Inspection device and inspection method

Abstract

To provide an inspection device and inspection method, which allow for easily inspecting diffraction optical element sheets with high accuracy.SOLUTION: An inspection device 10 provided herein is for inspecting a diffraction optical element sheet 80 comprising multiple unit diffraction optical elements 81 arrayed on a sheet surface. The inspection device 10 comprises a holding unit 20 for holding the diffraction optical element sheet 80, a light projection unit 30 having a laser light source 32 configured to project polarized inspection light L onto the diffraction optical element sheet 80 held by the holding unit 20, an image capturing unit 50 for capturing an image of the inspection light L transmitting through the diffraction optical element sheet 80, and a control unit 60 configured to acquire the image of the diffraction optical element sheet 80 from the image capturing unit 50 and inspect each of the unit diffraction optical elements 81 based on the image.SELECTED DRAWING: Figure 3

Description

【Technical Field】 【0001】 The present disclosure relates to an inspection apparatus and an inspection method. 【Background Art】 【0002】 Conventionally, diffractive optical elements have been known. A diffractive optical element is also called a Diffractive Optical Element or DOE. A diffractive optical element is an optical element that shapes light from a light source of various sensors into the size, shape, etc. of an irradiation region to be targeted. 【0003】 A diffractive optical element is an element that applies the diffraction phenomenon. The diffraction phenomenon is a phenomenon that occurs when light passes through a place where materials having different refractive indexes are arranged periodically. A diffractive optical element is basically designed for light of a single wavelength. The diffractive optical element can theoretically shape light into an arbitrary shape. The diffractive optical element can control the uniformity of the light distribution within the irradiation region. 【0004】 A diffractive optical element is manufactured by microfabrication on the order of nm. In particular, in order to diffract light of a long wavelength, it is necessary to form a fine shape with a high aspect ratio. Therefore, for the manufacture of a diffractive optical element, an electron beam lithography technique using an electron beam is used. In order to improve productivity, a large number of replicated substrates may be produced by molding resin using a substrate such as quartz created by electron beam lithography as a master. 【0005】 By mounting optical elements such as diffractive optical elements on multiple faces on a single substrate, a large number of optical elements can be manufactured from a single substrate. The optical elements mounted on multiple faces on the substrate are separated into individual pieces by means such as dicing and punching, and are mounted on electrical components such as holders. 【0006】 As mentioned above, diffractive optical elements shape light with their minute shapes, so even slight changes in shape can easily cause significant changes in their optical properties. Therefore, it is desirable to inspect whether the optical properties of diffractive optical elements used in sensors and other applications requiring particularly high detection accuracy are appropriate after manufacturing. [Prior art documents] [Patent Documents] 【0007】 [Patent Document 1] International Publication No. 2018 / 216575 [Overview of the Initiative] [Problems that the invention aims to solve] 【0008】 This disclosure provides an inspection apparatus and inspection method that can easily and accurately inspect diffractive optical element sheets. [Means for solving the problem] 【0009】 The inspection apparatus according to this embodiment is an inspection apparatus for inspecting a diffractive optical element sheet in which a plurality of unit diffractive optical elements are arranged on the sheet surface, and comprises: a holding unit for holding the diffractive optical element sheet; a light projection unit having a laser light source that projects polarized inspection light onto the diffractive optical element sheet held by the holding unit; an imaging unit that captures the inspection light transmitted through the diffractive optical element sheet; and a control unit that acquires an image of the diffractive optical element sheet from the imaging unit and inspects each unit diffractive optical element based on the image. 【0010】 In the inspection apparatus according to this embodiment, a polarization control unit is positioned between the laser light source and the diffractive optical element sheet, the polarization control unit changes the polarization state of the inspection light, and the control unit inspects each unit diffractive optical element based on the inspection light whose polarization state has been changed by the polarization control unit. 【0011】 In the inspection apparatus according to this embodiment, the diffractive optical element sheet has a reference side surface that determines the orientation, and the imaging unit first images the diffractive optical element sheet with the reference side surface facing a first direction, and then images the diffractive optical element sheet with the reference side surface facing a second direction rotated 90° with respect to the first direction, and the control unit may inspect each unit diffractive optical element based on the image of the diffractive optical element sheet taken in the first direction and the image of the diffractive optical element sheet taken in the second direction. 【0012】 In the inspection apparatus according to this embodiment, a state monitoring unit for monitoring the state of the inspection light may be provided between the laser light source and the diffractive optical element sheet. 【0013】 In the inspection apparatus according to this embodiment, the diffractive optical element sheet is attached to a holder, the diffractive optical element sheet attached to the holder is housed in a cassette buffer, and the apparatus may further include a transport device for transporting the diffractive optical element sheet attached to the holder between the cassette buffer and the holding unit. 【0014】 In the inspection apparatus according to this embodiment, the diffractive optical element sheet may be provided with alignment marks for positioning the holder and the diffractive optical element sheet. 【0015】 The inspection method according to this embodiment is an inspection method for inspecting a diffractive optical element sheet in which a plurality of unit diffractive optical elements are arranged on the sheet surface, and comprises the steps of: holding the diffractive optical element sheet in a holding unit; emitting polarized inspection light from a light-emitting unit having a laser light source onto the diffractive optical element sheet held in the holding unit; photographing the inspection light that has passed through the diffractive optical element sheet; acquiring an image of the photographed diffractive optical element sheet; and inspecting each unit diffractive optical element based on the image. 【0016】 In the inspection method according to this embodiment, the step of changing the polarization state of the inspection light between the laser light source and the diffractive optical element sheet may further include a step of inspecting each unit diffractive optical element based on the inspection light whose polarization state has been changed. 