JPS636969A - Picture data input system - Google Patents

Abstract

PURPOSE:To input pictures of different types including a character recorded on a recording medium properly by making the reference signal level of a threshold a variable or a fixed level in a prescribed scanning area in one scanning line at the time of an analog/digital conversion. CONSTITUTION:The level is set by following the signal level on a medium surface at the time of scanning a character part by the scanning line in a part where the character and the picture are mixed end recorded at the time of the analog/digital conversion, as the threshold. Since the character has a large density difference from the medium surface, a level difference corresponding to a stain on the medium surface is corrected and read. At the time of reading the picture part, the scanning area of the picture by the reading format information of a document is preset to stop the change in the reference signal level of a level setting circuit and set the reference signal level to a level immediately preceding thereto so as to prevent the reference signal level from being lowered by erroneously recognizing the half tone level of the picture as a medium surface level. Accordingly, the variable density of the picture can be converted according to the level.

Description

[Detailed Description of the Invention] [Summary] The present invention is a method for inputting an image on a recording medium as image data in image processing, and in analog/digital conversion to obtain digital data of pixels constituting the image, By setting the reference signal level used as a threshold to a variable or fixed level in a predetermined scanning area within one scanning line, different types of images including characters recorded on a recording medium can be accurately input.

[Industrial application field]

The present invention relates to a method for outputting an image on a recording medium in image processing as digital data of pixels constituting the image (hereinafter referred to as image data).

In recent years, with advances in technology, character recognition devices that read and recognize characters recorded on recording media, such as forms, are now capable of recording not only characters but also images, such as photographs, on forms. In recent years, it has become necessary to have an image input device equipped with an image processing function to read the photographic image as image data, and to input the image data.

However, character data is usually binary data,
Since images require gradation expression, they are multivalued data.

Therefore, different reading methods are required for characters and images, and reading them particularly when they are mixed in one form has become a problem.

[Conventional technology]

FIG. 6 is a block diagram of the configuration of a conventional human-powered image device, FIG. 3 is a diagram for explaining a form, and FIG. 5 is a diagram for explaining signal levels.

The image on the form is converted into a light intensity signal by optical scanning that moves in the direction of the scanning line (main scanning direction) and the direction perpendicular thereto (sub scanning direction), and is converted into a light intensity signal by the photoelectric converter of the image input device shown in Fig. 6. 1, for example, a CCD (charge-coupled device), etc.

The light intensity signal is converted into an electrical analog signal (hereinafter referred to as a video signal) for each pixel constituting the image, and the level setting circuit 2 generates a predetermined signal level and performs analog/digital (A/D) conversion. The circuit 3 compares the signal output from the photoelectric converter 1 with a reference signal level, and outputs the signal as image data to an image processing device 5, for example, a character or image recognition device.

As shown in Figure 4, image data is detected when the video signal shown by the solid line falls below the reference signal level shown by the dotted line.
That part is used as an image signal.

In addition, if the optical characteristics of the form surface, such as the reflectance due to the paper quality, stains, contamination, etc., are below the standard signal level, the data will be read and output as the same as the recorded data, so to avoid this, If the level change just before that change is small, it is assumed that it is a change in the form surface, and the reference signal level is changed to follow that level.

Then, the level setting circuit 2 generates the above-mentioned reference signal level.

In this case, reading can be performed without mistaking optical fluctuations on the form surface due to paper quality or dirt as described above as image signals.

However, images with intermediate tones like photographs,
If a photograph is read by following the reference signal level in the same manner as described above, the data cannot be read correctly because low-density areas are treated as fluctuations in the form surface.

Therefore, when reading an image such as a photograph, the reading mode is switched so that the reading is performed with the reference signal level fixed.

If the form is separated into a character recording part A-B and an image recording part CD as shown in FIG. A stop signal CLMP that stops changing the reference signal level during that time is sent to the level setting circuit 2, and at position C where the image recording portion ends, the mode is switched to the character (line drawing) mode again and characters are read.

[Problem that the invention seeks to solve]

In this conventional method, when the reference signal level fluctuates to follow the media surface level in a recorded area where characters and images are mixed, such as the C-section in Figure 3 on the same document, the characters may be read well, but the images cannot be read. If proper reading is not possible and the reference signal level is fixed for image reading, the effective function for character reading cannot be utilized.In other words, even if either characters or images can be read properly, - There was a problem that it could not be read properly.

[Means for solving problems]

The above problem is that the level setting circuit that generates the reference signal level fixes the reference signal level that follows the signal level on the surface of the recording medium to the level immediately before the scanning area of the preset scanning line. This problem is solved by the image data input method of the present invention, which does not change the image data during the scan area.

