JP2013221811A - Surface profile measuring apparatus and light-transmissive object thickness measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with a detection of a rotation angle of a disk of an optical path length variable device in which the disk disposed with a reflector rotates, and dispense with high accuracy of a control for uniformizing a rotation speed in an apparatus for measuring a surface profile of an object or thickness of a light-transmissive object by optical coherence tomography.SOLUTION: Before being applied to an inspection object OB, laser light is made to pass through a reference light-transmissive body 23 so as to reflect on a laser light incident surface and a laser light exiting surface of the reference light-transmissive body 23, and a surface of the inspection object OB, so that, when an optical path length is changed by an optical length variable device 40, three peaks are generated on a signal output by a light receiving sensor 15. Consequently, a distance from the reference light-transmissive body 23 to the inspection object OB is calculated from time differences of generations of three peaks, the thickness of the reference light-transmissive body 23, and a reflective index.

Description

  The present invention relates to an apparatus for measuring the surface profile of an object by optical coherence tomography (OCT), and an apparatus for measuring the thickness of a translucent object by optical coherence tomography.

Optical coherence tomography is a device that divides low-coherence light into two, one is incident on the object to be inspected, the other is incident on a device that changes the optical path length, and both reflected lights interfere to change the optical path length. This is a method for inspecting an inspection object by changing the optical path length of the light incident on the surface, measuring the state of the interference light with respect to the amount of change in the optical path length. Optical coherence tomography is often used to detect a cross-sectional image of the human body (especially the fundus). For example, as shown in Patent Document 1 below, the intensity of light obtained by combining two reflected lights is high. It can also be used to measure the profile of the object surface by detecting the amount of change in the optical path length at the time of increase. If the inspection object is a translucent object, light is reflected from the front and back surfaces. Therefore, if the amount of change in the optical path length at two points when the intensity of the combined light increases is detected, the thickness of the object Can also be measured. In this optical coherence tomography, for example, as shown in Patent Document 2 below, a device that changes the optical path length (hereinafter referred to as an optical path length variable device) includes a mirror that forms an angle of 90 ° on a disk, 90 ° There is a device in which a prism or retroreflector (hereinafter collectively referred to as a triangular reflector) having an angle of? Is arranged, and a disk is rotated to reflect light by the triangular reflector. This variable optical path length device has the advantage that high-speed sweeping is possible and backlash does not occur. And if it reflects light with a translucent body before making light inject into a test target object as shown by following patent document 2, reflection of a test target object will be made into the surface of this translucent body as a reference position. Since the distance to the position can be obtained, the inspection object can be inspected with high accuracy. Further, if this method is applied to the measurement of the profile of the object surface as shown in the following Patent Document 1, the profile of the object surface can be measured with high accuracy. If the inspection object is a translucent object, the thickness of the object can be measured together with the surface profile.

Special table 2003-534540 gazette JP 2004-325286 A

  However, since the optical path length variable device described above needs to obtain the amount of change in the optical path length with respect to the rotation angle, and detect the amount of change in the optical path length by detecting the rotation angle at the time when the intensity of the synthesized light reaches its peak. However, a device for detecting the rotation angle is required, which increases the cost of the apparatus. In addition, if the rotation angle is calculated by controlling the rotation of the disk at a constant rotation speed, measuring the time elapsed since the index signal was input from the encoder built in the rotation motor, It is possible not to provide a device to detect. However, in that case, in order to perform measurement with high accuracy, it is necessary to have a device that controls the rotation speed of the disk to be constant with high accuracy (rotation jitter is very small), which also increases the cost of the device. There is a problem of doing.

The present invention has been made to solve this problem, and the object of the present invention is to provide a triangular shape in an apparatus for measuring the surface profile of an object by optical coherence tomography and an apparatus for measuring the thickness of a transparent object by optical coherence tomography. It is not necessary to provide a device for detecting the rotation angle of the optical path length variable device that rotates the disk on which the reflector is arranged, and it is not necessary to provide a high-precision device for controlling the rotation of the disk to be constant. An object of the present invention is to provide an accurate surface profile measuring device and a translucent object thickness measuring device.

In order to achieve the above object, a feature of the present invention is that a surface profile measuring device is equipped with a reflector that reflects laser light incident on the surface of a disk and emits laser light in a direction opposite to the incident laser light. Then, by rotating the disk at a constant rotation speed by the rotating means, the optical path length changing means for returning the incident laser light by changing the optical path length, and the low-coherence laser light are split into one laser light. The first laser light is incident on the optical path length variable means, the second laser light, which is the other laser light, is irradiated on the inspection object, and the return light from the optical path length variable means and the reflected light from the inspection object And a reference transmission through which the second laser light is transmitted before the inspection target is irradiated with the second laser light and the reflected light from the inspection target is transmitted. A light body, inside the object A reference translucent body having a known optical path length and refractive index of the laser beam, a peak point time detecting means for detecting a time at a timing when a signal output from the light receiver reaches a peak as a peak point time, and an inspection object Moving means while detecting the moving position with respect to the second laser light irradiated to the inspection object, and the reference translucent body detected by the peak point time detecting means at each moving position by the moving means The peak point time corresponding to the laser light incident side surface and the laser light emitting side surface, the peak point time corresponding to the surface of the inspection object detected by the peak point time detecting means, and the object of the reference translucent body Using the optical path length and refractive index of the laser light at, calculate the distance from the laser light incident side surface or laser light emission side surface of the reference transparent body to the inspection object, and calculate the moving position. In that a surface profile calculating means for calculating the surface profile of the test object from a distance.

According to this, from when the peak point time detecting means detects the peak point time corresponding to the laser light incident side surface of the reference translucent body, until the peak point time corresponding to the surface of the inspection object is detected. In a short time zone, the disk of the optical path length varying means can be regarded as rotating at a constant rotational speed. The speed of change of the optical path length by the optical path length varying means can be regarded as substantially constant. Therefore, the time difference between the peak point times corresponding to the laser light incident side surface and the laser light emitting side surface of the reference light transmitting member, the peak point time corresponding to any surface of the reference light transmitting member, and the inspection object The time difference from the peak point time corresponding to the surface is proportional to the value obtained by multiplying the optical path length of the laser light by the refractive index. That is, if these peak point times, the optical path length of the laser light in the object of the reference light transmitting body, and the refractive index of the reference light transmitting body are used, the laser light incident surface of the reference light transmitting body or the laser light emission The distance from the side surface to the inspection object can be calculated with high accuracy. Then, the moving object is moved with respect to the second laser beam by the moving means, and from the laser light incident side surface or the laser light emitting side surface of the reference light transmitting body to the inspection object for each moving position. If the distance is obtained, the surface profile of the inspection object can be obtained with high accuracy. In other words, it is not necessary to provide a device for detecting the rotation angle of the optical path length variable device disk, and it is not necessary to make the device for controlling the rotation of the optical path length variable device constant so that the reference translucent material is not required. If the thickness and refractive index are accurately obtained and stored, the surface profile of the inspection object can be obtained with high accuracy.

Another feature of the present invention is that in the surface profile measuring apparatus, a reflector that emits laser light in a direction opposite to the incident laser light is mounted by reflecting the laser light incident on the surface of the disk. By rotating the rotating means at a constant rotational speed, the optical path length varying means for returning the incident laser light by changing the optical path length, and the rotation position by the rotating means at a predetermined rotational position, the rotation angle is 0. A reference rotation position detecting means for outputting a signal indicating a certain reference rotation position; a low-coherence laser beam; a first laser beam which is one of the laser beams is incident on the optical path length variable means; An optical system that irradiates the inspection object with the second laser light, and combines the return light from the optical path length varying means and the reflected light from the inspection object, and receives the light with a light receiver; 2 laser light The time at the timing at which the reference light transmitting body through which the second laser light is transmitted before irradiation and the reflected light from the inspection object is transmitted and the signal output from the light receiver peaks is defined as the peak time. Peak point time detecting means for detecting, moving means for moving the inspection object while detecting the movement position with respect to the second laser light irradiated to the inspection object, and at each movement position by the moving means Corresponding to the peak point time corresponding to the laser light incident side surface and the laser light emitting side surface of the reference translucent body detected by the peak point time detecting means and the surface of the inspection object detected by the peak point time detecting means Peak point time, a change amount of the optical path length with respect to the rotation angle from the reference rotation position of the disk stored in advance, a laser light incident side surface of the reference light transmission member stored in advance, and Using the rotation angle from the reference rotation position of the disk at the timing when the signal output from the light receiver corresponding to the surface on the laser light emission side peaks, the laser light incident side surface of the reference translucent body or the laser And a surface profile calculating means for calculating a distance from the light emitting side surface to the inspection object and calculating a surface profile of the inspection object from the calculated distance with respect to the moving position.

