Optical measuring device

Abstract

To provide an optical measuring device capable of highly accurately measuring temporal change in output light from an optical element and measuring a far-field image like diffraction light without being influenced by noise.SOLUTION: An optical measuring device 1 comprises: a collimator lens 22 which collimates light L0, light L1, or light L2 to be measured; a prism group 4 which emits the light emitted from the collimator lens 22 from an emission position where the distance from an optical axis is greater than a position on an extension of the light; and a first imaging element 60 in which photodetectors 6 for receiving light emitted from the prism group 4 are arranged. The prism group 4 comprises a first prism 41 which emits light at an emission angle greater than its incident angle without diffusing it, and a second prism 42 which emits the light emitted from the first prism 41 at an emission angle smaller than its incident angle.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an optical measurement device that measures a light pattern output from an optical element. [Background technology]

[0002] In recent years, with the improvement of the performance of semiconductor processes, the miniaturization and density of optical integrated circuits have progressed. Accordingly, optical elements in which output light interferes due to a microstructure, such as an optical modulation element, an optical phased array (OPA), an arrayed waveguide grating (AWG), a photonic crystal, a metasurface, etc., have appeared. In the optical performance evaluation of such optical elements, the optical pattern at the output part of the light (near field pattern; NFP) and the optical pattern observed at a distance from the output part (far field pattern; FFP) are mainly observed. In order to measure these optical patterns, an apparatus combining optical elements such as a plurality of lenses and an image sensor (camera) such as a CCD is used. An apparatus that switches between a near-field image and a far-field image by removing some lenses and forms an image with an image sensor (for example, Non-Patent Document 1) and an apparatus that is equipped with a beam splitter and two image sensors and can simultaneously measure a near-field image and a far-field image have been disclosed (for example, Patent Documents 1 and 2).

[0003] Furthermore, in Patent Document 1, the divergence angle of the output beam of the optical deflection element can be measured by observing a far-field pattern in which stray light is separated by a pinhole plate, and in Patent Document 2, the beam shape of the beam output from a part of the waveguides selected by a spatial filter can be measured. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-115249 A [Patent Document 2] JP 2020-98102 A [Non-patent literature]

[0005] [Non-Patent Document 1] NL Thomas, R. Houdre, M. Kotlyar, D. O'Brien, T. Krauss, "Exploring light propagating in photonic crystals with Fourier optics", Journal of the Optical Society of America, B, Volume 24, No. 12, p. 2964-2971, 2007 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, in the optical performance evaluation of an optical deflection element that controls the direction of a beam, it is required to measure not only the static shape of the beam but also the scanning speed of the beam sweep. However, a light receiving element with high time resolution such as a photodetector cannot obtain high spatial resolution like a CCD image sensor, so it is not possible to measure the deflection angle with high precision, and as a result, it is difficult to measure the scanning speed with high precision. Alternatively, if photodetectors are arranged for each of two or more specific deflection angles, when the difference between the deflection angles is small, such as a few degrees, a photodetector with a large package size requires a long distance from the optical deflection element, which reduces the amount of light received by the photodetector and reduces accuracy. In addition, if there is a small error in the deflection angle, the photodetector will not receive light, making evaluation difficult.

[0007] In addition, since an optical deflection element using an optical phased array generates a beam by interfering light output from each of a plurality of waveguides, the output light may have a plurality of peaks, and the main lobe with the highest output is used as the beam. Therefore, the evaluation target is exclusively the main lobe, and other side lobes become noise and are desirably removed. Similarly, diffracted light output from a diffraction grating or the like may be evaluated only for low-order light (e.g., zeroth order light, first order light), which has a relatively high output, and it is desirably possible to remove high-order light. The pinhole plate and spatial filter of Patent Documents 1 and 2 are intended to remove light other than that to be evaluated near the output section where the light is output, and are not intended to filter diffracted light.

[0008] The present invention has been devised in view of the above problems, and an object of the present invention is to provide an optical measuring device that is suitable for dynamic evaluation, such as temporal changes in output light, in evaluating the optical performance of optical elements, and that can measure far-field patterns, such as diffracted light, without being affected by noise. [Means for solving the problem]

[0009] In other words, the optical measurement device of the present invention comprises a collimating optical system that collimates the light to be measured, a diverging optical system that outputs the light emitted from the collimating optical system at a wider distance from the optical axis, and a first imaging element having two or more light receiving elements arranged in one or more one- or two-dimensions that receive the light emitted from the diverging optical system, wherein the diverging optical system comprises a diverging optical element that outputs the light at an exit angle larger than its incident angle without diffusing the light, and a corrective optical element that outputs the light emitted from the diverging optical element at an exit angle smaller than its incident angle. Effect of the Invention

[0010] According to the optical measurement device of the present invention, the beam angle of the light to be measured can be changed more greatly, so that a light receiving element such as a photodetector whose spatial resolution is not high relative to its time resolution can be used to perform dynamic evaluation with high accuracy, and the far-field pattern can be measured without being affected by noise. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating an overall shape of an optical measuring device according to the present invention. [Diagram 2] FIG. 1 is a schematic diagram illustrating a structure of an optical measurement device according to a first embodiment of the present invention. [Figure 3A] 2 is a schematic diagram illustrating a measurement method using the optical measuring device shown in FIG. 1. [Figure 3B] 2 is a schematic diagram illustrating a measurement method using the optical measuring device shown in FIG. 1. [Figure 4] FIG. 4 is a schematic diagram for explaining the structure of an optical measurement device according to a first modified example of the first embodiment of the present invention. [Diagram 5] FIG. 13 is a schematic diagram illustrating the structure of an optical measuring device according to a second modified example of the first embodiment of the present invention. [Figure 6] FIG. 13 is a schematic diagram illustrating the structure of an optical measuring device according to a third modified example of the first embodiment of the present invention. [Figure 7] FIG. 13 is a schematic diagram illustrating the structure of an optical measurement device according to a fourth modified example of the first embodiment of the present invention. [Figure 8] 5A and 5B are schematic diagrams illustrating the structure of an optical measurement device according to a second embodiment of the present invention. [Figure 9] 13A and 13B are schematic diagrams illustrating the structure of an optical measuring device according to a modified example of the second embodiment of the present invention. [Figure 10] 13A and 13B are schematic diagrams illustrating the structure of an optical measuring device according to a third embodiment of the present invention. [Figure 11] 13 is a schematic diagram illustrating the structure of an optical measurement device according to a fourth embodiment of the present invention. FIG. [Figure 12]4 is an image of a sample simulating the optical measurement device according to the first embodiment of the present invention, and an image of a simulated optical path of a beam. [Figure 13A] 13 is an image of a sample simulating an optical measurement device according to a second embodiment of the present invention, and an optical path of a simulated beam. [Figure 13B] FIG. 11B is an enlarged view of the vicinity of the light source side in FIG. 11A. [Figure 14] 13 is an image of a sample simulating an optical measurement device according to a modified example of the second embodiment of the present invention, and an image of a simulated optical path of a beam. [Figure 15A] 13 is an image illustrating a sample simulating an optical measurement device according to a modified example of the second embodiment of the present invention, and explaining the range of beam incidence angles in a simulation. [Figure 15B] 13 is an image illustrating a sample simulating an optical measurement device according to a modified example of the second embodiment of the present invention, and explaining the range of beam incidence angles in a simulation. [Figure 16] 13 is an image of a sample simulating an optical measurement device according to a third embodiment of the present invention, and an optical path of a simulated beam. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment for realizing the optical measurement device according to the present invention will be described with reference to the drawings. The optical measurement device 1 according to the present invention measures the pattern shape and temporal change of light outputted from a light source LS by using an optical element OE such as an optical deflection element or a diffraction grating as an evaluation object, and for example, as shown in FIG. 1, includes two image pickup elements 60, 81 for picking up a far-field image of the output light. The optical measurement device 1 is connected to or placed close to the light output part of the optical element OE, inputs the output light of the optical element OE, and acquires an electric signal by connecting an oscilloscope OSC or a personal computer PC to the image pickup elements 60, 81. The light source LS is a device that irradiates light of a wavelength, coherence (or incoherence), and output corresponding to the optical element OE, and is, for example, a laser light source. The optical element OE is driven by a current source CS as necessary. The oscilloscope OSC is a known device, and acquires the electric signal of each of the photodetectors (light receiving elements) 6 (see FIG. 2) of the first image pickup element 60. The PC is connected to the second imaging element 81 and the OSC to analyze the acquired image and electrical signals. The PC may also be connected to a current source CS to control the optical element OE and further to control the light source LS, as necessary. The optical measurement device and its elements shown in the drawings may be exaggerated in size and positional relationship, and may be simplified in shape and structure, for clearer explanation. In the explanation of each embodiment, the same reference numerals are used for the same elements as in the previous embodiment, and explanations are omitted as appropriate.

[0013] [First embodiment] (Optical Measuring Device) 2, the optical measurement device 1 according to the first embodiment of the present invention includes a collimating lens (collimating optical system) 22, a prism group (diverging optical system) 4 consisting of a first prism (diverging optical element) 41 and a second prism (correcting optical element) 42, a first imaging element 60 in which photodetectors (light receiving elements) 6 are linearly arranged, and preferably further includes a condensing lens (condensing optical system) 5. The optical measurement device 1 may further include a collimating lens 21, a beam splitter (light branching element) 31, an imaging lens (imaging optical system) 71, and a second imaging element 81. In detail, the optical measurement device 1 is provided with a collimator lens 21, a collimator lens 22, a beam splitter 31, a first prism 41, a second prism 42, a condenser lens 5, and a first image pickup element 60 arranged in order from the side of the optical element OE to be evaluated, i.e., the light incident side, and further includes an imaging lens 71 and a second image pickup element 81 arranged in order from the side of the beam splitter 31 in the direction of branching of light by the beam splitter 31. Each of these elements provided in the optical measurement device 1 is adapted to the wavelength of light input to the optical measurement device 1, i.e., the light output from the optical element OE, and is housed in a housing as shown in FIG.

[0014] In the optical measurement device 1 according to this embodiment, the optical element OE to be evaluated is a one-dimensional optical deflection element, and measures the shape of the output beam, the deflection angle θ, the scanning speed of the beam sweep, etc. The optical deflection element (optical element OE) scans a beam in the X direction centered on the Z axis, and is configured, for example, with a planar optical waveguide circuit (PLC: Planar Lightwave Circuit) in which multiple optical waveguides are arranged side by side on a substrate.