【0017】 In the inspection method according to this embodiment, the diffractive optical element sheet has a reference side surface that determines the orientation, and the imaging step includes imaging the diffractive optical element sheet with the reference side surface facing a first direction, and imaging the diffractive optical element sheet with the reference side surface facing a second direction rotated 90° with respect to the first direction, and the inspection step of each unit diffractive optical element may include inspecting each unit diffractive optical element based on an image of the diffractive optical element sheet imaged in the first direction and an image of the diffractive optical element sheet imaged in the second direction. 【0018】 In the inspection method according to this embodiment, a step of monitoring the state of the inspection light between the laser light source and the diffractive optical element sheet may be further included. 【0019】 In the inspection method according to this embodiment, the diffractive optical element sheet is attached to a holder, the diffractive optical element sheet attached to the holder is housed in a cassette buffer, and the method may further include a step of transporting the diffractive optical element sheet attached to the holder between the cassette buffer and the holding unit. 【0020】 In the inspection method according to this embodiment, alignment marks for positioning the holder and the diffractive optical element sheet may be provided on the diffractive optical element sheet, and the method may further include a step of positioning the holder and the diffractive optical element sheet. [Effects of the Invention] 【0021】 According to this embodiment, diffractive optical element sheets can be inspected easily and with high precision. [Brief explanation of the drawing] 【0022】 [Figure 1] Figure 1 is a schematic plan view showing an inspection apparatus according to the first embodiment. [Figure 2] Figure 2 is a front view showing a holder and a diffractive optical element sheet. [Figure 3] Figure 3 is a schematic cross-sectional view showing a part of the inspection apparatus according to the first embodiment along the optical path of inspection light. [Figure 4] Figures 4(a)-(d) are diagrams showing an inspection method according to the first embodiment. [Figure 5] Figures 5(a)-(c) are diagrams showing an inspection method according to the first embodiment. [Figure 6] Figure 6 is a schematic cross-sectional view showing a part of the inspection apparatus according to the second embodiment along the optical path of inspection light. [Figure 7] Figures 7(a) and (b) are diagrams showing diffractive optical element sheets facing the first direction and the second direction, respectively. [Figure 8] Figures 8(a) and (b) are diagrams showing diffractive optical element sheets facing the first direction and the second direction, respectively. [Figure 9] Figures 9(a) and (b) are graphs showing the efficiency measured for each dot of each chip of the diffractive optical element sheet in the first embodiment and the second embodiment, respectively. 【Embodiments for Carrying Out the Invention】 【0023】 (First Embodiment) Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 5. In the following figures, the same parts are denoted by the same reference numerals, and some detailed descriptions may be omitted. 【0024】 Figure 1 is a schematic plan view showing the inspection apparatus according to this embodiment. Note that all figures shown below, including Figure 1, are schematic representations, and the size and shape of each part are exaggerated as appropriate for ease of understanding. Furthermore, while specific numerical values, shapes, materials, etc., are described in the following explanation, these can be modified as appropriate. In this specification, terms specifying shape and geometric conditions, such as parallel and orthogonal, include not only their strict meaning but also states that exhibit similar optical functions and have an error that can be considered parallel or orthogonal. In this specification, terms such as plate, sheet, and film are used. These are generally used in the order of thickness, from thickest to thinnest, plate, sheet, and film, and this specification follows that convention. There is no technical significance to this distinction, and these terms can be replaced as appropriate. In this specification, the sheet surface refers to the surface of each sheet that aligns with the planar direction when viewed as a whole. The same applies to the plate surface and film surface. Also, in this specification, transparent means that it transmits at least the wavelength of light to be used. For example, even if a material does not transmit visible light, if it transmits infrared light, it will be treated as transparent when used for infrared applications. 【0025】 As shown in Figure 1, the inspection apparatus 10 according to this embodiment is an apparatus for inspecting a diffractive optical element sheet 80 in which a plurality of unit diffractive optical elements are arranged within the sheet surface. In this embodiment, the case in which the unit diffractive optical elements are chips 81 will be described as an example. The inspection apparatus 10 includes a holding unit 20, a light emitting unit 30, an imaging unit 50, a control unit 60, a transport device 70, and a cassette buffer 75. 【0026】 The holding unit 20 detachably holds the diffractive optical element sheet 80. The diffractive optical element sheet 80 is detachably attached to the holder 90. The inspection device 10 inspects the diffractive optical element sheet 80 while it is attached to the holder 90. 【0027】 The holding portion 20 holds the diffractive optical element sheet 80 in the state in which it is attached to the holder 90. The holding portion 20 may also hold the holder 90 and the diffractive optical element sheet 80 so that they can move. The holding portion 20 holds the diffractive optical element sheet 80 so that the sheet surface of the diffractive optical element sheet 80 is oriented along the vertical direction. 【0028】 Next, the diffractive optical element sheet 80 will be described. As shown in Figure 2, the diffractive optical element sheet 80 is a so-called polyhedron sheet, film, or plate on which multiple chips 81 are arranged. Multiple chips 81 are arranged on the diffractive optical element sheet 80 in their pre-separated state. After being separated, the chips 81 are used, for example, by being attached to the light source part of a sensor. Each chip 81 has a diffractive optical element region 82 located approximately in the center. This diffractive optical element region 82 is molded with a fine uneven pattern. The diffractive optical element region 82 diffracts and emits light of a predetermined wavelength, and has the function of shaping the light. The diffractive optical element region 82 functions as a Diffractive Optical Element or DOE. Note that in Figure 2, for ease of understanding and to make the figure easier to see, the chips 81 on the diffractive optical element sheet 80 are shown arranged in 3 rows vertically and horizontally, but in reality, a larger number of chips are arranged. 