JP6269334B2 - Multipoint distance measuring device and shape measuring device - Google Patents

Description

  The present invention relates to a multipoint distance measuring device that measures distances to a plurality of points on a measurement object, and a shape measuring device including the multipoint distance measuring device.

  As a measuring instrument that measures the surface shape of the measurement object, a shape that measures the surface shape of the measurement object by measuring the distance to multiple points on the measurement object and obtaining the relative positional relationship of these points Measuring devices are well known.

  For example, in Patent Document 1, a He-Ne laser is scanned with respect to a microlens array disposed at a position facing a measurement object, and the reflection of the He-Ne laser converged on the measurement object for each microlens. A method is disclosed in which the relative positions of a plurality of points are measured by detecting light with a two-divided photodetector and comparing the focus positions.

JP-A-10-300420

  By the way, in the measurement method described in Patent Document 1, the He-Ne laser is scanned with respect to the microlens array, that is, the measurement object. As the measurement object becomes larger, the scanning region and the scanning of the He-Ne laser are increased. Since time increases, there exists a problem that shape measurement takes time. For this reason, the He-Ne laser is divided into a plurality of light beams, each light beam is irradiated toward a plurality of points of the measurement object, and the surface shape is measured based on the result of detecting the reflected light from the plurality of points. Is preferred. However, if the level difference (unevenness or undulation) on the surface of the measurement object increases, when the reflected light from a plurality of points is detected, the detected reflected light is reflected from which point. It may not be possible to accurately determine, which may cause a problem in measurement accuracy. In addition, when the light beam obtained by dividing the He-Ne laser into a plurality of points is irradiated toward a plurality of points on the measurement object, it is difficult to select and detect only the regular reflection light of the light beam at each of the plurality of points. Therefore, a problem occurs in measurement accuracy.

  The present invention has been made in view of such circumstances, and measures the distance to a plurality of points on the measurement object with high accuracy and in a short time regardless of the shape of the measurement object (such as a step on the surface). It is an object of the present invention to provide a multipoint distance measuring device that can be used, and a shape measuring device including the multipoint distance measuring device.

  A multipoint distance measuring device for achieving the object of the present invention generates a special light that is a light having a predetermined repetition frequency from a light source that emits a broad spectrum and a broad spectrum that is emitted from the light source. Outgoing Fabry-Perot etalon, special light splitting the special light emitted from Fabry-Perot etalon into reference light and ranging light, and ranging light divided by special light splitting part A distance measuring light splitting unit that splits the light into a plurality of light beams, and a plurality of light beams divided by the distance measuring light splitting unit are respectively emitted toward a plurality of points of the measurement object and are regularly reflected at a plurality of points. Detecting light interference signals of a plurality of light incident / exiting portions into which the incident light beams are incident, a reference light divided by the special light dividing portion, and a plurality of light beams incident on the plurality of light incident / exiting portions, respectively. With light detector A distance calculation unit that calculates distances from a plurality of light incident / exit units to each of a plurality of points based on the detection result of the light detection unit, and a pulse interval of special light corresponding to the repetition frequency is set to D, and an arbitrary When the natural number is n, the optical path lengths of the light beams in the plurality of light incident / exit portions are sequentially increased by n · D, and the direction parallel to the light beams incident / exited from the plurality of light incident / exit portions is defined as the incident / exit direction. The Fabry-Perot etalon satisfies D> G, where G is the maximum value of the positional deviation amount in the incident / exit direction of two adjacent points among the plurality of points.

  According to the present invention, even when light beams are simultaneously emitted from a plurality of light incident / exit parts to a plurality of points of the measurement object, the specularly reflected light of each light beam is reflected at any of the plurality of points of the measurement object. Whether it is light can be easily identified. Thereby, multipoint measurement can be performed by one scan. Further, by using the distance measuring light generated by the Fabry-Perot etalon, only the regular reflection light of the light beam at each of a plurality of points can be selected and made incident on a plurality of light incident / exit portions, and the SN ratio A good interference fringe pattern can be generated. In addition, since only specularly reflected light can be incident on a plurality of light incident / exit portions, the influence of the reflectance at a plurality of points of the measurement object does not matter, and even when the optical paths of the respective light beams overlap, The distance to the point can be measured. As a result, the distance to a plurality of points of the measurement object can be measured at low cost with high accuracy and in a short time.

  In the multipoint distance measuring device according to another aspect of the present invention, the Fabry-Perot etalon can be exchanged according to the value of G. Thereby, multipoint distance measurement of a surface shape with a large level difference can be performed.

  In the multipoint distance measuring apparatus according to another aspect of the present invention, the light incident / exit positions of the light beams in the plurality of light incident / exit portions are the same position in the incident / exit direction. Thereby, it is possible to easily identify at which point among the plurality of points of the measurement object the specularly reflected light of each light beam is reflected.

  In the multipoint distance measuring apparatus according to another aspect of the present invention, the plurality of light incident / exit sections are one-dimensionally arranged in a direction perpendicular to the incident / exit direction. Thereby, based on the measurement result of the distance to a plurality of points, the one-dimensional surface shape of the measurement object can be measured.

  In the multipoint distance measuring apparatus according to another aspect of the present invention, the plurality of light incident / exit portions are two-dimensionally arranged in a plane perpendicular to the incident / exit direction. Thereby, based on the measurement result of the distance to a plurality of points, the two-dimensional surface shape of the measurement object can be measured.

  In the multipoint distance measuring device according to another aspect of the present invention, the plurality of light incident / exit portions are a plurality of optical fiber cables having different lengths. Thereby, it is possible to easily identify at which point among the plurality of points of the measurement object the specularly reflected light of each light beam is reflected.

