JP2020030166A - Distance measuring device and method - Google Patents

Abstract

To provide a distance measuring device capable of measuring an objective distance using a simplified optical system, without needing a spatial filter.SOLUTION: A distance measuring device 10 comprises: an irradiation optical system that condenses light from a light source 11 on a measurement target T and radiates the light; a lattice 14 that emits light having a periodic intensity distribution by changing the intensity distribution of incident light, with reflected light reflected from the measurement target T as the incident light; a light detection element 15 that detects lattice fringes generated by the light having the periodic intensity distribution emitted from the lattice 14; and a distance calculation unit 16 that calculates an object distance to the measurement target T based on the detection result obtained by the light detection element 15.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a distance measuring device and method, and more particularly to an optical distance measuring technique for irradiating an object with light and reflecting the light, and measuring an object distance to a measurement target based on the reflected light.

  2. Description of the Related Art Conventionally, there has been known an optical measuring device capable of measuring an object distance to a measurement target in a non-contact manner using light such as laser light. Such an optical measuring device is applied not only to measuring an object distance to a measurement target but also to various uses such as measurement of a surface shape of a measurement target and measurement of a thickness of a thin film.

  For example, Patent Literature 1 discloses an amplitude type diffraction grating that diffracts reflected light reflected from a measurement target, a condenser lens that condenses diffracted light from the diffraction grating on an image forming surface, and a condenser lens that is disposed on the image forming surface. Further, there is disclosed a distance measuring device having a spatial filter that transmits only two different orders of diffracted light set in advance and blocks other orders of diffracted light.

  The distance measuring device described in Patent Document 1 uses a spatial filter to transmit only two predetermined orders of diffracted light from many orders of diffracted light generated by the amplitude type diffraction grating. Then, the object distance is measured by causing the two orders of diffracted light to interfere with each other.

  More specifically, in the distance measuring device described in Patent Literature 1, an amplitude type diffraction grating having a rectangular transmittance distribution is used. For this reason, in the distance measuring device described in Patent Document 1, not only diffracted light of a desired specific order, for example, ± 1st-order diffracted light, but also higher-order diffracted light and straight-through transmission without diffraction are provided. Zero-order diffracted light appears.

  Further, in the distance measuring device described in Patent Literature 1, Fourier transform is performed using a condenser lens in order to cause only diffracted light beams of two predetermined orders to interfere with each other. The filter filters and transmits the desired two orders of diffracted light.

JP 2015-194347 A

  However, according to the technology described in Patent Document 1, it is necessary to adjust the positions of the condenser lens and the spatial filter to a suitable position. If this adjustment is not sufficient, interference fringes may be disturbed to perform distance measurement. May be difficult. Further, the spatial filter is required to have high processing accuracy, and thus has a problem that the configuration of the optical system is complicated.

  The present invention has been made in order to solve the above-described problems, and provides a distance measuring device that does not require a spatial filter and can measure an object distance using a more simplified optical system. With the goal.

  In order to solve the above-described problem, the distance measuring device according to the present invention is an irradiation optical system that condenses light from a light source on a measurement target and irradiates the measurement target, and uses reflected light reflected from the measurement target as incident light. A grating that emits light having a periodic intensity distribution by changing the intensity distribution of the incident light, and a photodetector that detects lattice fringes generated by the light having the periodic intensity distribution emitted from the grating. A distance calculation unit that calculates an object distance from the light detection element to the measurement target based on a detection result obtained by the light detection element.

  Further, in the distance measuring device according to the present invention, the distance measuring apparatus further includes a filter for selectively passing the diffuse reflection light out of the diffuse reflection light and the regular reflection light included in the reflection light reflected from the measurement target, May use light passing through the filter as the incident light.

  In the distance measuring device according to the present invention, the filter may be configured by a polarizing element.

  Further, in the distance measuring device according to the present invention, the measurement target has a diffuse reflection surface, the reflected light reflected from the measurement target is diffuse reflection light, and the distance calculation unit includes the light detection element The objective distance a from the measurement object to the position of the grid is determined by: a = dL / (P−d) (d is the pitch of the grid, L is (The distance to the photodetector).