【0029】 As shown in Figure 1, the holding unit 20 includes a transport stage 21 and a drive unit 22. The transport stage 21 is fixed to the floor surface. The drive unit 22 moves the holder 90 and the diffractive optical element sheet 80 together on the transport stage 21. The drive unit 22 may also move on the transport stage 21. The drive unit 22 moves the holder 90 and the diffractive optical element sheet 80 in a plane perpendicular to the optical axis of the inspection light L. In Figure 1, the drive unit 22 moves the holder 90 and the diffractive optical element sheet 80 along the Y-axis and Z-axis directions. The drive unit 22 allows the holder 90 and the diffractive optical element sheet 80 to take on a confirmation position and an inspection position. The confirmation position is the position where the holder 90 and the diffractive optical element sheet 80 are positioned using a position confirmation camera 25, which will be described later. In Figure 1, the holder 90 and the diffractive optical element sheet 80 in the confirmation position are shown by dashed lines. The inspection position is where the imaging unit 50 photographs the diffractive optical element sheet 80 and inspects the diffractive optical element sheet 80. At the inspection position, the inspection light L passes through each chip 81 of the diffractive optical element sheet 80. In Figure 1, the holder 90 and the diffractive optical element sheet 80 at the inspection position are shown by solid lines. 【0030】 As described above, the diffractive optical element sheet 80 is detachably attached to the holder 90. The holder 90 may be made of a rigid frame-shaped member such as metal. The planar shape of the holder 90 may be rectangular. The outer circumference of the holder 90 is larger than the outer circumference of the diffractive optical element sheet 80. As shown in Figure 2, the holder 90 has a holder opening 91. The diffractive optical element sheet 80 is attached to the position where the holder opening 91 is provided. The inspection light L from the light-emitting unit 30 passes through the holder opening 91. 【0031】 As shown in Figure 2, alignment marks 83 are provided on the diffractive optical element sheet 80. The alignment marks 83 are for positioning the holder 90 and the diffractive optical element sheet 80. The alignment marks 83 are provided near the four corners of the diffractive optical element sheet 80. Note that the position of the alignment marks 83 is not limited to the position of the chip 81. There may be one alignment mark 83 or multiple alignment marks 83. 【0032】 A reference mark 93 is provided on the holder 90. In this case, multiple reference marks 93 are provided. Each reference mark 93 is positioned at a location corresponding to each alignment mark 83. By comparing the alignment marks 83 on the diffractive optical element sheet 80 with the reference marks 93 on the holder 90, the position of the diffractive optical element sheet 80 relative to the holder 90 can be determined. 【0033】 As shown in Figure 1, a position confirmation camera 25 is positioned near the holding unit 20. The position confirmation camera 25 photographs the holder 90 and the diffractive optical element sheet 80 at the confirmation position. By photographing the holder 90 and the diffractive optical element sheet 80, the position confirmation camera 25 determines the amount of displacement of the diffractive optical element sheet 80 relative to the holder 90. This displacement data may be sent to the control unit 60. The control unit 60 calculates a correction value based on the transmitted displacement amount. The control unit 60 controls the drive unit 22 based on the correction value. This fine-tunes the inspection position for inspecting the holder 90 and the diffractive optical element sheet 80. If the position of the diffractive optical element sheet 80 relative to the holder 90 is shifted by more than a reference value, the holder 90 and the diffractive optical element sheet 80 may be excluded from the inspection. In this case, the holder 90 and the diffractive optical element sheet 80 may be returned to the cassette buffer 75. 【0034】 The cassette buffer 75 is positioned at least a distance from the optical axis of the inspection light L. The cassette buffer 75 is fixed to the floor. The cassette buffer 75 temporarily accommodates the diffractive optical element sheet 80 while it is attached to the holder 90. Multiple holders 90 and diffractive optical element sheets 80 are housed in the cassette buffer 75. Within the cassette buffer 75, the main surface of the diffractive optical element sheet 80 is perpendicular to the floor. In this case, the floor is parallel to the XY plane. The cassette buffer 75 houses both the diffractive optical element sheet 80 before inspection by the inspection device 10 and the diffractive optical element sheet 80 after inspection by the inspection device 10. The operation of housing and removing the holders 90 and diffractive optical element sheets 80 from the cassette buffer 75 may be performed by a transport device 70, which will be described later, or by human hands. 【0035】 A transport device 70 is provided between the cassette buffer 75 and the holding unit 20. This transport device 70 may be an industrial robot, such as a vertical articulated robot. The transport device 70 transports the diffractive optical element sheet 80, which is attached to the holder 90, between the cassette buffer 75 and the holding unit 20. Specifically, the transport device 70 takes out the diffractive optical element sheet 80, which is stored in the cassette buffer 75 before inspection, along with the holder 90, and holds it in the holding unit 20. The transport device 70 also takes out the diffractive optical element sheet 80, which is stored in the holding unit 20 after inspection, along with the holder 90, and stores it in the cassette buffer 75. 【0036】 The light-emitting unit 30 emits polarized inspection light L onto a diffractive optical element sheet 80 held by the holding unit 20. As shown in Figure 3, the light-emitting unit 30 includes a housing 31, a laser light source 32, a polarization control unit 33, a collimator lens 34, a variable aperture 35, an ND filter 36, and a beam splitter 37. The laser light source 32, polarization control unit 33, collimator lens 34, variable aperture 35, ND filter 36, and beam splitter 37 are each arranged within the housing 31. Furthermore, the polarization control unit 33, collimator lens 34, variable aperture 35, ND filter 36, and beam splitter 37 are arranged in this order along the direction of propagation of the inspection light L from the laser light source 32. 【0037】 The laser light source 32 emits laser light, which is the inspection light L. The wavelength of this laser light is the wavelength diffracted by the diffraction grating formed in the diffractive optical element region 82 of the diffractive optical element sheet 80. The laser light source 32 may also emit laser light from an edge-emitting laser. An edge-emitting laser is also called an Edge Emitting Laser or EEL. In this embodiment, the laser light from the laser light source 32 is a polarized laser. For example, the laser light from the laser light source 32 may be a linearly polarized laser. 【0038】 The polarization control unit 33 is located on the optical path of the inspection light L from the laser light source 32. The polarization control unit 33 changes the polarization state of the laser light, which is the inspection light L from the laser light source 32. The polarization state that the polarization control unit 33 changes is, for example, the direction of polarization. For example, the polarization control unit 33 may change the linearly polarized inspection light L to circularly polarized light. 