  In the multipoint distance measuring device according to another aspect of the present invention, the distance calculation unit includes a first process for performing a square process on the optical interference signal, and a first process for performing a low-pass filter process on the optical interference signal subjected to the square process. 2, a third process for performing a differentiation process on the optical interference signal subjected to the low-pass filter process, and a fourth process for generating a trigger signal at the zero crossing position of the optical interference signal subjected to the differentiation process. And a fifth process for detecting the peak position of the optical interference signal based on the trigger signal generated in the fourth process, and a sixth process for calculating the distance based on the peak position detected in the fifth process. And execute. Thereby, for example, the distance to a plurality of points of the measurement object can be measured with higher accuracy.

  A shape measuring apparatus for achieving the object of the present invention includes the multipoint distance measuring apparatus described above and a shape calculating unit that calculates the surface shape of the measurement object based on the calculation result of the distance calculating unit.

  The multipoint distance measuring device and the shape measuring device of the present invention can measure the distance to a plurality of points on the measurement object with high accuracy and in a short time.

It is the schematic of the shape measuring apparatus of 1st Embodiment. It is explanatory drawing for demonstrating the special light which permeate | transmitted Fabry-Perot etalon. It is a front view of the opposing surface of a beam splitter. It is explanatory drawing for demonstrating regular reflection light. It is an enlarged view of an optical fiber cable and a collimator. (A) is explanatory drawing for demonstrating the delay (delay) of the light beam radiate | emitted from the collimator of each optical fiber cable, (B) demonstrates the delay of the regular reflection light which injects into the collimator of each optical fiber cable. It is explanatory drawing for doing. It is a flowchart which shows the flow of the shape measurement process in a shape measuring apparatus. It is explanatory drawing for demonstrating the principal part of the shape measuring apparatus of 2nd Embodiment. It is a front view of the opposing surface of the beam splitter of the shape measuring apparatus of 3rd Embodiment. It is a functional block diagram of the interference fringe pattern detection part of the shape measuring apparatus of 4th Embodiment. It is explanatory drawing for demonstrating the function of the interference fringe pattern detection part of the shape measuring apparatus of 5th Embodiment. It is the schematic of the shape measuring apparatus of 6th Embodiment.

[Shape Measuring Device of First Embodiment]
FIG. 1 is a schematic diagram of a shape measuring apparatus 10 that measures the surface shape of a measurement object 9. This shape measuring device 10 is a device that measures the surface shape of the measuring object 9 in a non-contact manner by measuring the distance to a plurality of points on the surface of the measuring object 9, and the multipoint distance of the present invention. This corresponds to a measuring device. The type of the measurement object 9 is not particularly limited, and examples thereof include a mold, a rotating body such as an automobile or an airplane engine, and the like.

  The shape measuring apparatus 10 is broadly divided into a broad spectrum light source (corresponding to the light source of the present invention) 19, a Fabry-Perot etalon (hereinafter simply referred to as etalon) 20, an optical amplifier 21, a splitter (of the present invention). (Corresponding to special light splitting section) 22, first optical path 23, second optical path 24, mixer 25, light detection section 26, interference fringe pattern detection section 27, distance calculation section 28, shape calculation section 29, and these sections are connected. An optical fiber cable 30 and a connector 31 for connecting the optical fiber cable 30 are provided.

  The broad spectrum light source 19 outputs a broad spectrum (also referred to as broadband light). As this broad spectrum light source 19, for example, a semiconductor laser is used. The semiconductor laser can emit a broad spectrum because the wavelength of the emitted light changes by changing the magnitude of the drive current. Note that various known light sources capable of emitting a broad spectrum such as a CW laser (Continuous wave laser) light source may be used as the broad spectrum light source 19. The intensity of the broad spectrum can be changed as appropriate.

  The etalon 20 has frequency selectivity utilizing interference caused by multiple reflections of parallel reflecting surfaces. The etalon 20 generates and outputs special light 34 that is light having a repetition frequency fr from the broad spectrum input from the broad spectrum light source 19.

  2A and 2B are explanatory diagrams for explaining the special light 34 output from the etalon 20. As shown in FIG. 2A, the special light 34 is composed of a large number of lights that are separated from each other by a frequency fr exactly in the frequency domain. As shown in FIG. 2B, the special light 34 appears as a very stable pulse train (a stable pulse train having a time interval T corresponding to the reciprocal of the repetition frequency fr) in the time domain. The pulse interval D of this pulse train is D = c / 2fr (c is the speed of light).

  Returning to FIG. 1, the optical amplifier 21 amplifies the special light 34 input from the etalon 20, and then outputs the special light 34 toward the splitter 22.

  The splitter 22 is connected to the optical amplifier 21 and the first optical path 23 and the second optical path 24. The splitter 22 divides the special light 34 input from the optical amplifier 21 into the reference light 35 and the distance measuring light 36, outputs the reference light 35 to the first optical path 23, and outputs the distance measuring light 36 to the second optical path. 24.

  A first collimator 38, a prism reflector 39, a corner reflector 40, a scanning stage 41, and a second collimator 42 are provided in the first optical path 23.

  The first collimator 38 emits the reference light 35 input from the splitter 22 as a parallel light beam toward the prism reflector 39.

  The prism reflector 39 reflects the reference light 35 input from the first collimator 38 toward the corner reflector 40 and reflects the reference light 35 incident from the corner reflector 40 toward the second collimator 42.

  The corner reflector 40 is disposed on the optical path of the reference light 35 reflected by the prism reflector 39. The corner reflector 40 reflects the reference light 35 incident from the prism reflector 39 toward the prism reflector 39 again.

