Spectral imaging unit

Abstract

To provide a spectral imaging unit capable of capturing images with high resolution even in a wider wavelength range of light.SOLUTION: A spectral imaging unit (1) includes a collimator lens group (20) with a positive refractive power, a prism group (30), a focus lens group (40) with a positive refractive power, and a sensor (36) including an imaging element (36a). In the vertical direction of the sensor (36), when a wavelength range of at least 450 nm and 1700 nm or less is defined as a wavelength dispersion range with respect to an effective element vertical distance of the sensor (36), an incident angle (θ1-θ3), a focal length (f), and a tilt angle (α) are determined so as to satisfy a condition that the wavelength dispersion range is within a range of at least 70% and 90% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a spectral imaging unit, and more particularly to a spectral imaging unit that performs spectral analysis in the wavelength range of 450 nm to 1700 nm. [Background technology]

[0002] The spectral imaging unit is a device that receives light from multiple measurement points and forms an image on a sensor along the spatial and wavelength axes.

[0003] For example, Patent Document 1 discloses a spectral imaging unit that includes a slit at the incident end in the optical axis direction, and a glass plate, a collimator lens, a first prism, a grating, a second prism, a focus lens, and a sensor, arranged in this order from the slit in the longitudinal direction. The collimator lens, first prism, grating, second prism, and focus lens form an imaging optical system that uses incident light to form an image. The sensor is installed with its upper side tilted away from the slit relative to the optical axis. In the spectral imaging unit of Patent Document 1, a processor connected to the spectral imaging unit calculates transmission characteristics based on the imaging results obtained by the sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-139605 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, short wave infrared (SWIR) radiometer sensors have become sensitive to wavelengths ranging from the visible range (visible light) to the near infrared range (near infrared light), and as the number of pixels increases and pixel size decreases, there is a growing demand for spectroscopic cameras with high wavelength resolution and high resolution. However, when using a sensor that can cover the visible to near-infrared range, conventional spectral imaging units may not be able to achieve the desired wavelength resolution and resolution because the wavelength range of light is wide, from 450 to 1700 nm.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide a spectral imaging unit that can capture images with high wavelength resolution and high resolution even in a wider range of light wavelength bands. [Means for solving the problem]

[0007] The spectral imaging unit of the present invention is a spectral imaging unit having, in order from a slit into which light is incident, a collimator lens group having positive refractive power, a spectroscopic element group (prism group), a focus lens group having positive refractive power, and a sensor having an image sensor, When the wavelength of the light emitted from the dispersive element group is 1700 nm, the angle of incidence at the focus lens group is 0.691 degrees or more and 1.514 degrees or less; when the wavelength of the light emitted from the dispersive element group is 1075 nm, the angle of incidence at the focus lens group is 3.542 degrees to 5.408 degrees; when the wavelength of the light emitted from the dispersive element group is 450 nm, the angle of incidence at the focus lens group is 8.819 degrees or more and 9.614 degrees or less; The focal length (f) of the focus lens group is 30 mm or more and 40 mm or less, The tilt angle of the sensor (SWIR sensor) with respect to the optical axis of the focus lens group is between 73.097 degrees and 84.348 degrees, In the vertical direction of the sensor, if the wavelength range (ΔH) of 450 nm to 1700 nm inclusive relative to the effective element vertical distance (Hs) of the sensor is defined as the wavelength dispersion range (ΔH / Hs), the incident angle, focal length, and tilt angle are determined so that the wavelength dispersion range is in the range of 70% to 90%. [Effects of the Invention]

