JP6005506B2 - Optical measuring device - Google Patents

Description

  The present invention relates to an optical measurement device that irradiates an object with light and reflects it, and measures the distance to the object based on the reflected light.

  2. Description of the Related Art An optical measuring device that can measure the distance to an object in a non-contact manner using light such as laser light is known. Such an optical measuring device is not only for measuring the distance to an object, but also for various uses such as measuring the surface shape of an object and measuring the thickness of a thin film.

  As such an optical measuring device, for example, laser light is irradiated obliquely to the surface of an object, and the distance to the surface is calculated based on the principle of triangulation based on the position where the reflected light has reached. It has been known. Such an optical measuring apparatus is widely used as an inexpensive measuring apparatus because the apparatus configuration is relatively simple. However, since the tilt of the reflecting surface directly affects the distance measurement value, the measurement error increases when the surface of the object to be measured is not flat.

  On the other hand, as a measurement apparatus that can be used even when the surface of an object is not flat, an optical measurement apparatus that uses light interference has been proposed. For example, in the optical measuring apparatus described in Patent Document 1 below, light is irradiated to a measurement point of an object and reflected, and the reflected light reaches a CCD image sensor which is an interference fringe detection surface. It has a configuration.

  An optical lens system is disposed between the measurement point and the CCD image sensor, and the reflected light reaches the CCD image sensor through the optical lens system. The optical lens system is configured such that the reflected light from the point to be measured passes through a plurality of optical paths and is then irradiated on the CCD image sensor. Since the optical path lengths of the respective optical paths are different from each other, interference fringes are generated on the CCD image sensor due to the optical path difference.

  The fringe spacing of the interference fringes changes according to the distance between the measurement point and the CCD image sensor. Therefore, in this optical measuring device, the distance to the measurement point is calculated based on the fringe spacing obtained from the output of the CCD image sensor.

JP 2004-28977 A

  An optical lens system arranged to generate a plurality of optical paths having different optical path lengths is configured by a multifocal lens, a spherical lens, or the like that requires precise polishing. For this reason, it is generally expensive and requires precise assembly.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide an optical measurement apparatus that can accurately measure the distance to an object while having a simple configuration.

  In order to solve the above problems, an optical measurement apparatus according to the present invention is an optical measurement apparatus that irradiates and reflects light on an object, and measures the distance to the object based on the reflected light. A light source for generating light to irradiate the light, a condensing means disposed between the light source and the object, for condensing the light from the light source on the measurement point of the object, and reflection from the measurement point A first light-receiving surface which is a flat surface arranged so that a part of the light is directly incident on the first light-receiving surface, and a part of the reflected light is further reflected and incident on the first light-receiving surface. A first reflection surface arranged perpendicularly to the first light receiving surface, and first interference fringe measurement means for measuring the fringe spacing of the interference fringes generated on the first light receiving surface, and measured by the first interference fringe measurement means. The distance from the plane including the first light receiving surface to the measured point is calculated based on the fringe spacing. It is characterized in that.

  The optical measurement apparatus according to the present invention measures the distance to an object based on the fringe spacing of interference fringes generated by the reflected light by irradiating the object with light. The optical measuring device according to the present invention includes a light source, a light collecting means, a first light receiving surface, and a first reflecting surface.

  The light source generates light that irradiates an object. The light generated by the light source is coherent light. The condensing means is, for example, a convex lens, and condenses light generated by the light source at one point (measurement point) of the object. For this reason, reflection (scattering) of light from the object is performed only at one point to be measured. That is, the measurement point of the object can be regarded as a point light source that generates coherent light for generating interference fringes.

  The first light receiving surface is a flat surface arranged so that part of the reflected light from the measurement point is directly incident. The first reflecting surface is disposed perpendicular to the first light receiving surface, and is disposed so as to further reflect a part of the reflected light from the measurement point and enter the first light receiving surface. . With such a configuration, the first light receiving surface has reflected light that directly reaches the first light receiving surface from the measured point, and after reaching the first reflecting surface from the measured point and reflected by the first reflecting surface. The reflected light reaching the first light receiving surface is superimposed. The optical paths that the two reflected lights follow before reaching the first light receiving surface have different optical path lengths. For this reason, interference fringes are generated on the first light receiving surface due to the optical path difference.

  The optical measurement apparatus according to the present invention further includes first interference fringe measuring means for measuring the fringe spacing of the interference fringes generated on the first light receiving surface. The fringe spacing of the interference fringes is determined by the wavelength of the reflected light, the distance between the first reflecting surface and the measured point, and the distance between the first light receiving surface and the measured point. The size is proportional to the distance to the measurement point. For this reason, based on the fringe interval measured by the first interference fringe measuring means, the distance between the first light receiving surface and the measured point can be calculated.

  As described above, in the optical measuring device according to the present invention, the optical path difference and the interference fringes are generated by a simple configuration including the first reflecting surface and the first light receiving surface. The distance to the object, that is, the distance between the first light receiving surface and the measured point (the distance from the plane including the first light receiving surface to the measured point) is accurately measured based on the fringe spacing of the interference fringes. .

  Further, in the optical measuring device according to the present invention, the flat surface is disposed so that a part of the reflected light is directly incident, and is disposed in the same plane as the plane including the first light receiving surface. A second light-receiving surface, a second light-receiving surface arranged perpendicular to the second light-receiving surface so that a part of the reflected light is further reflected and incident on the second light-receiving surface, and the second light-receiving surface A second interference fringe measuring means for measuring the fringe spacing of the interference fringes generated on the surface, and a straight line that is perpendicular to the plane including the first light receiving surface and passes through the measured point is an intermediate line And the first light receiving surface and the second light receiving surface are arranged side by side with the intermediate line in between, the first reflective surface and the second reflective surface, They are parallel to each other and are disposed so as to face each other with the intermediate line in between. Based on the average value of the fringe interval measured by the fringe measuring means and the fringe interval measured by the second interference fringe measuring means, the measured object from the plane including the first light receiving surface and the second light receiving surface. It is also preferable to calculate the distance to the point.

  In this preferable aspect, the apparatus further includes a second light receiving surface, a second reflecting surface, and a second interference fringe measuring unit. The second light receiving surface is a flat surface arranged so that part of the reflected light from the measurement point directly enters, and is arranged in the same plane as the plane including the first light receiving surface. The second reflecting surface is disposed perpendicular to the second light receiving surface, and is disposed so as to further reflect a part of the reflected light from the measurement point and enter the second light receiving surface. . With such a configuration, the second light receiving surface has reflected light that directly reaches the second light receiving surface from the measured point, and after reaching the second reflecting surface from the measured point and reflected by the second reflecting surface. The reflected light reaching the second light receiving surface is superimposed. The optical paths that the two reflected lights follow until reaching the second light receiving surface have different optical path lengths. For this reason, interference fringes are generated on the second light receiving surface due to the optical path difference. Thus, in this preferable aspect, interference fringes are generated on each of the first light receiving surface and the second light receiving surface.

