JPH1073483A - Infrared-photographing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily observe infrared rays of a large light quantity and a small light quantity by setting a variable control part for changing a charge accumulation time of an image pick-up element (CCD), etc. SOLUTION: Infrared rays emitted from an object are formed into an image at an infrared CCD element 1, photoelectrically converted and further subjected to a signal treatment at a signal-processing part 2. At the processing part 2, a function of an electronic shutter is utilized in place of a filter to control a charge accumulation time, thereby to regulate a light quantity. In other words, when the CCD element 1 is connected to an electronic shutter variable control part 4, an observation of a wide temperature range from a high temperature area to a low temperature area is continuously carried out. A high temperature area signal A and a low temperature area signal B from the processing part 2 are delayed by an amount corresponding to one screen at a delay circuit 3, and sent to a selecting circuit 5 and a comparing circuit 6. The selecting circuit 5 selects a screen on the basis of information from the comparing circuit 6 of whether the electronic shutter is driven or not. A pixel signal of a screen bringing about a saturation signal is replaced with a pixel of a screen for which the shutter is driven.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared imaging apparatus, and more particularly to an apparatus which can be used without being limited by the amount of infrared light.

[0002]

2. Description of the Related Art The configuration of a conventional infrared imaging apparatus is shown in FIG. In FIG. 6, 8 is an infrared optical system, 10 is an infrared CCD device as an image sensor, 9 is an ND filter, and 11 is an imaging circuit. The infrared light emitted from the observation target 12 on the left side in FIG. 6 is collected by the infrared optical system 8, passes through the ND filter 9, and is imaged on the infrared CCD device 10. At this time, if the saturation light amount of the infrared CCD element 10 is exceeded, observation by the infrared CCD element 10 becomes impossible.
For this reason, the ND filter 9 is inserted at an appropriate place in the optical system to reduce the amount of light, thereby attenuating the amount of light received by the infrared CCD device 10. This filter is shown in FIG.
As shown in FIG. 7, there are a fixed type and a type which is installed in an infrared light path when necessary and which is removed when unnecessary. As shown in FIG. 7, the ND filter 9 is driven by the motor 13 under the control of the control unit 14. The infrared light received by the infrared CCD device 10 is converted into an electric signal and output to the imaging circuit 11. The electric signal input to the imaging circuit 11 is subjected to predetermined processing such as noise removal, and then output to a display device or the like as a TV signal.

[0003]

DISCLOSURE OF THE INVENTION The present inventors first,
Observation was performed using a conventional type in which the above-mentioned filter was fixedly installed in the infrared light path. as a result,
Even when infrared light having a light quantity exceeding the saturation light quantity of the infrared CCD element is incident on the element, the light quantity is reduced by the filter, so that observation having a light quantity exceeding the saturation light quantity of the element has become possible. However, when observing an object with a small amount of light from the object, the amount of infrared light incident on the infrared CCD element is reduced by the filter. There was a problem that observation of satellites became impossible.

In order to solve this problem, an apparatus using a removable filter as described in the above-mentioned prior art section has been proposed. This is because a filter is installed in the infrared light path only when the amount of infrared light exceeding the saturation light amount of the infrared CCD element is incident on the element, and when the light amount becomes small, the filter is removed from the light path and observation is performed. Was to do. This has made it possible to observe a wide range of objects, from those with high light intensity to those with low light intensity.

[0005] However, such a configuration using a filter causes a problem of an increase in the size of the apparatus, and the installation of the filter is troublesome. It is an object of the present invention to solve these problems and to provide an infrared imaging apparatus capable of easily observing infrared rays from a high light quantity to a low light quantity.

