Optical: systems and elements – Compound lens system – Microscope
Patent
1995-05-26
1997-08-19
Dzierzynski, Paul M.
Optical: systems and elements
Compound lens system
Microscope
359369, 359371, 359370, 359378, 359385, 359386, 359 30, 359 19, 359 20, 356346, 356347, G02B 2100, G02B 2136, G02B 2122, G03H 100
Patent
active
056594208
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a three-dimensional shape measuring apparatus in which a confocal optical system is employed, and in particular relates to a confocal optical apparatus for performing three-dimensional measurements using a hologram or a diffraction grating-type half-mirror.
BACKGROUND ART
So-called confocal optical systems are apparatus for measuring distances. FIG. 22 illustrates the principle of a confocal optical system.
In FIG. 22, light from a light source 1 is condensed by a lens 12 and then directed toward a half-mirror 31 via a pinhole PH1 located at a focal point F1. The light from the light source 1 is transformed by the pinhole PH1 located at the focal point F1 into light equivalent to the a point source. Light reflected from the half-mirror 31 is condensed by a lens 8 and projected onto the surface of an object 9. Shown here is a case in which the surface of the object 9 is in the focal position F2 of the lens 8, and the object 9 is moved and scanned in the X-Y-Z direction by a three-dimensional moving stage 40. Light scattered on the surface of the object 9 passes through the lens 8, travels through the half-mirror 31, and converges toward a point F3 conjugate with the focal position of the light source 1. A pinhole PH2 is located in the position of this focal point F3, and transmitted light is detected by a light sensor 10.
With this structure, the focal point F3 on the conjugate point side moves when the object surface Z0 is shifted to the front or back (Z1 or Z2) of the focal position F2, as shown in FIGS. 23a and 23b, and the output of the light sensor 10 is markedly reduced by the action of the pinhole. FIG. 24 illustrates the relation between the position of the object surface and the output of the light sensor 10.
This structure makes it possible to shift the measurement object 9 by the three-dimensional moving stage 40 in the direction of the Z axis (in the direction of the optical axis) for each X-Y coordinate position, to sample the output of the light sensor 10 in the course of this displacement, and to designate the detected Z position corresponding to the maximum sampling output as the surface position of the object 9. It is therefore possible to subject the measurement object 9 to three-dimensional measurements by sequentially changing the X-Y coordinate position and performing the same measurements.
A disadvantage of this conventional apparatus, however, is that each measurement instant yields information about a single point in space, making it necessary to spend much time to detect the surface shape.
In view of this, an attempt was made in Japanese Laid-Open Patent Application 4-265918 to arrange the confocal optical system in two dimensions and to detect each object position in parallel; the corresponding structure is illustrated in FIG. 25.
Specifically, with the apparatus illustrated in FIG. 25 above, light from a light source i passes through lenses 12 and 2, becomes parallel light, and enters a pinhole array PHA1. The pinhole array PHA1 consists of pinholes arranged in a matrix. The light that has passed through the pinhole array PHA1 is transmitted through a half-mirror condensed by lenses 8a and 8b, and projected onto a measurement object 9. The measurement object 9 is placed on top of a moving stage 35 capable of displacement in the direction of the Z axis. The light reflected by the measurement object 9 is condensed by the lenses 8a and 8b, reflected by the half-mirror 31, and imaged at a position conjugate with the pinhole array PHA1. A pinhole array PHA2 is located in the imaging position, and the light passing through the pinholes is detected by the individual light sensors 10 of a light sensor array.
This conventional structure makes it possible to separately sample the outputs of the individual light Sensors 10 of the light sensor array while displacing the moving stage 35 in the direction of the Z axis, and to designate the detected Z-direction position corresponding to the maximum output of the individual light sensors as the surfac
REFERENCES:
patent: 3013467 (1961-12-01), Minsky
patent: 3899711 (1975-08-01), Lemmond
patent: 5144540 (1992-09-01), Hayes
patent: 5329178 (1994-07-01), Derndinger et al.
Ando Manabu
Mizoguchi Kiyokazu
Moriya Masato
Shio Koji
Suzuki Toru
Dzierzynski Paul M.
Kabushiki Kaisha Komatsu Seisakusho
Sikd-er Mohammad Y.
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