JPH06253217A - Image pickup device - Google Patents

Abstract

PURPOSE:To attain real time elimination of noise by providing a nonreflection face on one face of a polygon mirror being a component of an infrared ray image pickup device, acquiring an output as fixed pattern noise when an image pickup element is opposite to the face, calculating the noise and an image pickup signal obtained from the element so as to eliminate the noise. CONSTITUTION:When an infrared ray is made incident from an object through an image pickup lens 12 of an optical system 1 and collimated by a collimator lens 13, the infrared ray is reflected in a reflecting face of a driven polygon mirror 14 and the image is formed on an infrared ray image pickup element 11 by an image forming lens 15 and it is used for an image pickup signal and it is converted into an electric signal. Since one side of the mirror 14 is formed as a non-reflecting face 14a, the element 11 is opposite to the non-reflecting face 14a during one rotation. Furthermore, when the light reflected in the reflection face is picked up by the element 11, since no synchronizing signal is outputted from a timing controller 2, it is inputted to an arithmetic operation circuit 7 as an image pickup signal and fixed pattern noise is cancelled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device such as an infrared ray image pickup device using an image pickup device, and more particularly to an image pickup device in which sensitivity variations and dark current variations of the image pickup element which cause fixed pattern noise in the image pickup element are corrected. .

[0002]

2. Description of the Related Art Conventionally, in an image pickup apparatus using a solid-state image pickup element or the like, fixed pattern noise is generated due to sensitivity variations and dark current variations due to individual differences. In particular, in an image pickup apparatus in which light of an image pickup target is imaged on an image pickup element by using a scanning optical system such as a polygon mirror, and a scanning signal is obtained from the image pickup element, a fixed pattern is formed in the scanning direction on the screen of the image pickup element. Noise is generated, which causes deterioration of imaging quality. As a method for correcting this fixed pattern noise, various proposals have hitherto been made, for example, Japanese Patent Application Laid-Open No. 2-7.
There is one described in Japanese Patent No. 2773. The device disclosed in this publication projects light of different luminance light sources onto the solid-state image pickup device in advance to obtain its output, and stores this output in the memory. Then, when an image is picked up by the solid-state image pickup device, an operation is performed using the output and the stored output to cancel the fixed pattern noise.

Further, in the infrared image pickup device using infrared rays, a fixed pattern noise acquisition device having a uniform radiation temperature over the entire radiation surface is provided in place of the different brightness light source of the above-mentioned publication, and this device is used for image pickup by the infrared image pickup device. Place it so that it covers the field of view. And by imaging this device,
The output signal from the infrared imaging device at this time is stored in the memory as fixed pattern noise. This fixed pattern noise data is subtracted from the output signal from the infrared image pickup device when an object of interest is imaged to correct sensitivity variations and dark current variations between the image pickup elements.

[0004]

In such a conventional correction of fixed pattern noise, it is necessary to acquire fixed pattern noise data in advance and store it in a memory before imaging. Therefore, in order to deal with sensitivity variations and dark current variations due to changes in characteristics of the image sensor over time, it is necessary to acquire and store data on a regular basis, and when this is omitted, fixed pattern noise is effective. It cannot be removed. In addition, imaging must be interrupted when acquiring this data. Therefore,
There is a problem that the management of the imaging device becomes complicated.

Further, in the infrared image pickup device as described above, since a device having a uniform radiation temperature on the entire radiation surface is required, the device other than the original image pickup device must be always secured. Further, at the time of acquiring the fixed pattern noise, it is necessary to install a device for acquiring the fixed pattern noise so as to cover the field of view of the imaging device, and infrared imaging is temporarily interrupted. It is an object of the present invention to provide an imaging device that constantly acquires fixed pattern noise and realizes highly accurate removal of fixed pattern noise, while not interrupting imaging.