[0006]

Means for Solving the Problems The present inventors have proposed an infrared C
Focusing on the filter used as a means for adjusting the amount of infrared light incident on the CD element, without using a filter,
The amount of incident light is adjusted using a completely different means. Therefore, the present invention firstly provides an image pickup device that detects an infrared ray and outputs an electric signal, and an infrared image pickup apparatus that has an infrared optical system that focuses the infrared ray on the image pickup element. Infrared imaging device characterized by control by charge storage time (Claim 1) "
I will provide a. Secondly, in an infrared imaging device having an image sensor that detects an infrared ray and outputs an electric signal and an infrared optical system that focuses the infrared ray on the image sensor, a variable control that changes the charge accumulation time of the image sensor An infrared imaging device having a unit (Claim 2) "is provided. Third, in an infrared imaging apparatus having an imaging device that detects an infrared ray and outputs an electric signal and an infrared optical system that focuses the infrared light on the imaging device, a variable control that changes the charge accumulation time of the imaging device And an image forming means for forming an image based on a plurality of pieces of information obtained by setting a plurality of charge accumulation times by the variable control section. provide. 4th
`` An image sensor that detects infrared rays and outputs an electrical signal,
An infrared imaging apparatus having an infrared optical system that focuses the infrared light on the image sensor, a variable control unit that changes a charge accumulation time of the image sensor, and a delay circuit that delays an output signal from the image sensor by a predetermined amount. A comparison circuit that compares a saturation equivalent signal of the image sensor with an output signal from the image sensor, and a selection circuit that selects an output signal from the image sensor and an output signal from the delay circuit. Infrared imaging device (claim 4) "is provided. Fifth, “a correction circuit is provided for correcting unevenness in sensitivity of each pixel of the image sensor and uneven light reception on the image sensor surface of the optical system as a uniform output. Infrared imaging device element (claim 5). " Sixth, there is provided an infrared imaging device element according to claim 5, wherein the correction circuit performs correction in accordance with a shutter speed of an electronic shutter.

[0007]

FIG. 1 is a block diagram schematically showing the present embodiment. An embodiment of the present invention will be described below with reference to FIG. Infrared rays emitted from an object (not shown) are condensed by an infrared optical system (not shown), as in the related art, and imaged on an infrared CCD device 1 as an image pickup device.
This infrared light is photoelectrically converted and subjected to electric signal processing in the signal processing unit 2. In the present invention, the amount of light is adjusted by controlling the charge accumulation time using the function of an electronic shutter instead of the conventional filter. The control of the charge accumulation time is performed by a driving circuit of the infrared CCD element. For example, assuming an infrared imaging device in which the charge accumulation time of the infrared CCD element is 1/30 sec, the infrared CCD element is saturated when an amount of infrared light equivalent to 400K is observed. At this time, the charge accumulation time of the infrared CCD element is set to 1 / (30
× k) When the control is performed so as to be sec, the amount of charge generated by the infrared CCD element becomes 1 / k. Therefore, as compared with the case where the charge accumulation amount is not controlled, the controlled device can detect up to k times the amount of infrared radiation, thereby expanding the observation temperature range of the infrared imaging device.

Further, in this embodiment, the infrared CCD device 1
Is connected to the electronic shutter variable control unit 4 so that
An apparatus capable of continuously observing a wide temperature range from a high temperature region to a low temperature region can be obtained. For example, the charge storage time of the electronic shutter is set to 1 / (30 × k) as described above.
Suppose you set it to sec. In this case, as described above, the infrared CCD
The amount of saturation light of the infrared CCD element 1 can be apparently increased by k times as compared with the case where the element 1 is constantly received, so that a higher temperature region can be observed. However, the sensitivity in a low-temperature region where the amount of light from the target object is originally small becomes low. Therefore, in order to increase the sensitivity in the low temperature region, it is only necessary to lengthen the light receiving time of the infrared light received by the infrared CCD element 1. However, the amount of received light increases, and when the high temperature region is observed, the infrared light amount increases. The saturation light amount of the CCD element 1 is exceeded, and it becomes impossible to observe a high-temperature region. Therefore, the electronic shutter variable control unit 4 is provided to switch the charge accumulation time of the infrared CCD element by using the fact that the shutter speed can be switched by the electronic shutter function for each screen. That is, observation is performed by switching between the amount of received light suitable for observation in the high-temperature region and the amount of received light suitable for observation in the low-temperature region. In this embodiment, the light receiving time at the time of observation of the high temperature region is 1 / (30 × k)
c, The charge accumulation time at the time of observation in the low temperature region is set to 1/30 sec, and switching is performed for each screen.

