JP2023139605A - Spectroscopic imaging unit - Google Patents

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

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.

A spectral imaging unit is a device that can analyze the characteristics of physical properties by receiving light from a plurality of measurement locations and forming an image on a sensor along a spatial axis and a wavelength axis.

For example, in Patent Document 1, the other tip of the input fiber and the output fiber is configured to be applied perpendicularly to the surface of the object to be measured, and the other tip position of the plurality of output fibers is The spectroscopic imaging unit images the light obtained from the plurality of emission fibers on the optical sensor, and the processing device focuses the light obtained from the plurality of emission fibers on the optical sensor. A characteristic measurement system is disclosed that calculates transmission characteristics based on imaging results.

On the other hand, recently, sensors that can handle a wide range of wavelengths have been developed, such as 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 visible light wavelength band. There is.

JP 2018-84539 Publication

However, when using a sensor capable of covering visible light to near-infrared light, there are cases in which an image cannot be formed clearly even if the sensor is installed using a conventional spectral imaging unit method. This is because the wavelength range of light is wide ranging from 450 to 1700 nm. In this case, a phenomenon occurs in which images of short wavelength and long wavelength cannot be precisely aligned.

At this time, a method of tilting the sensor may be considered, but if the tilt angle becomes large, the imaging characteristics will deteriorate due to the influence of the cover glass that protects the sensor. Furthermore, if the wavelength range is wide, the influence of secondary light may occur, which may adversely affect the measurement results.

SUMMARY OF THE INVENTION 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.

In order to achieve the above object, one of the typical spectral imaging units of the present invention has an entrance for light to enter, a plate glass, an imaging optical system, and a sensor, and the sensor includes an imaging device. and a sensor cover provided on the light incident side of the image sensor, the sensor being inclined at a predetermined angle with respect to a plane perpendicular to the traveling direction of the light, and the plate glass being provided on the sensor cover. The plate glass is made of the same material and has the same thickness and has the same optical characteristics as the sensor cover, and the plate glass is tilted by 90 degrees with respect to the sensor cover about the direction in which the light travels as a central axis, and the light from the input aperture is , the image is formed on the image sensor via the plate glass, the imaging optical system, and the sensor cover.

According to the present invention, in the spectroscopic imaging unit, it is possible to more accurately measure even in a wide range of light wavelength bands.
Problems, configurations, and effects other than those described above will be clarified by the following embodiments.

FIG. 1 is a transparent perspective view showing a first application example of the spectral imaging unit of the present invention. FIG. 7 is a transparent perspective view showing a second application example of the spectral imaging unit of the present invention. FIG. 1 is a perspective side view showing an embodiment of a spectroscopic imaging unit of the present invention. FIG. 1 is a perspective top view showing an embodiment of a spectroscopic imaging unit of the present invention. FIG. 3 is a cross-sectional view of a sensor in the spectroscopic imaging unit of the present invention. FIG. 3 is a plan view of the spectral imaging unit of the present invention when the sensor is placed on a horizontal surface. It is a top view of the glass plate in the spectroscopic imaging unit of this invention. It is a figure showing the relationship of the angle of a sensor cover and a glass plate in a spectroscopic imaging unit of the present invention. 1 is a schematic diagram showing an example of a measurement system to which a spectroscopic imaging unit of the present invention is applied. FIG. 3 is a diagram for explaining the influence of secondary light and tertiary light on a sensor. FIG. 2 is a cross-sectional view of the vicinity of a sensor showing a first example using a filter of the spectroscopic imaging unit of the present invention. FIG. 2 is a front view of the vicinity of a sensor showing a first example using a filter of a spectroscopic imaging unit of the present invention. FIG. 7 is a cross-sectional view of the vicinity of a sensor showing a second example using a filter of the spectroscopic imaging unit of the present invention. FIG. 7 is a front view of the vicinity of a sensor showing a second example using a filter of the spectroscopic imaging unit of the present invention. FIG. 7 is a cross-sectional view of the vicinity of a sensor showing a third example using a filter of the spectroscopic imaging unit of the present invention. FIG. 7 is a front view of the vicinity of a sensor showing a third example using a filter of the spectroscopic imaging unit of the present invention. FIG. 3 shows a graph comparing the spectroscopic imaging unit of the present invention with and without a filter. FIG.

