Spectral imaging unit

Abstract

To provide a spectroscopic imaging unit which enables more accurate measurement even in a wider range of wavelength bands of light.SOLUTION: The spectroscopic imaging unit comprises an incidence port from which light enters, a plate glass, an image-forming optical system, and a sensor. The sensor includes an imaging element, and a sensor cover which is provided to the incidence side of the light of the imaging element. The sensor is included by being inclined at a prescribed angle with respect to a plane perpendicular to the traveling direction of the light. The plate glass is constructed with a material having the same optical characteristics as, and in the same thickness as the sensor cover. The plate glass is provided to the sensor cover in an inclined state of being rotated 90° with the traveling direction of the light as a central axis, and the light from the incidence port is formed into an image in the imaging element via the plate glass, the image-forming optical system and the sensor cover.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a spectroscopic imaging unit, and particularly to a spectroscopic imaging unit suitable for measuring a wider wavelength band of light.

Background Art

[0002] A spectroscopic imaging unit is an apparatus capable of analyzing the properties of a substance by receiving light from a plurality of measurement locations and forming an image on a sensor in the spatial axis and the wavelength axis.

[0003] For example, in Patent Document 1, the other ends of the incident fiber and the output fiber are configured to be applied perpendicularly to the surface of the measurement object, and the other end positions of the plurality of output fibers are respectively arranged at different distances from the end position of the incident fiber. The spectroscopic imaging unit forms an image of the light obtained from the plurality of output fibers on a photosensor, and the processing device calculates the transmission characteristics based on the imaging result obtained by the photosensor. A characteristic measurement system is disclosed.

[0004] On the other hand, recently, sensors that can cover not only the wavelength band of visible light but also the wavelength band of near-infrared light in addition to the wavelength band of visible light, and sensors that can handle a wide range of wavelength regions have been developed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, when using a sensor that can cover visible light to near-infrared light, there are cases where the image is not clearly formed even when the sensor is installed in the conventional spectroscopic imaging unit method. This is due to the influence of the wide range of the wavelength of light from 450 to 1700 nm. In this case, an event occurs where the images of short wavelengths and long wavelengths cannot be perfectly aligned.

[0007] At this time, a method of tilting the sensor can be considered. However, when the tilt angle becomes large, it causes the imaging characteristics to deteriorate due to the influence of the cover glass that protects the sensor. Also, in a wide wavelength range, the influence of secondary light occurs, which may have an adverse effect on the measurement results.

[0008] In view of the above problems, an object of the present invention is to provide a spectroscopic imaging unit capable of more accurate measurement even in a wider wavelength band of light.

Means for Solving the Problems

[0009] To achieve the above object, one of the typical spectroscopic imaging units of the present invention has an entrance for light to enter, a plate glass, an imaging optical system, and a sensor. The sensor includes an imaging element and a sensor cover provided on the light incident side of the imaging element. The sensor is provided with a predetermined angle of inclination with respect to a plane perpendicular to the light traveling direction. The plate glass is composed of the same material and the same thickness as the sensor cover and has the same optical characteristics. The plate glass is provided in an inclined state rotated 90° around the light traveling direction with respect to the sensor cover. The light from the entrance is imaged on the imaging element through the plate glass, the imaging optical system, and the sensor cover.

Effects of the Invention

[0010] According to the present invention, in the spectroscopic imaging unit, more accurate measurement can be performed even in a wide wavelength band of light. Problems, configurations, and effects other than the above will be clarified by the following embodiments.

Brief Description of the Drawings

[0011]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0012] A mode for carrying out the present invention will be described.

[0013] <Configuration of Spectroscopic Imaging Unit> FIG. 1 is a perspective view showing a first application example of the spectroscopic imaging unit of the present invention. FIG. 2 is a perspective view showing a second application example of the spectroscopic imaging unit of the present invention. FIG. 3 is a perspective side view showing an embodiment of the spectroscopic imaging unit of the present invention. FIG. 4 is a perspective top view showing an embodiment of the spectroscopic imaging unit of the present invention. The left-right direction in FIGS. 1 to 4 is the longitudinal direction (Z direction) of the spectroscopic imaging unit 20, the up-down direction in FIGS. 1 to 3 is the up-down direction (Y direction) of the spectroscopic imaging unit 20, and the up-down direction in FIG. 4 is the lateral direction (X direction) of the spectroscopic imaging unit 20. Note that the longitudinal direction (Z direction) of the spectroscopic imaging unit 20 is also the traveling direction of light (optical axis direction).