[0006]

The present invention is configured as a scanning type image pickup apparatus which reflects light from a subject by a polygon mirror which is driven to rotate and forms an image on an image pickup element.
One of the plurality of reflecting surfaces of the polygon mirror is configured as a non-reflective surface, and means for acquiring the output of the image sensor when the image sensor faces the non-reflective surface as fixed pattern noise, and the acquired fixed A means for calculating pattern noise and an image pickup signal obtained from the image pickup device to remove fixed pattern noise from the image pickup signal. For example, a memory circuit that stores fixed pattern noise output from the image sensor, and an arithmetic circuit that performs calculation of the image signal from the image sensor and the fixed pattern noise stored in the memory circuit to remove the fixed pattern noise. , A timing controller that outputs a synchronization signal when the image sensor faces the non-reflective surface of the polygon mirror, and normally when the output of the image sensor is input to the arithmetic circuit and the synchronization signal is input from the timing controller And a switching circuit for switching the output of the image pickup device to the memory circuit as fixed pattern noise. Further, it is preferable that an offset correction circuit that performs offset correction of an output signal from the image pickup device that is input to or output as fixed pattern noise from the image pickup device is provided at a front stage or a rear stage of the memory circuit. The present invention is particularly configured as an infrared imaging device that captures infrared light from a subject by using an infrared imaging element as an imaging element, and the non-reflective surface of the polygon mirror is configured as a uniform temperature surface having a reflectance of 0%. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment in which the present invention is applied to an infrared imaging device. In the figure, an optical system 1 of the infrared imaging device is configured as a rotary scanning optical system using an infrared imaging device 11 composed of a large number of solid-state imaging devices, and an imaging lens 12 for imaging infrared light from a subject. A collimator lens 13 for converting the imaged light into parallel light, a polygon mirror 14 for sequentially reflecting the parallel light with rotation on a plurality of reflecting surfaces, and an image of the reflected light from the polygon mirror 14 on the infrared imaging element 11. The image forming lens 15 is provided. Here, the polygon mirror 14 is configured as a polygonal cylinder having a plurality of reflecting surfaces on its peripheral surface, which is an octagonal rotating mirror in this case, and one of the surfaces has a reflectance of 0%. As shown in FIG.
And is configured to be rotated in a fixed direction by a drive source (not shown).

A timing controller 2 is connected to the polygon mirror 14 so that the non-reflective surface 14a of the polygon mirror 14 is positioned to face the infrared image pickup element 11, that is, the polygon mirror 1 is attached to the infrared image pickup element 11.
A signal synchronized with the timing at which the infrared light from the subject is not imaged is output via 4. In addition, the infrared image pickup device 11 receives the image pickup signal output from the image pickup device A
An A / D converter 3 for D / D conversion is connected. This A / D
The output of the converter 3 is connected to the offset correction circuit 5, the memory circuit 6, and the arithmetic circuit 7 via the switching circuit 4, respectively. The switching circuit 4 performs an operation of selectively switching the image pickup signal digitized by the signal from the timing controller 2 between the offset correction circuit 5, the memory circuit 6 and the arithmetic circuit 7. The offset correction circuit 5 removes the offset component from the fixed pattern noise data as described later, and the memory circuit 6 stores the obtained fixed pattern noise data.
The arithmetic circuit 7 also performs correction subtraction such as subtraction of fixed pattern noise from the image pickup signal, and outputs the obtained image pickup signal to the output terminal 8.

Next, the operation will be described. When infrared light from the subject enters through the imaging lens 12 of the optical system 1 and is collimated by the collimator lens 13, the infrared light is reflected by the reflecting surface of the polygon mirror 14 that is rotationally driven. Then, the image is formed on the infrared imaging element 11 by the imaging lens 15, and is converted into an electric signal as an imaging signal by the imaging element 11. Since one surface of the polygon mirror 14 is configured as a non-reflection surface 14a having a reflectance of 0%, when the polygon mirror 14 makes one rotation, the infrared imaging element 11 is opposed to the non-reflection surface 14a in a part of its rotation cycle. Will be. Since the surface temperature of the non-reflective surface 14a is almost uniform and this surface is imaged on all the infrared imaging elements 11, the output signal from each imaging element 11 is an output according to its sensitivity variation and dark current variation. Become. This output signal is A / D converted in the A / D converter 3 to be a digital signal, which is input to the switching circuit 4.

