JP2000152081A - Method and device for infrared image pickup - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for infrared image pickup which don't pick up the image of background radiation and allow an infrared interference filter to be replaced. SOLUTION: An infrared laser 1 oscillates with a wavelength matched with the resonance absorption wavelength of gas to be visualized. An optical system 2 make the laser light uniform to irradiate an irradiation area by an irradiation optical system. An image forming lens 3 of an image pickup camera is a camera lens for the infrared area. It is desirable that the temperature of a low temperature source 8 is as low as possible, but it is the temperature of liquid nitrogen in a form of this implementation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared imaging method and an infrared imaging apparatus for imaging the reflection intensity of laser light using an infrared camera using an infrared laser and a two-dimensional solid-state infrared imaging device.

[0002]

2. Description of the Related Art A two-dimensional solid-state image sensor has a pixel number (for example, 2 pixels).
Photodiodes of only 56 × 256 pixels) are two-dimensionally arranged, and a time-series infrared video signal can be output by electronically scanning internally, thereby dramatically improving the performance of a conventional mechanical scanning type infrared imaging apparatus. If the target is uniformly irradiated with a laser beam in combination with an infrared laser and its reflection is imaged by such a camera, the spatial distribution of the reflected light can be measured. By irradiating the wavelength of the laser light according to the absorption wavelength of a specific gas, it becomes possible to visualize the presence of invisible gas. Exists.
A high-sensitivity gas visualization device can be realized by combining a laser strictly matched with the absorption wavelength with an infrared imaging device in this wavelength range).

[0003]

However, conventionally, when a two-dimensional solid-state imaging device is used for such a purpose, in order to improve its performance, strong background radiation from an object other than a laser must be removed. Since the laser light has a narrow spectral width, it can be solved by adding a narrow band optical infrared interference filter. However, in the thermal infrared region, even if an infrared interference filter is used, if the infrared interference filter itself is at room temperature, background radiation from the infrared interference filter will occur. That is, in order to image only the laser beam, a narrow band infrared interference filter may be used,
In a wavelength region other than the transmission wavelength, background light such as visible light cannot be completely blocked. Other than the transmission wavelength, the infrared interference filter behaves like a mirror, but if there is a room-temperature object in the reflection direction, it will pick up radiation from it.

In order to make the infrared interference filter work effectively, it is conceivable to mount the infrared interference filter in a cooling dewar in which the image pickup device is housed. However, this method has a problem that the infrared interference filter cannot be replaced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an infrared imaging method and an infrared imaging apparatus capable of replacing an infrared interference filter without imaging background radiation. The point is to provide.

[0006]

SUMMARY OF THE INVENTION The present invention has the following arrangement to solve the above-mentioned problems. The gist of the invention according to claim 1 is an infrared imaging method using an infrared imaging device using an infrared interference filter in an infrared region, wherein a transmission wavelength range is transmitted as an incident signal to the infrared imaging device by the infrared interference filter. The infrared interference filter, which is provided on the infrared imaging element side, reflects light emitted from a low-temperature body that emits light belonging to a non-transmitting wavelength range reflected by the infrared interference filter, to the infrared imaging element by the infrared filter. As described above, there is provided an infrared imaging method characterized in that the light is reflected by the infrared filter. The gist of the invention according to claim 2 resides in the infrared imaging method according to claim 1, wherein the low-temperature body is the cooled infrared imaging element. The gist of the invention according to claim 3 resides in the infrared imaging method according to claim 1, wherein the low-temperature body is a cold shield that stores the cooled infrared imaging element. The gist of the invention according to claim 4 is an infrared imaging apparatus using an infrared imaging device using an infrared interference filter in an infrared region, wherein a transmission wavelength range is transmitted as an incident signal to the infrared imaging device side, and a non-transmission wavelength range is transmitted. An infrared filter that reflects light, a low-temperature body that is provided on the infrared image sensor side of the infrared filter and emits light that belongs to the non-transmitting wavelength range, and the infrared filter emits light from the low-temperature body by the infrared light. And a reflection mirror provided so as to reflect the light to the imaging element. The gist of the invention according to claim 5 is an infrared imaging apparatus using an infrared imaging device using an infrared interference filter in an infrared region, wherein a transmission wavelength range is transmitted as an incident signal to the infrared imaging device side, and a non-transmission wavelength range is transmitted. An infrared filter that reflects an input light from the infrared imaging device, and the infrared filter is formed in a spherical shell shape so as to reflect the input light from the infrared imaging device to the infrared imaging device. . The gist of claim 6 is as follows.
An infrared imaging apparatus using an infrared imaging device using an infrared interference filter in the infrared region, a plurality of infrared filters that transmit a transmission wavelength range as an incident signal to the infrared imaging device side and reflect a non-transmission wavelength range, A low-temperature body that emits light belonging to the non-transmitting wavelength region, which is provided on the infrared imaging element side of the infrared filter, and is installed such that the infrared filter reflects light emitted from the low-temperature body to the infrared imaging element. And a plurality of reflection mirrors, wherein the plurality of infrared filters are connected to each other by a turret so as to be rotatable around the axial direction of the turret. The gist of the invention according to claim 7 is that an infrared imaging device according to any one of claims 4 to 6, wherein a lens that transmits light having a transmission wavelength in parallel is disposed before and after the infrared imaging device. Exists in the device.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) FIG. 1 shows a conceptual diagram of an infrared imaging apparatus according to a first embodiment. In FIG. 1, reference numeral 1 denotes an infrared laser which oscillates at a wavelength corresponding to the resonance absorption wavelength of the gas to be visualized.