[0014] FIG. 1 shows an example in which the spectroscopic imaging unit 20 is provided with the slit 14. At this time, the light passing through the objective lens 13 is set to be incident on the slit 14 provided on the side surface in the Z direction of the spectroscopic imaging unit 20. The slit 14 is provided to extend in the X direction (lateral direction) with the X direction (lateral direction) of the spectroscopic imaging unit 20 as the longitudinal direction, and the Y direction (vertical direction) is narrow. At this time, the slit 14 is set to extend laterally at the upper and lower center positions of the two-dimensional sensor 26. Thereby, in FIG. 1, the slit 14 extending in the lateral direction serves as the entrance 10. The objective lens 13 can be configured to be held, for example, in a lens barrel provided in an integrating sphere. Further, the spectroscopic imaging unit 20 and the objective lens 13 may be relatively moved in the Y direction (vertical direction) with respect to the measurement object.

[0015] FIG. 2 shows an example in which one end 15a of each of the plurality of optical fibers 15 is connected to the spectroscopic imaging unit 20. At this time, the tips of one ends 15a of the plurality of optical fibers 15 are set to be arranged laterally at the upper and lower center positions of the two-dimensional sensor 26. Thereby, in FIG. 2, one ends 15a of the plurality of optical fibers 15 arranged laterally serve as the entrance 10. The number of the plurality of optical fibers 15 is, for example, 4 or more, and further 8 or more. The other ends of the plurality of optical fibers 15 are installed at desired positions and receive light there.

[0016] As shown in FIGS. 1 to 4, the spectroscopic imaging unit 20 is an achromatic spectrometer that includes an entrance 10 at the incident-side end in the Z direction (optical axis direction), and includes a glass plate 28, a combined convex lens 21, a prism 22, a grating 23, a prism 24, a combined convex lens 25, and a sensor 26 in this order in the longitudinal direction. The spectroscopic imaging unit 20 also includes an image processing unit 27, and performs processing such as using the information received by the sensor 26 as image information. The combined convex lens 21, the prism 22, the grating 23, the prism 24, and the combined convex lens 25 form an imaging optical system for using the incident light for imaging.

[0017] The prism 22 is arranged such that the vertical surface 22b faces the grating 23 side and the inclined surface 22a faces the combined convex lens 21 side. The prism 24 is arranged such that the vertical surface 24b faces the grating 23 side and the inclined surface 24a faces the combined convex lens 25 side. The prisms 22 and 24 are prisms for angle correction. The grating 23 is a grating for wavelength dispersion.

[0018] The sensor 26 is a two-dimensional optical sensor (image sensor). For example, a sensor using an imaging device such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) in a monochrome camera can be applied. The sensor here can use a sensor that can cover visible light to near-infrared light. For example, it is a sensor that can sense the wavelength range of light from 450 nm to 1700 nm. Also, a sensor that senses other ranges may be used. The sensor 26 is installed inclined in a direction away from the entrance 10 with respect to a plane perpendicular to the optical axis direction (Z direction). Details of the sensor 26 will be described later.

[0019] The glass plate 28 is installed between the entrance 10 and the combined convex lens 21. The glass plate 28 uses the same material and the same thickness as the cover glass of the sensor 26. Further, the glass plate 28 is installed inclined in a direction away from the entrance 10 with respect to a plane perpendicular to the optical axis direction (Z direction), with the upper and lower side surfaces on the back side of FIGS. 1 and 2 when viewed from above. Details of the glass plate 28 will be described later.

[0020] The light beam from the entrance 10 passes through the glass plate 28. Thereafter, it is dispersed through the combined convex lens 21, the prism 22, the grating 23, the prism 24, and finally through the combined convex lens 25, and is designed such that the light is horizontally focused on the sensor 26. The sensor 26 is provided with a cover glass, which will be described later, and light forms an image on the imaging device through this cover glass.

