JP2003163839A - Image input apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image input apparatus that can reduce an image capturing time so as to sufficiently increase the dynamic range, match the number of cumulative summing with the dynamic range of an object and a storage capacity of a storage medium, and eliminate the effect of noise due to a dark current of an imaging element. <P>SOLUTION: The image input apparatus for electronically picking up an image of the object and receiving the image, is provided with: the imaging element 1 that has an imaging area divided into a plurality of areas and can simultaneously output each image signal of a plurality of the area divisions; a cumulative summing means comprising a memory 6 and an adder 5 capable of accumulating the image signals of a plurality of the areas for a plurality of number of times respectively; and the memory 6 that stores the image signal accumulated by the cumulative summing means. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device, and more particularly to an image input device used in a digital camera or a scanner and capable of picking up an image of a subject having a wide dynamic range.

[0002]

2. Description of the Related Art In an image input device for electronically capturing a subject, the dynamic range of the subject is 80 dB.
However, the dynamic range of a solid-state image sensor such as a CCD image sensor is about 50 dB, and it is impossible to image a subject having a wider dynamic range while maintaining the dynamic range. . If the dynamic range is insufficient, for example, saturation of the image pickup device may occur in a high-luminance portion, or conversely, insufficient exposure may occur in a low-luminance portion. In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 05-115045 (Japanese Patent Application No.
No. 334508), the dynamic range is expanded by cumulatively adding image signals read from the image sensor to reduce random noise. In this case, when the cumulative addition number is N, the signal value is N times and the noise value is N ^1/2 times, so that the imaging dynamic range can be N ^1/2 times.

However, when the number of pixels of the image pickup device is increased by this method, it becomes impossible for a normal image pickup device to output an image signal in a short time, and the cumulative addition number during a predetermined subject image input time decreases. However, there is a problem that the dynamic range cannot be greatly expanded. In addition, when the image signals are cumulatively added by this method, if the cumulative addition number is determined in advance, the cumulative addition result exceeds the storage capacity of the image signal cumulative storage medium, resulting in an abnormal image signal. . Further, there is a problem that the image is deteriorated by noise due to the dark current of the image pickup device.

[0004]

As described above, when considering expanding the dynamic range by cumulative addition in the conventional image input device, the image signal cannot be output in a short time, and the cumulative addition number is sufficient. There was a problem that the dynamic range could not be greatly expanded without being taken.
There is also a problem that the information amount of the cumulative addition result exceeds the storage capacity of the image signal cumulative storage medium, and the obtained image signal becomes abnormal. Further, there is a problem that an image is deteriorated by noise due to a dark current of the image sensor. The present invention solves these problems by a relatively simple method to shorten the image capturing time and sufficiently increase the dynamic range, and adapt the cumulative addition number to the dynamic range of the subject and the storage capacity of the storage medium. Can
Another object is to realize an image input device capable of eliminating the influence of noise due to the dark current of the image sensor.

[0005]

In order to achieve the above object, the present invention provides an image input device for electronically picking up an image of a subject and having the image pickup region divided into a plurality of regions. Image pickup means having a solid-state image pickup element capable of simultaneously outputting the image signals of the plurality of areas, cumulative addition means for cumulatively adding the image signals of the plurality of areas read out from the image pickup element a plurality of times, and An image signal cumulative storage means for storing the image signal cumulatively added by the adding means. As a result, the image sensor outputs the image signals of a plurality of image capturing areas simultaneously,
Since the picked-up image signals are added and accumulated at the same time, the dynamic range of the picked-up image can be expanded and processed at high speed even if the number of pixels of the image pickup element is increased.

[0006]

DETAILED DESCRIPTION OF THE INVENTION An image input apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a control flowchart of the CPU in the configuration of FIG. In FIG. 1, reference numeral 1 is an image sensor,
Reference numeral 2 is an amplifier, reference numeral 3 is a signal processing circuit, and reference numeral 4 is A /
D converter, reference numeral 5 is an adder, reference numeral 6 is a memory, reference numeral 7 is a CPU, reference numeral 8 is an image pickup optical system, and reference numeral 9 is a shutter. The image input from the image pickup optical system 8 through the shutter 9 is electronically picked up by the image pickup device 1. This image sensor 1
Is, for example, a configuration in which n × n CCD elements are arranged in a matrix. The configuration of the image sensor 1 is shown in FIG. The image pickup device 1 is configured to be able to output independently from each of the n × n CCD devices shown in FIG.

