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 configured to project 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. The image capturing unit 50 output brightness of each of the unit diffraction optical elements 81, and the control unit 60 corrects a brightness value of each of the unit diffraction optical elements 81 according to a diffraction angle of the inspection light L incident on the unit diffraction optical element 81.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 a target irradiation region.

[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 any 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 a 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 surfaces on a single substrate, a large number of optical elements can be manufactured from a single substrate. The optical elements mounted on multiple surfaces 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 emitting unit for projecting inspection light onto the diffractive optical element sheet held by the holding unit, a shooting unit for capturing the inspection light transmitted through the diffractive optical element sheet, and a control unit for acquiring an image of the diffractive optical element sheet from the shooting unit and inspecting each unit diffractive optical element based on the image, wherein the shooting unit outputs the brightness of each unit diffractive optical element, and the control unit corrects the brightness value for each unit diffractive optical element according to the diffraction angle of the inspection light incident on the unit diffractive optical element.

[0010] In the inspection apparatus according to this embodiment, the control unit may correct the luminance value for each unit diffracting optical element by multiplying the luminance value by a correction coefficient corresponding to the diffraction angle of the inspection light.

[0011] 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, comprising the steps of: holding the diffractive optical element sheet; emitting inspection light onto the held diffractive optical element sheet; photographing the inspection light transmitted 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, wherein in the step of photographing the inspection light, the brightness of each unit diffractive optical element is output, and in the step of inspecting each unit diffractive optical element, the value of the brightness is corrected for each unit diffractive optical element according to the diffraction angle of the inspection light incident on the unit diffractive optical element.

[0012] In the inspection method according to this embodiment, in the step of inspecting each unit diffractive optical element, the brightness value may be corrected for each unit diffractive optical element by multiplying the brightness value by a correction coefficient corresponding to the diffraction angle of the inspection light. [Effects of the Invention]

[0013] According to this embodiment, diffractive optical element sheets can be inspected easily and with high precision. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic plan view showing an inspection device according to one embodiment. [Figure 2] Figure 2 is a front view showing the holder and the diffractive optical element sheet. [Figure 3] Figure 3 is a schematic cross-sectional view showing a part of an inspection device according to one embodiment, along the optical path of the inspection light. [Figure 4] Figure 4 shows an image captured of the inspection light that passed through the chip. [Figure 5] Figures 5(a)-(c) illustrate an inspection method according to one embodiment. [Figure 6] Figure 6 is a graph showing the results of pre-measurement of the intensity of the inspection light incident on the chip using an integrating sphere. [Figure 7]FIG. 7(a) is a graph showing the actually measured values of the luminance for each spot of the chip, and FIG. 7(b) is a graph showing the corrected luminance values for each spot of the chip.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, an embodiment will be described with reference to FIGS. 1 to 7. In the following figures, the same parts are denoted by the same reference numerals, and some detailed descriptions may be omitted.

[0016] FIG. 1 is a schematic plan view showing an inspection apparatus according to the present embodiment. Note that each of the figures shown below, including FIG. 1, is a schematically shown figure, and the sizes and shapes of each part are exaggerated as appropriate for easy understanding. In the following description, specific numerical values, shapes, materials, etc. are shown for the description, but these can be changed as appropriate. In this specification, terms specifying shapes and geometric conditions, such as terms like parallel and orthogonal, in addition to their strict meanings, also include states having errors that allow them to be regarded as parallel or orthogonal while exhibiting similar optical functions. In this specification, words such as plate, sheet, and film are used. In general usage, they are used in the order of plate, sheet, and film in descending order of thickness, and this specification also follows this usage. Since there is no technical meaning in such a distinction, these words can be replaced as appropriate. In this specification, the sheet surface refers to the surface in the planar direction of the sheet when viewed as the entire sheet. The same applies to the plate surface and the film surface. Also, in this specification, transparent means a material that transmits at least light of the wavelength to be used. For example, even if it does not transmit visible light, if it transmits infrared light, it is treated as transparent when used for infrared applications.

[0017] As shown in FIG. 1, the inspection apparatus 10 according to the present embodiment is an apparatus for inspecting a diffractive optical element sheet 80 in which a plurality of unit diffractive optical elements are arranged in a sheet plane. In the present embodiment, the case where the unit diffractive optical element is a chip 81 will be described as an example. The inspection apparatus 10 includes a holding unit 20, a light projecting unit 30, a photographing unit 50, and a control unit 60.

