spectroscopic camera

Abstract

Provided is a spectroscopic camera capable of capturing a spectroscopic image in which the influence of ghosting is suppressed. A spectroscopic camera (1) includes a plurality of flat plate elements including a standard; a first lens group disposed at a position closer to an object side than the standard; a second lens group disposed at a position closer to an image side than the standard; and a capturing element that receives light that has passed through the second lens group from the standard, wherein parallel light that has been collimated by the first lens group is incident on the plurality of flat plate elements, the second lens group constitutes an imaging optical system that causes light that has passed through the plurality of flat plate elements to be imaged on the capturing element, and the Fresnel reflection interface, on which no antireflection film is disposed, is two-sided or less in the plurality of flat plate elements on which the parallel light is incident.

Description

Technical Field

[0001] This invention relates to a spectrophotometer. Background Technology

[0002] In a video camera, there is an optical system that consists of multiple lenses arranged from the objective lens to the imaging element, and sometimes a flat panel element is embedded in such an optical system.

[0003] In particular, in beam splitters equipped with wavelength-variable etalons in the optical system of a camera, the etalon is sometimes housed in an airtight enclosure to suppress mechanical impacts and water droplet ingress. In this case, the enclosure requires an incident portion for incident light to pass through toward the etalon and an exit portion for outgoing light from the etalon, and these incident and exit portions are made of flat plates such as glass (see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent document 1: Japanese Patent Application Publication No. 2014-142387.

[0007] However, in the configuration of embedding multiple planar elements in the optical system of a beam splitter and incident parallel light onto these planar elements, there is a technical problem that causes multiple reflections of light due to reflections at the interfaces of the planar elements, resulting in ghosting in the beam splitter image. Summary of the Invention

[0008] The first aspect of this disclosure relates to a beam splitter camera comprising: a plurality of flat panel elements, the plurality of flat panel elements including a etalon; a first lens group disposed at a position closer to the object side than the etalon; a second lens group disposed at a position closer to the image side than the etalon; and an imaging element that receives light from the etalon that has passed through the second lens group, and parallel light collimated by the first lens group is incident on the plurality of flat panel elements, the second lens group constituting an imaging optical system that images the light transmitted through the plurality of flat panel elements onto the imaging element, wherein among the plurality of flat panel elements on which the parallel light is incident, there are two or fewer Fresnel reflection interfaces without anti-reflective coatings. Attached Figure Description

[0009] Figure 1 This is a schematic diagram showing the general configuration of the beam splitter camera according to the first embodiment.

[0010] Figure 2 This is a schematic diagram showing a portion of the optical system configuration of this embodiment.

[0011] Figure 3This is a cross-sectional view showing the schematic configuration of the etalon, filter package, and bandpass filter in this embodiment.

[0012] Figure 4 This is a schematic diagram illustrating the mechanism by which ghosting occurs when parallel light is incident on multiple flat panel elements.

[0013] Figure 5 This is an example of a simulation result that visualizes the positions of the real image and the ghost image when multiple flat panel elements are not fitted with anti-reflective coatings.

[0014] Figure 6 This is a diagram showing the placement of the antireflective film in this embodiment.

[0015] Figure 7 This is a diagram showing an example of the simulation results indicating the position of the ghost image obtained by optically simulating the beam splitter camera of this embodiment.

[0016] Figure 8 This is a graph showing the ghosting reduction rate when an anti-reflective coating is applied relative to the Fresnel reflective interface of each flat panel element configured in the beam splitter.

[0017] Figure 9 This is a diagram showing the placement of the antireflective film in the second embodiment.

[0018] Figure 10 This is a diagram showing the placement of the antireflective film in the third embodiment.

[0019] Figure 11 This is a diagram illustrating an example of a simulation result that visualizes the position of the real image and the position of the ghost image of an object, obtained by optical simulation of the beam splitter camera of the third embodiment.

[0020] Figure 12 This is a diagram showing the placement of the antireflective film in the fourth embodiment.

[0021] Explanation of reference numerals in the attached figures

[0022] 1. Beam splitter camera; 12. Optical system assembly; 13. Imaging element; 20. Interchangeable lens; 31. First lens group; 32. Second lens group; 40. Erebecca; 41. First substrate; 42. Second substrate; 43. First reflective film; 44. Second reflective film; 50. Filter package; 51. Protective glass; 52. Cover glass; 60. Bandpass filter; 70. Anti-reflective film; 311. Collimator optical system; L. Optical axis of the imaging element. Detailed Implementation

[0023] First Implementation Method

[0024] The first embodiment of the beam splitter of this disclosure will now be described.

[0025] Overall Components of a Spectrometer

[0026] Figure 1 This is a schematic diagram showing the general configuration of the beam splitter camera according to the first embodiment.

[0027] The beam splitter 1 of this embodiment includes a camera body 10 and an interchangeable lens 20 that can be freely attached to and detached from the camera body 10.

[0028] like Figure 1 As shown, the camera body 10 includes a camera housing 11, an optical system component 12, an image sensor 13, and a circuit board 14. The optical system component 12, the image sensor 13, and the circuit board 14 are housed within the camera housing 11.

[0029] The camera housing 11 has internal space for housing the optical system assembly 12, the imaging element 13, and the circuit board 14. In addition, the camera housing 11 has a fixing mechanism for fixing each lens, imaging element 13, and circuit board 14 included in the optical system assembly 12.

