JP5793219B1 - Imaging apparatus and imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hyperspectral imaging apparatus capable of acquiring a clear hyperspectral image without requiring complicated arithmetic processing, control and adjustment of mechanism and apparatus. The apparatus includes a lens on which light from a subject is incident, an optical filter unit that splits light from the subject into light having a plurality of wavelengths by changing the wavelength of light to be transmitted with time. An image sensor having a light receiving surface disposed at a focal position of light from the lens, and having a plurality of pixels that receive the light dispersed by the optical filter unit and convert the light into an electric signal, and an electric signal generated by the image sensor For each pixel of the image sensor, data of physical quantities based on the light intensity or light intensity associated with the pixel position information, wavelength information, and time information is generated, and these data are used as pixel position information and wavelength information. And an arithmetic processing unit for converting the data into physical quantity data based on the intensity of light or the intensity of light. [Selection] Figure 1

Description

  The present invention relates to an imaging apparatus and an imaging method for acquiring hyperspectral data of a subject.

  An imaging device (hereinafter, also referred to as “hyperspectral imaging device”) that acquires hyperspectral data (hereinafter, also referred to as “HSD”) uses light from a subject (light emitted from the subject itself or light reflected from the subject). By separating the light into a plurality of wavelengths and receiving the separated light by an imaging device having a plurality of pixels and converting the light into an electrical signal, pixel position information and It is a device that acquires hyperspectral data, which is data of physical quantity (for example, reflectance) based on light intensity or light intensity associated with wavelength information. Hyperspectral imaging devices are mounted on satellites and aircraft and are used in the agricultural and environmental fields. In the future, it is expected to be used in the medical field and food field. According to the hyperspectral imaging apparatus, since the conventional color concept can be extended to the spectral region, a phenomenon that is invisible to the human eye can be visualized.

  FIG. 7 is an example of hyperspectral data acquired by the hyperspectral imaging apparatus. The hyperspectral data includes the physical quantity I (x, y, λ based on the intensity of light of the wavelength λ or the intensity of light at the position (x, y) of each pixel, where x and y are positions on the image plane and λ is a wavelength. ).

  As a prior art of such a hyperspectral imaging apparatus, a technique has been proposed in which light from a subject that is sequentially taken in by movement of a slit is dispersed for each wavelength and received by an imaging device to receive an image of the subject. As such an apparatus, for example, a technique described in Patent Document 1 (Japanese Patent Laid-Open No. 2009-039280) has been proposed. This technique is generally called a stage scanning method. In this technique, a subject image is scanned by moving the entire optical stage on which an image sensor such as a slit having a fine width, a diffraction grating, and a CCD is moved up and down. The light that has passed through the slit is split into light having a plurality of wavelengths by the diffraction grating, and the split light is imaged on the imaging surface of the imaging device. The imaged light is converted into an electrical signal and input to the analysis unit. In this technique, light passing through a one-dimensional (x) slit becomes two-dimensional spectral spectrum data I (x, λ), and finally three-dimensional hyperspectral data is obtained by continuous scanning in the y direction. It is converted to I (x, y, λ).

  However, in the technique using the stage scanning method described in Patent Document 1, since the entire optical stage is mechanically moved, the image is easily blurred due to the influence of vibration due to the movement of the apparatus, and a clear image is obtained. Hard to get. Further, since a mechanism for mechanically moving the entire optical stage is required, it is difficult to reduce the size of the apparatus.

  In order to solve this problem, for example, a hyperspectral imaging apparatus described in Patent Document 2 (Japanese Patent Laid-Open No. 2011-89895) has been proposed. This apparatus acquires hyperspectral data using a variable slit that can move only the slit position without moving the entire optical stage up and down.

  However, in the apparatus described in Patent Document 2, since the image is scanned by moving the slit up and down, the imaging position of the spectral spectrum on the image sensor also changes as the slit moves. For this reason, it is necessary to prepare a large number of wavelength tables indicating the correspondence between the y coordinate of the image sensor and the wavelength projected on the image sensor in advance for each slit position, and the slit is moved in the y direction. Each time, the y coordinate must be converted to a wavelength using these wavelength tables. Therefore, this apparatus requires complicated data processing and takes time for data processing. In addition, the liquid crystal slit has a limit in contrast between the slit portion and a portion other than the slit, and the accuracy of acquired data decreases due to light leakage (stray light) from a portion other than the slit.