[0008] The spectral imaging unit of the present invention includes a collimator lens group having positive refractive power, a dispersing element group, a focus lens group having positive refractive power, and a sensor having an image sensor. When the wavelength of light emitted from the dispersing element group is 1700 nm, the angle of incidence on the focus lens group is 0.691 degrees or more and 1.514 degrees or less. When the wavelength of light emitted from the dispersing element group is 1075 nm, the angle of incidence on the focus lens group is 3.542 degrees to 5.408 degrees. When the wavelength of light emitted from the dispersing element group is 450 nm, the angle of incidence on the focus lens group is 8.819 degrees or more and 9.614 degrees or less. The focal length of the focus lens group is 30 mm or more and 40 mm or less, and the tilt angle of the sensor with respect to the optical axis of the focus lens group is 73.097 degrees or more and 84.348 degrees or less. In the vertical direction of the sensor, if the wavelength range (ΔH) between 450 nm and 1700 nm inclusive relative to the sensor's effective element vertical distance (Hs) is defined as the wavelength dispersion range (ΔH / Hs), the incident angle, focal length, and tilt angle are determined so that the wavelength dispersion range is between 70% and 90% inclusive. Therefore, according to the spectral imaging unit having the above configuration, it is possible to provide a spectral imaging unit that can capture images with high wavelength resolution and high resolution even in a wider range of light wavelength bands. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a configuration of a spectral imaging unit 1 according to an embodiment. [Figure 2] FIG. 1 is a perspective view showing the appearance of a spectral imaging unit according to an embodiment. [Figure 3] 3A and 3B are diagrams for explaining the prism group 30, in which FIG. 3A is a diagram for explaining the angles of incidence θ1 to θ3 on the surface 41a perpendicular to the optical axis of the convex lens 41 for incident light wavelengths of 1700 nm, 1075 nm, and 450 nm, and FIG. 3B is a diagram for explaining the angle of the inclined surface 32a of the prism 32. [Figure 4] 10 is a diagram for explaining the focal length f of the focus lens group 40 and the tilt angle α of the image sensor 36a that constitutes the sensor. [Figure 5] 5A and 5B are plan views of the image sensor 36a constituting the sensor 36, where FIG. 5A shows an image of light corresponding to wavelengths of 450 nm, 1075 nm, and 1700 nm, and FIG. 5B shows the imaging surface of the image sensor 36a. [Figure 6] 10 is a table showing setting parameters in setting examples 1 to 3 and a comparative example of the spectral imaging unit 1. [Figure 7] 7A and 7B are tables showing the setting parameters in setting example 1 of the spectral imaging unit 1, where FIG. 7A is a diagram showing the setting parameters of the collimator lens group, the prism group, and the focus lens group, and FIG. 7B is a table showing the angle of incidence (see FIG. 3A) of the surface 41a perpendicular to the optical axis of the convex lens 41 constituting the focus lens group 40 with respect to the optical axis for three types of wavelengths. [Figure 8] 8(a) and 8(b) are tables showing the setting parameters in setting example 2 of the spectral imaging unit 1, where FIG. 8(a) is a table showing the setting parameters of the collimator lens group, the prism group, and the focus lens group, and FIG. 8(b) is a table showing the angle of incidence with respect to the optical axis of the surface 41a perpendicular to the incident side optical axis of the convex lens 41 constituting the focus lens group 40, for three types of wavelengths. [Figure 9] 9(a) and 9(b) are tables showing the setting parameters in setting example 3 of the spectral imaging unit 1, where FIG. 9(a) is a table showing the setting parameters of the collimator lens group, the prism group, and the focus lens group, and FIG. 9(b) is a table showing the angle of incidence with respect to the optical axis of the surface 41a perpendicular to the optical axis of the convex lens 41 constituting the focus lens group 40, for three types of wavelengths. DETAILED DESCRIPTION OF THE INVENTION

[0010] The configuration of the spectral imaging unit 1 according to the embodiment will be described below with reference to the drawings.

[0011] <Overall configuration of Spectroscopic Imaging Unit 1> FIG. 1 is a diagram showing the configuration of a spectral imaging unit 1 according to an embodiment. FIG. 2 is a perspective view showing the appearance of the spectral imaging unit of the present invention. FIG. 3 is a diagram for explaining the prism group 30, in which FIG. 3(a) is a diagram for explaining angles of incidence θ1 to θ3 on a surface 41a perpendicular to the optical axis of a convex lens 41 for incident light wavelengths of 1700 nm, 1075 nm, and 450 nm, and FIG. 3(b) is a diagram for explaining the angle of the inclined surface 31a of a prism 32. FIG. 4 is a diagram for explaining the focal length f of the focus lens group 40 and the tilt angle α of the sensor 36.

