JP2835100B2 - Spectral imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectral imaging device capable of extracting light of a specific wavelength or imaging in color.

[Conventional technology]

When a color image is to be obtained, a camera having three imaging devices is usually used. That is, three image pickup tubes are prepared corresponding to the three primary colors R (red), G (green), and B (blue), and RGB filters are mounted on the front surfaces thereof.
Then, the optical image distributed by a prism or the like is incident on each image pickup tube, and the R, G, and B output signals are combined to mix the image of each wavelength, thereby obtaining a color image.

[Problems to be solved by the invention]

However, according to the above prior art, the optical image is represented by R,
An optical system such as a prism for separating each of G and B, an RGB filter for selectively passing a specific wavelength, and the like are required, and an image pickup tube is also required for each of R, G and B. For this reason, not only was the apparatus complicated and large, but also the cost was high.

An object of the present invention is to solve the above-mentioned drawbacks.

[Means for solving the problem]

A first spectral imaging apparatus according to the present invention has an external electron emission type photocathode, a photoelectric conversion unit into which an optical image to be imaged is incident on the photocathode, and a photoelectron emitted from the photocathode. Means for extracting an object having an initial speed in a predetermined range and generating an optical image of a specific wavelength corresponding to the range of the initial speed.

Further, the second spectral imaging apparatus according to the present invention includes an external electron emission type photoelectric surface that receives an optical image to be imaged on one surface and emits photoelectrons from the other surface, and the other surface of the photoelectric surface. A predetermined level of extraction voltage is applied between an imaging surface on which a photoelectron image is formed by being arranged opposite to the side and disposed between the imaging surface and the photoelectric surface; An image tube having an electron transmission type electrode; extraction voltage switching means for switching an extraction voltage between a plurality of levels; controlling the switching operation of the extraction voltage switching means; and forming an image plane for each level of the extraction voltage. Image capturing control means for capturing the image and outputting image data, and generating means for generating an optical image of a specific wavelength corresponding to the level of the extraction voltage based on the image data.

Further, the third spectral imaging apparatus according to the present invention includes an image tube similar to the above, and an R tube capable of extracting R, G, and B components of the three primary colors.
Extraction voltage switching means for switching the extraction voltage between the GB level, the GB level at which the G and B components can be extracted, and the B level at which the B component can be extracted, and controlling the switching operation of the extraction voltage switching means, Imaging control means for capturing an image on the image plane for each level of the extraction voltage and outputting imaging data; and subtracting the imaging data when the extraction voltage is at the GB level from the imaging data when the extraction voltage is at the RGB level to obtain the R component data. Calculating means for obtaining the G component data by subtracting the imaging data at the B level from the imaging data at the GB level; and the imaging data of the B component output from the imaging control means when the extracted voltage is at the B level And a generating means for generating the color image corresponding to the optical image by combining the R component data and the G component data obtained by the calculating means.

[Action]

According to the invention, photoelectrons emitted from the photocathode are extracted according to their initial velocity. Here, the initial speed of the photoelectrons is a value corresponding to the energy of the incident light, that is, the wavelength. Therefore, by extracting the photoelectrons according to the initial speed, it is possible to selectively capture only the incident light image of the specific wavelength.

The above-mentioned extraction of photoelectrons can be realized by disposing an electron transmission type electrode facing the photocathode and applying a predetermined level of extraction voltage between the electrode and the photocathode. Then, by switching the level of the extraction voltage, it becomes possible to switch the wavelength of the optical image to be captured.

〔Example〕

Prior to the description of specific embodiments, the principle of the present invention will be described.

The energy of light varies depending on the wavelength λ. If the Planck constant is h and the light speed is c, E = hc / λ (1). Therefore, the energy E _lambda of photoelectrons emitted from the photocathode having a specific work function phi, the _{E λ = hc / λ-φ} ... (2). Here, the energy E _lambda corresponds to the initial velocity at which the photoelectrons emitted from the photocathode, thus optoelectronic initial velocity has a value corresponding to the wavelength of the incident light. Therefore, if photoelectrons that form an image on the imaging surface are extracted within a predetermined initial velocity range,
Only an incident optical image in a predetermined wavelength range can be captured.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a configuration diagram of a color imaging device according to an embodiment. Light from the object A ₁ to be imaged is incident on the image tube 3 consisting proximity II through the objective lens 1 and the UV radiation filter 2 (image intensifier).
The image tube 3 receives an optical image and emits external photoelectrons. The photoelectric surface 31 is formed on the incident surface, an electron-transmitting grid electrode 32 provided in close proximity to the photoelectric surface 31, and transmits through the grid electrode 32. (Micro channel plate) 33 for multiplying the obtained photoelectrons, a fluorescent screen 34 for receiving the multiplied electrons from the MCP 33 and generating a fluorescent image, and a vacuum container 35 for holding the above-mentioned elements integrally in a vacuum. And