  In the following, for convenience of explanation, the fringe interval of interference fringes generated on the first light receiving surface, that is, the fringe interval measured by the first interference fringe measuring means may be referred to as “first fringe interval”. Further, the fringe interval of the interference fringes generated on the second light receiving surface, that is, the fringe interval measured by the second interference fringe measuring means may be referred to as “second fringe interval”.

  Here, a straight line (virtual straight line) that is perpendicular to the plane including the first light receiving surface and passes through the measurement point is defined as an “intermediate line”. In this preferred embodiment, the first light receiving surface and the second light receiving surface are arranged side by side so as to sandwich the intermediate line therebetween. Further, the first reflecting surface and the second reflecting surface are parallel to each other, and are arranged to face each other with the intermediate line therebetween.

  As described above, the first stripe interval is determined by the wavelength of the reflected light, the distance between the first reflecting surface and the measured point, and the distance between the first light receiving surface and the measured point. In other words, when the distance between the first reflecting surface and the point to be measured (which may be referred to as the distance between the first reflecting surface and the intermediate line) changes, the first fringe interval also changes accordingly. Similarly, when the distance between the second reflecting surface and the point to be measured (which may be referred to as the distance between the second reflecting surface and the intermediate line) changes, the second stripe interval also changes accordingly.

  Therefore, for example, when an impact due to an external force is applied to the optical measuring device and the first reflecting surface and the second reflecting surface are displaced with respect to the first light receiving surface, etc., the distance to the point to be measured Even though there is no change, the fringe spacing will change. That is, the distance to the measurement point calculated based on the fringe spacing of the interference fringes may be different from the actual distance.

  Therefore, in this preferred embodiment, the distance to the measurement point based on the average value of the first stripe interval and the second stripe interval (distance from the plane including the first light receiving surface and the second light receiving surface to the measurement point). This reduces the influence of the displacement of the first reflecting surface or the like on the distance calculation.

  For example, a case will be described in which the first reflecting surface is displaced so as to approach the intermediate line, while the second reflecting surface is displaced so as to be away from the intermediate line. In this case, the first fringe interval increases and the second fringe interval decreases with the displacement. As a result, the average value of the first stripe interval and the second stripe interval does not change much.

  As described above, if the displacements of the first reflecting surface and the second reflecting surface (the parallel movement as described above may be such a displacement that both rotate) are the same as each other, The change in the stripe interval and the change in the second stripe interval are opposite to each other. That is, when one increases, the other decreases.

  Therefore, by calculating the distance based on the average value of the first stripe interval and the second stripe interval, the influence of the displacement of the first reflecting surface or the like on the calculation of the distance is reduced. Thus, according to this preferable aspect, the distance measurement accuracy can be further improved.

  In the optical measuring device according to the present invention, it is also preferable that the first reflecting surface and the second reflecting surface are arranged at positions where the distances from the first reflecting surface and the intermediate line are equal to each other.

  In this preferred embodiment, the first reflecting surface and the second reflecting surface are arranged at positions where the distances from the first reflecting surface and the intermediate line are equal to each other. In other words, in the state where the optical measuring device is arranged to measure the distance to the measurement point, the distance between the first reflecting surface and the intermediate line and the distance between the second reflecting surface and the intermediate line are equal to each other. Thus, the position of the first reflecting surface and the position of the second reflecting surface in the optical measuring device are determined.

  By arranging the first reflecting surface and the second reflecting surface in this way, the average value of the first stripe interval and the second stripe interval when the first reflecting surface and the second reflecting surface are displaced. The change is further suppressed. When calculating the distance based on the average value, the influence of the displacement of the first reflecting surface or the like can be reduced, and the distance measurement accuracy can be further improved.

  Further, the optical measuring device according to the present invention comprises a transparent body made of a material transparent to the light generated from the light source, and arranged so that the reflected light passes through the inside thereof. Both the one reflecting surface and the second reflecting surface are preferably flat surfaces formed on the surface of the transparent body.

  In this preferred embodiment, a transparent body made of a material transparent to the light generated from the light source is arranged so that the reflected light from the measurement point passes through the inside thereof. The reflected light from the point to be measured reaches the first light receiving surface or the second light receiving surface after passing through the inside of the transparent body.

  Moreover, both a 1st reflective surface and a 2nd reflective surface are flat surfaces formed in the surface of the said transparent body. In other words, the transparent body has two flat surfaces that are parallel and opposed to each other on the surface thereof, and the respective flat surfaces are a first reflecting surface and a second reflecting surface.

  By setting it as such a structure, the relative positional relationship of a 1st reflective surface and a 2nd reflective surface is always maintained constant. That is, since the first reflecting surface and the second reflecting surface are always integral, the displacements generated in both are always the same. For this reason, even if the transparent body is displaced, the average value of the first stripe interval and the second stripe interval hardly changes. As a result, when the distance is calculated based on the average value, the influence of the displacement of the first reflecting surface or the like can be almost eliminated, and the distance measurement accuracy can be further improved.

  In the optical measuring device according to the present invention, all the reflected light that reaches the first reflecting surface and the first light receiving surface passes through one point between the measured point and the first reflecting surface. As described above, it is preferable to further include a condensing means for condensing the reflected light.

  In many cases, the distance from the first light receiving surface to the point to be measured cannot be freely set due to constraints such as the environment in which the object and the optical measuring device are arranged. For example, when measuring the distance to an object placed in a vacuum chamber, the optical measuring device cannot be placed inside the vacuum chamber, so the distance from the first light receiving surface to the point to be measured is somewhat Need to take longer.

  By the way, as already described, the first stripe interval is determined by the distance between the first light receiving surface and the measurement point, and the longer the distance between the first reflection surface and the measurement point, the wider the first stripe interval. Become.

  For this reason, depending on the restriction on the distance from the first light receiving surface to the measurement point, the first fringe interval becomes too large compared to the size of the first light receiving surface (because the distance cannot be shortened). It may be difficult to accurately measure the stripe spacing. Conversely, the first fringe interval becomes too small compared to the measurement resolution of the first interference fringe measuring means (because the distance cannot be increased), and it is difficult to accurately measure the first fringe interval. There is also a case.