[0030] Furthermore, the camera housing 11 has a lens holder 111 that allows for easy attachment and detachment of the interchangeable lens 20. In the beam splitter 1 of this embodiment, any interchangeable lens 20 can be mounted on the lens holder 111. Figure 1 Although the illustration is omitted, multiple lenses are embedded in the interchangeable lens 20, and these lenses are different in each interchangeable lens 20. Therefore, different shooting conditions, such as zoom magnification, can be achieved using each interchangeable lens 20.

[0031] Figure 2 This is a schematic diagram showing a portion of the optical system component 12.

[0032] like Figure 2 As shown, the optical system assembly 12 includes a first lens group 31 and a second lens group 32. In the following description, it is assumed that the optical axis L of each lens constituting the optical system assembly 12 is aligned with the optical axis L of the imaging element 13, and the direction along the optical axis L is designated as the Z direction (the side facing the imaging element 13 is designated as +Z). In addition, a direction orthogonal to the Z direction is designated as the X direction, and a direction orthogonal to both the X and Z directions is designated as the Y direction.

[0033] First shot group 31 (in) Figure 2 (A portion of the +Z side is shown) guides light incident from the interchangeable lens 20 to the etalon 40 and the second lens group 32. (As shown in the image) Figure 2As shown, the first lens group 31 includes a collimator optical system 311 that makes the incident light parallel light. The light that is paralleled by the collimator optical system 311 passes through the etalon 40 and is guided from the second lens group 32 to the imaging element 13.

[0034] The etalon 40 selects a predetermined wavelength from the incident light and allows it to pass through. Thus, the imaging element 13 receives the light of the predetermined wavelength that has passed through the etalon 40 and captures a spectral image.

[0035] Furthermore, a plurality of flat panel elements are disposed between the first lens group 31 and the second lens group 32. These flat panel elements include a glass substrate constituting the standard etalon 40 (the first substrate 41 and the second substrate 42 described later), and a filter package 50 disposed on the standard etalon 40 (see reference 50). Figure 3 The protective glass 51 and cover glass 52, and the bandpass filter 60 that allows only light of a predetermined wavelength to pass through.

[0036] It should be noted that the descriptions of the etalon 40, the filter package 50, and the bandpass filter 60 will be provided later.

[0037] The second lens group 32 is an imaging optical system that enables light transmitted through the standard 40 to be imaged on the imaging element 13, for example, by forming a telecentric optical system using multiple lenses.

[0038] The imaging element 13 is an image sensor with multiple pixels that outputs image information of a spectral image by receiving light guided by the optical system component 12.

[0039] The circuit board 14 is provided with circuitry for controlling the driving of the imaging element 13 and the etalon 40. Although not shown in the figure, the circuit board 14 includes recording circuitry for recording various information, arithmetic circuitry for executing various programs, and driving circuitry for controlling the driving of the imaging element 13 and the etalon 40.

[0040] In addition, such as Figure 1 As shown, multiple circuit boards 14 can also be provided. Figure 1 The example shown is a circuit board 14 having a filter package 50 for housing a standard etalon 40 fixed thereon and a circuit board 14 having an imaging element 13 fixed thereon. In the configuration where the filter package 50 and the imaging element 13 are fixed to the circuit board 14, by fixing the circuit board 14 to a predetermined fixed position on the camera housing 11, the filter package 50 and the imaging element 13 can be positioned at a desired position (fixing mechanism) on the optical system configuration section 12.

[0041] Composition of standard etalon and filter package

[0042] Next, the etalon 40, the filter package 50, and the bandpass filter 60 will be described.

[0043] Figure 3 This is a cross-sectional view showing the schematic configuration of the standard 40, filter package 50, and bandpass filter 60 in this embodiment.

[0044] In this embodiment, by housing the standard 40 in the filter package 50 and attaching the bandpass filter 60 to the filter package 50, the standard 40, the filter package 50, and the bandpass filter 60 are integrally formed.

[0045] The standard etalon 40 is composed of a first substrate 41, a second substrate 42, a first reflective film 43, a second reflective film 44, and an actuator 45.

[0046] The first substrate 41 and the second substrate 42 are substrates that are transparent to each wavelength of the spectral image captured by the beam splitter 1. For example, when capturing a spectral image of a predetermined wavelength in the visible light region, they are made of glass substrates. It should be noted that when capturing a spectral image in the near-infrared region by the beam splitter 1, the first substrate 41 and the second substrate 42 may also be made of substrates such as silicon that are transparent to near-infrared light. The first substrate 41 and the second substrate 42 are integrally formed by bonding them together using a bonding layer.

[0047] In this embodiment, a standard fixture 40 is formed by joining a first substrate 41 and a second substrate 42. In the standard fixture 40, the direction from the second substrate 42 toward the first substrate 41 is designated as Z. E Direction (+Z) E ).

[0048] On the surface of the first substrate 41 opposite to the second substrate 42, a first reflective film 43 and a first electrode 451 constituting the actuator 45 are provided.

[0049] On the surface of the second substrate 42 opposite to the first substrate 41, a second reflective film 44 and a second electrode 452 constituting the actuator 45 are provided.

[0050] The surface of the first substrate 41 facing the second substrate 42 is formed with a recess, for example, by etching. Thus, when the first substrate 41 and the second substrate 42 are joined, the first reflective film 43 and the second reflective film 44 are facing each other through a predetermined first gap G1, and the first electrode 451 and the second electrode 452 are facing each other through a predetermined second gap G2.