  As a technique based on the same concept as an apparatus that acquires hyperspectral data using a variable slit, a hyperspectral imaging apparatus that generates line-shaped light using a light selection member is proposed in Patent Document 3. In this apparatus, the control of the plurality of light selection members is complicated, and each of the plurality of light selection members having different manufacturing accuracy requires a precise position (calibration) separately. Complex adjustments and controls are required.

JP 2009-039280 A JP 2011-089895 A JP 2012-058037 A

Fujiura et al., “Development of optical devices using high-efficiency electro-optic crystal KTN”, NTT Technical Journal, NTT Photonics Laboratories, January 2004, P56-59

  In view of the above problems, the present invention is capable of obtaining a clear hyperspectral image without requiring complicated arithmetic processing, control and adjustment of a mechanism and an apparatus, and easy-to-miniaturize hyperspectral imaging. An object is to provide an apparatus and a hyperspectral imaging method.

  The above problem is solved by adopting a time scanning method in which light from the entire subject is sequentially scanned over time to obtain spectral spectrum information.

  In a first aspect of the present invention, there is provided a hyperspectral imaging device that images a subject by splitting light from the subject into light having a plurality of wavelengths and causing the image sensor to receive the split light. The hyperspectral imaging device includes a lens on which light from a subject is incident, and an optical filter unit that splits light from the subject into light of a plurality of wavelengths by changing the wavelength of light to be transmitted over time. An image sensor having a light receiving surface disposed at a focal position of light from the lens, and having a plurality of pixels that receive the light dispersed by the optical filter unit and convert the light into an electric signal, and an electric signal generated by the image sensor For each pixel of the imaging device, light intensity data associated with the pixel position information, wavelength information, and time information or physical quantity data based on the light intensity is generated, and these data are used as pixel position information and An arithmetic processing unit that converts light intensity data associated with the wavelength information or physical quantity data based on the light intensity.

  In one embodiment, the optical filter unit includes a linear variable bandpass filter configured to continuously change the wavelength of transmitted light in one direction and a linear variable bandpass filter in one direction over time. , And a mechanical drive unit that moves perpendicularly to the normal direction of the light receiving surface. The drive unit is more preferably a linear motor.

  In another embodiment, the optical filter unit includes a linear variable bandpass filter configured such that the wavelength of transmitted light continuously changes in one direction, and a light traveling direction with respect to the linear variable bandpass filter. A refractive index variable material disposed upstream and capable of arbitrarily changing the angle of the traveling direction of outgoing light with respect to the traveling direction of incident light by changing the refractive index, and the refractive index of the refractive index variable material And an electric drive unit for applying a voltage for changing the refractive index to the refractive index variable material. The refractive index variable material is more preferably a KTN crystal, and the electrical drive unit more preferably has a power supply and a drive circuit for applying a voltage for controlling the refractive index of the KTN crystal to the KTN crystal.

  In the second aspect of the present invention, there is provided an imaging method for imaging a subject by splitting light from the subject into a plurality of wavelengths and causing the imaging device to receive the split light. The method includes focusing light from a subject on a light receiving surface of an imaging device having a plurality of pixels that convert the received light into an electrical signal, and light from the subject with a plurality of wavelengths over time. For each pixel of the image sensor, from the step of splitting the light into light, the step of receiving the dispersed light by the image sensor and converting it to an electrical signal for each pixel, and the electrical signal generated by the step of converting to the electrical signal Generating light intensity data associated with pixel position information, wavelength information and time information, or physical quantity data based on light intensity, and using these data for light associated with pixel position information and wavelength information. Converting to intensity data or physical quantity data based on light intensity.

  In one embodiment, the spectroscopic step is performed by applying a linear variable bandpass filter configured so that the wavelength of transmitted light continuously changes in one direction to the light receiving surface along one direction over time. And moving the light from the subject through the linear variable bandpass filter.

  In another embodiment, the spectroscopic step is performed on the refractive index variable material capable of arbitrarily changing the angle of the traveling direction of the outgoing light with respect to the traveling direction of the incident light by changing the refractive index. The step of applying a voltage for changing the refractive index as time passes, the step of transmitting the light from the subject through the refractive index variable material, and the wavelength range of the light that transmits the light transmitted through the refractive index variable material are the same. And passing through a linear variable bandpass filter configured to continuously change in direction.

