Device for calibrating optical angle measurement device, and method for calibrating optical angle measurement device

Abstract

Provided are a device for calibrating an optical angle measurement device and a method for calibrating the optical angle measurement device with which it is possible to accurately calculate, by using an actual measurement value, the rotation angle of a diffraction grating being measured. The present invention comprises: a light source capable of emitting laser light including light having three or more wavelengths; a reflection-type diffraction grating for allowing entry of incident light from the light source; a plurality of photodetectors for respectively detecting two or more ± nth order diffracted light beams (where n ≥ 1) generated in the diffraction grating; a turning means for enabling the diffraction grating to turn between at least a zeroth position at which a line normal to a grating surface of the diffraction grating is oriented in a reference direction, a first position at which the line normal to the grating surface of the diffraction grating is inclined by a first angle (δ1) with respect to the zeroth position, and a second position at which the line normal to the grating surface of the diffraction grating is inclined by a second angle (δ2) with respect to the zeroth position; and a computation unit for calculating a numerical value for calibration.

Description

Calibration device for optical angle measurement device, calibration method for optical angle measurement device

[0001] The present invention relates to a calibration device for an optical angle measurement device and a calibration method for an optical angle measurement device.

[0002] For example, semiconductor circuit manufacturing equipment generally includes a transfer device that transfers a stage carrying a silicon wafer between multiple manufacturing processes. This transfer device must be able to move and position the stage with high precision in order to precisely process the silicon wafer through the semiconductor process.

[0003] However, when a transfer device that involves mechanical movement moves a stage in one direction, for example, the X direction, rotational movement (such as torsional movement) may occur, which may result in misalignment in the Y or Z direction.

[0004] It is common to measure such characteristics as the transfer deviation for each specific transfer device in advance using an autocollimator or the like to measure the angle change during transfer, and then use this angle change data to calibrate the operation of the transfer device (see, for example, Patent Document 1).

[0005] Conventionally, as a method for detecting an angular change of a measurement object, for example, an optical angle measurement device having the configuration shown in Fig. 12 is known. This optical angle measurement device 100 irradiates incident light L11 containing multiple wavelengths from a light source 101 toward a diffraction grating 102 whose angle is to be measured. Diffracted light L12 emitted from the diffraction grating 102 is detected by a single photodetector 103, and the rotation angle of the diffraction grating 102 is calculated by a calculation unit or the like based on the change in the wavelength of the incident diffracted light L12.

[0006] JP 2011-058872 A

[0007] However, in the conventional optical angle measurement device 100 shown in FIG. 12, the light source 101, the diffraction grating 102, and the photodetector 103 are artificially set and the angle θ βThe angle change can be calculated by assuming that the angle is known, but since it is an artificial setting, there is a possibility that an error may be included. Also, the diffraction grating 102 is set to a predetermined grating pitch using a precision device, and the angle change is calculated based on the assumption that the grating pitch is known, but even the most precise device has its limits, and there is a possibility that the grating pitch may contain an error.

[0008] That is, the angle θ between the optical axis of the incident light L11 from the light source 101 and the optical axis of the diffracted light L12 emitted from the diffraction grating 102 and incident on the photodetector 103 is β There has been no method for detecting the angle θ between the optical axis of the incident light L11 and the normal to the diffraction grating 102, and no method for accurately detecting the actual grating pitch of the diffraction grating 102 without being based on artificial settings or the limitations of the grating pitch forming equipment. α There is a problem that an error may occur in the rotation angle of the diffraction grating 102, and an accurate rotation angle of the diffraction grating 102 may not be obtained.

[0009] The present invention has been proposed in view of the above-mentioned problems, and aims to provide a calibration device for an optical angle measurement device and a calibration method for an optical angle measurement device that are capable of accurately calculating the rotation angle of a diffraction grating, which is the object of measurement, from an actual measurement value.

