JP2011237272A - Optical distance meter and distance measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical distance meter and a distance measuring method with a confocal spectroscopic system, by which the position of a measurement object surface can be stably measured with high accuracy without being influenced by the reflectance thereof.SOLUTION: The optical distance meter 21 functions as follows. Illumination light from a white light source 22 is separated into an ordinary light component and an extraordinary light component by a birefringent plate 27 and projected to focus at different positions on the optical axis of the measurement object surface 34a. Reflected light from the object surface is multiplexed and dispersed with respect to wavelengths by a diffraction grating 29, and again separated into an ordinary light component and an extraordinary component by a birefringent plate 30 and guided into an imaging element 31. A signal processing unit 33 processes an electric signal outputted from the imaging element to detect intensities P1, P2 of the ordinary light component and the extraordinary light component, respectively, and calculates a difference ΔP=P1-P2. The position of the object surface is determined by detecting a wavelength λ0 where the difference ΔP reaches 0.

Description

  The present invention relates to an optical distance meter and a distance measuring method for measuring a distance to an object, a position, a shape, and the like optically in a non-contact manner.

  Conventionally, by irradiating light on the surface of an object and detecting the reflected light, the distance to the surface, its position, displacement, etc. are measured, and the two-dimensional and three-dimensional shapes of the object are further determined from the measurement results. Various optical methods are employed for measurement. Such optical methods mainly include confocal spectroscopy, focus detection, light wave interferometry, and triangulation.

  In general, a confocal spectral distance sensor includes a light source, a chromatic aberration optical system that directs light from the light source to the surface of the measurement object, and a photodetector that detects light reflected from the surface of the measurement object ( For example, see Patent Document 1). Since the light from the light source is focused at a different focal position for each spectral component by the chromatic aberration lens system, the reflected light from the surface of the measurement object is detected for each spectral component, and the distance from the light intensity to the surface of the measurement object is determined. Can be sought. Furthermore, in such a confocal spectroscopic method, light is scanned from a light source to a measurement object by an optical scanning means, and light having a wavelength whose focus is on the surface of the object is always detected, so that the wavelength peak position can be measured at high speed. A measuring instrument that enables this is known (for example, see Patent Document 2).

  In another confocal spectroscopic method, a light source that generates light of at least two types of wavelengths, a first photoelectric detector that detects the intensity of light from the light source, and light from the light source differ on the optical axis of the surface to be measured. There is known an optical displacement detection device including a chromatic aberration lens for focusing at a focal position, a second photoelectric detector for detecting the intensity of reflected light from a surface to be measured, and an arithmetic processing device (for example, Patent Documents). 3). This apparatus measures the displacement of the surface to be measured by calculating and comparing the light intensities detected from both photoelectric detectors for each wavelength.

  In addition, the position detection device of the focus detection method converges light from a point light source on the object to be measured, and the relative position between the apparatus side and the object to be measured so that the image of the point light source is focused on the object to be measured. The position where the focus is obtained is measured by a measuring means such as a scale, and the position and distance are detected. In order to simplify the system by eliminating the driving means for moving the apparatus side and the object to be measured and the measuring means for the movement amount, and to eliminate the influence of the accuracy of the driving means and the measuring means, the wavelength tunable laser light source Has been proposed (see, for example, Patent Document 4).

  In the light wave interference method, the light 2 from the light source is separated by a beam splitter, one of which is reflected from the measurement object and the base plate, and the other light reflected by the reference mirror is interfered with each other. The dimensions of the measurement object are measured from the fractional values of the two interference fringes (see, for example, Patent Document 5). In another light wave interference method, the light emitted from the light source and reflected by the object to be measured interferes with the light reflected by the reference mirror, and the interference light wave is recorded while changing the position of the reference mirror. It converts into a phase and measures the surface shape of a to-be-measured object (for example, refer patent document 6).

JP 2004-101532 A JP 2008-32668 A JP 51-51957 A Japanese Patent Laid-Open No. 2005-221451 JP-A-7-120210 JP 7-318308 A

  However, while the above-described light wave interference method can provide high accuracy, it is necessary that the light reflected from the object to be measured should have sufficient light intensity that is preferably equal to that of the reference light so that a clear interference fringe can be generated. It is. Therefore, there is a limitation that the surface of the object to be measured must have a sufficient mirror surface. In addition, the interference fringes are easily affected by air fluctuations and vibrations in the optical path, and it is difficult to obtain high stability.