  As described above, there are cases where it is not possible to achieve both the arrangement of the object and the optical measuring device so as to satisfy the constraints of the environment and the like, and the measurement of the distance from the first light receiving surface to the measurement point with a desired accuracy. Can occur. In addition, since the range of distance that can be measured is fixed due to environmental constraints, it becomes impossible to measure the distance when the distance from the first light receiving surface to the point to be measured varies greatly. May occur.

  In order to solve this problem, the preferable aspect further includes a light collecting means for collecting the reflected light. In the condensing means, all the reflected light that reaches the first reflecting surface and the first light receiving surface passes through one point (hereinafter also referred to as “condensing point”) between the measurement point and the first reflecting surface. As described above, the reflected light is collected.

  In the case of such a configuration, the position of the condensing point is the position of the point light source that generates interference fringes on the first light receiving surface. That is, the distance to the point light source that is directly calculated based on the first fringe interval is the distance from the first light receiving surface to the condensing point. Therefore, the distance from the first light receiving surface to the measurement point can be calculated by adding the distance from the light collection point to the measurement point to the distance from the first light reception surface to the light collection point. Note that the distance from the condensing point to the point to be measured is calculated based on the focal length of the condensing unit that is, for example, a convex lens, and the distance from the condensing unit to the condensing point.

  The distance from the condensing point to the point to be measured can be freely set depending on how the condensing means is selected. Thereby, the magnitude | size of a 1st fringe space | interval can be made appropriate, without changing the distance from the surface containing a 1st light-receiving surface to a to-be-measured point. In other words, it is possible to achieve both the arrangement of the object and the optical measuring device so as to satisfy the constraints such as the environment and the measurement of the distance from the first light receiving surface to the measurement point with a desired accuracy. .

  Further, for example, by changing the vertical magnification of the condensing unit that is a convex lens, the relationship between the variation in the distance from the condensing unit to the measurement point and the positional variation of the condensing point can be changed. Such a relationship can also be referred to as a relationship between a variation in the distance from the first light receiving surface to the measurement point and a variation in the first fringe interval. Increasing the vertical magnification improves the distance measurement resolution. If the vertical magnification is reduced, the distance measurement resolution is lowered, but the range of measurable distances is widened. By utilizing this, even if the distance from the first light receiving surface to the point to be measured varies greatly, the entire variation range can be accommodated in the measurable range.

  In the optical measuring device according to the present invention, all the reflected light reaching the first reflecting surface, the second reflecting surface, the first light receiving surface, and the second light receiving surface are It is also preferable to further include a condensing unit that condenses the reflected light so as to pass through one point between the first reflecting surface and the first reflecting surface.

  By adopting such an aspect, even in the optical measuring apparatus having the second reflecting surface and the second light receiving surface, the distance from the first light receiving surface (and the second light receiving surface) to the measurement point is set. The size of the first stripe interval and the second stripe interval can be made appropriate without being changed. In other words, the object and the optical measurement device are arranged so as to satisfy the constraints of the environment, and the distance from the first light receiving surface (and the second light receiving surface) to the measurement point is measured with a desired accuracy. Can be made compatible.

  According to the present invention, there is provided an optical measuring device capable of accurately measuring a distance to an object while having a simple configuration.

It is a figure which shows typically the structure of the optical measuring device which concerns on 1st embodiment of this invention. It is a figure for demonstrating the method to measure the distance to an object with the optical measuring device shown in FIG. It is a figure which shows typically the optical measuring device which concerns on 2nd embodiment of this invention. It is a perspective view which shows the glass rod with which the optical measuring device shown in FIG. 3 is provided. It is a figure for demonstrating the method to measure the distance to an object with the optical measuring device shown in FIG. It is a figure for demonstrating the method to measure the distance to an object with the optical measuring device shown in FIG. It is a figure which shows typically the optical measuring device which concerns on 3rd embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same constituent elements in the drawings will be denoted by the same reference numerals as much as possible, and redundant description will be omitted.

  The optical measuring device 1 according to the present embodiment is a device that irradiates and reflects light on an object M and measures the distance to the object M based on the reflected light. FIG. 1A schematically shows the configuration of the optical measuring device 1. As shown in FIG. 1A, the optical measuring device 1 includes a light source 10, a condenser lens 11, a CCD image sensor 20, and a mirror 30. Although the optical measuring device 1 further includes a casing for housing these, the illustration thereof is omitted in FIG.

  The light source 10 is a device that emits light of a single wavelength (monochromatic light) and irradiates the light toward the surface of the object M. As the light source 10, various devices that emit coherent light, such as a semiconductor laser device and a helium neon laser, can be used.

  The condenser lens 11 is a convex lens, and condenses the light emitted from the light source 10 at one point on the surface of the object M (hereinafter referred to as “measurement point”). The condensing lens 11 is not necessarily a convex lens, and various optical elements that condense the light emitted from the light source 10 onto the measurement point A can be used.

  The condensing lens 11 corresponds to the “condensing means” of the present invention. In carrying out the present invention, it is only necessary to irradiate one point of the object M with monochromatic light, and it is not always necessary to provide the light collecting means and the light source as separate bodies. For example, if the light source 10 is a semiconductor laser device and laser light that goes straight toward one point is emitted from the light source 10, the condensing lens 11 does not need to be arranged. In this case, it can be said that the semiconductor laser device is an integration of the “light source” and the “condensing means” of the present invention.

  The CCD image sensor 20 has a flat light receiving surface SS, and is arranged with the light receiving surface SS facing the measurement point A. A part of the light (reflected light) emitted from the light source 10 and reaching the measurement point A and reflected (diffuse reflection) at the measurement point A directly reaches the light receiving surface SS of the CCD image sensor 20.

  Here, a straight line (virtual straight line) that is perpendicular to the plane including the light receiving surface SS and passes through the measurement point A is defined as an intermediate line LC for convenience of explanation. Although FIG. 1 shows an example of an arrangement in which the intermediate line LC and the light receiving surface SS intersect at the center of the light receiving surface SS, there may be an arrangement in which the intermediate line LC and the light receiving surface SS do not intersect. .

  The mirror 30 has a flat reflecting surface SR, and is arranged so that the reflecting surface SR is perpendicular to the light receiving surface SS of the CCD image sensor 20. The reflecting surface SR is arranged to be parallel to the intermediate line LC and to face the intermediate line LC. For this reason, after a part of the light (reflected light) emitted from the light source 10 and reaching the measurement point A and reflected (scattered) at the measurement point A is further reflected by the reflection surface SR of the mirror 30, It reaches the light receiving surface SS of the CCD image sensor 20.