[0051] An annular recess is formed on the side of the second substrate 42 opposite to the first substrate 41. The inner side (central part of the substrate) of the annular recess in the second substrate 42 constitutes a movable part 421, and the annular recess constitutes a diaphragm part 422 that holds the movable part 421.

[0052] In the second substrate 42, the second reflective film 44 is disposed on the surface of the movable portion 421 opposite to the first substrate 41. The second electrode 452 may be disposed on the movable portion 421, on the diaphragm portion 422, or in the region extending from the movable portion 421 to the diaphragm portion 422.

[0053] The actuator 45 changes the distance G1 of the first gap between the first reflective film 43 and the second reflective film 44 by applying a voltage. In this embodiment, the actuator 45 is an electrostatic actuator, consisting of a first electrode 451 disposed on the first substrate 41 and a second electrode 452 disposed on the second substrate 42 and opposite to the first electrode 451. By applying a voltage between the first electrode 451 and the second electrode 452, the diaphragm portion 422 is bent by electrostatic attraction, and the movable portion 421 is displaced towards the first substrate 41. As a result, the size of the first gap G1 between the first reflective film 43 and the second reflective film 44 changes, and the wavelength of the light transmitted through the standard 40 changes. It should be noted that since the thickness of the movable portion 421 is greater than the thickness of the diaphragm portion 422, the bending of the movable portion 421, that is, the bending of the second reflective film 44, can be suppressed.

[0054] The filter package 50 is a box-shaped housing that maintains a reduced pressure environment inside, and houses the etalon 40 inside.

[0055] For example, such as Figure 3 As shown, the filter package 50 is configured to have a base 53 formed in the shape of a container and a cover glass 52. By joining the base 53 and the cover glass 52, a storage space is formed inside.

[0056] The base 53 is made of ceramic or the like and has a base portion 531 and a side wall portion 532. When viewed from the Z direction, the base portion 531 is configured as a flat plate with a rectangular shape, for example, and the cylindrical side wall portion 532 rises from the outer periphery of the base portion 531 toward the cover glass 52.

[0057] Additionally, an opening 531A extending along the Z direction is provided in the base portion 531. When the standard 40 is housed in the filter package 50, the opening 531A overlaps with the first reflective film 43 and the second reflective film 44 when viewed from above in the Z direction.

[0058] Additionally, a protective glass 51 covering the opening 531A is joined to the side of the base portion 531 opposite to the cover glass 52.

[0059] Furthermore, on the inner surface of the base portion 531 opposite to the cover glass 52, a wiring portion 541 is provided, which is respectively connected to the first electrode 451 and the second electrode 452 of the standard 40. This wiring portion 541 is connected to an external terminal portion 543 on the outer surface of the base portion 531 via a through electrode 542. When the filter package 50 is embedded in the circuit board 14, the external terminal portion 543 is connected to the drive circuit provided on the circuit board 14.

[0060] The sidewall portion 532 is formed as a frame that rises from the edge of the base portion 531, and the end face on the side opposite to the base portion 531 is a flat surface orthogonal to the Z direction, and the cover glass 52 is joined to this end face. The cover glass 52 is, for example, a transparent component with a rectangular shape when viewed from above, and is made of glass or the like.

[0061] In the filter package 50, the standard etalon 40 is fixed to the side wall portion 532 of the base 53. At this time, as... Figure 3 As shown, one end of the first substrate 41 of the standard fixture 40 is fixed to the sidewall portion 532 by a flexible connecting member 533, forming a cantilever structure. That is, since the other end of the standard fixture 40, which is not fixed to the filter package 50, becomes a free end, the Z-axis of the standard fixture 40 from the second substrate 42 towards the first substrate 41... E The direction (along the optical axis of the standard 40) is slightly tilted relative to the optical axis L (Z direction) of the imaging element 13. Therefore, the standard 40 constitutes the tilting element of this disclosure. The tilt angle is in the range of 0.5 degrees to 5.0 degrees, more preferably in the range of 0.5 degrees to 1.0 degrees.

[0062] With this fixing method, it is not easy for vibrations to propagate from the filter package 50 to the etalon 40.

[0063] The bandpass filter 60 allows light within the spectral band of the spectral pattern that has passed through the etalon 40 to pass through, while blocking other light.

[0064] In other words, the wavelength λ of the light transmitted through the etalon 40 is represented by 2dcosθ=nλ using the size d of the first gap G1 between the first reflective film 43 and the second reflective film 44, the incident angle θ toward the etalon 40, and the order n. Here, the order n takes a positive integer value, and light of wavelengths corresponding to multiple orders passes through the etalon 40. The bandpass filter 60 allows wavelengths of the desired band (e.g., the visible light region) among these wavelengths corresponding to multiple orders to pass through, while blocking light of other bands.

[0065] The bandpass filter 60 can be positioned either further forward (on the side opposite to the imaging element 13) than the etalon 40, or further backward (on the side of the imaging element 13). In this embodiment, the bandpass filter 60 is coupled to a cover glass 52, which is positioned closer to the imaging element 13 than the etalon 40.

[0066] Anti-reflective coating and ghosting suppression effect on flat panel components

[0067] The ghosting produced by the spectrophotometer 1 is explained.