The information on each of these screens is subjected to electrical signal processing by the signal processing unit 2. The output signal from the signal processing unit 2 is input to the delay circuit 3, the selection circuit 5, and the comparison circuit 6, respectively. For the sake of explanation, the signal obtained by controlling the charge accumulation time at 1 / (30 × k) sec is A (for high temperature region observation), and the signal obtained by controlling the light receiving time at 1/30 sec is B
(For low temperature region observation).

The signal A and the signal B are input to the delay circuit 3,
Each signal is delayed by one screen. In the present embodiment, the signal A is delayed by one screen with respect to the signal B, and is sent to the selection circuit 5 and the comparison circuit 6. Further, the comparison circuit 6 receives, from the electronic shutter variable control section 4, information on whether or not each signal is a screen driven by the electronic shutter (whether the electronic shutter is driven). When some of the pixels of one screen of the signal output from the signal processing unit 2, for example, the signal B, are saturated and the screen is a screen on which the electronic shutter is not driven, these pieces of information ( (Saturated pixel information) is sent from the comparison circuit to the selection circuit 5. Further, information on the received infrared light from the signal processing unit 2 (no delay processing) and information on the received infrared light delayed by one screen from the delay circuit 3 are input to the selection circuit 5. The selection circuit 5 to which the information is input performs the following selection based on the information on the presence or absence of driving of the electronic shutter input from the comparison circuit 6. [Selection 1-1] The electronic shutter drive presence / absence information input from the comparison circuit 6 is a screen with no drive. For pixels for which saturated pixel information is generated, the pixels are input from the delay circuit 3 to the selection circuit 5. Select the information [Selection 1-2] The information indicating whether or not the electronic shutter is driven, which is input from the comparison circuit 6, is a screen without driving, and a screen in which no saturated pixel information is generated is input to the selection circuit 5 from the signal processing unit 2. Selected information (a signal that has not been delayed). [Selection 2-1] This is a screen in which the electronic shutter drive presence / absence information input from the comparison circuit 6 is driven, and the pixels for which saturated pixel information has occurred are input from the signal processing unit 2 to the selection circuit 5. Select the information (undelayed signal). [Selection 2-2] A screen in which the electronic shutter drive presence / absence information input from the comparison circuit 6 is driven and a screen in which no saturated pixel information is generated is input from the delay circuit 3 to the selection circuit 5. Select the information

Such selection is performed by the selection circuit 5. As a result, the pixel signal in which the saturation signal has been generated is replaced with the pixel of the screen driven by the shutter, so that the screen is displayed in a wide temperature range from the high temperature part to the low temperature part. As described above, in the present invention, the shutter speed of the electronic shutter can be changed according to the temperature of the object to be observed. It is also possible to set a plurality of shutter speeds and combine information obtained at these shutter speeds.

In the present invention, the delay circuit, the comparison circuit, the selection circuit and the like as shown in FIG. 1 are referred to as image forming means. However, the present invention is not limited to this.
The charge accumulation time of the infrared CCD element, that is, the speed of the electronic shutter is controlled to a plurality of shutter speeds by a variable control unit, and information based on a plurality of light amounts obtained thereby can be processed to form at least one image. What is necessary is just to have a function. Further, the electronic shutter variable control unit has an electronic shutter selection circuit for determining a shutter speed and an electronic shutter drive circuit for driving the electronic shutter.