  The focus detection method is advantageous in that it does not require the surface of the object to be measured to be a mirror surface and is not affected by air fluctuations or vibrations in the optical path. However, a mechanical drive means is necessary to obtain a focal point by relatively moving the object to be measured and the apparatus side in the optical axis direction. For this reason, the measurement range is set by the amount of movement by the driving means, and the resolution may greatly affect the measurement accuracy.

  On the other hand, the confocal spectroscopy method is advantageous in that it does not require a mechanical drive means unlike the focus detection method, and its measurement range is set by the amount of chromatic aberration of the optical system that enters the measurement object. It is. However, the conventional confocal spectroscopic measuring device has the following problems.

  FIG. 7 shows a typical example of a conventional confocal spectroscopic optical distance meter. In this optical distance meter 1, the light emitted from the white light source 2 is converted into parallel light by the collimator lens 3, reflected by the beam splitter 4, condensed by the condenser lens 5, and passes through the pinhole 6. The light exiting the pinhole is condensed by the chromatic aberration lens 7 so as to form an image at different positions S1 and S2 on the optical axis of the surface 8a to be measured for each of different wavelength components L1 and L2. The The measurement object 8 can be displaced back and forth on the optical axis with respect to the chromatic aberration lens 7.

  The light of each wavelength component reflected by the surface to be measured is multiplexed through the chromatic aberration lens 7, passes through the pinhole 6 again, is converted into parallel light by the condensing lens 5 which is a collimating lens, and the beam It passes through the splitter 4. The parallel light that has passed through the beam splitter is diffracted by the diffraction grating 9 at different diffraction angles for the different wavelength components L1 and L2, and condensed by the condenser lens 10 at different positions on the image sensor 11 as measurement light.

  The collected measurement light is incident on the light receiving portion of the image sensor 11 and detected, and is output to the processing device 12 as an electrical signal. FIG. 8 shows a spectral spectrum of the measurement light processed by the processing device 12. In the drawing, a solid line P1 indicates a case where the measured surface 8a of the measurement object 8 is near the position S1 on the optical axis, and a broken line P2 indicates a case where the measured surface is near the position S2. The light of the wavelength components L1 and L2 is focused on the measured surface when the measured surface 8a is at the positions S1 and S2, respectively. Therefore, the positions S1 and S2 of the measured surface 8a are measured by detecting peak wavelengths λ1 and λ2 at which the light intensity is maximum from the curves P1 and P2 in FIG.

  However, as shown in FIG. 8, the light intensity curves P1 and P2 are relatively gentle around the peak. Furthermore, the image pickup device 11 is generally constituted by an array in which a large number of photoelectric conversion elements are arranged at regular intervals. Therefore, the light intensity curves P1 and P2 in FIG. 8 are actually approximate curves formed by connecting a large number of points plotting the outputs from the photoelectric conversion elements. For this reason, the light intensity curve is likely to vary due to noise and errors of the optical distance meter itself, and it is relatively difficult to accurately detect the peak wavelengths λ1 and λ2, which may cause measurement errors.

  Further, when the measurement target surface 8a of the measurement object 8 is not a colorless mirror surface but colored, the reflectance of each wavelength differs depending on the color. When the surface to be measured is colored in a color having a low reflectance, the light intensity detected from the image sensor 11 decreases corresponding to the reflectance.

  FIG. 9 shows a spectrum detected when it is assumed that the reflectivity of the surface 8a to be measured changes with respect to the wavelength as shown by the one-dot difference line in the figure. For comparison, the light intensity curves P1 and P2 in the case of total reflection in FIG. Since the light intensity curve P1 has a low reflectance in the corresponding wavelength region, the peak position is very low and is greatly shifted to the + side, and the light intensity curve P1 is a very gentle light intensity curve p1 as a whole. The light intensity curve P2 has a relatively high reflectance in the corresponding wavelength region, so that the peak position is slightly lowered and shifted to the + side, and the light intensity curve P2 as a whole is somewhat gentle. In either case, not only is the vicinity of the peak of the light intensity curve more gradual than in the case of total reflection, but also the peak wavelength shifts, so it is difficult to accurately detect the position of the measured surface 8a.