Reference numeral 2 denotes an optical system for uniformly irradiating an irradiation area with a laser beam by an irradiation optical system.

Reference numeral 3 denotes an imaging lens of an imaging camera, which is a camera lens in the infrared region.

Reference numeral 4 denotes a narrow band infrared interference filter for removing background light, the transmission wavelength of which is equal to the laser oscillation wavelength. The infrared image pickup device 5 is configured such that the radiation light (non-transmitting wavelength light) of the low-temperature source 8 reflected by the total reflection mirror 9 described below is reflected by the infrared interference filter 4 and input to the infrared image pickup device 5. It is inclined at about 45 °.

Reference numeral 5 denotes a two-dimensional infrared image pickup device.
A dimensional infrared intensity pattern can be read out in time series as a video signal. The infrared imaging element 2 is used after being cooled to the temperature of liquid nitrogen.

Reference numeral 6 denotes a cooled cold shield. In order to block unnecessary incident light from the imaging lens 3 so that unnecessary background light does not enter the imaging device, the cooled cold shield 6 is covered with the infrared imaging device 5.

Reference numeral 7 denotes a dewar as a vacuum container. A cold shield 6 is placed in the dewar 7. Although FIG. 1 is a plan view, the infrared
The cold shield 6 and the dewar 7 are drawn only in perspective so that the cold shield 6 and the dewar 7 are easily visible.

Reference numeral 8 denotes a low-temperature source. The temperature is desirably as low as possible, but in the present embodiment, it is the temperature of liquid nitrogen. The amount of infrared radiation is proportional to the fourth power of the absolute temperature ratio.
But (200/273) * 4 = 0.29, about 1 /
It can be reduced to 3.

It is to be noted that, for example, it can be cooled by an electronic refrigerator or the like (about -70 °).

Reference numeral 9 denotes a total reflection mirror. Since the narrow-band infrared interference filter 4 acts as a total reflection mirror in the cutoff wavelength region, the low-temperature source 8 is seen through the total reflection mirror 9 when viewed from the infrared imaging element 5.
As a result, background incidence other than the incidence from the narrow band signal can be significantly reduced to the infrared imaging element 5.
The infrared interference filter 4 has a transmission wavelength that matches the laser wavelength at 45 ° incidence.

In such an infrared imaging apparatus, as shown in FIG. 2, light of a transmission wavelength (solid line) from an object to be imaged passes through an infrared interference filter 4 and is input to an infrared imaging element 5. On the other hand, the low-temperature source 8 reflected by the total reflection mirror 9
(Dotted line) is reflected by the infrared interference filter 4 and input to the infrared imaging element 5. Therefore, the infrared interference filter 4 itself is not imaged. In FIG. 2, the non-transmitting wavelength light from the low-temperature source 8 is drawn slightly shifted so that the transmission does not overlap with the long hole. Less than,
4 and 7 are the same.

Since the infrared imaging apparatus according to the first embodiment is configured as described above, the following effects can be obtained.