[0010] In order to solve the above problems, a calibration device for an optical angle measurement device according to one embodiment of the present invention and a calibration method for an optical angle measurement device using the same propose the following means: (1) A calibration device for an optical angle measurement device according to one aspect of the present invention includes a light source capable of emitting laser light containing light of three or more wavelengths, a reflective diffraction grating onto which incident light from the light source is incident, a plurality of photodetectors for detecting two or more ±n (n≧1) order diffracted light beams generated by the diffraction grating, and a plurality of photodetectors for detecting at least a zeroth position where a normal to a grating surface of the diffraction grating is oriented in a reference direction, and a zeroth position where a normal to a grating surface of the diffraction grating is angled at a first angle (δ １and a rotation means for rotating the diffraction grating between a first position tilted by an angle (δ) and a second position tilted by an angle (δ), and a rotation means for rotating the diffraction grating between a first position tilted by an angle (δ) and a second position tilted by an angle (δ) based on the wavelengths of the diffracted light detected by the plurality of photodetectors at the first position and the first position. １ ), the angle (β －１ ), the angle (β ＋１ ), and a calculation unit that calculates each of the above.

[0011] (2) A calibration method for an optical angle measurement device according to one aspect of the present invention includes a first detection step of detecting wavelengths of diffracted light beams incident on a plurality of photodetectors at the zero position, a second detection step of detecting wavelengths of diffracted light beams incident on a plurality of photodetectors at the first position, a third detection step of detecting wavelengths of diffracted light beams incident on a plurality of photodetectors at the second position, and a formation pitch (g), an angle (α), a first angle (δ), and a second angle (δ) based on the wavelengths of diffracted light beams detected by the respective photodetectors obtained in the first detection step, the second detection step, and the third detection step. １ ), second angle (δ ２ ), angle (β ＋１ ), angle (β －１ ) and a calculation step of calculating each of the above.

[0012] According to the present invention, it is possible to provide a calibration device for an optical angle measurement device and a calibration method for an optical angle measurement device that can accurately calculate the rotation angle of a diffraction grating that is the measurement target from actual measured values, and it is also possible to provide a method for calibrating the grating formation pitch of a diffraction grating.

[0013] FIG. 1 is a schematic configuration diagram showing a calibration device for an optical angle measurement device according to one embodiment of the present invention. FIG. 2 is an explanatory diagram explaining a calibration method for an optical angle measurement device according to this embodiment. FIG. 3 is a flowchart showing each step of the calibration method for an optical angle measurement device according to this embodiment. FIG. 4 is a schematic configuration diagram showing a calibration device for an optical angle measurement device according to a first modified example of the present invention. FIG. 5 is a schematic configuration diagram showing a calibration device for an optical angle measurement device according to a second modified example of the present invention. FIG. 6 is a schematic configuration diagram showing a calibration device for an optical angle measurement device according to a third modified example of the present invention. FIG. 7 is a schematic configuration diagram showing a calibration device for an optical angle measurement device according to a fourth modified example of the present invention. FIG. 8 is a photograph showing an experimental calibration device for an optical angle measurement device (experimental device). FIG. 9 is a photograph showing an experimental calibration device for an optical angle measurement device (experimental device). FIG. 10 is a graph showing wavelength values ​​for 10 measurements obtained from a detector at each diffraction grating position. １ ), second angle (δ ２ ), angle (β ＋１ ), angle (β －１ 10 is a graph showing the results of actually calculating the value of the angle measurement error (a) and the value of the angle measurement error (b).

[0014] Hereinafter, a calibration device for an optical angle measurement device and a calibration method for an optical angle measurement device according to one embodiment of the present invention will be described with reference to the drawings. Note that the embodiment shown below is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Furthermore, the drawings used in the following description may show essential parts enlarged for convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as those in reality.

[0015] [Calibration Device for Optical Angle Measurement Device] Figure 1 is a schematic diagram showing the configuration of a calibration device for an optical angle measurement device according to one embodiment of the present invention. The calibration device for an optical angle measurement device 10 of this embodiment includes a light source 11, a diffraction grating 12 whose angle is to be measured, a first photodetector (-1st order photodetector) 13, a second photodetector (+1st order photodetector) 14, a rotating means 15, and a calculation unit 19. A collimator lens 16 is provided between the light source 11 and the diffraction grating 12. Furthermore, condenser lenses 17 and 18 are provided between the diffraction grating 12 and the first photodetector 13, and between the diffraction grating 12 and the second photodetector 14, respectively.

