JP2018185201A - Optical image measurement device - Google Patents

Abstract

An optical image measurement apparatus capable of acquiring images at a plurality of depth positions in a short measurement time without using a broadband light source.
An optical image measuring device according to the present invention has a first time point when a first light spot is irradiated and a second time point when a second light spot is irradiated with a time interval shorter than the scanning time for one pixel. Switch with.
[Selection] Figure 3

Description

  The present invention relates to an optical image measurement device that observes a measurement object using light.

  Optical coherence tomography (OCT: Optical Coherence Tomography) is a technique for acquiring a tomographic image of a measurement object using light interference, and has been put into practical use in the field of fundus examination since 1996. In recent years, cardiology, dentistry Application to various fields such as medicine, oncology, food industry and regenerative medicine is being studied.

  The following Patent Document 1 describes a technique related to OCT. As described in this document, in OCT, light from a light source is branched into two parts: a signal light that irradiates a measurement object and a reference light that is reflected by a reference light mirror without irradiating the measurement object. A measurement signal is obtained by combining the signal light reflected from the reference light with the reference light to cause interference.

  OCT is roughly divided into a time domain OCT and a Fourier domain OCT according to a method of scanning the measurement position in the optical axis direction (hereinafter referred to as z scan). In the time domain OCT, a low-coherence light source is used as a light source, and a z-scan is performed by scanning a reference light mirror during measurement. As a result, only the component having the same optical path length as the reference light included in the signal light interferes, and the desired signal is demodulated by performing envelope detection on the obtained interference signal. The Fourier domain OCT is further divided into a wavelength scanning type OCT and a spectral domain OCT. In the wavelength scanning OCT, a wavelength swept light source capable of scanning the wavelength of emitted light is used, z scanning is performed by scanning the wavelength during measurement, and the wavelength dependence (interference) of the detected interference light intensity is detected. A desired signal is obtained by Fourier transforming the spectrum. In the spectral domain OCT, a wide-band light source is used as a light source, the generated interference light is dispersed by a spectroscope, and the interference light intensity (interference spectrum) for each wavelength component is detected corresponding to the z scan. A desired signal is obtained by Fourier-transforming the obtained interference spectrum.

US2014 / 020204388

  In the conventional OCT apparatus described above, the depth resolution is determined by the wavelength bandwidth or wavelength sweep width of light. Therefore, a light source having a wide wavelength band such as a super luminescent diode (SLD) or a wavelength swept light source is used. These light sources are more expensive than ordinary laser light sources that generate narrow band light. Further, due to the wide wavelength band of light to be used, an optical element corresponding to broadband light is necessary, and chromatic dispersion compensation is also essential. For these reasons, it has been difficult to reduce the cost of the conventional OCT apparatus.

  Therefore, the present inventors invented the optical measuring device described in Patent Document 1. This optical measurement device uses a high NA (Numerical Aperture) objective lens to collect and irradiate laser light (signal light) onto the measurement object, and scans the objective lens to scan the condensing position. Acquire a tomographic image of the object. This optical measurement device enables three-dimensional measurement using the principle that the reflected light component other than the focal point of the objective lens included in the signal light does not interfere with the reference light because the wavefront curvature does not coincide with the reference light. The principle is fundamentally different from that of a conventional OCT apparatus using an SLD or a swept wavelength light source. In this configuration, since an expensive light source is not required, an inexpensive optical image measurement device can be provided. On the other hand, the measurement time tends to be long because it takes time to scan the condensing position.

  The present invention has been made in view of the above problems, and an object thereof is to provide an optical image measurement device that can acquire images at a plurality of depth positions in a short measurement time without using a broadband light source. To do.

  In the present invention, the irradiation position of the first light spot and the irradiation position of the second light spot are shifted from each other in a direction that is not parallel to the scanning direction by the scanning unit. The timing control unit switches between a first timing at which the first light spot is irradiated and a second timing at which the second light spot is irradiated on the measurement target, according to a switching time interval. The scanning unit switches between the first timing and the second timing at the switching time interval shorter than one cycle of the scanning frequency at which the irradiation positions of the first and second light spots are scanned. Thereby, the tomographic image to be measured can be acquired in a shorter time than in the past.

