JPH07123256A - Binarization device - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain an image with visually optimum density. [Structure] Three reading points are set apart from each other within the image forming range of the imaging lens 2 in the image reading unit 100, and one line of image signal is read at each point. Then, after counting the number of surplus bits at each point, the surplus ratio with respect to the surplus integration value is obtained. And
The threshold data for the obtained black character ratio is determined from the characteristic indicating the threshold correction value for the black character ratio, and this threshold data is supplied to the gradation control and binarization circuit 25. This allows
It is possible to obtain an image with a visually optimum density for the current subject.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binarization device,
For example, the present invention relates to a binarization device suitable for use in a scanning electronic image pickup device that performs spatial scanning using a line CCD and picks up an image of a subject.

[0002]

2. Description of the Related Art Generally, a binarizing device is often used in the field of processing image signals and the like, and is also used in an electronic image pickup device, for example. On the other hand, recently, a scanning type electronic imaging device (commonly called a stereoscopic copying device) that scans an image of a subject using a line CCD has been developed, and using this device, for example, character information written on a blackboard. It is being performed that the images are taken on the spot and printed out immediately for output. Unlike an electronic blackboard, using an electronic imaging device
It is extremely convenient because the character information can be printed even on an ordinary blackboard.

By the way, in a conventional electronic image pickup device using a binarization device, the AGC circuit controls the video signal read from the line CCD so that the level of the video signal becomes constant, thereby suppressing variations in density. I am trying.

[0004]

However, in the above-mentioned conventional electronic image pickup device, as shown in the waveform diagram of FIG. 8, a line having a light source such as a fluorescent lamp is used as a reference for a high-luminance video signal level. As AGC will operate as
Since the other video signal levels are lowered, the image becomes black as a whole. Further, as shown in the waveform diagram of FIG. 9, when a subject with little light and shade is imaged, the image signal level rises overall, resulting in a white-blown image.

As described above, in the conventional electronic image pickup apparatus using the binarization apparatus, an image having a large amount of black or an image having a large amount of white is formed depending on the exposure state, and an actual object is obtained. There was a problem in that there was a visual difference in density.

Therefore, an object of the present invention is to provide a binarizing device capable of visually obtaining an image having optimum density.

[0007]

In order to achieve the above object, a binarizing device according to the invention of claim 1 is a binarizing device for binarizing a video signal with a predetermined threshold value, and the binarizing device. Density detecting means for detecting the white or black density of the binarized video signal, and threshold setting for setting a predetermined threshold of the binarizing means based on the white or black density detected by the density detecting means. And means.

According to the second aspect of the present invention, the binarizing device has an image pickup means for picking up a subject image formed by the optical system, and a video signal obtained by picking up the image by the image pickup means with a predetermined threshold value. Binarizing means for binarizing, density detecting means for detecting the density of white or black of the image signal binarized by the binarizing means, and white or black density detected by the density detecting means. Threshold setting means for setting a predetermined threshold of the binarizing means based on the above.

In the binarizing device according to the third aspect of the present invention, the photographing means of the binarizing device according to the second aspect has a function of photographing a plurality of predetermined areas on the photographing surface. It is characterized by

[0010]

According to the first aspect of the invention, the image signal is captured by a predetermined threshold value and binarized to detect the density of white or black. Then, a threshold for binarization is set based on the detected white or black density. Therefore, it is possible to obtain an image with the visually optimum density.

According to the second aspect of the present invention, the image signal obtained by image pickup by the image pickup means is binarized by a predetermined threshold value to detect the density of white or black. Then, a threshold for binarization is newly set based on the detected white or black density. Therefore, similarly to the above, it is possible to obtain an image having a visually optimum density.

According to a third aspect of the invention, the image pickup means of the second aspect causes the plurality of predetermined areas on the image pickup surface to be photographed. Then, the video signal in each of the plurality of photographed predetermined areas is binarized by a predetermined threshold value to detect the density of white or black. Then, a threshold value for binarization is newly set based on each obtained density. Therefore, as the number of sampling points increases, it is possible to obtain an image with more optimal density.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an external view of an electronic imaging device (commonly called a stereoscopic copying device) to which a binarizing device according to the present invention is applied. In FIG. 1, reference numeral 1 denotes an electronic image pickup apparatus, which has a rectangular parallelepiped shape of a certain size, and is miniaturized for convenience of carrying. An image pickup lens 2 is provided on the front side of the electronic image pickup apparatus 1.
Are arranged. A viewfinder 3 and an operation unit 4 are arranged on the operation surface side of the upper surface of the electronic image pickup apparatus 1.

