JPS60256119A - Spectral imaging device - Google Patents

Abstract

PURPOSE:To perform spectral imaging without any position shift with wavelength by interposing an optical device whose wavelength dispersion characteristic is complementary to an acousto-optic element between an image formation surface and the acousto-optic element. CONSTITUTION:Prisms 5 and 6 as the optical device whose wavelength dispersion characteristic is complementary to the acousto-optic element 4 are interposed between the acousto-optic element 4 and an image pickup tube 7. Images are formed on an image plane S at different positions P1 and Q1 by wavelength components of lambdamax and lambdamin without the prisms 5 and 6. When, however, the prisms 5 and 6 are interposed, the angle of incidence and the angle of projection become equal to each other and the images are formed on the image pickup tube 9 at the same position. Therefore, spectral imaging having no position shift with wavelength is attained by utilizing ordinary diffracted light having superior image separation in an acoustic wave propagating direction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a spectral imaging device using an acousto-optic element.

(Prior Art) A spectroscopic imaging device is capable of extracting a specific wavelength component from light that forms an image to be measured and observing an image formed by the light of that wavelength component (1). Conventional spectral imaging devices are constructed using a vibrating or rotating reflecting mirror.

The inventors of the present application have invented and experimented with a spectroscopic imaging device without such moving parts using an acousto-optic element such as a tellurium dioxide (Te02) crystal.

A spectroscopic imaging apparatus using an acousto-optic element will be briefly described with reference to FIG.

This device includes a Vinpole plate 102, a collimator lens 105, an acousto-optic element 1
06, a focusing lens 107, and an image intensifier 108 are arranged in this order.

The collimator lens 105 directs the light transmitted through the pinhole of the first pinhole plate 102 to the acousto-optic element 1.
06 incident surface.

The acousto-optic element 106 is an acoustic transducer 161
and an acoustic wave absorber 162 are connected, and the acoustic transducer 161 is excited by the variable frequency oscillator 112.

(2) The acousto-optic element 106 performs Bragg diffraction on the human 1.1 light, -υ, disperses it at an angle corresponding to the wavelength of the incident light and the driving frequency of the acoustic I.Lance dial 61, and emits it.

11; 3 The fiber bundle L/lens 107 forms an image of the emitted light emitted at a constant deflection angle on the surface of the image detection device 108.

1111 The behavior of the incident light on the acousto-optic element 106 changes depending on the polarization state of the incident light, and the light that has passed through the acousto-optic element 7-106 is divided into two types: non-diffracted light B, non-diffracted light B, and diffracted light B-106. It can be divided into C.

Next, the behavior of incident light on the acousto-optic element 7-6 will be explained with reference to FIGS. 5 and 6.

The diffraction angle of the extraordinary incident diffracted light A hardly changes depending on the wavelength of the incident light. Therefore, the apparatus shown in FIG. 4 utilizes the extraordinary incident diffracted light beam.

As a result, the diffraction angle of the incident lightning diffracted light C changes depending on the wavelength.

This state is shown in comparison with FIG. 6.

(3) When the wavelength of the ordinary incident diffracted light C changes from 400 nm to 800 nm, the l1jI refraction angle changes in the range of approximately 12° to 10°, whereas the extraordinary incident diffraction angle changes from 4.5° to 3.0°.
It varies within a range of 8°.

The inventors of the present application have conducted various studies on the extraordinary incident diffracted light beam A, and found that the extraordinary incident diffracted light beam A undergoes image shift (blurring) in the diffraction direction due to the influence of the propagation of the acoustic wave, and the input signal I discovered that the decomposition of (image) is tO. As a result, such an image shift does not occur in the lightning incident diffracted light C, but since the images formed by each monochrome are shifted in the imaging device 1-, there is a risk that problems may occur in later image calculation processing, etc. There is.

(Object of the Invention) An object of the present invention is to provide a spectral imaging device that solves the problem of wavelength dependence of the diffraction angle of light transmitted through an acousto-optic element.