[0018] The holding unit 20 detachably holds the diffractive optical element sheet 80. The diffractive optical element sheet 80 is detachably attached to a holder 90. The inspection apparatus 10 inspects the diffractive optical element sheet 80 in a state where it is attached to the holder 90.

[0019] The holding unit 20 holds the diffractive optical element sheet 80 in a state where it is attached to the holder 90. The holding unit 20 may hold the holder 90 and the diffractive optical element sheet 80 movably. The holding unit 20 holds the diffractive optical element sheet 80 such that the sheet plane of the diffractive optical element sheet 80 is along the vertical direction.

[0020] Next, the diffractive optical element sheet 80 will be described. As shown in FIG. 2, the diffractive optical element sheet 80 is a so-called multi-sided sheet, film, or plate in which a plurality of chips 81 are arranged. In the diffractive optical element sheet 80, a plurality of chips 81 are arranged in a state before being separated. After being individualized, the chip 81 is attached to, for example, a light source unit of a sensor and used. In each chip 81, a diffractive optical element region 82 is located at substantially the center thereof. A pattern of a fine concavo-convex shape is formed in the diffractive optical element region 82. The diffractive optical element region 82 has an effect of diffracting and emitting light of a predetermined wavelength and shaping the light. The diffractive optical element region 82 functions as a Diffractive Optical Element or DOE. In FIG. 2, for ease of understanding and to make the figure easy to view, the diffractive optical element sheet 80 is illustrated with the chips 81 arranged in three rows each in the vertical and horizontal directions, but actually, a larger number of chips are arranged.

[0021] 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.

[0022] 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.

[0023] The light-emitting unit 30 emits inspection light L onto the 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 collimator lens 34, a variable aperture 35, and an ND filter 36. The laser light source 32, collimator lens 34, variable aperture 35, and ND filter 36 are each located within the housing 31. Furthermore, the collimator lens 34, variable aperture 35, and ND filter 36 are arranged in this order along the direction of propagation of the inspection light L from the laser light source 32.

[0024] 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 may be a polarized laser. For example, the laser light from the laser light source 32 may be a linearly polarized laser.

[0025] The collimator lens 34 is lit by inspection light L from the laser light source 32. The collimator lens 34 is a lens that corrects the inspection light L emitted by the laser light source 32 into parallel light.

[0026] 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.

[0027] The inspection light L that has passed through the variable aperture 35 is incident on the ND filter 36. The ND filter 36 reduces the amount of inspection light L regardless of its wavelength. The inspection light L that has passed through the ND filter 36 is incident on the diffractive optical element sheet 80.

[0028] 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, the camera 52 may have a solid-state image sensor such as a CMOS image sensor. 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. The imaging unit 50 outputs the brightness of each chip 81 captured by the camera 52 and transmits it to the control unit 60.

[0029] The control unit 60 includes an imaging control unit 61, a correction unit 63, and an evaluation unit 62. Of these, the imaging control unit 61 controls the imaging unit 50 to perform imaging when the inspection light L is projected onto the chip 81. As a result, the imaging control unit 61 performs imaging of the inspection light L. The imaging control unit 61 also images the diffractive optical element sheet 80 held in the holding unit 20. At this time, the diffractive optical element sheet 80 may be imaged by the imaging unit 50 while stationary.

[0030] For example, the imaging control unit 61 controls the camera to take a picture when the light spot S from the light emitter 30 is in the center of one chip 81, as shown in Figure 2. The imaging control unit 61 then repeatedly moves and stops the holding unit 20, sequentially taking pictures of other adjacent chips 81. Here, the imaging control unit 61 calculates the position of the chip 81 using pre-set positioning information and alignment information, and determines the timing for taking the picture. Furthermore, for imaging of chips 81 aligned in at least one direction, the imaging control unit 61 may continue moving the holding unit 20 while taking pictures with the imaging unit 50. In this case, only the center of the chip 81 may be photographed, or other areas may also be photographed. For example, if the camera 52 has a solid-state image sensor such as a CMOS image sensor, the camera 52 may photograph one chip 81 at a time. In this case, the imaging control unit 61 photographs the diffractive optical element sheet 80 held by the holding unit 20 a number of times corresponding to the number of chips 81. The imaging unit 50 transmits the image, including the captured chip 81, to the correction unit 63.