According to this, from when the peak point time detecting means detects the peak point time corresponding to the laser light incident side surface of the reference translucent body, until the peak point time corresponding to the surface of the inspection object is detected. In a short time zone, the disk of the optical path length varying means can be regarded as rotating at a constant rotational speed. Then, in advance, the rotation angle of the disk at the timing when the signal output from the light receiver corresponding to the laser light incident side surface or the laser light emission side surface of the reference transparent body reaches a peak is accurately measured and stored. Then, from the peak point time corresponding to the laser light incident side surface and the laser light emitting side surface of the reference transparent body and the peak point time corresponding to the surface of the inspection target object, the surface of the inspection target object is supported. The rotation angle of the disk at the timing when the peak occurs can be obtained with high accuracy. If the change amount of the optical path length with respect to the rotation angle of the disk is accurately measured and stored in advance, the laser light incident side surface or the laser light emission side surface of the reference transparent body is determined from the obtained rotation angle. The corresponding change amount of the optical path length and the change amount of the optical path length corresponding to the surface of the inspection object can be accurately obtained. Since the distance from any surface of the reference transparent body to the surface of the inspection object can be calculated from the difference in the change amount of the optical path length, the distance from any surface of the reference light transmission body to the surface of the inspection object can be calculated. The distance can be obtained with high accuracy. Then, the moving object is moved with respect to the second laser beam by the moving means, and from the laser light incident side surface or the laser light emitting side surface of the reference light transmitting body to the inspection object for each moving position. If the distance is obtained, the surface profile of the inspection object can be obtained with high accuracy. In other words, there is no need to provide a device for detecting the rotation angle of the optical path length variable device, and there is no need to make the device for controlling the rotation of the optical path length variable device constant so that the reference rotation of the disc is high. The amount of change in the optical path length with respect to the rotation angle from the position, and the reference of the disk at the timing when the signal output from the receiver corresponding to the laser light incident side surface and the laser light emission side surface of the reference translucent body peaks. If the rotational angle from the rotational position is accurately measured and stored, the surface profile of the inspection object can be obtained with high precision.

Another feature of the present invention is that in the invention of the surface profile measuring apparatus, the peak point time detecting means detects an instantaneous value of the signal output from the light receiver at a set time interval, and the detected signal The peak point time is detected by data processing of the instantaneous value. According to this, the peak point time can be easily and accurately detected only by providing an A / D converter.

  Furthermore, in carrying out the present invention, the present invention is not limited to the invention in the surface profile measuring apparatus, but can be applied to the invention in the translucent object thickness measuring apparatus. That is, if the inspection object is a translucent object, the laser light is reflected on the front and back surfaces of the inspection object, so that the peak time corresponding to the front and back surfaces of the inspection object can be detected, The distance from any surface of the reference light transmitting body to the surface of the inspection object and the distance to the back surface of the inspection object can be obtained. The difference between these distances is the thickness of the inspection object.

1 is an overall configuration diagram of a surface profile measuring apparatus to which the present invention is applied. It is a graph which shows the light intensity by interference of two reflected laser beams with respect to optical path length. It is a flowchart of the program performed by the data processor of a surface profile measuring device. It is a flowchart of the program performed by the data processor of a surface profile measuring device. It is the figure which displayed the instantaneous value data of the signal memorize | stored in the data processing apparatus of a surface profile measuring apparatus in time series, and showed visually. It is the figure which showed the relationship between the rotation angle of the spindle motor which rotates the disk of an optical path length variable apparatus, and optical path length variation | change_quantity. It is a block diagram of the apparatus for detecting the rotation angle of the spindle motor which the peak point corresponding to the surface and back surface of a reference | standard light transmission body generate | occur | produces. It is a block diagram of the apparatus for detecting the relationship between the rotation angle of a spindle motor and the optical path length change amount.

(First embodiment)
Hereinafter, a first embodiment of a surface profile measuring apparatus to which the present invention is applied will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a surface profile measuring apparatus to which the present invention is applied. This surface profile measuring device is a device that measures the surface profile of the inspection object OB placed on the stage 51.

  The surface profile measuring device includes a stage driving device 50. The stage driving device 50 includes a stage 51 on which the inspection object OB is placed and fixed, an X-direction feed motor 52 that moves the stage 51 in the X direction (left-right direction in FIG. 1), and the stage 51 in the Y direction (FIG. 1). , A Y-direction feed motor 53 that moves in the direction perpendicular to the paper surface is provided. The X direction and the Y direction are one direction parallel to the mounting surface of the stage 51 and are orthogonal to each other. The stage driving device 50 includes a screw feed mechanism 54 connected to the output shaft of the X-direction feed motor 52 and a screw feed mechanism (not shown) connected to the output shaft of the Y-direction feed motor 53, respectively. The XY stage moves the stage 51 in the X direction and the Y direction by rotating 52 and 53.

  In the X-direction feed motor 52, an encoder 52a that detects the rotation of the motor 52 and outputs a rotation signal representing the rotation is incorporated. This rotation signal is a pulse train signal that alternately switches between a high level and a low level every time the X-direction feed motor 52 rotates by a predetermined minute angle, and has a phase of π / 2 to identify the rotation direction. It consists of the shifted A phase signal and B phase signal. The rotation signal is output to the X direction feed motor control circuit 62 and the X direction position detection circuit 64.

  The X direction position detection circuit 64 counts up or down the number of pulses of the rotation signal from the encoder 52a in accordance with the rotation direction of the X direction feed motor 52, detects the X direction position of the stage 51 from the count value, A signal representing the directional position (hereinafter simply referred to as the X position) is output to the controller 90. Since the X position represents the relative position of the stage 51 in the X direction with respect to the optical head 20 described later, the X position is treated as an X coordinate value of the irradiation position of the laser beam irradiated from the optical head 20 to the inspection object OB. The irradiation position of the laser beam is a position where the optical head 20 can collect and irradiate the laser beam, and does not ask whether the laser beam is actually irradiated on the inspection object OB.

  The initial setting of the count value in the X direction position detection circuit 64 is performed by an instruction from the controller 90 when the power is turned on. That is, the controller 90 instructs the X-direction feed motor control circuit 62 to move the stage 51 to the X-direction limit position and the X-direction position detection circuit 64 to perform initial setting when the power is turned on. In response to this instruction, the X direction feed motor control circuit 62 rotates the X direction feed motor 52 to move the stage 51 to the X direction limit position. This X direction limit position is a drive limit position in the X direction of the stage 51 driven by the X direction feed motor 52. The X-direction position detection circuit 64 continues to input the rotation signal from the encoder 52a while the stage 51 is moving. When the stage 51 reaches the X-direction limit position and the rotation of the X-direction feed motor 52 stops, the X-direction position detection circuit 64 detects the stop of the rotation signal input from the encoder 52a and sets the count value to “0”. Reset to. At this time, the X-direction position detection circuit 64 outputs a signal for stopping output to the X-direction feed motor control circuit 62, whereby the X-direction feed motor control circuit 62 outputs a drive signal to the X-direction feed motor 52. Stop output. Thereafter, when the X-direction feed motor 52 is driven, the X-direction position detection circuit 64 counts up or down the number of pulses of the rotation signal in accordance with the rotation direction of the X-direction feed motor 52, and the count value The X position of the stage 51 is calculated based on the above and a digital signal representing the X position is continuously output to the X direction feed motor control circuit 62 and the controller 90.