(Structure of the Invention) In order to achieve the above object, a spectroscopic imaging device according to the present invention is a spectroscopic imaging device that takes out a monochromatic image of an image using an acousto-optic element, (4) The diffraction angle of the wave 1fi, l changes. Is the movement of the imaging position caused by light whose long dispersion characteristic l11- is complementary to the element described above? It is constructed by inserting the device into the imaging tube 1-8.

(Example) The present invention will now be described in more detail with reference to the drawings and the like.

FIG. 1 is a 7g'J' diagram showing an embodiment of the spectroscopic imaging device according to the present invention.

In this device, a pinhole 2, a collimator 1/lens 3, and an acousto-optic element 4 are arranged in this order on an oscillator 1 to be regulated.

The collimator lens 3 makes the light transmitted through the pinhole of the vinyl pole plate 2 enter the incident surface of the acousto-optic element 4.
Uru.

An acoustic transducer 4a and an acoustic wave absorber 4b are connected to the acousto-optic element 4, and an acoustic transducer 4b is connected to the acoustic transducer 4a.
--Li 4a is excited by 1 in the variable frequency oscillator 10.

In this example, E FL-FIOO manufactured by Matsushita Electrical Parts Co., Ltd.
This enables spectroscopic imaging up to

The acousto-optic element 4 undergoes Bragg diffraction of the incident light -U
The wavelength of the incident light and the acoustic I/Lance j, -sa 4b
The light is dispersed and emitted at angles corresponding to the driving frequency.

The prism 5.6 has the same shape and forms an optical device whose wavelength dispersion characteristics are complementary to the acousto-optic element 4.

The light that has passed through the prism 5.6 reaches the photocathode of the image pickup tube 7, where it is photoelectrically converted, extracted as a television signal, and subjected to image processing.

As described above, the diffraction angle of the normally incident diffracted light is wavelength dependent, and the shorter the wavelength, the larger the amount of diffraction, and the longer the wavelength, the smaller the amount of diffraction.

The diffraction angle for a wavelength of 400 nm (-λmin) is 19
3 milliradians (m rad), wave W700 nm (
-λmaχ) has a diffraction angle of 155 milliradians (m ra
d).

Select wavelength of λwax by variable frequency oscillator IO (6
), the center of the image that has not been converted into a parallel beam by the collimator lens 3 is incident on the point p of the prism 5.

If the prism 5 is removed and the image plane S is set at a position equivalent to the photocathode of the image pickup tube 7, an image formed by the wavelength component of λmax will appear on the image plane S as pl.

Similarly, if the wavelength λmin is selected by the variable frequency oscillator lO and is 7, the center of the image converted into a parallel beam by the 21 meter lens 3 will be incident on point q of the prism 5, and the prism 5 will be removed in the same way and the image plane S If we set λ
The image formed by the wavelength component of min is 91 in the image plane S.
Appears like.

This 31-diffraction light image of the incident lightning appears at a different position depending on the wavelength at which the image is formed.

If the image pickup tube 7 is placed at a location corresponding to the image plane S, the image points formed by different wavelengths generated from the same point of the original image source 1 to be measured will be located on the photocathode. Since the images are projected at different points at the same time and are made to correspond to different positions of the television signal (7), subsequent image processing calculations become complicated.

In this embodiment, the points of images formed by different wavelengths generated from the same point of the original image source 1 to be measured are made to coincide on the photocathode.

FIG. 3 is an enlarged view of a part of an optical device whose wavelength dispersion characteristics are in a complementary relationship with the acousto-optic element.

Prisms of the same shape made of optical glass BK7 5.
6 is arranged symmetrically with respect to the plane O-0.

The angle of incidence of each wavelength selected by the acousto-optic element 4 on the prism 5 varies depending on the wavelength, and in this embodiment, the wavelength λ
The incident angle θin of o+ax is the smallest, and the incident angle θin of wavelength λwin is the largest.