[0012] 1 to 4 is the longitudinal direction of the spectral imaging unit 1, and the up-down direction of FIGS. 1 to 4 is the up-down direction of the spectral imaging unit 1. The front-to-back direction of the spectral imaging unit 1 is also the traveling direction of light (optical axis direction). In addition, in each drawing for explaining the embodiments, members having the same functions are given the same reference numerals, and redundant explanations may be omitted.

[0013] 1 to 4, the spectral imaging unit 1 includes a slit 14 provided at an incident end (not shown) in the optical axis direction, a collimator lens group (combined convex lens) 20, a spectroscopic element group (hereinafter referred to as a "prism group") 30, a focus lens group (combined convex lens) 40, and a sensor 36. The collimator lens group 20, the prism group 30, and the focus lens group 40 form an imaging optical system used to image incident light. An image processing device 39, which will be described later, is connected to the sensor 36 (see FIG. 2(a)).

[0014] In the spectral imaging unit 1, the positions of the objective lens 38 (see FIG. 2(a)), which receives light from the subject, and the slit 14 are determined so that light enters the slit (entrance opening) 14 provided on the front side of the spectral imaging unit 1 in the front-to-back direction. The slit 14 extends in a direction (hereinafter referred to as the "vertical direction") perpendicular to the front-to-back direction of the spectral imaging unit 1, and its height in the vertical direction is narrow. Note that reference numeral 50 in FIG. 2(b) denotes a slit fixing member provided on the entrance side of the collimator lens group 20.

[0015] An image processing device (not shown) is connected to the spectral imaging unit 1, and the image processing device has an image processing section (not shown) that processes information received by the sensor 36 into image information, etc. The image processing section is composed of a microprocessor such as a CPU (Central Processing Unit), a memory, etc.

[0016] The image processing device 39 may include a display unit (not shown) that displays the measurement results and the like. The display unit may be, for example, a liquid crystal or organic electroluminescence (EL) display. The display unit may also be a separate unit. The image processing device 39 may also include a storage unit (not shown) therein that stores the image data and analysis results from the image processing device 39. As the storage unit, various types of storage devices may be used as needed, such as a hard disk drive (HDD) or a solid state drive (SSD).

[0017] <Collimator lens group> The collimator lens group 20 is a combined convex lens that combines a cemented lens 21 and a convex lens 22, and has positive refractive power. No optical components are arranged between the slit 14 and the collimator lens group 20. Generally, a mirror (optical component) is arranged for the purpose of changing the optical path, and an aspherical lens (optical component) or a spherical lens (optical component) is arranged for the purpose of aberration correction, but in this embodiment, no optical components are arranged between the slit 14 and the collimator lens group 20 because the optical path is not changed or aberration correction is not performed.

[0018] <Prism group> As shown in FIG. 3(a), the prism group 30 includes a grating 33, an incident-side prism 31, and an exit-side prism 32. The incident-side prism 31 is arranged such that its vertical surface 31b faces the grating 33 and its inclined surface 31a faces the collimator lens group 26. The exit-side prism 32 is arranged such that its vertical surface 32b faces the grating 33 and its inclined surface 32a faces the focus lens group 40, which will be described later. The incident-side prism 31 and the exit-side prism 32 are prisms for angle correction. The grating 33 is for wavelength dispersion. The incident-side prism 31 has an upper inclined surface 31c, and the exit-side prism 32 has an upper inclined surface 32c. The inclination angle (wedge angle) β (see FIG. 3(b)) of the upper inclined surfaces 31c and 32c relative to the optical axis direction is 11.35 degrees in the embodiment described below, but is not limited to this. Note that the upper inclined surface 31c is not shown in the drawings because it has a symmetrical configuration with the upper inclined surface 32c.