  Further, in the distance measuring device according to the present invention, the measurement target has a specular reflection surface, the reflected light reflected from the measurement target is specular reflection light, and the distance calculation unit includes the light detection element The object distance a from the measurement object to the position of the grating is calculated as follows: a = dL / 2 (P−d) + t / 2 (d is the pitch of the grating, L May be calculated from a distance from the grating to the photodetector, and t may be a distance from a position where light from the light source is condensed by the irradiation optical system to the grating.

  Further, in the distance measuring device according to the present invention, the grating may include an amplitude grating having a light-transmitting portion and a light-shielding portion which are arranged one-dimensionally and periodically alternately.

  Further, in the distance measuring device according to the present invention, the amplitude type grating may have a transmittance distribution that spatially changes in a rectangular wave shape.

  Further, in the distance measuring device according to the present invention, the distance from the grating to the light detecting element may be a Fourier image distance determined by a pitch of the grating, a wavelength of light from the light source, and the objective distance. .

  Further, in the distance measuring device according to the present invention, the grating has a liquid crystal layer and a plurality of electrodes arranged along a surface of the liquid crystal layer, and each of the plurality of electrodes individually separates the liquid crystal layer. A spatial light modulator for adjusting the transmittance by applying a voltage to the liquid crystal layer and performing intensity modulation on the incident light incident on the liquid crystal layer.

  The distance measuring apparatus according to the present invention may further include a condenser lens for condensing reflected light reflected from the measurement target, and the grating may be configured to convert the reflected light condensed by the condenser lens to incident light. It may be.

  Further, in the distance measuring device according to the present invention, an optical element that condenses the light having the periodic intensity distribution emitted from the grating in a direction perpendicular to an optical axis in a direction in which the intensity of the lattice fringes changes. Further, it may be provided.

  Further, in the distance measurement device according to the present invention, the irradiation optical system includes a light source lens for condensing light from the light source, and a beam splitter for directing light emitted from the light source lens to the measurement target. Is also good.

  Further, in the distance measuring device according to the present invention, the light irradiated on the measurement target by the irradiation optical system may be polarized light.

  Further, in the distance measuring method according to the present invention, the irradiation step of condensing and irradiating light from a light source to a measurement target, and the reflected light reflected from the measurement target as incident light, the intensity distribution of the incident light An intensity distribution generating step of emitting light having a periodic intensity distribution instead, and a detecting step of detecting, with a photodetector, lattice fringes generated by the light having the periodic intensity distribution emitted in the intensity distribution generating step. A distance calculating step of calculating an object distance from the light detecting element to the measurement target based on the detection result obtained in the detecting step.

  According to the present invention, a grating that emits light having a periodic intensity distribution by changing the intensity distribution of incident light reflected from an object to be measured is eliminated, so that a spatial filter is not required and a more simplified optical system is provided. The objective distance can be measured using the system.

FIG. 1 is a schematic diagram illustrating a configuration of a distance measuring device according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating the principle of distance measurement according to the first embodiment of the present invention. FIG. 3 is a block diagram illustrating a configuration example of a computer that realizes the distance calculation unit according to the first embodiment of the present invention. FIG. 4 is a flowchart illustrating the operation of the distance measuring device according to the first embodiment of the present invention. FIG. 5 is an image example showing lattice fringes generated on the detection surface according to the first embodiment of the present invention. FIG. 6 is a schematic diagram illustrating a configuration of a distance measuring device according to the second embodiment of the present invention. FIG. 7A is a schematic diagram illustrating a configuration of a distance measuring device according to the third embodiment of the present invention. FIG. 7B is a schematic diagram illustrating a configuration of a distance measuring device according to the third embodiment of the present invention. FIG. 8 is a schematic diagram illustrating a configuration of a distance measuring device according to a fourth embodiment of the present invention. FIG. 9 is a diagram showing a modification of the distance measuring device according to the embodiment of the present invention.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS.
[First Embodiment]
FIG. 1 is a schematic diagram illustrating a configuration of a distance measuring device 10 according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating the principle of distance measurement according to the first embodiment. In the present embodiment, a case where the measurement target T is a diffuse reflection surface will be described.
The distance measuring device 10 irradiates and reflects light on the measurement target T, and measures an object distance to the measurement target T based on the reflected light.