Although the infrared interference filter 4 itself is at room temperature, the radiation from the infrared interference filter 4 due to the radiation from the low-temperature source 8 is sufficiently small. That is, when the room-temperature interference filter 4 is viewed with infrared light, the radiation at the non-transmission wavelength is:

[0021]

(Equation 1)

## EQU1 ##

[0023]

(Equation 2)

Then, since the interference filter 4 is mirror-finished,

[0025]

(Equation 3)

It is considered that: Therefore, the radiation by the infrared interference filter 4 is extremely small, and the influence on the imaging can be extremely reduced.

Since there is no infrared interference filter 4 in the dewar 7, the infrared interference filter 4 can be easily replaced.

Further, as shown in FIG. 9, lenses 3 'and 3' are disposed before and after the infrared interference filter 4, so that light transmitted through the infrared interference filter 4 can be made parallel.
In such a case, the signal light is made incident on the infrared interference filter 4 as a parallel light beam, and can be used as the infrared interference filter 4 having a sufficiently narrow band.

Conventionally, the cold shield 6 is attached to the entrance of the cold shield 6 for use as the cold infrared interference filter 4. However, if it is installed immediately before the infrared imaging element 5, the infrared rays spread in a conical shape and cannot enter as parallel light, so that there is a problem that the transmission width cannot be sufficiently narrowed. However, according to the present embodiment, since it is not immediately before the infrared imaging element 5, the imaging lens 3 can be arranged before and after the infrared interference filter 4, and in such a case, as the parallel light as described above, Light can be incident, and the transmission width can be reduced.

Further, since the background light can be cut and detected, the dynamic range can be expanded, and as a result, the sensitivity can be improved.

(Second Embodiment) In the infrared imaging apparatus according to the second embodiment, as shown in FIG. 3, a narrow-band infrared interference filter 14 is formed on a spherical shell surface. The transmission wavelength of the infrared interference filter 14 is transmitted to the infrared imaging device 15 in the same manner as a normal filter.
Except for the transmission wavelength, the infrared imaging element 5 is arranged so as to see itself cooled. However, since the infrared imaging element 5 is cooled, it is not detected (imaged). That is, the low-temperature source 8 according to the first embodiment is the infrared imaging element 5 itself.

According to such an infrared imaging apparatus, as shown in FIG. 4, the transmitted radiation passes through the infrared filter 14 and is input to the infrared imaging element 15. Radiation light (non-transmitting wavelength light) from the infrared imaging element 15 itself is reflected by the infrared interference filter 14 and is input to the infrared imaging element 15 again. Therefore, according to such an infrared imaging device,
Since the cooled infrared imaging device 15 itself is viewed, the same effect as the imaging device according to the first embodiment can be obtained without separately providing the low-temperature source 8 and the total reflection mirror 9 as in the first embodiment. be able to.

(Third Embodiment) In an infrared imaging apparatus according to a third embodiment, as shown in FIG. 5, a narrow band infrared interference filter 24 is attached to a rotating turret T. The turret T is rotatable in a plane parallel to the plane of FIG. At the opposite position, an infrared interference filter 34 is attached. The band width of the infrared interference filter 34 is different from that of the infrared interference filter 24.

In such an infrared imaging device, as shown in FIG. 7, transmitted radiation passes through an infrared filter 24 and is input to an infrared imaging device 25. Radiation light (non-transmitting wavelength light) from the cold shield 6 is transmitted to the infrared interference filter 2.
The light is reflected at 4 and is again input to the infrared imaging device 25. According to the infrared imaging device according to the third embodiment, in addition to the effects of the infrared imaging device according to the first embodiment,
The following effects are achieved. That is, the low-temperature source 8 according to the first embodiment is the cold shield 6 itself.

According to such an infrared imaging apparatus, the exchange of the infrared interference filter can be easily performed only by rotating the turret T.

By rotating the turret T in synchronization with the frame rate of the two-dimensional infrared imaging device 25, narrow-band imaging and normal infrared imaging can be alternately performed. This method can also be applied to a case where a plurality of different infrared interference filters are attached to continuously visualize the images of a plurality of gases. In addition, the present invention can be applied to the differential absorption method by using filters having different bands. In order to perform differential absorption, an interference filter having a wavelength of resonance absorption and an interference filter having no absorption near the resonance filter may be used so that an absorption effect can be correctly obtained from a difference between images.