  Thus, the light directly reaching from the measurement point A and the light reaching from the reflecting surface SR of the mirror 30 are irradiated onto the light receiving surface SS of the CCD image sensor 20 in an overlapping manner. These are all the light emitted from the light source 10, but the optical path lengths of the optical paths that follow before reaching the light receiving surface SS are different from each other. For this reason, interference fringes are generated on the light receiving surface SS due to the optical path difference. The fringe interval (pitch) of the interference fringes has a size proportional to the distance from the light receiving surface SS to the measurement point A.

  An image processing device (not shown) is connected to the CCD image sensor 20. The image processing apparatus is a computer system composed of a CPU, a RAM, and the like, and analyzes the image data output from the CCD image sensor 20 (for example, Fourier transform), thereby generating interference fringes formed on the light receiving surface SS. The fringe interval is calculated. Further, the image processing apparatus calculates the distance between the light receiving surface SS and the measured point A based on the calculated fringe interval, and outputs this to the outside as the distance to the object M. A specific method for calculating the distance between the light receiving surface SS and the measurement point A will be described later.

  In this embodiment, an example in which the CCD image sensor 20 is used as a sensor for acquiring interference fringes is shown, but a CMOS image sensor, a photodiode array, a linear image sensor, or the like is used instead of the CCD image sensor 20. May be. When using a linear image sensor, it is necessary to arrange the arrangement direction along the direction in which interference fringes are arranged.

  1A shows an example in which the optical path of light reaching the measurement point A from the light source 10 and the optical path of light reaching the light receiving surface SS from the measurement point A are completely separated. Embodiments of the present invention are not limited to this. For example, as shown in FIG. 1B, the half mirror 12 is arranged on the optical path of the light reaching the light receiving surface SS from the measurement point A, and light is emitted from the light source 10 toward the half mirror 12. It is good. In this case, the light emitted from the light source 10 is reflected by the half mirror 12 and applied to the point A to be measured. Further, part of the light reflected (scattered) at the measurement point A passes through the half mirror and reaches the light receiving surface SS.

  Further, in order to make the interference fringes formed on the light receiving surface SS clearer, on the optical path between the light source and the measured point A or on the optical path between the measured point A and the light receiving surface SS. A polarizing plate may be disposed.

  Next, a specific method for calculating the distance between the light receiving surface SS and the measured point A will be described with reference to FIG. FIG. 2 is a diagram for explaining a method of measuring the distance to the object M by the optical measuring device 1, and schematically shows the path of light reflected from the measurement point A of the object M. .

  In FIG. 2, the direction from the measurement point A toward the light receiving surface SS along the intermediate line LC is the x direction. Further, the direction perpendicular to the x direction and going from the measurement point A to the surface including the reflection surface SR is defined as the y direction. Further, the origin of the perpendicular line drawn from the point A to be measured to the surface including the reflection surface SR is defined as the origin O, and the x coordinate axis is set along the x direction from the origin O. Similarly, the y coordinate axis is set along the y direction from the origin O.

FIG. 2 particularly shows an optical path of light that reaches a point B that is one point on the light receiving surface SS among the reflected light that directly reaches the light receiving surface SS from the point A to be measured. If the distance from the surface including the light receiving surface SS to the measurement point A is d and the distance from the surface including the reflection surface SR to the measurement point A is W / 2, the optical path length La of this optical path and the point B The relationship with the y coordinate (y) is expressed by the following equation (1).

Further, the light that reaches the reflection surface SR of the mirror 30 from the measurement point A, is further reflected by the reflection surface SR, and then reaches the point B on the light receiving surface SS will be considered. The optical path length Lb of the optical path followed by such light is emitted from a point A1 (0, W / 2) that is symmetric with respect to the measured point A (0, -W / 2) with respect to the plane including the reflecting surface SR. It is the same as the optical path length of the optical path that reaches the point B (d, y) by following a typical optical path. Accordingly, the relationship between the optical path length Lb and the y coordinate (y) of the point B is expressed by the following equation (2).

Therefore, the optical path difference between the two lights reaching point B is

It becomes.

Light interference occurs at point B due to the optical path difference. As described above, since the optical path difference is a function of y, the brightness of the interference fringes in the portion (point B) varies depending on the value of y. If the wavelength of the light emitted from the light source 10 is λ, the fringe spacing p1 of the interference fringes generated on the light receiving surface SS due to the optical path difference is

It becomes. Here, both of the optical path lengths La and Lb are sufficiently larger than W and can be approximated to be equal to d. Therefore, the following equation (5) is obtained by modifying the above equation (4).

  Thus, if the fringe spacing p1 (value calculated by the image processing device) of the interference fringes generated on the light receiving surface SS is known, the distance (d) from the surface including the light receiving surface SS to the point A to be measured is described in more detail. Is assumed to be the length from the intersection of the normal vector and the surface including the light receiving surface SS to the measured point A, assuming that the normal vector with respect to the surface including the light receiving surface SS passes through the measured point A. The distance (d) from the surface including the light receiving surface SS to the point A to be measured can be calculated by Expression (5).

  As described above, the optical measurement device 1 according to the present embodiment emits light from the light source 10 with a simple configuration including the reflection surface SR (first reflection surface) and the light reception surface SS (first light reception surface). The optical path difference and interference fringes of the generated light are generated. The distance to the object M, that is, the distance from the plane including the light receiving surface SS to the measurement point A is accurately measured based on the fringe spacing of the interference fringes.

  By the way, as apparent from the above equation (5), the calculated value of the distance (d) from the surface including the light receiving surface SS to the measurement point A may change depending on the value of W. There is. For example, mistakes during assembly of the optical measuring device or impact due to external force are applied to the optical measuring device 1, and the position of the optical lens system is displaced from the original design position. For example, the reflecting surface SR is displaced in the y direction. If this happens (when W becomes larger than the initial value), the relationship between the distance calculated based on the fringe spacing of the interference fringe and the actual distance will change. And the fringe spacing p1 change. As a result, the distance (d) from the plane including the light receiving surface SS to the measurement point A cannot be accurately calculated.