【0039】 A polarization controller may be used as the polarization control unit 33. Specifically, the polarization controller may be a paddle-type polarization controller. In a paddle-type polarization controller, stress is generated in the fiber by rotating the paddles. The effect of birefringence due to this stress is used to change the polarization state of light passing through the fiber under external force. Examples of paddle-type polarization controllers include a two-paddle type polarization controller or a three-paddle type polarization controller. Of these, the three-paddle type polarization controller can change the polarization state of light to any desired polarization state by arranging a quarter-wave plate, a half-wave plate, and a quarter-wave plate in order. The polarization control unit 33 is located between the laser light source 32 and the collimator lens 34, but it is sufficient to be located at least between the laser light source 32 and the diffractive optical element sheet 80. 【0040】 In this way, by providing a polarization control unit 33 between the laser light source 32 and the diffractive optical element sheet 80, the polarization state of the inspection light L from the laser light source 32 can be adjusted. When polarization is applied to the diffractive optical element sheet 80, the state of the emitted light may change depending on the polarization state of the light. Examples of light states include the direction of light distribution and / or light intensity. Therefore, by providing a polarization control unit 33, the influence of polarization on the inspection light L can be reduced. This improves the reproducibility of the measurement of the inspection light L. 【0041】 Furthermore, when the chip 81 is attached to the light source of the product, the polarization state of the light source may differ from the polarization state of the laser light from the laser light source 32. For example, the laser light source 32 may be an end-face emitting laser and use a linearly polarized light source. On the other hand, the light source of the product may be a vertical-cavity surface-emitting laser and use a circularly polarized light source. A vertical-cavity surface-emitting laser is also called a VCSEL. In this case, by using the polarization control unit 33, the polarization state of the inspection light L from the inspection device 10 can be matched to the polarization state of the light source of the product. As a result, the inspection accuracy of the inspection device 10 can be improved. 【0042】 The inspection light L that has passed through the polarization control unit 33 is incident on the collimator lens 34. The collimator lens 34 is a lens that corrects the inspection light L emitted by the laser light source 32 into parallel light. 【0043】 The inspection light L that has passed through the collimator lens 34 enters the variable aperture 35. The variable aperture 35 is an aperture whose diameter can be changed. The variable aperture 35 narrows the inspection light L that has passed through the collimator lens 34, thereby adjusting the amount of light. In addition, the variable aperture 35 can also block light that spreads out and cannot be corrected by the collimator lens 34. 【0044】 The inspection light L that has passed through the variable aperture 35 enters the ND filter 36. The ND filter 36 reduces the amount of inspection light L regardless of its wavelength. 【0045】 The inspection light L that has passed through the ND filter 36 is incident on the beam splitter 37. The beam splitter 37 transmits a portion of the inspection light L incident from the ND filter 36 side and emits it towards the diffractive optical element sheet 80 side. The beam splitter 37 also reflects a portion of the inspection light L incident from the ND filter 36 side, splits it, and directs it towards the state monitoring unit 40. 【0046】 The status monitoring unit 40 is located on the branched optical path branched from the beam splitter 37. The status monitoring unit 40 may also be located inside the housing 31. The status monitoring unit 40 monitors the status of the inspection light L inline. The status monitoring unit 40 may continuously monitor the status of the inspection light L. The status monitoring unit 40 transmits data regarding the status of the inspection light L to the control unit 60. The status monitoring unit 40 may transmit data to the control unit 60 for each diffractive optical element sheet 80 to be inspected. Alternatively, the status monitoring unit 40 may transmit data to the control unit 60 periodically, for example, once a day. 【0047】 The state monitoring unit 40 may, for example, monitor the output of the polarized inspection light L, its polarization profile, and its polarization state. In this case, the state monitoring unit 40 includes an integrating sphere 41, a polarization degree measuring device 42, and a beam profiler 43. 【0048】 The integrating sphere 41 is positioned on the branched optical path from the beam splitter 37. The integrating sphere 41 has a spherical inner surface, and a highly reflective light-scattering material is provided on its inner surface. The integrating sphere 41 scatters and homogenizes the captured inspection light L. For example, the S142C manufactured by THORABS may be used as the integrating sphere 41. 【0049】 The polarization meter 42 is positioned around the integrating sphere 41. The polarization meter 42 measures the polarization degree of the polarized test light L. Polarization degree is a quantity that represents the degree of polarization. For example, the PAX1000IR1 manufactured by THORABS may be used as the polarization meter 42. 【0050】 The beam profiler 43 is positioned around the integrating sphere 41. The beam profiler 43 measures the beam diameter and intensity distribution of the inspection light L, which is laser light. For example, the SP920s manufactured by OPHIR may be used as the beam profiler 43. 【0051】 In this way, by monitoring the state of the inspection light L incident on the diffractive optical element sheet 80 in-line, the diffractive optical element sheet 80 can be inspected stably and with high precision. Furthermore, by constantly monitoring the beam diameter and polarization state of the inspection light L, it is easy to determine whether the cause of a defect in the diffractive optical element sheet 80 lies on the light-emitting unit 30 side. 【0052】 The imaging unit 50 is a camera that captures the inspection light L that has passed through the diffractive optical element sheet 80. In this embodiment, the imaging unit 50 captures the inspection light L that has passed through the diffractive optical element sheet 80 from the opposite side of the light-emitting unit 30. The imaging unit 50 may also have a collimator lens 51 and a camera 52. The inspection light L that has passed through the diffractive optical element sheet 80 is incident on the collimator lens 51. The collimator lens 51 is a lens for correcting the inspection light L that has passed through the diffractive optical element sheet 80 into parallel light. The camera 52 may have an image sensor capable of capturing the light emitted by the light-emitting unit 30. For example, if the diffractive optical element sheet 80 to be inspected is for infrared light, the light-emitting unit 30 emits infrared light. In that case, the camera 52 may have an image sensor capable of capturing infrared light. 