  Therefore, the present invention has been made in view of the above-described conventional problems, and an object thereof is confocal spectroscopy capable of measuring the position with high accuracy and stability regardless of the reflectance of the surface to be measured. An optical distance meter and a distance measuring method are provided.

  In order to achieve the above object, the optical distance meter of the present invention separates the light source and the illumination light from the light source into first and second polarization direction components orthogonal to each other, and the first and second polarization direction components are separated. The illumination optical system for projecting images at different positions on the optical axis of the surface to be measured, the photodetector, and the first and second polarization direction components reflected from the surface to be measured are And a detection optical system for forming an image at different positions.

  By configuring in this way, the photodetector can detect the light intensities of the first and second polarization direction components reflected from the surface to be measured. Since the detected first and second polarization direction components have different imaging positions on the optical axis of the surface to be measured, their light intensities become curves having peak wavelengths at different positions. When the difference between the light intensities is calculated, a light intensity curve having a waveform that always passes through the zero point and changes relatively steeply and linearly near the zero point is obtained. Since the wavelength at which this difference is 0 can be detected with higher accuracy than the peak wavelength, the position of the surface to be measured can be measured with higher accuracy by using this.

  Moreover, when the reflectance of the surface to be measured is not constant with respect to the wavelength, it greatly affects the detected light intensity of the first and second polarization direction components, and the position of the peak wavelength is shifted. Even in such a case, the wavelength at which the difference in light intensity is zero does not change, so that the position of the surface to be measured can be measured stably.

  In one embodiment, the illumination optical system separates the illumination light from the light source into first and second polarization direction components orthogonal to each other, and the first and second polarization directions emitted from the birefringence plate. By having a condensing lens that projects the components to form images at different positions on the optical axis of the surface to be measured, an optical rangefinder with less noise and errors can be configured.

  In another embodiment, the illumination optical system has a polarization maintaining fiber that transmits the illumination light from the light source and makes it incident on the birefringent plate, so that the measurement object is located away from the main body portion of the optical distance meter. The surface to be measured can be measured.

  In another embodiment, the illumination optical system has a pinhole array in which a large number of pinholes are arranged so that the illumination light from the light source is condensed, diffused, and incident on the birefringent plate. A large number of points on the surface to be measured can be measured simultaneously. As a result, the two-dimensional shape of the measurement object can be measured more easily. Furthermore, the two-dimensional shape of the measurement object can be measured by scanning the surface to be measured with illumination light.

  According to yet another embodiment, the illumination optical system combines the first and second polarization direction components reflected from the surface to be measured and emits them to the detection optical system, and the detection optical system is from the illumination optical system. By separating the incident light into the first and second polarization direction components, it is not necessary to separately provide the optical path of the reflected light from the surface to be measured according to the polarization direction. Can do.

  In some embodiments, the light source is a white light source, allowing measurements over a wide wavelength range. In this case, the detection optical system needs to have a dispersive element that disperses incident light from the illumination optical system for each different wavelength.

  In another embodiment, the light intensity of the first and second polarization direction components incident on the photodetector is detected, the difference between the light intensity of the first polarization direction component and the second polarization direction component is calculated, and the light intensity By further including a signal processing unit that determines the wavelength at which the difference becomes zero, the position of the surface to be measured can be measured with a single optical distance meter without the need for an external processing device.

  According to another aspect of the present invention, illumination light from a light source is separated into first and second polarization direction components orthogonal to each other, and the first and second polarization direction components are different from each other on the optical axis of the surface to be measured. The light is projected to form an image at a position, the light intensities of the first and second polarization direction components reflected from the surface to be measured are detected, and the difference between the light intensities of the first and second polarization direction components is calculated. There is provided a distance measurement method for calculating, determining a wavelength at which the difference in light intensity is zero, and measuring the position of the surface to be measured based on this wavelength.