  The distance measuring device 10 includes a light source 11, a light source lens 12, a beam splitter 13, a grating 14, a photodetector 15, and a distance calculator 16. The distance measuring device 10 may be housed in a casing whose configuration is not shown, for example.

  The light source 11, the light source lens 12, and the beam splitter 13 constitute an irradiation optical system that condenses the light emitted from the light source 11 onto the measurement target T and irradiates the light.

  The light source 11 is a device that emits light used for distance measurement. In the present embodiment, the light from the light source 11 may be a monochromatic light such as a semiconductor laser device or a sodium lamp, or a device that outputs a single wavelength light by a white light source and a narrow band pass filter. it can.

  The light source lens 12 condenses the light emitted from the light source 11 and emits the light to the beam splitter 13.

  The beam splitter 13 is disposed on the optical path O of the focusing optical system, reflects light from the light source 11 condensed by the light source lens 12, and irradiates the light spot A of the measurement target T along the optical path O. . In addition, the beam splitter 13 causes the reflected light, which is reflected in the optical path O direction, of the reflected light diffusely reflected by the light spot A to be incident on the grating 14.

  The grating 14 is disposed on the optical path O, and receives reflected light from the measurement target T that has passed through the beam splitter 13. The grating 14 changes the intensity distribution of the incident light and emits light having a periodic intensity distribution. The emitted light having the periodic intensity distribution generates lattice fringes, which are light and dark fringes of light.

The grating 14 is formed of an amplitude grating in which light-transmitting portions and light-shielding portions are two-dimensionally and periodically arranged. More specifically, the grating 14 has a configuration in which a large number of slits formed by periodically arranging light absorbing portions (light shielding portions) on a substrate that transmits light are arranged at equal intervals in parallel. In the present embodiment, a case where a transmission type amplitude type grating is used as the grating 14 will be described, but a reflection type grating may be used.
In the present embodiment, the grating 14 has a spatially rectangular transmittance distribution, for example, a grating pitch of several hundred microns.

In the distance measuring device 1 according to the present embodiment, the distance from the grating 14 to the photodetector 15 is set to be near the Fourier image distance determined by the pitch of the grating 14, the wavelength from the light source 11, and the objective distance a. Is done. Specifically, the distance L from the grating 14 to the light detection element 15 is determined by the following equation (1).
L = nd ² a / (nd ² −aλ) (1)
In the above equation (1), n is an integer, d is the pitch of the grating 14, λ is the wavelength of light from the light source 11, and a is the objective distance. Here, the objective distance a refers to the distance from the measurement target T to the grating 14, as shown in FIG.

  In this manner, by setting the distance from the grating 14 to the light detecting element 15 to be the Fourier image distance, the light detecting element 15 can clearly display the grating fringes generated by the light having the periodic intensity distribution emitted from the grating 14. An image can be detected. Therefore, the photodetector 15 can more accurately determine the pitch of the lattice fringes.

  More specifically, since the grating 14 has the transmittance distribution in the form of a rectangular wave as described above, as the distance from the grating 14 increases, the component of the fundamental order of the light transmitted through the grating 14 becomes 3 Next, the fifth-order, seventh-order, and other components have different phases. Since the light emitted from the grating 14 is deviated from the basic order, if the distance from the grating 14 is other than the Fourier image distance, the lattice fringes detected by the photodetector 15 may have a distorted shape. For this reason, in the present embodiment, the photodetector 15 is installed at a position away from the grating 14 by the Fourier image distance.

  Here, as a specific example of the distance L from the grating 14 to the photodetector 15, n = 1 in the above equation (1), λ = 600 nm, the pitch d of the grating 14 = 0.19 mm, and the objective distance a = When it is set to 60 mm, L is set to 30 mm.