In the case where the amount of light received by the infrared CCD device is limited by using the electronic shutter function as in the present invention,
By increasing the non-uniformity of the obtained screen, it is possible to observe a wider temperature range with a good image.
The configuration and principle for achieving this will be described below. FIG. 2 is a block diagram of the present embodiment. Infrared light emitted from the observation target forms an image on an infrared CCD device serving as an imaging device via an infrared optical system.
The infrared rays imaged on the image sensor are photoelectrically converted into electric signals. The electric signal is passed through a correction circuit for removing gain (sensitivity) unevenness and offset unevenness for each pixel due to the image sensor so that the electric signal level in the screen becomes uniform when a uniform object is observed. Will be corrected. In the present embodiment, the output of the correction circuit is converted into an output proportional to the temperature via a predetermined voltage-temperature conversion circuit. The TV monitor may be a normal TV for processing such as adding a synchronization signal necessary for displaying an image on the TV monitor by a TV processing circuit that converts the output into a TV signal. The image sensor requires an image sensor driving circuit to output an image output. The electronic shutter selection circuit issues an instruction regarding switching of the selected electronic shutter to the shutter speed to the image sensor driving circuit, the correction circuit, and the voltage-temperature conversion circuit that drive the image sensor. In response to this instruction, each circuit receiving the instruction generates the following operation. In the image sensor driving circuit, a drive signal to the image sensor changes by switching the shutter speed. That is, the charge accumulation time is controlled according to the shutter speed.
In the voltage-temperature conversion circuit, the temperature range to be observed is different depending on the shutter speed, so the corresponding temperature conversion lookup table is switched. In the correction circuit, the correction of the change in the pixel unevenness of the image sensor and the change in the unevenness of the unnecessary radiation amount for each pixel are changed depending on the shutter speed.

FIG. 3 is a schematic diagram for explaining the concept of correction in an infrared imaging apparatus when an electronic shutter is not used. FIG. 3A shows the output of the image sensor when no correction is performed when a uniform target is observed. It can be seen from this that the gain (sensitivity) and offset of the image sensor output vary. FIG. 3B is obtained by correcting only the variation of each pixel of the image sensor. It can be seen that the output of the peripheral portion of the image is reduced due to the decrease in the amount of incident light at the periphery due to the optical system. The dotted line in the figure indicates unnecessary radiation from the optical system. FIG. 3C further shows a decrease in the peripheral light amount of FIG. 3B,
The unnecessary radiation of the optical system is corrected. Next, a case where the shutter speed is changed using an electronic shutter will be described with reference to FIG.

When an electronic shutter is used, correction for solving the following problems is required. FIG.
It is a figure showing the concept for explaining these. FIG. 4A
Indicates a normal image sensor output when only the self-radiation (unnecessary radiation) from the infrared optical system is obtained when the temperature of the observation target is sufficiently low. For systems where aperture matching is not perfect, there is thus unwanted radiation of the optical system. As shown in FIG. 4B, when the shutter speed is faster than the normal case, the unnecessary radiation is reduced in the same manner as the incidence from the observation target (solid line). Therefore, if the shutter speed is changed during the correction in FIG. 3, the correction will be shifted by the difference between the correction amounts shown in FIG. 4B. It is necessary to correct the offset amount in the spatial direction according to the shutter speed. The gain also needs to be corrected for a decrease in the peripheral light amount. In particular, regarding the offset, the addition of hardware can be reduced by considering the following relationship. The output of the unwanted radiation decreases in proportion to the shutter speed.

FIG. 5 shows an embodiment of the correction circuit. In FIG. 5, the image sensor unevenness correction circuit corrects variations of the image sensor for each pixel. The optical system offset unevenness correction circuit is a circuit that corrects unnecessary radiation caused by the optical system. The optical system gain non-uniformity correction circuit is a circuit that corrects a light amount change in a spatial direction caused by the optical system. In the optical system offset unevenness correction circuit, for example, when the shutter speed is 1/500 sec (1/500) / (1) with respect to the normal state (the shutter speed of the electronic shutter is 1/60 sec).
/ 60), the unnecessary radiation component is reduced. Therefore, as shown in FIG. 5B, the shutter speed difference is added to the normal correction circuit, and the addition calculation of (selected electronic shutter speed / reference electronic shutter speed−1) × (correction amount at reference electronic shutter speed) is performed in the correction circuit. Is performed, it is possible to correct the change in the optical system offset due to the change in the shutter speed.