  Similarly, an encoder 53 a that detects the rotation of the motor 53 and outputs a rotation signal representing the rotation is also incorporated in the Y-direction feed motor 53. Similar to the encoder 52a in the X-direction feed motor 52, this rotation signal is a pulse train signal that alternately switches between a high level and a low level each time the Y-direction feed motor 53 rotates by a predetermined minute angle. It consists of an A-phase signal and a B-phase signal that are out of phase by π / 2. This rotation signal is output to the Y-direction feed motor control circuit 63 and the Y-direction position detection circuit 65.

  The Y-direction position detection circuit 65 counts up or down the number of pulses of the rotation signal from the encoder 53a according to the rotation direction of the Y-direction feed motor 53, detects the Y-direction position of the stage 51 from the count value, and Y A digital signal representing a directional position (hereinafter simply referred to as a Y position) is output to the controller 90. Since the Y position represents the relative position of the stage 51 in the Y direction with respect to the optical head 20, it is treated as the Y coordinate value of the irradiation position of the laser light irradiated from the optical head 20 onto the inspection object OB.

  The initial setting of the count value in the Y-direction position detection circuit 65 is performed by an instruction from the controller 90 when the power is turned on, as in the X-direction position detection circuit 64. That is, when an initial setting is instructed from the controller 90, the Y-direction feed motor control circuit 63 rotates the Y-direction feed motor 53 to move the stage 51 to the Y-direction limit position. When the Y-direction position detection circuit 65 detects that the stage 51 has reached the Y-direction limit position and the input of the rotation signal from the encoder 53a is stopped, the Y-direction position detection circuit 65 resets the count value to “0” and feeds the Y-direction feed. An output stop signal is output to the motor control circuit 63. Thereafter, the Y-direction position detection circuit 65 counts up or down the number of pulses of the rotation signal in accordance with the rotation direction of the Y-direction feed motor 53, calculates the Y position of the stage 51 based on the count value, and calculates the Y position. Is continuously output to the Y-direction feed motor control circuit 63 and the controller 90.

  The X-direction feed motor control circuit 62 drives and controls the X-direction feed motor 52 according to an instruction from the controller 90 to move the stage 51 to the designated X position. Specifically, when the X position is input from the controller 90, the X direction feed motor control circuit 52 controls the rotation of the X direction feed motor 52 using the X position input from the X direction position detection circuit 64, and the X direction The X-direction feed motor 52 is rotated until the X position input from the position detection circuit 64 becomes equal to the X position input from the controller 90. The Y-direction feed motor control circuit 63 also drives and controls the Y-direction feed motor 53 according to an instruction from the controller 90 to move the stage 51 to the designated Y position. Specifically, the Y-direction feed motor control circuit 63 inputs the Y position input from the Y-direction position detection circuit 65 from the controller 90 when the Y position is input from the controller 90, similarly to the X-direction feed motor control circuit 62. The Y-direction feed motor 53 is rotated until it becomes equal to the Y position.

  The surface profile measuring device includes a measuring unit 10, an optical head 20, and an optical path length variable device 40. The measurement unit 10 includes a laser light source 11, a collimating lens 12, a condenser lens 13, an optical coupler 14, and a light receiving sensor 15. The laser light source 11 is composed of a super luminescent diode (SLD) or LED, and emits a laser beam with low coherence. As shown in FIG. 2, this low-coherence laser beam is obtained only when the two branched laser beams have the same optical path length when the two branched laser beams interfere with each other. It has the feature that the strength becomes extremely large. The collimating lens 12 converts the low-coherence laser light from the laser light source 11 into parallel light, and the condensing lens 13 condenses the parallel light from the collimating lens 12 and makes it incident on the optical fiber 16. In this case, the focal length of the condenser lens 13 is set so that the laser beam incident on the optical fiber 16 is totally reflected in the optical fiber 16. The laser light incident on the optical fiber 16 is guided to the optical coupler 14.

The optical coupler 14 divides the laser light incident through the optical fiber 16 into two, makes one incident on the optical fiber 31 leading to the optical head 20, and the other incident on the optical fiber 32 leading to the optical path length varying device 40 described later. Let The optical coupler 14 branches the reflected light guided from the optical head 20 via the optical fiber 31 and the reflected light guided from the optical path length varying device 40 via the optical fiber 32 into two parts, respectively. One is guided to the light receiving sensor 15 through the optical fiber 17. In this embodiment, the outgoing light and the reflected light are branched into two using the optical coupler 14, but the outgoing light and the reflected light are converted into parallel light having a small cross-sectional diameter, and a beam splitter is used. You may branch into two.

The light receiving sensor 15 outputs a signal having a magnitude representing the intensity of the received laser beam. In this case, since the two reflected lights incident on the light receiving sensor 15 interfere and the laser light has low coherence, the signal output from the light receiving sensor 15 is the reflection position of the reference translucent body 23 and the inspection object OB. The intensity increases only when the distance from the reflection position to the optical coupler 14 matches the distance from the reflection position (fixed reflector 46) of the optical path length varying device 40 to the optical coupler 14.

  The optical head 20 includes a collimating lens 21, an objective lens 22, and a reference translucent body 23. The collimating lens 21 guides the low-coherence laser beam emitted from the optical fiber 31 to the objective lens 22 as parallel light. The objective lens 22 condenses the laser light, which is parallel light from the collimating lens 21, and irradiates the inspection object OB, which is the measurement object, via the reference transparent body 23. By passing through the reference light transmitting body 23, the laser light is reflected at three places, that is, the incident surface of the reference light transmitting body 23, the exit surface of the reference light transmitting body 23, and the surface of the inspection object OB. Note that the numerical aperture of the objective lens 22 is small, and the surface of the inspection object OB is within the depth of focus of the objective lens 22 even if the surface of the inspection object OB is uneven. The reference light transmitting body 23 is made of glass, and the thickness (the optical path length of the laser light in the reference light transmitting body 23) and the refractive index are measured by a high-precision measuring instrument, and will be described later. 70 is stored in the memory. In this embodiment, glass is used as the reference light transmitting body 23. However, the material of the reference light transmitting body 23 may be other than glass as long as the light transmittance is high.

The optical path length varying device 40 includes a disk-like plate 41 that is rotationally driven by a spindle motor 44, and the disk-like plate 41 has four triangular reflectors 42 arranged at intervals of 90 ° in the circumferential direction. Each of the triangular reflectors 42 is composed of two reflectors whose reflecting surfaces intersect each other at an angle of 90 degrees, and is fixed to the disk-shaped plate 41 so that the reflecting surfaces are perpendicular to the disk-shaped plate 41. ing. Then, the combined vector of the normal vectors of each pair of reflecting surfaces of each triangular reflector 42 is set in the direction in which the disk-shaped plate 41 rotates. Further, the triangular reflector 42 reflects the incident laser light and is in a direction opposite to the incident laser light (parallel to the optical axis of the incident laser light and opposite to the incident laser light). The laser beam is emitted, and the optical axis of the incident laser beam is set to be parallel to a plane perpendicular to both reflection surfaces of the two reflectors (the upper surface of the disk-shaped plate 41). .