[0068] Figure 4 This is a schematic diagram illustrating the mechanism by which ghosting occurs when parallel light is incident on multiple flat panel elements. Figure 5 This is an example of a simulation result showing the location of the real and ghost images of an object when no anti-reflective coating is applied to multiple flat panel elements. Figure 5 The simulation results show the position of the real image of the object obtained by optical simulation of the designed optical system and the position of the ghost image caused by multiple reflections in the optical system.

[0069] The "ghosting" effect produced in the spectral image of the beam splitter 1 is generally caused by multiple reflections of light between multiple plate elements. In particular, when a portion of the plate elements (etalon 40) is tilted relative to the optical axis L of the imaging element 13, as in this embodiment, ghosting occurs at a position different from the position of the real image of the object. For example, in Figure 4 In the diagram, the dashed line P1 represents light incident on the imaging element 13 without multiple reflections between the flat elements, at point A1. Conversely, the solid line P2 represents light reflected by the second reflective film 44 or the first reflective film 43 of the standard etalon 40, returning to the protective glass 51 and being reflected again by the protective glass 51; in this case, it is incident on point A2, which is offset from point A1 on the imaging element 13. Furthermore, the solid line P3 represents light transmitted through the standard etalon 40, reflected by the cover glass 52, and then reflected again by the second reflective film 44 or the first reflective film 43 of the standard etalon 40; in this case, it is incident on point A3, which is offset from point A1 on the imaging element 13.

[0070] Thus, when light, after being reflected multiple times between the tilted plate element (tilted element) and other plate elements, is incident on the imaging element 13, the light is incident at a position deviating from its original incident position. Therefore, as... Figure 5 As shown, in the spectrophotometer, a ghost image G is projected near the image of the object (real image T).

[0071] Generally, when the ghosting intensity is below 1%, it is difficult for the human eye to visually confirm and has little impact on the measurement results. Therefore, it is preferable to form an anti-reflective film on the flat panel element to eliminate ghosting G with an intensity exceeding 1%. However, without an anti-reflective film on the flat panel element, ghosting G with an intensity exceeding 1% may occur.

[0072] In order to suppress ghosting in the beam splitter 1, it is ideal to provide anti-reflective coatings on all flat panel elements configured in the beam splitter 1.

[0073] However, if an anti-reflective film is applied to all planar elements, the manufacturing cost of the anti-reflective film (e.g., the cost of the film material used to form the anti-reflective film, the time involved in forming the anti-reflective film, etc.) increases accordingly. Furthermore, even if an anti-reflective film is not applied to all planar elements, as long as ghosting occurs to a degree that is not perceptible to the human eye, it will not affect the measurement. Therefore, in the spectrophotometer 1 of this disclosure, in order to minimize manufacturing costs as much as possible and suppress ghosting to a level that does not affect measurement accuracy, an anti-reflective film is applied to the planar elements as described below.

[0074] That is, in this embodiment, the Fresnel interface without anti-reflective film is located on two or fewer sides of the Fresnel interface of the five planar elements of the first substrate 41, the second substrate 42, the protective glass 51, the cover glass 52, and the bandpass filter 60.

[0075] Here, a first reflective film 43 and a first electrode 451 are provided on the surface of the first substrate 41 of the standard substrate 40 facing the second substrate 42, and a second reflective film 44 and a second electrode 452 are provided on the surface of the second substrate 42 facing the first substrate 41. Therefore, these surfaces of the first substrate 41 facing the second substrate 42 and the second substrate 42 facing the first substrate 41 are excluded from the formation of the anti-reflective film. That is, the anti-reflective film is provided on six or seven of the eight surfaces: the surface of the first substrate 41 facing the cover glass 52, the surface of the second substrate 42 facing the protective glass 51, both surfaces (±Z surfaces) of the protective glass 51, both surfaces (±Z surfaces) of the cover glass 52, and both surfaces (±Z surfaces) of the bandpass filter 60.

[0076] Figure 6 This is a diagram showing the placement of the antireflective film 70 in this embodiment. Figure 7 This is a diagram showing an example of a simulation result obtained by performing an optical simulation on the beam splitter 1 of this embodiment, which visualizes the position of the ghost image.

[0077] In this embodiment, as described above, the antireflective film 70 is provided on two or fewer sides of the Fresnel reflective interface of the plurality of flat plate elements where the antireflective film 70 is not provided. Figure 6In one example shown, antireflective films 70 are formed on both sides of the protective glass 51, both sides of the cover glass 52, and both sides of the bandpass filter 60. Therefore, the Fresnel reflective interface without the antireflective film 70 only becomes the surface of the first substrate 41 opposite to the cover glass 52 and the surface of the second substrate 42 opposite to the protective glass 51.

[0078] These antireflective films 70 can be commonly used antireflective films. That is, each antireflective film 70 is formed by stacking multiple optical layers with different refractive indices, and the film is formed such that its Fresnel reflectance is 0.5% or less relative to the wavelength range of the spectral image captured by the beam splitter 1. For example, in this embodiment, spectral images of each wavelength in the visible light region are captured by the beam splitter 1. In this case, an antireflective film 70 with a reflectance characteristic of 0.5% or less relative to the visible light region of 400 nm to 700 nm is formed.

[0079] Compare Figure 7 and Figure 5 It can be seen that when using the spectrophotometer 1 of this embodiment, and... Figure 5 Compared to an optical system without an anti-reflective coating, Ghost G's intensity is sufficiently low.

[0080] It should be noted that in this embodiment, the Fresnel reflective interface without the anti-reflective film 70 in the plurality of flat plate elements is two or fewer. The flat plate elements for which the anti-reflective film 70 is provided are not limited to... Figure 6 The example shown.

