Table of contents

A light pulse measuring device (time-expansion type phototube) which makes use of a velocity-modulation technique is proposed. The device provides the pulse expansion in time scale amounting to several hundred times. It is capable of direct observation of the shapes of the ultra-short pulses with an ordinary observing technique, for example, a sampling oscilloscope. The time resolution is evaluated to be a few picoseconds. Expected sensitivity ranks next to that of a photomultiplier when used with electron multiplier. The basic theory of the operation and characteristics of typical examples are presented in this paper.

An analysis of the enhancement of lattice vibrations by powerful picosecond light pulses leads to an increase of electric permittivity for optical frequency due to dipole-dipole interaction, both dipoles being induced by electric field of the light wave. It is shown that only the anharmonicity of lattice vibration guarantees the occuring of light filament formation.

This paper describes the most suitable design of the photon-drag detector and its figure of merit, and a new linear technique using the photon-drag effect for the measurement of ultrashort infra-red light pulses is proposed.

Conventional description of light sources in terms of power and coherence is deprived of all meaning as their statistical properties are not stationary. For instance, this case appears in light distribution in which illumination gradients are important (e.g. speckle), or pulses emitted by a mode-locked laser, the modes being partially or completely synchronized. Some methods of measurement of statistical data specify such partial coherent sources optically. Experiments show that the shape of 3rd-order time correlation obtained in nonlinear optical media leads to new quantitative information on the structure of short impulse sequence evolving some time coherence. Likewise, some classes of spatial distribution of luminance are analysed by utilizing concepts derived from experiments of holography in spatially incoherent light.

This paper reviews briefly the photoelectric methods for measuring very weak light signals based on the analog and digital techniques. Comparative study performed experimentally and theoretically shows that the single photoelectron counting method is advantageous with regard to sensitivity and stability. As a further extension of this study, the method for measuring the spectral distribution of ultra-low light signals was studied which led to the design and construction of a new type of spectrometer, called the filter spectral analyzer. Experimental tests to examine its performance and comparisons of its sensitivity with a conventional grating spectrometer were made by accomplishing the spectral analysis of low-level light sources. Moreover, as far as we know, the first spectroscopic measurements of the ultra-weak chemiluminescence associated with some sorts of enzymatic reactions were performed successfully as the new application of the measuring methods developed and evaluated in this paper.

This paper reports analytical and experimental studies on the lifetime measurements using correlated photons in cascade. Two photons emitted spontaneously in the cascade of a three level system are detected separately by two photomultipliers (PM), and from the time correlation between output photoelectron pulses of the two PM's, the direct measurement of the lifetime of the intermediate state in the cascade transition has been performed. The optimum operational condition of this method is discussed quantitatively by analyzing the signal-to-noise ratio and the contrast factor which is defined as a ratio of signal to background. Based on the analysis, measurements were made on 6³P₁ level in Hg r, and 2p₈ and 2p₉ levels in Ne i. The measured results are presented in comparison with corresponding results of other authors based on different techniques.

A novel high speed spectrophotometric system for the measurement of the weak transient radiation which can be repeatedly provided has been constructed. The principle of operation is based on the nanosecond measurement of the time distribution of the emitted photon burst during the short period of transient radiation. The system is characterized by the unique operation of multichannel coincidence circuit which works in conjunction with a high speed timing discriminator. An on-line mini-computer also plays an important role in accomplishing the data acquisition and analysis. Typical fluorescence decay curves are presented to demonstrate the system performance.

A photoelectron counting system has been constructed for the statistical studies of fluctuating light intensities of a limited duration, where a maximal exploitation of the data on time intervals between neighbouring pulses and their sequence in a photoelectron pulse train is required in order to maximize the statistical accuracy of a desired information on the light. The idea that has been adopted here is to collect the data in the computer memory and to use them repeatedly until a complete information is extracted. With this system, approximately 8000 data on pulse intervals ranging from 800 nsec to 2.1 sec can be processed at a time. The performance is demonstrated for He–Ne laser light itself and He–Ne laser light scattered from a suspension of polystylene spheres in water.

A newly constructed spectrofluorometer system which is characterized by photon counting mode of detection and computer assisted operation is presented. The photon counting technique is utilized to detect a weak fluorescence emission, and the gate width of the counter is continually controlled by the monitor photomultiplier output to cancel out light source fluctuations. Correction of the spectra is carried out in real time by using correction factors derived from the results of absolute intensity measurement by means of a quantum counter. All the experimental procedures can be done in the conversational mode through a teletypewriter and the corrected and uncorrected spectra are presented on the X–Y recorder on a wavelength scale. Details of the system are described together with examples of its performance data.

Sensitive bolometers are constructed with strips of thin films of Ge (or Ge containing a small amount of Au). These strips are obtained by evaporating Ge in high vacuum on a plate of fused quartz and then dipping this plate in distilled water to remove the deposited Ge film. The area of the element varies from 0.5 mm² to 10 mm², and the electrical resistance from 100 KΩ to 10 MΩ at room temperature. The current noise can be completely eliminated by carefully welding the strip to the electrodes by means of an electrical discharge. The detectivity of the best bolometer so far obtained is about 2×10⁸ cm·Hz^1/2/W.