  The low-coherence laser light emitted from the optical fiber 32 is converted into parallel light having a minute cross-sectional diameter by the collimating lens 43 and is incident on the triangular reflector 42 of the optical path length varying device 40. The triangular reflector 42 on which the laser beam is incident reflects the laser beam incident on one of the reflecting surfaces to be incident on the other reflecting surface, and reflects the incident laser beam on the other reflecting surface for fixed reflection. The laser beam is emitted toward the body 46, that is, the incident laser beam is emitted in the opposite direction to the incident laser beam. The laser light emitted toward the fixed reflector 46 is incident on the reflecting surface of the fixed reflector 46 perpendicularly. The fixed reflector 46 reflects the incident laser light and makes it incident on the other reflecting surface of the triangular reflector 42. The triangular reflector 42 reflects the laser beam incident on the other reflecting surface and makes it incident on one of the reflecting surfaces, and then reflects the laser beam on one reflecting surface to collimate the lens 43. Through the optical fiber 32 from which the laser beam is emitted. That is, the laser light emitted from the optical fiber 32 enters the optical fiber 32 as a laser light having the same optical axis position and a reverse traveling direction in the optical path length varying device 40. The optical axis positions of the outgoing laser light and the incident laser light are the same because the two reflectors of the triangular reflector 42 are at an angle of 90 °, and the optical axis of the outgoing laser light is two reflectors. This is because the optical axis of the emitted laser beam is parallel to the normal line of the reflecting surface of the fixed reflector 46. In the present embodiment, the triangular reflector 42 is composed of two reflectors whose reflecting surfaces intersect each other at an angle of 90 degrees, but the optical axes of the emitted laser light and the incident laser light in the optical fiber 32 are not limited. As long as the positions are the same, a prism or a retroreflector having an angle of 90 ° may be used as the triangular reflector 42.

  The spindle motor 44 is driven and controlled by the spindle motor control circuit 47 to rotate the disk-like plate 41 at a constant rotational speed. The spindle motor 44 incorporates an encoder 44a that detects the rotation of the motor 44, that is, the disk-shaped plate 41, and outputs a rotation detection signal representing the rotation. This rotation detection signal repeats an index signal Index generated every time the rotation position of the disk-like plate 41 reaches the reference rotation position, and a high level and a low level by a predetermined minute rotation angle, and is mutually phased by π / 2. It is composed of a pair of pulse train signals φA and φB which are shifted from each other. The spindle motor control circuit 47 starts to operate in response to a command from the controller 90, and controls the rotation of the spindle motor 44 so that the number of pulses per unit time of the pulse train signals φA and φB from the encoder 44a becomes a preset value. Thereby, the disk-shaped plate 41 rotates at the set rotational speed. Further, the index signal Index generated from the encoder 44a is input to the distance calculation circuit 73 of the data processing device 70 described later.

  When the disk-shaped plate 41 rotates, the position of the laser beam reflected by the triangular reflector 42 changes, but the optical axis positions of the outgoing laser light and the incident laser light in the optical fiber 32 remain the same. However, the optical path length of the laser light from the exit from the optical fiber 32 to the incidence changes. As a result, when the signal corresponding to the received light intensity output from the light receiving sensor 15 is located at the rotational position where the disk-like plate 41 is located in one triangular reflector 42, the reflection position of the reference translucent body 23 or the inspection object is detected. The distance from the reflection position of OB to the optical coupler 14 and the distance from the reflection position (fixed reflector 46) of the optical path length varying device 40 to the optical coupler 14 become a peak. In this case, the laser light irradiated onto the inspection object OB is reflected at three places, that is, the incident surface of the reference light transmitting body 23, the exit surface of the reference light transmitting body 23, and the surface of the inspection object OB. The signal output from the peak is obtained when the disc-like plate 41 is in three rotational positions in one triangular reflector 42.

  The surface profile measuring device includes a laser driving circuit 30 and a data processing device 50. When a laser irradiation start command is input from the controller 90, the laser driving circuit 30 supplies the laser light source 11 with a voltage and current having a set intensity so that laser light having the set intensity is emitted from the laser light source 11.

The data processing device 70 includes an amplification circuit 71, an A / D converter 72, and a distance calculation circuit 73. The amplification circuit 71 receives a signal having an intensity corresponding to the received light intensity output from the light receiving sensor 15, amplifies the signal with a set amplification factor, and outputs the amplified signal to the A / D converter 72. When an A / D conversion start command is input from the distance calculation circuit 73, the A / D converter 72 performs A / D conversion on a signal input from the amplifier circuit 71 at a set time interval, and is an instantaneous value of the signal. The digital data is output to the distance calculation circuit 73. When an A / D conversion end command is input from the distance calculation circuit 73, the A / D conversion is stopped. The distance calculation circuit 73 has a built-in memory and stores digital data input from the A / D converter 72. In addition, the thickness of the reference light transmitting body 23 (the optical path length of the laser light in the reference light transmitting body 23), the refractive index of the reference light transmitting body 23, and the digital data input from the A / D converter 72 are stored in advance. The time to start and the time to stop storing the input digital data are stored. The distance calculation circuit 73 has a built-in microcomputer, stores digital data input from the A / D converter 72 by executing a program to be described later, processes the stored digital data, and transmits the reference light transmitting body 23. The distance from the laser beam exit surface to the inspection object OB is calculated, and the digital data is output to the controller 90.

Hereinafter, description will be made along the program executed by the controller 90 and the program executed by the distance calculation circuit 73 after the surface profile measuring device is turned on and the inspection object OB is placed on the stage 51. After placing the inspection object OB on the stage 51, the operator inputs the X position and the Y position, which are measurement positions on the inspection object OB, from the input device 92, and inputs a measurement start command. Note that when the measurement position stored in the memory of the controller 90 is used as it is, it is not necessary to input the X position and the Y position. When a measurement start command is input from the input device 92, the controller 90 starts a program (not shown), and sets the X and Y positions, which are the first measurement positions, to the X direction feed motor control circuit 62 and the Y direction feed motor control circuit 63. And outputs an operation start command to the laser drive circuit 30 and the spindle motor control circuit 47. As a result, the first measurement position of the inspection object OB is irradiated with laser light, the optical path length varying device 40 changes the optical path length of the incident laser light and returns it to the original, and the signal output from the light receiving sensor 15 is a disk. When the plate-like plate 41 is at a certain rotational position, a signal is generated in which a peak occurs.

Next, the controller 90 outputs an operation start command to the distance calculation circuit 73. When this command is input, the distance calculation circuit 73 simultaneously starts the program shown in the flowchart of FIG. 3 and the program shown in the flowchart of FIG. Hereinafter, it demonstrates along the flowchart of FIG. When the distance calculation circuit 73 starts the program in step S100, the variable n and the variable k are set to 1 in step S102. The variable n designates the time for starting and ending the storage of data input from the A / D converter 72 stored in advance. The variable k indicates the number of rotations of the disk-like plate 41.

Next, the distance calculation circuit 73 outputs an A / D conversion start command to the A / D converter 72 in step S104. As a result, the A / D converter 72 starts A / D conversion, and digital data that is an instantaneous value of a signal is input to the distance calculation circuit 73 at a set time interval. Next, the distance calculation circuit 73 starts time measurement in step S106, waits for the index signal to be input from the encoder 44a built in the spindle motor 44 in step S108, and when the index signal is input, in step S110. Reset time (set value = 0).

Next, in step S112, the distance calculation circuit 73 repeatedly determines whether the measured time is equal to or longer than the previously stored time t (1), and the measured time is equal to or longer than the time t (1). Then, “Yes” is determined, and the process proceeds to step S114. In step S114, storage of digital data input from the A / D converter 72 is started. In step S116, it is repeatedly determined whether the measured time is equal to or longer than the time t (2) stored in advance. If the measured time is equal to or longer than the time t (2), “Yes” is determined. In step S118, the storage of digital data input from the A / D converter 72 is stopped.

Next, the distance calculation circuit 73 determines in step S120 whether or not the variable n has become 7. Since n is 1 at this stage, the determination is “No”, the process proceeds to step S122, and the variable is determined in step S122. 2 is added to n to make 3, and the process returns to step S112. And the process of step S112-step S118 mentioned above is performed. In this case, since the variable n is 3, the digital data input from the A / D converter 72 is stored during the measurement time from the time t (3) to the time t (4). In step S120, it is determined that the variable n has become “7”, and “No” is determined. In step S122, 2 is added to the variable n to set it to 5, and the process returns to step S112. This process is performed until the variable n becomes 7. As a result, the distance calculation circuit 73 has the measured time from time t (1) to time t (2), from time t (3) to time t (4), from time t (5). The digital data input from the A / D converter 72 is stored between time t (6) and between time t (7) and time t (8).