[0015] The collimating lens 21 and the collimating lens (collimating optical system) 22 are optical elements that convert diffused light into parallel light (collimate). The collimating lenses 21 and 22 may have a known configuration, for example, an aspheric lens or two or more spherical lenses may be applied, and these may be combined. Each lens may be a single lens made of one piece of glass, or an achromatic lens made by bonding two or more materials with different refractive indexes. The collimating lens 22 may be a plano-convex lens with a flat exit surface, and may be in close contact with a cube-shaped beam splitter 31 described later. In the optical measurement device 1, the collimating lens 21 is configured and arranged so as to convert the light in the near-field image NFP of the light output from the optical element OE into parallel light with a desired beam diameter, and is arranged on the optical element OE side relative to the far-field image FFP. On the other hand, the collimating lens 22 is configured and arranged so as to convert the light beams L0, L1, and L2 of the far-field pattern FFP of the light output from the optical element OE into parallel light beams having a desired beam diameter d. Furthermore, the collimating lens 22 is detachably provided in the optical measurement device 1.

[0016] The beam splitter (optical branching element) 31 is an optical element that branches incident light into two different directions. Specifically, the beam splitter 31 branches the incident light into light that passes through without changing its traveling direction and light that is reflected and changes its traveling direction (for example, light with an incident angle of 0° changes by 90°) and is emitted. Such beam splitter 31 can be a known non-polarized plate-type or cube-type beam splitter. The light quantity branching ratio of the reflected light and the transmitted light in the beam splitter 31 is not particularly limited, and may be a 1:1 half mirror, or one of the reflected light and the transmitted light may be relatively high-output, and is preferably selected according to the sensitivity of each of the imaging elements 60 and 81. In FIG. 2, the beam splitter 31 reflects light in the X direction (downward in the figure), but may be arranged to reflect light in the Y direction (perpendicular to the paper surface in the figure). By including the beam splitter 31, the optical measurement device 1 can simultaneously observe the far-field pattern FFP of the optical element OE by the photodetector 6 of the first imaging element 60 with high time resolution and the second imaging element 81 with high spatial resolution.

[0017] The prism group (divergence optical system) 4 outputs the light L1, L2 of the far-field pattern FFP, which has been converted into parallel light by the collimator lens 22, at a greater distance from the optical axis (Z axis, shown by a dashed line in the figure), that is, away from the optical axis. In detail, the prism group 4 outputs the light from an output position that is farther away from the optical axis than the output position when the light travels straight. However, the prism group 4 causes the light L0 with an incident angle (deflection angle of the optical element OE) of 0° on the optical axis (Z axis) to travel straight on the optical axis. The incident position and the output position of the prism group 4 are positions on the imaginary entrance surface 4i and output surface 4e of the prism group 4, which are perpendicular to the optical axis. In addition, the absolute value |θe| (≧0°) of the output angle θe of the light from the prism group 4 is preferably equal to or less than the incident angle θi (=θ), and more preferably closer to 0°.

[0018] Here, three light beams, namely, light L0 with an incident angle of 0° on the optical axis (Z-axis), light L1 with an incident angle of θ1, and light L2 with an incident angle of θ2 (0°<θ1<θ2), are incident on the prism group 4 at distances 0, x1i ,x 2i The beam enters the position (0 <x 1i <x 2i ) Distance from the optical axis 0,x 1e ,x 2e If the distance from the entrance surface 4i of the prism group 4 to the exit surface 4e is represented by Δz, the distance from the optical axis to the exit position on the exit surface 4e when the light L1 and L2 travel in a straight line (shown by the two-dot chain line in FIG. 2) (hereinafter, appropriately referred to as the distance of the exit position) is respectively x 1i +Δz tan θ1, x 2i +Δz tanθ2. However, due to the prism group 4, as mentioned above, x 1e >x 1i +Δz tan θ1, x 2e >x 2i +Δz tanθ2, and further, x 2e -x 1e >(x 2i +Δz tanθ2)-(x 1i +Δz tan θ1). That is, the prism group 4 diverges the light away from the optical axis and widens the interval between the lights with different angles of incidence before outputting them. The light beams L0, L1, and L2 of the far-field pattern FFP are collimated by the collimator lens 22 through the prism group 4 and further the condenser lens 5 described below, and are then received by the photodetector 6 of the first image sensor 60 without being diffused.

[0019] The prism group 4 includes a first prism 41 that does not diffuse light and emits the light at an emission angle larger than the incident angle, and a second prism 42 that emits the light emitted from the first prism 41 at an emission angle smaller than the incident angle. The first prism 41 and the second prism 42 each emit the light at a maximum incident angle (deflection angle of the optical element OE) θ max It is sized so that light (>0°) enters the entrance surface and exits from the exit surface.

[0020] The first prism (divergent optical element) 41 outputs the light, which has been converted into parallel light by the collimator lens 22, at an exit angle θe' larger than the magnitude of the incident angle θi (>0°) as parallel light (θi<θe'). However, the light L0 with an incident angle of 0° on the optical axis (Z axis) is made to travel straight. An example of such an optical element is an axicon lens, which is a rotationally symmetric prism. Furthermore, in this embodiment, since the light whose deflection angle of the optical element OE changes one-dimensionally (X direction) is the measurement target, the first prism 41 can also be a plane-symmetric prism (plane-symmetric prism) with a plane (ZY plane) including the optical axis (Z axis) as the symmetry plane. The first prism 41 has an entrance surface 41i that is a concave inclined surface and an exit surface that is a plane (vertical surface) perpendicular to the optical axis. If it is an axicon lens (plano-concave axicon lens), the entrance surface 41i is a conical surface, and if it is a plane-symmetric prism, it is a plane inclined in the XZ direction. However, in order to make the light L0 on the Z axis go straight, the first prism 41 has a vertical incidence surface in a predetermined area centered on the optical axis, or a through hole along the optical axis is formed, and if it is a plane-symmetric prism, two prisms are arranged plane-symmetrically with a gap between them. This predetermined area is equal to or larger than the beam diameter d and has a minimum incidence angle θ min In other words, the first prism 41 is designed so that light having an incident angle θ (>0°) on the incident surface 41i is incident on the incident surface (inclined surface) 41i. min The incident position of the light is positioned at a distance of d / 2 or more from the Z axis.

[0021] The first prism 41 is configured so that, as described above, θ1<θ1e', θ2<θ2e', and θ1e'<θ2e' are satisfied for the light L1 and L2 with the incident angles θ1 and θ2 (θ1<θ2). Furthermore, it is preferable that θ1e'-θ1≦θ2e'-θ2, and it is more preferable that θ1e'-θ1<θ2e'-θ2, and it is even more preferable that the difference between them is larger. With this configuration, when the light L1 and L2 are emitted from the first prism 41, they proceed with a wider distance between each other. The inclination angle (apex angle) α1 of the incident surface 41i and the refractive index n1 of the material of the first prism 41 are designed so that the difference (deviation angle) δ1 between the incident angle θi (=θ) and the exit angle θe' increases as the incident angle θi increases. The larger the apex angle α1 is, and the higher the refractive index n1 is, the larger the deviation angle δ1 is. Furthermore, if the refractive index n1 is high, the deviation angle δ1 can be made larger as the incident angle θi increases. Therefore, it is preferable that the first prism 41 is made of a highly refractive material. Note that, depending on the apex angle α1 and the refractive index n1 of the first prism 41, light with a large incident angle cannot be transmitted through the first prism 41. In other words, the limit (maximum) incident angle θ of the measurement target of the optical measurement device 1 max However, this may be limited by the structure of the first prism 41.

[0022] The second prism (compensating optical element) 42 outputs the light output from the first prism 41 at an output angle θe smaller than the magnitude of the incident angle θe' (>0°) (θe'>θe). Furthermore, the output angle θe of the second prism 42 is preferably equal to or smaller than the incident angle θi to the first prism 41 (θi≧θe), and more preferably closer to 0°. Note that, like the first prism 41, the second prism 42 causes the light L0 with an incident angle of 0° on the optical axis (Z axis) to travel straight. As such an optical element, like the first prism 41, there is an axicon lens, which is a rotationally symmetric prism. Furthermore, the collecting lens 5 described later may also serve as the second prism (compensating optical element) 42. In this embodiment, the measurement target is light whose deflection angle of the optical element OE changes in one dimension (X direction), so that the second prism 42 may be a plane-symmetric prism like the first prism 41. The second prism 42 has a vertical entrance surface and a convex inclined exit surface 42e. If it is an axicon lens (plano-convex axicon lens), the exit surface 42e is a conical surface, and if it is a plane-symmetric prism, it is a flat surface inclined in the XZ direction. However, in order to make the light L0 on the Z axis travel in a straight line, the second prism 42 has a vertical exit surface in a predetermined region centered on the optical axis, or a through hole is formed along the optical axis, and if it is a plane-symmetric prism, two prisms are arranged symmetrically with a gap between them. This predetermined region is equal to or larger than the beam diameter d and has a minimum incidence angle θ min The inclined surface 42e is designed to have a range such that the light is emitted from the inclined surface 42e.

[0023] As described above, the second prism 42 is configured so that θe≦θi, and therefore the deviation angle δ2 is set to be equal to or larger than the deviation angle δ1 of the first prism 41 (δ1≦δ2). For example, if the second prism 42 has a structure in which the inclination angle (apex angle) α2 of the exit surface 42e and the refractive index n2 of the material are the same as the apex angle α1 and the refractive index n1 of the first prism 41, then θi=θe. Regardless of the incidence angle θi to the first prism 41, i.e., regardless of the incidence angle θe′ to the second prism 42, in order to bring the exit angle θe closer to 0°, the second prism 42 lowers the refractive index n2 to a certain degree, while increasing the apex angle α2 so that the deviation angle δ2 is larger than the deviation angle δ1 of the first prism 41. Also, as the distance between the first prism 41 and the second prism 42 becomes longer, the exit position x of the light L1, L2 becomes smaller. 1e ,x 2e The prism group 4 is designed such that the structures (refractive index of material, apex angle) and the distance between the prisms 41, 42 are designed so that the emitted light beams L1, L2 are received by different photodetectors 6 on the first imaging element 60 via the subsequent condenser lens 5. The prisms 41, 42 may be provided so as to be movable in the optical axis (Z-axis) direction, making their positions adjustable.