  Therefore, as an embodiment capable of solving such a problem, an optical measuring device 1a according to a second embodiment of the present invention will be described below. FIG. 3 is a diagram schematically showing the configuration of the optical measuring device 1a, and schematically showing the path of light reflected from the measurement point A of the object M. As shown in FIG. As apparent from the comparison between FIG. 2 and FIG. 3, the optical measurement apparatus 1a includes a CCD image sensor 20a having a pair of light receiving surfaces (first light receiving surface SS1, second light receiving surface SS2), and The optical measurement apparatus 1 is different from the optical measurement apparatus 1 in that it includes a pair of mirrors (first mirror 31 and second mirror 32), and the other configuration is the same as that of the optical measurement apparatus 1.

  As shown in FIG. 3, the CCD image sensor 20a of the optical measuring device 1a has a first light receiving surface SS1 and a second light receiving surface SS2 which are a pair of light receiving surfaces. These are all flat light-receiving surfaces and are arranged side by side in the y direction on the same plane. The intermediate line LC intersects with the CCD image sensor 20a at the boundary between the first light receiving surface SS1 and the second light receiving surface SS2. The first light receiving surface SS1 is arranged on the + y direction side (lower side in FIG. 3) from the intermediate line LC, and the second light receiving surface SS2 is on the −y direction side (upper side in FIG. 3) from the intermediate line LC. Has been placed.

  The CCD image sensor 20a is arranged with its light receiving surfaces (the first light receiving surface SS1 and the second light receiving surface SS2) facing the measurement point A. A part of the light (reflected light) emitted from the light source 10 and reaching the measurement point A and reflected (scattered) at the measurement point A directly reaches the first light receiving surface SS1, and a part of the light reaches the first light receiving surface SS1. Directly reaches the second light receiving surface SS2.

  The first mirror 31 has a flat reflecting surface (first reflecting surface SR1), and is arranged so that the first reflecting surface SR1 is perpendicular to the first light receiving surface SS1 of the CCD image sensor 20a. Yes. The first reflecting surface SR1 is parallel to the intermediate line LC, and is arranged to face the intermediate line LC on the + y direction side of the intermediate line LC. For this reason, a part of the light (reflected light) emitted from the light source 10 and reaching the measurement point A and reflected (scattered) at the measurement point A is further reflected by the first reflection surface SR1 of the first mirror 31. After that, it reaches the first light receiving surface SS1 of the CCD image sensor 20a.

  The second mirror 32 has a flat reflecting surface (second reflecting surface SR2), and is disposed so that the second reflecting surface SR2 is perpendicular to the second light receiving surface SS2 of the CCD image sensor 20a. Yes. The second reflecting surface SR2 is parallel to the intermediate line LC and is disposed to face the intermediate line LC on the −y direction side of the intermediate line LC. For this reason, a part of the light (reflected light) emitted from the light source 10 and reaching the measurement point A and reflected (scattered) at the measurement point A is further reflected by the second reflection surface SR2 of the second mirror 32. After that, it reaches the second light receiving surface SS2 of the CCD image sensor 20a.

  In the state where the optical measuring device 1a is arranged so as to measure the distance to the measurement point A (state in FIG. 3), the distance from the first reflecting surface SR1 to the intermediate line LC is from the second reflecting surface SR2. It is equal to the distance to the intermediate line LC. In other words, the positions of the first mirror 31 and the second mirror 32 inside the optical measuring device 1a are determined so as to satisfy such a condition.

  The first mirror 31 and the second mirror 32 as described above may be provided with two mirrors that are separate from each other. However, in the present embodiment, two surfaces facing each other in one glass rod GL are used as the first mirror 31 and the second mirror 32, respectively.

  This will be described with reference to FIG. FIG. 4 is a perspective view showing the glass rod GL. The glass rod GL is a rectangular glass, and the end surface SF on one end side in the longitudinal direction is arranged toward the measurement point A of the object M. The CCD image sensor 20a is attached to the end surface SB on the other end side in the longitudinal direction with the first light receiving surface SS1 and the second light receiving surface SS2 in contact with each other. For this reason, the reflected light from the measurement point A enters from the end surface SF, passes through the inside of the glass rod GL, and reaches the first light receiving surface SS1 and the second light receiving surface SS2. The material of the glass rod GL is not limited to glass, and various materials that are transparent to the light emitted from the light source 10 can be used.

  As shown in FIG. 4, in the glass rod GL, two flat surfaces facing in the y direction are respectively a first reflecting surface SR1 (first mirror 31) and a second reflecting surface SR2 (second mirror 32). It has become. A part of the light incident on the inside of the glass rod GL from the end surface SF enters the first reflecting surface SR1 and is totally reflected, and then reaches the first light receiving surface SS1. Similarly, a part of the light incident on the inside of the glass rod GL from the end surface SF is incident on the second reflecting surface SR2 and totally reflected, and then reaches the second light receiving surface SS2. In addition, the thin film by metal vapor deposition may be formed in each surface used as the 1st reflective surface SR1 and the 2nd reflective surface SR2 among the surfaces of the glass rod GL.

  In addition, since the 1st mirror 31 and the 2nd mirror 32 in this embodiment are as above (one surface of the glass rod GL), the thickness cannot be considered. However, in FIG. 3 and the like, for convenience of explanation, each is depicted as a plate-like mirror having a certain thickness. Moreover, in FIG. 3 etc., illustration of parts other than the 1st mirror 31 and the 2nd mirror 32 among the glass rods GL is abbreviate | omitted.

  As described above, in the present embodiment, the first mirror 31 and the second mirror 32 are not separate from each other but are integrated with each other. Therefore, the relative positional relationship between the first mirror 31 and the second mirror 32 is always constant. Maintained constant. That is, even if the glass rod GL is displaced by the impact of an external force, the displacements generated on the first reflecting surface SR1 and the second reflecting surface SR2 are always the same.

  Returning to FIG. 3, the description will be continued. In FIG. 3, the direction from the measurement point A toward the surface including the first light receiving surface SS1 along the intermediate line LC is the x direction. Further, the direction perpendicular to the x direction and going from the measurement point A toward the surface including the first reflecting surface SR1 is defined as the y direction. In addition, the origin of the perpendicular line that is dropped from the measurement point A is the origin O with respect to the surface including the first reflecting surface SR1 at the time before displacement. An x coordinate axis is set from the origin O along the x direction. Similarly, the y coordinate axis is set along the y direction from the origin O. In the subsequent drawings, the x coordinate axis, the y coordinate axis, and the origin O are set in the same manner as described above.