Here, data storage start times t (1), t (3), t (5), t (7) and data storage stop times t (2), t (4), t (6), t (8 ). As described above, these times are stored in the distance calculation circuit 73 in advance, but this time may be set as follows. When an arbitrary inspection object OB is measured, during the period from when the index signal is input until the disk-like plate 41 of the optical path length varying device 40 rotates once (until the next index signal is input), The digital data input from the A / D converter 72 is stored. Since four triangular reflectors 42 are arranged on the disc-shaped plate 41, when digital data that is instantaneous values of stored signals are arranged in time series, three peaks are obtained as shown in FIG. There are four. 5 is a peak corresponding to the laser light incident surface (upper surface in FIG. 1) of the reference light transmitting body 23, and the peak B is a laser light emitting surface (lower side in FIG. 1) of the reference light transmitting body 23. The peak C corresponds to the surface of the inspection object OB. Since the distance from the optical coupler 14 to the reference translucent body 23 is constant, the four times when the peak A and the peak B occur are constant. The data storage start times t (1), t (3), t (5), and t (7) are set to a time slightly before the time when the peak A occurs. This time is a time at which the time of peak A can be obtained without any unnecessary data being stored. This time is based on the time obtained by numbering the data after the start of digital data storage and by multiplying the number of the data to be peak A by the time interval at which the A / D converter 72 performs A / D conversion. Subtract the minute time and find out.

The data storage stop times t (2), t (4), t (6), and t (8) are slightly shorter than the time when the data value level (signal intensity level) decreases rapidly. Set by time. This is the maximum time during which peak C can be obtained because peak C differs depending on the inspection object OB. In other words, it is the maximum time that the data is valid. Four triangular reflectors 42 are arranged on the disk-like plate 41, but the laser light incident on the optical path length varying device 40 is not always reflected by the triangular reflector 42, but a certain triangular reflection. After being reflected by the body 42, the disc-like plate 41 must be rotated to some extent in order to be reflected by the next triangular reflector 42. Therefore, there is a period in which the laser beam does not return from the optical path length varying device 40 during one rotation of the disk-shaped plate 41. During this period, the light receiving sensor 15 is reflected by the reference translucent body 23 and the inspection object OB. Since only light is received, the level of the signal output from the light receiving sensor 15 decreases rapidly. That is, the period during which the data value level is low is a period during which the data is invalid. Therefore, the data storage stop time is set before this period. Also during this time, the data is numbered after the digital data storage is started, and the A / D converter 72 performs the A / D conversion on the first data number of the data group in which the value level rapidly decreases. What is necessary is just to subtract minute time from the time calculated by multiplying the time interval.

If the digital data input from the A / D converter 72 is stored between the time t (7) and the time t (8), the variable n is 7, so that “Yes” is determined in step S120. Then, the process proceeds to step S124. Since four data groups are stored at this time, when arranged in time series, there are four data groups having peaks A, B, and C as shown in FIG. The distance calculation circuit 73 determines whether or not the variable k has reached the set value M in step S124. As described above, the variable k indicates the number of rotations of the disk-shaped plate 41, and this determination is a process for determining whether the disk-shaped plate 41 has rotated by M, which is the set number of rotations. An appropriate value may be set as the setting value M, for example, 3. Since the variable k is 1 at this stage, it is determined as “No” unless the setting value M is set to 1, and the process proceeds to step S126. In step S126, the variable k is incremented, and in step S128, the variable n And step S108 to step S124 are performed again. As a result, four more data groups having peaks A, B, and C are stored. The processing from step S108 to step S124 is performed until the variable k indicating the number of rotations of the disc-like plate 41 becomes equal to the set value M. In step S124, the variable k becomes equal to the set value M, and “Yes” is obtained. When the determination is made, 4 × M data groups in which peaks A, B, and C exist are stored.

When the distance calculation circuit 73 determines “Yes” in step S124 and proceeds to step S130, it outputs an A / D conversion end command to the A / D converter 72 in step S130. As a result, the A / D converter 72 stops the A / D conversion. Next, the distance calculation circuit 73 stops time measurement in step S132, and ends the execution of the program in step S134.

As described above, the distance calculation circuit 73 starts the program shown in the flowchart of FIG. 3 simultaneously with the program shown in the flowchart of FIG. Hereinafter, description will be given along the program shown in the flowchart of FIG. When the distance calculation circuit 73 starts the program in step S200, it sets the variable p to 1 in step S202. The variable p is a number added to the calculated distance from the laser light emitting surface of the reference transparent body 23 to the surface of the inspection object OB every time it is calculated.

Next, in step S204, the distance calculation circuit 73 determines whether or not there is a data group input from the A / D converter 72 by executing the program shown in the flowchart of FIG. The data group does not exist at the time when the program shown in the flowchart of FIG. 4 is started, but when a certain amount of time has passed, the data group is stored in the memory by executing the program shown in the flowchart of FIG. The process proceeds to step S206.

When the distance calculation circuit 73 proceeds to step S206, the data groups are arranged in time series in step S206, and the time when the peak A shown in FIG. Similarly, the time at which peak B shown in FIG. 5 occurs is set as time B in step S208, and the time at which peak C shown in FIG. In step S212, the time A, B, and C, the thickness t of the reference light transmission body 23 stored in advance, and the refractive index n of the reference light transmission body 23 are used, and the reference light transmission body is expressed by the following formula 1. The distance d from the laser light emission surface 23 to the surface of the inspection object OB is calculated.
(Equation 1)
d = t × n × (C−B) / (B−A)
This equation is valid when the speed of change of the optical path length is constant from time A to time C. Since the optical path length change amount CH with respect to the rotation angle of the disk-shaped plate 41 is theoretically expressed by the following formula 2, strictly speaking, even if the rotation speed of the disk-shaped plate 41 is constant, the speed of the optical path length change is not constant. .
(Equation 2)
CH = 4 · {r · sinΘ + di · (1-cosΘ)}
di: distance between the intersection point b of the rotation direction line from the intersection point a of the two reflecting surfaces of the triangular reflector 42 and the radius line of the disc-like plate 41 and the intersection point a r: intersection point from the center of the disc-like plate 41 Distance to b Θ: Rotation angle of the disk-like plate 41 when the rotation direction line from the intersection point a is parallel to the optical axis of the incident laser beam is 0 ° However, the rotation angle based on Equation 2 When the graph of the amount of change in the optical path length with respect to is obtained, a substantially proportional relationship is obtained as shown in FIG. 6, and therefore the speed of the change in the optical path length is constant within a short time from time A to time C. Can be considered constant. Even if the spindle motor control circuit 47 controls the spindle motor 44 to rotate at a constant rotational speed, the rotational speed has jitter, but the rotational speed is considered to be constant within a short time from time A to time C. Good. Therefore, the distance from the laser light emitting surface of the reference translucent body 23 to the surface of the inspection object OB can be obtained with high accuracy using Equation 1.

Since the distance d calculated in step S212 is obtained for each 4 × M data group in which the peaks A, B, and C exist, each time the distance d is obtained, the number by the variable p is associated, and d ( p). Then, in step S214, it is determined whether the variable p is 4 × M, that is, whether the distance d (p) is 4 × M, and the variable p is set in step S216 until the variable p becomes 4 × M. The process from step S204 to step S214 is repeated with increment. Accordingly, since 4 × M distances d (p) are obtained, “Yes” is determined in step S214, and the process proceeds to step S218.

In step S218, the distance calculation circuit 73 calculates an average value “dave” of 4 × M distances d (p) in step S218, and outputs the distance “dave” to the controller 90 in step S220. In step S222, execution of the program ends.