[0024] The condenser lens (condensing optical system) 5 condenses the light L0, light L1, or light L2 emitted from the prism group 4 onto the photodetector 6 of the first imaging element 60. The condenser lens 5 is provided as necessary, and is not necessary if the beam diameter d of the light L0, L1, and L2 by the collimator lens 22 is small enough to be received by the photodetector 6. In this embodiment, the condenser lens 5 further changes the emission angle so that the light L1 and L2 are incident on the photodetector 6, on its light receiving surface (light receiving area), and within a predetermined incident angle range. It is preferable that the incident angle range is set to a range in which the incident angle dependency of the photodetector 6 is sufficiently low. In other words, the condenser lens 5 can be said to be a part of the prism group (diverging optical system) 4 that compensates for the second prism (correcting optical element) 42. For this reason, the condenser lens 5 has a diameter that faces all the photodetectors 6 of the first imaging element 60. The condenser lens 5 may have a known configuration, may be a combination of one or more lenses, may be a single lens, or may be an achromatic lens. Furthermore, in this embodiment, since the measurement target is light whose deflection angle of the optical element OE changes one-dimensionally (X direction), a cylindrical lens or a rod lens may be applied to the condenser lens 5. Furthermore, the condenser lens (condensing optical system) may be configured by arranging small-diameter lenses facing each of the photodetectors 6 (see the second, third, and fourth embodiments), or may be combined with an array of small-diameter lenses on the light emission side of the condenser lens 5.

[0025] The first imaging element 60 includes an array of photodetectors (light receiving elements) 6, any one of which captures light L0, L1, and L2 of the far-field pattern FFP. In this embodiment, the measurement target is light whose deflection angle of the optical element OE changes one-dimensionally (X direction), so the first imaging element 60 includes photodetectors 6 arranged in a row in the X direction, with an odd number of photodetectors centered on one on the Z axis. In FIG. 2, the first imaging element 60 includes seven photodetectors 6 arranged at equal intervals. With such a first imaging element 60, the optical measuring device 1 can measure three stages of deflection angles θ of the optical element OE other than 0°.

[0026] The photodetector 6 is an element that converts an optical signal into an electric signal, and as described above, a known one corresponding to the wavelength of the light output from the optical element OE is applied. In the visible light region, a CCD sensor or a CMOS sensor can be applied, and in the infrared region, for example, an InGaAs sensor can be applied. The photodetector 6 has a time resolution required for measurement, and the response speed is preferably several hundred MHz or more, although it varies depending on the sensor size, etc. In addition, a photodetector with a fiber can be applied as the photodetector 6. In this case, a commercially available fiber coupler may be used on the fiber side to replace the condenser lens 5. In the first imaging element 60, the photodetectors 6 are arranged at a pitch of, for example, 10 mm to several tens of mm corresponding to the package size, etc., and are not limited to being arranged at equal intervals, and can be arranged according to the incidence position of each light of the optical element OE with different deflection angles θ on the first imaging element 60. Note that in FIG. 2, only the light receiving surface (light receiving area) of the photodetector 6 is shown. The smaller the arrangement pitch of the package size or the like of the photodetector 6, the smaller the first imaging element 60 can be, and the smaller the optical measurement device 1 can be. Also, the larger the light receiving surface of the photodetector 6 per arrangement pitch, the larger the measurement can be even if the error in the deflection angle θ of the optical element OE is.

[0027] The imaging lens (imaging optical system) 71 forms an image from the parallel light on the light receiving surface of the second imaging element 81. The imaging lens 71 may have a known configuration, for example, an aspheric lens or two or more spherical lenses, or these may be combined. Each lens may be a single lens made of a single piece of glass, or an achromatic lens made by bonding two or more materials with different refractive indices together.

[0028] The second imaging element 81 is a two-dimensional sensor having light receiving elements arranged two-dimensionally, and receives light L of the near-field image NFP. NOr, the second imaging element 81 captures one of the light beams L0, L1, and L2 of the far-field image FFP. As described above, the second imaging element 81 can be a known imaging element corresponding to the wavelength of the light output from the optical element OE, and a CCD image sensor or a CMOS image sensor can be applied in the visible light region, and an InGaAs sensor, for example, can be applied in the infrared region. A mixed sensor may be used to support multiple wavelengths. Also, the sensor has a required number of pixels, pixel pitch, etc. Also, a frame rate, which is a response speed, of up to about 120 Hz can be applied. A method in which the second imaging element 81 selects and captures one of the near-field image NFP or the far-field image FFP will be described later.

[0029] The optical measurement device 1 can also be configured so that the transmitted light of the beam splitter 31 is incident on the second imaging element 81, and the reflected light is incident on the first imaging element 60. That is, the optical measurement device 1 can have the prism group 4, the condenser lens 5, and the first imaging element 60, and the imaging lens 71 and the second imaging element 81 interchangeably arranged.

[0030] (Operation of optical measuring device) The operation of the optical measurement device according to the first embodiment of the present invention will be described with reference to Fig. 2, Fig. 3A, and Fig. 3B. For the sake of simplicity, Fig. 3A and Fig. 3B show the imaging lens 71 and the second imaging element 81 arranged so that the transmitted light of the beam splitter 31 is incident thereon, and only the light L0 with a deflection angle of 0° is shown for the far-field pattern FFP output from the optical element OE. When light is input from the light source LS to the optical element OE, the optical element OE outputs the light L0 of the near-field pattern NFP. N , and outputs either light L0, light L1, or light L2 as the far-field pattern FFP.

[0031] 2 and 3A, the light L0, light L1, or light L2 of the far-field pattern FFP is converted into parallel light with a beam diameter d by the collimator lens 22 and travels at deflection angles of 0°, θ1, or θ2. The light L0, L1, or L2 is then split into two directions by the beam splitter 31. One of the lights L0, L1, or L2 forms an image on the light receiving surface of the second image sensor 81 by the imaging lens 71. The second image sensor 81 captures the light L0, light L1, or light L2, and the beam shape and deflection angle θ are analyzed by the PC.

[0032] The other light L0, light L1, or light L2 split by the beam splitter 31 enters the prism group 4. The light L0 with a deflection angle (incident angle) of 0° travels straight along the optical axis of the prisms 41 and 42 of the prism group 4 and is transmitted therethrough, is collected by the condenser lens 5, and is incident on and received by the photodetector 6 on the Z axis of the first imaging element 60. The light L1 and L2 travel in the prism group 4 so that their optical paths move away from the Z axis according to the respective incident angles θ1 and θ2, and are further adjusted in their traveling direction and collected by the condenser lens 5, and are incident on and received by the different photodetector 6 in the first imaging element 60. The OSC detects the photocurrent of the photodetector 6, and the PC analyzes the switching speed between the light L0 and the light L1, the light L0 and the light L2, or the light L1 and the light L2, i.e., the scanning speed.

[0033] On the other hand, as shown in Fig. 3A, the light L of the near-field pattern NFP N is collimated by the collimator lens 21, but is diffused by the collimator lens 22 arranged on the exit side thereof, and is not imaged by the imaging lens 71 on the light receiving surface of the second imaging element 81. Therefore, imaging of the far-field pattern FFP is not hindered in the second imaging element 81. The same is true for the first imaging element 60 (photodetector 6).

[0034] In order to observe the near-field pattern NFP, the collimator lens 22 (indicated by a two-dot chain line in the drawing) is removed from the optical measurement device 1 as shown in FIG. 3B. Then, the light L of the near-field pattern NFP is Nis converted into parallel light by the collimator lens 21 and enters the imaging lens 71 as is to form an image on the light receiving surface of the second imaging element 81. On the other hand, the light L0 (L1, L2) of the far-field image FFP travels as diffuse light and is not imaged on the light receiving surface of the second imaging element 81 by the imaging lens 71. Therefore, imaging of the near-field image NFP is not hindered in the second imaging element 81.

[0035] It is preferable that the optical measuring device 1 is designed, for example, so that light with a deflection angle θ in the far-field pattern FFP in increments of 5°, i.e., light with θ = 0°, 5°, 10°, 15°, ... is received by different photodetectors 6 of the first imaging element 60, and further so that θ is each received by the same photodetector 6 within an error range (e.g., ±1°).

[0036] The optical measurement device 1 according to this embodiment may be configured so that an optical deflection element that scans a beam two-dimensionally (XY directions) can also be evaluated. In such a configuration, the first prism 41 and the second prism 42 of the prism group 4 are each an axicon lens. The first imaging element 60 includes photodetectors 6 arranged two-dimensionally, for example, in a square lattice pattern in the XY directions, or on concentric circles centered on the Z axis.

[0037] According to the optical measuring device 1 of this embodiment, the light L0, L1, and L2 of the far-field pattern FFP can be received by the photodetector 6 corresponding to the deflection angle with a relatively short optical path length, and the scanning speed of the beam sweep can be measured with high accuracy without increasing the size of the device. Furthermore, in the optical measuring device 1, after the light L0, L1, and L2 are made parallel by the collimating lens 22, they are incident on the photodetector 6 without diffusing, so that the measurement can be performed with high optical efficiency. Furthermore, the optical measuring device 1 can simultaneously observe the far-field pattern FFP of the optical element OE with the first imaging element 60 and the second imaging element 81, which are completely different in the arrangement pitch and light receiving area of ​​the elements, without providing a large number of optical elements or making the structure complex or dense.

[0038] In the optical measurement device 1 according to this embodiment, the collimating lens 21 may be disposed on the output side of the light of the far-field pattern FFP, and in this case, the collimating lens 22 is combined with the collimating lens 21 to collimate the light in the far-field pattern FFP. Also, the optical measurement device 1 may split the light of the far-field pattern FFP by a beam splitter 31 before collimating it (see the modified examples and the third and fourth embodiments described later).

[0039] The optical measurement device 1 may be configured to observe only the far-field pattern FFP (not the near-field pattern NFP), in which case the collimator lens 21 may not be provided, and the collimator lens 22 may not be removable. Furthermore, the optical measurement device 1 may be configured not to observe the near-field pattern NFP, and not to observe using the second imaging element 81. Such an optical measurement device 1 may not include the collimator lens 21, the second imaging element 81, the imaging lens 71, and the beam splitter 31, that is, it includes the collimator lens 22, the prism group 4, the condenser lens 5, and the first imaging element 60.

[0040] (Modification) The optical measuring device according to the first embodiment can switch between observing the far-field image and the near-field image of the output light of the optical element to be evaluated by attaching and detaching a part of the optical element (collimator lens), but can also be configured to observe the far-field image and the near-field image simultaneously. Hereinafter, an optical measuring device according to a modified example of the first embodiment of the present invention will be described with reference to Figs. 4, 5, 6, and 7.