[0081] For example, it is also possible to omitrate the anti-reflective film 70 on both sides of the cover glass 52, while providing anti-reflective films 70 on both sides of other flat elements, namely the protective glass 51, the surface of the first substrate 41 opposite the cover glass 52, the surface of the second substrate 42 opposite the protective glass 51, and both sides of the bandpass filter 60. Although an example of the beam splitting image in this case is omitted, it is possible to obtain a beam splitting image similar to the one shown in the example. Figure 6 The same spectroscopic image.

[0082] The effect of this implementation method

[0083] The beam splitter 1 of this embodiment includes: multiple planar elements (protective glass 51, cover glass 52, bandpass filter 60, and etalon 40) including an etalon 40; a first lens group 31 disposed on the object side of the etalon 40; a second lens group 32 disposed on the image side of the etalon 40; and an imaging element 13 that receives light passing through the second lens group 32 from the etalon 40. Parallel light collimated by the first lens group 31 is incident on the multiple planar elements, and the second lens group 32 constitutes an imaging optical system that images the light transmitted through the multiple planar elements onto the imaging element 13. Furthermore, the Fresnel reflective interface in the multiple planar elements where the parallel light is incident is configured to have two or fewer surfaces without an anti-reflective coating 70.

[0084] In this configuration, since the Fresnel reflective interface without the anti-reflective film 70 is on two or fewer sides, multiple reflections of light between the flat panel elements can be suppressed. This suppresses ghosting. Furthermore, compared to cases where anti-reflective films are applied to all flat panel elements, manufacturing costs can be reduced.

[0085] In the beam splitter 1 of this embodiment, the antireflective film 70 is composed of multiple thin films with different refractive indices stacked together, and has a Fresnel reflectance of 0.5% or less relative to the wavelength range of the visible light region.

[0086] Therefore, it is possible to capture spectroscopic images with minimal ghosting effects using a spectroscopic camera.

[0087] Second Implementation Method

[0088] Next, the second embodiment of this disclosure will be described.

[0089] In the following description, the same reference numerals will be used to refer to the components that have already been described, and their descriptions will be omitted or simplified.

[0090] In the first embodiment described above, by configuring the Fresnel reflection interface in the plurality of flat elements of the beam splitter 1, in which the anti-reflective film 70 is not provided, to be on two or less sides, the generation of ghosting is suppressed.

[0091] In contrast, the second embodiment differs from the first embodiment in that an antireflective film 70 is formed on a flat plate element located on the image side closer than the standard etalon 40.

[0092] It should be noted that the beam splitter 1 in this embodiment has the same configuration as that in the first embodiment described above, except that the flat panel element with the anti-reflective film 70 is different. Therefore, the beam splitter 1 in the second embodiment has the same... Figures 1 to 3 The first embodiment shown has the same configuration.

[0093] Figure 8This is a graph showing the ghosting reduction rate when an antireflective coating 70 is applied relative to the Fresnel reflective interface of each flat panel element disposed on the beam splitter 1. Figure 8 This demonstrates the extent to which ghosting can be reduced compared to when all flat panel elements are not fitted with the anti-reflective coating 70.

[0094] Here, in Figure 8 In this context, the surface described as "object side" refers to the orientation of the object captured by the spectrophotometer 1, that is... Figure 1 The Z-side surface, referred to as the "image side," refers to the direction in which the image is formed on the imaging element 13, that is... Figure 1 The +Z side of the surface. For example, "protective glass (object side)" refers to the side of the protective glass 51 opposite to the standard etalon 40 (-Z side), and "protective glass (image side)" refers to the +Z side of the protective glass 51 opposite to the standard etalon 40. Additionally, "standard etalon (object side)" refers to the -Z side of the second substrate 42. E The side surface, that is, the surface opposite to the protective glass 51. "Standard etalon (image side)" refers to the +Z side of the first substrate 41. E The side surface, that is, the surface opposite to the cover glass 52.

[0095] In the beam splitter 1, if a Fresnel reflective interface of a planar element exists at a position closer to the image side than the etalon 40, light reflected by these Fresnel reflective interfaces will enter the etalon 40 from the image side. This incident light is reflected towards the image side by the first reflective film 43 of the etalon 40, resulting in a high probability of ghosting. On the other hand, light that enters the etalon 40 from the object side and is reflected towards the object side by the second reflective film 44 of the etalon 40 will not enter the imaging element 13, thus reducing the ghosting contribution rate of the planar element on the object side.

[0096] Therefore, by providing the antireflective film 70 on the plate element disposed in each plate element at a position closer to the image side than the standard etalon 40, the contribution rate to reducing ghosting is higher compared to the case where the antireflective film 70 is provided on the plate element disposed on the object side.

[0097] Figure 9 This is a diagram showing the placement of the antireflective film 70 in this embodiment.

[0098] In this embodiment, anti-reflective films 70 are provided on both sides of the cover glass 52 and both sides of the bandpass filter 60. The cover glass 52 is a flat plate element that contributes significantly to reducing ghosting, that is, a flat plate element positioned closer to the image side than the etalon 40.