A charcoal pumped seal-off type He³ refrigerator is applied to an n-type InSb far-infrared detector. The detector temperature of 0.37 K is easily obtained under working conditions. This combination provides a higher sensitivity by a simple cryogenic handling than a conventional liquid He⁴ cooled detector. Incident power consideration is important to keep a detector at He³ temperatures. The acceptable highest wave number is about 60 cm^-1 using a Michelson type interferometer and 140 cm^-1 using a dispersive monochromator.

Since the advent of the laser and saturated absorption locking of the laser, the extension of radio frequency technology in to the optical region has produced exciting new results, such as a 10000 fold increase in the resolution of spectroscopy in this region and a new value of the speed of light, 100 times more accurate than the previously accepted value. This talk will describe the techniques and results achieved.

In the continuous drive method of Fourier spectrometer, the movable mirror should be driven at a constant speed. Otherwise the speed fluctuation causes spurious spectrum as ghost in a conventional spectrometer because of the lack of the uniform sampling path difference due to the characteristics of the electric filter. This paper gives a sampling method for correcting the distorted spectrum by the use of electric filter characterized by a flat attenuation and linear phase shift for the main signal, and the delay circuit for the sampling signal. The method is discussed theoretically. Experimental results show that the method is effective to correct the distorted spectrum.

Reliable Fourier spectrometers have been extensively employed for the collection of high spectral resolution infrared emission and absorption spectra. These spectrometers are being used in difficult field situations. Weak and fluctuating sources have been measured by coherently adding many interferograms. The specifications of field-grade Fourier spectrometers are presented. The measurement techniques for obtaining quantitative infrared spectra from remote sources are described. Examples of high spectral resolution infrared measurements of smokestacks, sky emission, jet aircraft and missile exhausts are shown.

A new method of interference spectroscopy is described. The spectral element is detected photoelectrically by taking the interference between the reflected and the diffracted beams of a modified Michelson interferometer whose one mirror is replaced with a diffraction grating. From the output of the photomultiplier the spectrum is obtained directly without any computation. The spectrum is scanned by the rotation of the grating and the modulation of the spectral signal is carried out by the vibration of the reflecting mirror. The resolution of the instrument is about 30000. The spectra of He–Ne gas laser, sodium D lines, 5461 Å, 5770 Å and 5790 Å lines of mercury obtained by this instrument are presented as an illustration.

To improve the contrast of a single Fabry–Perot interferometer, a double Fabry–Perot interferometer was designed. The contrast of this system is ∼7×10₄ which is ∼30 times as large as that of a single Fabry-Perot interferometer. Using this system, the Brillouin spectrum of gadolinium molybdate crystal, which has a very strong central component, could be observed. The temperature dependence of Brillouin shifts and Brillouin linewidths was measured. Brillouin shifts show softening and Brillouin linewidths show anomalous broadening near the structural phase transition point.

Brillouin backscattering from laser-produced plasmas of hydrogen and deuterium has shown as isotope effect in the red-side part of the generated second-harmonic light. This isotope shift is explained by the parametric instability at the cutoff region using the phase-matching condition of the waves. The decrease of the reflectivity appeared when the laser instensity increased up to one order of magnitude larger than the threshold of the parametric decay instability. A self-phase modulation by the modulational instability at critical density was observed. A broad-band laser showed more effective heating of the plasma than a narrow-band laser.

The excitation of Raman spectrum in very thin films requires a large concentration of energy. For the two methods we have previously described we compare the exciting fluxes in different media, the scattered fluxes and the useful volumes in the samples.

The Lamb dip on the Cd ii 4416 Å line is measured using a low-noise He–Cd laser. Noise characteristics are investigated in detail. The noise in high frequency range is found to depend critically on He pressure and discharge current. Dependences of resonance widths on He pressure and discharge current are observed. The radiative line-width is (56±6) MHz. The pressure broadening is (8.7±2.9) MHz/Torr. The latter is about a factor of 5 smaller than that of the Ne 6328 Å line. This result is attributed to the difference in effective quantum numbers of the upper laser levels. The electron broadening is also found to be (0.36±0.08) MHz/mA.

Methods for determining several important parameters of partially homogeneously broadened gas lasers, such as the Lorentzian line width, Doppler line width, spontaneous emission line width, saturation intensity, and gain coefficients, have been developed for both continuous wave and pulsed operation. For CW gas lasers, values for the gain and line-shape parameters are obtained from an analysis of experimental measurements of the saturated gain at the line center vs input intensity, and of the spontaneous emission line width, based on a quadratic approximation to the saturated gain and a Voigt function description of Fabry–Perot interferograms. Line-shape parameters of a laser amplifier can also be determined by analyzing measurements of the pulse intensity gain, pulse duration time and pulse delay time, using numerically calculated functions of the ratio of Lorentzian to Doppler line width. Experimental measurements for both CW and pulsed operation of the xenon 3.5 µm laser transition are adduced and analyzed as an example.

A new method of emission measurements of optical transition probabilities between two States through stimulated emission phenomena is shown, and the transition probabilities of four lines of argon ion and of three lines of krypton ion are measured. Perturbation spectroscopy is mainly used in our observation and Lamb's rate equations are applied to calculations. At first the ratio of the population densities of the two states of transition is experimentally acquired, and then the transition probability is determined using this ratio of populations. Measured transition probabilities of argon ion are compared with published values and meet in good agreement with them. Measured values of krypton ion are compared with the data of spontaneous emission intensities, and supposed to be reasonable.