[0041] 4, the optical measurement device 10 according to the first modified example of the first embodiment of the present invention includes a collimator lens 21, a collimator lens (collimator optical system) 22, a prism group (divergence optical system) 4, a condenser lens (condenser optical system) 5, a first imaging element 60, beam splitters (light branching elements) 31 and 32, imaging lenses (imaging optical systems) 71 and 72, a second imaging element 81, and a third imaging element 82. In detail, the optical measurement device 10 includes the collimator lens 21, the beam splitter 32, the collimator lens 22, the beam splitter 31, the prism group 4 (first prism 41, second prism 42), the condenser lens 5, and the first imaging element 60 arranged in this order from the optical element OE side. Furthermore, an imaging lens 71 and a second image pickup element 81 are arranged in this order from the beam splitter 31 side in the direction of branching of light by the beam splitter 31, and an imaging lens 72 and a third image pickup element 82 are arranged in this order from the beam splitter 32 side in the direction of branching of light by the beam splitter 32. That is, the optical measurement device 10 has a configuration in which the beam splitter 32 is added between the collimator lens 21 and the collimator lens 22 to the optical measurement device 1 according to the above embodiment, and the imaging lens 72 and the third image pickup element 82 are added in the direction of branching of light by the beam splitter 32.

[0042] The beam splitter 32 can be configured similarly to the beam splitter 31. In FIG. 4, the beam splitters 31 and 32 are arranged so as to reflect light downward, but they may be arranged in different directions, and may be reflected upward or in a direction perpendicular to the plane of the drawing. The imaging lens 72 and the third imaging element 82 can be configured similarly to the imaging lens 71 and the second imaging element 81, respectively. In this modification, the second imaging element 81 captures a far-field image FFP, and the third imaging element 82 captures a near-field image NFP. In this modification, the collimator lens 22 does not need to be removable.

[0043] In the optical measurement device 10, the light L of the near-field pattern NFP is collimated by the collimator lens 21. Nis split by the beam splitter 32, and the transmitted light or reflected light (reflected light in FIG. 4) is imaged by the imaging lens 72 on the light receiving surface of the third imaging element 82. According to the optical measurement device 10 of this modification, the near-field pattern NFP and far-field pattern FFP of the optical element OE can be observed simultaneously, and further, similar to the first embodiment, the far-field pattern FFP can be observed by the first imaging element 60 and the second imaging element 81. Note that, in this modification as well, the transmitted light and reflected light of the beam splitter 31 can be interchanged, and the transmitted light and reflected light of the beam splitter 32 can be interchanged.

[0044] 5, a beam splitter 32 may be disposed on the light exit side of the collimator lens 22. In such an optical measurement device 10A, the light L of the near-field pattern NFP that has been diffused by the collimator lens 22 is N The third imaging element 82 includes an imaging lens 72A that forms an image of the reflected light on the light receiving surface of the third imaging element 82.

[0045] As shown in FIG. 6, the light L0 (L1, L2) of the far-field pattern FFP is collimated by the collimator lens 22B, and the light L N 7, a beam splitter 31 may be disposed on the light incident side of the collimator lens 22B, and the light L0 (L1, L2) of the far-field image FFP may be imaged on the light receiving surface of the second image pickup element 81 by the imaging lens 71A.

[0046] Second Embodiment The optical measurement device according to the first embodiment measures light by making it enter different photodetectors depending on the deflection angle of the measurement object, but it can also be configured to measure light with a deflection angle other than 0° by making it enter the same photodetector.

[0047] (Optical Measuring Device) 8, the optical measuring device 1A according to the second embodiment of the present invention is different from the optical measuring device 1 according to the first embodiment in that it includes a prism group (diverging optical system) 4A consisting of a first prism 41A and a second prism 42A instead of the prism group 4, and a collecting lens (collecting optical system) 5A instead of the collecting lens 5. In this embodiment, the first imaging element 60 includes three photodetectors 6 arranged at equal intervals in the X direction.

[0048] The prism group (divergence optical system) 4A, like the prism group 4 of the first embodiment, emits the light L1 and L2 of the far-field pattern FFP, which has been made parallel by the collimator lens 22, away from the optical axis (Z-axis), and causes the light L0 with an incident angle (deflection angle of the optical element OE) of 0° on the optical axis (Z-axis) to travel straight. However, it is preferable that the prism group 4A has the emission positions of the light L1 and L2 with incident angles other than 0° closer to each other. Such a prism group 4A is obtained by designing the refractive index and apex angle of the material of each of the first prism 41A and the second prism 42A, and the distance between them. In addition, the lens 5a of the condenser lens 5A described later may also serve as the second prism (corrective optical element) 42A. In addition, the second prism (corrective optical element) 42A may be an annular cylindrical lens with at least a region of beam diameter d centered on the Z-axis, or may be combined with an axicon lens.

[0049] When the measurement target is light in which the deflection angle of the optical element OE changes in one dimension (X direction), the second prism (compensating optical element) 42A can be a plane-symmetric prism as in the first embodiment, or two lenses (or two sets of lenses) arranged plane-symmetrically can be used. When a lens is used as the compensating optical element 42A, the two lenses (or two sets of lenses) are arranged symmetrically with a region of at least the beam diameter d centered on the Z axis. The lenses can be spherical lenses, aspherical lenses, cylindrical lenses, or rod lenses.

[0050] The condenser lens (condensing optical system) 5A condenses the light L0, light L1, or light L2 emitted from the prism group 4A onto the photodetector 6 of the first imaging element 60. The condenser lens 5A further causes the light L1 and L2 with an incident angle other than 0° to be incident onto the same photodetector 6 in the first imaging element 60. For this purpose, the condenser lens 5A includes an array of small-diameter lenses 5a facing each of the photodetectors 6. The lens 5a may have a known configuration, and may be a combination of one or more lenses, or may be a single lens or an achromatic lens. Furthermore, when the measurement target is light whose deflection angle of the optical element OE changes one-dimensionally (X direction), the lens 5a may be a cylindrical lens or a rod lens.

[0051] (Operation of optical measuring device) The operation of the optical measurement device according to the second embodiment of the present invention is similar to that of the first embodiment. However, in this embodiment, the prism group 4A receives the light L0 with an incident angle of 0°, and the other light in the + direction and - direction, respectively, at different photodetectors 6. Therefore, it is possible to measure the speed at which the incident angle switches between 0° and the other incident angles, i.e., the scanning speed.

[0052] In the optical measuring device 1A according to this embodiment, the configuration and arrangement of the prism group 4A (prisms 41A, 42A) and the condenser lens 5A can be designed so that, for example, light with a deflection angle θ of approximately 5° to approximately 15° is incident on the first photodetector 6 (excluding on the Z axis) from the Z axis side, and light with a deflection angle θ of approximately 20° to approximately 30° is incident on the second photodetector 6 (not shown). In this way, the optical measuring device 1A receives light with an incident angle within a certain range on the same photodetector 6, and can reduce the number of parts compared to the first embodiment, making it possible to have a simpler structure, and can measure the deflection angle and scanning speed with high accuracy in combination with analysis by the second imaging element 81.

[0053] (Modification) In the optical measurement device according to the second embodiment, the first prism of the prism group (divergence optical system) may have a convex inclined entrance surface. As shown in the first and second embodiments, the larger the entrance angle of light incident on a first prism having a concave inclined entrance surface, the larger the exit angle from the first prism. In contrast, in a prism having a convex inclined entrance surface, the magnitude relationship between the entrance angle and the exit angle is reversed.

[0054] As shown in FIG. 9, an optical measuring device 1B according to a modified example of the second embodiment of the present invention is different from the optical measuring device 1A according to the second embodiment in that it has a prism (diverging optical element) 43B instead of the prism group 4A and a collecting lens (correcting optical element, collecting optical system) 5B instead of the collecting lens 5A, and the prism 43B and the collecting lens 5B form a diverging optical system 4B.

[0055] The diverging optical system 4B, like the prism group (diverging optical system) 4A of the second embodiment, emits the light beams L1 and L2 of the far field pattern FFP, which have been collimated by the collimator lens 22, with angles of incidence other than 0°, away from the optical axis (Z axis) and moves the emission positions closer to each other. The diverging optical system 4B includes, in order from the light incident side, a prism 43B and a condenser lens 5B.

[0056] Prism (divergent optical element) 43B outputs the light, which has been collimated by collimator lens 22, at an exit angle θe' with an absolute value greater than the magnitude of the incident angle θi (>0°) while keeping the light parallel (θi<|θe'|). However, light L0 with an incident angle of 0° on the optical axis (Z-axis) is caused to travel straight. Prism 43B is further configured so that, as described above, for lights L1 and L2 with incident angles θ1 and θ2 (θ1<θ2), θ1<|θ1e'|, θ2<|θ2e'|, and |θ1e'|>|θ2e'|. Furthermore, it is preferable that θ2-θ1≧|θ1e'|-|θ2e'|, and it is more preferable that θ2-θ1>|θ1e'|-|θ2e'|. As such an optical element, an axicon lens can be used, as in the first prisms 41 and 41A of the first and second embodiments, and a plane-symmetric prism can also be used when only one dimension (X direction) is to be measured. However, the prism 43B has an entrance surface that is a convex inclined surface and an exit surface that is a plane (vertical surface) perpendicular to the optical axis. On the other hand, the prism 43B has an entrance surface that is a vertical surface in a predetermined region centered on the optical axis in order to make the light L0 on the Z axis travel straight, as in the first prism 41, and has an isosceles trapezoidal cross-sectional shape. The prism 43B inverts the traveling direction of the light on either side of the optical axis (Z axis). That is, the light with an entrance angle θi of + (θi>0°) has an exit angle θe′ of − (θe′<0°).

[0057] The condenser lens (corrective optical element, condensing optical system) 5B emits the light emitted from the prism 43B at an emission angle θe (|θe'|>|θe|) whose absolute value is smaller than the incidence angle θe' (≠0°). The absolute value of the emission angle θe of the condenser lens 5B is preferably equal to or smaller than the incidence angle θi of the prism 43B (θi≧|θe|), and more preferably closer to 0°. Note that the condenser lens 5B, like the prism 43B, causes the light L0 with an incidence angle of 0° on the optical axis (Z axis) to travel straight. As such an optical element, the condenser lens 5B, which is also a condensing optical system, can be applied. The condenser lens 5B can be configured similarly to the condenser lens 5 of the first embodiment. The condenser lens 5B causes the light L1 and L2 to travel while approaching each other so as to be incident on the same photodetector 6 in the first imaging element 60 and to be condensed. The optical measurement device 1B may further include a condenser lens 5A in which lenses 5a facing each of the photodetectors 6 are arranged as a condenser optical system.