  For example, reference light and measurement light are generated by optical branching, and signal light is combined with the reference light to generate three or more interference lights having different phase relationships, and light emitted from the light source. Are propagated as light having different propagation angles, thereby shifting the irradiation position of the first light spot and the irradiation position of the second light spot. Thereby, the tomographic image of the measurement object can be acquired with higher resolution in the optical axis direction.

  As an example, a light spot is scanned by driving an objective lens. Thereby, a tomographic image to be measured can be acquired with a smaller and less expensive configuration.

  As an example, the distance between the center position of the first light spot and the center position of the second light spot is shifted by a distance corresponding to one pixel of the image. As a result, a tomographic image of the measurement target can be acquired in a shorter time than before while scanning a plurality of light spots almost uniformly within the measurement region.

  As an example, the positions of the light spots are shifted from each other in the optical axis direction. Thereby, tomographic images at two different depth positions can be acquired by one measurement.

  As an example, the light emitted from the light source is branched into first angle light and second angle light having different propagation angles, and a light shield is disposed on the optical path of the first angle light and the second angle light. Thus, the first angle light and the second angle light are shielded. Thereby, the distance between a plurality of light spots can be easily controlled with high accuracy.

  As an example, the light source includes a first light source and a second light source, and the light emitted from the first light source and the light emitted from the second light source are used as first angle light and second angle light having different propagation angles. By propagating, the first angle light is irradiated as the first light spot, and the second angle light is irradiated as the second light spot. Thereby, the timing at which a plurality of light spots are generated with a simple configuration can be controlled.

  As an example, the first and second light spots are repeatedly scanned along a first direction, and the first and second light spots are moved at a substantially constant speed along a second direction orthogonal to the first direction. The light spot is displaced, and the scanning unit scans the first and second light spots less than N times along the first direction, thereby obtaining the image having N pixels in the second direction. Thereby, the tomographic image to be measured can be acquired in a shorter time than in the past.

  As an example, the first and second light spots are repeatedly scanned at the scanning frequency along the first direction, and the first light spot is scanned at a substantially constant speed along the second direction orthogonal to the first direction. The timing control unit displaces the first and second light spots, and the timing control unit irradiates the measurement object with m light spots at a position corresponding to one pixel in the second direction of the image. As described above, the timing is controlled, and the timing control unit is configured such that the time interval from when the objective lens irradiates the measurement target with the first light spot to the mth light spot is The timing is controlled so as to be shorter than one cycle of the scanning frequency. Thereby, a signal sufficient to generate an image of N pixels can be sampled.

  According to the present invention, it is possible to provide an optical image measurement device that acquires a tomographic image to be measured in a short time without using a broadband light source such as an SLD or a wavelength sweep light source. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

1 is a schematic diagram illustrating a configuration example of an optical image measurement device according to Embodiment 1. FIG. It is a figure explaining the time scale of the movement of the focus position of the objective lens, and the irradiation timing of the 1st and 2nd light spot by the timing control part. It is a figure explaining the scanning path | route of the 1st and 2nd light spot. 6 is a schematic diagram of an optical image measurement device according to Embodiment 2. FIG. 3 is a top view showing an example of the structure of a pinhole disk 407. FIG. It is a figure explaining the scanning path | route of the 1st-3rd light spot. It is a schematic diagram of the optical image measurement device according to the third embodiment. 2 is a structural example of a two-surface reference light mirror 701. It is a figure explaining the scanning path | route of the 1st and 2nd light spot.

<Embodiment 1: Configuration of optical system>
FIG. 1 is a schematic diagram illustrating a configuration example of an optical image measurement apparatus according to Embodiment 1 of the present invention. The first laser light emitted from the first light source 101 is converted into parallel light by the collimator lens 102, and after passing through the polarization beam splitter 103, the optical axis is set to about 22.5 degrees with respect to the horizontal direction. The polarized light is adjusted to 45-degree linearly polarized light by the λ / 2 plate 108 and enters the polarizing beam splitter 109. The second laser light emitted from the second light source 104 is converted into parallel light by the collimator lens 105, the polarization state is changed to the S polarization state by the λ / 2 plate 106, the light is reflected by the polarization beam splitter 103, and then optical Polarization is adjusted to 45 degrees linearly polarized light by a λ / 2 plate 108 whose axis is set to about 22.5 degrees with respect to the horizontal direction, and is incident on the polarization beam splitter 109. The incident angle of the first laser beam and the incident angle of the second laser beam are different from each other at the time of entering the polarizing beam splitter 109. Such a relative angular shift can be realized, for example, by appropriately setting the positions of the collimating lenses 102 and 105. The timing control unit 107 controls the light emission timing so that the first light source 101 and the second light source 104 emit light alternately and periodically.