[0021] In addition, the spectroscopic imaging unit 20 is optically designed to disperse the light to be acquired within a specific wavelength range. For example, in the case of a spectroscopic imaging unit in the visible region and the near-infrared region, the wavelength range of 450 nm to 1700 nm is designed to span from one end to the other end of the two-dimensional sensor's vertical axis. Therefore, the light of each wavelength is focused on the sensor position corresponding to each wavelength position. Furthermore, by designing the selection of the grating 23, the shape of the prism 24, and the shapes of the combined convex lenses 21 and 25 in accordance with the spectroscopic design theory, the wavelength band of the light that can be projected onto the sensor 26 can be changed to other than the above.

[0022] <Details of the sensor> FIG. 5 is a cross-sectional view of the sensor in the spectroscopic imaging unit of the present invention. The cross-section here shows the cross-section cut by a cross-section (YZ plane) perpendicular to the horizontal direction (X direction).

[0023] The sensor 26 includes an image sensor 26a, an installation base 26b, a sensor cover 26c, and a mounting portion 26d.

[0024] The image sensor 26a has a large number of light-receiving elements arranged two-dimensionally and has a square or rectangular shape. Each light-receiving element converts the light received by each light-receiving element into an electrical signal. The image sensor 26a is installed flat on the installation base 26b.

[0025] The installation base 26b includes an installation surface 26a1 for arranging the image sensor 26a and a side surface 26a2 surrounding the periphery of the image sensor 26a. Since one end of the side surface 26a2 is open, the light-receiving side of the image sensor 26a on the installation base 26b is configured to be open.

[0026] The sensor cover 26c is installed to cover the opening on the side surface of the opening side of the installation base 26b to protect the image sensor 26a. A transparent glass material can be applied to the sensor cover 26c. As the material of the glass material, it is a glass material suitable as the sensor cover 26c. The sensor cover 26c is basically installed parallel to the light-receiving surface of the image sensor 26a.

[0027] The attachment part 26d is a part that is fixed to the main body of the spectroscopic imaging unit 20 on the side opposite to the imaging element 26a of the installation base 26b. The thickness T of the sensor cover 26c is determined based on strength, cost, physical properties of the glass, etc. Also, the space between the sensor cover 26c and the installation base 26b may be sealed with gas.

[0028] As shown in FIG. 5, the sensor 26 is installed such that the upper side is inclined away from the incident port 10 with respect to the XY plane. The XY plane is a plane perpendicular to the longitudinal direction (optical axis direction) of the spectroscopic imaging unit 20. Here, the inclination angle θ when viewed from the side with respect to the plane perpendicular to the optical axis direction can be determined according to the wavelength range of the received light. For example, if the wavelength range is 450 nm to 1700 nm, it can be 15° or more and 45° or less, further 20° or more and 45° or less, further 25° or more and 40° or less, further 30° or more and 35° or less, etc.

[0029] When the wavelength range of the light is widened, if the sensor 26 does not have the above inclination, the image will not be clearly formed and blurring will occur at points with different wavelengths. Therefore, by setting the above inclination and tilting the imaging element 26a, blurring does not occur in the imaging of light at short wavelengths and long wavelengths, and the images can be aligned.

[0030] On the other hand, the wider the wavelength range of the light, the larger the angle θ in FIG. 5 needs to be. However, in this case, the sensor cover 26c also tilts at the same time, and the influence of this tilt also increases. The transparent sensor cover 26c, when light passes through it, due to the angle, the lengths of the vertical axis (Tangential (T)) and horizontal axis (Horizontal (H)) of the light become different. This difference becomes larger as the angle increases. Furthermore, there is also the influence of the thickness T of the sensor cover 26c. The thicker the thickness, the larger the difference in the lengths of the above-mentioned vertical axis (longitudinal wave) and horizontal axis (transverse wave) of the light. As a result, the imaging characteristics deteriorate and there is a possibility that a clear image cannot be formed.

[0031] As a countermeasure in this case, it is also conceivable to reduce the thickness of the sensor cover 26c. However, in this case, the sensor cover 26c needs to be made of an expensive material and the configuration of the sensor 26 needs to be changed from the manufacturing stage, resulting in a large cost.