[0058] As described above, the diverging optical system 4B is designed with the refractive index and apex angle of the material of the prism 43B, the focal length of the condenser lens 5B, the distance between the prisms 43B, and the like, so that the light L1 and L2 with angles other than 0° are condensed onto the same photodetector 6 in the first imaging element 60. Note that as the apex angle of the prism 43B increases, the limit (maximum) incidence angle θ of the measurement target of the optical measurement device 1 decreases. max becomes smaller.

[0059] (Operation of optical measuring device) The operation of the optical measurement device according to the modified example of the second embodiment of the present invention is similar to that of the second embodiment (see FIG. 8). However, in this modified example, the traveling direction of light is inverted across the optical axis (Z-axis) by prism 45B, so that light with an incident angle other than 0° is received by photodetector 6 on the opposite side of the optical axis, as compared to the second embodiment. Also, in this modified example, for light whose incident angle (deflection angle) of the measurement target is greater than a certain value, the distance from the optical axis at the emission position may be shortened by diverging optical system 4B.

[0060] The optical measuring devices 1A and 1B according to the second embodiment and its modified examples are configured to include a beam splitter 32, a third imaging element 82, and an imaging lens 72, etc., like the optical measuring devices 10, 10A, 10B, and 10C according to the modified examples of the first embodiment (see Figures 4 to 7), and can also simultaneously observe the near-field image NFP and far-field image FFP of the optical element OE.

[0061] Third Embodiment It is also possible to configure the light to be measured to be all along an optical path in the 0° direction at a distance from the optical axis according to the deflection angle, and then move the optical paths away from each other so that they are incident on different photodetectors.

[0062] (Optical Measuring Device) 10, an optical measurement device 1C according to a third embodiment of the present invention includes a beam splitter (light branching element) 31, a parabolic mirror 24, a collimating lens (collimating optical system) 22a, a prism group (diverging optical system) 4C consisting of prisms 43, 44, 45, and 46, a first image pickup element 60 in which photodetectors (light receiving elements) 6 are two-dimensionally arranged, and preferably further includes a condenser lens (condensing optical system) 5A. The optical measurement device 1C may further include collimating lenses 21 and 23, an imaging lens (imaging optical system) 71, and a second image pickup element 81. In detail, the optical measuring device 1C is equipped with, arranged in order from the side of the optical element OE to be evaluated, i.e., the light incident side, a collimating lens 21, a beam splitter 31, a parabolic mirror 24, a collimating lens 22a, a third prism 45, a second prism 44, a first prism 43, a fourth prism 46, a focusing lens 5A, and a first imaging element 60, and further equipped with, arranged in order from the beam splitter 31 side in the direction of branching of light by the beam splitter 31, a collimating lens 23, an imaging lens 71, and a second imaging element 81.

[0063] The parabolic mirror 24 directs the light beams L0, L1, L2, and L3 having different deflection angles of the far field pattern FFP of the optical element OE in the same traveling direction (0° in this case) but on different optical paths; more specifically, the larger the deflection angle, the longer the optical path from the optical axis (Z axis; indicated by the dashed line in the drawing). The light beams L0, L1, L2, and L3 are in order of smallest deflection angle, and the light beam L0 with a deflection angle of 0° has an optical path on the optical axis. The parabolic mirror 24 can have a known configuration in which the mirror surface (reflecting surface) has a parabolic shape, and when only one dimension (X direction) is to be measured, the mirror surface may have a cylindrical shape (with a parabolic cross section). As in the first embodiment, the beam splitter 31 splits the light of the far-field pattern FFP and causes it to be incident simultaneously on the photodetector 6 of the first imaging element 60 and the second imaging element 81, and causes the light paths of the light incident on the parabolic mirror 24 from the optical element OE and the reflected light to differ. For this reason, the beam splitter 31 is disposed between the parabolic mirror 24 and the focal point F of its reflecting surface. In Fig. 10, the light output downward from the optical element OE is reflected by the beam splitter 31 and caused to be incident on the lateral (left) parabolic mirror 24, and the reflected light passes through the beam splitter 31 and travels to the right.

[0064] The collimating lens (collimating optical system) 22a is an optical element that converts the light reflected by the parabolic mirror 24 into parallel light, and is disposed on each optical path of the light L0, L1, L2, and L3 of the far-field pattern FFP reflected by the parabolic mirror 24. Since the spread angle of the light is reduced to a certain extent by the parabolic mirror 24, the collimating lens 22a is designed to convert the light L0, L1, L2, and L3 into parallel light in cooperation with the parabolic mirror 24. Furthermore, the collimating lens 22a has a diameter equal to or larger than the beam diameter of the incident light L0, L1, L2, and L3, and the resolution of the deflection angle θ decreases as the distance between the collimating lenses 22a becomes narrower. The collimator lenses 22a are provided in odd numbers with one centered on the optical axis of the parabolic mirror 24. In FIG. 10, seven collimator lenses 22a are provided in the X direction, and the optical measuring device 1C can measure three stages of deflection angles θ of the optical element OE other than 0°.

[0065] The collimating lens 23 collimates the light that is split by the beam splitter 31 and enters the second imaging element 81. The collimating lens 23 can have a configuration similar to that of the collimating lens 22 of the optical measuring device 1 according to the first embodiment, and further, like the collimating lens 22 in the optical measuring device 1, is provided detachably.

[0066] The prism group (divergence optical system) 4C widens the distance from the optical axis (Z-axis) of the light L0, L1, L2, and L3 of the far-field pattern FFP, which has been converted into parallel light in the optical axis direction (0°) by the parabolic mirror 24 and the collimator lens 22a. Furthermore, the prism group 4C increases the distance at the exit position of the light L0, L1, L2, and L3 as the distance from the optical axis at the entrance position increases. Note that the prism group 4C causes the light L0, L1, L2, and L3, which is a distance of 0, that is, traveling on the optical axis, to travel straight on the optical axis as it is. The entrance position and exit position of the prism group 4C are positions on the imaginary entrance surface 4i and exit surface 4e of the prism group 4C, which are perpendicular to the optical axis. Furthermore, it is preferable that the exiting light L0, L1, L2, and L3 of the prism group 4C are parallel to each other, and therefore the exit angle is set to 0°, which is the same as the entrance angle.

[0067] The prism group 4C is composed of first, second, and third prisms (diverging optical elements) 43, 44, and 45 that do not diffuse light and output the light at an output angle larger than the incident angle, and a fourth prism (correcting optical element) 46 that outputs the light output from the first, second, and third prisms 43, 44, and 45 at an output angle smaller than the incident angle. The prism group 4C includes the third prism 45, the second prism 44, the first prism 43, and the fourth prism 46 arranged in this order from the light incident side. Each of the prisms 43, 44, 45, and 46 can be an axicon lens, which is a rotationally symmetric prism, like the first prism 41 and the second prism 42 (see FIG. 2) in the first embodiment. Furthermore, when only one dimension (X direction) is to be measured, the prisms 43, 44, 45, and 46 may be plane-symmetric prisms with a plane (ZY plane) including the optical axis (Z axis) as the plane of symmetry.

[0068] The first, second and third prisms (divergent optical elements) 43, 44 and 45 each receive the light that has been collimated by the collimator lens 22a at an incident angle of 0°, bend it and emit it at a predetermined exit angle (>0°). The first prism 43 bends the light L1, the second prism 44 bends the light L2, the third prism 45 bends the light L3, and the other lights go straight. Therefore, the prisms 43, 44 and 45 all let the light L0 on the optical axis (Z axis) go straight. The entrance surface of the prisms 43, 44 and 45 is a convex inclined surface, and the exit surface is a flat surface (vertical surface) perpendicular to the optical axis. If it is an axicon lens (plano-convex axicon lens), the inclined surface is a conical surface, and if it is a plane-symmetric prism, it is a flat surface inclined in the XZ direction. However, in a predetermined region centered on the optical axis, the prisms 43, 44, and 45 have a vertical incident surface and an isosceles trapezoidal cross-sectional shape. The larger the inclination angle (apex angle) of the incident surface of the prisms 43, 44, and 45 is, and the higher the refractive index of the material is, the larger the exit angle becomes, but the apex angle is set to be less than the critical angle so that the incident light is not totally reflected. The prisms 43, 44, and 45 have the same refractive index and apex angle of the material so that the lights L1, L2, and L3 are each exited at the same exit angle θe.

[0069] The third prism 45, which is disposed on the most incident side, is designed so that the incident surface is a vertical surface in the region where the light L0, L1, and L2 are incident at an incident angle of 0°, and is an inclined surface in the region where the light L3 is incident. The second prism 44, which is disposed on the light exit side of the third prism 45, is designed so that the incident surface is a vertical surface in the region where the light L0 and L1 are incident at an incident angle of 0°, and is an inclined surface in the region where the light L2 is incident, and furthermore, is designed to have an outer diameter or an X-direction length such that the light L3 traveling in the θe direction is not incident. The first prism 43, which is disposed on the most exit side, is designed so that the incident surface is a vertical surface in at least a region of beam diameter d centered on the optical axis where the light L0 is incident, and is an inclined surface in the region where the light L1 is incident, and furthermore, is designed to have an outer diameter or an X-direction length such that the light L2 and L3 traveling in the θe direction are not incident.

[0070] The fourth prism (corrective optical element) 46 emits light at an exit angle smaller than the incident angle (>0°), and preferably has the same exit angle (0°) as the incident angle into the first, second, and third prisms 43, 44, and 45. The fourth prism 46 has a vertical entrance surface and a convex exit surface, and if it is an axicon lens (plano-convex axicon lens), the inclined surface is a cone surface, and if it is a plane-symmetric prism, the inclined surface is a plane inclined in the XZ direction. However, the fourth prism 46 has a vertical exit surface in at least a region of beam diameter d centered on the optical axis so that light L0 on the optical axis with an incident angle of 0° travels straight, and at least the region from which light L1, L2, and L3 are emitted is an inclined surface and has an isosceles trapezoidal cross-sectional shape. It is preferable that the fourth prism 46 has the same refractive index and apex angle as the prisms 43, 44, and 45, that is, the fourth prism 46 forms a prism pair with the first prism 43, the second prism 44, and the third prism 45. With this configuration, the angles of incidence to the first, second, and third prisms 43, 44, and 45 and the angle of emergence from the fourth prism 46 are the same value (0°).