[0019] <Focus lens group> 4, focus lens group 40 is a combination lens that combines a convex lens 41 with a cemented lens 42 made up of a biconvex lens and a concave lens, and has positive refractive power. The focal length f of focus lens group 40 is the distance from the principal plane of focus lens group 40 to image sensor 36a, which will be described later, and is preferably 30 to 40 mm. Furthermore, if the angle of incidence of light emitted from exit-side prism 32 at a wavelength of 1700 nm onto surface 41a perpendicular to the optical axis of convex lens 41 is denoted by θ1, the angle of incidence of light emitted at a wavelength of 1075 nm onto surface 41a perpendicular to the optical axis of convex lens 41 is denoted by θ2, and the angle of incidence of light emitted at a wavelength of 450 nm onto surface 41a perpendicular to the optical axis of convex lens 41 is denoted by θ3, these angles of incidence θ1 to θ3 are preferably 3.542 degrees to 5.408 degrees. Note that the principal plane is the locus described by the intersection of two straight lines extending the light rays before and after they enter the optical system while changing their height, parallel to the optical axis.

[0020] <Sensor> The sensor 36 is a two-dimensional optical sensor (image sensor) and includes an image sensor 36a and a sensor cover 36b (see FIG. 1). The sensor 36 is capable of detecting light ranging from visible light to near-infrared light, for example, in a wavelength range of 450 nm to 1700 nm. The sensor may also be configured to detect light in other wavelength ranges. The sensor 36 is installed with an inclination such that its upper side approaches the slit 14 relative to the optical axis direction (front-to-back direction). The inclination angle α (see FIG. 4) of the upper side of the sensor 36 relative to the optical axis direction is preferably in the range of 73.097 degrees to 84.327 degrees. The reason for inclining within this range is that if the wavelength range of light is 450 nm to 1700 nm and the inclination angle of the sensor 36 is 90 degrees, the image will not be clearly formed, resulting in blurring at points with different wavelengths.

[0021] The image sensor 36a has a large number of light-receiving elements arranged two-dimensionally and has a square or rectangular shape (see FIG. 5(b)). Each light-receiving element converts the light received by that element into an electrical signal. When the sensor 36 is installed as shown in FIG. 4, the horizontal direction of the image sensor 36a (the direction of arrow A in FIG. 5(b)) is the spatial axis, and the vertical direction of the image sensor 26a (the direction of arrow B in FIG. 5(b)) is the wavelength axis. That is, each piece of light information from the horizontally extending slit 14 is imaged on the spatial axis (the direction of arrow B in FIG. 5(b)) corresponding to the horizontal position of the slit 14. Furthermore, the light from the slit 14 forms an image of each wavelength in the vertical direction, as shown in FIG. 5(a). FIG. 5(a) shows images of three wavelengths: 450 nm (cross mark), 1075 nm (square mark), and 1700 nm (triangle mark). When the spectral imaging unit 1 of the embodiment is used, the characteristics are shown in the case where the wavelength becomes longer as it goes up in the vertical direction.

[0022] Light from the slit 14 is dispersed through the collimator lens group 20 and the prism group 30, and finally focused on the sensor 36 through the focus lens group 40, and then imaged on the image sensor 36a through the sensor cover 36b. As shown in FIG. 5(a), the light imaged on the image sensor 36a is formed within a dispersion range of ΔH on the vertical axis. Here, ΔH is the wavelength range from the position of a wavelength of 450 nm (the line connecting the triangle marks in FIG. 5(a) in the horizontal direction) to the position of a wavelength of 1700 nm (the line connecting the circle marks in FIG. 5(a) in the horizontal direction), and Hs is the effective vertical distance of the image sensor 36a.

[0023] <Spectral Imaging Unit 1 setting example> Below are shown the angle of incidence onto the focus lens group mentioned above, the focal length (f) of the focus lens group, the setting details for setting the tilt angle of the focus lens group optical axis with respect to the optical axis of the sensor (SWIR sensor) to a predetermined value, the wavelength dispersion range (ΔH / Hs) after setting, and the wavelength resolution for each of the three wavelengths of light emitted from the collimator lens group: 450 nm, 1075 nm, and 1700 nm. Note that the wavelength resolution represents the fineness of the wavelengths that can be separated within the wavelength range, and is calculated by multiplying the width of the slit that adjusts the amount of incident light by the reciprocal linear dispersion number (the wavelength width per unit length (1 mm) on the slit).

