JPH0775023A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To automatically eliminate intra-screen luminance ununiformity due to the characteristic difference of respective divided areas by using the output signals of image-formed picture elements of a slit opening arranged on a first image forming surface for correction. CONSTITUTION:An optical system is defined to be a relay type optical system and a slit-like opening part is provided on the first image forming surface. Since the slit opening part is present, the projection images 31 of the slit opening part are present other than the images of incident infrared rays on the image forming screen. The projection images 31 overlap with upper and lower parts among the non-display area 30 of a photodetecting element and thus, the radiated infrared rays of the slit opening part are photoelectrically converted and outputted for the parts. By providing a screen luminance correction part after offset correction and controlling the signals of the projected picture elements of the slit opening so as to be '0' at all times, even when the fluctuation of characteristics for the respective divided areas of the photodetecting element is present after the offset correction, luminance fluctuation for the respective areas due to the fluctuation can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device of a type in which a light receiving region of a photodetector is divided into a plurality of regions and read in parallel at the same time.

[0002]

2. Description of the Related Art An infrared imaging device will be described as a conventional example of a solid-state imaging device. FIG. 5 is a block diagram showing an example of a conventional infrared image pickup device.
Is an optical system, 3 is a photodetector, 4 is a first time series output signal, 5 is a second time series output signal, 6 is a first preamplifier, 7 is a second preamplifier, and 8 is a first A. / D converter, 9 is a second A / D converter, 10 is a first offset correction unit, 11 is a second offset correction unit, 12 is a screen synthesis unit, 13 is a video D / A converter, and 14 is for display. It is a monitor.

FIG. 6 shows a two-dimensional interline CCD (Charge Co) used in a conventional infrared imaging device or the like.
FIG. 3 is a schematic view of an array device of an up-loaded device, where 15 is a first divided region, 16 is a second divided region,
Reference numeral 17 is a first horizontal CCD (hereinafter referred to as HCCD), 18 is a second HCCD, 19 is a first floating diffusion amplifier (hereinafter referred to as FDA),
Reference numeral 20 is a second FDA, and 21 is a vertical scanning circuit.

In the conventional infrared detecting element, it is necessary to cool the element to about 80K, and if a high-speed read clock (hereinafter referred to as CLK) frequency is used, the transfer efficiency of the output signal is lowered due to the temperature characteristic of the CCD, and the image The resolution deteriorates. On the other hand, considering compatibility with external devices, the signal readout method is NTSC (National Television).
Ion System Committee) is suitable, and the frame rate at this time is 30H.
z. Therefore, in the case of driving a detection element having a large number of pixels in compliance with NTSC, a method of dividing the light receiving area as shown in FIG. 5 and simultaneously reading in parallel is adopted in order to avoid speeding up of the read CLK frequency.

Next, an example of the operation of the conventional infrared image pickup device will be described with reference to FIGS. First, regarding the operation of the photo-detecting element 3, the divided areas 15 and 16 having the dedicated HCCDs 17 and 18 and the dedicated FDAs 19 and 20, respectively, perform the reading operation simultaneously in parallel. That is, the vertical scanning circuit 21 causes the signal charges in one stage of the divided areas 15 and 16 to be transferred to the HCCDs 17 and 18 by the vertical CCD.
Then, it is read out as time series signals 4 and 5 from the FDA 19 and 20 by the CCD operation.

The time-series output signals 4 and 5 from the photo-detecting element 3 are analog data signals, which are amplified by the preamplifiers 6 and 7 and then converted into digital signals by the A / D converters 9 and 10. After that, the offset correction units 10 and 11 perform correction to evenly adjust the variations of the offsets of the respective pixels, and then the screen synthesis unit 12 synthesizes the signals of the respective regions and displays them on the monitor 14 through the video D / A 13. .

An example of the offset correction at this time will be described with reference to FIG. In FIG. 7, 22 is a first changeover switch for offset correction, 23 is a frame memory, 24 is a division circuit, and 36 is a second changeover switch for offset correction. When taking offset correction data, the switch 22 is connected to the contact b and the switch 36 is opened. At this time, the input signal is integrated n times and stored in the frame memory 23. The number of integration times n is determined by the size of the output signal and the capacity of the frame memory 23. After storing the data, the switch 22 is connected to the contact a and the switch 36 is closed. In this way, offset correction is performed by subtracting the offset signal from the frame memory 23 for each pixel signal. However, when acquiring offset data, it is necessary to capture an image that is uniform in temperature across all pixels, and additional work such as preparing a surface blackbody or covering the front of the imaging device with a cap is required. Become.