[0071] As the interval between the first prism 43 and the fourth prism 46 becomes longer, the distance between the emission positions of the light L1 becomes larger. Similarly, as the interval between the second prism 44 and the fourth prism 46 and the interval between the third prism 45 and the fourth prism 46 become longer, the distance between the emission positions of the light L2 and the light L3 becomes larger. Therefore, the third prism 45, which bends the light L3 to maximize the distance between the emission position relative to the distance between the incidence position, is disposed on the most incident side, farthest from the fourth prism 46.

[0072] (Operation of optical measuring device) The operation of the optical measurement device according to the third embodiment of the present invention will be described with reference to FIG. As described in the first embodiment, when light is input from the light source LS, the optical element OE converts the light L N , and outputs either light L0, light L1, light L2, or light L3 as the far-field pattern FFP.

[0073] The light L0, light L1, light L2, or light L3 of the far-field image FFP is split into two directions by the beam splitter 31. One of the lights L0, L1, L2, and L3 is converted into parallel light with a predetermined beam diameter by the collimator lens 23, travels at the deflection angle, and is imaged on the light receiving surface of the second image sensor 81 by the imaging lens 71.

[0074] The other light L0, light L1, light L2, or light L3 split by the beam splitter 31 is reflected by the parabolic mirror 24, and exits in the 0° direction from the reflection position, enters each collimator lens 22a, becomes parallel light with a beam diameter d, and enters the prism group 4C. The light L0 on the optical axis (Z axis) travels straight through the prisms 45, 44, 43, and 46 of the prism group 4C, is collected by the condenser lens 5a on the Z axis, and enters and is received by the photodetector 6 on the Z axis of the first imaging element 60. The light L1 travels straight through the prisms 45 and 44, is bent by the first prism 43, exits at an exit angle θe, returns to the 0° direction by the fourth prism 46, and increases the distance from the optical axis, and enters the first photodetector 6 (excluding the one on the Z axis) from the Z axis side via the opposing condenser lens 5a. The light L2 travels straight through the third prism 45, is bent by the second prism 44, travels outside the first prism 43 so that its optical path moves away from the Z axis in the traveling direction θe, and enters the fourth prism 46, returning in the 0° direction. Then, it enters the second photodetector 6 from the Z axis side via the opposing condenser lens 5a. The light L3 is bent by the third prism 45, travels outside the prisms 44 and 43 so that its optical path moves away from the Z axis in the traveling direction θe, and enters the fourth prism 46, returning in the 0° direction. Then, it enters the third photodetector 6 from the Z axis side via the opposing condenser lens 5a.

[0075] As described in the first embodiment, the light L of the near-field pattern NFP N is converted into parallel light by the collimator lens 21, but passes through the beam splitter 31 and is converted into diffuse light by the collimator lens 23 arranged on the exit side thereof, so that the light is not imaged by the imaging lens 71 on the light receiving surface of the second imaging element 81. In order to observe the near-field image NFP, the collimator lens 23 is removed from the optical measurement device 1C.

[0076] When measuring light with two stages of deflection angles θ other than 0°, the optical measurement device 1C may include five collimator lenses 22a and the prism group 4C may include prisms 43, 44, and 46. On the other hand, by increasing the number of collimator lenses 22a and providing the prism group 4C with an additional prism that serves as a diverging optical element, it is possible to measure light with four or more stages of deflection angles θ.

[0077] Prism group 4C includes one prism 46 as a corrective optical element, but may include three prisms that form a prism pair for each of prisms 43, 44, and 45. In addition, any one or more or all of first prism 43, second prism 44, and third prism 45 may have a concave inclined entrance surface like first prism 41 (see FIG. 2) in the first embodiment. By making prisms 43, 44, and 45 have concave entrance surfaces, the distance between them and fourth prism 46 can be shortened (see fourth embodiment).

[0078] (Modification) The optical measurement device 1C according to the third embodiment may include a collimating lens instead of the parabolic mirror 24. The optical measurement device 1C may include an axicon mirror as the diverging optical elements 43, 44, and 45 and the corrective optical element 46 of the diverging optical system 4C. The axicon mirror has a concave conical mirror surface, and in this embodiment, has a flat surface (vertical surface) perpendicular to the optical axis at the bottom. The axicon mirrors 43 and 46 have a vertical surface at the portion where the light L0 is incident, the axicon mirror 44 has a vertical surface at the portion where the light L0 and L1 are incident, and the axicon mirror 45 has a vertical surface at the portion where the light L0, L1, and L2 are incident.

[0079] The optical measurement device 1C according to the third embodiment may include a lens, instead of the collimator lens 22a, into which all of the light beams L0, L1, L2, and L3 of the far-field pattern FFP are incident on the incident side of the beam splitter 31. This lens, in cooperation with the parabolic mirror 24, reduces the spread angle of the light beams so as to make the light beams L0, L1, L2, and L3 into parallel beams.

[0080] The optical measuring device 1C according to the third embodiment can simultaneously observe the near-field image NFP and the far-field image FFP of the optical element OE as a configuration including the beam splitter 32, the third image pickup element 82, the imaging lens 72, etc., like the optical measuring devices 10, 10A, 10B, and 10C according to the modified examples of the first embodiment (see Figs. 4 to 7). Specifically, for example, the beam splitter 32 is disposed on the light emission side of the collimator lens 23, and the imaging lens 71 and the second image pickup element 81 are disposed on one of the branched emission sides, and the imaging lens 72A and the third image pickup element 82 are disposed on the other emission side (see Fig. 5).

[0081] [Fourth embodiment] In the optical measurement device according to the third embodiment, the diverging optical system widens the distance so that the light in the 0° direction is incident on a different photodetector depending on the distance from the optical axis at the incident position. Therefore, the optical measurement device according to the present invention can be configured to remove the main lobe and low-order light from the diffracted light and other light as noise, and to measure each order.

[0082] (Optical Measuring Device) 11, an optical measurement device 1D according to a fourth embodiment of the present invention includes a collimating lens (collimating optical system) 22, a prism group (diverging optical system) 4D consisting of prisms 47, 48, and 49, a first imaging element 60 in which photodetectors (light receiving elements) 6 are linearly arranged, and preferably further includes a condensing lens (condensing optical system) 5A. The optical measurement device 1D may further include collimating lenses 21 and 23, a beam splitter (light branching element) 31, an imaging lens (imaging optical system) 71, and a second imaging element 81. In detail, the optical measurement device 1D is provided with a collimator lens 21, a beam splitter 31, a collimator lens 22, a first prism 47, a second prism 48, a third prism 49, a condenser lens 5A, and a first image pickup element 60 arranged in order on the side of the optical element OE to be evaluated, i.e., from the light incident side, and further includes a collimator lens 23, an imaging lens 71, and a second image pickup element 81 arranged in order from the beam splitter 31 side in the direction of branching of light by the beam splitter 31. In addition, in this embodiment, the first image pickup element 60 is provided with five photodetectors 6 arranged at equal intervals in the X direction.

[0083] In the optical measurement device 1D according to this embodiment, the optical element OE to be evaluated is an optical deflection element or a diffraction grating similar to that in the first embodiment. Examples of the diffraction grating include MEMS (Micro Electro Mechanical Systems), liquid crystal, a spectroscopic prism, a metasurface, a photonic crystal device, a grating (diffraction grating) surface emitting laser (VCSEL, etc.), an arrayed waveguide grating (AWG), a spatial light modulator (SLM, etc.), a fiber array, and a light guide plate for an augmented reality (AR) head mounted display. The optical measurement device 1D measures the intensities of the 0th order light, ±1st order light, and ±2nd order light for the diffracted light output from the optical deflection element or the diffraction grating centered on one direction such as the 0° direction. In FIG. 11, the light L of the far-field image FFP of the light output from the optical element OE is measured. F The intensity peaks are represented by the shade of the pattern, with the most intense 0th order light being represented in black, the ±1st order lights being represented in dark gray, and the ±2nd order lights being represented in gray.

[0084] The collimator lens 22 and the collimator lens 23 collimate each of the lights split by the beam splitter 31. The collimator lens 23 is provided detachably, as in the third embodiment. On the other hand, the collimator lens 22 does not have to be detachable. In this embodiment, the light incident on the first imaging element 60 (photodetector 6) and the light incident on the second imaging element 81 are collimated separately, so that the light L of the far-field pattern FFP F In particular, since the light incident on the first image sensor 60 is split into beams of different orders by the prism group 4D described below, the beam diameter is set to correspond to the dimensional accuracy and positional accuracy of the prisms 47, 48, and 49 of the prism group 4D.

[0085] The prism group (divergence optical system) 4D converts the light (diffracted light) L of the far-field pattern FFP, which has been converted by the collimator lens 22 into parallel light in the optical axis (Z axis, shown by the dashed line in the drawing) direction (0°), into a parallel light. F The prism group 4D splits the light into light beams according to the orders, and outputs the light beams with the intervals between them widened. Specifically, the intervals between the light beams are set to the arrangement pitch of the photodetectors 6 in the first imaging element 60. For this purpose, the prism group 4D outputs the light beams with the distance at the output position increased as the distance from the optical axis at the input position increases, similar to the prism group 4C (see FIG. 10) of the optical measuring device 1C according to the third embodiment. Furthermore, the prism group 4D causes the light beams on the optical axis (Z axis), i.e., the 0th order light beams, to travel straight along the optical axis as they are. The input and output positions of the prism group 4D are positions on the imaginary input surface 4i and output surface 4e of the prism group 4D, which are perpendicular to the optical axis. Furthermore, it is preferable that the split diffracted light beams of the prism group 4D are parallel to each other, and therefore the output angle is set to 0°, which is the same as the input angle.

[0086] The prism group 4D is composed of a first prism (divergent optical element) 47 that does not diffuse light and outputs it at an output angle larger than the incident angle, and second and third prisms (corrective optical elements) 48, 49 that output the light output from the first prism 47 at an output angle smaller than the incident angle. The prism group 4D includes the first prism 47, the second prism 48, and the third prism 49 arranged in this order from the light incident side. Each of the prisms 47, 48, and 49 can be an axicon lens that is a rotationally symmetric prism, similar to the first prism 41 and the second prism 42 (see FIG. 2) in the first embodiment. Furthermore, when only one dimension (X direction) is to be measured, the prisms 47, 48, and 49 can be a plane-symmetric prism with a plane (ZY plane) including the optical axis (Z axis) as a symmetric plane.