[0032] FIG. 6 is a plan view when the sensor in the spectroscopic imaging unit of the present invention is placed on a horizontal plane. When the sensor 26 is installed as shown in FIG. 6, the horizontal direction (direction A in FIG. 6) of the imaging element 26a becomes the spatial axis, and the vertical direction (direction B in FIG. 6) of the imaging element 26a becomes the wavelength axis. That is, each piece of information of the light from the incident port 10 extending in the horizontal direction is imaged on the horizontal spatial axis. Further, the light from the incident port 10 is imaged with information for each wavelength in the vertical direction. When the spectroscopic imaging unit 20 of FIGS. 1 to 4 is used, the characteristics in the case where the wavelength becomes longer as going upward in the vertical direction are shown.

[0033] In the case of the example of FIG. 1, the objective lens 13 receives light and makes the light received along the horizontal direction enter the slit 14 (incident port 10). That is, along the horizontal direction (X direction), light is made to enter corresponding to the position of the received light. Thereby, in the imaging element 26a, the horizontal direction becomes the spatial axis corresponding to the horizontal position where the objective lens 13 received light.

[0034] In the case of the example of FIG. 2, since the other ends of the plurality of optical fibers 15 receive light at different locations, the light incident on the optical fibers 15 at each position is output side by side in the horizontal direction. For this reason, in the imaging element 26a, the horizontal direction becomes the spatial axis corresponding to the position of the light received by the optical fiber 15.

[0035] <Details of the glass plate> FIG. 7 is a top view of the glass plate in the spectroscopic imaging unit of the present invention.

[0036] The glass plate 28 is installed for the purpose of offsetting the adverse effect of imaging due to the mounting angle of the above-described sensor cover 26c. It is a glass plate having the same thickness as the thickness T of the sensor cover 26c, and a glass plate having the same optical properties is applied. The angle is inclined by an angle θ as viewed from above with respect to the XZ plane perpendicular to the longitudinal direction (Z direction). This θ is the same angle as the θ shown in FIG. 5. By this glass plate 28, the lengths of the vertical axis (longitudinal wave) and the horizontal axis (transverse wave) are deliberately shifted. That is, the optical path lengths of the longitudinal wave and the transverse wave are made equal. As a result, when passing through the glass of the sensor cover 26c, the shift in the lengths of the vertical axis and the horizontal axis of the light is offset, and the aberration characteristics are improved.

[0037] The inclination angle θ of the glass plate 28 may be inclined toward the sensor 26 side on either end in the X direction with respect to the XY plane which is a vertical plane. At this time, the rotation axis is the axis in the vertical direction (Y direction). Then, as shown by the solid line and the two-dot chain line in FIG. 7, it becomes possible to apply either of the glass plates 28 and 28'.

[0038] The same material can be applied to the sensor cover 26c and the glass plate 28, and here, it suffices that they are glass materials having the same optical properties. In particular, they are materials having the same or substantially the same refractive index nD and Abbe number Vd. The Abbe number is a number representing the degree of difference in refractive index for each wavelength. For example, if BK7 (borosilicate crown optical glass) is used, both the sensor cover 26c and the glass plate 28 use BK7.

[0039] FIG. 8 is a diagram showing the relationship between the angles of the sensor cover and the glass plate in the spectroscopic imaging unit of the present invention. As shown in FIG. 8, with respect to the sensor cover 26c, it is rotated 90° about the optical axis (axis in the Z direction) P. The rotation direction may be either the counterclockwise direction R1 or the clockwise direction R2. When the sensor cover 26c is rotated 90° in the counterclockwise direction R1, the inclined state becomes the glass plate 28 shown by the solid line in FIG. 7. When the sensor cover 26c is rotated 90° in the clockwise direction R2, the inclined state becomes the glass plate 28' shown by the two-dot chain line in FIG. 7. Note that the optical axis is the axis in the traveling direction of light.

[0040] <An example of the measurement system> FIG. 9 is a schematic diagram showing an example of a measurement system to which the spectroscopic imaging unit of the present invention is applied.

[0041] As shown in FIG. 9, the spectroscopic imaging unit 20 and the processing device 30 are connected via a connection line 31. Here, the connection line 31 is a cable for transferring data from the spectroscopic imaging unit 20 to the processing device 30. Then, the image information received by the sensor 26 from the image processing unit 27 of the spectroscopic imaging unit 20 is sent to the processing device 30. Note that a wireless communication method can also be applied instead of the connection line 31.