  As already described, the first light receiving surface SS1 of the CCD image sensor 20a is irradiated with the light directly reaching from the measurement point A and the light reaching from the first reflecting surface SR1 of the first mirror 31 in an overlapping manner. The These are all the light emitted from the light source 10, but the optical path lengths of the optical paths that follow until reaching the first light receiving surface SS1 are different from each other. For this reason, interference fringes are generated on the first light receiving surface SS1 due to the optical path difference. The fringe interval p1 of the interference fringes is proportional to the distance from the first light receiving surface SS1 to the measurement point A.

  Similarly, the light directly reaching from the measurement point A and the light reaching from the second reflecting surface SR2 of the second mirror 32 are irradiated on the second light receiving surface SS2 of the CCD image sensor 20a in an overlapping manner. These are all the light emitted from the light source 10, but the optical path lengths of the optical paths that follow before reaching the second light receiving surface SS2 are different from each other. For this reason, interference fringes are generated on the second light receiving surface SS2 due to the optical path difference. The fringe interval p2 of the interference fringes has a size proportional to the distance from the second light receiving surface SS2 to the measurement point A.

  Here, the first light receiving surface SS1 and the second light receiving surface SS2 are arranged on the same plane, and the distance from the first reflecting surface SR1 to the intermediate line LC is from the second reflecting surface SR2 to the intermediate line LC. As apparent from the fact that it is equal to this distance, the stripe interval p1 and the stripe interval p2 are equal to each other (see equation (5)).

  However, for example, when an impact due to an external force is applied to the optical measuring device 1 and the reflecting surface SR is displaced from the state shown in FIG. 3, the fringe spacing p1 and the fringe spacing p2 change, respectively. As will be described, the sizes are different from each other.

  As an example of such displacement, an example in which the glass rod GL is displaced by Δy in the y direction will be described. That is, an example will be described in which the first reflecting surface SR1 is translated in the y direction by Δy, and the second reflecting surface SR2 is also translated in the y direction by Δy. At this time, the position of the object M and the position of the CCD image sensor 20a are not changed.

  FIG. 5 is a diagram for explaining a method of measuring the distance to the object M by the optical measuring device 1a. FIG. 5 schematically shows the path of light reaching the first light receiving surface SS1 when the glass rod GL is displaced by Δy as described above. In the figure, the second mirror 32 is not shown. Further, the second reflecting surface SR2 of the CCD image sensor 20a is not shown.

FIG. 5 particularly shows an optical path of light reaching point B, which is one point on the first light receiving surface SS1, out of reflected light directly reaching the first light receiving surface SS1 from the point A to be measured. As in the case described with reference to FIG. 2, the distance from the surface including the first light receiving surface SS1 to the measurement point A is d, and the measurement is performed from the surface including the first reflection surface SR1 at the time before the displacement. If the distance to the point A is W / 2, the relationship between the optical path length La1 of this optical path and the y coordinate (y) of the point B is expressed by the following equation (6).

Next, light that reaches the first reflecting surface SR1 of the first mirror 31 from the measurement point A, is further reflected by the first reflecting surface SR1, and then reaches the first light receiving surface SS1 will be considered. The optical path length Lb1 of the optical path followed by such light is the optical path length of the optical path that is emitted from the point A2 (0, W / 2 + 2Δy) and reaches the point B (d, y) by following the linear optical path. Are the same. Accordingly, the relationship between the optical path length Lb1 and the y coordinate (y) of the point B is expressed by the following equation (7).

Therefore, the optical path difference between the two lights reaching point B is

It becomes.

Light interference occurs at point B due to the optical path difference. As described above, since the optical path difference is a function of y, the brightness of the interference fringes in the portion (point B) varies depending on the value of y. If the wavelength of the light emitted from the light source 10 is λ, the fringe spacing p1 of the interference fringes generated on the first light receiving surface SS1 by the optical path difference is

It becomes. However, in deriving the above equation (9), Δy is very small compared to y, and that optical path lengths La1 and Lb1 are both sufficiently larger than W and can be regarded as being equal to d, respectively. We are considering.

Assuming that the fringe spacing of the interference fringes generated on the second light receiving surface SS2 is p2, p2 can also be obtained as follows by the same procedure as described above.

Here, if the average value of p1 and p2 is p,

However, considering that Δy is a minute amount,

It becomes.

  As described above, when the first reflecting surface SR1 and the second reflecting surface SR2 are respectively displaced in the y direction, the sizes of the stripe intervals p1 and p2 are changed by the displacement. However, the change in the average value p of p1 and p2 is negligible. Based on the average value p, the distance (d) from the surface including the first light receiving surface SS1 to the measured point A can be calculated by the same equation (12) as the equation (5).

  Next, an example in which the glass rod GL rotates slightly will be described with reference to FIG. That is, an example will be described in which the first reflecting surface SR1 and the second reflecting surface SR2 are slightly rotated with one axis perpendicular to both the x coordinate axis and the y coordinate axis as a rotation axis. FIG. 6 shows a state in which the glass rod GL is rotated by an angle θ around a rotation axis that passes through the point C (x1, 0) and is perpendicular to both the x coordinate axis and the y coordinate axis. The direction of rotation is counterclockwise in FIG. That is, the rotation direction is such that the end on the object M side of the first reflecting surface SR1 is displaced in the + y direction and the end on the CCD image sensor 20a is displaced in the −y direction. On the other hand, the position of the object M and the position of the CCD image sensor 20a are not changed before and after the glass rod GL is displaced.

  As in the case of FIG. 5, the second mirror 32 is not shown in FIG. Further, the second reflecting surface SR2 of the CCD image sensor 20a is not shown. FIG. 6 particularly shows an optical path of light that reaches point B, which is one point on first light receiving surface SS1, out of reflected light that directly reaches first light receiving surface SS1 from point A to be measured. Point B is a point where the light that reaches point C from point A to be measured reaches first light receiving surface SS1 after being reflected by first reflecting surface SR1.

If the y coordinate of the point B is expressed as y, the optical path length La1 of the optical path followed by the reflected light that directly reaches the first light receiving surface SS1 from the measured point A is expressed by the following equation (13).

Next, light that reaches the first reflecting surface SR1 of the first mirror 31 from the measurement point A, is further reflected by the first reflecting surface SR1, and then reaches the point B on the first light receiving surface SS1 will be considered. The optical path length Lb1 of the optical path followed by such light is the same as the optical path length that is emitted from the point A3 in FIG. 6 and reaches the point B (d, y) by following the linear optical path. The point A3 is a point that is symmetric with respect to the measurement point A (0, −W / 2) with respect to the surface including the first light receiving surface SS1 after displacement, and the coordinates thereof are (Wtan θ + ² × 1 tan ² θ, W / 2 + ² × 1 tan θ). It is.