  The wavelength at which the difference between the light intensities of the first and second polarization direction components reflected from the surface to be measured is zero can be detected with higher accuracy than the peak wavelength and is not affected by the reflectance of the surface to be measured. Thus, the position of the surface to be measured can be stably measured with higher accuracy.

  In one embodiment, the illumination light is white light, and after the first and second polarization direction components reflected from the measurement surface are dispersed for different wavelengths, the light intensity of the first and second polarization direction components is obtained. Can be measured over a wide wavelength range.

The block diagram of 1st Example of the optical distance meter by this invention. FIG. 3 is a detailed view of a head portion of the first embodiment. FIG. 3 is a detailed view of a light detection unit according to the first embodiment. (A) is a diagram showing the spectrum of the first embodiment, (B) is a diagram showing the spectrum when the reflectance of the surface to be measured changes with respect to wavelength, and (C) is the surface to be measured. FIG. 5 is a diagram showing a comparison between a case where the reflectance of a light source is constant with respect to a wavelength and a case where the reflectance changes. (A) is a block diagram of a second embodiment of the optical distance meter according to the present invention, and (B) is a schematic perspective view of the pinhole plate of the second embodiment. The schematic perspective view of the photodetector of 2nd Example. The block diagram which shows the typical example of the optical distance meter of a prior art. The diagram which shows the spectrum of the optical distance meter of FIG. FIG. 9 is a diagram showing the case where the reflectance of the surface to be measured changes with respect to the wavelength in the spectral spectrum of FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are denoted by the same or similar reference numerals.

  FIG. 1 shows the configuration of a first embodiment of an optical distance meter according to the present invention. The optical distance meter 21 of the present embodiment includes a head portion 21a for projecting illumination light on a measurement object located at a position away from the main body portion and receiving the reflected light.

  The main part of the optical distance meter 21 includes a white light source 22, a collimating lens 23, and a beam splitter 24 arranged on the same optical axis, and a condensing lens 25 and one of the optical fibers 26 on an optical axis perpendicular to the optical axis. An end portion 26a is disposed. The optical fiber 26 is made of a polarization-maintaining fiber having birefringence in its cross section, and the other end 26b is connected to the head portion 21a.

  As shown in FIG. 2, the head portion 21 a has a birefringent plate 27 and a chromatic aberration lens 28 disposed on the same optical axis as the end portion 26 b of the optical fiber 26. The birefringent plate 27 is made of, for example, a birefringent material such as a quartz plate, and emits the incident linearly polarized light into polarized components orthogonal to each other, that is, separated into an ordinary light component and an extraordinary light component. The chromatic aberration lens 28 is a combination lens in which a concave lens 28a and a convex lens 28b having different refractive indexes such as crown glass and flint glass are bonded together.

  Further, the main part of the optical distance meter 21 is provided with a concave diffraction grating 29 on the opposite side of the beam splitter 24 on the same optical axis as the condenser lens 25, and the birefringent plate 30 in the diffraction direction of the diffraction grating. And the image pick-up element 31 is arrange | positioned. In another embodiment, a flat plate diffraction grating can be used instead of the concave diffraction grating 29. In that case, it is necessary to dispose a condenser lens as in the conventional example of FIG.

  Similarly, the birefringent plate 30 is formed of a birefringent material such as a quartz plate and separates the incident linearly polarized light into an ordinary light component and an extraordinary light component and emits them. As shown in FIG. 3, the image pickup device 31 has linear image sensors 32 a and 32 b in which photoelectric conversion elements such as photodiodes are arranged in one row as light receiving portions, which are arranged in two rows in parallel. The image sensor 31 is connected to a signal processing unit 33 for processing an output signal from the linear image sensor.

  In the optical distance meter 21, the white irradiation light emitted from the light source 22 is converted into parallel light by the collimator lens 23, reflected by the beam splitter 24, and condensed on the end portion 26 a of the optical fiber 26 by the condenser lens 25. . The optical fiber 26 is an aperture stop similar to a pinhole, and transmits irradiation light to the head unit 21a without changing the polarization state. Irradiation light exiting from the end portion 26b of the optical fiber 26 is diffused and separated into an ordinary light component and an extraordinary light component when passing through the birefringent plate 27. It is condensed so as to form an image on the axis.