  The light detection element 15 detects lattice fringes generated by light having a periodic intensity distribution emitted from the lattice 14 and outputs a detection result. More specifically, the light detection element 15 has a detection surface I, and detects lattice fringes on the detection surface I. As the light detection element 15, for example, a light receiving element arranged on one dimension such as a CCD (Charged Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) linear image sensor, or a photodiode array can be used.

  The distance calculation unit 16 performs arithmetic processing from the detection result obtained by the light detection element 15 to extract the period length of the lattice fringe, and calculates the object distance a from the lattice 14 to the measurement target T based on the obtained period length. calculate. The details of the configuration of the distance calculation unit 16 will be described later.

[Principle of distance measurement]
Next, the principle of distance measurement in the distance measurement device 10 according to the present invention will be described with reference to FIG.

  In FIG. 2, only the focusing optical system of the distance measuring device 10 is shown as a main part, and the irradiation optical system is omitted.

As shown in FIG. 2, when the surface of the measurement target T is a diffuse reflection surface, the objective distance from the measurement target T to the position of the grating 14 is a, and the distance from the grating 14 to the detection surface I of the photodetector 15 is L, the pitch of the grating fringes detected on the detection surface I is P, the wavelength of the light source 11 is λ, and the pitch of the grating 14 is d, based on the similarity between ABB ′ and ACC ′, the objective distance a is It is expressed by the following equation (2).
a = dL / (P−d) (2)

[Hardware Configuration of Distance Calculation Unit]
Next, the configuration of the distance calculation unit 16 that performs the arithmetic processing for calculating the above-described objective distance a will be described with reference to FIG.
The distance calculation unit 16 includes a computer including a computing device 102 having a CPU 103 and a main storage device 104 connected via a bus 101, a communication control device 105, an I / F 106, an external storage device 107, a display device 108, and the like. It can be realized by a program that controls these hardware resources.

As shown in FIG. 3, the light detection element 15 is connected to the distance calculation unit 16 via the I / F 106, and outputs the obtained detection result to the distance calculation unit 16 via the I / F 106.
The display device 108 is configured by a liquid crystal display or the like, and displays a calculation result of the object distance a by the arithmetic device 102.

  The communication control device 105 is a control device for connecting various external electronic devices via a communication network. The communication control device 105 may send the calculation result of the objective distance a and the like to the outside via a communication network.

[Operation of distance measuring device]
Next, the operation of the distance measuring device 10 having the above-described configuration will be described with reference to the flowchart of FIG.

  First, the measurement target T is arranged in the distance measuring device 10. Further, initial adjustments such as the light amount of the light source 11 and the exposure time are performed.

  Thereafter, the light emitted from the light source 11 is condensed by the light source lens 12, and is irradiated toward the measurement target T by the beam splitter 13 (Step S1). Next, the light reflected from the measurement target T passes through the beam splitter 13 and enters the grating 14. The grating 14 changes the intensity distribution of the incident light and emits light having a periodic intensity distribution (step S2).

  Next, lattice fringes generated by light emitted from the grating 14 and having a periodic intensity distribution are detected by the photodetector 15 (step S3).

  After that, the light detection element 15 inputs information on the detected lattice fringe to the distance calculation unit 16. Then, the distance calculation unit 16 performs an operation based on the above-described principle of the distance measurement, and calculates the object distance a of the measurement target T (Step S5).

  FIG. 5 is an analysis example of the detection result obtained by the light detection element 15. Here, the horizontal axis indicates the pixel position [pic] of the image along the direction orthogonal to the grid pattern, and the vertical axis indicates the light intensity (no unit) at each pixel position. The obtained detection result has a substantially rectangular wave shape, and its peak position corresponds to a bright line. Therefore, the actual distance indicating the checkerboard pitch P can be calculated from the number of pixels existing between the peak positions.

  As described above, according to the present embodiment, the distance measuring device 10 uses the reflected light reflected from the measurement target T having the diffuse reflection surface as the incident light and changes the intensity distribution of the incident light to form a periodic light. The provision of the grating 14 for emitting light having an intensity distribution eliminates the need for a spatial filter and allows the objective distance a to be measured using a more simplified optical system.