When the digital data of the distance dave is input from the distance calculation circuit 73, the controller 90 outputs the X position and the Y position as the next measurement positions to the X direction feed motor control circuit 62 and the Y direction feed motor control circuit 63, and the inspection target. The position of the laser beam irradiated on the object OB is set to the next measurement position. Then, an operation start command is output to the distance calculation circuit 73. When this command is input, the distance calculation circuit 73 executes the above-described program, calculates the distance “dave” at the next measurement position, and outputs it to the controller 90. The processing of the controller 90 and the distance calculation circuit 73 is continued until the distance “dave” is acquired at all the measurement positions set in the controller 90. When the distance “dave” is acquired at all the measurement positions, the controller 90 is not shown. By executing the program, an operation stop command is output to the laser drive circuit 30 and the spindle motor control circuit 47. As a result, the laser beam is no longer irradiated from the optical head 20 to the inspection object OB, and the optical path length varying device 40 stops the rotation of the disk-shaped plate 41.

Next, the controller 90 creates image data of the surface profile of the inspection object OB by using the distance dave obtained for each measurement position by executing a program (not shown), and outputs the image data to the display device 94. An image of the surface profile of the inspection object OB is displayed on the display device 94. This image may be a three-dimensional view or a cross-sectional view. Further, if necessary, the controller 90 may calculate a value indicating the degree of unevenness from the surface profile, and display the calculated value on the display device 94. Then, when there is an inspection object OB to be measured next, the operator removes the inspection object OB from the stage 51, places the next inspection object OB on the stage 51, and measures the measurement position from the input device 92. And the measurement start instruction are input, the surface profile of the inspection object OB is measured in the same manner as described above.

According to the embodiment of the surface profile measuring device that operates as described above, the distance calculation circuit 73 of the data processing device 70 corresponds to the laser light incident side surface and the laser light emission side surface of the reference light transmitting body 23. The time difference between time A, which is the peak point time, and time B, and the time difference between time B, which is the peak point time corresponding to the surface of the inspection object OB, is obtained by multiplying the optical path length of the laser light by the refractive index. Based on being proportional to the value, using time A, time B, time C, the thickness of the reference light transmitting body 23 (the optical path length of the laser light in the object), and the refractive index of the reference light transmitting body, The distance from the surface on the laser light emission side of the reference translucent body 23 to the inspection object OB is accurately calculated. Then, by driving the X-direction feed motor 52 and the Y-direction feed motor 53, the inspection object OB is moved with respect to the laser light irradiated from the optical head 20, and the reference translucent body 23 is moved for each movement position. By obtaining the distance from the laser light emitting side surface to the inspection object OB, the surface profile of the inspection object can be obtained with high accuracy. That is, it is not necessary to provide a device for detecting the rotation angle of the disk plate 41 of the optical path length varying device 40, and it is also necessary to provide a device for controlling the rotation of the disk plate 41 of the optical path length varying device 40 so as to have high accuracy. If the thickness and refractive index of the reference translucent body 23 are accurately obtained and stored, the surface profile of the inspection object OB can be obtained with high accuracy. Further, according to the embodiment of the surface profile measuring apparatus that operates as described above, it is possible to easily detect the time points A, B, and C, which are peak point times, simply by providing the A / D converter 72. .

(Second Embodiment)
Next, a second embodiment of the surface profile measuring apparatus to which the present invention is applied will be described. The surface profile measuring apparatus in the second embodiment is different from the surface profile measuring apparatus in the first embodiment in that the distance d from the surface on the laser light emitting side of the reference light transmitting body 23 to the surface of the inspection object OB is different. It is a calculation method. That is, only the calculation method of step S212 in the program shown in the flowchart of FIG. 4 executed by the distance calculation circuit 73 is different. In short, the difference from the calculation method of the first embodiment is that the speed of change of the optical path length is constant from time A to time C in the first embodiment. When the distance from the light body 23 to the inspection object OB is large, the degree of change in the speed of change in the optical path length increases, and the measurement accuracy may deteriorate. Therefore, in the second embodiment, the speed of change of the optical path length changes from time A to time C, but the calculation is performed on the assumption that the rotational speed of the disk plate 41 of the optical path length variable device 40 is constant. ing.

More specifically, the calculation method of the distance d in the second embodiment is described by using a light receiving sensor instead of the thickness of the reference light transmitting body 23 (the optical path length of the laser light in the object) and the refractive index of the reference light transmitting body 23. 15 corresponds to the rotation angle Θ (2n−1) of the disc plate 41 when a peak corresponding to the laser light incident surface of the reference light transmitting member 23 is generated in the signal output from the reference light transmitting member 23, and the laser light emitting surface of the reference light transmitting member 23. The rotation angle Θ (2n) (n = 1 to 4) when the peak to occur is stored in advance, and the relationship between the rotation angle of the disk plate 41 and the optical path length variation is stored in the distance calculation circuit 73 in advance. . Then, the laser light emission surface of the reference translucent body 23 using the times A, B, and C, which are peak point times, obtained by executing the program shown in the flowchart of FIG. 4 and these data stored in advance. The distance d from the surface to the surface of the inspection object OB is calculated.

Before explaining the detailed calculation method of the distance d, the disk plate 41 is used when the peak corresponding to the laser light incident surface of the reference light transmitting member 23 occurs and when the peak corresponding to the laser light emitting surface occurs. A method for obtaining the rotation angles Θ (2n−1) and Θ (2n) (n = 1 to 4) will be described. As shown in FIG. 7, a count circuit 80 is added to the surface profile measuring device, and an A / D converter 72 in the data processing device 70 produces a device that outputs data to the controller 90. The count circuit 80 counts the pulse signal of the encoder after the index signal is input from the encoder 44 a of the spindle motor 44 and outputs the count value to the controller 90. The output interval of the count value to the controller 90 is the same as the data output interval of the A / D converter 72. When the index signal is input from the encoder 44a, the count value is set to zero. 360 ° × (count value / maximum count value) is the rotation angle. The count value corresponds to the rotation angle.

In the apparatus as described above, the disk plate 41 of the optical path length varying device 40 is rotated at a set rotational speed by a command from the controller 90, the laser light is emitted from the light source 11, and the A / D converter 72 is started to operate. After the index signal is input to the controller 90, the digital data (the instantaneous value of the signal) from the A / D converter 72 and the count value (the rotation angle) from the A / D converter 72 until the next index signal is input. ) Is stored in the controller 90. When the data of the instantaneous value of the signal with respect to the rotation angle is created from the stored data, there are four places where a waveform as shown in FIG. 5 is obtained. The horizontal axis at this time is the rotation angle. Then, the rotation angles at peak A and peak B are stored as Θ (2n−1) and Θ (2n) (n = 1 to 4) in ascending order of rotation angle. By repeating this operation a plurality of times, a plurality of Θ (2n−1) and Θ (2n) (n = 1 to 4) are stored, and the stored values are averaged and used for the calculation Θ (2n−1) , Θ (2n) (n = 1 to 4).

Next, a method for acquiring the relationship between the rotation angle of the disk plate 41 and the optical path length change amount will be described. As shown in FIG. 8, the optical head 20 is removed from the surface profile measuring device as shown in FIG. 7, and a laser beam having a small cross-sectional diameter is reflected on the reflecting portion 86 a of the precision moving device 85 via the collimating lens 87. Incidently incident on the surface. The precision moving device 85 is a device that can precisely move the moving unit 86 by the amount of movement instructed from the controller 90. Alternatively, the precision moving device 85 may be a device that moves the moving unit 86 only while there is a movement command from the controller 90 and displays the movement amount with high accuracy. Then, each time the moving unit 86 of the precision moving device 85 is moved, the disk plate 41 of the optical path length varying device 40 is rotated at a set rotational speed by a command from the controller 90, and laser light is emitted from the light source 11. The digital data (instantaneous value of the signal) from the A / D converter 72 and the count circuit until the next index signal is input after the index signal is input to the controller 90 after starting the operation of the / D converter 72 The count value (rotation angle) from 80 is stored in the controller 90. At this time, there are four places where the peak C in FIG. 5 is obtained. The four rotation angles of peak C are stored in correspondence with the movement amount of the moving unit 86. As described above, this operation may be repeated a plurality of times to obtain a plurality of four rotation angles and average them. By performing this operation each time the moving unit 86 of the precision moving device 85 is moved, a relationship between the rotation angle of the disk plate 41 and the moving amount of the moving unit 86 is obtained. Then, the movement amount when the maximum movement amount or the minimum movement amount of the movement unit 86 from which the peak C is obtained is used as a reference (movement amount 0) is calculated, and a value obtained by doubling the movement amount is an optical path length change amount. And Thereby, the relationship between the rotation angle of the disc plate 41 and the optical path length change amount can be acquired. This relationship has four relationships shown in the graph of FIG. 6 and can be theoretically obtained by Equation 2. However, due to an attachment error of the triangular reflector 42 to the disk plate 41, etc. Since there is a discrepancy between the value theoretically derived from 2 and the actual value, it is preferable to acquire as described above in order to perform accurate measurement.