The viewfinder 3 is a portion where the photographer looks into the subject when determining the range of the subject, and the subject is focused on a focus screen (not shown) through the imaging lens 2. Can be seen from this viewfinder 3. An AF (autofocus mechanism) and a one-dimensional image sensor (line CCD) are built in on the optical axis penetrating the viewfinder 3 from the imaging lens 2.

The operation section 4 is a section for performing various operations necessary for image pickup, and is composed of, for example, a sheet switch, and can perform operations such as "start", "image pickup", and "print". A printer unit 5 is arranged beside the electronic image pickup apparatus 1, and the printer unit 5 prints and outputs the subject image formed on the image pickup surface by thermal transfer.

FIG. 2 is a block diagram showing the internal structure of the electronic image pickup apparatus 1. In FIG. 2, a line CCD (corresponding to an image pickup device) 21 in which elements are vertically arranged is attached to the image reading unit 100 behind the image pickup lens 2, and the line CCD 21 serves as a one-dimensional image sensor. The image reading unit 100 moves the image forming range of the imaging lens 2 in the lateral direction (arrow direction) to read an image for one screen. The video signal sequentially output from the line CCD 21 with the movement in the horizontal direction is amplified by the preamplifier 22 and the gain of the AGC amplifier 23 is adjusted to be constant so that the contour of the image is emphasized and corrected.

In the image reading section 100, three reading points (Rpa, Rpb, Rpc) are set as shown in the figure. This reading point (Rpa, Rp
Although details of (b, Rpc) will be described later, they are used when correcting the threshold value for the video signal.

The video signal output from the AGC amplifier 23 is subjected to gradation control and 2 after the shading correction circuit 24 corrects the brightness of the central portion and the peripheral portion of the image.
The gradation control is performed by the binarization circuit 25 and the binarized video signal is input to the pixel memory 26.

The pixel memory 26 stores a binarized video signal. The binary pixel data output from the pixel memory 26 is the black character counter 27 and the thermal head control circuit 3.
Entered in 2. The black character counter 27 counts the number of black bits of the input binary pixel data, and the output thereof is input to the controller 30 to obtain the black character ratio with respect to the count value.

The operations of the AGC amplifier 23, the gradation control / binarization circuit 25, and the pixel memory 26 are controlled by a controller 30. The controller 30 is composed of, for example, a microcomputer, and the gradation control / binarization is performed. The threshold value for the video signal in the circuit 25 is calculated. In this case, the threshold value is corrected corresponding to the surplus rate.

Here, the correction of the threshold will be described. FIG. 3 is a waveform diagram showing various signals when there is a light source such as a fluorescent lamp. When there is a light source such as a fluorescent lamp, the AGC operates based on the video signal of the light source, so that the level of the video signal becomes low as a whole. This can be seen from the fact that the white level is low and the black character ratio is high, as shown in the binary pixel data of the threshold value in FIG. FIG. 4 is a waveform diagram showing various signals when there is little difference in lightness and darkness as a whole. When there is little difference in lightness and darkness as a whole, as shown in the binary pixel data of the threshold in FIG. We know that the level is low (the surplus rate is low).

Assuming that the black pixel integrated value of the binary pixel data shown in FIG. 3 is "881", the black character ratio is as shown in FIG.
From the characteristic diagram showing the relationship between the black surplus integral value and the surplus ratio,
%"become. Further, assuming that the black surplus integral value of the binary pixel data shown in FIG. 4 is “1555”, the surplus ratio is as shown in FIG.
It becomes "30%" from the characteristic chart. In this case, the vertical axis of FIG. 5 is "3 points black integrated value", but this 3 point black integrated value is the black value with respect to the black integrated value of the reading points (Rpa, Rpb, Rpc) in the image reading unit 100. It is the rate.