Therefore, if the optical path length Lb1 which is the distance between the point A3 and the point B (d, y) is obtained and this and the equation (13) are substituted into the following equation (14), the interference generated on the first light receiving surface SS1. The stripe interval p1 of the stripe is obtained.

In consideration of the fact that θ is very small, p1 is calculated as follows if approximation such as tan θ = θ is performed.

Assuming that the fringe spacing of the interference fringes generated on the second light receiving surface SS2 is p2, p2 can also be obtained as follows by the same procedure as described above.

Here, if the average value of p1 and p2 is p,

However, considering that θ is a minute amount,

It becomes.

  As described above, when the first reflecting surface SR1 and the second reflecting surface SR2 are slightly rotated, the sizes of the stripe intervals p1 and p2 are changed by the rotation. However, the change in the average value p of p1 and p2 is negligible. Based on the average value p, the distance (d) from the surface including the first light receiving surface SS1 to the measurement point A can be calculated by the same equation (18) as the equation (5).

  The case where the glass rod GL is displaced so as to move in parallel and the case where it is displaced so as to rotate have been described with reference to FIGS. 5 and 6. As is clear from the above description, in any case, if the displacements of the first reflection surface SR1 and the second reflection surface SR2 are similar to each other, the change in the stripe interval p1 and the change in the stripe interval p2 Changes are opposite to each other. That is, when one increases, the other decreases. Therefore, the change in the average value p of p1 and p2 is negligible, and the distance (d) from the surface including the first light receiving surface SS1 to the measurement point A is calculated based on the average value p. be able to.

  This is true not only when the parallel movement or rotation of the glass rod GL occurs individually as described above, but also when it occurs in combination. In addition, as long as the displacements of the first reflecting surface SR1 and the second reflecting surface SR2 are similar to each other, this holds even when a complicated displacement other than the above occurs.

  In the present embodiment, in order to make the displacement of the first reflecting surface SR1 and the displacement of the second reflecting surface SR2 similar to each other, they are two surfaces facing the glass rod GL. However, the embodiment of the present invention is not limited to this. For example, the first mirror 31 and the second mirror 32 may be configured as separate bodies, and some means for fixing the relative displacement between them (for example, a column interposed between the two) may be provided.

  In the present embodiment, the CCD image sensor 20a is arranged so that the normal direction of the first light receiving surface SS1 (and the second light receiving surface SS2) coincides with the longitudinal direction of the glass rod GL. As an embodiment of the present invention, in addition to this aspect, the CCD image sensor 20a may be arranged so that the normal direction of the first light receiving surface SS1 and the like is slightly inclined with respect to the longitudinal direction of the glass rod GL. . With such an arrangement, even when multiple reflections in the cover glass provided in the CCD image sensor 20a or multiple reflections between the cover glass and the glass rod GL occur, interference fringes are generated. The influence of the multiple reflection or the like on the measurement can be suppressed.

  When the CCD image sensor 20a is thus inclined, the stripe intervals p1 and p2 change due to the influence of the inclination. However, since the tilt angle of the CCD image sensor 20a is known, the equation (18) for calculating d based on the fringe intervals p1 and p2 may be appropriately corrected and used.

  Moreover, the optical measuring device 1a according to the present embodiment can measure the thickness of the thin film in addition to measuring the distance to the surface of the object as described above. In this case, the interference fringes due to the reflected light reflected from the surface of the thin film and the interference fringes due to the reflected light reflected from the back surface of the thin film are caused to overlap the first light receiving surface SS1 and the second light receiving surface SS2, respectively.

  The fringe spacing of the interference fringes generated by overlapping the first light receiving surface SS1 and the like can be calculated by arithmetic processing (for example, Fourier transform) performed by the image processing apparatus. Therefore, the distance from the surface including the first light receiving surface SS1 to the surface of the thin film and the distance from the surface including the first light receiving surface SS1 to the back surface of the thin film are simultaneously measured, and the thickness of the thin film which is the difference between the two Can be calculated.

  Next, an optical measuring device 1b according to a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a diagram schematically showing the optical measuring device 1b, and schematically showing the path of light reflected from the measurement point A of the object M. The optical measuring device 1b is different from the optical measuring device 1a in that the condensing lens 40 is disposed between the object M and the first mirror 31, and other configurations are the same as those of the optical measuring device 1a. It is the same. However, the illustration of the second mirror 32 is omitted in FIG. Further, the second reflecting surface SR2 of the CCD image sensor 20a is not shown.

  As shown in Expression (12), Expression (18), and the like, the sizes of the stripe intervals p1 and p2 (and the average value p thereof) obtained as the output of the CCD image sensor 20a include the first light receiving surface SS1. The value is proportional to the distance (d) from the surface to the point A to be measured.

  For this reason, when it is going to measure distance with the optical measuring device 1a which concerns on 2nd embodiment, when d is large, the stripe space | interval p1 will become too large compared with the magnitude | size of 1st light-receiving surface SS1, and a stripe It may be difficult to accurately measure the interval p1. Conversely, when d is small, the fringe interval p1 becomes too small compared to the measurement resolution of the CCD image sensor 20a, and it may be difficult to accurately measure the fringe interval p1.

  However, there are many cases where the distance from the first light receiving surface SS1 to the point A to be measured cannot be freely set due to restrictions on the environment where the object M and the optical measuring device 1a are arranged. For example, when measuring the distance to the object M arranged in the vacuum chamber, the optical measuring device 1a cannot be arranged inside the vacuum chamber, and therefore from the first light receiving surface SS1 to the measurement point A. It is necessary to take a certain distance.

  As a result, the object M and the optical measuring device 1a are arranged so as to satisfy the constraints such as the environment, and the distance from the first light receiving surface SS1 to the measurement point A is measured with a desired accuracy. There may be cases where it is impossible. In addition, since the range of the distance that can be measured is fixed due to constraints such as the environment, when the distance from the first light receiving surface SS1 to the point A to be measured varies greatly, it becomes impossible to measure the distance. It may also happen.

  Therefore, in the optical measuring device 1b according to the present embodiment, the above-described problem is solved by disposing the condenser lens 40 between the object M and the first mirror 31. Hereinafter, the effect of disposing the condenser lens 40 will be described.

  The condensing lens 40 is a thin single lens, and condenses all reflected light from the measurement point A toward the CCD image sensor 20a at one point (condensing point FP). The main surface of the condensing lens 40 is perpendicular to the intermediate line LC, and the condensing point FP is located on the intermediate line LC. All the reflected light that reaches the first reflecting surface SR1, the second reflecting surface SR2, the first light receiving surface SS1, and the second light receiving surface SS2 from the measurement point A passes through the condensing lens 40, and then the condensing point FP. Pass through.

