JP2003319254A - Still picture pickup device and preread control method for still picture pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image of an object in an optimal exposure state controlled in advance when the reading instruction from a host device is received and to surely shorten a time from the reception of the reading instruction to acquisition of a still picture by detecting the movement of the object and performing pre-control of a shutter time and an amplification gain after the object stops. <P>SOLUTION: The still picture pickup device has an image reading part for reading the image of the object, a variable gain amplifier for amplifying an output signal from the image reading part, an image memory for storing the image of the object, an object presence/absence detector for detecting the presence/absence of the object based upon the image stored in the image memory, an object movement detector for detecting the movement of the object based upon the image stored in the image memory, and a control part for performing the pre-control of the shutter speed of the image reading part and the amplification gain of the variable gain amplifier when the object is detected and it is detected that the object stops before the reading instruction of the object is received. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a still image pickup device and a read-ahead control method in the still image pickup device.

[0002]

2. Description of the Related Art Conventionally, in a still image pickup device as an image input device for optically reading a still image such as a form or a catalog, the shutter time is controlled and the gain of an amplifier for amplifying the output of the image sensor is controlled. Then, the exposure state is adjusted.

FIG. 2 is a block diagram of a conventional still image pickup device.

In the figure, 100 is a mat for placing a subject, 101 is a subject such as a form or catalog which is placed on the mat 100 and a still image is optically read, and 102 is for illuminating the subject. Illuminating device including a fluorescent lamp, 103 is a lens, and 104 is the subject 1
CCD (ChargeCo
an image sensor such as an up-loaded device, 10
5 is an AGC amplifier as a variable gain amplifier for amplifying the output signal of the image sensor 104, and 106 is the AGC
An A / D converter that converts an analog signal output from the amplifier 105 into a digital signal, 107 is an image memory that stores an image captured by the image sensor 104, 10
Reference numeral 8 is a brightness detector for detecting the brightness of the image stored in the image memory 107, and 109 is an object presence / absence for detecting whether or not the image of the object 101 is included in the images stored in the image memory 107. The detector 120 is the shutter time of the image sensor 104 and the AGC.
The control unit controls the amplification gain of the amplifier 105 in advance.

In the still image pickup device,
When it is detected that a form as a subject 101 whose still image is optically read is placed on the mat 100, the shutter time is controlled and the amplification gain is controlled without waiting for a reading instruction from a host device (not shown). Then, the exposure state is adjusted. In this case, the control unit 120 determines that the form as the subject 101 is the mat 100 based on the signal from the subject presence / absence detector 109.
If it is determined that the exposure position is on, the control signal is transmitted to the image sensor 104 and the AGC amplifier 105 based on the output of the brightness detector 108 to control the shutter time and the amplification gain so as to optimize the exposure state. To do.

As described above, when the still image pickup device detects that the form as the subject 101 is placed on the mat 100, the shutter time and the amplification gain are preceded without waiting for the reading instruction from the host device. Advance control of
Since the exposure is adjusted so that the optimum exposure state is obtained, when the reading instruction from the host device is received, the image of the form can be obtained in the optimal exposure state that has been adjusted in advance, and the still image is acquired from the reading instruction. It is possible to shorten the time until.

[0007]

However, in the above-mentioned conventional still image pickup device, only the presence or absence of the form as the subject 101 is detected, and therefore, the form is the mat 1
00, the shutter time and the amplification are detected when the presence / absence of the document is detected by the subject presence / absence detector 109 even when the document is still in a predetermined position, that is, even when the document is still moving. Gain control is started. Therefore, the control of the shutter time and the amplification gain by the control unit 120 becomes unstable, and it takes time until the values of the shutter time and the amplification gain converge to the optimum values.