Silicon-photovoltaic cells are now in common use for light- and color-measurement. Their use is limited by the minimum "actinic" radiant flux, which can be measured according to the sensitivity of the detector, lowered by correction to the wanted evaluation function, and the quality of the amplifier. With best operational amplifiers an illuminance of 10^-3 lx and a luminance of 2 cd/m² (evaluation angle 1.5°) can be measured (smallest digit). By tristimulus colorimetry the chromaticity coordinates can be measured with 4 decades, if the sum of the tristimulus values are equivalent to that of 5 lx at illuminant A.

This paper describes an instrument for quantitative microspectrofluorimetry. It is capable of quantitative fluorescence measurements with better accuracy by introducing a spot excitation system and microspectrofluorimetric attachment as well as a stabilized light source. As only a small portion of the specimen is illuminated with the exciting spot light, it is possible to perform the measurement of fluorescent distribution across the entire area of the specimen without the influence of photodecomposition and nonspecific fluorescence. An accurate measurement of fluorescent spectrum scanned over the wavelength range between 400 and 700 nm can be done in 3 sec. Its construction and examples of biological application are presented.

A novel gas analyzer by UV absorption has been developed in order to measure the concentrations of sulphur dioxide, nitric oxide and nitrogen dioxide which are the major gaseous pollutants in the fossil fuel burner exhaust. Theoretical consideration of multiple ingredient measurement by light absorption, results of measurement of absorption cross sections of the three gases, discussion on the anomalous behavior of NO absorption and operating performance of the developed gas analyzer are described. The operating characteristics revealed this gas analyzer is useful for the monitoring of SO₂, NO, and NO₂ in the stack effluent.

The measurement of the absorption lines of ozone using the emission lines of the (00°1–02°0) band of CO₂ laser was discussed. As the result of experiment, it was made obvious that the absorption cross section of ozone pressurized up to 760 Torr was (2.4±0.08)×10^-19 cm² at the frequency of 1052.1956 cm^-1 corresponding to the P(14) laser line of the (00°1–02°0) band. By the use of this value, the minimum detectable concentration of ozone was estimated for the long path absorption. Accordingly, it was concluded that the concentration of 0.1 ppm in ambient atmosphere would be able to be detected by using the laser power of only 0.3 µW for the path length of 500 m.

Results described here show that infinite conductivity theory matches experimental grating efficiencies very closely when wavelengths exceed 4 µm, in fact often serves adequately above 1 µm. At shorter wavelengths, i.e. the visible region, the influence of finite conductivity on the theory must be included, in which case once again excellent agreement with experiment can be demonstrated. The nature of anomalies, especially as affected by different metal surfaces, is a highly sensitive test for theory. In the vacuum ultraviolet region correspondence between theory and experiment could still be observed, although some new practical limitations intervene.

Within the last several years the holographic grating has been developed both technically and theoretically, and it is now possible to discuss their properties by comparison with classically ruled gratings. Although the two kinds of gratings compete for many applications, each has properties the other lacks. This paper gives a comparative review of gratings in terms of ruled area and the number of grooves/mm, quality of diffracted wavefronts, ghosts and stray light, and efficiency. Problems associated with the grating efficiency are discussed in the three domains of the holographic grating, i.e., in the "very electromagnetic", "middle electromagnetic", and "scalar" diffraction domains.

Blaze optimization studies of diffraction gratings in the past have all assumed that the surface conductivity of the grating structure is infinite. This has previously restricted the validity of these results to the infra-red region of the spectrum. The theory of Maystre takes account of the finite conductivity of the grating surface and has enabled rigorous studies to be made in the visible spectrum. Results obtained using Maystre's theory have shown that the blaze optimums predicted using the infinite conductivity theory may be usefully extended to the visible spectrum. Results are reported here for gratings having triangular, sinusoidal and distorted sinusoidal groove profiles.

This paper is concerned with continuous control of the grating ruling process. It is shown that unless special measures are taken in the guidance of the indexed grating carriage, Coulomb friction will be more than two orders of magnitude greater than the inertial reaction force. A ruling engine is described in which piezo-microstep indexing is employed. Fast continuous control of the grating carriage has enabled acceptable test-ruling to be undertaken with only elementary environmental precautions taken. Analysis of control requirements reveals a constraint on the maximum groove density and control response speed in continuous motion machines. Currently recorded performances indicate that this may have already been approached.

Concave gratings that form stigmatic images in normal incidence spectrographs are analyzed and a new method of ruling stigmatic concave gratings has been developed. The ruling engine is numerically controlled for varying the groove spacings and is capable of ruling both straight and curved grooves. Three types of concave gratings, one conventional and two stigmatic have been ruled and the imaging properties of them are examined. From the results of the examination, the possibility of producing mechanically ruled stigmatic concave gratings with the freedom of choosing stigmatic wavelengths is proved.

Production of blazed plane holographic gratings with various groove spacing by a simple optical system as used in the Wiener's standing wave experiment is investigated. Gratings were made in Shipley AZ–1350 photoresist, and it was found that the blaze wavelength could be controlled between half and four fifth of the theoretical value of 305 nm by changing the exposur and development conditions. The groove had a good sawtooth contour up to 1500 lines/mm and the efficiency did not decrease. The wave front and the line profile were also measured and the results were as good as those of mechanically ruled gratings. The experimental results will provide valuable informations on the production of holographic gratings blazed for other spectral region.