[0042] The processing device 30 is a device that can analyze based on the information acquired by the sensor 26 of the spectroscopic imaging unit 20. For example, a computer capable of performing data processing such as a personal computer can be applied, and a program is introduced into this computer to perform the corresponding processing. Here, the processing unit is composed of a macroprocessor such as a CPU (Central Processing Unit) and a memory.

[0043] The processing device 30 may be provided with a display unit 30a, and the measurement results and the like are displayed here. As the display unit 30a, for example, a display using liquid crystal, organic EL, or the like can be applied. Also, the display unit 30a may be separate. Further, the processing device 30 may be internally provided with a storage unit, and the image data and analysis results from the image processing unit 27 are stored here. As the storage unit, for example, various types of storage devices such as an HDD (Hard Disk Drive) and an SSD (Solid State Drive) are applied as required.

[0044] Also, the processing device 30 can also be applied to a tablet, a smartphone, etc. As shown in FIG. 9, it is also possible to use a tablet 35 or a smartphone 36 that can transfer data wirelessly with the spectroscopic imaging unit 20 as the processing device 30.

[0045] <Function> In the spectroscopic imaging unit 20 described with reference to FIGS. 1 to 8, the light output from the entrance 10 passes through the entire glass plate 28. Then, the light that has passed through the glass plate 28 forms an image on the sensor 26 through the imaging optical system of the combined convex lens 21, prism 22, grating 23, prism 24, and combined convex lens 25. At this time, in the sensor 26, the light first passes through the sensor cover 26c, and then the imaging element 26a receives the light and forms an image. The imaging here has the spatial axis in the horizontal direction and the wavelength axis in the vertical direction. The light received by the imaging element 26a is converted into an electrical signal and sent to the processing device 30 described with reference to FIG. 9. In the processing device 30, analysis processing is performed based on the received electrical signal, and the analysis result is displayed on the display unit 30a or the like.

[0046] <Influence of second-order light and third-order light> FIG. 10 is a diagram for explaining the influence of second-order light and third-order light on the sensor. In the spectroscopic imaging unit, N-th order diffracted light (N is an integer) may overlap and interfere with the measurement.

[0047] In the spectroscopic imaging unit 20 shown in FIGS. 1 to 3, when an optical system is designed to cover a wide wavelength range, + second-order light, + third-order light, etc. are simultaneously projected onto the sensor. This influence is small, for example, if the sensitivity region of the sensor is not a wide one such as the near-infrared region (900 - 1700 nm). However, for example, when capturing the visible to near-infrared region (450 - 1700 nm) with the sensor, second-order light and third-order light are projected onto the sensor. An example of this is shown in FIG. 10. FIG. 10 is a diagram showing the projection of light with wavelengths of 450 - 1700 nm when no filter is used.

[0048] FIG. 10(a) shows the projection of + first-order light onto the sensor 26. Since the first-order light is the light used for actual measurement, it is designed to be projected onto the imaging element 26a of the sensor 26. FIG. 10(b) shows the projection of + second-order light onto the sensor 26. The + second-order light is projected above the sensor compared to the + first-order light. FIG. 10(c) shows the projection of + third-order light onto the sensor 26. The + third-order light is projected above the sensor compared to the + second-order light. Therefore, the influence of the second-order light is greater than that of the third-order light.

[0049] In this way, when second-order light and third-order light are incident on the sensor, they become an existence that inhibits accurate measurement as false data. Therefore, there is a need to provide a cut filter that cuts off higher-order light other than the first-order light such as second-order light. However, such a cut filter actually affects the first-order light as well, and in many cases, it also cuts off the first-order light to some extent. For this reason, for example, when a cut filter is placed in front of the objective lens 13, the entrance port 10, and the combined convex lens 21 and the entire light passes through the cut filter, the first-order light in the visible range itself is also cut off to some extent. To remove this influence, it is necessary to measure once without the cut filter, measure a second time with the cut filter inserted, and then perform combination in data processing. However, such a method requires two measurements, which is time-consuming. Furthermore, a processing system for this purpose is also required.