That is, when the illuminance of the illuminating device 102 is stable and the brightness of the object 101 is constant and the shutter time or the value of the amplification gain is within a predetermined range in advance, the shutter time and the amplification gain are Since the value quickly converges to the optimum value, when the reading instruction from the host device is received, the image of the form can be immediately obtained in the optimal exposure state, and the time from the reading instruction to the acquisition of the still image is shortened. You can do it. However,
When the form as the subject 101 is moving, it is highly possible that a hand or the like is within the reading field of view, and the brightness in the reading field of view greatly changes due to the shadow of the hand or the like. Therefore, the control of the shutter time and the amplification gain by the control unit 120 becomes unstable, the values of the shutter time and the amplification gain do not converge to the optimum values, and the situation may occur that the control is still in progress even when the reading instruction is received. There is. In that case, it takes more time to acquire a still image than when the preceding control is not performed.

The present invention solves the problems in the conventional still image pickup device, detects the motion of the subject, and performs the advance control of the shutter time and the amplification gain after the subject has stopped, thereby making it possible to use the host device. When a reading instruction from the camera is received, an image of the subject can be obtained in an optimally adjusted exposure state that has been adjusted in advance, and still image capture that can reliably shorten the time from receiving the reading instruction to acquiring the still image An object of the present invention is to provide a read-ahead control method for a device and a still image pickup device.

[0010]

Therefore, in the still image pickup apparatus of the present invention, an image reading unit for reading an image of a subject, a variable gain amplifier for amplifying an output signal of the image reading unit, and the subject An image memory that stores images, and based on the images stored in the image memory,
The subject presence / absence detector for detecting the presence / absence of the subject, the subject movement detector for detecting the movement of the subject based on the image stored in the image memory, and the reception instruction for the subject before receiving the reading instruction. When a subject is detected and it is detected that the subject is still, the control unit controls the shutter time of the image reading unit and the amplification gain of the variable gain amplifier in advance.

In another still image pickup device of the present invention,
Further, it has a reference image memory for detecting the movement of the subject.

In still another still image pickup device of the present invention, an A / D converter for converting an analog signal output from the variable gain amplifier into a digital signal, and an image of an image stored in the image memory. And a brightness detector for detecting the density.

In the preceding reading control method in the still image pickup apparatus of the present invention, the image reading unit for reading the image of the subject, the variable gain amplifier for amplifying the output signal of the image reading unit, and the image of the subject are stored. In a still image pickup device having an image memory, the presence or absence of the subject is detected based on the image stored in the image memory, the movement of the subject is detected based on the image stored in the image memory, If the subject is detected and the stillness is detected before the subject reading instruction is received, the shutter time of the image reading unit and the amplification gain of the variable gain amplifier are preliminarily controlled.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a still image pickup device according to the first embodiment of the present invention, and FIG. 3 is a perspective view of the still image pickup device according to the first embodiment of the present invention.

In FIG. 3, reference numeral 25 denotes a still image pickup device for optically reading a still image of a subject, which is a mat 10 on which the subject is placed, a pillar 26 attached to the mat 10, and the pillar 26. Has a photographing unit 27 attached to the upper end of the. In the present embodiment, the still image capturing device 25 is an image input device that optically reads a still image of the subject 11 such as a form or catalog shown in FIG. It should be noted that the subject 11 may be something other than a form or a catalog, and may be of any kind, but a relatively flat and flat surface such as a print medium such as paper. It is desirable to have a shape.

In FIG. 1, the still image pickup device 2 is shown.
The internal structure of 5 is shown. In FIG. 1, 11 is a subject placed on the mat 10 and 12 is the subject 1
An illuminating device such as a fluorescent lamp for irradiating 1; a lens; 14; a CCD for scanning the subject 11 to capture an image; and an image as an image reading unit having a built-in electronic shutter. It is a sensor and outputs an image signal S1. The lens 13 and the image sensor 14 are attached to the photographing unit 27.

