JP3219071B2 - Infrared laser imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared laser imaging apparatus, and more particularly to an infrared laser imaging apparatus used in a gas visualization apparatus for visualizing an invisible gas using a laser.

[0002]

2. Description of the Related Art Conventionally, attempts have been made to visualize an invisible gas using a laser. Methane gas, propane gas and the like have a strong absorption band in the infrared 3 micron band. By combining a laser strictly matched to the absorption wavelength with an infrared imaging device in this wavelength range, a highly sensitive gas visualization device can be realized.

[0003] A pyroelectric element can take out only a change in the incidence of infrared rays from its operating mechanism. Therefore, even if an infrared image of the target is obtained (passive imaging), there is no response if the infrared radiation from the target is constant.

For this purpose, a mechanical chopper is placed in front of a camera, and the surface of the chopper and the target image are alternately (30).
(At about Hz). When the chopper is at a constant temperature and the target temperature is slightly higher, the signal of the detection element starts to rise at the timing when the chopper is turned off from on, and reaches the maximum output just before the chopper is turned on again.

That is, the signal starts to rise at the timing when the chopper changes from a state in which the front surface of the sensing element is blocked (blocking state) to an open state (non-blocking state), and the chopper starts blocking the front surface of the sensing element again. The maximum output immediately before. Therefore, if the difference between the signal immediately before the rise and the signal immediately before the chopper is turned on again is read out as the output signal, the detection with the highest sensitivity is possible.

Now, special measures are required to read out each pixel at the above timing with a two-dimensional imaging device. For example, as shown in FIG. 4, various chopper shapes are considered. I have. With such chopping and the reading method synchronized therewith, the most sensitive signal reading is realized. In FIG. 4, 21 is a chopper, and 22 is a detection element.

[0007]

In the above-mentioned conventional gas visualization device, the presence of strong background light unique to the infrared region becomes a problem. In order to capture only laser light, it is desirable not to respond to background light. Since the pyroelectric type uncooled infrared element responds only to the changing infrared ray, if the irradiation laser is irradiated in a pulsed manner, it can naturally respond only to the laser reflected light.

However, the uncooled detector has a low-speed response,
Since the speed that can respond with the highest sensitivity is limited to the TV frame rate of about 30 Hz, the laser irradiation is turned on and off (ON,
OFF) is repeated, and it is necessary to read out the signal at the timing when the change becomes maximum, and the above-described chopping and the reading method synchronized therewith must be used.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide an infrared laser image pickup apparatus capable of removing background infrared radiation and picking up an image only by laser reflection without requiring a chopper. Is to do.

[0010]

An infrared laser imaging apparatus according to the present invention scans a laser beam of an infrared laser on a target surface, and uses the laser reflected light obtained by the scanning by electronic scanning synchronized with a laser beam scanner. The image is read out as a video signal from a pyroelectric uncooled two-dimensional infrared imaging device.

Another infrared laser imaging apparatus according to the present invention is an infrared laser oscillator for emitting a laser beam for irradiating a target surface, and a scanning optical system for scanning the laser beam emitted from the infrared laser oscillator on the target surface. A pyroelectric uncooled infrared imaging element on which laser reflected light obtained by the scanning of the laser beam by the scanning optical system forms an image; a scanning timing by the scanning optical system; and the pyroelectric uncooled infrared imaging element. There are provided means for synchronizing the scanning timing of the electronic scan of the imaging device with the electronic scanning, and means for reading out the image formed on the pyroelectric type uncooled infrared imaging device as a video signal.

That is, the infrared laser imaging apparatus according to the present invention relates to an active infrared imaging technique for imaging the reflection intensity of a laser beam using an infrared camera including an infrared laser and a two-dimensional solid-state imaging device, and more particularly, to an infrared laser imaging device using a pyroelectric element. The present invention relates to an infrared camera using a cooled two-dimensional infrared imaging device.

The number of pixels (for example, 25
By arranging pyroelectric infrared elements of only 6 × 256 pixels) two-dimensionally and electronically scanning them internally, it is possible to output a time-series infrared video signal. It is possible to reduce the size and weight of the camera.

By irradiating a target with a laser beam in combination with an infrared laser and imaging the reflection of the laser beam with an infrared camera, the spatial distribution of the reflected light can be measured. By irradiating the wavelength of the laser light in accordance with the absorption wavelength of a specific gas, it becomes possible to visualize the presence of an invisible gas.

A conventional infrared camera captures and visualizes infrared radiation from a target without irradiating a laser to enable visual recognition of the target even in darkness, and that the amount of infrared radiation is proportional to the temperature of the target. Is used to capture the target temperature distribution two-dimensionally.