  Even if the ordinary light component and the extraordinary light component of the irradiation light separated by the birefringent plate 27 have the same wavelength, they are imaged at different positions S1 and S2 on the optical axis of the measured surface 34a. At this time, the measuring object 34 is arranged so that the measured surface 34a is between the positions S1 and S2 on the optical axis.

  The ordinary light component and the extraordinary light component reflected by the surface to be measured are converged by the chromatic aberration lens 28, are combined again when passing through the birefringent plate 27, and are condensed on the end portion 26b of the optical fiber 26, and the polarization thereof. It is transmitted through the optical fiber while maintaining the state. The reflected light that exits the end portion 26 a of the optical fiber 26 is diffused, converted into parallel light by the condensing lens 25 that is a collimating lens, and then transmitted through the beam splitter 24.

  The parallel light transmitted through the beam splitter is diffracted by the concave diffraction grating 29 at different diffraction angles for the different wavelength components L1 and L2, and converged to form an image on the image sensor 31 as measurement light. As shown in FIG. 3, the measurement light L passes through the birefringent plate 30 before being incident on the image sensor 31 and is separated into an ordinary light component Lo and an extraordinary light component Le. The ordinary light component Lo passes straight through the birefringent plate 30 and enters one linear image sensor 32a. The extraordinary light component Le shifts from the ordinary light component Lo by a predetermined separation width, and the other linear image sensor 32b. Is incident on.

  The measurement light incident on the image sensor 31 is output to the signal processing unit 33 as an electric signal and processed. The signal processing unit 33 performs the following processing. First, necessary processing such as correction and amplification is performed on the output signals from the linear image sensors to detect the light intensities P1 and P2 of the ordinary light component Lo and the abnormal light component Le. Next, a difference ΔP = P1−P2 between the light intensities of the ordinary light component Lo and the extraordinary light component Le is calculated. Then, the wavelength λ0 at which the difference ΔP is 0 is detected, and the position of the measured surface 34a is calculated based on the wavelength λ0.

  FIG. 4A shows a spectral spectrum of measurement light processed by the signal processing unit 33 when the reflectance of the measurement target surface 34a is assumed to be constant. As described above, since the irradiation light is projected onto the measurement surface 34a via the birefringent plate 27, the ordinary light component and the extraordinary light component are imaged at different positions on the optical axis at the same wavelength. Therefore, the light intensities P1 and P2 are curves having different peak wavelength positions, and the light intensity curve with the difference ΔP always passes through the zero point of the light intensity. Moreover, the change in the vicinity of the zero point of this curve is steep and linear compared to the change in the vicinity of the peak. Therefore, the wavelength λ0 where the difference ΔP = 0 can be detected with higher accuracy.

  FIG. 4B shows a spectral spectrum of the measurement light processed by the processing device 33 when it is assumed that the reflectance of the measurement target surface 34a changes with respect to the wavelength. In the figure, the reflectivity changes as indicated by a one-point difference line. Due to this influence, the light intensities p1 and p2 of the ordinary light component Lo and the extraordinary light component Le have waveforms with respect to the light intensities P1 and P2 in FIG. 4A as described above with reference to the prior art in FIG. It is greatly deformed and the peak wavelength is also shifted. Correspondingly, the difference Δp = p1−p2 between the light intensities p1 and p2 is also greatly deformed from the waveform of FIG. Also in this case, the light intensity curve of the difference Δp always passes the zero point of the light intensity.

  FIG. 4C shows the light intensity curve of the difference Δp in FIG. 4B in comparison with the light intensity curve of the difference ΔP in FIG. As can be seen from the figure, the wavelength at which the light intensity curve of the difference Δp passes through the zero point is exactly the same as the wavelength λ0 through which the light intensity curve of the difference ΔP passes through the zero point. As described above, according to the present invention, by using the difference between the detected signals for the ordinary light component and the abnormal light component of the measurement light, the measurement target is not affected by the reflectance or noise of the measurement target surface 34a. The position of the surface can be detected with high accuracy.