The theory of the holographic grating is applied to the design of aberration-reduced holographic concave gratings for use with Seya–Namioka monochromators. The proper recording parameters are determined for various types of aberration-reduced holographic concave gratings that have the effective grating constant of 1/1200 mm. The performance of the holographic gratings thus designed is evaluated in terms of the degree of spread in spot diagrams. The results show that coma-reduced holographic concave gratings are superior to conventionally ruled concave gratings and holographic concave gratings of Types I, II, and III, proving the usefulness of the design procedure adopted in the present study.

The exact solutions on the directions of diffracted rays and the positions of image points on an image forming surface have been derived in the case of the diffraction of lights from a point source by a grating. No limitations are needed for the shapes of surface and lines of the grating.

The concept that the ruled area of a concave grating must be symmetric with respect to its vertex is generally accepted and applied in all mountings manufactured at present. A new concept is introduced in the theory: the center of the rectangular area used is not necessarily the vertex of the grating, but a point of the symmetry plane perpendicular to the grooves, lying at a varying distance w_o from it; the additional degree of freedom thus introduced permits an improvement of focus of some mountings commonly used at present. Fixed slits monochromators with translation and rotation of the grating and with simple rotation of the grating are examined.

Optical transfer functions (O.T.F.'s) of a simple plane-grating monochromator were determined by both of experimental and theoretical methods in case of partially coherent image formation. Because of low degree of coherence, the light intensity was regarded to be additive as in the case of incoherent image formation. In an observed spectrogram of Hg 6P–6D lines, the faint shoulder corresponding to the weak 578.97 nm line appeared clearly when it was corrected by means of the O.T.F.'s.

The theoretical and experimental foundations of holographic interferometry and holographic contouring are reviewed. Holography has revolutionized classical interferometric measurements. It visualizes optical path changes of the order of the wavelength of light, (i.e. 1/2 µm). It is a consequence of the wavefront (phase) re-creation properties of a hologram. A new technique of nondestructive testing has resulted. Flow visualization has been improved. It is practiced with visible lasers, usually He–Ne gas lasers or pulsed ruby lasers. The latter records holograms under non-laboratory conditions.

The developments of holography suggest several contouring applications. Nevertheless, most of the holographic contouring procedures were primarily centered on the visual imaging technique. We will discuss a modulation-detection technique, in which precision of a real holographic image can easily be achieved. The basic advantage of the modulation-detection technique, aside from very fine precision, offers automatic contouring procedures. The major application of this technique may range from delicate biological specimen contouring to historical art data preservation.

A holographic method for surface mapping is described, and the results obtained, with respect to accuracy and data retrieval rate, are compared to those obtained by stereophotograrnmetry. With the holographic technique, in which a real image of the surface is scanned automatically, greater accuracy is achieved and data are retrieved more rapidly. A high-power pulsed laser technique is also described which allows extending the method to non-stationary objects. Although developed primarily for automotive model mapping, the method is applicable to other areas such as anthropometry.

A holographic spatial filter for direction independent differentiation can be produced with a multiple exposure technique by superimposing four holographic gratings with slightly different grating constants. A theoretical description of the filter is given and the experimental realisation is explained. Finally some experimental results are presented.

Differentiation filters are considered from a new view-point. A moiré pattern is obtained by recording incoherently two interference fringes whose spatial frequencies are slightly different. This pattern serves as a first-order differentiation filter. The second-order differentiation filter is synthesized with triple exposure technique. The second-order differentiation is also performed by utilizing the nonlinear characteristics of the photographic emulsion on which the exposure corresponding to making the first-order differentiation filter is recorded. As applications of the first-order differentiation filter, the differentiation of a phase object and the subtraction of two letters are experimentally performed.

This paper describes techniques for processing data given in the form of line functions. The outputs from pen recorders and oscilloscopes, line drawings and graphs are examples of data available in this format. We have used a sphero-cylindrical optical processor in order to achieve the addition, subtraction, or differentiation of line functions. There are two basic techniques, one of which allows real-time addition or subtraction of two graphs if one of them is available beforehand. The latter method displays both the sum and the difference of the functions in the output plane of the optical processor. The theory of the method is developed and experimental results are given.

In addition to the absorbing structures in photographic layers, surface relief and index of refraction variations may occur that change the optical path length and hence the phase of a wave field passing through the layer. A method is reported on how the modulation of these phase structures can be determined from two measurements of the modulation transfer function, MTF. Assuming a photographic grating to be purely absorptive, an elevated "as-if-MTF" is obtained from diffraction efficiency measurements. By means of a new scanning instrument, the MSSM, the correct MTF can be measured. From these two MTF values, a simple formula yields the modulation of the associated phase grating. Experimental values for a holographic plate show a maximum phase modulation little less than 1 rad per unit density difference at a spatial frequency of about 35 cycles/mm and vanishing phase effect beyond about 600 cycles/mm.