[0008]

The conventional infrared image pickup device is constructed as described above, but since the HCCD and FDA are independently given to each divided area, its characteristics (HCCD transfer efficiency, FDA When the output characteristics, etc.) change with time, a difference occurs in the output voltage for each divided area. This appears as a difference in brightness on the screen and causes an unnatural image pickup result. In order to avoid this phenomenon, offset correction must be performed intricately, and correction data must be obtained every time, so the above-mentioned additional work is required, which is troublesome.

The present invention has been made in order to solve such a problem, and can automatically eliminate the uneven brightness in the screen due to the characteristic difference of each divided area, and perform the offset correction. Even in such a case, it is an object of the present invention to reduce the work required for obtaining the correction data and to easily obtain the correction data.

[0010]

In a solid-state image pickup device according to the present invention, an optical system thereof is a relay type optical system, a slit-shaped opening is provided on a first image forming surface thereof, and a pixel selector and a signal addition unit are provided. A screen brightness difference correction unit having a circuit or the like as a constituent element is provided.

Further, the solid-state image pickup device according to the present invention is provided with a horizontal stage brightness comparing section for sequentially adding and comparing screen signals for each horizontal stage of the photodetecting element, and finely adjusting the position of the slit opening by the output thereof. This is provided with a drive motor capable of performing.

Further, the solid-state image pickup device according to the present invention is provided with a drive motor capable of opening and closing the slit opening portion by a control signal from the outside.

Further, the solid-state image pickup device according to the present invention is
A temperature control unit that can freely set the temperature of the slit opening is provided.

[0014]

According to the present invention, the slit openings arranged on the first image forming surface form images on the upper and lower pixel rows outside the effective display area of the photodetector on the second image forming surface (focal plane). The screen brightness difference correction unit calculates an average value of the output signals of the pixels formed by the slit apertures, and subtracts this average value from the image signal of the effective display area as a screen brightness difference correction signal.

Further, the horizontal stage luminance comparing section compares the image signals added for each horizontal stage, and the drive signal output from the horizontal stage compares the drive motor to finely adjust the position of the slit opening.

Further, the drive motor opens and closes the slit opening by a control signal from the outside.

Further, the temperature control section controls the temperature of the slit opening based on a temperature signal given from the outside.

[0018]

EXAMPLES Example 1. FIG. 1 is a block diagram of an infrared imaging device showing an embodiment of the present invention, in which 25 is a relay optical system, 26 is a slit opening, 27 is a drive motor, and 2 is a drive motor.
Reference numeral 8 is a first screen brightness difference correction unit, 29 is a second screen brightness difference correction unit, 37 is a first image plane, 38 is a second image plane (focal plane), and 39 is horizontal stage brightness determination. Reference numeral 40 is a portion for controlling opening / closing of the drive motor from the outside, and reference numeral 41 is a temperature control portion.

FIG. 2 is a diagram showing an image pickup state of a photodetector of an infrared ray image pickup device according to an embodiment of the present invention.
Is a pixel area (hereinafter referred to as a non-display area) other than the area (effective display area) displayed on the screen in the light receiving area of the element, and 31 is an image formed on the light detection element by the relay type optical system 25. It is a projected image of a slit opening.

Next, the operation of the infrared image pickup device in the first embodiment will be described with reference to FIGS. The incident infrared ray 1 forms an image on the image forming surface 37 once by the relay type optical system 25 and then re-images on the image forming surface 38. However, since the slit opening 26 exists on the image forming surface 37, the infrared ray 1 is not formed. On the image plane 38, a projected image 31 of the slit opening 26 exists in addition to the image of the incident infrared ray 1. This projected image 31 overlaps the upper and lower parts of the non-display area 30 of the photodetector element 3, and thus this part photoelectrically converts the infrared radiation emitted from the slit opening 26 and outputs it. The projected image 31 of this slit opening 26
Must faithfully reflect the temperature condition of the slit opening 26 itself, and therefore the emissivity of the slit opening 26 must be approximately 1.