FIG. 6 is a characteristic diagram showing a threshold correction value for the black character ratio. In this case, there are 32 levels of data as the threshold value, and the correction value is a ratio of how many levels the threshold value data is shifted up and down. Generally, the standard black character ratio is set to 15 to 33%, and therefore the threshold value is corrected by comparing the black character ratio of 24% with the black character ratio of the read video signal.

Since the black character ratio in FIG. 3 is set to 17%, the threshold value is corrected in -3 steps from FIG. FIG. 4 is a waveform diagram in which the threshold value shown in FIG. 3C is corrected. On the other hand, since the surplus rate in FIG. 4 is 30%, the threshold value is corrected in +2 steps. FIG. 5 is a waveform diagram in which the threshold value shown in FIG. 4C is corrected. If the surplus rate is outside the range of 15% to 33%, ± 4
Do not correct more than the points. In this way, the threshold value is changed depending on the surplus rate. The characteristic showing the relationship between the black surplus integral value and the black surplus rate shown in FIG. 5 and the characteristic showing the threshold correction value for the black surplus rate shown in FIG. 6 are written in the ROM inside the controller 30 in the form of a data table. .

The controller 30 outputs the corrected threshold value to the gradation control and binarization circuit 25. As a result, the gradation control and binarization circuit 25 outputs binary pixel data based on the corrected threshold value. For example, 2 shown in FIG.
The binary pixel data shown in FIG. 3F is output instead of the binary pixel data. In this case, since the threshold value is corrected in -3 steps, it can be seen that the white level of the binary pixel data has increased. Further, in FIG. 4, the binary pixel data shown in FIG. 4F is output instead of the binary pixel data shown in FIG. In this case, since the threshold value is corrected in +2 steps, it can be seen that the black level of the binary pixel data has increased. By the method as described above, the optimum threshold value is set according to the exposure state.

Returning to FIG. 2, the controller 30 controls the AGC amplifier 23, the gradation control and binarization circuit 25, the pixel memory 26, and the scanning of the line CCD 21 in addition to the above-described calculation for obtaining the threshold value. And outputs a drive signal to the motor control and drive circuit 31,
A control signal is output to the thermal head control circuit 32.

The motor control and drive circuit 31 is line C
A CCD moving motor 33 for driving the CD 21 laterally,
A lens moving motor 34 for driving the image pickup lens 2 in the optical axis direction for focusing, and particularly for moving the image pickup lens 2 by a predetermined amount along the incident direction of light at the time of image pickup, and a printer. A feed motor 35 that rotationally drives a roller (not shown) in the section 5 is controlled. The rollers of the printer unit 5 feed and drive the thermal paper P. Further, the line CCD 21 is driven by the charge transfer clock in order to transfer the charges corresponding to the amount of light converted by the line CCD 21.

The thermal head control circuit 32 controls the thermal head drive section 36 based on the control signal output from the controller 30 and the pixel data output from the image memory 26. The thermal head drive unit 36 operates according to an input signal or the like, so that the line CCD 21 is attached to the thermal paper P fed and driven by the roller.
The image for one screen is transferred by heat when is moved once in the horizontal direction.

The gradation control and binarization circuit 25 corresponds to binarization means. The black character ratio counter 27 corresponds to the density detecting means. The controller 30 corresponds to a threshold setting means. In addition, the image reading unit 10
0 corresponds to the image pickup means.

Description of Operation Next, the operation relating to printing of this apparatus will be described with reference to the flowchart shown in FIG. In this embodiment, in the reciprocal scanning of the line CCD 21, a threshold value is set by the black ratio on the outward path, and the image signal picked up by the threshold value on the return path is binarized. First, initialization is performed in step S1. That is, the controller 30 sets the threshold for the image signal to a prescribed threshold. After making this setting, clear the black ratio BUFF. Next, after moving the line CCD 21 to the home position in step S2,
The movement is started in the direction of the shooting start position (outward path).

Next, in step S3, it is determined whether or not the reading points Rpa, Rpb, and Rpc have been moved. In this determination, if it is determined that each point has been moved, the process proceeds to step S4, and one line of the image signal of the main scanning direction line at the reading point is read. First, it is assumed that reading is performed at the point Rpa.

