JPS637370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spectral imaging device for obtaining an image of a subject at a specific wavelength.

The above-mentioned spectroscopic imaging device is used to analyze geological features in aerial photogrammetry, and to analyze the colors of original maps in the fields of textile dyeing and printing.

Conventional spectroscopic imaging devices are configured to use a vibrating or rotating reflector between an optical system with an extremely narrow field of view and the subject, and optically scan the subject by vibrating or rotating the reflector. There is. Through the scanning, the light from a part of the object that has entered the optical system is separated by a prism, and light of a desired wavelength is detected by a separate photodetector.

Only components corresponding to light of a desired spectrum are extracted from the output signal of the photoelectric detector by scanning in synchronization with the vibration or rotation of the reflecting mirror. From these components, the image of the subject was reconstructed using light of a specific wavelength.

Since such conventional spectroscopic imaging devices require mechanically movable parts such as vibrating or rotating reflecting mirrors, it is difficult to make the devices smaller and lighter.

Furthermore, in the conventional spectroscopic imaging apparatus, in order to change the wavelength to be detected, it is necessary to change the position angle of the prism, and for this purpose, it is necessary to prepare a rotation adjustment section.

An object of the present invention is to provide a spectroscopic imaging device that uses a completely novel configuration to obtain an image at a desired wavelength by selecting the frequency of an oscillator, and does not require mechanical moving parts as in conventional devices. There is a particular thing.

In order to achieve the above object, a spectroscopic imaging device using an acousto-optic filter according to the present invention has the following features:
For the image source to be measured, a first pinhole plate, a collimator lens, an acousto-optic filter, a focusing lens,
A second pinhole plate, an image intensifier are arranged in this order, and a control device for controlling characteristics of the acousto-optic filter, and the collimator lens is connected to the pinhole of the first pinhole plate. The light transmitted through the acousto-optic filter is incident on the incident surface of the acousto-optic filter, the acousto-optic filter performs Bragg diffraction on the incident light and outputs it at a constant deflection angle, and the focusing lens directs the emitted light to the second pinhole. The image intensifier is configured to receive light from the pinhole in the second pinhole plate onto a photocathode and intensify its image.

According to the above configuration, the object of the present invention can be completely achieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A spectroscopic imaging apparatus using an acousto-optic filter according to the present invention will be described in detail below with reference to the drawings and the like.

FIG. 1 is a schematic diagram of an embodiment of the spectroscopic imaging apparatus of the present invention.

FIG. 2 is a longitudinal cross-sectional structural diagram for explaining the structure of an acousto-optic filter used in the spectroscopic imaging apparatus shown in FIG. 1. The same parts as shown in FIG. 1 are given the same numbers.

A pinhole 2 is provided in a part of the outer wall of the dark box 1. The outer wall of the dark box 1 in which the pinhole 2 is provided forms a first pinhole plate.

When using the spectroscopic imaging apparatus according to the present invention, this pinhole 2 is arranged so as to receive light from the subject 14, and a first
With respect to the pinhole plate, the collimator lens 5,
An acousto-optic filter 6, a focusing lens 7, a second pinhole plate, and an image intensifier 8 are arranged in this order.

The front focal point of the collimator lens 5 is aligned with the pinhole 2 of the first pinhole plate. Therefore, the collimator lens 5 converts the light from the object that is incident through the pinhole 2 into parallel light and causes it to enter the acousto-optic filter 6. The acousto-optic filter 6 emits the parallel light from the collimator lens 5 at a constant deflection angle (only light of a specific wavelength).
A shielding wall 4 having a pinhole 3 is provided between the focusing lens 7 and the image intensifier 8 at the back focal point of the focusing lens 7. This shielding wall 4 forms a second pinhole plate. A window is provided in a part of the outer wall of the room housing the image intensifier 8 so that the screen 10 of the image intensifier 8 can be observed from the outside.

The parallel light emitted from the acoustic filter 6 at a constant deflection angle becomes monochromatic light with a specific wavelength determined by the physical constants and shape constants of the crystal constituting the acousto-optic filter 6 and the frequency of the sound wave applied to the crystal. ing.

In order to obtain the constant deflection, the crystal forming the acoustic filter 6 must satisfy certain conditions.

Next, an example of an acousto-optic filter will be described in detail with reference to FIG. The material of the crystal is tellurium dioxide (TeO ₂ ).

The surface 63 on which the light L is incident is inclined by 18.6 degrees from the [110] axis of the tellurium dioxide crystal (that is, the second
In the figure, θi = 18.6°). The surface 64 from which the light L is emitted is inclined by 14.93° from the [110] axis of the crystal (that is, θo = 14.93° in Fig. 2).The opposing side surfaces 65 and 66 are inclined from the [001] axis of the crystal.
It is tilted by 1.6° (i.e., α=
1.6°). All of the four planes include the [110] axis of the crystal.

A transducer 61 is attached to the side surface 66. An acoustic wave absorber 62 is attached to the side surface 65. The transducer 61 is a crystal [110]
It generates acoustic waves of any frequency in the range of 39 to 104 MHz with transverse waves that vibrate in the axial direction. The acoustic wave is driven by a voltage wave in the frequency range provided by a controllable oscillator 12.