  According to the present invention, it is possible to realize a hyperspectral imaging apparatus capable of obtaining a clear image because the apparatus is easily adjusted, controlled, and downsized and the apparatus is not affected by vibration or light leakage.

1 is a diagram illustrating a schematic configuration of a hyperspectral imaging device according to a first embodiment using a linear variable bandpass filter. FIG. It is a block diagram which shows the arithmetic processing part and memory | storage part in the hyperspectral imaging device which concerns on one Embodiment of this invention. It is a figure which shows typically how the wavelength of the light received by the light-receiving surface of an image pick-up element changes with progress in the hyperspectral imaging device by 1st Embodiment. It is a figure which shows the image of the image data acquired in the hyperspectral imaging device by 1st Embodiment. It is a figure which shows schematic structure of the hyperspectral imaging device by 2nd Embodiment using the refractive index variable material which can change the refractive index of light arbitrarily. It is a figure which shows the image of the image data acquired in the hyperspectral imaging device by 2nd Embodiment. It is a figure which shows an example of hyperspectral data.

  Hereinafter, a first embodiment embodying a hyperspectral imaging apparatus and a hyperspectral imaging method according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
[Outline of device]
FIG. 1 is a diagram showing a schematic configuration of a hyperspectral imaging apparatus 1 according to the first embodiment of the present invention. FIG. 2 is a block diagram illustrating the arithmetic processing unit 20 and the storage unit 22 of the hyperspectral imaging apparatus 1.
As shown in FIG. 1, the hyperspectral imaging device 1 changes the wavelength of light transmitted from a lens 12 through which light emitted from or reflected from the subject 10 enters and the wavelength of transmitted light over time, thereby allowing light from the subject 10. Is provided with an optical filter unit 13 that can split the light into a plurality of wavelengths of light, and an image sensor 18 having a light receiving surface 17 that receives the light split by passing through the optical filter unit 13. The image sensor 18 converts the received light into an electrical signal and outputs it. The hyperspectral imaging apparatus 1 further includes an arithmetic processing unit 20 that takes in the converted electrical signal and generates hyperspectral data, a storage unit 22 for storing various data, programs, and the like, and a display as necessary. The display part 24 is provided.

  The hyperspectral imaging apparatus according to the present invention is, for example, a food field (for example, visualization of freshness of vegetables, meat, fish, etc.), a medical field (for example, visualization of malignant tumors), a remote sensing field (for example, vegetation from above). Observation), industrial field (for example, electronic circuit wiring check), cosmetic field (for example, visualization of facial stains and skin moisture), security field (for example, detection of intruders), agricultural field (for example, harvest time) For example, image display means for displaying a spectrum image as a measurement result, and printing means for printing spectrum data. Etc.) can be configured and used.

[Description of each configuration]
Hereinafter, each configuration shown in FIG. 1 will be described in detail.

  The lens 12 receives light from the subject 10 and directs the light to the optical filter unit 13. The lens 12 is driven in the optical axis direction by a lens driving unit (not shown), and the light from the subject 10 can be focused on the light receiving surface 17 of the image sensor 18.

  The optical filter unit 13 is configured to change the wavelength of light to be transmitted with the passage of time. In the present embodiment, the optical filter unit 13 may include a linear variable bandpass filter 14 and a mechanical drive unit 16 that moves the linear variable bandpass filter 14.

  The linear variable bandpass filter 14 is an optical filter having a size corresponding to or larger than the light receiving surface 17 of the image sensor 18, and the wavelength of light that can be transmitted from one end to the other end. On the other hand, it has spectral characteristics that continuously change in one direction from λ1 to λn (hereinafter, this direction is referred to as “wavelength change direction”). The linear variable bandpass filter shown in the upper part of FIG. 1 represents a state in which the lower linear variable bandpass filter 14 is viewed from the upstream side in the light traveling direction. Accordingly, light having a specific wavelength out of the light incident on the linear variable bandpass filter 14 is positioned from one end of the linear variable bandpass filter 14 to the other end (that is, from one end. Depending on the length of the wavelength change direction, the linear variable bandpass filter 14 is transmitted. In one embodiment of the present invention, a commercially available optical filter such as a linear variable bandpass filter manufactured by Edmund Optics Japan, Inc. can be used as the linear variable bandpass filter 14.