As described above, the rotation angles Θ (2n−1) and Θ (2n) (n = 1 to 4) of the disk plate 41 when the peaks corresponding to the laser light incident surface and the light emitting surface of the reference light transmitting member 23 are generated. ) And the rotation angle of the disk plate 41 and the optical path length change amount are acquired and stored in the distance calculation circuit 73, and the calculation of the distance d in step S212 of the program shown in the flowchart of FIG. , Performed according to equation (4). A, B, and C are the times of peaks A, B, and C obtained in steps S206 to S210.
(Equation 3)
Rotation angle of peak C = {Θ (2n) −Θ (2n−1)} × (C−B) / (B−A)
(Equation 4)
d = {(the optical path length change amount corresponding to the rotation angle of the peak C) − (the optical path length change amount corresponding to the rotation angle of the peak B)} / 2
In this case, the rotation angles Θ (2n−1) and Θ (2n) (n = 1 to 4) are n = 1 in the first data group, and n = 2 in the next data group. The next data group uses n = 3. Then, after n = 4 is used for the next data group, n = 1 is again used for the next data group. As shown in the flowchart of FIG. 3, the storage of data is started after the index signal is generated. In the apparatus of FIGS. 7 and 8, the rotation angle is 0 when the index signal is generated, and Θ ( This is because 2n−1) and Θ (2n) (n = 1 to 4) are stored in ascending order of values.

The calculations according to Equations 3 and 4 are equations assuming that the rotation speed is constant from the time when Peak A occurs to the time when Peak C occurs. As described above, even if controlled at a constant rotational speed, there is jitter in the rotational speed, but the rotational speed can be considered constant within a short time from the time when peak A occurs to the time when peak C occurs.

According to the embodiment of the surface profile measuring device that operates as described above, the distance calculation circuit 73 of the data processing device 70 corresponds to the laser light incident side surface and the laser light emission side surface of the reference light transmitting body 23. The ratio between the time difference between time A, which is the peak point time, and time B, and the time difference between time B, which is the peak point time corresponding to the surface of the inspection object OB, is peak A and peak B. The time A, the time B, the time C, and the time A, the time B, the time C, and the difference between the rotation angle difference of the disk plate 41 and the difference of the rotation angle of the disk plate 41 when the peak B and the peak C occur The rotation angle of the disk plate 41 when the peak C occurs is calculated using the rotation angle of the disk plate 41 when the peak A and peak B that have been measured and stored in advance with accuracy are generated. Furthermore, using the relationship between the rotation angle of the disc plate 41 and the optical path length variation that has been measured and stored in advance with accuracy, the optical path length variation corresponding to the rotation angle when the calculated peak C is generated and stored. The optical path length change amount corresponding to the rotation angle when the peak B is generated is calculated, and from these optical path length change amounts to the inspection object OB from the surface on the laser light emission side of the reference translucent body 23. Calculate distance accurately. Then, by driving the X-direction feed motor 52 and the Y-direction feed motor 53, the inspection object OB is moved with respect to the laser light irradiated from the optical head 20, and the reference translucent body 23 is moved for each movement position. By obtaining the distance from the laser light emitting side surface to the inspection object OB, the surface profile of the inspection object can be obtained with high accuracy. That is, it is not necessary to provide a device for detecting the rotation angle of the disk plate 41 of the optical path length varying device 40, and it is also necessary to provide a device for controlling the rotation of the disk plate 41 of the optical path length varying device 40 so as to have high accuracy. Rather, the amount of change in the optical path length with respect to the rotation angle from the reference rotation position of the disk plate 41 and the signal output by the light receiving sensor 15 corresponding to the laser light incident side surface and the laser light emission side surface of the reference translucent body 23. If the rotation angle from the reference rotation position of the disk at the timing when becomes a peak is accurately measured and stored, the surface profile of the inspection object OB can be determined with high precision. Further, according to the embodiment of the surface profile measuring apparatus that operates as described above, it is possible to easily detect the time points A, B, and C, which are peak point times, simply by providing the A / D converter 72. .

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the object of the present invention.

In the said 1st Embodiment and 2nd Embodiment, although the form which applied this invention to the apparatus which measures the surface profile of the test object OB was shown, the test object OB is a translucent object like a glass plate. If present, the present invention may be applied to an apparatus for measuring the thickness of the inspection object OB. In this case, since the peak d corresponding to the back surface of the inspection object OB is generated after the peak C shown in FIG. 5, the inspection object OB is detected from the laser light emitting surface of the reference translucent body 23 by the same calculation as in the present embodiment. The distance to the back surface of the inspection object OB may be calculated and the distance to the surface of the inspection object OB may be subtracted from this value.

Moreover, in the said 1st Embodiment and 2nd Embodiment, although the distance from the laser beam emission surface of the reference | standard light transmission body 23 to the surface of the test object OB was calculated, it is sufficient if the surface profile of the test object OB can be acquired. Therefore, the distance from the laser light incident surface of the reference translucent body 23 to the surface of the inspection object OB may be calculated. Further, the distance from the point determined from the laser light emitting surface and the laser light incident surface of the reference light transmitting body 23 to the surface of the inspection object OB may be calculated.

In the first and second embodiments, the time at which a peak occurs due to data processing is detected by obtaining the instantaneous value of the signal output from the light receiving sensor 15 at a set time interval. If there is no need for measurement of the above, the time at which the peak occurs may be obtained by using another method. For example, a reference voltage is determined, a signal is generated when the signal output from the light receiving sensor 15 slices the reference voltage, and the time when the signal is generated is measured to obtain 2 near the peak. A time obtained by averaging two times may be used as a peak time.

Moreover, in the said 1st Embodiment and 2nd Embodiment, the time when the signal which the light reception sensor 15 outputs becomes a peak was detected. However, the signal output from the light receiving sensor 15 changes as shown in FIG. That is, the laser beam that is reflected by the laser beam reflected by the surface of the inspection object OB and the laser beam reflected by the optical path length varying device 40 has bottoms on both sides of the peak. The bottom corresponds to a position where the phases of the reflected laser beams are shifted by an optical path length corresponding to π in the optical path lengths of the reflected laser beams. This bottom position is very close to the position where the optical path lengths of the reflected laser beams coincide with each other, and at the same time, the difference between times A, B, and C is used in calculating the distance d to the surface of the inspection object OB. . Therefore, the distance d to the surface of the inspection object OB can be calculated by detecting the time when the bottom occurs instead of the time when the peak occurs and calculating the difference between the detected times. In the second embodiment, the rotation angle of the disk plate 41 at the timing when the bottom occurs may be stored. In this case, an average value of calculation results by both bottoms may be adopted, or a calculation result by one bottom (a smaller bottom is preferable) may be adopted. In the claims, the terms “peak point time” and “peak timing” include the time when the bottom described here occurs and the timing when the bottom occurs.

In the first embodiment and the second embodiment, four triangular reflectors 42 are arranged on the disk plate 41 so that four data can be obtained by one rotation of the disk plate 41. However, the number of triangular reflectors 42 arranged on the disk plate 41 may be changed as appropriate in consideration of the measurement speed and the cost of the apparatus. However, when seven or more are arranged, another triangular reflector 42 blocks the laser light applied to a certain triangular reflector 42, so the number of triangular reflectors 42 is preferably six or less.