  The scanning stage 41 is attached to the corner reflector 40. The scanning stage 41 reciprocates the corner reflector 40 along a direction parallel to the optical path of the reference light 35 reflected by the prism reflector 39. Specifically, the scanning stage 41 is reciprocated with a stroke amount slightly longer than the pulse interval D described above. Thereby, the amplitude of the optical interference signal of the reference light 35 and the ranging light 36 which will be described later can be temporally varied. By integrating the measurement data of the optical interference signal that varies with time, the accuracy of the measurement data can be increased. Instead of the scanning stage 41, for example, a PZT stage (voltage actuator) may be used.

  The second collimator 42 collects the reference light 35 incident from the prism reflector 39 and outputs it to the optical fiber cable 30. The second collimator 42 can be moved in a direction parallel to the optical path of the reference light 35 incident from the prism reflector 39 by a moving mechanism (not shown). Thereby, the optical path length of the reference light 35 in the first optical path 23 can be varied. The reference light 35 output from the second collimator 42 is input to the mixer 25.

  In the second optical path 24, a circulator 44, a beam splitter 46, and a plurality of optical fiber cables 47 are provided. The circulator 44 outputs the distance measuring light 36 input from the splitter 22 toward the beam splitter 46, and outputs the return light (regular reflection light 36 b described later) from the beam splitter 46 toward the mixer 25.

  The beam splitter 46 corresponds to the distance measuring light splitting unit of the present invention, and is connected to the circulator 44 via an optical fiber cable. Further, a plurality of optical fiber cables 47 having different lengths are provided on a facing surface 46a (corresponding to a surface perpendicular to the incident / exiting direction of the present invention, see FIG. 3) of the beam splitter 46 facing the measurement object. It has been. The beam splitter 46 divides the ranging light 36 input from the circulator 44 into a plurality of light beams 36 a and outputs each light beam 36 a to the optical fiber cable 47.

  The optical fiber cable 47 constitutes a plurality of light incident / exit portions of the present invention together with a collimator 47a provided at the tip thereof (the collimator 47a can be omitted). A plurality of optical fiber cables 47 are attached to the facing surface 46a with the collimator 47a facing the measurement object 9. Each optical fiber cable 47 emits the light beam 36a input from the beam splitter 46 toward a plurality of points of the measurement object 9 from the collimator 47a. In addition, the specularly reflected light 36b of the light beam 36a specularly reflected at each of the plurality of points of the measurement object 9 enters the optical fiber cables 47 via the collimator 47a. Note that the symbol “A” in the drawing indicates a direction parallel to the light beam 36a incident / exited from each collimator 47a, and this direction is hereinafter referred to as an incident / exit direction A.

  Each collimator 47a can be used as a starting point of the incident / exit position of the light beam 36a and the regular reflection light 36b. Specifically, the positions of the collimators 47a are adjusted so that the incident / exit positions of the light beam 36a and the regular reflection light 36b in the incident / exit direction A are the same (including substantially the same position). Thereby, the emission position of the light beam 36a from each collimator 47a becomes the same position, and the incident position of the regular reflection light 36b to each collimator 47a becomes the same position.

  FIG. 3 is a front view of the facing surface 46 a of the beam splitter 46. On the facing surface 46a, the optical fiber cable 47 is one-dimensionally arranged in a direction perpendicular to the aforementioned incident / exit direction A with the collimator 47a facing the measurement object 9. Therefore, as shown in FIG. 3, the luminous flux 36a is emitted from the collimator 47a of each optical fiber cable 47 to a plurality of points arranged in the one-dimensional direction of the measurement object 9, and the positive reflections are regularly reflected at the plurality of points. The reflected light 36b enters each optical fiber cable 47 via the collimator 47a.

  FIG. 4 is an explanatory diagram for explaining the specularly reflected light 36b. As shown in FIG. 4, each light beam 36 a, that is, the special light 34 generated by the etalon 20 has a high S / N ratio, and therefore, a plurality of reflected light beams that are incident and reflected on a plurality of points of the measurement object 9. Only the specularly reflected light 36b specularly reflected at each point enters the optical fiber cable 47 through the collimator 47a. Here, the regular reflection light is the reflection light returning along the optical path of the light beam 36a.

  FIG. 5 is an enlarged view of each optical fiber cable 47 and each collimator 47a. FIG. 6A is an explanatory diagram for explaining the delay of the light beam 36 a emitted from the collimator 47 a of each optical fiber cable 47. FIG. 6B is an explanatory diagram for explaining the delay of the specularly reflected light 36 b incident on the collimator 47 a of each optical fiber cable 47.

  As shown in FIG. 5, the length of each optical fiber cable 47 (that is, the optical path length of the light beam 36a in each optical fiber cable 47) is increased in order by the pulse interval D shown in FIG. It is formed to become. Note that “X” in the figure is a predetermined reference length of the optical fiber cable 47. As shown in FIG. 6 (A), the length of each optical fiber cable 47 is increased in order by the pulse interval D so that the light is emitted from the collimator 47a of each optical fiber cable 47 toward a plurality of points of the measurement object 9. The light beam 36a can be sequentially delayed by the pulse interval D. Thereby, each light beam 36a can be made to reach the multiple points of the measuring object 9 sequentially.

  Further, as shown in FIG. 6B, the time during which the specularly reflected light 36b of each light beam 36a enters the collimator 47a of each optical fiber cable 47 can be varied. Specifically, the regular reflection light 36b corresponding to the optical fiber cable 47 having the length “X + 2D” is different from the regular reflection light 36b corresponding to the optical fiber cable 47 having the length “X + D”. The incident light is delayed by an amount corresponding to the level difference of the reflection point of the light 36b. Further, the regular reflection light 36b corresponding to the optical fiber cable 47 having the length “X + 3D” is 2D (pulse interval D × 2) with respect to the regular reflection light 36b corresponding to the optical fiber cable 47 having the length “X + D”. And the incident light is delayed by an amount corresponding to the step of the reflection point of the regular reflection light 36b.