【0053】 The control unit 60 includes an image capture control unit 61 and an evaluation unit 62. The image capture control unit 61 controls the image capture unit 50 to perform imaging while the inspection light L is projected onto the chip 81. As a result, the image capture control unit 61 sequentially captures the inspection light L. Here, "sequentially" includes continuous operation, and the image capture may be performed by temporarily stopping the holding unit 20, or by continuously capturing images while the holding unit 20 continues to move. Furthermore, the phrase "sequentially capture images" here includes not only the capture of still images but also the capture of video. Video capture is a series of still image captures, and in this embodiment, there is no need to distinguish between them. For example, in a certain shooting mode, the image capture control unit 61 may repeatedly move and stop the holding unit 20, and the image capture unit 50 may perform imaging while the holding unit 20 is stopped. 【0054】 For example, the shooting control unit 61 controls the system to take a picture when the light spot S from the light projection unit 30 is in the center of the chip 81, as shown in Figure 2. The shooting control unit 61 then repeatedly moves and stops the holding unit 20, sequentially taking pictures of other adjacent chips 81. Here, the shooting control unit 61 calculates the position of the chip 81 using pre-set alignment information and alignment information from the position confirmation camera 25, and determines the timing for taking a picture. Furthermore, for the shooting of chips 81 aligned in at least one direction, the shooting control unit 61 may continue moving the holding unit 20 while taking pictures with the shooting unit 50. In this case, only the center of the chip 81 may be photographed, or other areas may also be photographed. 【0055】 The evaluation unit 62 acquires an image of the diffractive optical element sheet 80 from the imaging unit 50 and inspects each chip 81 based on the image. For example, the evaluation unit 62 evaluates the light distribution characteristics of the chip 81 based on the image information obtained by the imaging unit 50. For example, the evaluation unit 62 may evaluate the light distribution of the light irradiation pattern of the diffractive optical element sheet 80. Examples of light distribution include the position or intensity of the light irradiation pattern. The specific content of the evaluation performed by the evaluation unit 62 can be evaluated using an appropriate algorithm depending on what kind of light distribution characteristics the chip 81 of the diffractive optical element sheet 80 to be inspected is required to perform. 【0056】 Next, we will describe the operation of this embodiment, which has the above configuration. Specifically, we will explain the inspection method using the inspection device 10 according to this embodiment. 【0057】 First, as shown in Figure 4(a), the diffractive optical element sheet 80 is attached to the holder 90 outside the inspection device 10. In this case, the diffractive optical element sheet 80 may be attached to the holder 90 with high positional accuracy using a jig or the like (not shown). 【0058】 Next, as shown in Figure 4(b), the holder 90 and the diffractive optical element sheet 80 are placed inside the cassette buffer 75 of the inspection device 10. At this time, multiple sets of the holder 90 and the diffractive optical element sheet 80 are placed inside the cassette buffer 75. The process of placing the holder 90 and the diffractive optical element sheet 80 may be done manually or automatically using an industrial robot or the like. 【0059】 Next, the holder 90 and the diffractive optical element sheet 80 are held in the holding unit 20. At this time, as shown in Figure 4(c), the transport device 70, such as an industrial robot, automatically removes the holder 90 and the diffractive optical element sheet 80 from the cassette buffer 75. Then, as shown in Figure 4(d), the transport device 70 holds the holder 90 and the diffractive optical element sheet 80 in a predetermined position on the transport stage 21 of the holding unit 20. After that, the transport device 70 retracts from the holding unit 20. 【0060】 Next, as shown in Figure 5(a), the drive unit 22 moves the holder 90 and the diffractive optical element sheet 80 on the transport stage 21. This moves the holder 90 and the diffractive optical element sheet 80 to the confirmation position. In Figure 5(a), the holder 90 and the diffractive optical element sheet 80 in the confirmation position are shown by solid lines. 【0061】 Next, the position confirmation camera 25 photographs the holder 90 and the diffractive optical element sheet 80 at the confirmation position. By photographing the holder 90 and the diffractive optical element sheet 80, the position confirmation camera 25 determines the amount of displacement of the diffractive optical element sheet 80 relative to the holder 90. The control unit 60 calculates a correction value based on the transmitted displacement amount. 【0062】 Next, the holder 90 and the diffractive optical element sheet 80 are positioned. At this time, as shown in Figure 5(b), the drive unit 22 moves the holder 90 and the diffractive optical element sheet 80 on the transport stage 21. As a result, the holder 90 and the diffractive optical element sheet 80 move from the confirmation position to the inspection position. In Figure 5(b), the holder 90 and the diffractive optical element sheet 80 at the inspection position are shown by solid lines. At this time, the control unit 60 positions the holder 90 and the diffractive optical element sheet 80 while correcting their positions. Specifically, the control unit 60 controls the drive unit 22 based on correction values ​​obtained from the image from the position confirmation camera 25 to fine-tune the inspection position for inspecting the holder 90 and the diffractive optical element sheet 80. 【0063】 Next, each chip 81 of the diffractive optical element sheet 80 is individually spot-irradiated with inspection light L. At this time, as shown in Figure 5(c), inspection light L is projected from the light-emitting unit 30 having a laser light source 32 onto the diffractive optical element sheet 80 held in the holding unit 20. 【0064】 During this time, as shown in Figure 3, first, polarized inspection light L is irradiated from the laser light source 32. This inspection light L is incident on the polarization control unit 33. In the polarization control unit 33, the polarization state of the laser light, which is the inspection light L, is changed. For example, the polarization control unit 33 may change linearly polarized laser light to circularly polarized light. Next, the inspection light L is corrected to parallel light by the collimator lens 34. Subsequently, the light intensity of the inspection light L is adjusted by the variable aperture 35 and reduced by the ND filter 36. After that, a portion of the inspection light L is split by the beam splitter 37. 【0065】 A portion of the branched inspection light L reaches the state monitoring unit 40. The state monitoring unit 40 monitors the state of the inspection light L passing between the laser light source 32 and the diffractive optical element sheet 80. The state monitoring unit 40 periodically transmits data regarding the state of the inspection light L to the control unit 60. The state monitoring unit 40 may also monitor, for example, the output of the polarized inspection light L, its polarization profile, and its polarization state. 