[Second embodiment]
Next, a second embodiment of the present invention will be described. In the following description, the same components as those of the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

  In the first embodiment, the case where the measurement target T is a diffuse reflection surface has been described. On the other hand, in the second embodiment, a case where the measurement target T is a regular reflection surface will be described. Hereinafter, the configuration different from the first embodiment will be mainly described.

[Principle of distance measurement]
FIG. 6 is a schematic diagram showing a configuration of a distance measuring device 10A according to the present embodiment. Hereinafter, the principle of distance measurement in the present embodiment will be described with reference to FIG.
When the measurement target T is a diffuse reflection surface as in the first embodiment, light emitted toward the measurement target T diffuses from the surface of the measurement target T as a starting point. In the first embodiment, the distance to the measurement target T is measured by obtaining the starting point. On the other hand, when the measurement target T is a specular reflection surface as in the present embodiment, the light irradiated while being collected toward the measurement target T has the surface of the measurement target T at the focus point. Except in the case, the light is condensed at a place other than the surface of the measurement target T, and is diffused with the light condensing point as a starting point.

As shown in FIG. 6, the point at which the light irradiated toward the measurement target T converges is denoted by D. When the measurement target T is located far away, the light converges at the point D and then at the measurement target T. The light is reflected and diffused starting from a point E which is a virtual image of the point D. The distance between DA and the distance between AE are equal.
The object distance from the measurement object T to the position of the grating 14 is a, the distance from the grating 14 to the detection surface I of the photodetector 15 is L, the pitch of the lattice fringes detected on the detection surface I is P, Is d, and the distance from the position where the light from the light source is focused by the irradiation optical system to the grating is t, the distance between DA and the distance between A and E are equal, and EBB 'and ECC When the object distance a is obtained based on the similarity of ', it is expressed by the following equation (3).
a = dL / 2 (P−d) + t / 2 (3)

  The distance calculation unit 16 calculates the object distance a of the measurement target T using the above equation (3), using the information of the lattice fringe detected by the light detection element 15 as an input.

  As described above, according to the second embodiment, even when the measurement target T is a specular reflection surface, the distance measuring device 10A accurately measures the object distance a with a simplified optical system. be able to.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the following description, the same components as those in the above-described first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted.

  In the first and second embodiments, the case where the light reflected by the measurement target T is incident on the grating 14 has been described. On the other hand, in the third embodiment, a lens 17 (condensing lens) is provided between the measurement target T and the grating 14. Hereinafter, a description will be given focusing on a configuration different from the first and second embodiments.

7A and 7B are schematic diagrams illustrating a configuration of the distance measuring device 10B according to the present embodiment. 7A shows a case where the surface of the measurement target T is a diffuse reflection surface, and FIG. 7B shows a case where the surface of the measurement target T is a regular reflection surface.
The lens 17 is provided on the optical path O between the measurement target T and the beam splitter 13. The light from the light source 11 reflected by the beam splitter 13 is condensed by the lens 17 and is irradiated on the measurement target T. The light reflected from the measurement target T is condensed by the lens 17, passes through the beam splitter 13, and enters the grating 14.

[Principle of distance measurement when the measurement target is a diffuse reflection surface]
First, the principle of distance measurement when the surface of the measurement target T is a diffuse reflection surface will be described with reference to FIG. 7A.
Note that the lens 17 originally has two principal points according to the incident direction of light, and their respective positions are different. However, in the following, the lens 17 is formed of a thin single lens in order to avoid complicated expressions. Each equation was derived assuming that there is only one point at the lens center.

  As shown in FIG. 7A, the objective distance from the measurement target T to the position of the grating 14 is a, the distance from the measurement target T to the lens 17 is b, and the distance from the lens 17 to the grating 14 is h. The distance from the grating 14 to the detection surface I of the photodetector 15 is L, the distance from the detection surface I to the position Q of the image of the light collected by the lens 17 is c, and the focal length of the lens 17 is f. And As in the first and second embodiments, the pitch of the lattice fringes detected on the detection surface I is P, the wavelength of the light source 11 is λ, and the pitch of the grating 14 is d.

When the surface of the measurement target T is a diffuse reflection surface as shown in FIG. 7A, the relationship of the distance is expressed by the following equation (4) according to the formula of a thin lens.