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

<Configuration of spectroscopic imaging unit>
FIG. 1 is a transparent perspective view showing a first application example of the spectral imaging unit of the present invention. FIG. 2 is a transparent perspective view showing a second application example of the spectral 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 horizontal direction in FIGS. 1 to 4 is the longitudinal direction (Z direction) of the spectroscopic imaging unit 20, the vertical direction in FIGS. 1 to 3 is the vertical direction (Y direction) of the spectroscopic imaging unit 20, and the vertical direction in FIG. This is the horizontal 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 direction in which light travels (optical axis direction).

FIG. 1 shows an example in which the spectroscopic imaging unit 20 includes a slit 14. At this time, the setting is such that the light passing through the objective lens 13 enters a slit 14 provided on the side surface of the spectroscopic imaging unit 20 in the Z direction. The slit 14 is provided to extend in the X direction (horizontal direction) with the X direction (horizontal direction) of the spectroscopic imaging unit 20 as the longitudinal direction, and is narrower in the Y direction (vertical direction). At this time, the slit 14 is set to extend horizontally at the vertical center of the two-dimensional sensor 26. Thereby, in FIG. 1, the slit 14 extending in the horizontal direction becomes the entrance port 10. The objective lens 13 can be configured, for example, by being held in a lens barrel provided on an integrating sphere. Further, the spectral imaging unit 20 and the objective lens 13 may be moved relative to the object to be measured in the Y direction (vertical direction).

FIG. 2 shows an example in which one end 15a of the plurality of fibers 15 is connected to a spectroscopic imaging unit 20. At this time, the tips of the one ends 15a of the plurality of fibers 15 are set to be lined up in the horizontal direction at the vertical center of the two-dimensional sensor 26. As a result, in FIG. 2, one end 15a of the plurality of fibers 15 arranged in the horizontal direction becomes the entrance port 10. The number of the plurality of fibers 15 is, for example, four or more, further, eight or more. Further, the other ends of the plurality of fibers 15 are installed at desired positions and receive light there.

As shown in FIGS. 1 to 4, the spectral imaging unit 20 includes an entrance opening 10 at the entrance 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, and a prism 24. , a combined convex lens 25, and a sensor 26 in this order in the longitudinal direction. The spectral imaging unit 20 also includes an image processing section 27, which performs processing such as converting information received by the sensor 26 into image information. Note that the combined convex lens 21, the prism 22, the grating 23, the prism 24, and the combined convex lens 25 constitute an imaging optical system that uses incident light for imaging.

The prism 22 is arranged with the vertical surface 22b facing the grating 23 side and the slope 22a facing the combined convex lens 21 side. The prism 24 is arranged with the vertical surface 24b facing the grating 23 side and the slope 24a facing the combined convex lens 25 side. The prisms 22 and 24 are angle correction prisms. The grating 23 is a grating for wavelength dispersion.

The sensor 26 is a two-dimensional optical sensor (image sensor). For example, a sensor using a monochrome camera having an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) can be applied. As the sensor here, a sensor capable of covering visible light to near-infrared light can be used. For example, it is a sensor that can detect light wavelengths in the range of 450 nm to 1700 nm. Further, a sensor that senses a range other than this may also be used. The sensor 26 is installed with its upper side inclined in a direction away from the entrance port 10 with respect to a plane perpendicular to the optical axis direction (Z direction). Details of the sensor 26 will be described later.

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

The light beam from the entrance aperture 10 passes through the glass plate 28. After that, the light is dispersed through a combination convex lens 21, a prism 22, a grating 23, and a prism 24, and finally passes through a combination convex lens 25 and is designed to be focused horizontally on a sensor 26. The sensor 26 is provided with a cover glass, which will be described later, and light is focused on the image element through this cover glass.