【0066】 The inspection light L that was not split by the beam splitter 37 is incident on the diffractive optical element sheet 80. The diffractive optical element sheet 80 is held in the holding unit 20 while attached to the holder 90. The imaging unit 50 captures the inspection light L that has passed through the diffractive optical element sheet 80. As a result, the imaging unit 50 acquires an image by directly projecting the light irradiation pattern and transmits it to the control unit 60. 【0067】 The control unit 60 acquires an image of the light irradiation pattern of the diffractive optical element sheet 80 from the imaging unit 50, and inspects each chip 81 based on this image. The inspection content may be, for example, the light distribution of the light irradiation pattern of the diffractive optical element sheet 80. Examples of the light distribution include the position and intensity of the inspection light L passing through each chip 81. 【0068】 After the inspection of the diffractive optical element sheet 80 is completed, the transport device 70 automatically removes the holder 90 and the diffractive optical element sheet 80 held in the holding unit 20. Then, the transport device 70 returns the holder 90 and the diffractive optical element sheet 80 to the cassette buffer 75. 【0069】 As described above, the inspection device 10 according to this embodiment allows for easy and highly accurate inspection of the diffractive optical element sheet 80. 【0070】 As described above, in this embodiment, the polarization control unit 33 is positioned between the laser light source 32 and the diffractive optical element sheet 80. The polarization control unit 33 changes the polarization state of the inspection light L. The control unit 60 inspects each chip 81 based on the inspection light L whose polarization state has been changed by the polarization control unit 33. This allows each chip 81 to be inspected without being affected by the polarization state of the inspection light L. Also, for example, even if the polarization state of the inspection light L from the laser light source 32 is different from the polarization state of the light source part of the product, the polarization state of the inspection light L can be matched to the polarization state of the light source part of the product. Therefore, the accuracy of the inspection results by the inspection device 10 can be improved. 【0071】 As described above, according to this embodiment, a state monitoring unit 40 is provided between the laser light source 32 and the diffractive optical element sheet 80 to monitor the state of the inspection light L. This allows the output of the inspection light L from the laser light source 32 to be measured inline, enabling stable and highly accurate inspection by the inspection device 10. Furthermore, by constantly monitoring the state of the inspection light L, it is easy to determine whether or not the inspection light L from the laser light source 32 is the cause when an abnormality occurs in the inspection results from the inspection device 10. 【0072】 As described above, according to this embodiment, the diffractive optical element sheet 80, attached to the holder 90, is housed in the cassette buffer 75. The transport device 70 transports the diffractive optical element sheet 80, attached to the holder 90, between the cassette buffer 75 and the holding unit 20. In this case, the operation of attaching the diffractive optical element sheet 80 to the holder 90 can be performed outside the inspection device 10. This reduces the switching time between the completion of inspection of the diffractive optical element sheet 80 and the start of the next inspection, thereby increasing the time that can be continuously inspected. 【0073】 As described above, according to this embodiment, the diffractive optical element sheet 80 is provided with alignment marks 83 for positioning the holder 90 and the diffractive optical element sheet 80. This eliminates the need for manual alignment between the holder 90 and the diffractive optical element sheet 80. Therefore, the switchover time between the completion of inspection of the diffractive optical element sheet 80 and the start of the next inspection can be shortened, and the time during which continuous inspection is possible can be extended. 【0074】 (Second Embodiment) Next, a second embodiment will be described with reference to Figures 6 to 8. Figures 6 to 8 show the second embodiment. The second embodiment shown in Figures 6 to 8 differs mainly in that the imaging unit 50 first images the diffractive optical element sheet 80 in a first direction, and then images it again in a second direction rotated 90° with respect to the first direction. The other configurations are substantially the same as those of the first embodiment described above. In Figures 6 to 8, the same reference numerals are used for parts that are the same as those in the first embodiment shown in Figures 1 to 5, and detailed descriptions are omitted. 【0075】 As shown in Figure 6, in the inspection apparatus 10 according to this embodiment, the light projection unit 30 is not provided with a polarization control unit 33. Therefore, the inspection light L from the laser light source 32 passes through the diffractive optical element sheet 80 without its polarization state being changed and reaches the imaging unit 50. For example, if the inspection light L from the laser light source 32 is linearly polarized laser light, linearly polarized inspection light L is incident on the imaging unit 50. The other configurations of the inspection apparatus 10 are substantially the same as in the first embodiment. 【0076】 Next, we will describe the operation of this embodiment, which has the above configuration. Specifically, we will explain the inspection method using the inspection device 10 according to this embodiment. 【0077】 First, as in the first embodiment, the diffractive optical element sheet 80 is attached to the holder 90 outside the inspection device 10. Next, the holder 90 and the diffractive optical element sheet 80 are placed inside the cassette buffer 75 of the inspection device 10. 【0078】 Next, the holder 90 and the diffractive optical element sheet 80 are held in the holding unit 20. At this time, the transport device 70 removes the holder 90 and the diffractive optical element sheet 80 from the cassette buffer 75. Then, the transport device 70 holds the holder 90 and the diffractive optical element sheet 80 in a predetermined position on the transport stage 21 of the holding unit 20. 【0079】 At this time, the reference side surface 80a of the diffractive optical element sheet 80 is facing the first direction. Here, the reference side surface 80a refers to one side surface of the diffractive optical element sheet 80 that serves as a reference for determining the orientation. The side surface of the diffractive optical element sheet 80 refers to the surface located around the sheet surface of the diffractive optical element sheet 80. The reference side surface 80a of the diffractive optical element sheet 80 may be perpendicular to the sheet surface. The first direction refers to the direction in a plane parallel to the sheet surface of the diffractive optical element sheet 80. For example, as shown in Figure 7(a), in the first direction, the reference side surface 80a of the diffractive optical element sheet 80 faces vertically upward. 