[0016] As an example, light source 11 is configured as a laser light source capable of emitting laser light including light of three wavelengths. Note that light source 11 may be any light source capable of emitting incident light L1 consisting of laser light including light of at least three wavelengths toward diffraction grating 12, and may also be a light source capable of emitting laser light in a continuous wavelength range, for example, white light. Furthermore, each of the three wavelengths may be in any wavelength range of visible light, ultraviolet light, or infrared light.

[0017] The diffraction grating 12 is a reflective diffraction grating, and may have any desired linear irregularities formed at any desired pitch (g) on ​​the grating surface 12a. The diffraction grating 12 may be formed, for example, from a resin plate having micrometer-sized irregularities molded therein.

[0018] The rotating means 15 may be configured as a rotating device that rotates the diffraction grating 12 so that the grating surface 12a of the diffraction grating 12 faces in any direction.

[0019] The collimator lens 16 is an optical lens that converts the laser light diverging from the emission surface of the light source 11 into parallel light, and may be made of a quartz lens or a resin lens that has been aberration-corrected to obtain parallel light. The collimator lens 16 may also be a lens group made up of multiple lenses.

[0020] The condenser lenses 17 and 18 are optical lenses that condense the diffracted light beams L2 and L3, which are parallel light beams emitted from the diffraction grating 12, onto the detection surfaces of the first photodetector 13 and the second photodetector 14. The condenser lenses 17 and 18 may be made of quartz lenses or resin lenses that are aberration-corrected so as to obtain focused light beams. Each of the condenser lenses 17 and 18 may be a lens group made up of a plurality of lenses.

[0021] The first photodetector 13 and the second photodetector 14 may be configured, for example, by a spectroscope. The first photodetector 13 detects the wavelength of diffracted light L2 emitted from the diffraction grating 12 in response to the incidence of incident light L1. The second photodetector 14 detects the wavelength of diffracted light L3 emitted from the diffraction grating 12 in response to the incidence of incident light L1.

[0022] The diffracted light beams L2 and L3 are preferably strong 1st-order and −1st-order diffracted light beams, but may also be 2nd-order or higher order, ±nth-order diffracted light beams (n is an integer). The wavelengths of the diffracted light beams L2 and L3 detected by the first photodetector 13 and the second photodetector 14, respectively, change depending on the rotation angle of the diffraction grating 12.

[0023] The calculation unit 19 may be composed of, for example, a computer (PC) equipped with a CPU, memory, etc., and an interface that connects this computer to the light source 11, the first photodetector 13, the second photodetector 14, the rotation means 15, etc.

[0024] [Calibration Method for Optical Angle Measurement Device] The operation of the optical angle measurement device calibration device 10 configured as described above and the calibration method for the optical angle measurement device will be described below. Fig. 2 is an explanatory diagram illustrating the calibration method for the optical angle measurement device of this embodiment. Fig. 3 is a flowchart showing each step of the calibration method for the optical angle measurement device of this embodiment. In this embodiment, ±1st order diffracted light is detected at the 0th position, the 1st position, and the 2nd position described below.

[0025] When calibrating an optical angle measurement device using the optical angle measurement device calibration device 10, first, a diffraction grating 12 having a grating surface 12a on which a grating with a formation pitch (g) is used, and incident light L1 consisting of laser light containing light of at least three wavelengths is incident from a light source 11 toward the diffraction grating 12 at a zeroth position (see FIG. 2( a)) where the normal to the diffraction grating 12 faces a reference direction. At this zeroth position, the optical axis of the incident light L1 and the normal Q0 to the diffraction grating 12 intersect at an angle (α) on the grating surface 12a. Note that the zeroth position can be any position.

[0026] Then, at this 0th position, the wavelengths of the diffracted light beams incident on the plurality of photodetectors are detected (first detection step S1). In this embodiment, the diffracted light beam L10 generated by making the incident light beam L1 incident on the diffraction grating 12 at the 0th position is received by the first photodetector (-1st order photodetector) 13, and its wavelength (λ0 －１ ) and outputs it to the calculation unit 19. At this time, the optical axis of the incident light L1 and the optical axis of the first photodetector 13 form an angle (β －１ ) and intersect.