  The linear variable bandpass filter 14 is preferably as close as possible to the light receiving surface 17 so that the wavelength resolution Δλ can be further increased. Further, when the linear variable bandpass filter 14 is formed by coating an optical thin film on a substrate such as glass, the one closer to the light receiving surface 17 so that the wavelength resolution Δλ can be further increased. It is preferable to use a linear variable bandpass filter 14 whose surface is coated with an optical thin film.

  A mechanical drive unit 16 is connected to the linear variable bandpass filter 14. In the present embodiment, as shown in FIG. 1, the linear variable bandpass filter 14 is wavelength-changed perpendicularly to the normal direction of the light receiving surface 17 of the image sensor 18 using the mechanical drive unit 16. By moving along the direction, it passes through the wavelength region corresponding to the length of the linear variable bandpass filter 14 located in front of the light receiving surface 17 (that is, upstream in the traveling direction of light from the subject 10) at a certain point in time. The received light is received by the light receiving surface 17. In FIG. 1, the linear variable bandpass filter 14 is moved perpendicularly to the normal direction of the light receiving surface 17 so that the wavelength change direction is the vertical direction of the light receiving surface 17. The moving direction of the pass filter 14 is not limited to this direction. For example, the linear variable bandpass filter 14 is moved in the normal direction of the light receiving surface 17 so that the wavelength change direction is the left-right direction of the light receiving surface 17. However, it may be moved vertically.

  For example, as shown in FIG. 1, a linear variable bandpass filter 14 formed so that the wavelength of light to be transmitted changes from λ1 to λn in the wavelength change direction (that is, the vertical direction in FIG. 1) is used. By moving the linear variable bandpass filter 14 from the lower side to the upper side of the light receiving surface 17 of the image sensor 18, light of wavelengths λ1 to λn among the light from the subject 10 is linearly sequentially with time. The light passes through the variable bandpass filter 14 and is received by the light receiving surface 17. The mechanical drive unit 16 is controlled by a control signal from the drive unit control unit 203 of the arithmetic processing unit 20, and the moving speed of the linear variable bandpass filter 14 is controlled by this control signal. The relationship between the operation of the linear variable bandpass filter 14 and the wavelength of light received by the light receiving surface 17 will be described later with reference to FIG.

  The mechanical drive unit 16 can use a linear motor or a combination of a rotary motor and a ball screw, but it is more preferable to use a linear motor. Since the linear motor does not have a bearing and the drive system can be made smaller, a device using the linear motor can be made smaller than a device using a rotary motor. In one embodiment of the present invention, a commercially available linear motor such as an ultrasonic motor TULA series manufactured by Techno Hands Co., Ltd. can be used as the linear motor. In another embodiment of the present invention, as a combination of a rotary motor and a ball screw, for example, a linear stage T-LSR series manufactured by Zaber Technologies can be used.

  The image sensor 18 can be configured using, for example, a CCD image sensor or a CMOS image sensor, and converts the light imaged on the light receiving surface 17 of the image sensor 18 into an electrical signal for each pixel. The size of the image sensor 18 can be appropriately selected depending on the application used and the size of the apparatus. The electric signal (digital signal) converted by the image sensor 18 is taken into the arithmetic processing unit 20.

  As illustrated in FIG. 2, the arithmetic processing unit 20 includes a drive unit control unit 203, an image data generation unit 204, a data conversion unit 206, and a CPU 210. The storage unit 22 stores data necessary for processing in the arithmetic processing unit 20, data after processing, working data, various programs, and the like. The image data storage unit 222, the HSD storage unit 224, And a program storage unit 226.

  The drive unit control unit 203 controls the mechanical drive unit 16 so as to move the linear variable bandpass filter 14 perpendicular to the normal direction of the light receiving surface 17, preferably at a constant speed. The image data generation unit 204 acquires the electrical signal converted by the image sensor 18 and also acquires data related to the moving speed of the linear variable bandpass filter 14 from the drive unit control unit 203, and the above-described electric signal and moving speed data. Are used to generate image data representing the intensity of light or a physical quantity (for example, reflectance) I based on the intensity of light for each pixel. The wavelength λ of the light received by the light receiving surface 17 at a certain time t is determined by the length of the linear variable bandpass filter 14 in the wavelength changing direction located before the light receiving surface 17 at the time t. This length can be calculated from the time t and the moving speed v of the linear variable bandpass filter 14. The image data generation unit 204 associates the positional information x, y of each pixel, the wavelength information λ of the light received at each pixel, and the information t of the time when the light is received, and the image data I (t, x, y, λ) is generated.