Further, the spectral imaging unit 20 is optically designed so that the light to be acquired is dispersed in a specific wavelength range. For example, in the case of a spectral imaging unit in the visible region and near-infrared region, the wavelength range from 450 nm to 1700 nm is designed to extend from one end of the vertical axis of the two-dimensional sensor to the other. For this reason, the light of each wavelength is condensed at a sensor position that matches the respective 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 spectrometer design theory, the wavelength band of light that can be projected onto the sensor 26 can be changed beyond the above. can.

<Sensor details>
FIG. 5 is a cross-sectional view of the sensor in the spectroscopic imaging unit of the present invention. The cross section here shows a cross section cut along a cross section (YZ plane) perpendicular to the lateral direction (X direction).

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

The image sensor 26a has a large number of light receiving elements arranged two-dimensionally, and has a positive or rectangular shape. Each light receiving element converts the received light into an electrical signal. The image sensor 26a is installed on a flat surface on the installation stand 26b.

The installation stand 26b includes an installation surface 26a1 on which the image sensor 26a is placed, and a side surface 26a2 surrounding 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 open.

The sensor cover 26c is installed on the opening-side side surface of the installation base 26b so as to cover the opening and protect the image sensor 26a. The sensor cover 26c can be made of transparent glass material. The glass material is a glass material suitable for the sensor cover 26c. The sensor cover 26c is basically installed parallel to the light receiving surface of the image sensor 26a.

The attachment portion 26d is a portion that is fixed to the main body of the spectroscopic imaging unit 20 on the opposite side of the installation base 26b from the image sensor 26a. The thickness T of the sensor cover 26c is determined based on strength, cost, physical properties of glass, etc. Further, gas may be sealed between the sensor cover 26c and the installation base 26b.

As shown in FIG. 5, the sensor 26 is installed with its upper side inclined in a direction away from the entrance 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 a plane perpendicular to the optical axis direction can be determined depending on the wavelength range of the received light. For example, if the wavelength range is 450 nm to 1700 nm, the range is 15° or more and 45° or less, furthermore, 20° or more and 45° or less, furthermore, 25° or more and 40° or less, furthermore, 30° or more and 35° or less. It is possible to do so.

When the wavelength range of light is widened, if the sensor 26 does not have the above-mentioned inclination, the image will not be formed clearly, and blurring will occur at points with different wavelengths. Therefore, by setting the above-mentioned inclination and inclining the image sensor 26a, the images of the short and long wavelengths do not become blurred, and the images can be brought together.

On the other hand, the wider the wavelength range of 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 is angled when light passes through it, so that the lengths of the vertical axis (tangential (T)) and horizontal axis (horizontal (H)) of the light differ. The difference becomes larger as the angle increases. Furthermore, there is also the influence of the thickness T of the sensor cover 26c, and the thicker the thickness, the greater the difference in length between the vertical axis (longitudinal wave) and the horizontal axis (transverse wave) of the light described above. As a result, the imaging characteristics deteriorate and there is a possibility that clear imaging cannot be performed.

As a countermeasure for this case, it may be possible to reduce the thickness of the sensor cover 26c. However, in this case, it is necessary to use an expensive material for the sensor cover 26c and change the configuration of the sensor 26 from the manufacturing stage, resulting in large costs.

FIG. 6 is a plan view of the spectral imaging unit of the present invention when the sensor is placed on a horizontal surface. When the sensor 26 is installed as shown in FIG. 6, the horizontal direction of the image sensor 26a (direction A in FIG. 6) becomes the spatial axis, and the vertical direction of the image sensor 26a (direction B in FIG. 6) becomes the wavelength axis. becomes. That is, each piece of information of the light from the entrance port 10 extending in the lateral direction is imaged on the lateral spatial axis. Furthermore, information for each wavelength is formed into an image of the light from the entrance port 10 in the vertical direction. When the spectroscopic imaging unit 20 of FIGS. 1 to 4 is used, characteristics are shown in which the wavelength becomes longer as it goes up in the vertical direction.

In the example of FIG. 1, the objective lens 13 receives light and makes the received light enter the slit 14 (incidence port 10) along the lateral direction. That is, light is incident along the lateral direction (X direction) corresponding to the position of the received light. Thereby, in the image sensor 26a, the lateral direction becomes a spatial axis corresponding to the lateral position where the objective lens 13 receives light.