  FIG. 5A shows the configuration of a second embodiment of the optical distance meter according to the present invention. In the optical distance meter 41 of the present embodiment, a white light source 42, a condenser lens 43, and a beam splitter 44 are arranged on the same optical axis, and a pinhole plate 45, a birefringent plate on an optical axis perpendicular thereto. 46 and a telecentric chromatic aberration lens 47 are arranged. On the opposite side of the beam splitter 44 on the same optical axis as the pinhole plate 45, a concave diffraction grating 48 is disposed, and a birefringent plate 49 and an image sensor 50 are disposed in the diffraction direction of the diffraction grating. ing.

  As shown in FIG. 5B, the pinhole plate 45 is composed of a pinhole array in which a large number of pinholes 45a are arranged in a horizontal row at regular intervals. The birefringent plates 46 and 49 are formed of a birefringent material such as a quartz plate, for example, as in the first embodiment, and separate the incident linearly polarized light into mutually orthogonal polarized components, that is, an ordinary light component and an extraordinary light component. Then exit. In another embodiment, a flat type diffraction grating can be used in place of the concave type diffraction grating 48. In this case, a condensing lens is required as in the conventional example of FIG.

  The image sensor 50 is an area image sensor in which a large number of photoelectric conversion elements such as photodiodes are arranged in a plane, for example, in a lattice shape as a light receiving unit. In this embodiment, as shown in FIG. 6, a photodiode array 51, 52 in which a large number of photodiodes 51a, 52a are arranged in one row is arranged in parallel. A signal processing unit 53 for processing an output signal from the photodiode array is connected to the image sensor 50.

  In the optical distance meter 41, the white irradiation light emitted from the light source 42 is converged by the condensing lens 43, reflected by the beam splitter 44, and condensed on each pinhole 45a of the pinhole array. Irradiation light exiting each pinhole 45a diffuses and is separated into an ordinary light component and an extraordinary light component when passing through the birefringent plate 46, and is parallel to each other by the telecentric chromatic aberration lens 47 and the position of each pinhole. Are focused so as to form an image on the optical axis at each point on the measurement surface 54a of the measurement object 54 corresponding to.

  Even if the ordinary light component and the extraordinary light component of each irradiation light separated by the birefringent plate 46 have the same wavelength, they are imaged at different positions S1 and S2 on the optical axis of the measured surface 54a. The measurement object 54 is arranged so that the measured surface 54a is between the positions S1 and S2 on the optical axis.

  The ordinary light component and the extraordinary light component reflected at each point on the surface to be measured are converged by the telecentric chromatic aberration lens 47, and are combined when passing through the birefringent plate 46 again, and collected in the original pinhole 45a. Lighted. The reflected light exiting each pinhole diffuses and passes through the beam splitter 44, enters the concave diffraction grating 48, is diffracted at different diffraction angles for different wavelength components L1 and L2, and is used as measurement light. Focusing is performed so as to form an image on the image sensor 50.

  The measurement light is transmitted through the birefringent plate 49 before being incident on the image sensor 50, and is separated into an ordinary light component Lo and an extraordinary light component Le. As shown in FIG. 6, the ordinary light component Lo passes straight through the birefringent plate 49 and enters one photodiode array 51, and the extraordinary light component Le is shifted from the ordinary light component Lo by a predetermined separation width. , And enters the other photodiode array 52. In the present embodiment, measurement light from each point on the measurement target surface 54a can be simultaneously incident on the corresponding photodiodes 51a and 52a of the respective photodiode arrays.

  The measurement light incident on the image sensor 50 is output to the signal processing unit 53 as an electrical signal and processed, as in the first embodiment. That is, the signal processing unit 53 performs necessary processes such as correction and amplification on the output signals from the respective photodiode arrays, detects the light intensities P1 and P2 of the ordinary light component Lo and the abnormal light component Le, and these light intensities. The difference ΔP = P1−P2 is calculated. Then, the wavelength λ0 at which the difference ΔP is 0 is detected for each point on the measured surface 54a, and the position of each point is calculated simultaneously based on these wavelengths λ0.

  As described above, according to the present embodiment, the position of a large number of points can be detected at a high accuracy at a time without being affected by the change in reflectance or noise on the surface to be measured 54a, and the two-dimensional measurement of the surface to be measured. The shape can be measured. Furthermore, if the surface to be measured 54a is scanned and illumination light is projected, the three-dimensional shape of the measurement object 54 can be measured.