Note that the present invention is not limited to the above embodiment, but can be applied to an infrared imaging apparatus suitable for applying the present invention.

Further, the number, position, shape, etc. of the above-mentioned constituent members are not limited to the above-mentioned embodiment, but can be set to a suitable number, position, shape, etc. for implementing the present invention. For example, as shown in FIG. 8, the number of infrared filters can be set to a number suitable for carrying out the present invention, such as three.

In each of the drawings, the same reference numerals (1, 11, 21, etc.) indicate the same constituent elements.

[0040]

Since the present invention is configured as described above, the following effects can be obtained. The infrared interference filter itself is at room temperature, but the low-temperature source does not image the infrared interference filter. In addition, since there is no infrared interference filter in the dewar, the infrared interference filter can be easily replaced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an infrared imaging device according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing the operation of the infrared imaging device shown in FIG.

FIG. 3 is a conceptual diagram of an infrared imaging device according to a second embodiment of the present invention.

FIG. 4 is a conceptual diagram showing the operation of the infrared imaging device shown in FIG.

FIG. 5 is a conceptual diagram of an infrared imaging device according to a third embodiment of the present invention.

FIG. 6 is a front view of the infrared interference filter fixed to the turret shown in FIG.

FIG. 7 is a conceptual diagram showing the operation of the infrared imaging device shown in FIG.

FIG. 8 is a front view showing a modified example of the turret shown in FIG. 6;

FIG. 9 is a conceptual diagram of an infrared imaging device according to another embodiment of the present invention.

[Explanation of symbols]

 1,11,21 Infrared laser 2,12,22 Irradiation optical system 3,13,23 Imaging lens 3 'Lens 4,14,24 Infrared interference filter 5,15,25 Infrared imaging device 6,16,26 Cold shield 7 , 17,27 Dewar 8 Low temperature source 9,29 Total reflection mirror 34 Infrared interference filter T Turret

Claims (7)

[Claims] 1. An infrared imaging method using an infrared imaging device using an infrared interference filter in an infrared region, wherein a transmission wavelength range is transmitted by an infrared interference filter as an incident signal to the infrared imaging device, and the infrared interference filter The infrared light is emitted from a low-temperature body that emits light belonging to a non-transmitting wavelength range that is reflected on the infrared interference filter and is reflected on the infrared image sensor by the infrared filter. An infrared imaging method comprising reflecting light from a filter. 2. The infrared imaging method according to claim 1, wherein the low-temperature body is the cooled infrared imaging device. 3. The infrared imaging method according to claim 1, wherein the low-temperature body is a cold shield that stores the cooled infrared imaging device. 4. An infrared imaging apparatus using an infrared imaging device using an infrared interference filter in an infrared region, the infrared filter transmitting a transmission wavelength range as an incident signal to the infrared imaging device side and reflecting a non-transmission wavelength range. And, a low-temperature body that emits light belonging to the non-transmitting wavelength range, which is provided on the infrared imaging element side of the infrared filter,
A reflection mirror provided so that the infrared filter reflects the radiation light from the low-temperature body to the infrared imaging element. 5. An infrared imaging apparatus using an infrared imaging device using an infrared interference filter in an infrared region, the infrared filter transmitting a transmission wavelength range as an incident signal to the infrared imaging device side and reflecting a non-transmission wavelength range. And an infrared imaging device, wherein the infrared filter is formed in a spherical shell shape so as to reflect input light from the infrared imaging device to the infrared imaging device. 6. An infrared imaging apparatus using an infrared imaging device using an infrared interference filter in an infrared region, wherein a plurality of transmission devices transmit a transmission wavelength region as an incident signal to the infrared imaging device and reflect a non-transmission wavelength region. An infrared filter, a low-temperature body that is provided on the infrared imaging element side of the infrared filter and emits light belonging to the non-transmitting wavelength range, and the infrared filter emits light from the low-temperature body to the infrared imaging element. An infrared imaging device, comprising: a reflection mirror installed so as to reflect the light; and wherein the plurality of infrared filters are mutually connected by a turret so as to be rotatable around an axial direction of the turret. 7. The infrared imaging device according to claim 4, wherein a lens that transmits light having a transmission wavelength in parallel is disposed before and after the infrared imaging device.