The time series signal 4 output from the photodetector 3
And 5 are amplified by preamplifiers 6 and 7, and then A / D
The signals are converted into digital signals by the converters 8 and 9, and are corrected by the offset correction units 10 and 11, and the screen brightness difference correction units 28 and 29, and then the signals of the respective regions are combined by the screen combining unit 12 to generate the video D / Monitor 1 through A13
Display in 4.

Details of the screen brightness difference correction at this time will be described with reference to FIG. In FIG. 3, reference numeral 32 is a pixel selector, 33 is a changeover switch for screen brightness difference correction, 34 is a signal addition circuit for pixels in the non-display area, and 35 is a division circuit. The offset-corrected time-series signal is the changeover switch 3
Enter in 3. The changeover switch 33 is normally connected to the contact a. The pixel selector 32 controls the changeover switch 33, and selects only the signal of the non-display area where the slit opening 26 is projected among the time series signals. At this time, the changeover switch 33 is connected to the contact b, and the addition circuit 3
At 4, the N pixels are added. Here, N is the non-display area 3
It is the number of pixels used for addition (the slit opening 26 is projected) out of 0. If the characteristics of the photodetector 3 are the same as when the offset correction data was acquired, the adder circuit 34
Is 0, but if there is a variation in the characteristic, the variation is reflected in the output from the adding circuit 34. Therefore, this output is returned to the fluctuation of one pixel by the division circuit 35 and subtracted from the time series signal from the offset correction unit. The signal thus obtained becomes a signal obtained by removing the variation in the characteristic for each divided area, and is sent to the screen synthesis unit 12.

On the other hand, the geometrical position of the slit opening 26 projected on the photo-detecting element 3 may change due to a change in environmental temperature or a disturbance such as vibration. Due to this variation, the slit opening 26 is projected in the effective display area, or the number of projected pixels (N pixels) required for correction is reduced, which causes problems. In order to solve this problem, a horizontal stage brightness comparing section 39 is provided, and its operation will be described with reference to FIG. In FIG. 4, 42 is the first addition circuit, 4
3 is a second adder circuit, 44 is a second adder circuit, and 45 is a comparison / determination unit. The adder circuits 42 and 43 sequentially add the image signals for one stage according to the horizontal synchronizing signal of the image. The added signals are further added by the adding circuit 44 and input to the comparison / determination unit 45. The comparison / determination unit 45 compares the addition signal of the currently input stage with the addition signal of the immediately preceding stage, and outputs a drive signal to the drive motor 27. For example, if there are 10 non-display areas above the photodetector and 5 of them are pixel areas used for addition for correction,
When the projected pixel area of the slit opening is 10 steps or more, the slit opening is projected on the effective display area, and when it is 5 steps or less, an error occurs in the added value of the image signals in the screen brightness difference correction section. . Therefore, the comparison / judgment unit 45 counts the number of horizontal stages of the element with the horizontal synchronizing signal, and if there is a difference of a certain value or more in the added signal to be compared within 5 stages, the comparison is performed even in the direction of closing the slit opening even for 10 stages or more. If there is no difference of a certain value or more in the added signal, a signal for slightly moving the drive motor in the direction of opening the slit opening is sent. In this way, the position of the slit opening 26 projected onto the photodetector 3 can be kept optimum.

Since the slit opening 26 has an emissivity of approximately 1, it can be used as an appropriate background temperature source. Therefore, for example, when the operator pushes a switch, a control signal is given to the drive motor 27, and the offset correction data can be acquired by closing the slit opening portion. And it can be performed easily.

Further, the temperature control device 4 is provided at the slit opening.
Since the temperature of the slit opening can be freely set from the outside by attaching 1, the offset correction data can be acquired at any temperature. As a result, even if there is a difference in temperature between the inside of the device and the imaging field of view, by adjusting the temperature of the slit opening to the temperature of the imaging field of view, it is possible to always obtain offset correction data based on the temperature of the imaging field of view. It will be possible.

Although the CCD is used for vertical / horizontal transfer in the above embodiment, similar effects can be obtained as long as charge reading is possible, such as a MOS switch system.

[0027]

As described above, according to the present invention, the slit openings are projected above and below the non-display area of the photodetector, and
Since the screen brightness correction unit is provided after the offset correction and the signal of the pixel on which the slit aperture is projected is controlled to be always 0, even if there is a change in the characteristics for each divided region of the photodetector after the offset correction, the change is caused by the change. It is possible to eliminate the brightness variation for each area.