The first laser light is split into two, the first measurement light and the first reference light, by the polarization beam splitter 109, and the second laser light is split into two, the second measurement light and the second reference light, by the polarization beam splitter 109. . The first and second measurement lights are converted in polarization state from s-polarized light to circularly-polarized light by the λ / 4 plate 110 whose optical axis direction is set to about 22.5 degrees with respect to the horizontal direction, and then the objective lens 111. Are incident at different angles. Thereby, the first light spot and the second light spot are irradiated to the sample 113. As will be described later, the first light spot and the second light spot are only a distance corresponding to one pixel of the image in the x direction. Generated at a remote location. The objective lens 111 is linearly driven in the x direction while being repeatedly driven in the y-axis direction at a frequency f _{sig by} , for example, a sine wave by the objective lens actuator 112, whereby the irradiation positions of the first and second light spots are changed in the xy direction. Scanned.

  The first and second signal lights obtained by reflecting or scattering the first and second measurement lights from the sample 113 pass through the objective lens 111 again, and the polarization state is changed from circularly polarized light to p-polarized light by the λ / 4 plate 110. And enters the polarization beam splitter 109. The sample 113 is made of a material that transmits light to some extent, and may be any material as long as non-invasive observation of the internal structure is desired. For example, a semiconductor multilayer structure, food, plant, cultured cell, human tissue, and the like are conceivable.

  The first and second reference lights are converted from p-polarized light to circularly-polarized light by the λ / 4 plate 114 whose optical axis direction is set to about 22.5 degrees with respect to the horizontal direction, and then the reference light lens The light is condensed and irradiated on the reference light mirror 116 by 115. The reference light mirror 116 is disposed at the focal position of the reference light lens 115. The first and second reference lights reflected by the reference light mirror 116 pass through the reference light lens 115 again, the polarization state is converted from circularly polarized light to s-polarized light by the λ / 4 plate 114, and is incident on the polarization beam splitter 109. .

  The polarization beam splitter 109 generates the first combined light by combining the first signal light and the first reference light. The first synthesized light is incident on the interference optical system 124. The interference optical system 124 includes a half beam splitter 117, a λ / 2 plate 118, a λ / 4 plate 121, condenser lenses 119 and 122, and Wollaston prisms 120 and 123. The first combined light incident on the interference optical system 124 is branched into two by the half beam splitter 117 into transmitted light and reflected light. The first combined light transmitted through the half beam splitter 117 passes through the λ / 2 plate 118 whose optical axis is set to about 22.5 degrees with respect to the horizontal direction, and is then collected by the condenser lens 119. The Wollaston prism 120 generates first interference light and second interference light having a phase relationship of 180 degrees different from each other by polarizing and separating the first combined light. The current differential type photodetector 125 detects the first interference light and the second interference light, and outputs a differential output signal 126 proportional to the difference in intensity between them.

  The first combined light reflected from the half beam splitter 117 passes through the λ / 4 plate 121 whose optical axis is set to about 45 degrees with respect to the horizontal direction, and is then collected by the condenser lens 122. The Wollaston prism 123 generates third interference light and fourth interference light having a phase relationship of about 180 degrees different from each other by polarization-separating the first combined light. The third interference light is approximately 90 degrees out of phase with the first interference light. The current differential photodetector 127 detects the third interference light and the fourth interference light, and outputs a differential output signal 128 proportional to the difference in intensity between them.

  The second signal light and the second reference light are combined by the polarization beam splitter 109 to generate the second combined light. Since the subsequent processing of the second combined light is the same as that of the first combined light, description thereof is omitted here. The image generation unit 129 generates an image based on the generated differential output signals 126 and 128, and the image display unit 130 displays the image.