Further, the following equation (5) is obtained from the similarity between QBB ′ and QCC ′ in FIG. 7A.

From the above equations (4) and (5), the objective distance a is obtained by the following equation (6).

[Principle of distance measurement when the measurement target is a specular reflection surface]
Next, the principle of distance measurement when the measurement target T is a regular reflection surface will be described with reference to FIG. 7B.

  As shown in FIG. 7B, the objective distance from the measurement target T to the position of the grating 14 is a, the distance from the measurement target T to the lens 17 is b, and the distance from the lens 17 to the grating 14 is h. The distance from the grating 14 to the detection surface I of the photodetector 15 is L, the distance from the detection surface I to the position Q of the image of the light collected by the lens 17 is c, and the focal length of the lens 17 is f. And

  The distance between DA and the distance between AE are s. More specifically, the point at which the light emitted toward the measurement target T converges is D, and when the measurement target T is located far away, the light is condensed at the point D and then reflected at the measurement target T. , From the point E which is a virtual image of the point D. As in the first and second embodiments, the pitch of the lattice fringes detected on the detection surface I is P, the wavelength of the light source 11 is λ, and the pitch of the grating 14 is d.

When the surface of the measurement target T is a specular reflection surface as shown in FIG. 7B, the relationship of the distance is expressed by the following equation (7) according to the formula of a thin lens.

The following equation (8) is obtained from the similarity between QBB ′ and QCC ′ in FIG. 7B.

Further, the following equation (9) is obtained from FIG. 7B.

From the above equations (7), (8), and (9), the objective distance a is obtained by the following equation (10).

  As described above, according to the distance measuring device 10B according to the third embodiment, the lens 17 is provided on the optical path O between the measurement target T and the grating 14, and the reflected light from the measurement target T is collected. The light is incident on the grating 14. Therefore, it is possible to measure the object distance a after collecting more reflected light from the measurement target T. This is particularly effective when the distance from the measurement target T to the photodetector 15 cannot be reduced due to design reasons.

  Further, the distance measuring device 10B according to the third embodiment can accurately measure the object distance a even when the measurement target T is a diffuse reflection surface and a regular reflection surface.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. In the following description, the same components as those in the above-described first to third embodiments are denoted by the same reference numerals, and description thereof will be omitted.

  In the first embodiment, the case where the surface of the measurement target T is a diffuse reflection surface has been described, and in the second embodiment, the case where the surface of the measurement target T is a regular reflection surface has been described. In the third embodiment, the case where the surface of the measurement target T is a diffuse reflection surface and the case where the surface of the measurement object T is a regular reflection surface are described. On the other hand, in the fourth embodiment, a case will be described in which the surface of the measurement target T is a glossy surface and the specular reflection light and the diffuse reflection light are mixed in the reflection light. The distance measuring apparatus 10C according to the present embodiment further includes a polarizing element (filter) 18 between the beam splitter 13 and the grating 14. Hereinafter, the configuration different from the first to third embodiments will be mainly described.

  FIG. 8 is a schematic diagram illustrating a configuration of a distance measuring device 10C according to the present embodiment. Polarized light is used as the light emitted from the light source 11 to the measurement target T. The polarizing element 18 is provided on the optical path O between the beam splitter 13 and the grating 14, and the light reflected by the measurement target T passes through the beam splitter 13, passes through the polarizing element 18, and passes through the grating 14. Incident.

  The polarizing element 18 selectively transmits predetermined polarized light out of the reflected light reflected from the measurement target T. Specifically, the polarizing element 18 selectively allows the diffuse reflection light among the diffuse reflection light and the regular reflection light included in the reflection light reflected by the measurement target T to pass.

  Here, the polarizing element 18 is an optical element capable of removing polarized light in any one direction. Therefore, by aligning the direction of the polarization element 18 with the direction of the polarized light applied to the measurement target T, the polarized light can be substantially removed. For example, when non-polarized light is incident on the polarizing element 18, about half of the non-polarized light passes through the polarizing element 18 and about the other half is removed.