[0050] <First Example Using a Cut Filter> FIG. 11 is a cross-sectional view near the sensor showing a first example using the cut filter of the spectroscopic imaging unit of the present invention. FIG. 12 is a front view near the sensor showing a first example using the filter of the spectroscopic imaging unit of the present invention. Here, an example of adding a cut filter 40 to the spectroscopic imaging unit 20 of FIGS. 1 to 8 is shown, and the same explanations are omitted for parts that are not particularly described. Basically, the same components are labeled with the same reference numerals.

[0051] The sensor 26' in FIGS. 11 and 12 has an installation base 26b that becomes the installation base 26b' and no sensor cover 26c compared to the sensor 26 in FIG. 5. The installation base 26b' here has a configuration in which the side surface 26a2 is eliminated compared to the installation base 26b in FIG. 5. Therefore, the installation base 26b' includes only the installation surface 26a1 on which the imaging element 26a is arranged. The inclination angle θ of the sensor 26' in FIGS. 11 and 12 is the same as that of the sensor 26 in FIG. 5.

[0052] The cut filter 40 is a filter that cuts light other than the primary light. It is a filter that cuts at least the secondary light, and may also cut higher-order lights such as the tertiary light and the quaternary light. Therefore, the cut filter 40 is a filter having optical characteristics for this purpose.

[0053] The cut filter 40 is disposed on the light incident side with respect to the imaging element 26a. Specifically, there are two elements. First, the lower end of the cut filter 40 is disposed at a distance S above the lower end of the light receiving surface of the imaging element 26a. Thereby, the imaging element 26a on the side that receives light with a shorter wavelength does not pass through the cut filter 40. Second, the cut filter 40 is disposed at a distance G from the imaging element 26a. At this time, the light receiving surface of the imaging element 26a and the cut filter 40 are disposed in parallel, and the distance between the light receiving surface of the imaging element 26a and the side surface of the cut filter 40 on the side of the imaging element 26a is G.

[0054] The distance S will be described. The distance S is for enabling the imaging element 26a to receive light without passing through the cut filter 40 below the imaging element 26a. As also shown in FIG. 10, the light after the secondary light does not reach below the imaging element 26a. Therefore, it is not necessary to provide the cut filter 40 to the lower side. On the other hand, if the cut filter 40 is provided to the lower side, as described above, the accurate measurement of the primary light is affected more or less by the cut filter 40. Therefore, the configuration is such that the distance S is provided. The distance S may be selected within a range where there is no or little influence on the measurement of the secondary light or higher-order lights after the secondary light. In this range of the distance S, the imaging element 26a receives light that does not pass through the cut filter 40.

[0055] The distance G will be described. As described above, the cut filter 40 is configured to be shifted upward by the distance S. Then, the imaging element 26a receives, on the upper side, the light that has passed through the cut filter 40, and on the lower side, the light that has not passed through the cut filter 40. In this case, a boundary occurs between the light that has passed through the cut filter 40 and the light that has not. If the distance between the cut filter 40 and the imaging element 26a is short, the boundary line becomes a dead space and has an adverse effect on the imaging result. On the other hand, if the distance between the cut filter 40 and the imaging element 26a is large, a blurred portion that does not reach imaging occurs in the portion of the cut filter 40. Therefore, in such a case, the adverse effect on imaging is suppressed and accurate measurement becomes possible.

[0056] Regarding the distance G, a length in the range of 3% or more and 10% or less, and further 2% or more and 8% or less, with respect to the length L from the entrance 10 to the center of the imaging element 26a of the sensor 26 shown in FIG. 3 is preferable. For example, if the length L is about 10 cm, the distance G is in the range of 3 mm or more and 10 mm or less, and further 2 mm or more and 8 mm or less.

[0057] As described above, in the first example using the filter, by installing the cut filter 40 at the distances S and G with respect to the imaging element 26a, good measurement with reduced influence of secondary light and higher-order light becomes possible.

[0058] <Second Example Using a Filter> FIG. 13 is a cross-sectional view near the sensor showing a second example using the filter of the spectroscopic imaging unit of the present invention. FIG. 14 is a front view near the sensor showing a second example using the filter of the spectroscopic imaging unit of the present invention. Here, an example in which a cut filter 40 is added to the spectroscopic imaging unit 20 of FIGS. 1 to 8 is shown, and the same explanations are omitted for portions not particularly described. Basically, the same components are denoted by the same reference numerals.