FIG. 2 is a diagram for explaining the time scale of the movement of the focal position of the objective lens 111 and the irradiation timings of the first and second light spots by the timing control unit 107. As shown in FIG. 2A, the time required for the focal position of the objective lens 111 to move by a distance corresponding to one line of the image is ½f _sig . Therefore, when the number of pixels of the image of the sample 113 acquired by the optical image measurement device according to the first embodiment is N × N, the time required for the focal position of the objective lens 111 to move by a distance corresponding to one pixel. Is about ½ Nf _{sig on} average (FIG. 2B). In the first embodiment, the timing control unit 107 causes the first light source 101 and the first light source 101 to move while the focal position of the objective lens 111 moves by a distance corresponding to one pixel (average time of 1/2 Nf _sig ). The light emission state of the two light sources 104 is switched at least once. In other words, the first light source 101 and the second light source 104 emit light alternately at a frequency of at least 2Nf _sig . Thereby, as shown in FIG. 2C, for example, the first and second light spots can be generated on the measurement object at least once during the time when the focal position of the objective lens 111 moves by one pixel. It is possible to sample enough signals to produce an N × N pixel image for each of the first and second light spots.

  The timing of generating the first and second light spots is such that the first and second light spots are irradiated to the measurement object at least once each while the focal position of the objective lens 111 moves by one pixel. Any timing is acceptable. When the first and second light spots are generated once each while the focal position of the objective lens 111 moves by one pixel as shown in FIG. 2C, twice as shown in FIG. 2D. When generating, all patterns are conceivable.

On the other hand, if the frequency at which the first light source 101 and the second light source 104 are alternately emitted is too large, the timing controller 107 and the photodetectors 125 and 127 need to have high performance (high speed). As a result, the cost increases. Therefore, the first light source 101 not larger than the frequency to emit the second light source 104 are alternately required, for example, from about _{2NF sig} or to set a range of degree less than or equal to about _{4Nf sig} preferred.

  FIG. 3 is a diagram for explaining scanning paths of the first and second light spots. For the sake of explanation, the light spot is schematically shown by a large circle. The same applies to FIG. 6 described later. In the conventional optical image measurement device, in order to generate an image of N × N pixels, it is necessary to repeatedly move the light spot position in the scanning axis direction (y-axis direction) at least N times (here, the measurement region y). One-way movement from one end of the direction to the other is counted as one time). In the first embodiment, the irradiation position of the first light spot and the irradiation position of the second light spot are shifted by a distance corresponding to one pixel in the direction orthogonal to the repeated scanning axis (x-axis direction) and described with reference to FIG. As described above, by generating the data at different timings, it is possible to acquire information for two lines of the image by moving the light spot once. Therefore, it is possible to generate an image of N × N pixels by moving the light spot N / 2 times less than before. That is, an image can be generated in about half the time of the conventional method.

<Embodiment 1: Spatial resolution>
The spatial resolution in the optical axis direction of the optical image measurement device according to the first embodiment will be described. In the first embodiment, reflected light components other than the focal point of the objective lens 111 included in the first and second signal lights have defocus aberrations, and the first and second having flat wavefronts. The reference beam and wavefront shape do not match. Therefore, it does not interfere with the reference light uniformly in space, and many interference fringes are formed on the light receiving surface of the detector. When such interference fringes are formed, the value obtained by integrating the intensity of the detected interference light in the light receiving surface is almost equal to the sum of the intensity of the signal light and the reference light. The components of the differential output signals 126 and 128 corresponding to the reflected light component from are substantially zero. By such a principle, the reflected light component from other than the focal point of the objective lens 111 does not effectively interfere with the reference light, and only the reflected light component from the focal point of the objective lens 111 is selectively detected, and the optical axis direction High spatial resolution is achieved. The spatial resolution in the optical axis direction is determined by the numerical aperture NA of the objective lens and the wavelength λ of the laser light, and is proportional to λ / NA ² . In general, the wavelength of light used in the OCT apparatus is about 600 nm to 1300 nm which is not easily absorbed by hemoglobin or water. For example, when the numerical aperture of the objective lens 111 is 0.4 or more, the spatial resolution in the optical axis direction at wavelengths of 600 nm to 1300 nm is about 3.3 μm to about 7.2 μm.