[0099] The effect of this implementation method

[0100] The beam splitter 1 of this embodiment includes: multiple planar elements (protective glass 51, cover glass 52, bandpass filter 60, and etalon 40) including an etalon 40; a first lens group 31 disposed on the object side of the etalon 40; a second lens group 32 disposed on the image side of the etalon 40; and an imaging element 13 that receives light passing through the second lens group 32 from the etalon 40. Parallel light collimated by the first lens group 31 is incident on the multiple planar elements, and the second lens group 32 constitutes an imaging optical system that images the light passing through the multiple planar elements onto the imaging element 13. Furthermore, an anti-reflective coating 70 is provided on the planar elements (cover glass 52 and bandpass filter 60) disposed on the image side of the etalon 40.

[0101] Therefore, multiple reflections of light on the image-side plate element of the etalon, which contributes significantly to the formation of ghosting, can be suppressed. Thus, similar to the first method, ghosting caused by multiple reflections of light at the Fresnel reflection interfaces of each plate element can be suppressed, and manufacturing costs can be reduced compared to the case where anti-reflective films are provided on all plate elements.

[0102] Therefore, multiple reflections of light on the image-side plate elements of the etalon 40, which contribute significantly to the formation of ghosting, can be suppressed. Thus, similar to the first embodiment, ghosting caused by multiple reflections of light at the Fresnel reflection interfaces of each plate element can be suppressed, and manufacturing costs can be reduced compared to the case where anti-reflective films are provided on all plate elements.

[0103] Third Implementation Method

[0104] Next, the third embodiment of this disclosure will be described.

[0105] In the first embodiment described above, ghosting is suppressed by configuring the Fresnel reflection interface in the plurality of flat elements provided in the beam splitter 1 such that the anti-reflective film 70 is not provided on two or fewer sides. In the second embodiment, ghosting is suppressed by providing the anti-reflective film 70 on the flat element on the image side of the etalon 40.

[0106] In contrast, in the third embodiment, an anti-reflective film is provided on the plate element that is tilted relative to the optical axis L among the plurality of plate elements.

[0107] Figure 10 This is a diagram showing the configuration position of the antireflective film 70 in the third embodiment. Figure 11 This is a diagram showing an example of a simulation result obtained by performing an optical simulation on the beam splitter 1 of the third embodiment, which visualizes the position of the real image of the object and the position of the ghost image.

[0108] In this embodiment, such as Figure 10 As shown, an anti-reflective film 70 is provided on each of the image-side and object-side surfaces of a standard 40 that is tilted at an angle θ relative to the optical axis L of the imaging element 13. That is, an anti-reflective film 70 is provided on the +Z plane of the first substrate 41 opposite the cover glass 52. E The second substrate 42 opposite to the protective glass 51 -Z E Anti-reflective film 70 is applied to each surface.

[0109] In this case, multiple reflections between the plate elements (e.g., protective glass 51, cover glass 52) disposed before and after the standard 40 and the standard 40 can be suppressed. That is, multiple reflections between the first substrate 41 and the second substrate 42 of the standard 40, which are tilted relative to the optical axis L, and the plate elements can be suppressed. Thus, by Figure 11 The simulation results show that it can suppress the formation of ghost images G near the real image T.

[0110] It should be noted that, in this configuration, since the Fresnel reflective interface without the anti-reflective film 70 is not configured with two or fewer sides as in the first embodiment, a ghost image G with a ghosting intensity of 1% or more is actually formed at the location where the real image T is formed. However, since the ghost image G overlaps with the real image T, its influence on measurement becomes extremely low.

[0111] The effect of this implementation method

[0112] The beam splitter 1 of this embodiment includes: multiple planar elements (protective glass 51, cover glass 52, bandpass filter 60, and etalon 40) including an etalon 40; a first lens group 31 disposed at a position closer to the object side than the etalon 40; a second lens group 32 disposed at a position closer to the image side than the etalon 40; and an imaging element 13 that receives light passing through the second lens group 32 from the etalon 40. Parallel light collimated by the first lens group 31 is incident on the multiple planar elements, and the second lens group 32 constitutes an imaging optical system that images the light passing through the multiple planar elements onto the imaging element 13. Furthermore, the optical axis of the etalon 40 (and Z) E (The direction is parallel) and tilted relative to the optical axis of the imaging element 13. An anti-reflective film 70 is provided on the etalon 40.

[0113] Therefore, by suppressing the reflection of light on the first substrate 41 and the second substrate 42 of the standard etalon 40, even if a ghost image G is formed, the ghost image overlaps with the position of the real image T, thereby reducing the impact of the ghost image G on the measurement accuracy.

[0114] Fourth Implementation Method

[0115] Next, the fourth embodiment of this disclosure will be described.

[0116] In the third embodiment described above, an example is shown in which an anti-reflective film 70 is provided on a standard 40 that is tilted at an angle θ relative to the optical axis L of the imaging element 13. However, anti-reflective films may also be provided on the flat panel elements of the pre-amplifier and the post-amplifier disposed on the standard 40.

[0117] Figure 12 This is a diagram showing the flat panel element and the anti-reflective film 70 disposed on the flat panel element in the fourth embodiment.

[0118] In this embodiment, such as Figure 12 As shown, antireflective films 70 are provided on the protective glass 51 on the object side of the etalon 40, which is tilted at an angle θ relative to the optical axis L of the imaging element 13, and on the cover glass 52 on the image side of the etalon 40. That is, antireflective films 70 are provided on the +Z surface of the protective glass 51 and the -Z surface of the cover glass 52, respectively.