As the polygon mirror 14 rotates, the non-reflective surface 14a of the polygon mirror 14 is imaged by the infrared imaging device 11 and at the same time, the timing controller 2 outputs a synchronizing signal, so that the switching circuit 4 operates by the synchronizing signal. Then, the switches are switched to the offset correction circuit 5 and the memory circuit 6 side. Therefore, the digital signal output from the infrared imaging device 11 and input to the switching circuit 4 is obtained as fixed pattern noise data by removing the offset by the offset correction circuit 5, and this is input to the memory circuit 6. Will be remembered.

Further, when the infrared image pickup device 11 picks up the image of the infrared light from the subject which is reflected by the reflecting surface of the polygon mirror 14, the timing controller 2 does not output a synchronizing signal, so that it is used as an image pickup signal. The digital signal is input to the arithmetic circuit 7 through the switching circuit 4. Then, in the arithmetic circuit 7, the fixed pattern noise stored in the memory circuit 6 is read out, and the imaging signal and the fixed pattern noise are subtracted. By this subtraction, the fixed pattern noise due to the sensitivity variation and the dark current variation of the infrared image pickup device 11 included in the image pickup signal is offset, and the corrected pattern data is output.

FIG. 2 shows an image pickup signal from the infrared ray image pickup device 11 in one rotation of the octagonal polygon mirror 14 which is composed of seven reflection surfaces and one nonreflection surface on the peripheral surface as described above. FIG. 9 is a diagram showing the characteristics of the output signals S1 to S7 from the reflecting surfaces 1 to 7 among the eight surfaces 0 to 8, while signals corresponding to the intensity of infrared light from the subject are obtained, The signal S0 from the surface does not include a signal due to infrared light from the subject, and a signal corresponding to the sensitivity variation and the dark current variation of the infrared imaging element 11 is obtained.

FIG. 3 is a schematic diagram showing an example of a method for correcting sensitivity variations and dark current variations of the infrared image pickup device 11 in the arithmetic circuit 7. When the infrared imaging device 11 faces the non-reflection surface 14a of the polygon mirror 14,
Since an object having a uniform temperature is seen, the output signal from the infrared image pickup device 11 must be constant. In reality, there are variations in sensitivity and variations in dark current due to individual differences in the infrared detection element 11, so the output is not constant,
As a result, fixed pattern noise data is obtained from the A / D converted digital signal as shown in FIG. When the offset amount is removed in the offset correction circuit 5 by using the minimum value of the fixed pattern noise as the offset amount, FIG.
It becomes like (b). Next, since the signal output from the infrared imaging element 11 by imaging the infrared light from the subject reflected by the reflecting surface of the polygon mirror 14 includes sensitivity variations and dark current variations, FIG. become that way. Then, this signal is sent to the arithmetic circuit 7 in FIG.
By performing subtraction with the fixed pattern noise of (b), the fixed pattern noise is removed, and the corrected signal of FIG. 3 (d) can be obtained.

Therefore, in this image pickup apparatus, the fixed pattern noise can be obtained every one rotation of the polygon mirror 14, and the fixed pattern noise can be removed from the obtained image pickup signal of the subject. Therefore, it is possible to remove fixed pattern noise in real time, which corresponds to fluctuations in sensitivity, dark current fluctuations, and the like due to aging of the image sensor 11, and to perform infrared imaging of a subject with fixed pattern noise removed with high accuracy. Can be realized. Further, since the fixed pattern noise is acquired during the image pickup, a special device for obtaining the fixed pattern noise is unnecessary, and the work for acquiring the fixed pattern noise in advance before the image pickup is not necessary. There is also no need to interrupt imaging to capture noise. Although the offset correction circuit 5 is provided in the preceding stage of the memory circuit 6 in the above-mentioned embodiment, this is for subtracting the predetermined level value from the fixed pattern noise, so that it may be provided in the subsequent stage of the memory circuit 6. Well, in some cases it can be omitted. Further, although the above-mentioned embodiment shows an example in which the present invention is applied to an infrared imaging device, the present invention can be similarly applied to an imaging device using normal visible light. Further, the switching circuit 4 is configured to select the synchronizing signal from the timing controller 2 and perform switching operation for each of a plurality of synchronizing signals, thereby acquiring fixed pattern noise for each plurality of rotations of the polygon mirror 14 and storing the fixed pattern noise. It may be stored in the circuit 6.