  Similarly, as the length of the optical fiber cable 47 is increased in order by the pulse interval D, the regular reflection light 36b is incident with a delay in order. At this time, the interval between the pulse trains of the regular reflection light 36b is the same as the pulse interval D. Therefore, when the etalon 20 satisfies the following conditions, each of the regular reflection light 36b is selected from a plurality of points of the measurement object 9. It is possible to easily identify whether the light is reflected by a point.

  Here, when the size of the step between two adjacent points of the measurement object 9, that is, the amount of positional deviation in the incident / exit direction A between the two points is larger than the pulse interval D, the adjacent optical fiber cable The specularly reflected light 36b may be incident on the longer one of 47 which is formed longer. In such a case, it is impossible to determine at which of these two points the specularly reflected light 36b specularly reflected at the two points is specularly reflected. For this reason, when the maximum value of the positional deviation amount in the incident / exit direction A of two adjacent points among the plurality of points is G (see FIG. 5), the etalon 20 satisfies the pulse interval D> the maximum value G. That is, the one that can set the repetition frequency fr that satisfies the pulse interval D> the maximum value G is used. The etalon 20 of the shape measuring apparatus 10 can be replaced according to the maximum value G. The setting of the repetition frequency fr by the etalon 20 is possible up to a setting where the pulse interval D is several hundred μm, for example.

  In addition, about the measurement object 9 with which the level | step difference of several points becomes large, it can measure by using two etalon (For example, pulse interval D1 = 0.5mm, pulse interval D2 = 0.55mm).

  Returning to FIG. 1, the specularly reflected light 36 b incident on each optical fiber cable 47 is input to the mixer 25 via the beam splitter 46, the circulator 44, and the like.

  For example, an optical mixer is used as the mixer 25. The mixer 25 mixes the reference light 35 input from the first optical path 23 and the regular reflection light 36b for each of a plurality of points input from the second optical path 24 by a method such as optical multiplication, for example. An optical interference signal 53 between the reference light 35 and the regular reflection light 36b is generated for each of a plurality of points. Further, since the reference light 35 and the regular reflection light 36b include frequency components whose frequencies are close to each other, the optical interference signal 53 is beat-down to a detectable frequency region. Then, an optical interference signal 53 for each of a plurality of points is output from the mixer 25 to the light detection unit 26.

  The light detection unit 26 receives the light interference signals 53 for each of the plurality of points input from the mixer 25 and converts them into electrical signals, and outputs the light interference signals 53 for each of the plurality of points to the interference fringe pattern detection unit 27. The correspondence between each point of the plurality of points and the optical interference signal 53 (that is, to which point among the plurality of points the optical interference signal 53 corresponds) is the relationship between the etalon 20 and each optical fiber cable 47 described above. It is clear from the length.

  The interference fringe pattern detection unit 27 functions as a distance calculation unit of the present invention together with a distance calculation unit 28 described later. The interference fringe pattern detection unit 27 and the distance calculation unit 28 use a known pulse interference position measurement technique based on the optical interference signal 53 for each of a plurality of points input from the light detection unit 26, and each of the optical fiber cables 47. The distance from the collimator 47a to each of a plurality of points of the measurement object 9 is calculated. And the shape calculation part 29 calculates the surface shape of the measuring object 9 based on the distance calculation result to each point of multiple points. Hereinafter, an example of distance calculation to a plurality of points and surface shape calculation will be described.

  As the interference fringe pattern detection unit 27, for example, a lock-in amplifier is used. The interference fringe pattern detection unit 27 detects the interference fringe pattern of the optical interference signal 53 input from the light detection unit 26 described above, and outputs the detection result of the interference fringe pattern to the distance calculation unit 28.

  The distance calculation unit 28 calculates the distance to each of a plurality of points of the measurement object 9 based on the detection result of the interference fringe pattern input from the interference fringe pattern detection unit 27, and the distance calculation result for each of the plurality of points. Is output to the shape calculation unit 29. Since the method for calculating each distance from the interference fringe pattern is known, a specific description is omitted here.

  The shape calculation unit 29 calculates the surface shape of the measurement object 9 based on the distance calculation result for each of a plurality of points input from the distance calculation unit 28. Since the arrangement and intervals of the light beams 36a are known from the arrangement and intervals of the optical fiber cables 47, the relative positional relationship between a plurality of points can be calculated based on the distance calculation result input from the distance calculation unit 28. it can. As a result, the one-dimensional surface shape of the measuring object 9 can be calculated.

<Operation of shape measuring device>
FIG. 7 is a flowchart showing the flow of shape measurement processing in the shape measuring apparatus 10 having the above-described configuration. As shown in FIG. 7, when the measurement object 9 is set in the measurement space of the shape measuring device 10 and then a shape measurement start operation is performed via an operation unit (not shown), a broad spectrum is emitted from the broad spectrum light source 19. (Step S1).

  The broad spectrum emitted from the broad spectrum light source 19 is generated as special light 34 having a repetition frequency fr by the etalon 20 (step S1A), amplified by the optical amplifier 21, and further measured with the reference light 35 by the splitter 22. The light is divided into distance light 36 (step S2). The reference light 35 is output from the splitter 22 to the first optical path 23 and then input to the mixer 25 via the first collimator 38 and the like.