The pyroelectric uncooled element can visualize only the variation of infrared radiation due to the operation principle of the element. Therefore, conventionally, an image is taken by using a mechanical chopper to alternately display a chopper blade and a target at a uniform temperature at room temperature. In this case, while devising the shape of the chopper and cutting the blade perpendicular to the pyroelectric element row, the row scan by electronic scan and the rotation of the chopper blade synchronize the timing of chopping the row so that the highest sensitivity is obtained. The signal is being read.

The present invention provides a use method in which a pyroelectric uncooled image pickup device can be used with the highest sensitivity in active infrared imaging using a laser. That is, the scanning according to the present invention in synchronization with laser irradiation makes it possible not to respond to infrared radiation from a target (background) while capturing only the change due to laser irradiation with the highest sensitivity. By using this method, it is possible to detect only laser light with high sensitivity without using a chopper and without responding to background infrared radiation.

[0018]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an infrared laser imaging apparatus according to one embodiment of the present invention. In the figure, an infrared laser imaging device according to one embodiment of the present invention includes an infrared laser oscillator 1, a laser scanning optical system 2, an imaging lens 3 of an imaging camera, a pyroelectric uncooled imaging device 4,
It comprises a signal processing unit 5, a camera head 6 of an infrared camera, and a control device 7.

The infrared laser oscillator 1 oscillates a laser beam at a wavelength corresponding to the resonance absorption wavelength of the gas to be visualized. The laser scanning optical system 2 is for scanning and irradiating the laser beam from the infrared laser oscillator 1 in the form of a rectangular beam whose longitudinal direction is perpendicular to the target surface in the horizontal direction. The imaging lens 3 of the imaging camera is an infrared camera lens.

The pyroelectric type uncooled image sensor 4 includes a signal processor 5
Thereby, an infrared video signal is read. The camera head 6 of the infrared camera is the same as the conventional uncooled infrared camera except that there is no chopper. The control device 7 synchronizes the horizontal scan timing of the laser scanning optical system 2 with the horizontal scan timing of the electronic scan of the uncooled image sensor 4.

The wavelength of the laser beam from the infrared laser oscillator 1 is adjusted near the peak of the resonance absorption spectrum of the gas to be visualized. Laser scanning optical system 2
The laser beam is shaped into a rectangular uniform irradiation pattern, irradiates the target plate 8, and is repeatedly scanned in the horizontal direction.

The scanning of the laser beam is controlled in synchronization with the electronic scanning timing of the uncooled image pickup device 4 by a synchronization signal from the control device 7. The irradiated laser beam is reflected by the target plate 8 and the diffused light is imaged on the uncooled image sensor 4 by the imaging lens 3 of the imaging camera, and the image is output from the uncooled image sensor 4 by the signal processor 5. Read as a signal.

In this case, the target plate 8 (for example, a wall) irradiated with the laser light can be displayed on a television as an image as if the target plate 8 is illuminated by the laser light. If there is a gas leak or the like in the space on the way, the gas is strongly attenuated on the optical path, and the location where the gas exists is visualized as a shadow picture.

Here, since the pyroelectric type uncooled image pickup device 4 responds only to a change in infrared rays, it does not respond to infrared radiation from a stationary background, but the target plate 8 irradiated with a laser beam. Since the reflected light enters in a pulsed manner, only the laser reflection is read out as a signal.

The pyroelectric type uncooled image pickup device 4 includes a two-dimensionally arranged pyroelectric device and an IC (integrated circuit) (for example, CCD: Char) for reading out electric signals two-dimensionally by electronic scanning.
geCoupled Device), it is important to synchronize the timing between the laser scanning optical system 2 and the electronic scan in order to detect a signal with high sensitivity.

That is, when scanning a rectangular irradiation beam horizontally, the vertical column scanning of the pyroelectric type uncooled imaging element 4 is performed at high speed, the horizontal column scanning is synchronized with the horizontal scanning of the laser beam, and the pyroelectric element is scanned. By reading the signal at the timing when the signal change from the infrared incident change is the largest, the signal is read with the highest sensitivity.

FIG. 2 is a diagram showing an example of horizontal scanning irradiation of a rectangular beam in the infrared laser imaging apparatus according to one embodiment of the present invention. In the figure, a rectangular beam 11 having a vertical direction as a longitudinal direction is indicated by an arrow A on an imaging region 12.
(Horizontal direction).

FIG. 3 is a diagram showing another example of scanning irradiation of a rectangular beam in the horizontal direction in the infrared laser imaging apparatus according to one embodiment of the present invention. In the figure, a rectangular beam 13 converted into a fiber by an optical fiber 14 is sequentially scanned in the direction of arrow A (horizontal direction) on the imaging area 12.

In this case, assuming that the imaging region 12 is divided into n (n is a positive integer), the rectangular beam 13 is, for example, the first to fifth regions of the n-divided imaging region 12,
The sixth to sixth areas,..., The n-th area, and the first to fourth areas
The area is scanned sequentially, such as the second area. According to this method, the laser beam is not irradiated to an area other than the imaging area 12, and the energy used is not wasted. Incidentally, reference numeral 15 denotes a prism.