  In another embodiment, the pinhole array of the pinhole plate 45 can be changed to a slit-shaped aperture stop. In this case, the position on the measured surface 54a can be measured as a continuous line.

  The present invention is not limited to the above embodiments, and can be implemented with various modifications or changes within the technical scope thereof. For example, the optical fiber in the first embodiment can be replaced with a pinhole. In addition, the birefringent plate in each embodiment can be used in various other known structures such as a parallel plate structure and a bifocal lens. Further, a wavelength tunable light source can be used instead of the white light source. In this case, the reflected light from the measurement surface only needs to be separated by the polarization direction before being incident on the image sensor, so that a dispersive element such as a diffraction grating can be omitted.

1, 2, 41 ... optical distance meter, 2, 22, 42 ... white light source, 3, 23 ... collimating lens, 4, 24, 44 ... beam splitter, 5, 10, 25, 43 ... condensing lens, 6, 45a ... pinhole, 7, 28 ... chromatic aberration lens, 8, 34, 54 ... measurement object, 8a, 34a, 54a ... measurement surface, 9 ... diffraction grating, 11, 31, 50 ... imaging device, 12 ... processing device, 21a ... Head part, 26 ... Optical fiber, 26a, 26b ... End, 27, 30, 46, 49 ... Birefringent plate, 28a ... Concave lens, 28b ... Convex lens, 29, 48 ... Concave diffraction grating, 32a, 32b ... Linear Image sensor, 33, 53 ... signal processing unit, 45 ... pinhole plate, 47 ... telecentric chromatic aberration lens, 51, 52 ... photodiode array, 51a, 52a ... photodiode.

Claims (10)

  A light source and illumination light from the light source are separated into first and second polarization direction components orthogonal to each other, and the first and second polarization direction components are imaged at different positions on the optical axis of the surface to be measured. An illumination optical system for projecting, a photodetector, and a detection optical system for imaging the first and second polarization direction components reflected from the surface to be measured at different positions of the photodetector, respectively. An optical distance meter characterized by that.   The illumination optical system separates the illumination light from the light source into first and second polarization direction components orthogonal to each other, and the first and second polarization direction components emitted from the birefringence plate The optical distance meter according to claim 1, further comprising a condensing lens that projects so as to form images at different positions on the optical axis of the surface to be measured.   The optical distance meter according to claim 2, wherein the illumination optical system includes a polarization maintaining fiber that transmits illumination light from the light source and causes the illumination light to enter the birefringent plate.   The said illumination optical system has a pinhole array which arranged many pinholes so that the illumination light from the said light source may be condensed, diffused and made to inject into the birefringent plate. Optical distance meter as described.   The illumination optical system combines the first and second polarization direction components reflected from the surface to be measured and outputs the combined light to the detection optical system, and the detection optical system receives incident light from the illumination optical system. The optical rangefinder according to claim 1, wherein the first and second polarization direction components are separated.   The optical distance meter according to claim 1, wherein the light source is a white light source.   The optical distance meter according to claim 6, wherein the detection optical system includes a dispersive element that disperses incident light from the illumination optical system at different wavelengths.   The light intensity of the first and second polarization direction components incident on the photodetector is detected, the difference of the light intensity of the first polarization direction component and the second polarization direction component is calculated, and the difference of the light intensity is The optical distance meter according to claim 1, further comprising a signal processing unit that determines a wavelength to be a zero value.   The illumination light from the light source is separated into first and second polarization direction components orthogonal to each other, and the first and second polarization direction components are projected to form images at different positions on the optical axis of the surface to be measured. Detecting the light intensities of the first and second polarization direction components reflected from the surface to be measured, calculating a difference between the light intensities of the first and second polarization direction components, and calculating the light intensity. A distance measurement method characterized by determining a wavelength at which the difference between the two values becomes 0 and measuring the position of the surface to be measured based on the wavelength.   The illumination light is white light, and after the first and second polarization direction components reflected from the measurement surface are dispersed for different wavelengths, the light intensity of the first and second polarization direction components is detected. The distance measuring method according to claim 9, wherein:

Images