【0080】 Next, as in the first embodiment, the holder 90 and the diffractive optical element sheet 80 are moved to the confirmation position. Then, the position confirmation camera 25 is used to determine the amount of displacement of the diffractive optical element sheet 80 relative to the holder 90, and the positioning of the holder 90 and the diffractive optical element sheet 80 is performed. 【0081】 Next, as in the first embodiment, each chip 81 of the diffractive optical element sheet 80 is individually spot-irradiated with inspection light L. As described above, the inspection light L from the laser light source 32 reaches the imaging unit 50 without any change in its polarization state. The imaging unit 50 transmits an image of the inspection light L that has passed through the diffractive optical element sheet 80 facing the first direction to the control unit 60. 【0082】 Next, the holder 90 and the diffractive optical element sheet 80 held in the holding unit 20 are removed, and the diffractive optical element sheet 80 is rotated 90° with respect to the first direction. At this time, the reference side surface 80a of the holder 90 and the diffractive optical element sheet 80 faces the second direction. Then, the diffractive optical element sheet 80, which is facing the second direction, is held in a predetermined position on the transport stage 21 of the holding unit 20. The operation of rotating the reference side surface 80a of the diffractive optical element sheet 80 90° from the first direction may be performed by the transport device 70 or manually. Here, the second direction refers to the direction in which the reference side surface 80a of the diffractive optical element sheet 80 is rotated 90° from the first direction, with the normal to the sheet surface of the diffractive optical element sheet 80 as the central axis. For example, as shown in Figure 7(b), in the second direction, the reference side surface 80a of the diffractive optical element sheet 80 faces sideways, that is, to the left in Figure 7(b). 【0083】 Next, as in the first embodiment, the holder 90 and the diffractive optical element sheet 80 are moved to the confirmation position. Then, the position confirmation camera 25 is used to determine the amount of displacement of the diffractive optical element sheet 80 relative to the holder 90. Subsequently, the holder 90 and the diffractive optical element sheet 80 are positioned. 【0084】 Next, as in the first embodiment, each chip 81 of the diffractive optical element sheet 80 is individually spot-irradiated with inspection light L. At this time, the inspection light L from the laser light source 32 reaches the imaging unit 50 without any change in its polarization state. The imaging unit 50 transmits an image of the inspection light L that has passed through the diffractive optical element sheet 80 facing the second direction to the control unit 60. 【0085】 Next, the control unit 60 inspects each chip 81 based on the image of the diffractive optical element sheet 80 taken in a first direction and the image of the diffractive optical element sheet 80 taken in a second direction. For example, the control unit 60 may calculate the average value of the intensity of the inspection light L passing through the dots of each chip 81 when taken in the first direction and the intensity of the inspection light L passing through the dots of each chip 81 when taken in the second direction. This average value of the intensity of the inspection light L may be used as the light distribution intensity of the dots of each chip 81. 【0086】 For example, consider a case where 11 chips 81a to 81k are arranged on a diffractive optical element sheet 80, as shown in Figures 8(a) and 8(b). Figure 8(a) shows the case where the diffractive optical element sheet 80 is oriented in a first direction. Figure 8(b) shows the case where the diffractive optical element sheet 80 is oriented in a second direction. In this case, the intensity of the inspection light L passing through the dots of a predetermined chip 81a to 81k in the first direction shown in Figure 8(a) and the intensity of the inspection light L passing through the same dot in the second direction shown in Figure 8(b) may be averaged and used as the light distribution intensity of the dot. 【0087】 After the inspection of the diffractive optical element sheet 80 is completed in this manner, the transport device 70 automatically removes the holder 90 and the diffractive optical element sheet 80 held in the holding unit 20. Then, the transport device 70 returns the holder 90 and the diffractive optical element sheet 80 to the cassette buffer 75. 【0088】 As described above, according to this embodiment, the control unit 60 inspects each chip 81 based on an image of the diffractive optical element sheet 80 taken in a first direction and an image of the diffractive optical element sheet 80 taken in a second direction. This allows each chip 81 to be inspected without being affected by the polarization state of the inspection light L. In particular, even if the polarization state of the inspection light L from the laser light source 32 differs from the polarization state of the light source part of the product, the diffractive optical element sheet 80 can be inspected without being affected by the polarization state of the inspection light L. Therefore, the accuracy of the inspection results by the inspection device 10 can be improved. 【0089】 [Examples] Next, Figures 9(a) and 9(b) show the results of measuring the efficiency for each dot on each chip in the first and second embodiments. In Figures 9(a) and 9(b), the horizontal axis represents the dot number from 1 to 99, and the vertical axis represents the efficiency in %. Here, efficiency is a value that represents the ratio of the output value of each dot to the input value of the inspection light L for each chip. 【0090】 Figure 9(a) shows the results of measuring the efficiency for each dot on each chip in the first embodiment. In this case, the polarization control unit changes the polarization state of the inspection light L from linear polarization to circular polarization. In Figure 9(a), the efficiency values ​​when the polarization state is changed by the polarization control unit are shown by the thick line. 【0091】 Figure 9(b) shows the results of measuring the efficiency for each dot of each chip in the second embodiment. In Figure 9(b), the efficiency values ​​measured in the first direction are shown by thin lines, and the efficiency values ​​measured in the second direction are shown by dashed lines. In Figure 9(b), the average value of the efficiency values ​​measured in the first direction and the efficiency values ​​measured in the second direction is shown by a thick line. 【0092】 As shown in Figure 9(a), when the polarization state was changed by the polarization control unit and the efficiency was measured, and as shown in Figure 9(b), when the efficiency measured in the first direction and the second direction were averaged, almost the same results were obtained. 【0093】 The multiple components disclosed in each of the above embodiments and variations can be combined as needed. Alternatively, some components may be removed from all the components shown in each of the above embodiments and variations. [Explanation of symbols] 【0094】 10 Inspection equipment 20 Holding part 21 Transport Stages 22 Drive unit 25 Location tracking camera 30. Light-emitting section 31 cabinets 32 Laser light sources 33 Polarization control unit 34 Collimator Lens 35 Variable aperture 36 ND filter 37 Beam Splitter 40 Status Monitoring Unit 41 Integrating sphere 42 Polarization Measuring Instrument 43 Beam Profiler 50 Photography Department 51 Collimator lens 52 Cameras 60 Control Unit 61 Imaging Control Unit 62 Evaluation Department 70 Conveying device 75 Cassette Buffer 80 Diffraction Optical Element Sheet 81 chips, unit diffractive optical elements 82 Diffractive optical element region 83 Alignment Marks 90 Holder 91 Holder opening 93 Standard Mark