[0027] In addition, the diffracted light L20 generated by making the incident light L1 incident on the diffraction grating 12 at the 0th position is received by the second photodetector (+1st order photodetector) 14, and its wavelength (λ0 ＋１ ) and outputs it to the calculation unit 19. At this time, the optical axis of the incident light L1 and the optical axis of the second photodetector 14 form an angle (β ＋１ ) and intersect.

[0028] Next, the diffraction grating 12 is rotated to a first position (see FIG. 2B) by the rotating means 15. At this first position, the normal Q1 to the grating surface 12a of the diffraction grating 12 forms a first angle (δ １ The first position may be any position that is shifted by an arbitrary angle from the zero position.

[0029] Then, at this first position, the wavelengths of the diffracted light beams incident on the plurality of photodetectors are detected (second detection step S2). In this embodiment, the diffracted light beam L11 generated by making the incident light beam L1 incident on the diffraction grating 12 at the first position is received by the first photodetector (-1st order photodetector) 13, and its wavelength (λ1 －１ ) and outputs it to the calculation unit 19.

[0030] In addition, the diffracted light L21 generated by making the incident light L1 incident on the diffraction grating 12 at the first position is received by the second photodetector (+1st order photodetector) 14, and its wavelength (λ1 ＋１ ) and outputs it to the calculation unit 19.

[0031] Next, the diffraction grating 12 is further rotated to a second position (see FIG. 2C) by the rotating means 15. At this second position, the normal Q2 to the grating surface 12a of the diffraction grating 12 forms a second angle (δ ２ The second position may be a position shifted by any angle from the first position.

[0032] Then, at this second position, the wavelengths of the diffracted light beams incident on the plurality of photodetectors are detected (third detection step S3). In this embodiment, the diffracted light beam L12 generated by making the incident light beam L1 incident on the diffraction grating 12 at the second position is received by the first photodetector (-1st order photodetector) 13, and its wavelength (λ2 －１ ) and outputs it to the calculation unit 19.

[0033] In addition, the diffracted light L22 generated by making the incident light L1 incident on the diffraction grating 12 at the second position is received by the second photodetector (+1st order photodetector) 14, and its wavelength (λ2 ＋１ ) and outputs it to the calculation unit 19.

[0034] Next, the calculation unit 19 calculates the wavelengths (λ0 －１ ), (λ0 ＋１ ), (λ1 －１ ), (λ1 ＋１ ), (λ2 －１ ), (λ2 ＋１) are calculated based on the values ​​of the grating pitch (g), angle (α), first angle (δ), and the grating pitch (g) of the diffraction grating 12. １ ), second angle (δ ２ ), angle (β ＋１ ), angle (β －１ ) are calculated (calculation step S4).

[0035] In the calculation step S4, for example, calculation is performed using the diffraction grating equation shown in the following simultaneous equation (1) with six unknowns to calculate each value: sin α - sin(β －１ −α) = −(λ0 －１ ) / g sinα+sin(β ＋１ +α) = (λ0 ＋１ ) / g sin(α+δ １ ) -sin(β －１ -α-δ １ ) = -(λ1 －１ ) / g sin(α+δ １ ) + sin(β ＋１ +α+δ １ ) = (λ1 ＋１ ) / g sin(α+δ ２ ) -sin(β －１ -α-δ ２ ) = -(λ2 －１ ) / g sin(α+δ ２ ) + sin(β ＋１ +α+δ ２ ) = (λ2 ＋１ ) / g (1) The six-variable simultaneous equation (1) is a diffraction grating equation for a vacuum. In a case other than a vacuum, the diffraction grating equation may take into account factors such as refractive index.

[0036] In the above formula (1), λ －１ is the wavelength of the diffracted light detected by the first photodetector at the 0th position, λ ＋１ is the wavelength of the diffracted light detected by the second photodetector at the 0th position, λ －１ is the wavelength of the diffracted light detected by the first photodetector at the first position, λ ＋１ is the wavelength of the diffracted light detected by the second photodetector at the first position, λ －１ is the wavelength of the diffracted light detected by the first photodetector at the second position, λ＋１ is the wavelength of the diffracted light detected by the second photodetector at the second position.