As described above, the laser beam emitted from the infrared laser oscillator 1 at a wavelength corresponding to the resonance absorption wavelength of the gas to be visualized is directed by the laser scanning optical system 2 onto the target plate 8 in a direction perpendicular to the longitudinal direction. While irradiating in the form of a rectangular beam, and repeatedly scanning in the horizontal direction,
The horizontal scanning timing of the laser scanning optical system 2 and the horizontal scanning timing of the electronic scanning of the uncooled image sensor 4 are synchronized by the control device 7, and the laser beam reflected by the target plate 8 is not cooled by the imaging lens 3 of the imaging camera. Image sensor 4
By forming an image on the top and reading it out as a video signal from the uncooled imaging device 4 by the signal processing unit 5, it is possible to remove infrared radiation from the background and capture only laser reflection.

Further, by using the pyroelectric type uncooled image pickup device 4, the cooling of the detector becomes unnecessary, so that the infrared laser image pickup device can be reduced in size and power consumption, and the weight can be reduced. And cost reduction can be realized. In this case, since a chopper conventionally required is not required, it is possible to further simplify and reduce the size of the infrared camera using an ordinary pyroelectric type uncooled imaging device 4.

Further, by synchronizing the scanning of the laser irradiation beam by the laser scanning optical system 2 and the electronic scanning of the pyroelectric type uncooled image pickup device 4, the reflected light of the laser is detected with the highest sensitivity. be able to.

Although the scanning is performed in the horizontal direction in the embodiment of the present invention, the same effect as described above can be obtained by performing the scanning in the vertical direction and performing the electronic scanning of the image pickup device in the same manner as the TV raster scan. Can be

[0034]

As described above, according to the present invention, a laser beam of an infrared laser is scanned on a target surface, and the laser reflected light obtained by the scanning is pyroelectrically scanned by electronic scanning synchronized with the laser beam scanner. By reading as a video signal from the uncooled two-dimensional infrared imaging device of the mold, there is an effect that the infrared radiation of the background can be removed and an image can be captured only by laser reflection without requiring a chopper.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an infrared laser imaging device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of scanning irradiation of a rectangular beam in the horizontal direction in the infrared laser imaging device according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating another example of scan irradiation of a rectangular beam in the horizontal direction in the infrared laser imaging device according to one embodiment of the present invention.

FIG. 4 is a diagram showing a conventional chopper shape.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 infrared laser oscillator 2 laser scanning optical system 3 imaging lens of imaging camera 4 pyroelectric uncooled imaging element 5 signal processing unit 6 camera head of infrared camera 7 control device 8 target plate 11, 13 rectangular beam 12 imaging area 14 Optical fiber

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/61 G01J 1/00-1/60 G01V 3 / 16 G01J 5/00-5/62

Claims (6)

(57) [Claims] 1. A laser beam of an infrared laser is scanned on a target surface, and a laser reflected light obtained by the scanning is imaged from a pyroelectric uncooled two-dimensional infrared imaging device by electronic scanning synchronized with a laser beam scanner. An infrared laser imaging device characterized by reading out as a signal. 2. An infrared laser oscillator for emitting a laser beam for irradiating a target surface, a scanning optical system for scanning a laser beam emitted from the infrared laser oscillator on a target surface, and the laser by the scanning optical system. Pyroelectric uncooled infrared imaging element in which laser reflected light obtained by beam scanning forms an image, scanning timing by the scanning optical system, and scanning timing of electronic scanning by the pyroelectric uncooled infrared imaging element An infrared laser imaging apparatus, comprising: means for synchronizing image data; and means for reading out the image formed on the pyroelectric type uncooled infrared imaging element as a video signal. 3. The infrared laser imaging apparatus according to claim 2, wherein the infrared laser oscillator oscillates the laser beam at a wavelength corresponding to a resonance absorption wavelength of a gas to be visualized. 4. The scanning optical system shapes the laser beam into a rectangular beam having one of a vertical direction and a horizontal direction of the target surface as a longitudinal direction, and converts the rectangular beam into a vertical direction and a horizontal direction of the target surface. 4. An infrared laser imaging apparatus according to claim 2, wherein the infrared laser imaging apparatus is configured to scan the other side. 5. An infrared laser imaging apparatus according to claim 2, further comprising an imaging lens for imaging said laser reflected light on said pyroelectric type uncooled infrared imaging device. apparatus. 6. The scanning optical system according to claim 1, wherein the scanning optical system is configured to sequentially scan each of a plurality of divided areas among the imaging areas of the target surface divided into n (n is a positive integer). The infrared laser imaging device according to any one of claims 2 to 5.