[0031] The correction unit 63 corrects the brightness value for each chip 81 according to the diffraction angle of the inspection light L incident on the chip 81. Specifically, the correction unit 63 corrects the brightness value for each chip 81 by multiplying the brightness value obtained from the imaging unit 50 by a correction coefficient corresponding to the diffraction angle of the inspection light L. Details of the correction method by the correction unit 63 will be described later.

[0032] The evaluation unit 62 inspects each chip 81 based on the brightness value of each chip 81 corrected by the correction unit 63. For example, the evaluation unit 62 evaluates the light distribution characteristics of the chip 81 based on the image information corrected by the correction unit 63. 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 being inspected is looking for.

[0033] Figure 4 shows an image captured by the imaging unit 50 of the image transmitted through the chip 81 of the diffractive optical element sheet 80. The chip 81 splits the incident inspection light L into multiple beams and distributes it to multiple different locations. In the example in Figure 4, the light is split into nine spots P1 to P9 arranged in three rows vertically and horizontally, and distributed in a square shape.

[0034] 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.

[0035] First, as shown in Figure 5(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).

[0036] Next, as shown in Figure 5(b), the holder 90 and the diffractive optical element sheet 80 are held in the holding section 20 of the inspection device 10. At this time, the holder 90 and the diffractive optical element sheet 80 may be held in the holding section 20 using a transport device such as an industrial robot (not shown). Alternatively, the holder 90 and the diffractive optical element sheet 80 may be held in the holding section 20 by hand.

[0037] Next, as shown in Figure 5(c), the inspection light L is spot-irradiated onto the diffractive optical element sheet 80. At this time, the inspection light L is projected from the light-emitting unit 30, which has a laser light source 32, onto the diffractive optical element sheet 80 held in the holding unit 20.

[0038] During this time, as shown in Figure 3, inspection light L is first emitted from the laser light source 32. This inspection light L enters the collimator lens 34. 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 the light intensity is reduced by the ND filter 36.

[0039] Subsequently, the inspection light L 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.

[0040] 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.

[0041] The camera 52 of the imaging unit 50 may simultaneously photograph multiple spots P1 to P9 of each chip 81. In this case, it is preferable to photograph all spots P1 to P9 included in each chip 81. The imaging unit 50 outputs the brightness of spots P1 to P9 of each chip 81 and transmits it to the control unit 60. The correction unit 63 of the control unit 60 corrects the brightness value for each chip 81 according to the diffraction angle of the inspection light L incident on spots P1 to P9 of the chip 81.

[0042] The method of correction by the correction unit 63 will be explained further below.

[0043] First, a correction coefficient is determined for all spots P1 to P9 on the chip 81, corresponding to the diffraction angle of the inspection light L. This correction coefficient value is stored in the control unit 60.

[0044] For example, consider the case where the diffractive optical element sheet 80 has nine spots P1 to P9, as shown in Figure 4. Furthermore, assume that the diffraction angle θ5 of the inspection light L incident on the central spot P5 among the nine spots P1 to P9 is 0°. The diffraction angles of the inspection light L incident on each of the spots P1 to P9 are denoted as θ1 to θ9.

[0045] Next, the intensity of the inspection light L incident on each spot P1 to P9 is measured using an integrating sphere (not shown). Figure 6 is a graph showing the results of measuring the intensity of the inspection light L incident on each spot P1 to P9 using the integrating sphere beforehand. Based on the integrating sphere intensity measured using this integrating sphere, a correction coefficient is determined. The correction coefficient is calculated by constructing a model equation and examining the correlation between the measured integrating sphere intensity and the luminance value. The correction coefficient may also be defined by, for example, the following formula. Correction factor = 1 / (cosθ) p Here, θ is the diffraction angle of the inspection light L incident on each spot P1 to P9 of the chip 81. p is the cosθ power coefficient and takes the same value for all spots P1 to P9.