[0024] [Setting example 1] FIG. 7 is a table showing setting parameters in Setting Example 1 of the spectral imaging unit 1. FIG. 7(a) is a diagram showing setting parameters for the collimator lens group, prism group, and focus lens group. FIG. 7(b) is a diagram showing the angle of incidence (see FIG. 3(a)) of the surface 41a of the convex lens 41 constituting the focus lens group 40 relative to the optical axis, which is perpendicular to the optical axis, for three wavelengths. Surface 1 represents the slit 14, Surfaces 2 to 7 represent the collimator lens group, Surfaces 9 to 13 represent the prism group, Surfaces 15 to 21 represent the focus lens group, and Surface 22 represents the sensor cover (glass) 36b. Details of Setting Example 1 are described below. Note that Surfaces 4, 5, 7, 8, 10, 12, 14, 16, 17, 20, and 21 represent gaps (air) between lenses, and so their details are omitted. (Surface1: slit) Thickness: 31.157mm Line spacing (slit width): 20μm (Surface 2: Concave lens that makes up cemented lens 21) ·Curvature radius: 165.200 Thickness: 1.700mm ND (refractive index): 1.805 vd (Abbe number): 25.360 (Surface 3: biconvex lens that makes up cemented lens 21) ·Curvature radius: 33.000 Thickness: 6.000mm ND (refractive index): 1.651 vd (Abbe number): 55.892 (Surface 6: convex lens 22) ·Curvature radius: 44.500 Thickness: 5.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 (Surface 9: Prism 31) Thickness: 5.510mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Wedge angle β of slope 31c (see Figure 3(b)): 11.35 degrees (Surface10: Grating 33) Thickness: 3.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Line count: 110 / mm (Surface 13: Prism 32) Thickness: 5.510mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Wedge angle β of slope 32c (see Figure 3(b)): 11.35 degrees (Surface 15: convex lens 41) ·Curvature radius: 289.000 Thickness: 5.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 (Surface 18: biconvex lens that makes up cemented lens 42) ·Curvature radius: 39.480 Thickness: 6.000mm ND (refractive index): 1.651 vd (Abbe number): 55.892 (Surface 19: Concave lens that makes up cemented lens 42) ·Curvature radius: 33.000 Thickness: 1.700mm ND (refractive index): 1.805 vd (Abbe number): 25.360 (Surface22: Sensor cover 36b) Thickness: 1.100mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Sensor tilt angle α relative to the optical axis (see Figure 4): 73.097 degrees (chromatic dispersion range (ΔH / Hs)) Incident light wavelength 1700nm: Incident angle 0.691 degrees Incident light wavelength 1075nm: Incident angle 4.882 degrees Incident light wavelength 450nm: Incident angle 9.390 degrees Focus lens group focal length (f): 35,000 mm ΔH=5.50mm Hs=7mm Chromatic dispersion range (ΔH / Hs): 78% Optical wavelength resolution (incident light wavelength 1075nm, slit width 20μm): 4.66nm

[0025] <Comparative example of a spectroscopic imaging unit> Below, for each of the three wavelengths of light emitted from the collimator lens group (spectral element group (PGP)) of 450 nm, 1075 nm, and 1700 nm, the angle of incidence onto the focus lens group, the focal length (f) of the focus lens group, and the tilt angle of the sensor (SWIR sensor) with respect to the optical axis of the focus lens group are set to predetermined values. The settings, wavelength dispersion range (ΔH / Hs) after setting, and wavelength resolution in a comparative example are shown below. Note that the wavelength resolution is calculated by multiplying the width of the slit, which adjusts the amount of incident light, by the reciprocal linear dispersion. The reciprocal linear dispersion refers to the wavelength width per unit length (1 mm) on the slit. Sensor tilt angle α relative to the optical axis (see Figure 4): 62.89 degrees (chromatic dispersion range (ΔH / Hs)) Incident light wavelength 1700nm: Incident angle 1.112 degrees Incident light wavelength 1075nm: Incident angle 1.484 degrees Incident light wavelength 450nm: Incident angle 4.208 degrees Focus lens group focal length (f): 28.26mm ΔH=2.295mm Hs=7mm Chromatic dispersion range (ΔH / Hs): 32.7% Optical wavelength resolution (incident light wavelength 1075nm, slit width 20μm): 11.038nm