  The generated image data is stored in the image data storage unit 222. The data conversion unit 206 reads the image data from the image data storage unit 222 and converts it into hyperspectral data (HSD). The converted hyperspectral data is stored in the HSD storage unit 224. The hyperspectral data thus converted is processed as necessary by the external output unit 208 of the arithmetic processing unit 20, and is visually output as an image on an external monitor, or the data or image is printed by a printer device. Can do.

  Hereinafter, the operation of the optical filter unit 13 and the generation of hyperspectral data will be described in detail.

[Operation of optical filter section and generation of HSD]
FIG. 3 schematically shows how the wavelength of light received by the light receiving surface 17 of the image sensor 18 changes with time in the present embodiment using the linear variable bandpass filter 14. Is. As shown in FIG. 1, the linear variable bandpass filter 14 is disposed in front of the light receiving surface 17 of the image sensor 18, and is perpendicular to the normal direction of the light receiving surface 17 by the mechanical drive unit 16. Moving. The moving direction of the linear variable bandpass filter 14 is the wavelength changing direction.

  A time T = t0 is defined when the upper end 14a of the linear variable bandpass filter 14 is coincident with the lower end 17b of the light receiving surface 17 of the image sensor 18. This reference position of the linear variable bandpass filter 14 is accurately located when the device is manufactured. Next, the upper end 14a of the filter 14 moves from the lower end 17b of the light receiving surface 17 toward the upper end 17a at a constant moving speed v between T = t0 and t1, and at time T = t1, FIG. As shown in (a), for example, it is located at a distance L1 from the lower end 17b of the light receiving surface 17. The length of L1 can be calculated using the moving speed v and time t1. At this time, the linear variable bandpass filter 14 covers the area of the light receiving surface 17 obtained from (length L1) × (the lateral length of the light receiving surface). At time T = t1, the linear variable bandpass filter 14 transmits light having a plurality of wavelengths, for example, λ1 to λ2, corresponding to positions within the length L1 in the wavelength change direction. During T = t0 to t1, the linear variable bandpass filter 14 sequentially receives light of a plurality of wavelengths (here, λ1 to λ2) corresponding to positions within the length L1 in the wavelength change direction as time passes. As a result, the light receiving surface 17 sequentially receives the transmitted light of wavelengths λ1 and λ2 over time.

  The linear variable bandpass filter 14 further moves at a constant moving speed v. When time T = tm, the upper end 14a of the filter 14 is, for example, the upper end of the light receiving surface 17, as shown in FIG. A position corresponding to 17a, that is, a distance L2 from the lower end 17b of the light receiving surface 17 is reached. The length of L2 can be calculated using the moving speed v and time tm. At time T = tm, the linear variable bandpass filter 14 transmits light having a plurality of wavelengths, for example, λ1 to λm to λn−r, corresponding to positions within the length L2 in the wavelength change direction. During T = t1 to tm, the linear variable bandpass filter 14 transmits light of a plurality of wavelengths (in this case, λ1 to λm to λn−r) corresponding to positions within the length L2 in the wavelength change direction over time. As a result, the light receiving surface 17 sequentially receives light having the transmitted wavelengths as time passes.

  The linear variable bandpass filter 14 further moves at a constant moving speed v. When time T = tn, the lower end 14b of the filter 14 is, for example, the upper end 17a of the light receiving surface 17 as shown in FIG. To L3. At time T = tn, the linear variable bandpass filter 14 transmits light having a plurality of wavelengths, for example, λn−2 to λn, corresponding to positions within the length L3 in the wavelength changing direction. During T = tm to tn, the linear variable bandpass filter 14 emits light of a plurality of wavelengths (here, λ1 to λn) corresponding to the length in the wavelength changing direction located in front of the light receiving surface 17 during this period. As a result, the light is sequentially transmitted with the passage of time. As a result, the light receiving surface 17 sequentially receives the light in the transmitted wavelength region with the passage of time. When the acquisition of data for all wavelengths is completed, the linear variable bandpass filter 14 is returned to the reference position.