In order to produce an accurate aspheric surface, it is necessary to know the exact shape of that surface in the process of polishing. For this purpose, we have developed an interferometer using computer generated holograms. Experiments were made on that apparatus with three kinds of computer generated holograms. They are 1) interferogram, 2) Lohmann type hologram and 3) inclined bar type hologram. A software has been developed to draw interferogram, but generally computer time to draw it was larger than that to obtain a Lohmann type hologram. The deterioration of the interference pattern when using a Lohmann type hologram could be remedied by using a proposed "inclined bar" type hologram to some extent. Therefore, the inclined bar type hologram is more practical for the purpose of testing an aspheric surface.

A holographic interferometer is described for the measurement of the vector displacement of a deforming rough surface. The illumination of the object surface is provided by four beams arranged in pairs in two orthogonal planes. Four sets of interference patterns, one from each beam combining with the reconstructed image of the surface, are viewed one at a time in a single direction. This viewing direction is parallel to the line of intersection of the two orthogonal planes and normal to the surface. The method yields two independent sets of measurements from which the consistency of the observations may be checked. The interferometer has been used to measure the surface displacement of a specimen of concrete, in real time, when the specimen is absorbing water.

Double exposure holography has been used in order to study the surface distortion of ceramic plates due to bullet impacts. A double-pulse ruby laser was first used: the reference exposure was taken before the gun shot; the second exposure occurred a few micro-seconds after the impact. In another experiment the pulses were delivered by two ruby lasers suitably adjusted: both exposures were taken after the impact with a time interval ranging from 10 to 0.4 µs in this case. Pictures and results are presented.

In holographic interferometry, interference fringes of equal inclination are produced from a double exposure hologram recorded before and after the movement of a diffuse object. These fringes, however, can also be obtained by the movement of a photographic plate on which the hologram is to be recorded and this movement is useful when the movement of the object is not possible. This paper discusses a method for detecting the degree of deformation from the decrease of the visibility of these fringes and for measuring the area of deformation by using the subtraction processing. An application to the electrochemical polishing is proposed.

A new method of holographic interferometry is proposed for obtaining the contours of the vibration amplitude and determining the phase of the vibration of an object. The basic idea is to make a double exposure hologram by the time average and the sinusoidal phase modulation methods. The brightest interference fringe on the reconstructed image corresponds to a nodal line and the second brightest fringe gives the information on the relative phases of vibration between various object points. The new method has been applied to a practical vibration study of the blade group of a steam turbine and its usefulness and simplicity have been verified.

By the use of a light source of two wavelengths and by the sinusoidal phase modulation of the reference wave in recording a hologram of a vibrating object, small amplitude vibrations which are hardly observable by the normal time average method can be detected as a slight color variation against the colored background of stationary regions on the reconstructed image. Theoretical analysis of the color variation on the image is given and an experiment has been performed by using a He–Ne laser and an Ar-ion laser as light sources. The color variation is easily detectable and the colored background of stationary regions allows the shape of the object to be clearly recognized. The difference in color variation also helps to determine the phase of the object vibration.

Interference fringes have recently been obtained with two small telescopes operated as a Michelson stellar interferometer. With the availability of photon-counting television cameras, it now becomes possible to build synthetic aperture arrays of large telescopes working in the speckle interferometry mode. Details of the two-telescope prototype are given, as well as preliminary plans for the construction of a full-size array.

Speckle patterns at the image plane of a diffusely reflecting object illuminated by completely or partially spatially coherent light are studied experimentally as functions of the spatial coherence condition of illumination and the surface roughness properties of the object. Measurements of surface roughness from the average contrast of image speckle intensity variations are discussed in some detail. The usefulness of the present method using image speckle patterns is verified experimentally.

The dynamic behaviours of laser speckles caused by a uniform in-plane movement of a diffuse object are investigated by deriving the general formulas of the intensity cross-correlation function in both the diffraction and image fields of the object. The formulas obtained suggest the new methods of pattern correlation and MTF measurement. Validity and applicability of these methods are verified experimentally.

A new method for non-contact velocimeter is proposed. A one-dimensional photodiode array, whose diodes are connected differentially, is used instead of a parallel slit array, in order to remove the low frequency noise. Then, the output signal of the differential detector is restricted to a narrow band signal, whose center frequency is proportional to the velocity of a rough surface. Since the output can be directly fed to a frequency counter, the restriction of the measurement range due to the cut-off frequency of the high pass filter is lifted. The characteristics of the proposed velocimeter are studied with the aid of spectrum analysis and some experimental results are shown.

The autocorrelation function of a diffusing and/or transmitting pupil as well as the visualization of its displacements and eventual deformations are given by a suitable Fourier transform of the speckle pattern representing the diffused and/or transmitted wavefront. This technique has been applied to the determination of the Modulation Transfer Function of real pupils and quantitative study of vibrations of a metallic plate. In this work we use the statistical properties of a random distribution of transparency transmitted by an optical system to measure its Modulation Transfer Function and the properties of a wave diffused by a rough oscillating surface to determine its vibration amplitude, and then the deformations of the fringe pattern projected on the vibrating structure to obtain the large amplitudes of the mechanical vibration.

Effect of speckle reduction on the spatial frequency contents of the object is investigated for partially coherent optical systems specified with the circular and ring effective sources. For this purpose, using the general formula derived previously, the spatial frequency distributions of the noise power of speckling are given and the general formula to obtain the image contrast of the sinusoidal object in any illumination mode, is derived. Computer simulations are made to obtain images of simple object models in the presence of the random phase noise under the stated coherence conditions. The correspondence between the statistical evaluation of the speckle noise and the appearance of the image is examined in coherent and partially coherent optical systems. Then, some experimental results for the practical optical systems are compared with corresponding, simulated images.