<Embodiment 1: Operation Principle of Optical System>
Hereinafter, the function of the interference optical system 124 will be described using mathematical expressions. The Jones vector of the first combined light at the time of incidence on the interference optical system 124 is expressed by the following formula 1.

The Jones vector of the combined light after passing through the half beam splitter 117 and the λ / 2 plate 118 is expressed by the following formula 2. E _sig represents the complex amplitude of the signal light, and E _ref represents the complex amplitude of the reference light.

The combined light represented by Equation 2 is bifurcated into a p-polarized component and an s-polarized component by the Wollaston prism 120 and then differentially detected by the current differential photodetector 125. At this time, the electrical signal output from the photodetector 125 is expressed by the following Equation 3. θ _sig and θ _ref are phases when the complex amplitude numbers E _sig and E _ref are expressed in polar coordinates, respectively. For simplicity, the conversion efficiency of the detector was set to 1.

  On the other hand, the Jones vector of the combined light reflected by the half beam splitter 117 and further transmitted through the λ / 4 plate 121 is expressed by the following formula 4.

  The combined light represented by Equation 4 is bifurcated into a p-polarized component and an s-polarized component by the Wollaston prism 123, and then differentially detected by the current differential photodetector 127. At this time, the electrical signal output from the photodetector 127 is expressed by the following Equation 5.

  The image generation unit 129 performs a calculation represented by the following equation 6 on the signals represented by the equations 3 and 5, thereby making the signal proportional to the absolute value of the amplitude of the signal light independent of the phase. Is generated.

<Embodiment 2>
FIG. 4 is a schematic diagram of an optical image measurement device according to Embodiment 2 of the present invention. Components that are the same as those shown in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. In the second embodiment, (a) the diffraction grating 403 is used as a means for generating a plurality of light spots for the sample 113, and (b) the timing for generating individual light spots is shifted. The difference from the first embodiment is that a pinhole disk 407 is used as timing adjustment means.

  The laser light emitted from the light source 401 is converted into parallel light by the collimator lens 402, and is separated into three light beams of the first laser light, the second laser light, and the third laser light having different angles by the diffraction grating 403. The first to third laser beams pass through the polarization beam splitter 404 and change the polarization state from p-polarized light to circularly-polarized light by the λ / 4 plate 405 whose optical axis direction is set to about 22.5 degrees with respect to the horizontal direction. After the conversion, the light is condensed at different positions on the pinhole disk 407 by the lens 406. The structure of the pinhole disk 407 will be described later.

  The first to third laser beams that have passed through the pinhole disk 407 are converted into parallel light by the lens 410 and then focused on the mirror 412 by the lens 411. The mirror 412 is disposed at the focal position of the lens 411. The first to third laser beams reflected by the mirror 412 are transmitted again through the lenses 411 and 410, the pinhole disk 407, and the lens 406, and then converted from circularly polarized light to s polarized light by the λ / 4 plate 405. The light is reflected and enters the λ / 2 plate 108. Subsequent apparatus configurations are the same as those in the first embodiment, and thus description thereof is omitted.

  FIG. 5 is a top view showing an example of the structure of the pinhole disk 407. A large number of pinholes are arranged on the surface of the pinhole disk 407, and the timing control unit 107 controls the motor 408 to rotate the pinhole disk 407, so that one of the first to third laser lights. Can be transmitted alternately.

The first to third laser beams have propagation angles different from each other by a predetermined amount, and the first to third light spots are alternately arranged at three positions different from each other by a distance corresponding to one pixel of the image in the x direction with respect to the sample 113. Generated. In the second embodiment, the timing control unit 107 applies the first to third light spots while the focal position of the objective lens 111 moves by a distance corresponding to one pixel (on average, a time of 1/2 Nf _sig ). It was decided to generate at least once.