[0059] The sensors 26'' in FIGS. 13 and 14 have basically the same configuration as the sensor 26 in FIG. 5, and include an imaging device 26a, an installation base 26b, a sensor cover 26c, and a mounting portion 26d. Further, the installation base 26b includes an installation surface 26a1 for disposing the imaging device 26a and a side surface 26a2 surrounding the periphery of the imaging device 26a. However, in order to secure the distance G described in FIGS. 11 and 12, a configuration is adopted in which the distance G is secured between the light receiving surface of the imaging device 26a and the side surface on the light incident side of the sensor cover 26c. For this reason, the thickness of the sensor cover 26c and the height of the side surface 26a2 are dimensioned to maintain this distance G. The inclination angle θ of the sensors 26'' in FIGS. 13 and 14 is the same as that of the sensor 26 in FIG. 5.

[0060] The cut filter 40 is installed by being bonded to the surface on the light incident side of the sensor cover 26c. The cut filter 40 is attached so as to secure the distance S described in the first example of FIGS. 11 and 12. Also, as described above, the distance G is also secured by the configuration of the sensor 26''.

[0061] In the second example using the filter in this way, the cut filter 40 can be installed as it is without changing the configuration of the sensor 26'', and the same effect as the first example using the filter is exhibited.

[0062] <Third Example Using a Filter> FIG. 15 is a cross-sectional view near the sensor showing a third example using the filter of the spectroscopic imaging unit of the present invention. FIG. 16 is a front view near the sensor showing a third example using the filter of the spectroscopic imaging unit of the present invention. Here, an example of adding a cut filter 40 to the spectroscopic imaging unit 20 in FIGS. 1 to 8 is shown, and the same description is omitted for parts not specifically described. Basically the same components are denoted by the same reference numerals.

[0063] The sensors 26''' in FIGS. 15 and 16 include an imaging element 26a, a mounting base 26b, a sensor cover 26c', and a mounting portion 26d. The imaging element 26a and the mounting portion 26d are the same as those in FIG. 5. The mounting base 26b includes a mounting surface 26a1 for arranging the imaging element 26a and a side surface 26a2 surrounding the periphery of the imaging element 26a, similar to FIG. 5. Also, the sensor cover 26c' in FIGS. 15 and 16 is different from the sensor cover 26c in FIG. 5 in that it has a thin portion 26c2.

[0064] The thin portion 26c2 is configured such that a predetermined thickness is removed from the light incident side surface to make the thickness thinner than the base portion 26c1 of the sensor cover 26c'. This forms a stepped portion. The size of the thin portion 26c2 is adapted to the size of the cut filter 40. Also, the dimension of the difference in thickness between the base portion 26c1 and the thin portion c2 (the thickness of the removed part) is the same as the thickness dimension of the cut filter 40. To ensure the distance G described in FIGS. 11 and 12, a configuration is provided such that the distance G is ensured by the light receiving surface of the imaging element 26a and the light incident side surface of the thin portion 26c2 of the sensor cover 26c'. Therefore, the thickness of the thin portion 26c2 of the sensor cover 26c' and the height of the side surface 26a2 are of a dimension configuration to maintain this distance G.

[0065] The cut filter 40 is attached and installed on the light incident side surface of the thin portion 26c2 of the sensor cover 26c'. As a result, the cut filter 40 has a size that fits exactly into the stepped portion in the thin portion 26c2 of the sensor cover 26c'. In this way, no stepped portion exists between the sensor cover 26c' and the cut filter 40. Thus, the cut filter 40 can be attached so as to ensure the distance S described in the first example of FIGS. 11 and 12. Also, as described above, the distance G is ensured by the configuration of the sensor 26'''.

[0066] In the third example using the filter in this way, it is possible to have a configuration without protrusions by the cut filter 40, and at the same time, it exhibits the same effects as the first example using the filter.

[0067] FIG. 17 shows a graph comparing the influence of secondary light with and without the cut filter in the spectroscopic imaging unit of the present invention. This graph is an example applying the configurations of FIGS. 13 and 14. In FIG. 17, the horizontal axis represents wavelength and the vertical axis represents the intensity of light. The case without the cut filter 40 is indicated by A, and the case with the cut filter 40 is indicated by B. In the case of A, strong output is shown in the vicinity of 800 nm to 1500 nm. On the other hand, in the case of B, there is almost no output in the vicinity of 800 nm to 1500 nm, indicating that the secondary light is cut off.