  The light received on the light receiving surface 17 in this manner is converted into an electrical signal by the image sensor 18, and the converted electrical signal is split into a plurality of wavelengths at each received time by the image data generation unit 204. Created image data. The created image data is sequentially stored in the image data storage unit 222. The accuracy (wavelength resolution) Δλ of the wavelength of the acquired light is the sampling time interval ΔT of the image data, the moving speed v of the linear variable bandpass filter 14, and the performance (unit in the wavelength change direction) of the linear variable bandpass filter 14. Transmission wavelength width per length). Therefore, by shortening the sampling time interval ΔT or slowing the moving speed v of the linear variable bandpass filter 14, data can be acquired with a required wavelength resolution Δλ depending on the application. In the present embodiment, the image data acquired here is each pixel (xi, yi) every time ti, where the width direction of the light receiving surface 17 of the image sensor 18 is the x direction and the direction orthogonal to the x direction is the y direction. ) Is the data set I (ti, xi, yi, λi) of the intensity I of the light having the wavelength λi received in (i.e., pixel position information, wavelength information, and time information acquired for each pixel of the image sensor). Data of light intensity associated with or a physical quantity data based on the light intensity.

  FIG. 4 shows an image of this data set. In the figure, each cell represents a pixel of the image sensor, and the height of the oblique line in the pixel represents the intensity of light. Since FIG. 4 is for explaining the image of the data set, the number of pixels of the image pickup element in the drawing is represented significantly smaller than the actual number of image pickup elements. For example, the intensity data of the light (wavelength λ2) received at the pixel (xn, y1) at time T = t1 is I (t1, xn, y1, λ2). For example, the intensity data of the light (wavelength λ1) received at the pixel (x1, yn) at time T = tm is I (tm, x1, yn, λ1), and the pixel (xm, ym) The intensity data of the light received at (wavelength λm) is I (tm, xm, ym, λm). Further, the intensity data of the light (wavelength λn−2) received at the pixel (xm, yn) at time T = tn is I (tn, xm, yn, λn−2).

  Next, the image data is read from the image data storage unit 222 by the data conversion unit 206 and converted into hyperspectral data (HSD). As described above, the image data stored in the image data storage unit 222 is the light intensity data I (ti, xi, yi, λi) at the wavelength λi at each pixel (xi, yi) at each time ti. Yes, the data conversion unit 206 reads out these data and rearranges them as light intensity data at the position (xi, yi) of each pixel for each wavelength λi, so that the hyperspectral data I (xi, yi, λi) is generated. That is, the hyperspectral data is light intensity data associated with pixel position information and wavelength information, or physical quantity data based on the light intensity. The generated hyperspectral data is stored in the HSD storage unit 224.

(Second Embodiment)
Hereinafter, a second embodiment that embodies the hyperspectral imaging apparatus and hyperspectral imaging method according to the present invention will be described in detail with reference to the drawings. FIG. 5 is a diagram illustrating a schematic configuration of a hyperspectral imaging device 1 according to the second embodiment as a diagram corresponding to FIG. 1 illustrating the first embodiment. In the present embodiment, the configuration of the optical filter unit 13 is different from that of the first embodiment. In FIG. 5, the same elements as those shown in FIG. 1 are denoted by the same reference numerals, and overlapping elements will not be described here.

[Configuration of optical filter section]
The hyperspectral imaging device 1 of the present embodiment can arbitrarily change the refractive index of light that is transmitted by applying a voltage in the optical filter unit 13, thereby causing the outgoing light to travel in the traveling direction of the incident light. The refractive index variable material 30 capable of arbitrarily changing the direction angle is used. The refractive index variable material 30 is provided in the optical filter unit 13 in front of the linear variable bandpass filter 14 (that is, upstream in the traveling direction of light from the subject 10). In this embodiment, the linear variable bandpass filter 14 is fixed before the light receiving surface 17 so as to cover the entire light receiving surface 17, and therefore, a mechanical drive for moving the linear variable bandpass filter 14. The part 16 is not necessary. The linear variable bandpass filter 14 is arranged so that the entire wavelength range that needs to be acquired covers the light receiving surface 17.