  On the other hand, the distance measuring light 36 is output from the splitter 22 to the second optical path 24, then input to the beam splitter 46 through the circulator 44, and is split into a plurality of light beams 36 a by the beam splitter 46. Each light beam 36a is emitted from the collimator 47a of each optical fiber cable 47 arranged one-dimensionally on the facing surface 46a toward a plurality of points on the measurement object 9 (step S3). Then, the specularly reflected light 36b specularly reflected at each of the plurality of points of the measuring object 9 enters the optical fiber cable 47 through the collimator 47a (step S4).

  At this time, each optical fiber cable 47 is formed so as to increase in order by the pulse interval D, and the etalon 20 having a repetition frequency fr satisfying the pulse interval D> maximum value G is used. The light 36b can be sequentially delayed according to the individual length of the optical fiber cable 47. As a result, it is possible to easily identify at which point among the plurality of points of the measuring object 9 each specularly reflected light 36b is reflected.

  The regular reflection light 36b for each of a plurality of points is input to the mixer 25 via the beam splitter 46, the circulator 44, and the like.

  The reference light 35 and the regular reflection light 36b for each of a plurality of points are sequentially mixed by the mixer 25, and the light interference signal 53 for each of the plurality of points is input from the mixer 25 to the light detection unit 26. And the optical interference signal 53 for every several points is detected in the photon detection part 26 (step S5). The light detection unit 26 sequentially outputs the light interference signals 53 for each of the plurality of points to the interference fringe pattern detection unit 27.

  The interference fringe pattern detection unit 27 detects the interference fringe pattern of the optical interference signal 53 for each of a plurality of points, and sequentially outputs the detection result of each interference fringe pattern to the distance calculation unit 28. Then, the distance calculation unit 28 calculates the distance from the collimator 47a of each optical fiber cable 47 to each of the plurality of points of the measurement object 9 based on the detection result of each interference fringe pattern input from the interference fringe pattern detection unit 27. Calculate (step S6). In the present embodiment, the pulse interval D can be changed according to the shape of the measurement object that is the object to be measured. For example, in this embodiment, the distance is measured at a measurement speed of 1 ms / point or more under the condition that the pulse interval D is 0.5 mm (repetition frequency fr = 300 GHz). Then, the distance calculation unit 28 outputs the calculation result of each distance to the shape calculation unit 29.

  The shape calculation unit 29 calculates the relative positional relationship between the plurality of points of the measurement object 9 based on the calculation result of the distances for each of the plurality of points input from the distance calculation unit 28, the known arrangement of the respective light fluxes 36a, and the intervals thereof. By calculating, the one-dimensional surface shape of the measuring object 9 is calculated (step S7). The calculation result of the surface shape is stored in a storage unit (not shown).

  Next, when the measurement position of the surface shape of the measurement object 9 (position where the light beam 36a is irradiated) is changed, the one-dimensional surface shape of the measurement object 9 at the new measurement position is calculated by the above-described processes. . Thereafter, by repeating the calculation of the one-dimensional surface shape of the measurement object 9 while changing the measurement position, the two-dimensional surface shape of the measurement object 9 is calculated.

  At this time, if the relationship between the pulse interval D> the maximum value G is not satisfied by changing the measurement position of the surface shape, the etalon 20 is changed according to the maximum value G, and the pulse interval D> the maximum value. The repetition frequency fr satisfying G is exchanged for one that can be set. Note that the etalon 20 is similarly replaced when the type of the measurement object 9 changes and the relationship of the pulse interval D> the maximum value G is not satisfied. Here, as described above, measurement may be performed using two etalons.

<Effect of the present invention>
As described above, in the shape measuring apparatus 10 according to the present invention, by using the etalon 20 and the optical fiber cable 47 described above, the light beams 36a are simultaneously emitted from each optical fiber cable 47 toward a plurality of points of the measurement target 9. Even in this case, it is possible to easily identify at which point among the plurality of points of the measurement object 9 each specularly reflected light 36b is reflected. Thereby, multipoint measurement can be performed by one scan. Further, by using the distance measuring light 36 generated by the etalon 20, only the regular reflection light 36b of the light beam 36a at each of a plurality of points can be selected and made incident on each optical fiber cable 47, and the SN ratio is good. An interference fringe pattern can be generated. As a result, the distance to a plurality of points of the measurement object 9 can be measured with high accuracy (specifically, sub-μm accuracy) in a short time, and the surface shape of the measurement object 9 can be calculated with high accuracy. be able to.

  Further, since the repetition frequency fr can be set by the etalon 20 up to a setting in which the pulse interval D is several hundred μm, the etalon 20 is exchanged according to the step (maximum value G) of the surface shape of the measurement object 9. Thus, it is possible to measure a surface shape having a large level difference.

  Further, as described above, since only the regular reflection light 36b specularly reflected at a plurality of points of the measurement object 9 can be made incident on each optical fiber cable 47, the reflectance of the measurement object 9 at a plurality of points can be reduced. The influence does not become a problem, and furthermore, the distance to a plurality of points can be measured even when the optical paths of the light beams 36a overlap.

  Moreover, since the principal part of the shape measuring apparatus 10 of this invention can be comprised by the etalon 20, the beam splitter 46, and each optical fiber cable 47, the shape measuring apparatus 10 is realizable at low cost.

[Shape Measuring Device of Second Embodiment]
FIG. 8 is an explanatory diagram for explaining a main part of the shape measuring apparatus 10A according to the second embodiment of the present invention. In the shape measuring apparatus 10 of the first embodiment, the position of the collimator 47a of each optical fiber cable 47 in the incident / exit direction A is adjusted to the same position. On the other hand, as shown in FIG. 8, in the shape measuring apparatus 10 </ b> A, the position of the collimator 47 a of each optical fiber cable 47 in the incident / exit direction A is sequentially shifted toward the measurement object 9 by the pulse interval D. . As a result, it is possible to correct the production error of the optical fiber length of the optical fiber cable 47, and it is also possible to measure a plane as the measurement object 9 that is the object to be measured. The shape measuring apparatus 10A has basically the same configuration as the shape measuring apparatus 10 of the first embodiment except that the positions of the collimators 47a in the incident / exit direction A are different. For this reason, the same reference numerals are given to the same functions and configurations as those in the first embodiment, and the description thereof is omitted.

