JPS59117861A - Binary-coding device of video signal - Google Patents

Abstract

PURPOSE:To obtain a binary-coding device of a video signal not affected by the lighting condition and sensitivity of an image pickup tube by inputting the video signal of an object at the same time, comparing the signal with a reference voltage by N sets of comparison means and changing the binary level at the N sets of areas. CONSTITUTION:A letter A written on a blue ground paper 2 is divided into regions a4-a6 having a contrast by placing a black background plate 1 at the left and is image picked up by an image pickup device 20. A video signal from the device 20 is amplified 21 and inputted to comparators 25-27 by each region. Adjusting voltages 33-35 from adjusting voltage generating circuits 22-24 are inputted to the comparators 25-27 at each region, an output of the amplifier 21 is compared with binary-coding threshold values 30-32 at each region and binary-coding signals S1-S3 are outputted from the comparators 25-27. Thus, the variation in the lightness at each region is corrected in this way. Then, the signals S1-S3 are transmitted as one binary-coding signal 29 based on the control of a region split circuit 28.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for binarizing a video signal based on a plurality of threshold values.

This type of binarization device is required to generate a binarized signal that can faithfully reproduce the raw image of the subject.

For this reason, conventional devices that binarize video signals have adjusted the binarization level (threshold) using the black level of the video signal as a reference. However, since the distribution of light irradiated onto a subject is generally not uniform, it has been difficult to adjust the binarization level (threshold). below,
This problem will be explained using FIGS. 1 and 2.

Figure 1 is an explanatory diagram of photoelectric conversion of white letters 1''AJ written on a blue mount.Here, 1 is a black background plate (hereinafter referred to as sample hold plate), and 2 is white letters ``AJ''. A blue board with "A" written on it, the area surrounded by 3 is the effective screen of the photoelectric conversion element, 4 is a bright and dark area ■, 5 is a bright and dark area ■, 6 is a bright and dark area ■, 7 is a bright and dark area ■ 8 indicates the horizontal scanning line direction in area a, 8 indicates the horizontal scanning line direction in area 2, and 9 indicates the horizontal scanning line direction in area 2.

Further, FIG. 2 is a video signal representing the white character "A" in FIG. Here, 10 is the video signal corresponding to the horizontal scanning line 7, 11 is the video signal No. 18 corresponding to the horizontal scanning line 8, and 12 is the video signal corresponding to the horizontal scanning line 9.
No. 13 is the sample hold point, 14 is the adjustment "b, pressure (
15 is an area corresponding to the sample hold plate l, 16 is an area corresponding to the mount 2, 17 is an area corresponding to the effective screen, 18 is a fixed binarization level (threshold), 18 indicates a binary signal.

Conventionally, in a video signal binarization device that images a bright and dark mount 2 as shown in FIG. 1 using an imaging device such as a television camera and binarizes the resulting video signal, A method was used in which a black matte background board (ie, sample hold board 1) was placed on the surface of the image, and this was used as a reference black level to convert the image into 2I at one binarization level.

Now, in Figure 1, area ■5. Area 06. Area■4
Assuming that the brightness decreases in the order of
When the mount 2 on which AJ is written is observed with a photoelectric conversion element (for example, an image pickup tube such as HISHICON), a video signal as shown in FIG. 2 is obtained from the horizontal scanning lines in each of these areas.

That is, a reference sample hold point 13 was determined in advance in the region 15 of the sample hold plate 1, and the value obtained by adding the adjustment voltage 14 to that voltage was set as the binarization level 18 (this was set as the fixed binarization level). (called ζ). However, in area ■4, the video signal level is lower than fixed binarization level 18, in area ■5, the video signal level is higher than fixed binarization level 1B, and in area ■6, fixed binarization level 18
The video signal level is slightly higher. In the binary signal 18 obtained in this way, the white character "rA"
The disadvantage is that the upper part is chipped or becomes thinner, and as it goes downward, it becomes thicker.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a video signal binarization device that is not affected by illumination conditions, sensitivity of an image pickup tube, shading, etc.