Reference numeral 15 is an AGC amplifier as a variable gain amplifier which amplifies the image signal S1 of the image sensor 14 to a predetermined level and outputs an image signal S2, and 16 is an analog signal which is an output of the AGC amplifier 15. Is an A / D converter that converts the signal into a digital signal. Here, the A / D converter 16 uses, for example, a fixed voltage as a reference voltage on the + side and 0 [V] as a reference voltage on the − side, and outputs the image signal S2 of the AGC amplifier 15 as follows.
For example, A / D conversion is performed with a quantization bit number of 8 [bit] to generate a digital image signal S3.

An image memory 17 receives the digital image signal S3 output from the A / D converter 16 and stores the image captured by the image sensor 14. Reference numeral 18 denotes a brightness detector for detecting the image density as the brightness of the image stored in the image memory 17, and 19 denotes whether the image of the subject 11 is included in the images stored in the image memory 17. It is a subject presence / absence detector that detects whether or not. Reference numeral 20 is a microprocessor or the like, and is an image sensor 1 as an image reading unit.
4 is a control unit that controls the shutter time of 4 and the amplification gain of the AGC amplifier 15 as a variable gain amplifier in advance. Then, the control unit 20 controls the operation of the electronic shutter built in the AGC amplifier 15 and the image sensor 14 based on the outputs of the brightness detector 18 and the subject presence / absence detector 19. . Also,
If the image sensor 14 does not include an electronic shutter, an external shutter (not shown) is provided, and the controller 20 controls the operation of the external electronic shutter.

Reference numeral 21 is a reference image memory, which binarizes the image stored in the image memory 17 according to a predetermined binarized slice standard and stores it. Reference numeral 22 is a subject motion detector, which binarizes the image stored in the image memory 17 according to a predetermined binarized slice standard and compares it with the image stored in the reference image memory 21. , Detecting whether the subject 11 is moving,
It is designed to be sent to.

Next, the operation of the still image pickup device 25 having the above construction will be described.

FIG. 4 is a diagram showing the operation of the still image pickup device according to the first embodiment of the present invention, and FIG. 5 is a first diagram showing the operation of the still image pickup device according to the first embodiment of the present invention. 6 is a second flowchart showing the operation of the still image capturing apparatus according to the first embodiment of the present invention.

In the present embodiment, the still image pickup device 2
Reference numeral 5 denotes an opening time of the electronic shutter, that is, a shutter time value and an amplification gain value of the AGC amplifier 15, and an appropriately set initial value is acquired in advance.
The object 1 operates on the mat 10 based on the initial value.
The presence of 1 is constantly monitored.

First, when the power is turned on, the still image pickup device 25 acquires an image for one frame, loads it into the image memory 17, and stores it. In this case, the image sensor 1
Reference numeral 4 denotes an image signal S obtained by capturing an image for one frame.
1 is output. The image signal S1 is the AGC amplifier 1
Amplified by 5 and output as an image signal S2, the A / D converter 16 outputs the digital image signal S2.
3 is generated. Then, the digital image signal S3
Are fetched and stored in the image memory 17.

Subsequently, the subject presence / absence detector 19 detects whether or not the image of the subject 11 is included in the images stored in the image memory 17. In this case, the subject presence / absence detector 19 determines whether the multivalued image in the image memory 17 is 1 or 2 based on an appropriate binarized slice, that is, whether it is equal to or more than an appropriate threshold value. It is converted into a binary image of 0, and 1 (in the present embodiment,
It is assumed that binarization has been performed so that the subject 11 portion becomes 1 and the background portion becomes 0. ), The number of pixels is counted, and when the value of the counted number of pixels is larger than the subject presence / absence determination parameter value determined in advance by experiments or the like, it is determined that a subject is present.

When it is determined that there is no subject, the above-described operation is repeated to detect the presence or absence of the subject 11.