  The length of each optical fiber cable 47 is formed so as to increase in order by the pulse interval D as in the first embodiment. For this reason, the optical path length L of each light beam 36a from the collimator 47a of each optical fiber cable 47 to a plurality of points of the measurement object 9 is, for example, (1) L = 10 · D + σ1, (2) L = 9 · D + σ2. (3) L = 8 · D + σ3,... Here, σ 1, σ 2, σ 3,... Are values indicating the relative displacement amounts of the measurement object 9 in the incident / exit direction A, that is, values indicating the surface shape of the measurement object 9. .

  By sequentially increasing the length of each optical fiber cable 47 by the pulse interval D, the light flux 36a emitted from the collimator 47a of each optical fiber cable 47 toward a plurality of points of the measuring object 9 can be sequentially delayed. it can. Thereby, since each light beam 36a can be made to reach the multiple points of the measuring object 9 sequentially, the regular reflection light 36b of each light beam 36a incident on the collimator 47a can be sequentially delayed. As a result, also in the shape measuring apparatus 10A of the second embodiment, it is easy to determine at which point among the plurality of points of the measuring object 9 the specularly reflected light 36b incident on each optical fiber cable 47 is reflected. Since it can identify, the effect similar to the effect demonstrated in 1st Embodiment is acquired.

[Shape Measuring Device of Third Embodiment]
FIG. 9 is a front view of the facing surface 60a of the beam splitter 60 of the shape measuring apparatus according to the third embodiment. In the shape measuring apparatus 10 of the first embodiment, the optical fiber cable 47 and the collimator 47a are one-dimensionally arranged on the facing surface 46a of the beam splitter 46. On the other hand, the optical fiber cables 47 and the like are two-dimensionally arranged on the facing surface 60a (surface perpendicular to the incident / exit direction) of the beam splitter 60 of the shape measuring apparatus according to the third embodiment. As a result, as shown in FIG. 9, the light flux 36a is emitted from the collimator 47a of each optical fiber cable 47 to a plurality of points arranged in the two-dimensional direction of the measurement object 9, and is regularly reflected at the plurality of points. The regular reflection light 36b enters each optical fiber cable 47 through the collimator 47a.

  As described above, in the shape side measuring apparatus according to the third embodiment, the optical fiber cables 47 and the like are two-dimensionally arranged on the facing surface 60a of the beam splitter 60, whereby each of a plurality of points arranged in the two-dimensional direction of the measuring object 9 is arranged. Each distance to the point can be calculated. As a result, the two-dimensional surface shape of the measuring object 9 can be calculated in one measurement.

  The shape-side measuring device of the third embodiment is basically the same configuration as the shape measuring device 10 of the first embodiment, except that it includes a beam splitter 60 in which optical fiber cables 47 and the like are two-dimensionally arranged. Therefore, the same effect as described in the first embodiment can be obtained.

[Shape Measuring Device of Fourth Embodiment]
FIG. 10 is a functional block diagram of the interference fringe pattern detection unit 65 of the shape measuring apparatus according to the fourth embodiment. The shape-side measuring device according to the fourth embodiment is basically the same as the shape-measuring device 10 according to the first embodiment, except that the interference fringe pattern detection unit 65 is different from the shape measuring device 10 according to the first embodiment. The same configuration. For this reason, the same reference numerals are given to the same functions and configurations as those in the first embodiment, and the description thereof is omitted.

  As shown in FIG. 10, the interference fringe pattern detection unit 65 includes a first amplifier 70 (indicated by “AMP1” in the drawing), a low-pass filter 71 (indicated by “LPF” in the drawing), and a differentiation processing unit 72 (indicated by “LPF” in the drawing). A second amplifier 73 (shown as “AMP2” in the figure), and a peak position detector 74 are provided. In the fourth embodiment and the fifth embodiment to be described later, the optical interference signal 53 input from the light detection unit 26 is an integer of the above-described repetition frequency fr, where the optical path difference between the first optical path 23 and the second optical path 24 is the same. The description will be made as an interference fringe pattern signal in which an interference fringe is generated at a position corresponding to double.

  The first amplifier 70 amplifies the interference fringe pattern signal, which is the optical interference signal 53 input from the light detection unit 26, cuts off the noisy zero voltage portion, and further amplifies and outputs it to the low-pass filter 71. To do.

  The low pass filter 71 performs low pass filter processing on the interference fringe pattern signal input from the first amplifier 70 to improve the SN ratio, and then outputs the interference fringe pattern signal to the differentiation processing unit 72.

  The differentiation processing unit 72 performs a differentiation process on the interference fringe pattern signal input from the low-pass filter 71 and then outputs the interference fringe pattern signal to the second amplifier 73.

  The second amplifier 73 generates a trigger signal (pulse signal) at the zero crossing position of the interference fringe pattern signal input from the differentiation processing unit 72, and outputs the trigger signal to the peak position detection unit 74.

  The peak position detection unit 74 detects the peak position of the interference fringe pattern signal based on the trigger signal input from the second amplifier 73 and outputs the detection result of the peak position to the distance calculation unit 28 described above.

  The distance calculation unit 28 calculates the distance from the collimator 47a of each optical fiber cable 47 to each of a plurality of points of the measurement object 9, based on the detection result of the peak position input from the peak position detection unit 74, The distance calculation result for each of a plurality of points is output to the shape calculation unit 29. Since the subsequent processing is basically the same as that of the first embodiment, a specific description is omitted here.