In the case of the example shown in FIG. 2, the other ends of the plurality of fibers 15 receive light at different locations, so that the light incident on the fibers 15 at each location is output side by side in the horizontal direction. Therefore, in the image sensor 26a, the horizontal direction becomes a spatial axis corresponding to the position of the light received by the fiber 15.

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

The glass plate 28 is installed for the purpose of offsetting the adverse effect on imaging caused by the above-mentioned mounting angle of the sensor cover 26c. The glass plate has the same thickness as the thickness T of the sensor cover 26c and is made of a material with the same optical characteristics. The angle is inclined by an angle θ when viewed from above with respect to the XZ plane perpendicular to the longitudinal direction (Z direction). This θ is the same angle as θ shown in FIG. By using this glass plate 28, the lengths of the vertical axis (longitudinal wave) and the horizontal axis (transverse wave) are intentionally shifted. That is, the optical path lengths of longitudinal waves and transverse waves are matched. Thereby, when the light passes through the glass of the sensor cover 26c, the difference in length between the vertical axis and the horizontal axis of the light is canceled out, and the aberration characteristics are improved.

The inclination angle θ of the glass plate 28 may be such that any end of the glass plate 28 in the X direction is inclined toward the sensor 26 with respect to the XY plane, which is a vertical plane. At this time, the rotation axis becomes an 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 the glass plate 28 or 28'.

The sensor cover 26c and the glass plate 28 can be made of the same material, as long as they have the same optical characteristics. In particular, the materials are the same or substantially the same in refractive index nD and Abbe number Vd. The Abbe number is a number that represents 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 are made of BK7.

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

<Example of 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.

As shown in FIG. 9, the spectroscopic imaging unit 20 and the processing device 30 are connected via a connection line 31. The connection line 31 here is a cable for transferring data from the spectroscopic imaging unit 20 to the processing device 30. Image information received by the sensor 26 is then sent from the image processing section 27 of the spectroscopic imaging unit 20 to the processing device 30. Note that a wireless communication system may be used instead of the connection line 31.

The processing device 30 is a device that can perform analysis based on information acquired by the sensor 26 of the spectroscopic imaging unit 20. For example, a computer capable of processing data, such as a personal computer, can be used, and a program can be introduced into this computer to perform the processing. Here, the processing unit includes a macro processor such as a CPU (Central Processing Unit), a memory, and the like.

The processing device 30 may include a display section 30a, on which measurement results and the like are displayed. For example, a liquid crystal display, an organic EL display, or the like can be used as the display section 30a. Further, the display section 30a may be a separate body. Further, the processing device 30 may include a storage section therein, in which image data and analysis results from the image processing section 27 are stored. As the storage unit, various types of storage devices are applied as needed, such as an HDD (hard disk drive) or an SSD (solid state drive).

Further, the processing device 30 can 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, which can wirelessly transfer data to the spectroscopic imaging unit 20, as the processing device 30.

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

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

In the spectral imaging unit 20 shown in FIGS. 1 to 3, when an optical system is designed to have a wide wavelength range, +2nd order light, +3rd order light, etc. are simultaneously projected onto the sensor. This effect was small unless the sensitivity range of the sensor was wide, such as the near-infrared range (900 to 1700 nm). However, for example, when a sensor captures the visible to near-infrared region (450 to 1700 nm), secondary light and tertiary light are projected onto the sensor. An example is shown in FIG. FIG. 10 is a diagram showing the projection of light having a wavelength of 450 to 1700 nm when no filter is used.

FIG. 10(a) shows the projection of +1st-order light onto the sensor 26. Since the primary light is the light used for actual measurement, it is designed to be projected onto the image sensor 26a of the sensor 26. FIG. 10(b) shows the projection of +secondary light onto the sensor 26. The +2nd order light is projected higher on the sensor than the +1st order light. FIG. 10(c) shows the projection of +3rd order light onto the sensor 26. The +3rd order light is projected higher on the sensor than the +2nd order light. Therefore, the influence of secondary light is greater than that of tertiary light.