  From such characteristics, when the measurement object T is irradiated with polarized light and the reflected light is a mixture of the diffusely reflected light and the specularly reflected light, the direction of the polarizing element 18 can be adjusted to the direction of the specularly reflected light (polarized light). Specularly reflected light can be almost removed. At the same time, about half of the diffuse reflected light is removed by the polarizing element 18, but about half of the diffuse reflected light passes through the polarizing element 18. Therefore, the polarizing element 18 can selectively allow only the diffusely reflected light to pass.

[Principle of distance measurement]
Hereinafter, the principle of distance measurement in the present embodiment will be described with reference to FIG.
As described above, the origin from which the reflected light is diffused differs between the case where the reflected light from the measurement target T is the diffusely reflected light and the case where the reflected light is the specularly reflected light. Therefore, the formula used to determine the object distance a is different from the pitch P of the lattice fringes detected on the detection surface I.

  For example, when polarized light is used as light to be irradiated on the measurement target T, and the reflected light from the measurement target T is specular reflection light, the polarization state is preserved upon reflection, so that the reflected light is also polarized. I have. On the other hand, when the reflected light from the measurement target T is diffuse reflected light, the reflected light is unpolarized because the polarization state is not preserved during reflection.

  As shown in FIG. 8, linearly polarized light in a direction perpendicular to the plane of the paper is irradiated to the measurement target T, and reflected light from the measurement target T is made incident on a polarizing element 18 that transmits linearly polarized light in a direction parallel to the plane of the paper. The light that is specularly reflected on the surface of the measurement target T is removed, and only the light that is diffusely reflected passes through, enters the grating 14, and is detected by the photodetector 15. Since the light detected by the light detection element 15 is only the light diffusely reflected by the measurement target T, the object distance a can be obtained by using Expression (6).

  As described above, according to the distance measuring device 10C according to the fourth embodiment, even when the surface of the measurement target T is a glossy surface and the specular reflection light and the diffuse reflection light are mixed in the reflection light, the measurement can be performed. By using polarized light as light to be applied to the object T and installing the polarizing element 18 between the beam splitter 13 and the grating 14, the object distance a can be measured with high accuracy.

  In the embodiment described above, the case where the light detection element 15 directly detects the light transmitted through the grating 14 on the detection surface I has been described. However, the present invention is not limited to this. For example, as in a distance measuring device 10D shown in FIG. 9, a light collecting means (optical element) such as a cylindrical lens 19 may be further provided on the optical path O between the grating 14 and the light detecting element 15.

  This condensing means condenses the light emitted from the grating 14 in a direction in which the intensity of the lattice fringes changes and in a direction orthogonal to the optical axis. It should be noted that a reflecting mirror may be used instead of the condensing means utilizing refraction like the cylindrical lens 19.

  By further providing the above-mentioned light collecting means, the distance measuring device 10D can measure the object distance a based on a larger signal intensity (light reception amount).

  Further, a case has been described in which the distance measuring devices 10, 10A, 10B, 10C, and 10D according to the above-described embodiments include the grating 14 that changes the intensity distribution of incident light and emits light having a periodic intensity distribution. . However, instead of the grating 14, for example, a spatial light modulator can be used.

  The spatial light modulator has, for example, a liquid crystal layer and a plurality of electrodes arranged along the surface of the liquid crystal layer, and adjusts the transmittance by individually applying a voltage to the liquid crystal layer from each of the plurality of electrodes. Then, the intensity distribution is changed with respect to the incident light entering the liquid crystal layer, and light having a periodic intensity distribution is emitted. By using the spatial light modulator, the transmittance distribution can be made variable according to the application.

  The embodiments of the distance measuring device and the distance measuring method according to the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and those skilled in the art may refer to the scope of the invention described in the claims. Various possible modifications can be made.

  DESCRIPTION OF SYMBOLS 10 ... Distance measuring device, 11 ... Light source, 12 ... Light source lens, 13 ... Beam splitter, 14 ... Grating, 15 ... Light detection element, 16 ... Distance calculation part, T ... Measurement object, I ... Detection surface, a ... Objective distance , 101 bus, 102 arithmetic unit, 103 CPU, 104 main storage device, 105 communication control device, 106 I / F, 107 external storage device, 108 display device.