[0026] (Effect of setting example 1) In the spectral imaging unit configured in the comparative example, the wavelength dispersion range (ΔH / Hs) is 32.7%, and the optical wavelength resolution, which depends on wavelength dispersion, is 11.038 nm. On the other hand, in the spectral imaging unit 1 configured in setting example 1, the wavelength dispersion range (ΔH / Hs) can be increased to 78%, and the optical wavelength resolution is 4.66 nm. Therefore, compared to the comparative example, the wavelength dispersion range can be widened and the optical wavelength resolution (nm) also increases (the lower the optical wavelength resolution value, the better the resolution). Therefore, the ability to distinguish between subjects (imaged objects) is improved.

[0027] [Setting example 2] FIG. 8 shows setting parameters for setting example 2 of the spectral imaging unit 1. FIG. 8(a) shows setting parameters for the collimator lens group, prism group, and focus lens group. FIG. 8(b) shows the angle of incidence of light with respect to the optical axis of surface 41a, which is perpendicular to the optical axis of convex lens 41 constituting focus lens group 40, for three wavelengths. Surface 1 represents slit 14, Surfaces 2 to 7 represent collimator lens groups, Surfaces 9 to 13 represent prism groups, Surfaces 15 to 21 represent focus lens groups, and Surface 22 represents sensor cover (glass) 36b. Details of setting example 2 are described below. Note that Surfaces 4, 5, 7, 8, 10, 12, 14, 16, 17, 20, and 21 represent gaps (air) between lenses, and so their details are omitted. (Surface1: slit) Thickness: 31.157mm Line spacing (slit width): 20μm (Surface 2: Concave lens that makes up cemented lens 21) ·Curvature radius: 165.200 Thickness: 1.700mm ND (refractive index): 1.805 vd (Abbe number): 25.360 (Surface 3: biconvex lens that makes up cemented lens 21) ·Curvature radius: 33.000 Thickness: 6.000mm ND (refractive index): 1.651 vd (Abbe number): 55.892 (Surface 6: convex lens 22) ·Curvature radius: 44.500 Thickness: 5.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 (Surface 9: Prism 31) Thickness: 5.510mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Wedge angle β of slope 31c (see Figure 3(b)): 11.35 degrees (Surface10: Grating 33) Thickness: 3.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Line count: 131 / mm (Surface 13: Prism 32) Thickness: 5.510mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Wedge angle β of slope 32c (see Figure 3(b)): 11.35 degrees (Surface 15: convex lens 41) ·Curvature radius: 289.000 Thickness: 5.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 (Surface 18: biconvex lens that makes up cemented lens 42) ·Curvature radius: 39.480 Thickness: 6.000mm ND (refractive index): 1.651 vd (Abbe number): 55.892 (Surface 19: Concave lens that makes up cemented lens 42) ·Curvature radius: 33.000 Thickness: 1.700mm ND (refractive index): 1.805 vd (Abbe number): 25.360 (Surface22: Sensor cover 36b) Thickness: 1.100mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Sensor tilt angle α relative to the optical axis (see Figure 4): 84.325 degrees (chromatic dispersion range (ΔH / Hs)) Incident light wavelength 1700nm: Incident angle 1.412 degrees Incident light wavelength 1075nm: Incident angle 3.542 degrees Incident light wavelength 450nm: Incident angle 8.819 degrees Focus lens group focal length (f): 35,000 mm ΔH=6.24mm ·Hs=7mm ·Wavelength dispersion range (ΔH / Hs):89% Optical wavelength resolution (incident light wavelength 1075nm, slit width 20μm): 4.09nm

[0028] (Effect of setting example 2) According to the spectral imaging unit 1 configured in the above setting example 2, the wavelength dispersion range (ΔH / Hs) can be increased to 89%, and the optical wavelength resolution, which depends on wavelength dispersion, is 4.09 nm. Therefore, compared to the above comparative example, the wavelength dispersion range can be widened and the optical wavelength resolution (nm) is also increased. Therefore, the ability to distinguish between subjects (image-taking objects) is improved.