  As described above, in the shape measuring apparatus according to the fourth embodiment, the peak position of the interference fringe pattern signal can be accurately detected, so that the distance to a plurality of points of the measuring object 9 can be measured with higher accuracy. . As a result, the surface shape of the measuring object 9 can be measured with high accuracy. In addition, since the shape side measuring apparatus of 4th Embodiment is the same structure as the shape measuring apparatus 10 of 1st Embodiment except for the point provided with the interference fringe pattern detection part 65, in 1st Embodiment. The same effect as described is obtained.

[Shape Measuring Device of Fifth Embodiment]
FIG. 11 is an explanatory diagram for explaining the function of the interference fringe pattern detection unit 80 of the shape measuring apparatus according to the fifth embodiment. Note that the shape side measuring apparatus of the fifth embodiment is the same as the shape measuring apparatus of the fourth embodiment (that is, the first measuring apparatus) except that the interference fringe pattern detecting unit 80 is different from the shape measuring apparatus of the fourth embodiment. The configuration is basically the same as the shape measuring apparatus 10) of the embodiment. For this reason, the same reference numerals are given to the same functions and configurations as those in the first embodiment, and the description thereof is omitted.

  As shown in FIG. 11, the interference fringe pattern detection unit 80 first executes a first process for performing a square process on the interference fringe pattern signal (see the number in parentheses (1) in the figure). Then, the interference fringe pattern detection unit 80 performs a second process (see number (2) in parentheses in the figure) for performing a low-pass filter process on the interference fringe pattern signal after the square process, and a third process for performing a differentiation process. (See number (3) in parentheses in the figure). As the low-pass filter used in the low-pass filter process, a filter having a large time constant is used in order to eliminate the fine structure of the interference fringe pattern signal.

  Next, the interference fringe pattern detection unit 80 performs a fourth process (see the number in parentheses (4) in the figure) for generating a trigger signal (pulse signal) at the zero crossing position of the interference fringe pattern signal after the differentiation process. The fifth process of detecting the peak position of the interference fringe pattern signal is executed based on the trigger signal generated in the fourth process.

  The interference fringe pattern detection unit 80 outputs the detection result of the peak position detected in the fifth process to the distance calculation unit 28 described above. Hereinafter, similarly to the fourth embodiment, the distance calculation unit 28 performs a sixth process of calculating the distances to a plurality of points of the measurement object 9 based on the detection result of the peak position. Since the subsequent processing is basically the same as that of the first embodiment, a specific description is omitted here.

  As described above, the shape measuring apparatus according to the fifth embodiment can accurately detect the peak position of the interference fringe pattern signal (specifically, it can be detected with a resolution of several tens of nanometers). Can be measured with higher accuracy. As a result, the surface shape of the measuring object 9 can be measured with high accuracy. Note that the shape-side measuring device of the fifth embodiment is basically the same in configuration as the shape measuring device 10 of the first embodiment except that the interference fringe pattern detection unit 80 is provided, so the first embodiment The same effect as described in the above can be obtained.

[Shape Measuring Device of Sixth Embodiment]
FIG. 12 is a schematic diagram of a shape measuring apparatus 10B according to the sixth embodiment. The configuration of the shape measuring apparatus is not limited to the configuration of the shape measuring apparatus 10 of the first embodiment shown in FIG. 1, and can be changed as appropriate. Hereinafter, the shape measuring apparatus 10B will be described as an example of a modification of the shape measuring apparatus with reference to FIG. In addition, about the thing same as said 1st Embodiment on a function and a structure, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  The shape measuring apparatus 10B is roughly divided into a broad spectrum light source 19, an etalon 20, an optical fiber cable 30, a circulator 44B, a splitter 22B, a first optical path 23B, a second optical path 24B, a moving stage 85, a beam splitter 46, and an optical fiber cable 47. A light detection unit 26, an interference fringe pattern detection unit 27, a distance calculation unit 28, and a shape calculation unit 29.

  The circulator 44B outputs the special light 34 input from the etalon 20 toward the splitter 22B, and outputs the return light (optical interference signal 53) from the splitter 22B toward the light detection unit 26.

  The splitter 22B is connected to the circulator 44B, the first optical path 23B, and the second optical path 24B. The splitter 22B divides the special light 34 input from the circulator 44B into the reference light 35 and the distance measuring light 36, and outputs the reference light 35 to the first optical path 23B, and the distance measuring light 36 to the second optical path 24B. Output to.

  A first collimator 38B and a moving stage 85 are provided in the first optical path 23B. The first collimator 38B emits the reference light 35 input from the splitter 22B as a parallel light beam toward the moving stage 85.

  The moving stage 85 is disposed at a position facing the first collimator 38B, and reflects the reference light 35 incident from the first collimator 38B to the first collimator 38B. The moving stage 85 is reciprocated in a direction parallel to the optical path of the reference light 35. Thereby, the optical path length of the reference light 35 in the first optical path 23B can be varied. The reference light 35 reflected by the moving stage 85 is input to the first collimator 38B, and then input from the first collimator 38B to the splitter 22B.

  The above-mentioned beam splitter 46 and a plurality of optical fiber cables 47 are provided in the second optical path 24B. As a result, the distance measuring light 36 input from the splitter 22B to the second optical path 24B is divided into a plurality of light beams 36a by the beam splitter 46, and then the plurality of points of the measuring object 9 from the collimator 47a of each optical fiber cable 47. Are emitted toward Then, the specularly reflected light 36b that is specularly reflected at a plurality of points of the measurement object 9 enters each optical fiber cable 47 through the collimator 47a.