The fluorescent screen 34 displays the fluorescent image through the relay lens 4.
CCD incorporated in the imaging device 5 and the like (charge coupled device), a video signal corresponding to the image A ₂ corresponding to the object A _1, frame signal for vertical synchronization is outputted from the imaging device 5. The video signal is sent to the signal switch 61,
From here, it is sent to the RGB memory 71, GB memory 72 and B memory 73 as frame memories. R operation circuit 81 is RGB
Based on the signals (video signals) from the memory 71 and the GB memory 72, subtraction of (RGB-GB) is performed to obtain an R component signal, and the G operation circuit 82 is based on the signals from the GB memory 72 and the B memory 73. , (GB-B) to obtain a G component signal. The RGB synthesizing circuit 9 receives the R, G, B signals from the R operation circuit 81, the G operation circuit 82, and the B memory 73.
An image based on the component signals is synthesized, and a color signal is output.

On the other hand, the frame signal from the imaging device 5 is sent to the control circuit 10, and the switching operation of the video signal changeover switch 61, the RGB memory 71, the GB
The timing of the storage operation of the memory 72 and the B memory 73, the operation of the R operation circuit 81 and the G operation circuit 82, and the timing of the mixing operation of the RGB synthesis circuit 9 are controlled. The control signal from the control circuit 10 is also supplied to an extraction voltage, that is, a cathode voltage changeover switch 62.
Is switched between the B level voltage V _B , the GB level voltage V _GB, and the RGB level voltage V _RGB . Incidentally, the grid electrode 32 of the image tube 3 is grounded, the potential of the photocathode _{31 (V B, V GB,} V RGB) is set to several 100 mV. The potential V _M-IN between the grid electrode 32 and the input surface of the _MCP 33 is, for example, about 200 V, the potential V _MCP between the input and output surfaces of the _MCP 33 is, for example, 500 to 900 V, the output surface of the _MCP 33 and the fluorescent screen 34. the potential V _S between is set to, for example, about 6kV.

Next, the operation of the color imaging apparatus according to the above embodiment will be described with reference to FIG. 2 and FIG.

First, the cathode voltage changeover switch 62 is switched by the control signal from the control circuit 10, and the photoelectric surface 31 of the image tube 3 is switched.
Is controlled so that the voltage of FIG. Then
When the B level voltage V _B is selected, the photoelectrons emitted by the photons of the R and B components have a small initial velocity,
The light cannot pass through the grid electrode 32 facing 31. On the other hand, the photoelectrons emitted by the high-energy B-component photons have a high initial velocity, so that they pass through the grid electrode 32 and are multiplied by the MCP 33 to cause the fluorescent screen 34 to generate fluorescent light. On the other hand, when the GB level voltage V _GB is selected, only the photoelectrons due to the low-energy R component photons cannot pass through the grid electrode 32, and therefore, only the fluorescence corresponding to the G and B component photons is emitted. Generated on screen 34.
When the RGB level voltage V _RGB is selected, R,
Photoelectrons generated by photons of either G or B component are
, And only the noise component is blocked, so that the fluorescent screen 34 generates fluorescent light corresponding to all of the R, G, and B components.

Therefore, as shown in FIG. 2B, the spectral characteristics in the first frame in which the photoelectric surface 31 is at the RGB level voltage V _RGB are R, G,
The spectral characteristics in the second frame, which has sensitivity in all wavelength ranges of B and has a GB level voltage V _GB , has sensitivity in the G and B wavelength ranges and has a B level voltage V _B. The spectral characteristics in the third frame have sensitivity in the B wavelength range.
The ultraviolet light having a wavelength shorter than the wavelength range of B is cut by the ultraviolet filter 2 before entering the photoelectric surface 31.

The spectral characteristic video signal obtained as described above is
Under the control of the control circuit 10, the signals are separately stored in the RGB memory 71, the GB memory 72, and the B memory 73 by the signal changeover switch 61. Therefore, these frame memories 71 to
The 73, the optical image data of the object A ₁ in the spectral characteristics shown in FIG. 2 (c) is stored. For these data (shown in FIGS. 2 (c) and 3 (a)), the R operation circuit 81 and the G operation circuit 82 subtract (RGB-GB) and (G
BB) is subtracted. In this case, since the quantum efficiency differs depending on the R, G, and B components, the calculation is performed after weighting. By the above processing, data of the R, G, and B components are respectively extracted as shown in FIGS. 3 (b) and 3 (c). The extracted data is mixed by the RGB synthesizing circuit 9, synthesized as a color signal and output.

The present inventor conducted the following experiment in order to confirm the effectiveness of the above embodiment.

That is, using an image tube having an S-20 photocathode,
A spectroscope is arranged in front of the photocathode to reduce the wavelength of incident light by 20
It was changed from 0 nm to 900 nm. Then, the photocathode potential (V
_K-IN ) was changed in the range of 0.3 V to 0.9 V in 0.1 V steps, and the quantum efficiency was measured. The result is shown in FIG. Note that the wavelength
Incident light below 350nm can be cut by placing an ultraviolet filter.