In this way, when the secondary light and the tertiary light are incident on the sensor, they become false data and obstruct accurate measurement. Therefore, it becomes necessary to provide a cut filter that cuts high-order light other than first-order light such as secondary light. However, strictly speaking, such a cut filter also affects the primary light, and there are many cases in which the primary light is also cut to some extent. For this reason, for example, if a cut filter is inserted before the objective lens 13, the entrance aperture 10, and the combined convex lens 21 and all of the light passes through the cut filter, some primary light in the visible range itself will also be cut. To remove this influence, it is necessary to measure without a cut filter the first time, insert a cut filter the second time, and then perform a 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.

<First example using a cut filter>
FIG. 11 is a cross-sectional view of the vicinity of a sensor showing a first example using a cut filter of the spectral imaging unit of the present invention. FIG. 12 is a front view of the vicinity of the sensor showing a first example using the filter of the spectroscopic imaging unit of the present invention. Here, an example is shown in which a cut filter 40 is added to the spectral imaging unit 20 of FIGS. 1 to 8, and the same explanation is omitted for parts that are not particularly explained. Basically the same components are given the same reference numerals.

The sensor 26' in FIGS. 11 and 12 differs from the sensor 26 in FIG. 5 in that the installation base 26b is the installation base 26b', and there is no sensor cover 26c. The installation stand 26b' here has a configuration in which the side surface 26a2 is removed from the installation stand 26b of FIG. 5. Therefore, the installation stand 26b' includes only an installation surface 26a1 on which the image sensor 26a is placed. The inclination angle θ of the sensor 26' in FIGS. 11 and 12 is the same as that of the sensor 26 in FIG.

The cut filter 40 is a filter that cuts light other than primary light. It is a filter that cuts at least secondary light, and may also cut high-order light such as 3rd-order light and 4th-order light. Therefore, the cut filter 40 is a filter that has optical characteristics for this purpose.

The cut filter 40 is placed closer to the light incident side than the image sensor 26a. Specifically, there are two elements. First, the lower end of the cut filter 40 is placed above the lower end of the light receiving surface of the image sensor 26a by a distance S. As a result, the image sensor 26a on the side that receives light with a shorter wavelength does not pass through the cut filter 40. In the second method, the cut filter 40 is arranged with a distance G apart from the image sensor 26a. At this time, the light receiving surface of the image sensor 26a and the cut filter 40 are arranged in parallel, and the distance between the light receiving surface of the image sensor 26a and the side surface of the cut filter 40 on the image sensor 26a side is G.

The distance S will be explained. The distance S allows light to be received below the image sensor 26a without passing through the cut filter 40. As shown in FIG. 10, the secondary light and subsequent lights do not reach the lower side of the image sensor 26a. Therefore, it is not necessary to provide the cut filter 40 all the way to the bottom. On the other hand, if the cut filter 40 is provided all the way to the lower side, as described above, the cut filter 40 will affect accurate measurement of the primary light to some extent. For this reason, the configuration is such that a distance S is provided. The distance S may be selected within a range that has no or little influence on the measurement of secondary light or higher-order light after the secondary light. As a result, within the range of distance S, the image sensor 26a receives light that does not pass through the cut filter 40.

The distance G will be explained. As described above, the cut filter 40 is configured to be shifted upward by the distance S. Then, the image sensor 26a receives the light that has passed through the cut filter 40 on the upper side, and receives the light that does not pass through the cut filter 40 on the lower side. In this case, there is a boundary between light that passes through the cut filter 40 and light that does not pass through. If the distance between the cut filter 40 and the image sensor 26a is short, the boundary line becomes a dead space, which adversely affects the imaging results. On the other hand, if the cut filter 40 and the image sensor 26a are far apart, the cut filter 40 becomes a blurred portion that does not reach image formation. Therefore, in such a case, accurate measurement is possible while suppressing the adverse effects of imaging.

The distance G is within the range of 3% to 10%, more preferably 2% to 8%, of the length L from the entrance port 10 to the center of the image sensor 26a of the sensor 26, as shown in FIG. length is preferred. For example, if the length L is about 10 cm, the distance G will be in the range of 3 mm or more and 10 mm or less, and further, 2 mm or more and 8 mm or less.