[0119] In this case, by suppressing the reflection of light on the cover glass 52, multiple reflections of light between the cover glass 52 and the first substrate 41 or the first reflective film 43 are suppressed. Similarly, by using the second substrate 42 or the second reflective film 44 to suppress the reflection of light towards the protective glass 51, multiple reflections of light between the protective glass 51 and the second substrate 42 or the second reflective film 44 are suppressed.

[0120] Therefore, similar to the third embodiment, even when a ghost image G with a ghost intensity of 1% or more is formed, its formation position overlaps with the formation position of the real image T, and its influence on measurement is extremely low.

[0121] The effect of this implementation method

[0122] The beam splitter 1 of this embodiment includes: multiple planar elements (protective glass 51, cover glass 52, bandpass filter 60, and etalon 40) including an etalon 40; a first lens group 31 disposed at a position closer to the object side than the etalon 40; a second lens group 32 disposed at a position closer to the image side than the etalon 40; and an imaging element 13 that receives light passing through the second lens group 32 from the etalon 40. Parallel light collimated by the first lens group 31 is incident on the multiple planar elements, and the second lens group 32 constitutes an imaging optical system that images the light passing through the multiple planar elements onto the imaging element 13. Furthermore, the optical axis of the etalon 40 (and Z) E (Parallel) Inclined relative to the optical axis of the imaging element 13, an anti-reflective film 70 is provided on the protective glass 51 of the front stage of the standard 40 and the cover glass 52 of the rear stage of the standard 40.

[0123] Therefore, by suppressing the reflection of light between the first substrate 41 and the cover glass 52, and between the second substrate 42 and the protective glass 51, the ghost image G is formed, and its position overlaps with the real image T, just as in the third embodiment, thereby reducing the impact of the ghost image G on the measurement accuracy.

[0124] Variations

[0125] The present invention is not limited to the above-described embodiments, and includes the following modifications within the scope of achieving the purpose of the present invention.

[0126] Variation Example 1

[0127] In the above embodiments, an example is shown where the bandpass filter 60 is positioned closer to the imaging element 13 than the etalon 40, but the bandpass filter 60 may also be positioned closer to the object than the etalon 40.

[0128] That is, as explained in the second embodiment, the reflected light at the Fresnel reflective interface of the plate element disposed on the image side of the etalon 40 is highly likely to become ghosting. Therefore, it is preferable to adopt a configuration in which the plate element is disposed as little as possible on the image side of the etalon 40. Therefore, by adopting a configuration in which the bandpass filter 60 is disposed closer to the object side (-Z side) than the etalon 40, the generation of ghosting can be suppressed more effectively.

[0129] Variation Example 2

[0130] In the above embodiment, the standard etalon 40, protective glass 51, cover glass 52, and bandpass filter 60 are exemplified as multiple flat panel elements, but other flat panel elements may also be configured. In this case, it is preferable to position the flat panel element closer to the object side than the standard etalon 40.

[0131] Variation Example 3

[0132] In the above embodiments, an example of a tilting element of the present disclosure being a etalon 40 is shown, but it is not limited thereto. For example, it could also be the Z-axis of the etalon 40. E The orientation is maintained parallel to the optical axis L (Z direction). Furthermore, any of the plate elements other than the etalon 40 can be a tilted element tilted relative to the optical axis L. In this case, by configuring the Fresnel reflection interface without the anti-reflective film 70 in the plurality of plate elements as shown in the first embodiment to be two or fewer surfaces, the effect of ghosting can also be suppressed. Additionally, by placing the tilted element in front of the etalon 40 (object side), the effect of ghosting can be suppressed in the same way as in the second embodiment. Alternatively, an anti-reflective film can be formed on the tilted element as in the third embodiment, or an anti-reflective film can be formed on the plate elements disposed before and after the tilted element as in the fourth embodiment.

[0133] This is a summary of the disclosure.

[0134] The first aspect of this disclosure relates to a beam splitter camera comprising: a plurality of flat panel elements, the plurality of flat panel elements including a etalon; a first lens group disposed at a position closer to the object side than the etalon; a second lens group disposed at a position closer to the image side than the etalon; and an imaging element that receives light from the etalon that has passed through the second lens group, wherein parallel light collimated by the first lens group is incident on the plurality of flat panel elements, the second lens group constituting an imaging optical system for imaging the light transmitted through the plurality of flat panel elements onto the imaging element, wherein among the plurality of flat panel elements on which the parallel light is incident, there are two or fewer Fresnel reflection interfaces without anti-reflective coatings.

[0135] Therefore, it is possible to suppress ghosting caused by multiple reflections of light at the Fresnel reflection interfaces of each plate element, and it is also possible to reduce manufacturing costs compared to the case where an anti-reflective film is applied to all plate elements.

[0136] The second aspect of this disclosure relates to a beam splitter camera comprising: a plurality of flat panel elements, the plurality of flat panel elements including a etalon; a first lens group disposed at a position closer to the object side than the etalon; a second lens group disposed at a position closer to the image side than the etalon; and an imaging element that receives light from the etalon that has passed through the second lens group, wherein parallel light collimated by the first lens group is incident on the plurality of flat panel elements, the second lens group constituting an imaging optical system that images the light transmitted through the plurality of flat panel elements onto the imaging element, and an antireflective coating is provided on one or more of the flat panel elements disposed at a position closer to the imaging element than the etalon.