  The refractive index variable material 30 is connected to an electrical drive unit 32 for changing the refractive index of the refractive index variable material 30, and the operation of the electrical drive unit 32 is performed by the drive unit control unit 203 of the arithmetic processing unit 20. Be controlled. Unlike the first embodiment, by configuring the optical filter unit 13 using such a refractive index variable material 30 and the linear variable bandpass filter 14, a configuration without a mechanical drive unit is possible. The apparatus can be further reduced in size, and the apparatus itself is not affected by vibration, so that the image is less likely to be blurred and a clearer image can be obtained.

As the refractive index variable material 30 in the present embodiment, typically, a KTN crystal (KTa _1-x Nb _x O ₃ ) can be used, but is not limited to this, and the refractive index variable material 30 is For example, other materials having an electro-optic effect such as lithium niobate crystal (LiNbO ₃ ), lithium tantalate crystal (LiTaO ₃ ), potassium niobate (KNbO ₃ ), and the like can also be used. “Electro-optic effect” refers to a phenomenon in which the refractive index of a material changes when a voltage is applied. The effect that the refractive index change is proportional to the applied voltage is the “first-order electro-optic effect” (Pockels effect). The effect in which the refractive index change is proportional to the square of the voltage is called “second-order electro-optic effect” (Kerr effect). For example, the KTN crystal is a transparent electro-optic crystal made of potassium, tantalum, niobium and oxygen, and is known as a material having a very large secondary electro-optic effect. Details of the KTN crystal are described in Non-Patent Document 1, for example.

[Operation of optical filter section and generation of HSD]
Thus, the refractive index variable material 30 can arbitrarily change its refractive index according to the magnitude of the control voltage from the electric drive unit 32. Therefore, the refractive index variable material is supplied from the electric drive unit 32 so that the light whose traveling direction has changed due to refraction when passing through the refractive index variable material 30 sequentially covers the entire wavelength changing direction of the linear variable bandpass filter 14. By changing the magnitude of the control voltage applied to 30 over time, the light from the subject 10 can be split into light of a plurality of wavelengths. The magnitude of the control voltage for allowing the transmitted light to change the refractive index so as to cover the entire wavelength changing direction of the linear variable bandpass filter 14 depends on the type of the refractive index variable material 30. In the manufacture of the device, the relationship between the magnitude of the control voltage and the light refraction angle is adjusted.

  For example, at time T = t1, the refractive index of the refractive index variable material 30 is indicated by a one-dot chain line in FIG. 5A due to the refractive index of the refractive index variable material 30 by the voltage from the electrical drive unit 32. When controlled to travel along the optical path (Pt1), it corresponds to the transmission wavelength of the light at the position of the linear variable bandpass filter 14 on the optical path of the light (ie, below the linear variable bandpass filter 14). Light having a plurality of wavelengths, for example, λ1 to λ2, passes through the linear variable bandpass filter 14 and is received by the light receiving surface 17 of the image sensor 18. The light receiving state on the light receiving surface 17 at this time is, for example, a state shown as T = t1 in FIG. In the present embodiment, the linear variable bandpass filter 14 is disposed upside down with respect to the first embodiment shown in FIG.

  Next, at time T = tm, the refractive index of the refractive index variable material 30 is changed by the voltage from the electric drive unit 32, and the light emitted from the refractive index variable material 30 is indicated by a solid line in FIG. When controlled to travel (Ptm), it corresponds to the transmission wavelength of the light at the position of the linear variable bandpass filter 14 on the optical path of the light (that is, near the center of the linear variable bandpass filter 14). Light having a plurality of wavelengths, for example, λm−1 to λm + 1, passes through the linear variable bandpass filter 14 and is received by the light receiving surface 17. The light receiving state on the light receiving surface 17 at this time is, for example, a state shown as T = tm in FIG. Similarly, at time T = tn, the refractive index of the refractive index variable material 30 is indicated by a dotted line in FIG. 5A due to the refractive index of the refractive index variable material 30 by the voltage from the electrical drive unit 32. When controlled to travel along the optical path (Ptn), the state of the light receiving surface 17 becomes a state shown as T = tn in FIG. 5B.

  The light received on the light receiving surface 17 in this manner is converted into an electrical signal by the image sensor 18, and the converted electrical signal is split into a plurality of wavelengths at each received time by the image data generation unit 204. Created image data. The created image data is sequentially stored in the image data storage unit 222. In the present embodiment, the image data acquired here is the data set I (ti of the intensity I of the light of the wavelength λi received at each pixel (xi, yi) every time ti, as in the first embodiment. , Xi, yi, λi), that is, light intensity data or physical quantity data based on light intensity associated with pixel position information, wavelength information, and time information acquired for each pixel of the image sensor. It is.