[0015]

As described above, according to the present invention, a non-reflective surface is provided on one surface of a polygon mirror, and the output of the image sensor when the image sensor faces the non-reflective surface is acquired as fixed pattern noise. Since the fixed pattern noise and the image pickup signal obtained from the image pickup device are calculated to remove the fixed pattern noise from the image pickup signal, the fixed pattern noise can be removed in real time. The step of acquiring the fixed pattern noise prior to the above is not necessary, and highly accurate noise removal that copes with the fluctuation of the fixed pattern noise due to the change over time can be realized. Further, since a special device for fixed pattern noise acquisition is not required, it is possible to remove fixed pattern noise with a simple configuration, and further, without interrupting the imaging.
There is an effect that fixed pattern noise in the image sensor can be removed at any time. Further, the fixed pattern noise output from the image pickup device is stored in the memory circuit, and the fixed pattern noise is removed by calculating the image pickup signal from the image pickup device and the fixed pattern noise stored in the memory circuit in the arithmetic circuit. In addition, when storing the fixed pattern noise in the memory circuit, the switching circuit is switched based on the synchronization signal output from the timing controller when the image pickup device faces the non-reflective surface of the polygon mirror, and the output of the image pickup device is output. Is input to the memory circuit as fixed pattern noise, the fixed pattern noise can be automatically acquired in real time. Furthermore, by providing an offset correction circuit that performs offset correction of fixed pattern noise in the preceding stage or the subsequent stage of the memory circuit, it is possible to remove fixed pattern noise using net fixed pattern noise with no offset, A highly accurate image pickup signal can be obtained from the arithmetic circuit.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment in which the present invention is applied to an infrared imaging device.

FIG. 2 is a waveform diagram of an image pickup signal obtained from the image pickup device of FIG.

FIG. 3 is a schematic diagram for explaining a method of correcting fixed pattern noise for an image pickup signal.

[Explanation of symbols]

 1 Optical System 11 Infrared Imaging Element 12 Imaging Lens 14 Polygon Mirror 14a Non-Reflecting Surface 2 Timing Controller 3 A / D Converter 4 Switching Circuit 5 Offset Correction Circuit 6 Memory Circuit 7 Arithmetic Circuit

Claims (4)

[Claims] 1. A scanning type image pickup apparatus for reflecting light from a subject on a rotationally driven polygon mirror to form an image on an image pickup device, wherein one of a plurality of reflecting surfaces of the polygon mirror is a non-reflection surface. A means for acquiring the output of the image sensor as fixed pattern noise when the image sensor faces the non-reflection surface, and the acquired fixed pattern noise and the image signal obtained from the image sensor. And a means for removing fixed pattern noise from the image pickup signal. 2. A memory circuit that stores fixed pattern noise output from an image pickup device, and an operation of an image pickup signal from the image pickup device and the fixed pattern noise stored in the memory circuit to remove the fixed pattern noise. Arithmetic circuit,
A timing controller that outputs a synchronization signal when the image sensor faces the non-reflective surface of the polygon mirror, and normally when the output of the image sensor is input to the arithmetic circuit and the synchronization signal is input from the timing controller. The image pickup apparatus according to claim 1, further comprising a switching circuit that switches the output of the image pickup element to the memory circuit as fixed pattern noise. 3. The memory circuit is provided before or after the memory circuit,
The image pickup apparatus according to claim 2, further comprising an offset correction circuit that performs offset correction of an output signal from the image pickup device that is input or output as fixed pattern noise to the memory circuit. 4. An infrared imaging device for imaging infrared light from a subject using an infrared imaging device as an imaging device, wherein the non-reflective surface of the polygon mirror is a uniform temperature surface having a reflectance of 0%. The image pickup apparatus according to claim 1, wherein