A laser Doppler microscope having a spatial resolution of about 5 µm has been constructed which has an ability of measuring the flow velocity in a microscopic area. The two kinds of Doppler-signal analyzing systems in this microscope are investigated and constructed. An example of the experimentally measured results by the laser Doppler microscope is shown.

A method for measuring low velocities is described. A directional laser Doppler velocimeter is employed so that the generated carrier beat signal may be modulated by Doppler shifts due to a moving body. The Doppler shift in question is recovered by phase demodulation techniques that are capable of excluding the unwanted low frequency fluctuations due to instruments. This processing is simply done by comparing the modulated beat signal with the reference carrier beat-signal at the phase demodulating stage. The velocity as low as 0.07 µm/s is measured using a solid test specimen moving in a sawtooth or triangular mode.

A new method of in-plane vibration measurement is possible by using an optical heterodyne technique which detects the frequency shift of light reflected from a point in motion. If a point in a vibrating surface is illuminated with two laser beams whose light frequencies are slightly shifted from each other in the direction symmetrical with respect to the normal of the surface and the intensity at the point is measured with a photomultiplier through an optical system, the output signal of a limiter-discriminator connected to the terminal of the photomultiplier has an amplitude proportional to the frequency-amplitude product of in-plane vibration. By using these principles, a prototype instrument for the measurement of in-plane vibration is constructed and a vibration amplitude of 10 Å at 20 kHz is measured in real time together with its direction.

The phenomenon of interference in diffused light was observed for the first time by Newton. But it is after the discovery of laser and holography that the problem of interference in diffused light gained attention of many workers all over in the world. In the experiment of Burch and Tokarski a number of speckle pattern, displaced laterally relative to one another and recorded successively on the same photographic plate, gives at infinity a system of interferences fringes. We describe a new method of optical processing which is based on the speckle interference phenomenon at infinity. After describing the general principle of the method, we shall give a brief account of the various applications of this technique: extraction of differences between two images, multiplexing of images, the coding and decoding of a message, spatial filtering, data storage. We shall describe also the applications of double-exposure speckle photographs to study displacement and deformation of an object and at the end we shall discuss how speckle intervenes in astronomy.

The point-diffraction interferometer is an interferometer for measuring phase variations in which the reference wave is produced by a point discontinuity in the path of the beam. Its simplicity makes it very suitable for testing instruments in situ, and some such tests are described. The general theory shows that other diffracting apertures can be used and relates the technique to phase-contrast microscopy and to scatter-plate interferometry.

Assuming that any path difference or time retardation between interfering waves of polychromatic light produces a spectral modulation, a wide variety of absolute measurements can be carried out through the classical channelled spectrum phenomena. This accounts for the properties of complex pupils and interference arrangements that behave as time optical filters–a spectroscope performing the analysis of the emerging disturbances. Practical applications are presented, including thickness measurement, interferometry with rough surfaces, non-holographic double exposure techniques for displacement evaluation, moiré effect between channelled spectra. Potentialities of the concept of time spread function are also illustrated in testing the departure from straightness and parallelism of slit edges, longitudinal analysis of pairs of wave trains still dealing with channelled spectra.

A second order finite difference can be obtained using birefringent optical components and only two polarizers. Different experimental arrangements will be proposed performing a second finite differentiation taken either in one direction or in two orthogonal directions. These new devices can be compensated for an extended source i.e. can work with nearly incoherent illumination.

An interferometer for the measurement of thickness of a lens by the aid of white-light fringes to an accuracy of 1 µm was designed. The two end mirrors of the dispersion compensated Michelson interferometer were replaced by a lens L to be tested and a reference plane parallel plate R of the same kind of glass and of the same thickness. The interferometer was adjusted to give rise to the white-light Newton rings over the front surfaces of L and R, and then either of L or R was made to move until another white-light fringes appear at the rear surfaces. The translation relates directly to the thickness difference between L and R. Experimental results confirmed that the method is capable of being applied to the thickness measurement of precision single lenses.

The evolution of computer disc files to the current levels of high density information storage has resulted in the development of high sensitivity, low-flying recording heads. An interferometer is described which was designed especially for the analysis of the flight characteristics of such heads. It is capable of detecting nano-metres differential motion between a head and disc in the presence of several tens of micro-metres of disc run-out. To achieve this mode of operation, differential design and polarisation effects have been employed. The final instrument has, in addition to fulfilling its design requirement, proved to be a versatile high precision measurement tool.

Discussion is made of calculational reconstruction of refractive index distribution from "multidirectional interferograms." Two approximate calculation formulae are given for two-dimensional case. One is derived using the Born approximation and corresponds to a generalization of the formula in X-ray structure analysis. The other is obtained using Rytov's approximation and a generalization of straight path approximation.

Multiple-path interferometers have been developed which are very stable and more sensitive than existing two-beam interferometers. Their optical properties are described in connection with alignment, stability and sensitivity. In the interferometers, the division and recombination of a light beam are repeated by means of the beam folder which is placed outside of a beam-splitter and consists of at least one Porro prism. A fourfold- and an eightfold-path interferometers are found to be more stable than a double-path interferometer. They are expected to have a sensitivity higher than 1 Å. Applications to the measurements of the fluctuation of air, the refractive indices of gases, the lattice constants of single crystals and the lengths of mechanical parts are briefly described.

We describe an "optical calliper square" which measures external object dimensions up to several tens of meters with a relative precision of 10^-5. This utilises an interferometer for displacement measurements and a single mode laser beam as calliper arm. The influence of geometrical parameters on the measurement are discussed. The experimental realisation and results obtained are given.

Using a laser beam focused near interferometer plates, an improved interferometric dilatometer has been developed. It has a couple of features, i.e. it has a much greater latitude in parallelism adjustment of the interferometer plates than that of the conventional Fizeau-type ones and enables, on the other hand, automatic recording with a simple device just composed of a solar cell and a recorder to measure reflected beams. Moreover, collimation of the optical system is very easy. Therefore, it is applicable even to routine determination of dilatation for quality control in a factory. The dilatometer is capable of determining the thermal dilatation of materials with low and/or negative expansion as well as those with transition, extremum or inflection point in expansion curves. Experimental results on some metallic, ceramic, semiconductor and glassy materials are presented.

An extension of the proposal presented by Gamo on the intensity interferometer with coherent background is introduced with similar abilities without using a triple correlating system and a modulated coherent light that were needed in the Gamo's proposed interferometer.

A computer-aided method of calculation for obtaining n and d directly from the observed values of tan Ψ and Δ is described. Two equations giving tan Ψcos Δ and tan Ψsin Δ as respective functions of Fresnel coefficients and δ are solved for δ and n. Here δ=4πd√n²-sin ²φ/λ (φ is the angle of incidence). As a means for solution a linear equation for cos δ is conveniently utilized, which is derived from the first of the above equations, and another equation giving tan ²Ψ as a function of Fresnel coefficients and δ. A similar method of calculation is also given for the case where n and d are to be determined from the principal angle of incidence, φ_P, and the ellipticity of light reflected at this angle of incidence, ρ_P.

Reflection of light at the surfaces of a λ/4 plate seriously affects the accuracy of ellipsometric measurements. The ellipsometer described here, which is to be used for the determination of the principal angle of incidence, φ_P, and the reflectivity ratio of the p- and s-components at this angle of incidence, φ_P, employs only one polarizer and no compensator, and is free from this nuisance. Its extinction sensitivity is roughly twice as large as that of a conventional ellipsometer. The requirements that have to be fulfilled in order that φ_P and ρ_P can be determined to ±3'' and ±10'' respectively are given in detail.

Optical excitation of non-radiative surface plasma waves at the interface between a metal and another medium is used for determining certain parameters of the metal or the adjoining substance. Relative variations of observable parameters with variations of the refractive index of silver are compared with ellipsometric data from the literature. Cover layer thickness changes can be observed and variations in the refractive index of the adjacent medium can be discriminated against by recording the position together with the shape of the reflection curve. A measurement technique for the observation of rapid layer growth is reported.

It is proposed that the pitch of the spiral structure and the refractive indices of cholesteric liquid crystals can be determined separately by using selective reflections and total reflections. This method is effective when the pitch is comparable with or shorter than the wavelength of visible light. In such a case, the "Cano wedge" method is difficult. Using the values of the pitch and refractive indices obtained by this method, the incident angle dependence of light transmission was calculated and compared with experimental results in order to examine the effectiveness of this method.

A well rectified polarizing microscope is constructed and applied to examine the edge birefringence. An interpretation is proposed to clarify the origin of the edge birefringence by using the theory of birefringence introduced by Bragg.

An angular-scanning polar nephelometer, used in this work for determining the size parameters of spherical aerosol particles generated by a piezoceramic nebulizer is described. The instrument uses a piezo-optical birefringence modulator to modulate the polarization state of the incident light beam and uses lock-in amplifier detection of the scattered light to determine the elements of the transformation matrix. Comparison of the results of the Mie scattering calculation with experimental data yields the size parameters of the aerosol. Pertinent factors effecting the mean size of the aerosol are described. The system has potential applications in atmospheric physics, as a calibration standard for particle size meters, and for evaluation of pollution measurement or control devices.

The theory and the process of the development of a new method of three dimensional measurement by the use of moiré or the moiré topography are described. The moiré formed by a linear plane grating and its shadow cast obliquely on the surface of an object shows the equal height contour of the object from the plane of the grating when the vertical distances of light source and the pupil of the observing system are equal from the grating. The noises in the picture such as the grating and its shadow and the alias moire due to higher harmonics of them will be wiped away by translating the grating in its plane during exposure. This technique also averages the pitch errors in the grating and improves the accuracy of measurement.

Moiré fringe patterns can be formed not only in the conventional way, by superposition of two gratings, but also by superposition of several gratings. The advantage is that the moire fringe spacing and orientation can be independently adjusted. Experiments illustrating this are shown and the zone-plate features of superposed quasiperiodic structures are demonstrated. The microstructure of the multiple grating moiré patterns has favorable properties in applications with visual inspection.