The operation of this embodiment will be described with reference to the flowchart of FIG. When the flow chart starts in step 100, the upper limit MAX of the cumulative addition number is set to the specified value in step 101. The specified value is set from the outside, for example. Next, step 102.
The cumulative addition count CN is set to 0. The contents of the memory 6 are cleared to 0 here. In step 103, the image signal of each area output from each CCD element is amplified by the amplifier 2, processed by the signal processing circuit 3 such as clipping processing, and then digitalized by the A / D converter 4. The converted signal is accumulated and added to the signal stored in the memory 6 by the adder 5, and stored again in the memory 6. Then, in step 104, 1 is added to the cumulative addition number CN, and in step 105, the cumulative addition number CN is set to the upper limit value MA.
It is checked whether X has been reached. If the cumulative number of additions CN has not reached the upper limit value MAX, step 103
Then, the cumulative addition is repeated.

Such cumulative addition is performed a predetermined number of times, and when the cumulative addition number CN reaches the upper limit value MAX in step 105, the CPU 7 stops the cumulative addition in step 106,
The captured image signal is output in step 107, and step 10
The operation ends at 8. The cumulatively added signal is 1
The image signal has a wider dynamic range than the image signal obtained with the same subject input time. Further, the larger the number of cumulative additions, the wider the dynamic range.

In the present embodiment, since the image pickup device capable of simultaneously outputting the image pickup signals of a plurality of regions is used, it is possible to perform cumulative addition at a higher speed with the same clock as compared with the device having only a single output. . For example, in the case of an image pickup device capable of simultaneously outputting image signals of n × n regions, n ² times as many cumulative additions can be performed within the same time, so that the dynamic range can be further increased within the same capture time. Therefore, a better image signal can be output.

Next, FIG. 4 is a block diagram showing the configuration of another embodiment of the present invention, and FIG. 5 is a CPU having the configuration of FIG.
The control flowchart of is shown. In FIG. 4, reference numeral 1 is an image sensor, reference numeral 2 is an amplifier, reference numeral 3 is a signal processing circuit, reference numeral 4 is an A / D converter, reference numeral 5 is an adder, reference numeral 6 is a memory, reference numeral 7 is a CPU, reference numeral 8 is An imaging optical system, reference numeral 9 is a shutter, reference numeral 10 is an output switching circuit, and reference numeral 11 is a signal processing circuit.

The operation of this embodiment will be described with reference to the flow chart of FIG. When the flow chart starts in step 200, the upper limit MAX of the cumulative addition number is set to a specified value in step 201. Next, at step 102, the cumulative addition count CN is set to 0. The contents of the memory 6 are cleared to 0 here. In FIG. 4, the circuit up to the A / D converter 4 is the same as that of the embodiment of FIG.
The signal digitized by the D converter 4 is the output switching circuit 10
Entered in. The signal input to the output switching circuit 10 is
By switching in the output switching circuit 10, a signal immediately before the start of imaging is output to the signal processing circuit 11, and a signal during imaging is output to the adder 5.

In step 202, the signal processing circuit 11 outputs the maximum value S of the input image signal immediately before the start of image pickup to the CPU 7. Further, in step 203, the capacity C per pixel of the memory 6 is set. CPU7 is step 20
From the maximum value S of all the pixels of the image signal input in 4 and the capacity C per pixel of the memory 6, the upper limit value MS of the cumulative addition number is determined as MS = C / S, and in step 205, it is previously determined. The calculated upper limit value MS is compared with the predetermined upper limit value MAX of the cumulative addition number, and the calculated upper limit value M is set as the upper limit value M.
If it is smaller than AX, this upper limit value MS is determined in step 206.
Is the upper limit value MAX of the cumulative addition number, and otherwise, the predetermined cumulative addition number MAX is the upper limit value. Subsequent steps 207 to 213 are performed in the same manner as steps 102 to 108 in FIG. As a result, it is possible to prevent an abnormal image that occurs when the information amount of the image signal due to cumulative addition exceeds the upper limit value of the capacity per pixel in the memory 6.

FIG. 6 is a block diagram showing the configuration of another embodiment of the present invention, and FIG. 7 is a control flowchart when the fixed pattern noise of the image pickup device is created by the CPU in the configuration of FIG. The control flowchart during imaging is shown in Fig. 2.
It is the same as that of. In FIG. 6, reference numeral 1 is an image sensor, reference numeral 2 is an amplifier, reference numeral 3 is a signal processing circuit, reference numeral 4 is an A / D converter, reference numeral 5 is an adder, reference numeral 6 is a memory, reference numeral 7 is a CPU, reference numeral 8 is Reference numeral 9 is a shutter, reference numeral 10 is an output switching circuit, reference numeral 11 is a signal processing circuit, reference numeral 12 is a memory, reference numeral 13 is an adder, and reference numeral 14 is a subtractor.