[0037] The diffraction grating equation shown in the above-mentioned formula (1) is a nonlinear equation containing multiple sine functions, and the wavelength of the detected diffracted light contains errors. However, it is possible to obtain an approximate solution that is practical by using the trust region method, the quasi-Newton method, or the like.

[0038] Through the above steps, the angle (β －１ ) and the value of the grating pitch (g) of the diffraction grating 12. If the optical angle measurement device is calibrated only once initially using these values, thereafter accurate and accurate angle information can be obtained from the wavelength information obtained by only one photodetector.

[0039] 4 is a schematic diagram showing the configuration of an optical angle measurement device calibration device according to another embodiment of the present invention. In this modification 1, first-order diffracted light beams having different wavelengths are detected at the 0th position, the 1st position, and the 2nd position.

[0040] In the optical angle measurement device calibration device 20 of this modified example 1, an angle (β ＋１＿１ ) diffracted light L0 of the first wavelength emitted from the diffraction grating 12 ＿１ and a first photodetector (+primary photodetector A) 23 that receives the incident light L1 at an angle (β ＋１＿２ ) diffracted light L0 of the second wavelength emitted from the diffraction grating 12 ＿２ a second photodetector (+1st order photodetector B) 24 that receives the diffracted light L0 ＿１ and diffracted light L0 ＿２ In this state, the diffraction grating 12 is rotated by the rotating means 15 to the first position (see FIG. 2B) and the second position (see FIG. 2C), and measurements are performed in the same manner.

[0041] Even with this configuration, by performing calculations using the diffraction grating equation shown in the following six-variable simultaneous equation (2) based on the wavelength values ​​of the diffracted light at each position on the diffraction grating 12 obtained by the first photodetector 23 and the second photodetector 24, it is possible to obtain values ​​necessary for calibrating the optical angle measurement device, such as the angle between the optical axis of the incident light L1 and the optical axis of the first photodetector 23, and the grating formation pitch of the diffraction grating 12.

[0042] sinα-sin(β －１＿１ −α) = −(λ0 －１＿１ ) / g sinα−sin(β －１＿２ −α) = −(λ0 －１＿２ ) / g sin(α+δ １ ) -sin(β －１＿１ -α-δ １ ) = -(λ1 －１＿１ ) / g sin(α+δ １ ) -sin(β －１＿２ -α-δ １ ) = -(λ1 －１＿２ ) / g sin(α+δ ２ ) -sin(β －１＿１ -α-δ ２ ) = -(λ2 －１＿１ ) / g sin(α+δ ２ ) -sin(β －１＿２ -α-δ ２ ) = -(λ2 －１＿２ ) / g (2) The six-variable simultaneous equation (2) is a diffraction grating equation for a vacuum. In a case other than a vacuum, the diffraction grating equation may take into account factors such as refractive index.

[0043] [Calibration Device for Optical Angle Measurement Device: Modification 2] Fig. 5 is a schematic diagram showing the configuration of a calibration device for optical angle measurement devices according to yet another embodiment of the present invention. In this modification 2, first-order diffracted light and second-order diffracted light are detected at the 0th position, the first position, and the second position, respectively. In the calibration device for optical angle measurement devices 30 according to modification 2, an angle (β ＋１ ) diffracted light L0 emitted from the diffraction grating 12 ＿１ and a first photodetector (+1st order photodetector) 33 that receives the incident light L1 at an angle (β＋２ ) diffracted light L0 emitted from the diffraction grating 12 ＿２ and a second photodetector (+secondary photodetector) 34 that receives the first light. In this state, the diffraction grating 12 is rotated by the rotating means 15 to the first position (see FIG. 2(b)) and the second position (see FIG. 2(c)), and measurements are performed in the same manner.

[0044] Even with this configuration, by performing calculations using the above-mentioned equation (1) based on the wavelength values ​​of the diffracted light at each position on the diffraction grating 12 obtained by the first photodetector 33 and the second photodetector 34, it is possible to obtain values ​​necessary for calibrating the optical angle measurement device, such as the angle between the optical axis of the incident light L1 and the optical axis of the first photodetector 33, and the grating formation pitch of the diffraction grating 12.