[0137] Therefore, multiple reflections of light on the image-side plate element of the etalon, which contributes significantly to the formation of ghosting, can be suppressed. Thus, similarly to the first method, ghosting caused by multiple reflections of light at the Fresnel reflection interfaces of each plate element can be suppressed, and manufacturing costs can be reduced compared to the case where an anti-reflective film is provided on all plate elements.

[0138] The third aspect of this disclosure relates to a beam splitter camera comprising: a plurality of flat panel elements, the plurality of flat panel elements including a etalon; a first lens group disposed at a position closer to the object side than the etalon; a second lens group disposed at a position closer to the image side than the etalon; and an imaging element that receives light from the etalon that has passed through the second lens group, wherein parallel light collimated by the first lens group is incident on the plurality of flat panel elements, the second lens group constituting an imaging optical system for imaging light transmitted through the plurality of flat panel elements onto the imaging element, at least one of the plurality of flat panel elements being a tilting element having an optical axis tilted relative to the optical axis of the imaging element, and an antireflective coating being disposed on the tilting element.

[0139] Therefore, by suppressing the reflection of light on the tilting element, even if a ghost image is formed, the ghost image will overlap with the position of the real image, thereby reducing the impact of the ghost image on the measurement accuracy.

[0140] The fourth aspect of this disclosure relates to a beam splitter camera comprising: a plurality of flat panel elements, the plurality of flat panel elements including a etalon; a first lens group disposed at a position closer to the object side than the etalon; a second lens group disposed at a position closer to the image side than the etalon; and an imaging element that receives light from the etalon that has passed through the second lens group, wherein parallel light collimated by the first lens group is incident on the plurality of flat panel elements, the second lens group constituting an imaging optical system that images the light transmitted through the plurality of flat panel elements onto the imaging element, at least one of the plurality of flat panel elements is a tilting element having an optical axis tilted relative to the optical axis of the imaging element, and antireflective coatings are provided on the flat panel elements disposed before and after the tilting element.

[0141] Therefore, even if light is reflected by the tilting element, multiple reflections of light between the tilting element and the plate element in front of it, as well as multiple reflections between the tilting element and the plate element in the rear of it, can be suppressed. Thus, even if a ghost image is formed, it overlaps with the position of the real image, thereby reducing the impact of the ghost image on measurement accuracy.

[0142] In the beam splitter camera described above, the antireflective film is composed of multiple thin films with different refractive indices stacked together, and has a Fresnel reflectance of less than 0.5% relative to the wavelength range of the visible light region.

[0143] Therefore, it is possible to capture spectroscopic images with minimal ghosting effects using a spectroscopic camera.

Claims

1. A spectrophotometer, comprising: Multiple flat panel elements, the multiple flat panel elements including a standard etalon; The first lens group is positioned closer to the object side than the standard datum; The second lens assembly is positioned further on the image side than the standard etalon; and The imaging element receives light from the etalon that has passed through the second lens group. Parallel light, collimated by the first lens group, is incident on the multiple flat panel elements. The second lens assembly constitutes an imaging optical system that images light passing through the plurality of said flat panel elements onto the imaging element. Among the plurality of planar elements in which parallel light is incident, the Fresnel reflective interface without an anti-reflective film is on two or less sides.

2. A spectrophotometer, comprising: Multiple flat panel elements, the multiple flat panel elements including a standard etalon; The first lens group is positioned closer to the object side than the standard datum; The second lens assembly is positioned further on the image side than the standard etalon; and The imaging element receives light from the etalon that has passed through the second lens group. Parallel light, collimated by the first lens group, is incident on the multiple flat panel elements. The second lens assembly constitutes an imaging optical system that images light passing through the plurality of said flat panel elements onto the imaging element. One or more of the flat panel elements, positioned closer to the imaging element than the standard, are provided with an anti-reflective film.

3. A spectrophotometer, comprising: Multiple flat panel elements, the multiple flat panel elements including a standard etalon; The first lens group is positioned closer to the object side than the standard datum; The second lens assembly is positioned further on the image side than the standard etalon; and The imaging element receives light from the etalon that has passed through the second lens group. Parallel light, collimated by the first lens group, is incident on the multiple flat panel elements. The second lens assembly constitutes an imaging optical system that images light passing through the plurality of said flat panel elements onto the imaging element. At least one of the plurality of the flat plate elements is a tilting element having an optical axis tilted relative to the optical axis of the imaging element, and an anti-reflective film is provided on the tilting element.

4. A spectrophotometer, comprising: Multiple flat panel elements, the multiple flat panel elements including a standard etalon; The first lens group is positioned closer to the object side than the standard datum; The second lens assembly is positioned further on the image side than the standard etalon; and The imaging element receives light from the etalon that has passed through the second lens group. Parallel light, collimated by the first lens group, is incident on the multiple flat panel elements. The second lens assembly constitutes an imaging optical system that images light passing through the plurality of said flat panel elements onto the imaging element. At least one of the plurality of the flat panel elements is a tilting element having an optical axis tilted relative to the optical axis of the imaging element, and the flat panel elements disposed in the pre-stage and post-stage of the tilting element are provided with anti-reflective films.

5. The beam splitter according to claim 3 or 4, wherein, The tilt angle between the optical axis of the tilting element and the principal ray of the parallel light is greater than 0.5 degrees.

6. The spectrophotometer according to any one of claims 1 to 4, wherein, The antireflective film is composed of multiple thin films with different refractive indices stacked together, and has a Fresnel reflectance of less than 0.5% relative to the wavelength range of visible light.

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