[0068] <Effect> In the spectroscopic imaging unit 20 described with reference to FIGS. 1 to 9, by installing the sensor 26 at a predetermined angle, even for a wide range of light wavelengths, there is no blur in the light imaging, and it becomes possible to align the image. Further, in order to suppress the deterioration of the imaging characteristics due to the sensor cover 26c of the obliquely installed sensor 26, by installing the glass plate 28, the aberration characteristics can be improved. Therefore, more accurate measurement can be performed even in a wide range of light wavelength bands.

[0069] Furthermore, by using the cut filter 40 described with reference to FIGS. 11 to 17, the influence of higher-order light other than primary light such as secondary light can be suppressed. At this time, by determining the position of the cut filter 40 at a predetermined position with respect to the imaging element 26a, the adverse effect of the cut filter 40 on imaging can be suppressed, enabling accurate measurement.

[0070] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments and includes various modifications other than those described above. For example, it is not limited to those having all the configurations provided in the above-described embodiments. Also, it is possible to delete a part of the configuration of a certain embodiment or replace it with another configuration.

Explanation of Reference Numerals

[0071] 10 Entrance 13 Objective lens 14 Slit 15 Fiber 15a One end 20 Spectral imaging unit 21, 25 Combination convex lens 22, 24 Prism 23 Grating 26, 26’, 26’’, 26’’’ Sensor 26a Image sensor 26a1 Installation surface 26a2 Side surface 26b, 26b’ Mounting base 26c, 26c’ Sensor cover 26c1 Base part 26c2 Thin part 27 Image processing unit 28, 28’ Glass plate 30 Processing device 30a Display part

Claims

1. It has a light incident port, a plate glass, an imaging optical system, and a sensor, The sensor includes an imaging element and a sensor cover provided on the light incident side of the imaging element, The sensor is provided with a predetermined angle of inclination with respect to a plane perpendicular to the light traveling direction, The plate glass is made of the same material with the same optical properties and the same thickness as the sensor cover, The plate glass is provided in an inclined state rotated 90° about the light traveling direction as the central axis with respect to the sensor cover, The light from the incident port is imaged on the imaging element through the plate glass, the imaging optical system, and the sensor cover. A spectroscopic imaging unit characterized by that.

2. In the spectroscopic imaging unit according to Claim 1, The material having the same optical properties is a material having the same or substantially the same refractive index and Abbe number. A spectroscopic imaging unit characterized by that.

3. In the spectroscopic imaging unit according to Claim 1 or Claim 2, The inclination angle of the sensor is set in the range of 15° or more and 45° or less. A spectroscopic imaging unit characterized by that.

4. In the spectroscopic imaging unit according to any one of Claims 1 to 3, It includes a cut filter, and the cut filter is arranged offset with respect to the imaging element so that some light reaches the imaging element without passing through the cut filter, and the cut filter is arranged at a position separated from the imaging element by a predetermined distance, The predetermined distance is in the range of 3% or more and 10% or less with respect to the length from the incident port to the center of the imaging element. A spectroscopic imaging unit characterized by that.

5. In the spectroscopic imaging unit according to Claim 4, The predetermined distance is in the range of 2% or more and 8% or less with respect to the length from the incident port to the center of the imaging element. A spectroscopic imaging unit characterized by that.

6. In the spectroscopic imaging unit according to Claim 4 or Claim 5, The cut filter is installed by being bonded to the sensor cover. A spectroscopic imaging unit characterized by that.

7. In the spectroscopic imaging unit according to any one of Claims 1 to 6, It includes a slit through which light is incident via an objective lens, and the incident port is the slit. A spectroscopic imaging unit characterized by that.

8. In the spectroscopic imaging unit according to any one of claims 1 to 6, the spectroscopic imaging unit is connected to one end side of a plurality of optical fibers that propagate light, and the entrance port is one end of the plurality of optical fibers. A spectroscopic imaging unit characterized by this.

9. In the spectroscopic imaging unit according to any one of claims 1 to 8, the imaging optical system includes a first combined convex lens, a first prism, a grating, a second prism, and a second combined convex lens. A spectroscopic imaging unit characterized by this.

Images