  FIG. 6 shows an image of this data set. In the figure, each cell represents a pixel of the image sensor, and the height of the oblique line in the pixel represents the intensity of light. Since FIG. 6 is for explaining the image of the data set, the number of pixels of the image sensor in the figure is represented significantly smaller than the actual number of image sensors. For example, the intensity data of the light (wavelength λ2) received at the pixel (x1, y2) at time T = t1 is I (t1, x1, y2, λ2). For example, the intensity data of the light (wavelength λm) received at the pixel (x2, ym) at time T = tm is I (tm, x2, ym, λm). Further, for example, the intensity data of the light (wavelength λn−1) received at the pixel (x1, yn−1) at time T = tn is I (tn, x1, yn−1, λn−1). Become. The acquired image data is converted into hyperspectral data by the data conversion unit 206 as in the first embodiment.

DESCRIPTION OF SYMBOLS 1 Hyperspectral imaging device 10 Subject 12 Lens 13 Optical filter part 14 Linear variable band pass filter 16 Mechanical drive part 17 Light-receiving surface 18 Image sensor 20 Arithmetic processing part 203 Drive part control part 204 Image data generation part 206 Data conversion part 208 External Output unit 210 CPU
222 Image data storage unit 224 HSD storage unit 226 Program storage unit 22 Storage unit 24 Display unit 30 Refractive index variable material 32 Electrical drive unit

Claims (3)

An imaging apparatus that images the subject by splitting light from the subject into light having a plurality of wavelengths and causing the imaging device to receive the split light,
A lens on which light from the subject is incident;
An optical filter unit that splits light from the subject into light of a plurality of wavelengths by changing the wavelength of light to be transmitted with the passage of time; and
An image sensor having a light receiving surface disposed at a focal position of light from the lens, and having a plurality of pixels that receive light dispersed by the optical filter unit and convert the light into an electrical signal;
From the electrical signal generated by the image sensor, for each pixel of the image sensor, generate physical quantity data based on the light intensity or light intensity associated with the pixel position information, wavelength information and time information, and An arithmetic processing unit that converts the data of the above into the data of the physical quantity based on the light intensity or the light intensity associated with the pixel position information and the wavelength information ,
The optical filter section is
A linear variable bandpass filter configured to continuously change the wavelength of light to be transmitted in one direction;
Arranged upstream of the linear variable bandpass filter in the light traveling direction, by changing the refractive index, the angle of the traveling direction of the emitted light with respect to the traveling direction of the incident light can be arbitrarily changed. A refractive index variable material;
An electric drive unit for applying a voltage to the refractive index variable material to change a refractive index of the refractive index variable material over time;
That having a, an imaging device. 2. The imaging according to claim 1 , wherein the refractive index variable material is a KTN crystal, and the electrical driving unit includes a power source and a driving circuit that apply a voltage for controlling a refractive index of the KTN crystal to the KTN crystal. apparatus. An imaging method for imaging the subject by splitting light from the subject into a plurality of wavelengths and causing the imaging device to receive the split light,
Focusing light from a subject on a light receiving surface of an imaging device having a plurality of pixels that convert the received light into an electrical signal;
Splitting the light from the subject into light of a plurality of wavelengths over time;
Receiving the dispersed light by the image sensor and converting the light into an electrical signal for each pixel;
From the electrical signal generated by the step of converting to an electrical signal, for each pixel of the image sensor, data of physical quantity based on the light intensity or light intensity associated with the pixel position information, wavelength information and time information is obtained. produced, see containing and converting these data into data of a physical quantity based on the intensity or the intensity of light of the light associated with the positional information and the wavelength information of the pixel,
The spectroscopic step includes:
A voltage for changing the refractive index over time is applied to the refractive index variable material that can arbitrarily change the angle of the outgoing light traveling direction with respect to the traveling direction of incident light by changing the refractive index. Adding steps,
Transmitting light from the subject through the refractive index variable material;
Transmitting the light transmitted through the refractive index variable material through a linear variable bandpass filter configured to continuously change the wavelength region of the transmitted light in one direction; and
Including, imaging methods.