  FIG. 6 is a diagram for explaining scanning paths of the first to third light spots. In the second embodiment, the first to third light spots are repeatedly generated at different timings at positions shifted by a distance corresponding to one pixel in the direction orthogonal to the scanning axis (x-axis direction). As a result, the information for three lines of the image can be acquired by one movement of the light spot, so that an image of N × N pixels can be generated by the movement of the light spot N / 3 times less than the conventional one. it can.

  In the second embodiment, since the first to third laser beams having different angles are generated using the diffraction grating 403, unlike the first embodiment, the distance between the light spots is set regardless of the position of the collimating lens. It can be set with high accuracy.

<Embodiment 3>
FIG. 7 is a schematic diagram of an optical image measurement device according to Embodiment 3 of the present invention. Components that are the same as those shown in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted. The third embodiment is different from the first embodiment in that the irradiation positions of the first and second light spots irradiated on the sample 113 are different from each other in the optical axis direction.

  The first laser light emitted from the first light source 101 is converted into parallel light by the collimating lens 102. The second laser light emitted from the second light source 104 is converted into a state having a predetermined defocus aberration by the collimating lens 105. The defocus amount can be adjusted by the position of the collimating lens 105 in the optical axis direction. In the third embodiment, a two-surface reference light mirror 701 described later is provided instead of the reference light mirror 116.

If the amount of displacement in the optical axis direction of the collimator lens 105 from the position where the defocus aberration of the second laser beam is 0 is Δz _col , the defocus amount applied to the second laser beam is approximately 7 can be expressed. NA _col is the numerical aperture of the collimating lens 105.

Since the defocus amount expressed by Expression 7 is given to the second laser light, the second light spot is generated at a position shifted by a predetermined amount Δz _sig from the first light spot in the optical axis direction. The shift amount Δz _sig is approximately expressed by the following formula 8 when the numerical aperture of the objective lens 111 is NA _sig .

Similarly, when the defocus amount represented by Expression 7 is given to the second laser light, the condensing position of the second reference light by the reference light lens 115 is changed from the condensing position of the first reference light. The amount is different by the amount represented by the following formula 9. NA _ref is the numerical aperture of the reference light lens 115.

FIG. 8 is a structural example of the two-surface reference light mirror 701. The two-surface reference light mirror 701 has a first reflecting surface 801 and a second reflecting surface 802, and the interval between the two reflecting surfaces is about Δz _ref . Therefore, the first and second reference lights can be reflected at the respective condensing positions.

FIG. 9 is a diagram for explaining the scanning paths of the first and second light spots. In the third embodiment, the first and second light spots are generated at different timings at positions shifted by a predetermined distance Δz _sig in the optical axis direction, so that different depths can be obtained by moving the light spot N times. Two images corresponding to the position can be generated.

<Modification of the present invention>
The present invention is not limited to the above-described embodiments, and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. For example, in the configuration of the first and second embodiments, the configuration for displacing the light spot in the optical axis direction described in the third embodiment can be added.

101: first light source 102: collimating lens 103: polarizing beam splitter 104: second light source 108: λ / 2 plate 109: polarizing beam splitter 110: λ / 4 plate 111: objective lens 112: objective lens actuator 113: sample 114: λ / 4 plate 115: Reference light lens 116: Reference light mirror 117: Half beam splitter 118: λ / 2 plate 119: Condensing lens 120: Wollaston prism 121: λ / 4 plate 122: Condensing lens 123: Wollaston Prism 124: Interference optical system 125: Photo detector 127: Photo detector 129: Image generation unit 130: Image display unit

Claims (11)