Of the light that is perpendicularly incident on the surface 63 of the optical crystal as described above, the wavelength abnormal light component corresponding to the frequency of the acoustic wave is incident on the crystal and causes anisotropic Bragg diffraction due to the acoustic wave. Then, due to anisotropic Bragg diffraction, the plane of polarization is rotated by 90° and becomes an ordinary ray. The light is then emitted with a deflection angle of 1.68° from the incident light (the angle formed by the light that enters the crystal and the light that is diffracted and refracted within the crystal and exits from the crystal).
This deflection angle is within the frequency range of the acoustic wave mentioned above, 39MHz.
Wavelength range 800nm to 400nm corresponding to ~104MHz
It is constant regardless of the wavelength of the emitted light.
(θo = 14.93° is the most important value for keeping the deflection angle constant) Figure 3 shows the relationship between the frequency of the acoustic wave and the wavelength of the light emitted with the dispersion angle of 1.68°.

Note that the light of other wavelengths incident on the optical crystal 6 and the light of the ordinary light component at the wavelength corresponding to the acoustic frequency are emitted in different directions.

The optical axis of the focusing lens 7 is aligned with the direction of the light emitted from the acousto-optic filter 6. Therefore, the light incident on the acousto-optic filter 6 as parallel light becomes monochromatic parallel light with a specific wavelength and enters the focusing lens 7, and the rear focus (second
pinhole 3) in the shielding wall 4 which is the pinhole plate of
focus on.

Light of other wavelengths incident on the optical crystal 6 and ordinary light component light at a wavelength corresponding to the acoustic frequency are absorbed by the inner wall of the dark box 1 and disappear.

Since the photocathode 9 of the image intensifier 8 faces the second pinhole 3, a subject image of a specific wavelength is projected. The object image of a specific wavelength projected onto the photocathode 9 is intensified to a light intensity several thousand times, and then transmitted to the fluorescent surface 10 of the image intensifier 8.
appears in

Next, a control device for controlling the characteristics of the acousto-optic filter and a related display device will be explained. When a desired wavelength is manually input to the wavelength controller 11, the voltage corresponding to the wavelength is changed to the controllable oscillator 12.
will be sent to. The controllable oscillator 12 uses the voltage input from the wavelength controller 11 as an output wave instruction signal, and sends out a voltage wave of a corresponding frequency to the transducer 61. The wavelength controller 11 converts a manually input signal into a signal of an appropriate format and sends it to the wavelength display device 13. The wavelength display device 13 displays to the observer, through numbers or meter indications, the wavelength of the image appearing on the fluorescent surface 10 of the image intensifier 8 from the subject. The wavelength controller 11 may be such that two wavelengths are manually input and an output voltage that automatically sweeps between the two wavelengths is delivered.

As explained above, the spectral imaging device according to the present invention can easily obtain an image formed by a specific wavelength from a subject by electrically controlling its characteristics using an acousto-optic filter.

This eliminates the need for reflective mirrors and prisms as in conventional devices, making it possible to provide a compact and lightweight spectral imaging device with no mechanically moving parts.

Since a specific wavelength can be selected by electrical control, it becomes easy to observe a large number of wavelengths automatically or sequentially according to a predetermined program.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram for explaining an embodiment of a spectroscopic imaging apparatus of the present invention. FIG. 2 is a vertical cross-sectional structural diagram for explaining the structure of the acousto-optic filter used in the spectroscopic imaging apparatus shown in FIG. 1, and FIG. 3 is a graph for explaining the characteristics of the acousto-optic filter. 1...Dark box, 2...(1st) pinhole, 3...
... (Second) pinhole, 4 ... Shielding wall, 5 ... Collimator lens, 6 ... Acousto-optic filter, 61
...Acoustic transducer, 62...Acoustic wave absorber, 7...Focusing lens, 8...Image intensifier, 9...Photocathode of image intensifier, 10...Screen of image intensifier , 11... Wavelength controller, 12...
Variable oscillator, 13...wavelength display device.

Claims (1)

[Claims] 1. With respect to the image source to be measured, a first pinhole plate,
A collimator lens, an acousto-optic filter, a focusing lens, a second pinhole plate, and an image intensifier are arranged in this order, and a control device for controlling characteristics of the acousto-optic filter,
The collimator lens allows the light transmitted through the pinhole of the first pinhole plate to be incident on the incident surface of the acousto-optic filter, and the acousto-optic filter performs Bragg diffraction on the incident light and outputs it at a constant deflection angle, The focusing lens focuses the emitted light onto the pinhole of the second pinhole plate, and the image intensifier receives the light from the pinhole of the second pinhole plate on a photocathode and intensifies its image. A spectroscopic imaging device using an acousto-optic filter configured to 2. A spectroscopic imaging device using an acousto-optic filter according to claim 1, wherein the acousto-optic filter is a tellurium dioxide crystal.