[0046] After determining the correction coefficient in this manner, the actual brightness value is measured for each spot P1 to P9 of the chip 81, and the obtained brightness value is corrected. Specifically, the control unit 60 determines a correction coefficient for each spot P1 to P9 of the chip 81, corresponding to the angles θ1 to θ9, which are the diffraction angles θ of the inspection light L, i.e., 1 / (cosθ) p The value of is multiplied by the luminance value obtained by the imaging unit 50. This corrects the luminance value obtained by the imaging unit 50. Specifically, let C be the measured luminance value obtained by the imaging unit 50, and the corrected luminance value is C A Therefore, C A It can be obtained by the following formula. C A =(1 / (cosθ) p )×C

[0047] Figure 7(a) is a graph showing the luminance values ​​obtained by the imaging unit 50, i.e., the measured values, for each spot P1 to P9 of the chip 81. Figure 7(b) is a graph showing the corrected luminance values ​​for each spot P1 to P9 of the chip 81, multiplied by the correction coefficient. As shown in Figure 7(b), it can be seen that the corrected luminance values ​​for each spot P1 to P9 of the chip 81 have a shape similar to the graph measured using an integrating sphere, as shown in Figure 6.

[0048] In addition, the brightness mentioned above may be calculated using integrated brightness. Integrated brightness refers to the sum of the brightness values ​​of the dots contained in each spot P1 to P9 of the chip 81.

[0049] 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.

[0050] As described above, according to this embodiment, the imaging unit 50 outputs the brightness of each spot P1 to P9 of the chip 81. The control unit 60 corrects the brightness value for each spot P1 to P9 of the chip 81 according to the diffraction angle of the inspection light L incident on the spot P1 to P9 of the chip 81. In this case, it is possible to suppress variations in brightness values ​​that depend on the diffraction angle of the inspection light L. In particular, even when the diffraction angle or incident angle of the inspection light L is large, it is possible to reduce variations in brightness captured by the camera 52. For this reason, multiple spots P1 to P9 of the chip 81 can be captured simultaneously using the imaging unit 50. This eliminates the need to perform measurements for each spot P1 to P9 using an integrating sphere or the like, and allows the inspection by the inspection device 10 to be performed efficiently in a short amount of time.

[0051] It is also possible to combine the multiple components disclosed in each of the above embodiments and variations as needed. Alternatively, some components may be removed from all the components shown in each of the above embodiments and variations. [Explanation of Symbols]

[0052] 10 Inspection equipment 20 Holding part 21 Transport Stages 22 Drive unit 30. Light-emitting section 31 cabinets 32 Laser light sources 34 Collimator Lens 35 Variable aperture 36 ND filter 50 Photography Department 51 Collimator lens 52 Cameras 60 Control Unit 61 Imaging Control Unit 62 Evaluation Department 63 Correction Unit 80 Diffraction Optical Element Sheet 81 chips, unit diffractive optical elements 82 Diffractive optical element region 90 Holder 91 Holder opening

Claims

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 diffractive optical element sheet held in the holding part is provided with a light-emitting unit that emits inspection light, 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, The imaging unit outputs the brightness of each unit diffracting optical element, The control unit corrects the brightness value for each unit diffracting optical element by multiplying the brightness value by a correction coefficient corresponding to the diffraction angle of the inspection light incident on the unit diffracting optical element. The aforementioned correction coefficient is calculated by the correlation between the integrating sphere intensity and brightness value of the measured data in the inspection device.

2. The correction coefficient is given by the following formula Correction factor = 1 / (cosθ)p (θ is the diffraction angle of the inspection light L incident on each spot of the unit diffracting optical element, and p is the cosθ power coefficient, which takes the same value for all spots.) The inspection apparatus according to claim 1, as defined by [the relevant law].

3. 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, The process involves projecting inspection light onto the held diffractive optical element sheet, 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, In the process of capturing the inspection light, the brightness of each unit diffracting optical element is output, Beforehand, we measured the actual data using an integrating sphere. A correction coefficient is determined by the correlation between the integrating sphere intensity and brightness value of the measured data. An inspection method comprising the step of inspecting each of the aforementioned unit diffractive optical elements, wherein for each unit diffractive optical element, the value of the brightness is corrected by multiplying the value of the brightness by a correction coefficient corresponding to the diffraction angle of the inspection light incident on the unit diffractive optical element.

4. The correction coefficient is given by the following formula Correction factor = 1 / (cosθ)p (θ is the diffraction angle of the inspection light L incident on each spot of the unit diffracting optical element, and p is the cosθ power coefficient, which takes the same value for all spots.) The inspection method according to claim 3, as defined by [the relevant law].

Images