Claims

[Claim 1] An inspection device for inspecting a diffractive optical element sheet in which multiple unit diffractive optical elements are arranged within the sheet surface, A holding portion for holding the diffractive optical element sheet, The holding portion is equipped with a light-emitting unit that emits polarized inspection light onto the diffractive optical element sheet held in the holding portion, A camera unit for capturing the inspection light that has passed through the diffractive optical element sheet, The system includes a control unit that acquires an image of the diffractive optical element sheet from the imaging unit and inspects each unit diffractive optical element based on the image, A polarization control unit is positioned between the laser light source and the diffractive optical element sheet. The polarization control unit is a paddle-type polarization controller in the inspection device. [Claim 2] The inspection apparatus according to claim 1, wherein the polarization control unit changes the linearly polarized inspection light to circularly polarized light. [Claim 3] The polarization control unit changes the polarization state of the inspection light, The inspection apparatus according to claim 1 or 2, wherein the control unit inspects each unit diffracting optical element based on the inspection light whose polarization state has been changed by the polarization control unit. [Claim 4] The diffractive optical element sheet has a reference side surface that determines the orientation, The imaging unit first images the diffractive optical element sheet with the reference side facing the first direction, and then images the diffractive optical element sheet with the reference side facing the second direction, which is rotated 90° with respect to the first direction. The inspection apparatus according to claim 1, wherein the control unit inspects each unit diffractive optical element based on an image of the diffractive optical element sheet taken in the first direction and an image of the diffractive optical element sheet taken in the second direction. [Claim 5] The inspection apparatus according to any one of claims 1 to 4, wherein a state monitoring unit for monitoring the state of the inspection light is provided between the laser light source and the diffractive optical element sheet. [Claim 6] The aforementioned diffractive optical element sheet is attached to a holder, The diffractive optical element sheet, while attached to the holder, is housed in the cassette buffer. The inspection apparatus according to any one of claims 1 to 5, further comprising a transport device for transporting the diffractive optical element sheet, which is attached to the holder, between the cassette buffer and the holding portion. [Claim 7] The inspection apparatus according to claim 6, wherein the diffractive optical element sheet is provided with alignment marks for positioning the holder and the diffractive optical element sheet. [Claim 8] The inspection apparatus according to any one of claims 1 to 7, wherein the paddle-type polarization controller is a three-paddle type polarization controller. [Claim 9] The inspection apparatus according to claim 8, wherein the three-paddle polarizing controller has, in order, a quarter-wave plate, a half-wave plate, and a quarter-wave plate. [Claim 10] An inspection method for inspecting a diffractive optical element sheet in which multiple unit diffractive optical elements are arranged within the sheet surface, The step of holding the diffractive optical element sheet in the holding part, The process involves projecting polarized inspection light from a light-emitting unit having a laser light source onto the diffractive optical element sheet held in the holding unit, A step of capturing the inspection light that has passed through the diffractive optical element sheet, The process includes acquiring an image of the diffractive optical element sheet that has been photographed, and inspecting each unit diffractive optical element based on the image, The process includes changing the polarization state of the inspection light from linearly polarized to circularly polarized using a paddle-type polarization controller between the laser light source and the diffractive optical element sheet, The aforementioned paddle-type polarization controller is an inspection method that changes the polarization state of light by stress on a fiber. [Claim 11] The inspection method according to claim 10, wherein the step of inspecting each unit diffracting optical element includes the step of inspecting each unit diffracting optical element based on the inspection light whose polarization state has changed. [Claim 12] The diffractive optical element sheet has a reference side surface that determines the orientation, The aforementioned process of taking photographs is A step of photographing the diffractive optical element sheet with the reference side facing the first direction, The process includes taking a photograph of the diffractive optical element sheet with its reference side facing a second direction rotated 90° with respect to the first direction, The inspection method according to claim 10, wherein the step of inspecting each unit diffractive optical element includes the step of inspecting each unit diffractive optical element based on an image of the diffractive optical element sheet taken in the first direction and an image of the diffractive optical element sheet taken in the second direction. [Claim 13] The inspection method according to any one of claims 10 to 12, further comprising the step of monitoring the state of the inspection light between the laser light source and the diffractive optical element sheet. [Claim 14] The aforementioned diffractive optical element sheet is attached to a holder, The diffractive optical element sheet, while attached to the holder, is housed in the cassette buffer. The inspection method according to any one of claims 10 to 13, further comprising the step of transporting the diffractive optical element sheet, which is attached to the holder, between the cassette buffer and the holding part. [Claim 15] Alignment marks are provided on the diffractive optical element sheet for positioning the holder and the diffractive optical element sheet. The inspection method according to claim 14, further comprising the step of positioning the holder and the diffractive optical element sheet. [Claim 16] The inspection method according to any one of claims 10 to 15, wherein the paddle-type polarization controller is a three-paddle type polarization controller. [Claim 17] The inspection method according to claim 16, wherein the three-paddle polarizing controller has, in order, a quarter-wave plate, a half-wave plate, and a quarter-wave plate.

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