On the other hand, when it is determined that the subject is present, the still image pickup device 25 clears the value of the stillness determination counter M for counting the state in which the subject 11 is still to zero. Then, an image for one frame is acquired, loaded into the image memory 17, converted into a binary image of 1 or 0 by a predetermined binarized slice, and then stored in the reference image memory 21. in this case,
The positional relationship between the images of the subject 11 in the image memory 17 is as shown at the top of the elapsed time T1 in FIG.
The image of the subject 11 after conversion into the value image is shown in FIG.
As shown in the second stage of the elapsed time T1 in.

Subsequently, the still image pickup device 25 acquires the image for the next one frame, stores it in the image memory 17, and converts it into a binary image of 1 or 0 by a predetermined binary slice. Then, the subject motion detector 22 detects the image of the subject 11 captured in the image memory 17 and converted into the binary image, and the subject 11 after being converted into the binary image stored in the reference image memory 21. Exclusive OR with image (Exc
positive OR) and count the number of non-matching pixels with a value of "1".

In this case, in the image memory 17,
The positional relationship of the subject 11 in the image for the next one frame is as shown in the uppermost stage of the elapsed time T2 in FIG. 4, and the image of the subject 11 captured in the image memory 17 and converted into a binary image is shown in FIG. As shown in the third row of the elapsed time T2 in FIG. Further, the image of the subject 11 after being converted into the binary image stored in the reference image memory 21 is the elapsed time T2 in FIG.
As shown in the second row of. Therefore, the exclusive OR with the image of the subject 11 after being converted into the binary image stored in the reference image memory 21 is as shown in the fourth row of the elapsed time T2 in FIG. Become. It should be noted that in the figure, a portion where a non-matching pixel having an exclusive OR value of “1” exists is filled in with black.

Here, since the portion where the non-coincidence pixel having the value of the exclusive OR is "1" represents the magnitude of the displacement of the object 11 in two consecutive frames,
If the movement of the subject 11 is large, that is, the subject 11
If the movement of the subject is fast, the movement is wide, and if the movement of the subject 11 is small, that is, if the movement of the subject 11 is slow, the movement is narrow, and if the subject 11 is completely stopped, it disappears.

Therefore, the subject motion detector 22 determines that the subject 11 is moving if the number of non-matching pixels whose exclusive OR value is "1" is not less than the subject motion determination parameter N as a threshold value. judge. Then, the still image capturing apparatus 25 clears the value of the stillness determination counter M for counting the state in which the subject 11 is still to zero, and repeats the above-described operation. In this case, the image of the subject 11 after being converted into the binary image stored in the reference image memory 21 is updated, as shown in the second row of the elapsed time T3 in FIG.

On the other hand, the subject motion detector 22 determines that the subject 11 is stationary if the number of mismatched pixels whose exclusive OR value is "1" is less than the subject motion determination parameter N. Then, the still image capturing device 25 adds 1 to the value of the stillness determination counter M.

Subsequently, in the still image pickup device 25, the value of the stillness determination counter M is used as a threshold value for the stillness determination parameter St.
It is determined whether it is No or more. Here, the stillness determination parameter StNo is a parameter for determining whether or not the subject 11 remains stationary for a predetermined time or more, that is, for a predetermined number of frames or more. And
When the value of the stillness determination counter M is not greater than or equal to the stillness determination parameter StNo as the threshold, the still image capturing device 25
Further, an image for the next one frame is acquired, loaded into the image memory 17, converted into a binary image of 1 or 0 by a predetermined binarized slice, and the above-described operation is repeated.

On the other hand, when the value of the stillness determination counter M is greater than or equal to the stillness determination parameter StNo as a threshold value, the still image pickup device 25 determines that the subject 11 has been stationary for a predetermined time or more, that is, for a predetermined number of frames or more. It controls the operation of the electronic shutter built in the AGC amplifier 15 and the image sensor 14. In this case, the control unit 20
Controls the shutter time of the electronic shutter based on the output of the brightness detector 18, and
The amplification gain of the C amplifier 15 is controlled.