[0029] [Setting example 3] FIG. 9 shows setting parameters for setting example 3 of the spectral imaging unit 1. FIG. 9(a) shows setting parameters for the collimator lens group, prism group, and focus lens group. FIG. 9(b) shows the angle of incidence of light with respect to the optical axis of surface 41a, which is perpendicular to the optical axis of convex lens 41 constituting focus lens group 40, for three wavelengths. Surface 1 represents slit 14, Surfaces 2 to 7 represent collimator lens groups, Surfaces 9 to 13 represent prism groups, Surfaces 15 to 21 represent focus lens groups, and Surface 22 represents sensor cover (glass) 36b. Details of setting example 3 are described below. Note that Surfaces 4, 5, 7, 8, 10, 12, 14, 16, 17, 20, and 21 represent gaps (air) between lenses, and so their details are omitted. (Surface1: slit) Thickness: 31.157mm Line spacing (slit width): 20μm (Surface 2: Concave lens that makes up cemented lens 21) ·Curvature radius: 165.200 Thickness: 1.700mm ND (refractive index): 1.805 vd (Abbe number): 25.360 (Surface 3: biconvex lens that makes up cemented lens 21) ·Curvature radius: 33.000 Thickness: 6.000mm ND (refractive index): 1.651 vd (Abbe number): 55.892 (Surface 6: convex lens 22) ·Curvature radius: 44.500 Thickness: 5.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 (Surface 9: Prism 31) Thickness: 5.510mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Wedge angle β of slope 31c (see Figure 3(b)): 11.35 degrees (Surface10: Grating 33) Thickness: 3.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Line count: 102 / mm (Surface 13: Prism 32) Thickness: 5.510mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Wedge angle β of slope 32c (see Figure 3(b)): 11.35 degrees (Surface 15: convex lens 41) ·Curvature radius: 289.000 Thickness: 5.000mm ND (refractive index): 1.517 vd (Abbe number): 64.167 (Surface 18: biconvex lens that makes up cemented lens 42) ·Curvature radius: 39.480 Thickness: 6.000mm ND (refractive index): 1.651 vd (Abbe number): 55.892 (Surface 19: Concave lens that makes up cemented lens 42) ·Curvature radius: 33.000 Thickness: 1.700mm ND (refractive index): 1.805 vd (Abbe number): 25.360 (Surface22: Sensor cover 36b) Thickness: 1.100mm ND (refractive index): 1.517 vd (Abbe number): 64.167 Inclination angle α of the sensor relative to the optical axis (see Figure 4): 84.348 degrees (chromatic dispersion range (ΔH / Hs)) Incident light wavelength 1700nm: Incident angle 1.514 degrees Incident light wavelength 1075nm: Incident angle 5.408 degrees Incident light wavelength 450nm: Incident angle 9.614 degrees Focus lens group focal length (f): 35,000 mm ΔH=4.90mm Hs=7mm Chromatic dispersion range (ΔH / Hs): 70% Optical wavelength resolution (incident light wavelength 1075nm, slit width 20μm): 5.23nm

[0030] (Effect of setting example 3) According to the spectral imaging unit 1 configured in the above setting example 3, the wavelength dispersion range (ΔH / Hs) can be increased to 70%, and the optical wavelength resolution, which depends on wavelength dispersion, is 5.23 nm. Therefore, compared to the above comparative example, the wavelength dispersion range can be widened and the optical wavelength resolution (nm) is also increased. Therefore, the ability to distinguish between subjects (image-taking objects) is improved.