Although the variable control section of the electronic shutter shown in FIG. 1 is not described in the embodiment of FIG. 2, it is of course possible to install the variable section in the image pickup device. Further, the voltage-temperature conversion circuit shown in FIG. 2 is not always necessary, and may be arbitrarily provided depending on the purpose of use and conditions.

[0018]

As described above, according to the infrared imaging apparatus of the present invention, when observing a high-temperature object, it is possible to observe a high-temperature area without using a conventional ND filter. Since it is not necessary to mount the filter depending on the temperature of the object, continuous observation is possible, and the trouble of the observation is reduced. Further, since the ND filter is not used, the number of components is reduced and the size of the apparatus can be reduced. Also,
Since an expensive ND filter is not used, manufacturing costs can be reduced. Further, since the shutter speed of the electronic shutter can be arbitrarily adjusted by the variable control means, there is no need to prepare a plurality of ND filters. Further, by adjusting the shutter speed and combining the obtained information, it is possible to observe a wide temperature range from a high temperature to a low temperature. Further, by providing the correction circuit, unnecessary radiation from the infrared optical system can be reduced, so that the effective observation range can be widened. And
With a configuration in which the voltage-temperature favorable table is switched for each electronic shutter speed, and a configuration in which the correction amount is switched for each pixel in the spatial direction and for each pixel, it is possible to eliminate image unevenness that occurs when the electronic shutter is changed.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of an infrared imaging device having a correction circuit according to the present invention.

FIG. 3 is a conceptual diagram illustrating image correction in a general infrared imaging device.

FIG. 4 is a conceptual diagram showing a problem when a shutter speed is changed in an infrared imaging device using an electronic shutter.

FIG. 5 is a block diagram showing an example of a correction circuit according to the present invention.

FIG. 6 is a schematic diagram of a conventional infrared imaging device.

FIG. 7 is a schematic diagram of a conventional infrared imaging device.

[Explanation of symbols]

 8. Infrared optical system 9 ... ND filter 10. Infrared CCD element 11. Imaging circuit 12. Observation target 13. Motor 14. Control unit

Claims (6)

[Claims] 1. An infrared imaging apparatus comprising: an imaging device that detects an infrared ray and outputs an electric signal; and an infrared imaging system that focuses the infrared ray on the imaging device. An infrared imaging device characterized by being controlled by: 2. An infrared imaging apparatus comprising: an imaging device that detects an infrared ray to output an electric signal; and an infrared imaging system that focuses the infrared light on the imaging device. An infrared imaging device having a control unit. 3. An infrared imaging apparatus having an image sensor for detecting an infrared ray and outputting an electric signal and an infrared optical system for condensing the infrared ray on the image sensor. An infrared imaging apparatus comprising: a control unit; and an image forming unit that forms an image based on a plurality of pieces of information obtained by setting a plurality of charge accumulation times by the variable control unit. 4. An infrared imaging apparatus having an image sensor for detecting an infrared ray and outputting an electric signal and an infrared optical system for condensing the infrared ray on the image sensor, wherein the charge storage time of the image sensor is changed. A control unit, a delay circuit that delays an output signal from the image sensor by a predetermined amount, a comparison circuit that compares a saturation equivalent signal of the image sensor with an output signal from the image sensor, and an output from the image sensor. An infrared imaging device comprising a selection circuit for selecting a signal and an output signal from the delay circuit. 5. A correction circuit for correcting unevenness in sensitivity of each pixel of the image sensor and uneven light reception on the image sensor surface of the optical system as a uniform output. 5. The infrared imaging device element according to 4. 6. The correction circuit according to claim 5, wherein said correction circuit performs correction in accordance with a shutter speed of an electronic shutter.
An infrared imaging device element as described in the above.