In this way, in the first example using a filter, the influence of secondary light and higher order light is suppressed by installing the cut filter 40 at the above-mentioned distance S and distance G with respect to the image sensor 26a. Good measurements are possible.

<Second example using a filter>
FIG. 13 is a sectional view of the vicinity of the sensor showing a second example using the filter of the spectroscopic imaging unit of the present invention. FIG. 14 is a front view of the vicinity of the sensor showing a second example using the filter of the spectral imaging unit of the present invention. Here, an example is shown in which a cut filter 40 is added to the spectral imaging unit 20 of FIGS. 1 to 8, and the same explanation is omitted for parts that are not particularly explained. Basically the same components are given the same reference numerals.

The sensor 26'' in FIGS. 13 and 14 basically has the same configuration as the sensor 26 in FIG. 5, and includes an image sensor 26a, a mounting base 26b, a sensor cover 26c, and a mounting portion 26d. Furthermore, the installation stand 26b includes an installation surface 26a1 on which the image sensor 26a is placed, and a side surface 26a2 surrounding the image sensor 26a. However, in order to secure the distance G explained in FIGS. 11 and 12, the distance G is secured between the light receiving surface of the image sensor 26a and the side surface of the sensor cover 26c on the light incident side. Therefore, the thickness of the sensor cover 26c and the height of the side surface 26a2 are designed to maintain this distance G. The inclination angle θ of the sensor 26'' in FIGS. 13 and 14 is the same as that of the sensor 26 in FIG.

The cut filter 40 is attached and installed on the light incident side surface of the sensor cover 26c. The cut filter 40 is pasted to ensure the distance S described in the first example of FIGS. 11 and 12. Furthermore, as described above, the distance G is also ensured by the configuration of the sensor 26''.

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

<Third example using a filter>
FIG. 15 is a sectional view of the vicinity of the sensor showing a third example using the filter of the spectroscopic imaging unit of the present invention. FIG. 16 is a front view of the vicinity of the sensor showing a third example using the filter of the spectroscopic imaging unit of the present invention. Here, an example is shown in which a cut filter 40 is added to the spectral imaging unit 20 of FIGS. 1 to 8, and the same explanation is omitted for parts that are not particularly explained. Basically the same components are given the same reference numerals.

The sensor 26''' in FIGS. 15 and 16 includes an image sensor 26a, a mounting base 26b, a sensor cover 26c', and a mounting portion 26d. The image sensor 26a and the mounting portion 26d are the same as those shown in FIG. 5. As in FIG. 5, the installation stand 26b includes an installation surface 26a1 on which the image sensor 26a is placed, and a side surface 26a2 surrounding the image sensor 26a. Further, the sensor cover 26c' in FIGS. 15 and 16 differs from FIGS. 5, 13, and 14 in that it includes a thinner portion 26c2 than the sensor cover 26c in FIG.

The thin portion 26c2 has a structure in which a predetermined thickness is removed from the light incident side surface to make the plate thinner than the base portion 26c1 of the sensor cover 26c'. This forms a stepped portion. The size of the thin portion 26c2 matches the size of the cut filter 40. Further, the difference in thickness between the base portion 26c1 and the thin portion c2 (thickness of the removed portion) is the same as the thickness of the cut filter 40. In order to secure the distance G described in FIGS. 11 and 12, the distance G is secured by the light receiving surface of the image sensor 26a and the light incident side 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 designed to maintain this distance G.

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 perfectly fits into the stepped portion of the thin portion 26c2 of the sensor cover 26c'. This makes it possible to eliminate the presence of a stepped portion between the sensor cover 26c' and the cut filter 40. In this way, the cut filter 40 can be attached so as to secure the distance S described in the first example of FIGS. 11 and 12. Furthermore, as described above, the distance G is also ensured by the configuration of the sensor 26'''.

In the third example using a filter in this way, it is possible to have a configuration in which there is no protrusion due to the cut filter 40, and the same effect as the first example using a filter is also exhibited.