[0031] [Effects of the embodiment] The spectral imaging unit 1 according to the embodiment includes a collimator lens group 20 having positive refractive power, a prism group 30, a focus lens group 40 having positive refractive power, and a sensor 36 including an image sensor 36a. When the wavelength of light emitted from the prism group 30 is 1700 nm, the angle of incidence at the focus lens group 40 is 0.691 degrees or more and 1.514 degrees or less, when the wavelength of light emitted from the prism group 30 is 1075 nm, the angle of incidence at the focus lens group 40 is 3.542 degrees to 5.408 degrees, and when the wavelength of light emitted from the prism group 30 is 450 nm, the angle of incidence at the focus lens group 40 is 8.819 degrees or more and 9.614 degrees or less. The focal length of focus lens group 40 is 30 mm or more and 40 mm or less, and the tilt angle of focus lens group 40 with respect to the optical axis of sensor 36 is 73.097 degrees or more and 84.348 degrees or less. In the vertical direction of sensor 36, if the wavelength range (ΔH) of 450 nm or more and 1700 nm or less for the effective element vertical distance (Hs) of sensor 36 is defined as the chromatic dispersion range (ΔH / Hs), the incident angles θ1 to θ3, focal length f, and sensor tilt angle α are determined so that the chromatic dispersion range is 70% or more and 90% or less. Therefore, the spectral imaging unit 1 having the above configuration can provide a spectral imaging unit that can capture images with high resolution even in a wider range of light wavelength bands.

[0032] According to the spectral imaging unit 1 of the embodiment, there are no optical components between the slit 14 and the collimator lens group 20, so that the cost of the spectral imaging unit 1 can be reduced.

[0033] According to the spectroscopic imaging unit 1 of the embodiment, the collimator lens group 20 and the focus lens group 40 are composed of the same lens components and are configured symmetrically with the prism group 30 in between, which reduces the manufacturing costs of the collimator lens group 20 and the focus lens group 40.

[0034] According to the spectral imaging unit 1 of the embodiment, the prism group 30 includes a grating 33 and a pair of prisms 31 and 32 that are arranged on either side of the grating 33 and have the same wedge angle β. This reduces the manufacturing cost of the prism group 30.

[0035] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. [Explanation of symbols]

[0036] 1...spectral imaging unit, 14...slit, 20...collimator lens group, 30...prism group (spectral element group), 33...grating (diffraction grating), 36...sensor, 36a...imaging element, 40...focus lens group

Claims

1. A spectral imaging unit having, in order from a slit through which light is incident, a collimator lens group having positive refractive power, a spectroscopic element group, a focus lens group having positive refractive power, and a sensor having an image sensor, When the wavelength of the light emitted from the dispersive element group is 1700 nm, the angle of incidence at the focus lens group is 0.691 degrees or more and 1.514 degrees or less; when the wavelength of the light emitted from the dispersive element group is 1075 nm, the angle of incidence at the focus lens group is 3.542 degrees to 5.408 degrees; when the wavelength of the light emitted from the dispersive element group is 450 nm, the angle of incidence at the focus lens group is 8.819 degrees or more and 9.614 degrees or less; the focal length of the focus lens group is 30 mm or more and 40 mm or less, an inclination angle of the sensor with respect to the optical axis of the focus lens group is equal to or greater than 73.097 degrees and equal to or less than 84.348 degrees; In the vertical direction of the sensor, when a wavelength range of 450 nm or more and 1700 nm or less with respect to the effective element vertical distance of the sensor is defined as a wavelength dispersion range, the incident angle, the focal length, and the tilt angle are determined so as to satisfy that the wavelength dispersion range is a range of 70% or more and 90% or less. A spectroscopic imaging unit characterized by:

2. No optical component is disposed between the slit and the collimator lens group. The spectroscopic imaging unit according to claim 1 .

3. the collimator lens group and the focus lens group are configured with lens components of the same shape and are arranged at positions spaced the same distance apart with the spectroscopic element group in between; 3. The spectral imaging unit according to claim 1 or 2.

4. the light-splitting element group includes a grating and a pair of prisms that are arranged symmetrically with respect to the grating and have the same wedge angle; 3. The spectral imaging unit according to claim 1 or 2.

Images