Here, the brightness detector 18 detects the image density as the brightness of the image stored in the image memory 17 and compares it with a predetermined target image density to obtain the image density. Determine whether the brightness is appropriate, too dark, or too bright.

When it is determined that the image density is appropriate, the current shutter time and amplification gain values set as initial values are used as they are. Further, when it is determined that it is too dark, the control unit 20 lengthens the shutter time of the electronic shutter or increases the value of the amplification gain of the AGC amplifier 15.
Then, the image is acquired again, the image density is detected again by the brightness detector 18, and the process is repeated until an image density of an appropriate value can be obtained. Further, if it is determined that the image sensor 14 is too bright, the control unit 20 similarly causes the image sensor 14 to operate.
Shutter time is shortened, or AGC amplifier 1
The value of the amplification gain of 5 is reduced and repeated until the predetermined image density can be obtained, and the optimum shutter time and the value of the amplification gain are obtained.

Next, when the optimum shutter time and amplification gain values are determined by performing advance control of the shutter time and amplification gain as described above, the still image pickup device 25 is a higher-level device (not shown). Wait until the reading instruction is received from. Then, when receiving the reading instruction from the host device, the electronic shutter built in the image sensor 14 is operated so that the optimum shutter time determined by performing the advance control of the shutter time and the amplification gain, AG with optimum amplification gain
The C amplifier 15 is operated to capture an image of the subject 11, and the image is stored in the image memory 17. Then, when the photographing of one subject 11 is completed, the photographing of the next subject is started.

Next, the flowchart will be described. Step S1 Turn on the power supply. In step S2, one frame of image is acquired and stored in the image memory 17. Step S3 The presence or absence of the subject 11 is detected. In step S4, it is determined whether or not the subject 11 is present. If the subject 11 is present, the process proceeds to step S5 and the subject 11
If there is not, the process returns to step S2. In step S5, the stationary determination counter M is set to 0. In step S6, an image for one frame is acquired and loaded into the image memory 17. In step S7, binarization is performed. In step S8, the image is stored in the reference image memory 21. In step S9, an image for one frame is acquired and loaded into the image memory 17. In step S10, binarization is performed. In step S11, the exclusive OR is taken between the image in the image memory 17 and the image in the reference image memory 21. In step S12, the number of unmatched pixels "1" is counted. In step S13, it is determined whether the number of mismatched pixels “1” is smaller than the subject motion determination parameter N. If the number of mismatched pixels "1" is smaller than the subject motion determination parameter N, the process proceeds to step S14, and if the number of mismatched pixels "1" is greater than or equal to the subject motion determination parameter N, the process returns to step S5. In step S14, 1 is added to the stationary determination counter M. In step S15, it is determined whether or not the stillness determination counter M is greater than or equal to the stillness determination parameter StNo. If the stillness determination counter M is greater than or equal to the stillness determination parameter StNo, the process proceeds to step S16. If the stillness determination counter M is less than the stillness determination parameter StNo, the process returns to step S9. In step S16, the shutter time and the amplification gain value are controlled. In step S17, the reading instruction is waited, and when the reading instruction is received, the process proceeds to step S18. In step S18, the image is photographed, and the process returns to step S2 to photograph the next subject 11.

As described above, in the present embodiment, the still image pickup device 25 confirms that the subject 11 is still, so that the shutter time and the amplification gain are preceded after the brightness on the subject 11 is stabilized. Since the control is performed, the values of the shutter time and the amplification gain quickly converge to the optimum values. Therefore, when the reading instruction from the host device is received, the image of the form can be obtained in the optimal exposure state adjusted in advance, and the time from the reading instruction to the acquisition of the still image can be surely shortened.

Next, a second embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the description is abbreviate | omitted by giving the same code | symbol.

FIG. 7 is a block diagram of a still image pickup device according to the second embodiment of the present invention.