Claims (14)

An irradiation optical system that condenses light from a light source onto a measurement target and irradiates the light;
A grating that emits light having a periodic intensity distribution by changing the intensity distribution of the incident light, with reflected light reflected from the measurement target as incident light,
A photodetector that detects lattice fringes generated by the light having the periodic intensity distribution emitted from the lattice,
A distance calculation unit that calculates an object distance from the light detection element to the measurement target based on a detection result obtained by the light detection element. The distance measuring device according to claim 1,
Further comprising a filter for selectively passing the pre-Symbol diffuse reflection light of the diffuse reflected light and regular reflected light included in the reflected light reflected from the measurement object,
A distance measuring device, wherein the grating uses light passing through the filter as the incident light. The distance measuring device according to claim 2,
The said filter is comprised with a polarizing element, The distance measuring apparatus characterized by the above-mentioned. The distance measuring device according to any one of claims 1 to 3,
The measurement target has a diffuse reflection surface,
The reflected light reflected from the measurement target is diffuse reflected light,
The distance calculation unit calculates an object distance a from the measurement target to the position of the lattice based on the pitch P of the lattice fringes detected by the light detection element, a = dL / (P−d) (d is The pitch and L of the grating are calculated based on the distance from the grating to the photodetector. The distance measuring device according to any one of claims 1 to 3,
The measurement target has a specular reflection surface,
The reflected light reflected from the measurement target is specularly reflected light,
The distance calculation unit calculates an object distance a from the measurement target to the position of the lattice based on the pitch P of the lattice fringes detected by the light detection element, a = dL / 2 (P−d) + t / 2 (d is the pitch of the grating, L is the distance from the grating to the photodetector, and t is the distance from the position where light from the light source is collected by the irradiation optical system to the grating). A distance measuring device characterized by the above-mentioned. The distance measuring device according to any one of claims 1 to 5,
The distance measuring device according to claim 1, wherein the grating includes an amplitude type grating having a light-transmitting portion and a light-shielding portion which are arranged one-dimensionally and periodically alternately. The distance measuring device according to claim 6,
The distance measuring device, wherein the amplitude type grating has a transmittance distribution that changes spatially in a rectangular wave shape. The distance measuring device according to any one of claims 1 to 7,
A distance measuring device, wherein a distance from the grating to the light detecting element is a Fourier image distance determined by a pitch of the grating, a wavelength of light from the light source, and the objective distance. The distance measuring device according to any one of claims 1 to 8,
The lattice has a liquid crystal layer and a plurality of electrodes arranged along the surface of the liquid crystal layer, and adjusts the transmittance by individually applying a voltage to the liquid crystal layer from each of the plurality of electrodes. A spatial light modulator that performs intensity modulation on the incident light that enters the liquid crystal layer. The distance measuring device according to any one of claims 1 to 9,
Further comprising a condenser lens for condensing reflected light reflected from the measurement object,
The distance measuring device, wherein the grating uses the reflected light condensed by the condenser lens as incident light. The distance measuring device according to any one of claims 1 to 10,
A distance measuring device further comprising an optical element for condensing light having the periodic intensity distribution emitted from the grating in a direction in which the intensity of the lattice fringes changes and in a direction orthogonal to an optical axis. The distance measuring device according to any one of claims 1 to 11,
The irradiation optical system includes:
A light source lens for condensing light from the light source,
A beam splitter for directing light emitted from the light source lens to the object to be measured. The distance measuring device according to any one of claims 1 to 12,
The light emitted from the irradiation optical system to the object to be measured is polarized light. An irradiation step of irradiating the measurement target with light from the light source condensed,
An intensity distribution generating step of emitting light having a periodic intensity distribution by changing the intensity distribution of the incident light, with the reflected light reflected from the measurement object as incident light,
A detection step of detecting, with a photodetector, lattice fringes generated by the light having the periodic intensity distribution emitted in the intensity distribution generation step,
A distance calculation step of calculating an object distance from the photodetector to the measurement target based on the detection result obtained in the detection step.

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