[0087] The first prism (divergent optical element) 47 receives the light, which has been converted into parallel light by the collimator lens 22, at an incident angle of 0° and emits it at a predetermined exit angle θe (>0°). As with the first prism 41 in the first embodiment, the first prism 47 has an entrance surface that is a concave inclined surface and an exit surface that is a plane (vertical surface) perpendicular to the optical axis. If it is an axicon lens (plano-concave axicon lens), the inclined surface is a conical surface, and if it is a plane-symmetrical prism, the inclined surface is a plane inclined in the XZ direction. However, in a predetermined region centered on the optical axis, the first prism 47 has an entrance surface that is a vertical surface, or a through hole along the optical axis is formed, and if it is a plane-symmetrical prism, two prisms are arranged symmetrically with a gap between them. In detail, if the spot distance between the 0th order light and the ±1st order light on the entrance surface 4i of the prism group 4D is Δx1, it is preferable that only the region with a diameter or width of Δx1 (from the optical axis to Δx1 / 2) centered on the optical axis is a vertical surface or a through hole. With this configuration, the first prism 47 advances light (zeroth-order light) with a predetermined beam diameter on the optical axis (Z-axis) in a straight line, and bends diffracted light of first and higher orders to separate it from the zeroth-order light. Furthermore, the larger the inclination angle (apex angle) of the entrance surface of the first prism 47 is, and the higher the refractive index of the material is, the larger the exit angle θe becomes. However, the apex angle of the first prism 47 is set to be less than the critical angle so that the incident light is not totally reflected.

[0088] The second and third prisms (corrective optical elements) 48, 49 emit light at an exit angle smaller than the incident angle θe (>0°), and preferably have the same exit angle as each other, and more preferably have the same exit angle (0°) as the incident angle to the first prism 47. The second and third prisms 48, 49 have a vertical entrance surface and a convex exit surface. If they are an axicon lens (plano-convex axicon lens), the inclined surface is a cone surface, and if they are a plane-symmetric prism, the inclined surface is a plane inclined in the XZ direction. However, as described later, the second and third prisms 48, 49 each have an exit surface that is a vertical surface in a predetermined region centered on the optical axis, or a through hole is formed along the optical axis, and if they are a plane-symmetric prism, the two prisms are arranged plane-symmetrically with a gap between them. It is preferable that the refractive index and apex angle of the material of the second and third prisms 48, 49 are the same as those of the first prism 47, that is, each of them forms a prism pair with the first prism 47. With this configuration, the angle of incidence on the first prism 47 and the angles of emergence from the second and third prisms 48 and 49 are the same (0°).

[0089] The second prism 48 emits only ±1st order light of the first or higher order diffracted light traveling in the θe direction at an emission angle of 0°, and causes other light to travel straight. In detail, the second prism 48 has an area with at least a diameter or width of Δx1 centered on the optical axis as a vertical emission surface or through hole, and an inclined surface in the area where the ±1st order light is emitted, and is designed with an outer diameter or X-direction length such that second or higher order diffracted light does not enter. The third prism 49 emits only ±2nd order light of the second or higher order diffracted light traveling in the θe direction at an emission angle of 0°, and causes other light to travel straight. In detail, in order to allow the 0th order light and ±1st order light traveling in the 0° direction to travel straight, the third prism 49 has a predetermined area centered on the optical axis onto which these lights are incident, which is a vertical exit surface or a through hole, and the area from which the ±2nd order lights exit is an inclined surface, and further is designed with an outer diameter or X-direction length such that third or higher order diffracted light is not incident.

[0090] The longer the interval between the first prism 47 and the second prism 48, the greater the distance between the emission positions of the ±1st order light. Similarly, the longer the interval between the first prism 47 and the third prism 49, the greater the distance between the emission positions of the ±2nd order light. Therefore, the structures (refractive index, apex angle) and the intervals between the prisms 47, 48, 49 are designed so that the ±1st order light and the ±2nd order light are received by the respective predetermined photodetectors 6.

[0091] (Operation of optical measuring device) The operation of the optical measurement device according to the fourth embodiment of the present invention will be described with reference to FIG. Light L of the far-field pattern FFP output from the optical element OE at the center in the 0° direction F The light L is split into two directions by the beam splitter 31. F The light is converted into parallel light by the collimator lens 23 and forms an image on the light receiving surface of the second image sensor 81 by the imaging lens 71.

[0092] The other light L split by the beam splitter 31 Fis collimated by collimator lens 22 and enters prism group 4D at an incident angle of 0°. The zeroth-order light on the optical axis (Z-axis) travels straight through prisms 47, 48, and 49 of prism group 4D, is collected by collecting lens 5a on the Z-axis, and is incident on and received by photodetector 6 on the Z-axis of first imaging element 60. The first and higher order diffracted lights are emitted by first prism 47 at an emission angle θe (>0°), separated from the zeroth order light, and travel away from the Z-axis. Of the first and higher order diffracted lights traveling in the θe direction, only ±1st order lights are incident on second prism 48, return to an emission angle of 0°, and are separated from second and higher order diffracted lights. The ±1st order light then travels straight through the third prism 49 and is transmitted therethrough, and is incident on and received by the first photodetector 6 from the Z-axis side of the first imaging element 60 (excluding the side on the Z-axis) via the opposing lens 5a. The second and higher order diffracted light travels outside the second prism 48, and only the ±2nd order light enters the third prism 49, returning to an emission angle of 0° and being separated from the third and higher order diffracted light. The ±2nd order light then enters and is received by the second photodetector 6 from the Z-axis side of the first imaging element 60 via the opposing lens 5a. As a result, the photodetectors 6 receive +2nd order light, +1st order light, 0th order light, -1st order light, and -2nd order light in order from the top in FIG. 11.

[0093] As described with reference to FIG. 3A in the first embodiment, the light L of the near-field pattern NFP N is converted into parallel light by collimator lens 21, but is converted into diffuse light by collimator lenses 22 and 23 arranged on the exit side thereof, and therefore is not imaged on the light receiving surface of second imaging element 81 by imaging lens 71. Therefore, imaging of the far-field pattern FFP is not impeded in second imaging element 81. The same is true for first imaging element 60. In order to observe the near-field pattern NFP, collimator lens 23 is removed from optical measurement device 1D (see FIG. 3B).

[0094] In the optical measuring device 1D according to this embodiment, when only low-order light of the first order or lower (-1st order light, 0th order light, +1st order light) is measured, the prism group 4D may include one prism pair of the first prism 47 and the second prism 48. Furthermore, when only the 0th order light (main lobe) is measured, the prism group 4D may include only the first prism 47, and may include only one photodetector 6 on the Z axis. Furthermore, the optical measuring device 1D can measure diffracted light of third order or higher by providing the prism group 4D with an additional prism that serves as a corrective optical element and increasing the number of photodetectors 6 in the first imaging element 60.

[0095] (Modification) The optical measuring device 1D of this embodiment may be equipped with a parabolic mirror as the collimating optical system 22, and a beam splitter 31 is disposed between the mirror surface of the parabolic mirror 22 and the focal point so that the optical path of the reflected light from the parabolic mirror 22 does not overlap with the optical path of the output light of the optical element OE.

[0096] The optical measurement device 1D according to this embodiment may include an axicon mirror as the diverging optical element 47 and the corrective optical elements 48, 49 of the diverging optical system 4D. The axicon mirror has a concave conical mirror surface, and in this embodiment, has a flat surface (vertical surface) perpendicular to the optical axis at the bottom. The axicon mirror 47 has a vertical surface at the portion where the zeroth order light is incident. The axicon mirror 48 has a vertical surface at the portion where the zeroth order light is incident, and has an outer diameter such that second order or higher diffracted light is not incident. The axicon mirror 49 has a vertical surface at the portion where the first order or lower order light is incident, and has an outer diameter such that third order or higher order light is not incident.

[0097] The optical measuring device 1D according to this embodiment may be configured to dispose the collimating lens 22 on the light incident side of the beam splitter 31 (between the collimating lens 21) in the same manner as the optical measuring device 1 according to the first embodiment, and may not include the collimating lens 23. Also, the optical measuring device 1D may be configured to include the beam splitter 32, the imaging lens 72, and the third imaging element 82, as in the optical measuring devices 10, 10A, 10B, and 10C (see FIGS. 4 to 7) according to the modifications of the first embodiment, and may simultaneously observe the near-field image NFP and the far-field image FFP of the optical element OE. EXAMPLES

[0098] In order to confirm the effects of the present invention, a simulation was performed using a sample simulating the optical measurement devices according to the first to fourth embodiments of the present invention, and the incidence angle and emergence angle of the beam at each optical element were obtained.

[0099] Example 1 As a sample simulating the optical measuring device according to the first embodiment of the present invention shown in FIG. 2, a plane-symmetric prism (first prism) as a diverging optical element, a plane-symmetric prism (second prism) as a correcting optical element, and a convex lens as a condensing lens are arranged in this order from the light incident side, as shown in FIG. 12. The right side of the figure and the drawings showing the samples of Example 2 and the following examples is the light incident side, and the beam travels to the left. All optical elements such as prisms and convex lenses, including those of Example 2 and the following examples, are made of BK7 (refractive index 1.5). The first prism is two right-angle prisms with a vertex angle of 45° and a side length (length in the optical axis direction) of 20 mm, arranged with a gap of 2 mm (distance from the optical axis 1 mm) and a position of the incident surface (the position of the far-field image is taken as 0) of 8 mm, so that the incident surface is a concave surface and the exit surface is a vertical surface. The second prism is composed of two right-angle prisms with a 45° apex and a side length of 40 mm, arranged with a gap of 40 mm (20 mm from the optical axis) and the position of the entrance surface at 60 mm (32 mm from the first prism) so that the entrance surface is vertical and the exit surface is convex. The convex lens is made by bonding two 150 mm diameter plano-convex lenses together, with the entrance surface f1800 and the exit surface f800, the position of the entrance surface at 300 mm, and the position of the bonded surface at 350 mm.

[0100] The input light was collimated light with a beam diameter of 1 mm, and four angles of incidence were set: 0°, 5°, 10°, and 15°. The simulation was performed using FRED optical software (Photon Engineering, LLC). Figure 12 shows an image of the optical path of the simulated beam. The exit angle from the first prism, the exit angle from the second prism, and the exit angle from the convex lens as the angle of incidence to the photodetector (PD) were calculated. Furthermore, assuming that the photodetector is arranged at a position 1000 mm from the far-field image, the distance from the optical axis at this position (exit position) was calculated. These values ​​are shown in Table 1 for input light with angles of incidence of 5°, 10°, and 15°.