Further, since the horizontal step brightness comparing section determines the number of horizontal steps in the pixel area in which the slit opening is projected, and the position of the slit opening can be finely adjusted by the drive motor according to the value. The positions of the slit opening and the photodetector can be kept optimum regardless of changes in the external environment.

Further, since the slit opening can be opened / closed by inputting a control signal from the outside, it is possible to obtain the offset correction data by closing the slit opening, which is a conventional additional work. It is possible to easily obtain a large amount of correction data.

Further, since the slit opening is connected to the temperature control section and its temperature can be arbitrarily set from the outside, it is possible to obtain offset correction data according to the temperature in the imaging visual field. Become.

[Brief description of drawings]

FIG. 1 is a block diagram of an infrared imaging device showing an embodiment of the present invention.

FIG. 2 is a diagram showing an image pickup state of a photodetecting element of an infrared image pickup device showing one embodiment of the present invention.

FIG. 3 is a block diagram of a screen brightness difference correction unit of the infrared imaging device showing the embodiment of the present invention.

FIG. 4 is a block diagram of a horizontal stage brightness comparison unit of the infrared imaging device according to the embodiment of the present invention.

FIG. 5 is a block diagram showing an example of a conventional infrared imaging device.

FIG. 6 is a schematic diagram of a two-dimensional interline CCD array photodetector used in a conventional infrared imaging device or the like.

FIG. 7 is a block diagram showing an example of an offset correction unit of a conventional infrared imaging device.

[Explanation of symbols]

1 Incident infrared ray 2 Optical system 3 Photodetector element 4 First time-series output signal 5 Second time-series output signal 6 First preamplifier 7 Second preamplifier 8 First A / D converter 9 Second A / D converter 10 1st offset correction part 11 2nd offset correction part 12 Screen composition part 13 Video D / A converter 14 Display monitor 15 1st division area 16 2nd division area 17 1st horizontal direction CCD ( HCCD) 18 Second HCCD 19 First floating diffusion amplifier (F
DA) 20 2nd FDA 21 Vertical scanning circuit 22 1st changeover switch for offset correction 23 Frame memory 24 Division circuit 25 Relay type optical system 26 Slit opening 27 Drive motor 28 1st screen brightness difference correction part 29th Second screen brightness difference correction unit 30 Pixel area (non-display area) other than the area displayed on the screen in the light receiving area of the element 31 Projected image of the slit opening formed on the photodetector by the relay optical system 32 Pixel selector 33 Change-over switch for screen brightness difference 34 Addition circuit for non-display area 35 Division circuit 36 Second change-over switch for offset correction 37 First image forming surface 38 Second image forming surface (focal surface) 39 Horizontal brightness comparison unit 40 Part for controlling opening / closing of drive motor from outside 41 Temperature control unit 42 First addition circuit 43 Second addition circuit 4 4 Third Adder Circuit 45 Comparison Judgment Unit

Claims (4)

[Claims] 1. A light receiving region of a photodetector is divided into a plurality of regions,
In a solid-state image pickup device of a system in which a preamplifier, an A / D converter, and an offset correction unit are independently arranged to read output signals simultaneously in parallel, in order to collect input light on a light receiving surface of the photodetector element, A relay type optical system, and a slit-shaped opening provided on the first image forming surface of the relay type optical system,
A pixel selector that selects a predetermined pixel signal from the input image signals, a changeover switch that performs a switching operation under the control of this pixel selector, an addition circuit that sequentially adds the image signals output from the offset correction unit, and an addition circuit A solid-state image pickup device, comprising: a screen luminance difference correction unit including a division circuit for dividing the calculated value by a predetermined value. 2. An adder circuit for adding input image signals in units of horizontal stages, and a signal for each horizontal stage added by this adder circuit is compared with an added signal of the previous horizontal stage, and the difference is calculated. And a drive motor for finely adjusting the position of the slit-shaped opening according to the output signal of the horizontal stage brightness comparison unit. The solid-state imaging device according to claim 1. 3. The solid-state imaging device according to claim 1, further comprising a drive motor that opens and closes the slit-shaped opening by a signal input from the outside. 4. A temperature control unit for arbitrarily setting the temperature of the slit-shaped opening portion.
Any one of the solid-state imaging devices.