  As is apparent from FIG. 7, in the configuration as described above, the position of the condensing point FP can be regarded as the position of the point light source that generates the interference fringes on the first light receiving surface SS1. Accordingly, the distance d1 between the surface including the first light receiving surface SS1 and the condensing point FP can be calculated by the same procedure as that when d is calculated by the equations (12) and (18).

  Further, the position of the condensing lens 40 in the optical measuring device 1b, that is, the distance between the surface including the first light receiving surface SS1 and the main surface of the condensing lens 40 is known. Therefore, the distance d2 between the condensing point FP and the main surface of the condensing lens 40 can be calculated by subtracting the distance d1 from the distance.

Further, since the focal length f of the condenser lens 40 is also known, the distance d3 between the main surface of the condenser lens 40 and the measurement point A can be calculated by the lens imaging formula shown below.

  The distance (d) from the surface including the first light receiving surface SS1 to the measurement point A can be easily obtained as the sum of d1, d2, and d3 calculated as described above.

  The distance (d2 + d3) from the condensing point FP to the point to be measured A can be freely set depending on how the condensing lens 40 is selected. In other words, the distance d1 between the surface including the first light receiving surface SS1 and the condensing point FP can be freely set.

  Thereby, the magnitude | size of the fringe space | interval p1 can be made appropriate, without changing the distance from the surface containing 1st light-receiving surface SS1 to the to-be-measured point A. In other words, the object M and the optical measuring device 1b are arranged so as to satisfy the constraints such as the environment, and the distance from the first light receiving surface SS1 to the measurement point A is measured with a desired accuracy. Can be made.

  Further, for example, by changing the vertical magnification of the condensing lens 40, the relationship between the variation in the distance d3 from the condensing lens 40 to the measurement point A and the positional variation of the condensing point FP (variation in the distance d2) is obtained. Can be changed. Such a relationship can also be referred to as a relationship between a variation in the distance d from the first light receiving surface SS1 to the measurement point A and a variation in the stripe interval p1. Increasing the vertical magnification improves the measurement resolution of the distance d. If the vertical magnification is reduced, the measurement resolution of the distance d decreases, but the range of the distance d that can be measured becomes wider. By utilizing this, even if the distance d from the first light receiving surface SS1 to the measurement point A varies greatly, the entire variation range can be accommodated in the measurable range.

  The condensing lens 40 is not necessarily a thin single lens, and various optical elements that condense the reflected light from the measurement point A onto the condensing point FP can be used. Further, it goes without saying that the condenser lens 40 as described above has the same effect even when it is arranged with respect to the optical measuring device 1 shown in FIG.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements included in each of the specific examples described above and their arrangement, materials, conditions, shapes, sizes, and the like are not limited to those illustrated, but can be changed as appropriate. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

  For example, the example in which the first light receiving surface SS1 and the second light receiving surface SS2 are the light receiving surfaces of one CCD image sensor 20a has been described. However, instead of such an aspect, two CCD image sensors are provided. Also good. In this case, the light receiving surface of one CCD image sensor may be used as the first light receiving surface SS1, and the light receiving surface of the other CCD image sensor may be used as the second light receiving surface SS2.

1, 1a, 1b: Optical measuring device 10: Light source 11: Condensing lens 12: Half mirror 20, 20a: CCD image sensor 30: Mirror 31: First mirror 32: Second mirror 40: Condensing lens A: Covered Measurement point FP: Condensing point GL: Glass rod LC: Intermediate line M: Object SB: End surface SF: End surface SR: Reflective surface SR1: First reflective surface SR2: Second reflective surface SS: Light receiving surface SS1: First light receiving surface SS2: Second light receiving surface θ: Angle

Claims (6)

An optical measuring device that irradiates and reflects light on an object and measures the distance to the object based on the reflected light,
A light source that generates light to irradiate an object;
A light condensing means disposed between the light source and the object, and condensing light from the light source on a point to be measured of the object;
A first light receiving surface which is a flat surface arranged so that a part of the reflected light from the measurement point directly enters;
A first reflecting surface disposed perpendicular to the first light receiving surface so as to further reflect a part of the reflected light and enter the first light receiving surface;
First interference fringe measuring means for measuring the fringe spacing of the interference fringes generated on the first light receiving surface,
An optical measurement apparatus that calculates a distance from a plane including the first light receiving surface to the measurement point based on a fringe interval measured by the first interference fringe measuring unit. A second light-receiving surface disposed in the same plane as the plane including the first light-receiving surface, the flat surface disposed so that a part of the reflected light is directly incident;
A second reflecting surface disposed perpendicular to the second light receiving surface so as to further reflect a part of the reflected light and enter the second light receiving surface;
A second interference fringe measuring means for measuring the fringe spacing of the interference fringes generated on the second light receiving surface;
When a straight line that is perpendicular to the plane including the first light receiving surface and passes through the measurement point is defined as an intermediate line,
The first light receiving surface and the second light receiving surface are arranged side by side so as to sandwich the intermediate line therebetween,
The first reflective surface and the second reflective surface are parallel to each other and are disposed so as to face each other with the intermediate line therebetween.
A plane including the first light receiving surface and the second light receiving surface based on the average value of the fringe interval measured by the first interference fringe measuring unit and the fringe interval measured by the second interference fringe measuring unit. The optical measurement apparatus according to claim 1, wherein a distance from a point to be measured is calculated.   The optical measurement apparatus according to claim 2, wherein the first reflection surface and the second reflection surface are disposed at positions where the distances from the first reflection surface and the intermediate line are equal to each other. It is made of a material transparent to the light generated from the light source, and includes a transparent body arranged so that the reflected light passes through the inside thereof.
4. The optical measurement device according to claim 2, wherein each of the first reflection surface and the second reflection surface is a flat surface formed on a surface of the transparent body. 5.   Condensation for condensing the reflected light so that all of the reflected light reaching the first reflecting surface and the first light receiving surface passes through one point between the measured point and the first reflecting surface. The optical measuring device according to claim 1, further comprising means.   All of the reflected light that reaches the first reflecting surface, the second reflecting surface, the first light receiving surface, and the second light receiving surface passes through one point between the measured point and the first reflecting surface. The optical measuring device according to any one of claims 2 to 4, further comprising condensing means for condensing the reflected light.