[0045] [Calibration Device for Optical Angle Measurement Device: Modification 3] Figure 6 is a schematic diagram showing the configuration of a calibration device for optical angle measurement devices according to yet another embodiment of the present invention. In this modification 3, an example will be described in which the number of detectors is increased to three, thereby reducing the number of rotations to one. Therefore, in this modification 3, first-order diffracted light and second-order diffracted light are detected at the zeroth position and the first position.

[0046] In the optical angle measurement device calibration device 40 of the third modified example, an angle (β －１ ) diffracted light L0 emitted from the diffraction grating 12 ＿１ and a first photodetector (-1st order photodetector) 43 that receives the incident light L1 at an angle (β －２ ) diffracted light L0 emitted from the diffraction grating 12 ＿２ and a second photodetector (-secondary photodetector) 44 that receives the incident light L1 at an angle (β ＋１ ) diffracted light L0 emitted from the diffraction grating 12 ＿３ and a third photodetector (+primary photodetector) 45 that receives the first light.

[0047] In this state, the diffraction grating 12 is rotated to the first position (see FIG. 2B) by the rotating means 15, and measurement is performed in the same manner. In this modification 3, there are three detectors, so three equations can be obtained with one rotation.

[0048] Therefore, the following simultaneous equation (3) with six unknowns is obtained, and by calculating this, six unknowns can be found. －２ −α) = −(2λ0 －２ ) / g sinα−sin(β －１ −α) = −(λ0 －１ ) / g sinα+sin(β ＋１ +α) = (λ0 ＋１ ) / g sin(α+δ)−sin(β －２ -α-δ)=-(2λ1 －２ ) / g sin(α+δ)−sin(β －１ −α−δ)=−(λ1 －１ ) / g sin(α+δ)+sin(β ＋１ +α+δ)=(λ1 ＋１ ) / g (3) The six-variable simultaneous equation (3) is a diffraction grating equation for a vacuum. In a case other than a vacuum, the diffraction grating equation may take into account factors such as refractive index.

[0049] Even with this configuration, values ​​necessary for calibrating the optical angle measurement device, such as the angle between the optical axis of the incident light L1 and the optical axis of the first photodetector 33 and the grating pitch of the diffraction grating 12, are calculated based on the wavelength values ​​of the diffracted light at the two rotation positions of the diffraction grating 12, namely the 0th position and the 1st position, obtained by the first photodetector 43, the second photodetector 44, and the third photodetector 45.

[0050] In particular, in this variant example 3, by providing three photodetectors, the values ​​required for calibrating the optical angle measurement device can be obtained using only the wavelength values ​​of the three photodetectors at two positions (position 0, position 1) obtained by rotating the diffraction grating 12 only once.

[0051] [Calibration Apparatus for Optical Angle Measurement Apparatus: Variation 4] Figure 7 is a schematic diagram showing the configuration of a calibration apparatus for an optical angle measurement apparatus according to yet another embodiment of the present invention. In this variation 4, in the Littrow configuration (a configuration in which the angle of -1st-order diffracted light is selected so that the diffraction angle and the incident angle are the same), the rotation can be reduced to one. In this variation, -1st-order diffracted light is detected at the 0th position and the 1st position.

[0052] In the optical angle measurement device calibration device 50 of this modification 4, the diffracted light L0 emitted from the diffraction grating 12 is aligned with the optical axis of the incident light L1 emitted from the first detector 51, which also serves as a light source. －１ The light is received by the first detector 51, which also serves as a light source. ＋１ is zero.

[0053] In this state, the diffraction grating 12 is rotated to the first position (see FIG. 2B) by the rotating means 15 (see FIG. 1), and measurement is similarly performed with the second detector 54. In this fourth modification, since the Littrow configuration is used, there are four unknowns, and the unknowns can be obtained from the following four equations obtained by one rotation.

[0054] Therefore, the following simultaneous equation (4) with four unknowns is obtained, and by calculating this, four unknowns can be found. ＋１ ) / g sinα−sin(β －１ −α) = −(λ0 －１ ) / g 2sin(α+δ)=(λ1 ＋１ ) / g sin(α+δ)−sin(β －１ −α−δ)=−(λ1 －１ ) / g (4) The above simultaneous equation with four unknowns (4) is a diffraction grating equation for the case in a vacuum. In the case of a place other than a vacuum, the diffraction grating equation may take into account factors such as the refractive index.