Next, for this measured value, V _K-IN =
0.9 V, V _K-IN = 0.7 V corresponding to the G component, and V _K-IN = 0.4 V corresponding to the B component, and weighted subtraction is performed.

That is, for the G component, (GB−B) = V _0.7V −3.29 × V _0.4V, and for the R component, (RGB−GB) = V _0.9V −1.56 × V _0.7V . The results are shown in FIG. 5 as curves C _R , C _B and C _G.
When the quantum efficiency is adjusted to 10%, the result is as shown in FIG. 6, and it can be seen that spectral imaging can be performed well.

The present invention is not limited to the above embodiment, and various modifications are possible.

For example, when observing an optical image that does not contain ultraviolet light,
When the photocathode has no sensitivity to ultraviolet light, or when ultraviolet light is to be subjected to spectral imaging, an ultraviolet filter may not be provided. Also, when acceleration or multiplication of photoelectrons from the photocathode is not required, it is not necessary to provide an MCP in the image tube.

On the other hand, for example, a spectral imaging apparatus that individually extracts specific wavelengths (for example, R, G, and B components) without attaching an RGB combining circuit or the like may be used. In this case, the selected wavelength is variably set according to the potential of the photocathode of the image tube.

〔The invention's effect〕

As described above in detail, in the present invention, the initial speed of the photoelectrons emitted from the photocathode is a value corresponding to the energy of the incident light, that is, the wavelength. Only the incident light image of the wavelength can be selectively picked up.

The above-mentioned extraction of photoelectrons can be realized by disposing an electron transmission type electrode facing the photocathode and applying a predetermined level of extraction voltage between the electrode and the photocathode. By changing the level of the extraction voltage, it is possible to change the wavelength of the optical image to be picked up. For example, by mixing the R, G, and B components, color imaging can be performed.

According to the present invention, spectral imaging and color imaging can be performed by one image tube, so that the configuration of the imaging device can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a color spectral imaging apparatus according to an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing the operation of the embodiment, and FIGS. 4 to 6 are graphs showing specific examples. It is. 2 ... UV filter, 3 ... Image tube, 31 ... Photocathode, 32 ... Grid electrode, 33 ... MCP, 34 ... Fluorescent screen, 4 ... Relay lens, 5 ... Imaging device, 61 ... …
Video signal changeover switch, 62 Cathode voltage changeover switch, 71 RGB memory, 72 GB memory, 73 B memory, 81 R arithmetic circuit, 82 G arithmetic circuit, 9 RG
B synthesis circuit, 10 Control circuit.

Claims (3)

(57) [Claims] 1. A photoelectric conversion means having an external electron emission type photocathode, on which an optical image to be imaged is incident on the photocathode, and having an initial velocity in a predetermined range among photoelectrons emitted from the photocathode. Means for extracting an object and generating the optical image having a specific wavelength corresponding to the range of the initial velocity. 2. An external electron emission type photocathode which receives an optical image to be picked up on one surface and emits photoelectrons from the other surface, and is disposed opposite to the other surface side of the photocathode. An image-forming surface on which an image of photoelectrons is formed, and an electron transmission type electrode disposed between the image-forming surface and the photoelectric surface and having a predetermined level of extraction voltage applied between the photoelectric surface and the photoelectric surface. An image tube having: an extraction voltage switching means for switching the extraction voltage between a plurality of levels; controlling a switching operation of the extraction voltage switching means, and capturing an image of the imaging plane for each level of the extraction voltage. A spectral imaging apparatus comprising: imaging control means for outputting imaging data; and generating means for generating the optical image having a specific wavelength corresponding to the level of the extraction voltage based on the imaging data. 3. An external electron emission type photocathode which receives an optical image to be picked up on one surface and emits photoelectrons from the other surface, and said photocathode is disposed so as to face the other surface of said photocathode. An imaging surface on which an image of photoelectrons is formed, and an electron transmission type electrode disposed between the imaging surface and the photocathode and having a predetermined level of extraction voltage applied between the photocathode and the photocathode. And an extraction voltage for switching the extraction voltage between an RGB level at which the R, G, B components of the three primary colors can be extracted, a GB level at which the G and B components can be extracted, and a B level at which the B component can be extracted. Switching means, and an imaging control means for controlling the switching operation of the extraction voltage switching means, capturing an image of the imaging plane for each level of the extraction voltage and outputting imaging data, and wherein the extraction voltage is at an RGB level. Image data at the GB level from the image data at the time Calculating means for obtaining the R component data by subtracting the image data when the extracted voltage is at the B level from the image data when the extracted voltage is at the GB level to obtain the G component data by subtracting the image data when the extracted voltage is at the B level; A spectral imaging unit comprising: a generation unit configured to combine the B component imaging data output from the imaging control unit with the R component data and the G component data obtained by the calculation unit to generate a color image corresponding to the optical image. apparatus.