After reading one line of the video signal of the main scanning direction line at the reading point Rpa, the video signal is binarized by a predetermined threshold value in step S5 and temporarily stored in the pixel memory 26. Then, the stored pixel data is transferred to the black character ratio counter 27, and the number of black character bits is counted. Then, in step S6, the count value of black character bits is input and written in the black character ratio BUFF.

After counting the number of black bits at the reading point Rpa, it is determined in step S7 whether or not the photographing start position is reached. At present, the process at the reading point Rpa is only completed, so it is determined that the photographing start position is not reached, and the process returns to step S3. Then, the same processing as described above is performed to count the number of black character bits at the reading point Rpb. When this process ends,
The same processing as above at the reading point Rpc is performed.

After the number of black character bits at each reading point Rpa, Rpb, Rpc is counted, the black character ratio with respect to the black character integral value of these three points is calculated.
Then, if it is determined in the determination in step S7 that it is the shooting start position, the threshold value data corresponding to the value of the black character ratio BUFF is determined with reference to the correction value table (FIG. 6) in step S8. After the threshold data is determined, the threshold data is output to the gradation control and binarization circuit 25 in step S9.
As a result, the threshold value with which a visually optimal density image is obtained for the current subject is determined. After the threshold is determined, the line CCD 21 is folded and moved in step S10, and then the image is taken in step S11 (return pass). Then, the image that has been photographed and whose density has been corrected is the thermal paper P.
Printed on.

In the above embodiment, the black character ratio counter 27 is provided and the density is corrected based on this count value.
There is an advantage that the load is small in terms of hardware and software.

Although the threshold value is corrected based on the black character ratio in the above embodiment, the threshold value may be corrected based on the white character ratio. Further, the application of the present invention is not limited to the electronic image pickup device, and an image signal or the like
Any device capable of digitizing can be applied.

[0037]

According to the present invention, the image signal is binarized in advance to detect the density of white or black, and 2 is detected from the detection result.
Since I set a new threshold for digitizing,
An image with a visually optimum density is obtained. In addition, since an image having an optimum density can be obtained at one time, there is almost no need to retake the image depending on the density condition as in the conventional case, so that the cost of paper and time can be saved.

[Brief description of drawings]

FIG. 1 is an external view of an electronic imaging device to which a binarizing device according to the present invention is applied.

FIG. 2 is a block diagram showing an internal configuration of the electronic image pickup apparatus of the embodiment.

FIG. 3 is a waveform chart of various signals in the electronic image pickup apparatus of the embodiment.

FIG. 4 is a waveform chart of various signals in the electronic image pickup apparatus of the same embodiment.

FIG. 5 is a characteristic diagram for explaining density correction in the electronic image pickup apparatus of the embodiment.

FIG. 6 is a characteristic diagram for explaining density correction in the electronic image pickup apparatus of the embodiment.

FIG. 7 is a flowchart showing a density correction operation in the electronic image pickup apparatus of the embodiment.

FIG. 8 is a waveform diagram of various signals in a conventional electronic image pickup device.

FIG. 9 is a waveform chart of various signals in a conventional electronic image pickup apparatus.

[Explanation of symbols]

 21 line CCD 25 gradation control and binarization circuit (binarization means) 26 pixel memory 27 black character ratio counter (density detection means) 30 controller (threshold setting means) 100 image reading unit (imaging means)

Claims (3)

[Claims] 1. A binarizing means for binarizing a video signal with a predetermined threshold value, a density detecting means for detecting a white or black density of the video signal binarized by the binarizing means, and the density. A threshold value setting means for setting a predetermined threshold value of the binarizing means based on the density of white or black detected by the detecting means; 2. An image pickup means for picking up a subject image formed by an optical system, a binarization means for binarizing a video signal obtained by picking up the image by the image pickup means, and the binary value. Density detecting means for detecting the density of white or black of the image signal binarized by the digitizing means, and a predetermined threshold value of the binarizing means is set based on the density of white or black detected by the density detecting means. And a threshold value setting means for controlling the threshold value. 3. The binarization apparatus according to claim 2, wherein the photographing means photographs a plurality of predetermined areas on a photographing surface.