The apex angle θ of the prism 5 is selected so that all of these lights are 3L emitted from the exit surface at the same exit angle θout.

Incident angle θin, output angle θout, apex angle θ of prism 5
The following relationship holds between n and the refractive index n of the glass forming the prism.

(8) sin θOu
l)...■ Wavelength λl1la, λmin and the wavelengths in between, respectively, the incident angle θin and the refractive index n-/J < . The apex angle of the prism at which sin θout is approximately constant is selected.

In this example, when θ is set to 68.5°, the change in θout for all wavelengths is the smallest, and with a prism with this apex angle, θ0u((λma)−θout(λm1n)<0.
It has been confirmed by calculation that the value is 4'.

Since the prism 6 is arranged symmetrically with the prism 5 on the plane O--O, the incident angle of the light of each wavelength reaching the incident surface of the prism 6 is equal to the output angle θouL.

The light that has passed through the prism 6 is emitted at an angle equal to the angle of incidence when it enters the prism 5, and reaches the same point on the photocathode of the first imaging device 7.

(9) Therefore, the points of images formed by different wavelengths generated from the same point on the original image source 1 to be measured are made to coincide on the photocathode.

(Effects of the Invention) As described above, in the spectroscopic inosing device according to the present invention, the movement of the imaging position by the wavelength ti+ characteristic is in a complementary relationship with the acousto-optic element each time the diffraction angle changes depending on the wavelength. Since the optical device is inserted into the imaging path, images of different wavelength components generated at any point on the image source to be measured can be made to correspond to the same point on the imaging device or the like.

Therefore, by using lightning diffraction light, which is excellent at resolving images in the direction of acoustic wave propagation, it has become possible to perform spectral imaging without positional shifts due to wavelength.

Since the points of the images formed by the respective wavelengths generated from the same point of the original image source 1 to be measured are coincident with each other at the photocathode 1-, they are the same as that of the video signal. The corresponding parts will be placed in the same position.

Therefore, when processing image signals, it is possible to significantly simplify the memory for storing the output of those signals and the arithmetic processing of the contents between those memories (10).

As an additional effect, since no positional shift occurs due to wavelength, it is possible to use an imaging device with the light-receiving surface necessary to capture an image of any wavelength. There is no longer any need to prepare the sides.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a spectroscopic imaging apparatus according to the present invention. FIG. 2 is a graph for explaining image shift when no optical device for correction is used. FIG. 3 is an enlarged optical path diagram showing a part of the optical device in which the wavelength dispersion characteristics of the spectral imaging device according to the present invention are complementary to the acousto-optic element. FIG. 4 is a block diagram showing a conventional spectroscopic imaging device. FIG. 5 is a schematic diagram for explaining the behavior of various types of incident light on the acousto-optic element. FIG. 6 is a graph showing the difference in diffraction angles between ordinary light and Tatsumi ordinary light. 1... Image source to be measured 2... Pinball plate 3... Collimator lens 4... Acousto-optic element 5.6... Prism 7... Imaging device 10... Variable frequency oscillator 102. ...Pinhole plate 105...Collimator lens 106...Acousto-optic element 107...Grid lens 108...Image intensifier 112...
Variable frequency oscillator 114... Image source to be measured 161... Acoustic transducer 162... Acoustic wave absorber Patent applicant Hamamatsu Photonics Co., Ltd. Agent Patent attorney Hisashi Inoro

Claims (2)

[Claims] (1) In a spectroscopic imaging device that takes out a monochromatic image of an image using an acousto-optic element, an optical device whose wavelength dispersion characteristic is complementary to that of the acousto-optic element is used to control the movement of the imaging position due to changes in the diffraction angle depending on the wavelength. A spectral imaging device characterized by being configured by being inserted into an imaging path. (2) The spectral imaging device according to claim 1, wherein the optical device is a pair of prisms of the same shape inserted between the imaging plane and the acousto-optic element.