In order to achieve such an object, the present invention includes N comparing means that simultaneously introduce video signals of a subject and compare each with a predetermined reference signal, and a series of N comparing means that sequentially switch the output signals from the comparing means. 2 (lli conversion 4; 4''3), and is configured to change the binarization level for each of the N regions forming the subject.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 shows a video signal binarization device according to an embodiment of the present invention. Here, 20 is an imaging device, 21 is an amplifier circuit,
22 is an adjustment voltage generation circuit that sets the binary level (threshold) in area ■4; 23 is an adjustment voltage generation circuit that sets the binarization level (threshold) in area ■5;
4 is an adjustment voltage generation circuit for setting the binarization level (threshold) in area 6; 25 is a comparator for area 4; 28 is a comparator for area 5; 27 is a comparator for area @6; Sl to S3 are these comparators 25, 28
,2? The output signal 28 divides the screen based on the number of horizontal scanning lines, and accordingly divides the 82-binarized signal sent from the comparators 25, 28, and 27 and synthesizes them into a series of binary signals. A region dividing circuit that sends out a control signal for
NDI to AND3 are AND gates that allow only one of the comparator output signals 5t-S3 to pass in response to a control signal from the area dividing circuit 3; OR is an OR gate; 28
shows a binarized signal obtained by this example.

FIG. 4 is a timing diagram illustrating the operation of FIG. 3. Here, 28 is the binarized signal shown in Fig. 3, 30 is the binarization level (threshold) of area ■4, and 31 is the 2nd level of area ■5.
The digitization level (threshold value) 32 indicates the binarization level of the region (6), 33 the adjustment voltage of the region (4), 34 the adjustment voltage of the region (2)5, and 35 the adjustment voltage of the region (2)6.

In this embodiment, in order to prevent variations in brightness in each region of the subject, the imaging device 20 such as a television camera is
The detected video signal is input to the amplifier circuit 21.

Then, the amplified video signal and the signals sent from the adjustment voltage generation circuits 22, 23.24 for each area are input to each comparator 25, 28, 27. Thereby, variations in brightness in each area can be corrected. Thereafter, based on the control of the area dividing circuit 28, three two
The digitized signal Sl-531 is sent out as one 2', (tj digitized signal 29).

Also, changes in lighting conditions, sensitivity, and shading.

Appropriate binarized signals can be obtained even for blurred images by changing the region division positions.

Note that the present invention is directed to the video 413 representing the above-mentioned printed figure.
It goes without saying that the present invention can be applied not only to the case of binarizing numbers, but also to the case of binarizing video signals such as stamped characters and figures.

As explained above, according to the present invention, it is possible to binarize the video signal by following the drift of the video signal, changes in illumination on the subject, etc., so that it is possible to accurately identify the subject, inspect the appearance of the subject, etc. I can do things well.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining a general subject, FIG. 2 is a line diagram showing a video signal representing the subject in FIG. 1, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. FIG. 4 is a diagram illustrating the operation of FIG. 3; 1... Black background board, 2... Mount with white letters rAJ written on it, 3... Effective screen of photoelectric conversion element, 4.5.6... Bright and dark area, ? , 8.9...Horizontal scanning line direction, 10...Video signal corresponding to horizontal scanning line 7, 11.
...Video signal corresponding to horizontal scanning line 8, 12...Video signal corresponding to horizontal scanning line 9, 13...Sample hold point, 14...Adjustment voltage, 15...Corresponding to background plate 1 16...Area corresponding to mount 2, 17...Area corresponding to the effective screen, 18...Fixed binarization level (threshold), 18...Binarization Signal, 20... Imaging device, 21... Amplification circuit, 22.23.24... Adjustment voltage generation circuit, 25.26
．． 27... Comparator, S]~S3... Comparator output, 28... Area division circuit, AND l~AND3... AND gate, OR...
ORGATE, 28... 2 I
3.34.35... Adjustment voltage. Patent applicant Fuji Electric Manufacturing Co., Ltd. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1) N comparison means that simultaneously introduce video signals of a subject and compare each video signal with a predetermined reference signal. The output signal from the comparison means is sequentially switched to obtain a series of two
2 of the video signal, comprising: a control means for transmitting a digitized signal, and the 2-sensification level is changed for each of the N regions constituting the subject;
Value device.