In the first and second embodiments, the disk plate 41 of the optical path length varying device 40 is rotated clockwise to change the optical path length from the small side to the large side and rotate clockwise. 5 is obtained, but the signal waveform shown in FIG. 5 is reversed even if the disk plate 41 is rotated counterclockwise to change the optical path length from the larger side to the smaller side. Since the calculation method shown in this embodiment can be used without change, the disk plate 41 may be rotated counterclockwise.

DESCRIPTION OF SYMBOLS 10 ... Measuring part, 11 ... Laser light source, 14 ... Optical coupler, 15 ... Light receiving sensor, 16, 17, 31, 32 ... Optical fiber, 20 ... Optical head, 40 ... Optical path length variable device, 41 ... Disc plate, 42 ... Triangle -Shaped reflector, 44 ... spindle motor, 46 ... fixed reflector, 70 ... data processing device, 72 ... A / D converter, 73 ... distance calculation circuit, 80 ... count circuit, 85 ... precision movement device, 90 ... controller

Claims (6)

A reflector that emits laser light in the direction opposite to the incident laser light by reflecting the laser light incident on the surface of the disk is mounted, and the disk is rotated at a constant rotational speed by a rotating means, thereby allowing the incident light to enter the disk. Optical path length variable means for returning the laser beam by changing the optical path length;
The low-coherence laser beam is branched, the first laser beam, which is one of the laser beams, is incident on the optical path length varying means, the second laser beam, which is the other laser beam, is irradiated on the inspection object, An optical system for synthesizing the return light from the optical path length varying means and the reflected light from the inspection object and receiving the light with a light receiver;
A reference translucent body that transmits the second laser light before the second laser light is irradiated onto the inspection object, and transmits reflected light from the inspection object. A reference translucent body having a known optical path length and refractive index of the laser beam;
A peak point time detecting means for detecting a time at a timing when the signal output from the light receiver becomes a peak, as a peak point time;
Moving means for moving the inspection object while detecting a movement position with respect to the second laser light irradiated on the inspection object;
The peak point time corresponding to the laser light incident side surface and the laser light emission side surface of the reference light transmitting body detected by the peak point time detecting unit at each moving position by the moving unit, and the peak point Using the peak point time corresponding to the surface of the inspection object detected by the time detection means and the optical path length and refractive index of the laser light in the object of the reference light transmitting body, the laser of the reference light transmitting body Surface profile calculating means for calculating a distance from the light incident side surface or the laser light emitting side surface to the inspection object and calculating a surface profile of the inspection object from the calculated distance with respect to the moving position; A surface profile measuring apparatus. A reflector that emits laser light in the direction opposite to the incident laser light by reflecting the laser light incident on the surface of the disk is mounted, and the disk is rotated at a constant rotational speed by a rotating means, thereby allowing the incident light to enter the disk. Optical path length variable means for returning the laser beam by changing the optical path length;
Reference rotation position detection means for outputting a signal indicating a reference rotation position having a rotation angle of 0 each time the rotation position by the rotation means reaches a predetermined rotation position;
The low-coherence laser beam is branched, the first laser beam, which is one of the laser beams, is incident on the optical path length varying means, the second laser beam, which is the other laser beam, is irradiated on the inspection object, An optical system for synthesizing the return light from the optical path length varying means and the reflected light from the inspection object and receiving the light with a light receiver;
A reference translucent body through which the second laser light is transmitted before the second laser light is irradiated onto the inspection object, and a reflected light from the inspection object is transmitted;
A peak point time detecting means for detecting a time at a timing when the signal output from the light receiver becomes a peak, as a peak point time;
Moving means for moving the inspection object while detecting a movement position with respect to the second laser light irradiated on the inspection object;
The peak point time corresponding to the laser light incident side surface and the laser light emission side surface of the reference light transmitting body detected by the peak point time detecting unit at each moving position by the moving unit, and the peak point The peak point time corresponding to the surface of the inspection object detected by the time detection means, the change amount of the optical path length with respect to the rotation angle from the reference rotation position of the disk stored in advance, and the reference stored in advance Using the rotation angle from the reference rotation position of the disk at the timing when the signal output from the light receiver corresponding to the laser light incident side surface and the laser light emission side surface of the translucent body becomes a peak, The distance from the surface on the laser light incident side or the surface on the laser light emission side of the reference light transmitting body to the inspection object is calculated, and the surface of the inspection object is calculated from the calculated distance with respect to the moving position. Surface profile measuring apparatus being characterized in that a surface profile calculating means for calculating a profile. The peak point time detecting means detects an instantaneous value of a signal output from the light receiver at a set time interval, and detects a peak point time by processing the instantaneous value of the detected signal. The surface profile measuring device according to claim 1 or 2, characterized by the above. A reflector that emits laser light in the direction opposite to the incident laser light by reflecting the laser light incident on the surface of the disk is mounted, and the disk is rotated at a constant rotational speed by a rotating means, thereby allowing the incident light to enter the disk. Optical path length variable means for returning the laser beam by changing the optical path length;
A low-coherence laser beam is branched, a first laser beam, which is one of the laser beams, is incident on the optical path length varying means, and a second laser beam, which is the other laser beam, is an inspection object that is a translucent object. An optical system that irradiates an object, combines the return light from the optical path length variable means and the reflected light from the inspection object, and receives the light with a light receiver;
A reference translucent body that transmits the second laser light before the second laser light is irradiated onto the inspection object, and transmits reflected light from the inspection object. A reference translucent body having a known optical path length and refractive index of the laser beam;
A peak point time detecting means for detecting a time at a timing when the signal output from the light receiver becomes a peak, as a peak point time;
The peak point time corresponding to the laser light incident side surface and the laser light emission side surface of the reference transparent body detected by the peak point time detection unit, and the inspection object detected by the peak point time detection unit Thickness calculating means for calculating the thickness of the object to be inspected using the peak point times corresponding to the front and back surfaces and the optical path length and refractive index of the laser light in the object of the reference light transmitting body And a translucent object thickness measuring device. A reflector that emits laser light in the direction opposite to the incident laser light by reflecting the laser light incident on the surface of the disk is mounted, and the disk is rotated at a constant rotational speed by a rotating means, thereby allowing the incident light to enter the disk. Optical path length variable means for returning the laser beam by changing the optical path length;
Reference rotation position detection means for outputting a signal indicating a reference rotation position having a rotation angle of 0 each time the rotation position by the rotation means reaches a predetermined rotation position;
A low-coherence laser beam is branched, a first laser beam, which is one of the laser beams, is incident on the optical path length varying means, and a second laser beam, which is the other laser beam, is an inspection object that is a translucent object. An optical system that irradiates an object, combines the return light from the optical path length variable means and the reflected light from the inspection object, and receives the light with a light receiver;
A reference translucent body through which the second laser light is transmitted before the second laser light is irradiated onto the inspection object, and a reflected light from the inspection object is transmitted;
A peak point time detecting means for detecting a time at a timing when the signal output from the light receiver becomes a peak, as a peak point time;
The peak point time corresponding to the laser light incident side surface and the laser light emission side surface of the reference transparent body detected by the peak point time detection unit, and the inspection object detected by the peak point time detection unit The peak point times corresponding to the front and back surfaces of the disk, the change amount of the optical path length with respect to the rotation angle from the reference rotation position of the disk stored in advance, and the laser light incidence of the reference light transmitter stored in advance The rotation angle from the reference rotation position of the disk at the timing when the signal output from the light receiver corresponding to the surface on the side and the surface on the laser light emission side peaks, and the thickness of the inspection object is determined. A translucent object thickness measuring apparatus comprising a thickness calculating means for calculating. The peak point time detecting means detects an instantaneous value of a signal output from the light receiver at a set time interval, and detects a peak point time by processing the instantaneous value of the detected signal. The translucent object thickness measuring apparatus according to claim 4 or 5, characterized in that