An optical image measurement device that acquires an image of a measurement object,
A light source that emits light,
An objective lens that collects the light emitted from the light source and irradiates the measurement object as a first light spot and a second light spot;
A scanning unit that scans the irradiation positions of the first and second light spots;
A timing controller for controlling the timing at which the first and second light spots are irradiated to the measurement object;
A photodetector that detects signal light generated by reflection or scattering of light at a position at which the first and second light spots are irradiated on the measurement object;
With
The irradiation position of the first light spot and the irradiation position of the second light spot are shifted from each other in a direction not parallel to the scanning direction by the scanning unit,
The timing control unit switches between a first timing at which the measurement object is irradiated with the first light spot and a second timing at which the measurement object is irradiated with the second light spot. Switch by time interval,
The timing control unit is configured to switch between the first timing and the second timing at the switching time interval shorter than one cycle of a scanning frequency at which the scanning unit scans the irradiation positions of the first and second light spots. The optical image measuring device characterized by switching. The optical image measurement device further includes
An optical branching element that generates reference light and measurement light that is irradiated onto the measurement object by the objective lens from light emitted from the light source,
An interference optical system that generates three or more interference lights having different phase relationships by combining the signal light with the reference light;
An optical element that shifts the irradiation position of the first light spot and the irradiation position of the second light spot by propagating light emitted from the light source as light having different propagation angles,
With
The optical image measuring device according to claim 1, wherein the photodetector detects the interference light and outputs the detected signal as an electrical signal. The optical image measurement device according to claim 1, wherein the scanning unit is configured using an actuator that moves the objective lens. 3. The optical element according to claim 2, wherein the distance between the center position of the first light spot and the center position of the second light spot is shifted by a distance corresponding to one pixel of the image. Optical image measurement device. The optical image measurement device further adjusts a condensing position along the optical axis direction of the first light spot to a first condensing position, and sets the condensing position along the optical axis direction of the second light spot. The optical image measuring device according to claim 1, further comprising an optical element that adjusts to a second condensing position different from the first condensing position. The optical image measurement device further includes a light branching element that branches light emitted from the light source into first angle light and second angle light having different propagation angles,
The optical image measurement device further includes a light shield disposed on an optical path of the first angle light and the second angle light to shield the first angle light and the second angle light,
The timing controller irradiates the first light spot when the light shield blocks the second angle light at the first timing, and the light shield blocks the first angle light at the second timing. The optical image measuring device according to claim 1, wherein the shader is controlled so that the second light spot is irradiated by doing so. The optical image measurement device includes a first light source and a second light source as the light source,
The optical image measurement device further propagates the light emitted from the first light source and the light emitted from the second light source as first angle light and second angle light having different propagation angles, thereby causing the first angle. An optical element that allows light to be irradiated as the first light spot and the second angle light to be irradiated as the second light spot;
The timing control unit includes the timing at which the first light source emits light and the first light spot so that the first light spot is irradiated at the first timing and the second light spot is irradiated at the second timing. The optical image measurement device according to claim 1, wherein the timing at which the two light sources emit light is controlled. The optical image measurement device includes a first light source and a second light source as the light source,
The optical element is configured such that a propagation angle of light emitted from the first light source and a propagation angle of light emitted from the second light source are different from each other, thereby irradiating the irradiation position of the first light spot and the second light. The optical image measurement device according to claim 2, wherein the irradiation positions of the spots are shifted from each other. The scanning unit repeatedly scans the first and second light spots along a first direction, and the first and second light spots at a substantially constant speed along a second direction orthogonal to the first direction. Displace two light spots,
The image has N pixels in the second direction;
The scanning unit generates the signal light for obtaining the image having N pixels in the second direction by scanning the first and second light spots less than N times along the first direction. The optical image measuring device according to claim 1. The scanning unit repeatedly scans the first and second light spots at a scanning frequency along a first direction and at a substantially constant speed along a second direction orthogonal to the first direction. Displacing the first and second light spots;
The timing control unit controls the timing so that the objective lens emits m light spots to the measurement target at a position corresponding to one pixel in the second direction of the image;
In the timing control unit, the time interval from when the objective lens irradiates the measurement target with the first light spot to the mth light spot becomes shorter than one cycle of the scanning frequency. The optical image measurement device according to claim 1, wherein the timing is controlled as follows. The objective lens irradiates the measurement object with a third light spot in addition to the first and second light spots,
The scanning unit scans the irradiation position of the third light spot in addition to the irradiation positions of the first and second light spots,
The timing control unit switches between the first timing, the second timing, and a third timing at which the measurement object is irradiated with the third light spot according to the switching time interval,
The timing control unit includes the first timing and the second timing at the switching time interval shorter than one cycle of a scanning frequency at which the scanning unit scans irradiation positions of the first, second, and third light spots. The optical image measuring device according to claim 1, wherein the timing is switched between the timing and the third timing.

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