[0101] [Table 1]

[0102] As shown in Table 1 and Figure 12, two plane-symmetric prisms (two sets of prisms) separate light beams with different angles of incidence while preventing the output angle from changing significantly with respect to the angle of incidence, and by combining it with a convex lens, the angle of incidence at the photodetector can be made close to 0°. It is expected that the optical path length to the photodetector can be made even shorter depending on the refractive index and apex angle of each of the two prisms, as well as the light receiving area and allowable range of the angle of incidence of the photodetector.

[0103] Example 2 As a sample simulating the optical measurement device according to the second embodiment of the present invention shown in FIG. 8, a plane-symmetric prism (first prism) as a diverging optical element, and two convex lenses and a plane-symmetric prism (second prism) as correction optical elements were arranged in order from the light incident side, as shown in FIGS. 13A and 13B. The first prism has the same structure as the first prism in Example 1. That is, the first prism is two right-angle prisms with a vertex angle of 45° and a side length (length in the optical axis direction) of 20 mm, arranged with a gap of 2 mm (distance from the optical axis 1 mm) and a position of the incident surface (the position of the far-field image is taken as 0) of 8 mm, so that the incident surface is a concave surface and the exit surface is a vertical surface. Both convex lenses are 100 mm in diameter and f800, and the position of the incident surface is 300 mm for the first lens (the distance from the first prism is 272 mm) and 360 mm for the second lens (the distance from the first convex lens is 30 mm). The second prism is made up of two right-angle prisms with a 45° apex angle and a side length of 50 mm, arranged with a gap of 1150 mm (distance from the optical axis 575 mm) and the entrance surface positioned at 860 mm (distance from the second convex lens 470 mm) so that the entrance surface is vertical and the exit surface is convex.

[0104] The input light was collimated light with a beam diameter of 1 mm, and had four angles of incidence: 0°, 5°, 10°, and 15°. Figure 13A shows an image of the optical path of the beam by simulation. Figure 13B shows an enlarged view of the vicinity of the first prism in Figure 13A. The exit angle from the first prism, the incident angle to the second prism (the exit angle from the second convex lens), and the exit angle from the second prism as the incident angle to the photodetector (PD), as well as the distance from the optical axis at this position (exit position) were calculated, assuming that the photodetector was arranged at a position 1000 mm from the far-field image. The exit position at 100 mm from the far-field image was also calculated. Table 2 shows these values ​​for input light with incident angles of 5°, 10°, and 15°.

[0105] [Table 2]

[0106] As shown in Table 2 and Figures 13A and 13B, by using two plane-symmetric prisms (two sets of prisms) and two convex lenses between them, light with different incident angles other than 0° can be separated from the optical axis while bringing the emission positions closer to each other, and further making the incident angle to the photodetector close to 0°.

[0107] Example 3 As a sample simulating the optical measurement device according to the modified example of the second embodiment of the present invention shown in Fig. 9, a plane-symmetric prism (prism) as a diverging optical element and a plano-convex lens as a correction optical element and light collecting optical system are arranged in order from the light incident side as shown in Fig. 14. The prism has an entrance surface that is a convex surface including a vertical surface at the center and an exit surface that is a vertical surface, a cross-sectional shape of an isosceles trapezoid, an apex angle of 45°, a length in the optical axis (Z axis) direction of 14 mm, a length in the X direction of 30 mm, a length in the X direction of the plane perpendicular to the entrance surface of 2 mm, and a position of the entrance surface (the position of the far field image is set to 0) of 20 mm. The plano-convex lens has a diameter of 30 mm, an entrance surface of f80, an exit surface that is a vertical surface, and a position of the entrance surface of 90 mm (a distance from the prism of 56 mm).

[0108] The input light was collimated light with a beam diameter of 1 mm, and had four angles of incidence: 0°, 5°, 10°, and 15°. An image of the optical path of the beam from a simulation is shown in Figure 14. The exit angle from the prism and the exit angle from the plano-convex lens as the angle of incidence to the photodetector (PD), as well as the distance from the optical axis at this position (exit position) were calculated, assuming that the photodetector is arranged at a position 210 mm from the far-field image. These values ​​for input light with incidence angles of 5°, 10°, and 15° are shown in Table 3.

[0109] [Table 3]

[0110] As shown in Table 3 and Figure 14, one plane-symmetric prism and one convex lens can move light with different angles of incidence other than 0° away from the optical axis while bringing the emission positions closer to each other, and furthermore, make the angle of incidence to the photodetector close to 0°. Note that the light is diffused at a position 210 mm from the far-field pattern, but it can be focused by adding a focusing lens facing each photodetector.

[0111] Here, the sample shown in Fig. 14 has an incidence angle range of 3° to 23° inclusive for the measurement target, as shown in Fig. 15A. In order to increase the upper limit of the incidence angle, the dimensions of the prism can be increased. For example, as shown in Fig. 15B, if the optical axis length of the prism is increased to 17 mm, it becomes possible to measure incidence angles up to 25°.

[0112] Example 4 As a sample simulating the prism group (divergence optical system) of the optical measurement device according to the third embodiment of the present invention shown in Fig. 10, a rotationally symmetric prism (first prism) was arranged as a divergence optical element and a rotationally symmetric prism (second prism) was arranged as a correction optical element, in order from the light incident side, as shown in Fig. 16. The first prism has an entrance surface that is a convex surface including a vertical surface at the center, an exit surface that is a vertical surface, a cross-sectional shape of an isosceles trapezoid, an apex angle of 45°, an optical axis direction length of 2 mm, a diameter of 5 mm, a diameter of the vertical surface of the entrance surface of 1 mm, and a position of the entrance surface (the position of the far field image is set to 0) of 5 mm. The second prism has an entrance surface that is a convex surface including a vertical surface at the center, an exit surface that is a convex surface including a vertical surface at the center, a cross-sectional shape of an isosceles trapezoid, an apex angle of 45°, an optical axis direction length of 3 mm, a diameter of 28 mm, a diameter of the vertical surface of the exit surface of 22 mm, and a position of the entrance surface of 33 mm (the distance from the first prism is 26 mm).

[0113] The input light was collimated light with a beam diameter of 1 mm, with an incident angle of 0° and three incident positions of -1 mm, 0, and +1 mm. An image of the optical path of the beam from a simulation is shown in Figure 16. The exit angle from the first prism and the exit angle from the second prism as the incident angle to the photodetector (PD) were calculated. Furthermore, assuming that the photodetector is arranged at a position 200 mm from the far-field image, the distance from the optical axis at this position (exit position) was calculated. These values ​​are shown in Table 4 for the input light with incident positions of -1 mm and +1 mm.

[0114] [Table 4]

[0115] As shown in Table 4 and Figure 16, the two rotationally symmetric prisms that make up the prism pair separate the parallel light with an incident position of ±1 mm from the exit position by more than ±12 mm at 200 mm from the far-field pattern, and the exit angle from the second prism, i.e., the incident angle to the photodetector, is 0.08°, i.e., nearly 0°, and remains parallel light. It can be said that the exit position can be adjusted to the arrangement pitch of the photodetector by adjusting the distance between the two prisms.

[0116] Although various embodiments for implementing the optical measurement device according to the present invention have been described above, the present invention is not limited to these embodiments, and various modifications are possible within the scope of the claims. [Explanation of symbols]

[0117] 1,1A,1B,1C,1D Optical measuring device 10, 10A, 10B, 10C Optical measuring device 21 Collimating lens 22,22B Collimating lens (collimating optical system) 22a Collimating lens (collimating optical system) 23 Collimating Lens 31,32 Beam splitter (optical branching element) 4, 4A, 4C, 4D Prism group (diverging optical system) 4B Diverging optical system 41, 41A First prism (diverging optical element) 42, 42A Second prism (corrective optical element) 43 First prism (divergent optical element) 43B Prism (diverging optical element) 44 Second prism (divergent optical element) 45 Third prism (divergent optical element) 46 Fourth prism (corrective optical element) 47 First prism (divergent optical element) 48 Second prism (corrective optical element) 49 Third prism (corrective optical element) 5,5A Condenser lens (condenser optical system) 5B Condenser lens (corrective optical element, converging optical system) 60 First image sensor 6 Photodetector (light receiving element) 71, 71A Imaging lens (imaging optical system) 72, 72A Imaging lens (imaging optical system) 81 Second image sensor 82 3rd image sensor

Claims

1. a collimating optical system that collimates light to be measured; a diverging optical system that outputs the light emitted from the collimating optical system at a wider distance from an optical axis; and a first imaging element having two or more light receiving elements that receive the light emitted from the diverging optical system and are arranged in one or more one- or two-dimensional arrays; The diverging optical system of the optical measurement device includes a diverging optical element that emits light without diffusing it at an exit angle larger than its incident angle, and a corrective optical element that emits the light emitted from the diverging optical element at an exit angle smaller than its incident angle.

2. 2. The optical metrology device of claim 1, wherein the diverging optical element is a rotationally symmetric prism.

3. The first imaging element includes one or more light receiving elements arranged in a one-dimensional manner, 2. The optical measurement device according to claim 1, wherein the diverging optical element is a plane-symmetric prism with a plane including the optical axis as a plane of symmetry.

4. 4. The optical measurement device according to claim 1, further comprising a focusing optical system that focuses the light emitted from the diverging optical system onto a light receiving element of the first image sensor.

5. 4. The optical measurement device according to claim 1, wherein light is incident on different light receiving elements in accordance with a distance from an optical axis of an incident position on the diverging optical system or an incident angle.

6. 4. The optical measurement device according to claim 1, wherein light within a predetermined range of a distance from an optical axis of an incident position to the diverging optical system or an incident angle is incident on the same light receiving element.

7. The imaging device further includes a light branching element that branches the light into two or more light beams, a second imaging element having a plurality of light receiving elements arranged two-dimensionally, and an imaging optical system that forms an image of the light beam on the light receiving surface of the second imaging element, 4. The optical measurement device according to claim 1, wherein the diverging optical system receives one of the two beams branched by the optical branching element, and the second imaging element receives the other beam via the imaging optical system.

8. 8. The optical measurement device according to claim 7, wherein the collimating optical system is made up of two or more optical elements, and some of the light beams from the two or more optical elements are detachable.

9. Further comprising: a third image sensor including a plurality of light receiving elements arranged two-dimensionally; and an imaging optical system that forms an image of light on the light receiving surface of the third image sensor; The optical branching element branches the light into three or more beams, The optical measurement device according to claim 7 , wherein the third imaging element receives light different from the two light beams branched by the optical branching element via the imaging optical system.

Images