[0055] In particular, in this fourth modification, the Littrow arrangement is used, so that the values ​​required for calibrating the optical angle measurement device can be obtained from only the wavelength values ​​of the two photodetectors at two positions (position 0 and position 1) obtained by rotating the diffraction grating 12 only once.

[0056] [Calibration Device for Optical Angle Measurement Device: Variation 5] In the above example, the refractive index around the calibration device for optical angle measurement device is calculated as a known value, but by applying the method of the present invention, the refractive index can also be accurately determined as follows.

[0057] When the refractive index n is unknown, this can be achieved by detecting the 1st-order diffracted light and the −1st-order diffracted light at the 0th position, the 1st position, the 2nd position, and also at a third position to which the diffraction grating 12 is rotated by the rotation means 15. Using FIG. 2 as an example, the rotation means 15 rotates the diffraction grating 12 to the 1st position (see FIG. 2(b)) and the 2nd position (see FIG. 2(c)), and then rotates it to a third position (not shown), and measurements are performed in the same manner. In this modification 5, there are eight unknowns, and the unknowns can be obtained from the following eight equations obtained by three rotations:

[0058] Therefore, the following simultaneous equation (5) with eight unknowns is obtained, and by calculating this, eight unknowns can be found. －１ −α) = −(λ0 －１ ) / ng sinα+sin(β ＋１ +α) = (λ0 ＋１ ) / ng sin(α+δ １ ) -sin(β －１ -α-δ １ ) = -(λ1 －１ ) / ng sin(α+δ １ ) + sin(β ＋１ +α+δ １ ) = (λ1 ＋１ ) / ng sin(α+δ ２ ) -sin(β －１ -α-δ ２ ) = -(λ2 －１ ) / ng sin(α+δ ２ ) + sin(β ＋１ +α+δ ２ ) = (λ2 ＋１ ) / ng sin(α+δ ３ ) -sin(β －１ -α-δ ３ ) = -(λ3 －１ ) / ng sin(α+δ ３) + sin(β ＋１ +α+δ ３ ) = (λ3 ＋１ ) / ng...(5)

[0059] In particular, in this modification 5, the refractive index can be accurately determined.

[0060] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0061] An experimental calibration device (experimental device) for an optical angle measurement device was actually assembled, as shown in the photographs in Figures 8 and 9. Using this experimental device, measurements were repeated 10 times to check the stability of the wavelength information obtained from each detector.

[0062] (a) The angle (α) between the optical axis of the incident light and the normal to the diffraction grating at the initial position (position 0) was set to be approximately 0°. (b) The first angle (δ １ ) is about 0.028°, and the second angle (δ ２ (c) When the angle (α) is 0°, the angle (β －１ ) angle (β ＋１ ) were designed to be approximately 28°.

[0063] FIG. 10 shows a graph of the wavelength values ​​measured 10 times and obtained from each detector at each diffraction grating position (0th position, 1st position, 2nd position).

[0064] Then, from the wavelength values ​​shown in FIG. 10, the formation pitch (g), angle (α), and first angle (δ) are calculated based on the above-mentioned formula (1). １ ), second angle (δ ２ ), angle (β ＋１ ), angle (β －１) were calculated for each of the 10 measurements. The calculated values ​​for each of the 10 measurements are shown in the graph of Figure 11. The calculations were performed using the software "Matlab (registered trademark: MathWorks)" using the confidence region method.

[0065] According to the results shown in FIG. 11, the angle (β ＋１ ), angle (β －１ ) is stable over about six orders of magnitude over 10 measurements. In addition, the grating pitch (g) of the diffraction grating was found to be the same at the 10-pm level over 10 measurements, confirming that it is possible to measure it with sufficient stability.

[0066] According to the calibration device for optical angle measurement devices and the calibration method for optical angle measurement devices of the present invention, it is possible to easily and highly accurately calibrate angular deviations and the like in conveying devices that are required to convey and position with extremely high precision, such as those installed in semiconductor manufacturing equipment.