The operation for creating fixed pattern noise according to the present embodiment will be described with reference to the flowchart of FIG. In the flowchart of FIG. 7, steps 300 to 306 are steps 100 to 10 in FIG.
The operation is the same as that up to 6. The image signal is output from the A / D converter 4 and input to the output switching circuit 10 in the same procedure as in the embodiment of FIG. When creating fixed pattern noise, the shutter 9 is closed immediately before the start of image capturing and immediately after the end of image capturing, and input of the subject image is stopped. In this case,
The image signals input to the output switching circuit 10 immediately before the start of image capture and immediately after the end of image capture are input to the adder 13 and are added and accumulated in the adder 13 and the memory 12. The signal additionally accumulated in the memory 12 while the shutter 9 is closed is so-called fixed pattern noise due to the dark current of the image sensor. After the above procedure is completed, in step 307, the CPU 7 outputs the cumulative addition signal when the shutter 9 is closed to the signal processing circuit 11. Then, the signal added and accumulated in the memory 12 is averaged for each pixel by the signal processing circuit 11, and is multiplied by the cumulative addition number during image pickup.

On the other hand, during image pickup, the shutter 9 is opened, and as shown in FIG.
The image signals are cumulatively added in the same procedure as in the embodiment. In the case of an image signal being captured, it is input to the adder 5,
The cumulatively added signals are stored in the memory 6. Then, the signal multiplied by the cumulative addition number in the signal processing circuit 11 is
It is subtracted from the signal cumulatively added to the memory 6 by being output to the subtractor 14 in synchronization with the image signal stored in the memory 6 in step 308. As a result, the subtractor 14
The signal after the subtraction is a signal obtained by removing the influence of fixed pattern noise due to the dark current of the image pickup device from the image pickup signal, and therefore, the image deterioration due to the fixed pattern noise can be suppressed. Here, the shutter 9 is used as the subject image input stopping means, but means such as controlling the image pickup element to electrically stop the subject image input may be used.

[0017]

As described above, the invention of claim 1 of the present invention comprises an image pickup device having an image pickup region divided into a plurality of regions and capable of simultaneously outputting image signals of the divided plural regions. The image pickup means is provided. This makes it possible to output the image pickup signal at high speed, prevent the output speed from decreasing due to the increase in the number of pixels, and expand the dynamic range.

According to a second aspect of the present invention, the upper limit value of the cumulative addition number is determined from the picked-up image signal immediately before the start of image pickup and the storage capacity of the image signal cumulative storage medium, and the cumulatively added image signal is the image signal. Do not exceed the storage capacity of the cumulative storage medium. This makes it possible to prevent the obtained image signal from becoming abnormal due to the cumulative addition result exceeding the storage capacity of the image signal cumulative storage medium.

According to the third aspect of the present invention, the input of the object image to the image pickup element is stopped immediately before the start of image pickup and immediately after the end of image pickup, and the image signals at that time are added and accumulated, and the average calculated for each pixel is calculated. The values are subtracted by the cumulative addition count from the captured image signal of each pixel that has been cumulatively added after the end of imaging.
As a result, dark current noise of the image sensor can be removed, and image deterioration due to dark current noise can be suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an image input apparatus of the present invention.

FIG. 2 is a control flowchart of the CPU in the configuration of FIG.

FIG. 3 is a diagram showing a configuration of an image sensor of the image input apparatus of the present invention.

FIG. 4 is a block diagram showing the configuration of another embodiment of the image input apparatus of the invention.

5 is a control flowchart of the CPU in the configuration of FIG.

FIG. 6 is a block diagram showing the configuration of another embodiment of the image input apparatus of the invention.

FIG. 7 is a control flow chart when a fixed pattern noise of an image sensor is created by the CPU in the configuration of FIG.

[Explanation of symbols]

1 Image sensor 2 amplifier 3 Signal processing circuit 4 A / D converter 5 adder 6 memory 7 CPU 8 Optical system for imaging 9 shutters 10 output switching circuit 11 Signal processing circuit 12 memories 13 adder 14 Subtractor

Claims (3)

[Claims] 1. An image input device for electronically picking up and inputting a subject, wherein the solid-state imaging device has an imaging region divided into a plurality of regions and can simultaneously output image signals of the divided plurality of regions. Image pickup means having an element, cumulative addition means for cumulatively adding image signals of a plurality of regions read from the image pickup element a plurality of times, and image signal cumulative storage for storing the image signals cumulatively added by the cumulative addition means An image input device comprising: 2. An upper limit of the number of cumulative additions that can be executed by the cumulative addition unit, based on the image signal of the subject image and the storage capacity of the image signal cumulative storage unit, when a subject image is captured and input from the image pickup unit immediately before the start of image pickup. A cumulative addition number upper limit value determining means for determining a value; and a cumulative addition number limiting means for limiting the cumulative addition number to the upper limit value or less at the time of imaging according to the determination of the cumulative addition number upper limit value determining means. The image input device according to claim 1. 3. A shutter means for stopping the input of a subject image to an image pickup element immediately before the start of image pickup and immediately after the end of image pickup, and image signals when the subject image input is stopped by this shutter means are added and accumulated to obtain an average value for each pixel. A subtraction for subtracting the average value calculated by the fixed pattern noise calculation means from the fixed pattern noise calculation means for calculating The image input device according to claim 1, further comprising: