A manager with a major automobile manufacturer once made the comment that " the best thing we ever did to improve quality was give the guys on the floor a caliper to measure the parts" . As the tolerances on manufacturing become tighter the need for accurate measurement has also increased. Hand fitting of parts to each other does not work in modem automated factories. Gages in the past have been built to provide a fixed set of measurements of a known part. This practice too has been changing due to the trend toward flexible manufacturing. Now the gages themselves must be flexible to accommodate the variety of parts made on a single line. This need has spurred a flurry of activity in the development of new three-dimensional (3-D) measurement tools. This paper will review the current state of the new optical based 3-D tools and discuss some of the applications being addressed. Background The need for three dimensional contouring has arisen from two primary areas of application. The first area of application has been in the area of robot guidance. ''4 Robots are used for their flexibility of motion. Applications may include loading of parts into machine tools stuffing printed circuit boards welding and cutting metal or simple assembly operations. In the simple applications the motion of the robot can be preprogrammed to follow a set trajectory. If the part not in the right location then the operation fails. In the case of painting robots this preprogrammed route can generally taken. As the task gets more complex and the positions become more critical guidance of the robot becomes important. If a robot welder misses the seam it may not only not make the weld but may also damage the surrounding material. This area of robot guidance has been one of the primary areas of growing interest. 58 The requirements for this type of application do not demand a great deal of contour measurement but does require three dimensional information. The range to the seam being welded as well as the location of the seam are very important. The actual shape of the seam is of secondary importance. This leads us to our second primary application area that being actual gaging of shapes for geometric verification. A complex shape like a turbine blade airfoil for example needs to be consistent and know to typically a few tens of microns. Large shapes and panels such as clay molds for car bodies have loser tolerances but are equally difficult a task because of the large areas involved. On the other end of the extreme in some cases the shape of the surface roughness of a material itself must be known typically to a fraction of a micron. The technologies for these applications need not

A moire profilometry method has been developed that is capable of inspecting objects whose size is limited only by the available laser power. The moire contours are generated in real time by projecting variable spacing gratings upon the target and filtering the image either optically in the video signal or in the computer. The system is designed to compare the surface shape of a test object with a previously stored image of a perfect object and to display the surface errors superimposed on a video image of the test object. A unique feature of the system is the continuously variable depth resolution which makes it usable either for human or robot adjustment of the test object or for automated pass/fail inspection.

Weak optical feedback from diffusely-reflecting targets modulates the power and emission spectrum of laser diodes. The modulation is a coherent phenomenon independent of background light and requiring very little power. The practical applications of the backscatter modulation of laser diodes is considered in the context of machine vision. It is shown that interferometry, velocimetry, absolute ranging, and position sensing can be performed with a minimum of hardware. Both high precision (submicron) and long range (50 m) systems are described.

A new type of moire reference grid on the surface of a CCD-chip is presented. In surface contouring an improvement of the resolution by a factor of 4 is achieved. The modification steps to generate the new reference grid are simple. Any further modification of the internal image size or the electronic design of the CCD-camera is not necessary.

The process of accommodating extreme measurement geometries, including aspheric cylindrical surfaces, is considered, and an absolute calibration technique for linear surfaces capable of 0.0067 wavelength (42 A) p-p with a precision (1-sigma) of 0.0008 wavelength 5 A is described. The technique was used to measure the absolute axial sag on the inside of a X-ray telescope.

Fluctuations of the refractive index of air causes nowadays the largest errors in high precise interferometric displacement measuring systems. We present in this paper a new method for compensating these influences by tuning the optical frequency of the laser. Variing laser temperature and current regulates the frequency (wavelength) of a GaA1As-semiconductor laser in such a manner that the wavelength in air is constant.

Rare-earth doped phosphors are discussed here which exhibit intense fluorescence well above 1000C. This is a rare characteristic for solidstate materials. One immediate application for them is thermometry. For example surface temperatures of rotating components systems in hostile or restricted environments and systems in environments with very high temperature backgrounds are measurable with phosphor thermographic methods. The subject phosphors Y203:Eu LuPO4:Eu YPO4:Eu and LuPO4:Dy provide the capability to extend these methods to very high temperatures. The use of pulsed ultraviolet (UV) laser activation of these phosphors leads to numerous practical application possibilities. The phosphor characteristics plus various fluorescent decay times vs temperature are shown along with discussion of their high-temperature applications. The phosphor thermographic method Several papers in previous ICALEO meetings have described various aspects of the phosphor thermographic method. 13 Since 1982 the method has been used to perform temperature measurements under a variety of conditions. The major elements of the technology include the pulsed activation of a surface layer of phosphor usually by a UV laser and the recording of the characteristic decay of selected fluorescent emission bands. For applications above 1000C the methodology remains basically the same. The added difficulties arise from the need to find and calibrate phosphors that are temperature active in this range and the need to reject any effects from blackbody emissions or other background effects specific to hightemperature environments. L. I. A. Vol.

A proposed multiplexed fiber-optic sensor system capable of analyzing a composite material during its curing cycle and over its service lifetime is presented. The sensor is composed of two independent sensing schemes that will ultimately be multiplexed onto a specialized singlemode/multimode optical fiber. The first sensing scheme is a fiber-optic viscosity and temperature sensor used for composite cure analyses. This sensor is based on (1) the laser-induced viscositydependent fluorescence phenomena observed in epoxy-based composite materials and (2) the temperature-dependent decay-time fluorescence phenomena observed in thermographic phosphors. The second sensor is based on a low-finesse, single-mode fiber-optic Fabry-Perot interferometer and is used as a strain/vibration sensor for lifetime nondestructive evaluations on composites. Exp erimental results have determined that these sensor concepts are feasible alternatives to cureanalysis monitors and conventional strain-analysis techniques.

The purpose of this paper is to provide a nonmathematical overview of holographic and speckle interferometry. This provides information necessary for those participants with little or no background in these areas to understand the application papers in the Holography Speckle session of ICALEO''89. Holography A hologram is an optical device which is capable of producing threedimensional images. The word hologram stems from the Greek root holos which means whole complete or entire and the word gram which means message. Thus a hologram is a complete record of a scene or object. The first hologram was produced by Dennis Gabor in 1948. In 1971 he won the Nobel Prize for his work. Leith and Upatnieks produced the first holograms using a laser in the early 1960''s. In conventional photography the light reflected from a scene is focused by a camera lens onto a photographic emulsion. The variation in irradiance of the light reaching the emulsion is related only to the amplitude of the electric field due to the light. To produce three-dimensional images a hologram records information about both the amplitude and phase of light reflected from a scene or object. Production Hologram Figure 1 is a sketch of a system which can be used to produce optical holograms. A laser operating in the TEM mode is used as a light source. A continuous wave or a pulsed laser can be

A system has been developed for display in real-time of dynamic and static holographic interference fringes and for quantitative data output. Although the optics are similar to a conventional electronic speckle pattern interferometer, a 90-deg phase shift is introduced between the reference and object beams after each TV frame. A pipeline image processor subtracts alternate frames and processes pairs of these results to obtain the square root of the sum of their squares. A true holographic image results whose speckles correspond only to image speckles on the original object. Dynamic displacements, such as vibration, are displayed in real-time Jo fringes. Static displacements are displayed as cosine fringes obtained by adding four current TV frames to four stored frames. Provision is made for speckle averaging by changing the object illumination. Image data fields can be transferred to the host computer for displacement analysis.

The use of pulsed laser holography in analyzing the atomization of impinging jets is evaluated using a holographic camera system capable of recording a 3D image of the atomization process in 3 x 10 exp -8 seconds. The holocamera and the experimental configuration and procedure are described in detail. Two nozzles were fabricated to produce 1-mm diameter liquid water jets that impinged at 60 and 90 deg. Holograms were obtained for each nozzle at liquid velocities of 20 and 40 m/s. Analysis of the holograms revealed the evolution of the jets from the plane of emergence through the region of droplet formation. Features of interest included the growth of disturbances prior to the breakup region and the effect of these disturbances on the formation of ligaments and liquid globules. Preliminary analyses show that waves of atomized liquid formed after impingement are closely correlated to waves measured on the jets, leading to the possibility of controlling the atomization process at the nozzle.

This paper presents the results of an analytical and experimental investigation of the accuracy of a laser Doppler velocimeter (LDV) for solid surface velocity measurements made over very short averaging times (less than a millisecond). Fundamental limitations exist on the accuracy of such ''instantaneous'' measurements. For frequency domain signal processing (spectrum analysis) the accuracy is limited by finite transit time broadening and, in the case of a rotating surface, tangential velocity gradient broadening. For time domain processing (time period measurement) the accuracy is limited by stochastic phase variations in the nominally sinusoidal signal. Experiments were conducted using both signal processing techniques to determine the conditions needed to minimize the error in instantaneous measurements using the LDV. An analysis of the relative performance of a laser speckle velocimeter is also included.

Lasers find application in numerous areas of criminalistics such as fiber analysis document examination and serology. Their widest use however is in detection of latent finger prints. Several routine procedures for obtaining laserexcited fingerprint fluorescence on a range of surfaces have been devel oped. However many surfaces fluoresce so strongly themselves that they are not amenable to these procedures. Timeresolved luminescence imaging is being investigated to permit detection of fingerprints on such surfaces.

Recent results are presented for the application of laser spark emission spectroscopy in the determination of elemental composition of particles in the combustion zone of a pulverized coal flame. The technique is particularly sensitive to metallic elements and may be very useful in the study of mineral matter transformations during combustion. High energy laser pulses were used to form plasmas on single coal particles and timeresolved spectra of the optical emission was collected using a linear diode array detector. The various transitions were assigned and qualitative trends in elemental composition for wellcharacterized coals were observed to be in agreement with other analytical results. Semiquantitative elemental concentrations were calculated and are presented.

A novel technique has been developed for measuring the temperature of the calcium oxide product inside an operating industrial lime kiln. In this technique trace quantifies of a rare earth element are incorporated into the product causing it to exhibit strong fluorescence under ultraviolet excitation. The decay time constant of this fluorescence which is strongly temperature dependent serves as a measure of product ternperature. The spectral and temporal characteristics of the fluorescence of several rare earths have been studied over a temperature range of 800 to 1150C which is the range of interest in an operating kiln. This workhasled totheselectionofpraseodyrnium asthernostsuitable rareearthelementand to the development of techniques to permit temperature measurements to be performed with an accuracy of approximately at rare earth concentrations in the parts per million range. A prototypesensoremployingthisfluorescencetechnique hasbeen used successfully to make measurements of lime temperature in an operating kiln. These measurements are in good agreement with simultaneous thermocouple measurementsoflimetemperatureand providethe firstaccurate in-situ measurementof lime kiln product temperature which can be made on a continuous basis.

A new micro object detecting sensor using diffracted light wave was developed. A linelike micro-object on the order of tenth micrometers in diameter can be detected over a large operating range of 0. 5mm wide 80mm long. The sensitivity of this sensor is not affected by the color material or diameter of the object. Futhermore the sensor is able to detect not only the existence of the object but also the lateral direction of the moving object when it gets out of the operating range.

A New capability and applTEtTof two-color laser three photon ionization process of CS molecule were presented. By using this method lying excited state 2Jir low lying state CS2were probed and investigated.