[0067] Furthermore, by using the measurements obtained by the method of the present invention, it is possible to obtain design errors in the grating pitch of a diffraction grating or errors associated with deterioration, and it is also possible to provide calibration of the grating pitch, which has industrial applicability.

[0068] REFERENCE SIGNS LIST 10... Calibration device for optical angle measurement device 11... Light source 12... Diffraction grating 13... First photodetector (-1st order photodetector) 14... Second photodetector (+1st order photodetector) 15... Rotation means 19... Calculation unit

Claims

1. A light source capable of emitting laser light including light of three or more wavelengths; a reflective diffraction grating onto which the incident light from the light source is incident; a plurality of photodetectors for detecting two or more ±n (n≧1) order diffracted lights generated by the diffraction grating; and a plurality of photodetectors for detecting at least a 0th position where the normal to the grating surface of the diffraction grating is oriented in a reference direction, and a 1st angle (δ １ and a rotation means for rotating the diffraction grating between a first position tilted by an angle (δ), and a second position tilted by an angle (δ) based on the wavelengths of the diffracted light detected by the plurality of photodetectors at the zero position and the first position, and determining a grating formation pitch (g) on ​​the grating surface of the diffraction grating, an angle (α) between the optical axis of the incident light at the zero position and the normal to the diffraction grating, and the first angle (δ). １ ), the angle (β －１ ), the angle (β ＋１ and a calculation unit that calculates each of the above.

2. The rotating means rotates the normal to the grating surface of the diffraction grating at a second angle (δ ２ 2. The calibration device for an optical angle measurement device according to claim 1, wherein the diffraction grating is rotatable between a first position and a second position tilted by an angle of 100°.

3. A calibration device for optical angle measurement devices according to claim 2, wherein the diffracted light detected by the first photodetector is +1st order light, and the diffracted light detected by the second photodetector is -1st order light.

4. The calibration device for an optical angle measurement device according to claim 2, wherein the wavelength of the diffracted light detected by the first photodetector and the wavelength of the diffracted light detected by the second photodetector are different from each other.

5. The calibration device for an optical angle measurement device according to claim 1, wherein three of the photodetectors are arranged.

6. The angle (β －１ 2. The calibration device for an optical angle measurement device according to claim 1, wherein the calibration device is in a Littrow configuration in which the angle .theta.

7. A calibration method for an optical angle measurement device using the calibration device for an optical angle measurement device of claim 2 or 3, comprising: a first detection step of detecting the wavelength of diffracted light incident on each of a plurality of photodetectors at the zero position; a second detection step of detecting the wavelength of diffracted light incident on each of a plurality of photodetectors at the first position; a third detection step of detecting the wavelength of diffracted light incident on each of a plurality of photodetectors at the second position; and determining a formation pitch (g), an angle (α), a first angle (δ) based on the wavelength of diffracted light detected by each of the photodetectors obtained in the first detection step, the second detection step, and the third detection step. １ ), second angle (δ ２ ), angle (β ＋１ ), angle (β －１ and a calculation step of calculating each of the above.

8. The calibration method for an optical angle measurement device according to claim 7, wherein the calculation step uses simultaneous equations with six unknowns, as shown in the following formula (1): sin α - sin(β －１ −α) = −(λ0 －１ ) / g sinα+sin(β ＋１ +α) = (λ0 ＋１ ) / g sin(α+δ １ ) -sin(β －１ -α-δ １ ) = -(λ1 －１ ) / g sin(α+δ １ ) + sin(β ＋１ +α+δ １ ) = (λ1 ＋１ ) / g sin(α+δ ２ ) -sin(β －１ -α-δ ２ ) = -(λ2 －１ ) / g sin(α+δ ２ ) + sin(β ＋１ +α+δ ２ ) = (λ2 ＋１ ) / g (1) where λ0 －１ is the wavelength of the diffracted light detected by the first photodetector at the zero position, λ ＋１ is the wavelength of the diffracted light detected by the second photodetector at the 0 position, λ －１ is the wavelength of the diffracted light detected by the first photodetector at the first position, λ ＋１ is the wavelength of the diffracted light detected by the second photodetector at the first position, λ －１ is the wavelength of the diffracted light detected by the first photodetector at the second position, λ ＋１ is the wavelength of the diffracted light detected by the second photodetector at the second position.

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