The moiré fringe with enhanced sensitivity, as much as ten times of conventional method, can be obtained by a newly developed strain measuring system based on multiplied fringe shift moiré technique. The system is useful for in situ strain measurement and features the stability against vibration and air-turbulence. Two-dimensional strain distribution can be determined at a time. Metal itself can be used as a test specimen and the measurement is carried out without contacting the test specimen. The system has been applied to the assessment of elastic and elastic-plastic strain and deformation around crack tip. The experimental results and the comparison with the theoretical prediction have verified the usefulness of the newly developed method.

A small-angle measuring device utilizing moiré fringe has been constructed for the absolute measurement of angular displacements smaller than 0.1 µrad. Applying an optical filtering technique, the intensity of the moiré fringe changes sinusoidally as a measuring mirror rotates; the apparatus is self-calibrated with an accuracy of 1%. A light emitting diode is used as the light source in order to reduce heat generation in the apparatus. The electrical noise in the output of the apparatus is about 10 µV which corresponds to an angular displacement of 60 prad. The short-term stability is about 0.6 nrad when the temperature changes are within 0.01°C, and the drift is 3 nrad/h. The measuring range is 4.5 µrad with an accuray of 1%.

An application of the moiré method to the interferometric testing of the plane gratings is presented. By this method, we can measure the slowly changing aperiodic spacing error separately from the other errors, that is, the error in the figure of the grating surface and the optical thickness variation. The principle is presented theoretically and verified experimentally.

Two methods for measuring the three strain components in a plane plate specimen are presented. In one method, the three strain components are converted into light intensity distributions, and in the other these components are converted into color bands in an image formed from the specimen. Optical spatial filtering using a cross grating is adopted for the measurements. The principles and some experimental results are shown in the present paper.

It was pointed out by Burch that blurring due to diffraction in moiré type displacement measurement can be minimized by using the Fourier image effect of transmission amplitude gratings. Similar effects can be obtained also by using phase gratings instead of amplitude gratings. The Fourier image and the double diffraction of holographic phase gratings of small grating constants (0.75∼10.0 µm) are investigated. Theoretical considerations on the contrast of double diffraction are also presented.

This paper introduces new techniques for automating the inspection of microcircuit mask patterns. The techniques are non-comparative, thereby eliminating the need for a reference pattern, and demonstrate an advantageous combination of simple optics and electronics to produce a system with excellent defect-sensitivity and speed. A single focussed laser spot is scanned over the mask. The resulting diffraction patterns are immobilized in the Fourier plane, where they are analyzed by a special photodetector array. Optimum designs for this array follow from a discussion, in terms of the Boundary Diffraction Wave theory, of the diffraction pattern differences between typical defects and valid mask features. The design and performance of a practical mask inspection system based on these principles is presented.

A new inspection system termed the "Projection Method" is developed and discussed from experimental and theoretical aspects. The essential of the method is the observation of Fresnel diffraction patterns of ceramic surface flaws such as pits, burrs and scratches. The observation yields the following information concerning flaws: 1) the flaw mode (namely, whether the flaw is convex or concave) and 2) the flaw size. This "Projection Method" can be applied as an aid to visual inspection not only for glazed and unglazed ceramics, but also for other materials such as glass and metal.

Measurement precision is in general determined by the instrument performance, the environmental conditions, and last but not least by economical considerations (measuring time, workload etc.). The influence of all three parameters which as of today limits the overall precision of industrial measurements can be drastically reduced by the aid of computers. Their data handling capabilities in terms of speed, capacity, and numerical data analysis allow to either increase the number of measurements and/or to evaluate the measurement data more thoroughly. In both cases the measurement precision will be increased beyond the instrument capabilities in conventional terms. The constraints of the environmental and the economical conditions can be overcome by increasing the speed of the measurement. Examples will be given for opto-electronic measurement principles applied to measurement tasks in integrated circuit manufacturing.

In order to measure the intensity distribution of an object far in the distance, a strip telescope with a long, narrow aperture is studied. The restoration of the highly resolved image from the blurred ones observed with the strip telescope is theoretically investigated for a general object. Some computer simulations are conducted to verify the theory. A diffractometor with a rotatable slit aperture is used in the experiment as a model of the strip telescope. The intensity distributions of the synthesized images are two-dimensionally displayed with a precise flying spot scanner. The utility of the strip telescope is also discussed.

This paper describes a Porro prism image derotator system. The prism is made to rotate at half the speed of a rotating component and thus renders to an observer's eye an optically stationary image of that component. A simple electronic synchronisation system has been developed to maintain a constant velocity ratio between the prism and the component to retain a stationary image. The prism unit has been used to study the centrifugal stresses of thin flat rotating photoelastic discs. The moire technique has also been applied to determine the corresponding disc displacements.

A new method is presented allowing study in real time of the intensity pattern of diffusing sources. The classical method of point by point plotting of scattered light intensity is replaced by the measurements of some coefficients, called "moments", directly containing all the desired information. This method uses an integrating sphere with a non-uniform coating. The principle of the method is explained, and then some experimental results proving its feasibility are presented. Finally we describe further improvements allowing actual application to the determination of the size and the shape of macro-molecules in a liquid solution.

The effects of the most usual corrections of transverse chromatic aberration, primary coma and astigmatism on the illuminance and chromaticity variations in the polychromatic edge spread function are obtained and discussed in this paper. Correction criteria of transverse chromatic aberration, which is the most important aberration with respect to the chromaticity variation in the image, are deduced as function of the illuminance and the chromaticity in the edge spread function.