In the first embodiment, in addition to the image memory 17 for storing the photographed image, the reference image memory 2 for detecting the movement of the subject 11.
1 is provided, but in the present embodiment, the reference image memory 21 is omitted and the image memory 17
Is also used as a reference image memory.

Next, the operation of the still image pickup device 25 having the above structure will be described.

By the way, in the first embodiment, an image for one frame is taken into the image memory 17, converted into a binary image, and then stored in the reference image memory 21. Then, the reference image memory 21
An exclusive OR is taken between the image stored in the image and the image obtained by acquiring the image for the next one frame, loading it in the image memory 17, and converting it into a binary image.

On the other hand, in the present embodiment,
The image for one frame is fetched and stored in the image memory 17, and the image for the next one frame is stored in the image memory 1.
The data is directly transmitted to the subject motion detector 22 without being taken into 7, and the subject motion detector 22 takes an exclusive OR with the image stored in the image memory 17. For other operations,
The description is omitted because it is similar to the first embodiment.

Thus, in this embodiment, the reference image memory 21 in the first embodiment is used.
Therefore, the configuration of the still image capturing device 25 is simplified, and the movement of the subject 11 can be simultaneously detected while capturing the image of the subject 11. Therefore, the cost of the still image pickup device 25 can be reduced, and the processing speed can be improved.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention, and they are not excluded from the scope of the present invention.

[0048]

As described in detail above, according to the present invention, when a reading instruction is received from a host device, an image of a subject can be obtained in an optimum exposure state adjusted in advance. It is possible to reliably reduce the time from the reception of the instruction to the acquisition of the still image.

[Brief description of drawings]

FIG. 1 is a block diagram of a still image capturing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a conventional still image pickup device.

FIG. 3 is a perspective view of a still image capturing device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an operation of the still image capturing apparatus according to the first embodiment of the present invention.

FIG. 5 is a first flowchart showing an operation of the still image capturing apparatus according to the first embodiment of the present invention.

FIG. 6 is a second flowchart showing the operation of the still image capturing apparatus according to the first embodiment of the present invention.

FIG. 7 is a block diagram of a still image capturing device according to a second embodiment of the present invention.

[Explanation of symbols]

11 subject 14 image sensor 15 AGC amplifier 16 A / D converter 17 Image memory 18 Brightness detector 19 Object presence detector 20 Control unit 21 Reference image memory 22 Object motion detector 25 Still image pickup device

Claims (4)

[Claims] 1. An image reading unit for reading an image of a subject, (b) a variable gain amplifier for amplifying an output signal of the image reading unit, and (c) an image memory for storing the image of the subject. (D) A subject presence / absence detector for detecting the presence / absence of the subject based on the image stored in the image memory, and (e) a movement of the subject is detected based on the image stored in the image memory. An object motion detector, and (f) before receiving the object reading instruction,
A still image, comprising: a shutter time of the image reading unit and a control unit that performs advance control of an amplification gain of the variable gain amplifier when the subject is detected and the still image is detected to be still. Imaging device. 2. The still image pickup device according to claim 1, further comprising a reference image memory for detecting the movement of the subject. 3. An A / D converter for converting an analog signal output from the variable gain amplifier into a digital signal, and a brightness detector for detecting an image density of an image stored in the image memory. The still image pickup device according to 1 or 2. 4. An image reading unit for reading an image of a subject, (b) a variable gain amplifier for amplifying an output signal of the image reading unit, and (c) an image memory for storing the image of the subject. In the still image pickup device having (d)
The presence or absence of the subject is detected based on the image stored in the image memory, (e) the movement of the subject is detected based on the image stored in the image memory,
(F) If the subject is detected and it is detected that the subject is stationary before the instruction to read the subject is received, the shutter time of the image reading unit and the amplification gain of the variable gain amplifier are preceded. A pre-reading control method in a still image pickup device, which is characterized by controlling.