  At this time, as described in the first embodiment, each regular reflection light 36b can be sequentially delayed according to the individual length of the optical fiber cable 47. It is possible to easily identify at which point among the plurality of nine points the light is reflected. Then, the regular reflection light 36b for each of a plurality of points is input to the splitter 22B via the beam splitter 46 and the like.

  The reference light 35 and the regular reflection light 36b for each of a plurality of points are sequentially mixed by the splitter 22B, and the light interference signal 53 for each of the plurality of points is input to the light detection unit 26 from the splitter 22B via the circulator 44B. Then, the light interference signal 53 for each of the plurality of points is detected by the light detection unit 26. The subsequent processing is basically the same as that in the first embodiment, and a detailed description thereof will be omitted.

  As described above, the shape measuring apparatus 10B of the sixth embodiment also includes the etalon 20, the beam splitter 46, and the optical fiber cable 47 similar to those of the first embodiment, and the basic configuration is the shape measuring apparatus 10 of the first embodiment. Therefore, the same effects as those described in the first embodiment can be obtained.

[Others]
In each of the above embodiments, the description has been given by taking the beam splitter as an example of the distance measuring light splitting unit of the present invention, but various distance measuring light splitting units capable of splitting the distance measuring light 36 into a plurality of light beams 36a, for example, The same effect can be obtained by using an optical switch instead of the beam splitter. Further, a diffraction grating, a lens array, a mask, a micro mirror array (DMD: Digital Mirror Device), a transmissive spatial light modulator, or the like can be used.

  In each of the above embodiments, the length of each optical fiber cable 47 is formed so as to increase in order by the pulse interval D. However, when an arbitrary natural number is n, the length of each optical fiber cable 47 is set to n. -You may form long in order of D (including about natural number times). Also in this case, an etalon 20 that satisfies D> G is used.

  In each of the above embodiments, an optical fiber cable has been described as an example of the light incident / exit section of the present invention, but various light incident / exit sections that can be changed in length can be used.

  Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the beam splitter and the optical fiber cable are arranged in a factory without arranging all of the shape measuring apparatuses of the above embodiments in the same place, and other parts connected thereto by optical communication are in different measurement rooms. It is also possible to measure objects that exist in different places / buildings by extending the optical fiber for optical communication connection, such as by placing it.

  DESCRIPTION OF SYMBOLS 10 ... Shape measuring device, 10A ... Shape measuring device, 10B ... Shape measuring device, 20 ... Fabry-Perot etalon, 26 ... Light detection part, 27 ... Interference fringe pattern detection part, 28 ... Distance calculation part, 29 ... Shape calculation 34, special light, 46 ... beam splitter, 47 ... optical fiber cable

Claims (8)

A light source that emits a broad spectrum;
A Fabry-Perot etalon that generates and emits special light that is light having a predetermined repetition frequency from the broad spectrum emitted from the light source, and
A special light splitting unit that splits the special light emitted from the Fabry-Perot etalon into reference light and ranging light;
A ranging light dividing unit that divides the ranging light divided by the special light dividing unit into a plurality of light fluxes;
A plurality of light incident beams that respectively emit the plurality of light beams divided by the distance measuring light splitting unit toward a plurality of points of the measurement object, and the light beams regularly reflected at the plurality of points respectively enter. An emission part;
A light detecting unit that detects an optical interference signal between the reference light divided by the special light dividing unit and the light flux at each of the plurality of points incident on the plurality of light incident / exiting units;
A distance calculating unit that calculates a distance from each of the plurality of light incident / exiting units to each of the plurality of points based on a detection result of the light detecting unit;
When the pulse interval of the special light corresponding to the repetition frequency is D and an arbitrary natural number is n, the optical path length of the light flux in the plurality of light incident / exit portions is sequentially increased by n · D,
The direction parallel to the light flux entering / exiting from the plurality of light entrance / exit portions is defined as the entrance / exit direction, and the maximum value of the positional deviation amount in the entrance / exit direction at two adjacent points among the plurality of points is defined as G. In some cases, the Fabry-Perot etalon satisfies D> G.   The multipoint distance measuring apparatus according to claim 1, wherein the Fabry-Perot etalon is exchangeable according to the value of G.   The multipoint distance measuring device according to claim 1 or 2, wherein the light incident / exiting positions of the light beams in the plurality of light incident / exiting portions are the same position in the incident / exiting direction.   4. The multipoint distance measuring device according to claim 1, wherein the plurality of light incident / exit portions are one-dimensionally arranged in a direction perpendicular to the incident / exit direction. 5.   4. The multipoint distance measuring device according to claim 1, wherein the plurality of light incident / exit portions are two-dimensionally arranged in a plane perpendicular to the incident / exit direction. 5.   The multipoint distance measuring device according to any one of claims 1 to 5, wherein the plurality of light incident / exit sections are a plurality of optical fiber cables having different lengths. The distance calculation unit
A first process for applying a square process to the optical interference signal;
A second process for performing a low-pass filter process on the optical interference signal subjected to the square process;
A third process for differentiating the optical interference signal subjected to the low-pass filter process;
A fourth process for generating a trigger signal at a position of zero crossing of the optical interference signal subjected to the differentiation process;
A fifth process for detecting a peak position of the optical interference signal based on the trigger signal generated in the fourth process;
A sixth process for calculating the distance based on the peak position detected in the fifth process;
The multipoint distance measuring device according to any one of claims 1 to 6, wherein: The multipoint distance measuring device according to any one of claims 1 to 7,
Based on the calculation result of the distance calculation unit, a shape calculation unit that calculates the surface shape of the measurement object;
A shape measuring apparatus comprising:

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