FIG. 17 shows a graph comparing the influence of secondary light when the spectral imaging unit of the present invention has a cut filter and when it does not have a cut filter. This graph is an example to which the configurations of FIGS. 13 and 14 are applied. In FIG. 17, the horizontal axis is the wavelength, and the vertical axis is the intensity of light. The case where the cut filter 40 is not provided is indicated by A, and the case where the cut filter 40 is present is indicated by B. In the case of A, 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, and it can be seen that secondary light is cut off.

<Effect>
In the spectral imaging unit 20 described in FIGS. 1 to 9, by installing the sensor 26 at a predetermined angle, the images are aligned without blurring even for a wide range of light wavelengths. becomes possible. Further, in order to suppress deterioration of imaging characteristics due to the sensor cover 26c of the sensor 26 installed obliquely, a glass plate 28 is installed, thereby making it possible to improve aberration characteristics. Therefore, more accurate measurements can be made even in a wide range of light wavelength bands.

Furthermore, by using the cut filter 40 described with reference to FIGS. 11 to 17, it is possible to suppress the influence of higher-order light other than primary light such as secondary light. At this time, by determining the position of the cut filter 40 at a predetermined position with respect to the image sensor 26a, the adverse effect of the cut filter 40 on imaging can be suppressed, and accurate measurement is possible.

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

10 Inlet port 13 Objective lens 14 Slit 15 Fiber 15a One end 20 Spectroscopic imaging units 21, 25 Combined convex lenses 22, 24 Prism 23 Grating 26, 26', 26'', 26''' Sensor 26a Image sensor 26a1 Installation surface 26a2 Side surface 26b , 26b' Installation stand 26c, 26c' Sensor cover 26c1 Base part 26c2 Thin part 27 Image processing part 28, 28' Glass plate 30 Processing device 30a Display part

Claims (9)

It has an entrance through which light enters, a plate glass, an imaging optical system, and a sensor,
The sensor includes an image sensor and a sensor cover provided on a light incident side of the image sensor,
The sensor is provided to be inclined at a predetermined angle with respect to a plane perpendicular to the traveling direction of the light,
The plate glass is made of a material having the same optical properties and the same thickness as the sensor cover,
The plate glass is provided in an inclined state rotated by 90 degrees with respect to the sensor cover about the direction in which light travels as a central axis,
A spectral imaging unit characterized in that light from the entrance port is imaged on the image pickup element via the plate glass, the imaging optical system, and the sensor cover. The spectroscopic imaging unit according to claim 1,
The spectroscopic imaging unit is characterized in that the materials having the same optical properties are materials having the same or substantially the same refractive index and Abbe number. The spectroscopic imaging unit according to claim 1 or 2,
A spectroscopic imaging unit characterized in that the inclination angle of the sensor is set in a range of 15° or more and 45° or less. The spectroscopic imaging unit according to any one of claims 1 to 3,
A cut filter is provided, and the cut filter is arranged to be shifted from the image sensor so that a part of the light reaches the image sensor without passing through the cut filter, and the cut filter placed at a predetermined distance from the element,
The spectroscopic imaging unit is characterized in that the predetermined distance is in a range of 3% or more and 10% or less of a length from the entrance port to the center of the image sensor. The spectroscopic imaging unit according to claim 4,
The spectroscopic imaging unit is characterized in that the predetermined distance is in a range of 2% or more and 8% or less of a length from the entrance port to the center of the image sensor. In the spectroscopic imaging unit according to claim 4 or 5,
The spectral imaging unit is characterized in that the cut filter is attached and installed on the sensor cover. The spectroscopic imaging unit according to any one of claims 1 to 6,
A spectral imaging unit comprising a slit through which light enters through an objective lens, the entrance opening being the slit. The spectroscopic imaging unit according to any one of claims 1 to 6,
The spectroscopic imaging unit is characterized in that the spectroscopic imaging unit is connected to one end side of a plurality of fibers that propagate light, and the entrance port is one end of the plurality of fibers. The spectroscopic imaging unit according to any one of claims 1 to 8,
A spectral imaging unit characterized in that the imaging optical system includes a first combined convex lens, a first prism, a grating, a second prism, and a second combined convex lens.

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