[Operation] When a scanning line scans a character portion in a portion where a mixture of characters and images is recorded, the level is set to follow the signal level on the medium surface.

Since characters have a large density difference with the medium surface, it is effective to read the characters by correcting the level difference corresponding to dirt on the medium surface.

When reading an image part, the image scanning area is set in advance based on the reading format information of the form, and the change in the reference signal level of the level setting circuit is stopped, so that the halftone level of the image is mistakenly recognized as the media surface level. Since the reference signal level is fixed at the level just before it so as not to drop, the shading of the image is converted according to that level.

〔Example〕

FIG. 1 shows a block diagram of an embodiment of the image data input method of the present invention.

Note that the same reference numerals indicate the same objects throughout the figures.

In FIG. 1, an image converted into light intensity by optical scanning is input to a photoelectric converter 1 and converted into an electric intensity signal, that is, a video signal.

This video signal is input to a level setting circuit 2 and an analog/digital conversion circuit 3.

The video signal input to the level setting circuit 2 is input to the level determination circuit 21, and compared with the reference signal level which is the output of the level setting circuit 2 (output of the digital/analog conversion circuit 24), the video signal is compared with the reference signal level. Determine the vertical relationship with the signal level.

The result is input to the level determining circuit 22, where it is compared with the previous level stored in the level memory 23 and stored in the level memory 23 again.

Furthermore, this level is converted to an analog level by a digital/analog (D/A) conversion circuit 24, and is inputted to the analog/digital conversion circuit 3 as a reference signal level.

Using this reference signal level as a threshold, the analog/digital conversion circuit 3 converts the video signal output from the photoelectric converter 1 into a digital signal and outputs the digital signal to the image recognition device 5.

When reading the C-D portion of the form shown in FIG. and scanning line S- between scanning area C-D.
When S reaches the scanning division line EF, the level setting control circuit 53 sends a stop signal CLMP to the level determining circuit 22 to instruct it to stop changing the reference signal level.

This signal causes the level determining circuit 22 to stop changing the reference signal level.

Then, when the scanning line reaches the scanning dividing line GH, the stop signal is released.

Therefore, as shown in Figure 5, the relationship between the reference signal level and the video signal level is an fb1 diagram in which the reference signal level does not change between E-F and GH, and the reference signal level changes in other scanning areas. (a).

To explain using the signal timing chart of FIG. 2, the timing controller 4 determines the effective range from which the scanning line takes out the signal of the form using the horizontal gate signal H, and samples the pixel signal of the video signal VD using the video clock signal VCL.

In FIG. 2, signals from pixels 1 to 2048 of the scanning line are read by the horizontal gate signal H;
and pixel 1800, the reference signal level is fixed and read by the stop signal CLMP.

In Figure 4, the analog/digital conversion circuit 3
To explain digital conversion, the reference signal level, that is, the white level shown by the dotted line, is set to 0, and as the analog density increases, the level decreases, and the density level tone is changed to 16 tones, that is, 4
Expressed in bits, the white level is 0 level, and the maximum density, that is, the black level, is F level, and in the figure, level 6 and level 8.
Shows level concentration.

Binarization of character data is performed at this stage, or after output, it is performed in a subsequent device.

The level at which the reference signal level is fixed by the stop signal, that is, the white level in the figure, may be fixed by selecting one of a plurality of density gradation levels determined by the apparatus.

Furthermore, in the scanning areas EF and GH, each scanning line may be set not at the reference signal level immediately before it, but at a preset level, or at a level immediately before the scanning area of the first scanning line.

〔Effect of the invention〕

As described above, according to the present invention, the reference signal level is changed to follow the medium surface level in the character scanning area of the scanning line, and is fixed in the image scanning area to accurately read out the halftone image. This is an image data manual system of an image input device suitable for a character recognition device equipped with a human image function or an image processing device equipped with an appropriate character input function, and is extremely useful in practice.

[Brief explanation of the drawing]

Figure 1 is a configuration block diagram of an embodiment of the image data input method of the present invention, Figure 2 is a signal timing chart, Figure 3 is a diagram explaining a form, and Figure 4 is an explanation of analog/digital conversion. 5 is a diagram for explaining signal levels, and FIG. 6 is a block diagram of a conventional example. In the figure, l is a photoelectric converter, 2 is a level setting circuit, 3 is an analog/digital (A/D) conversion circuit, 4 is a timing controller, 5 is an image processing device, 10 is an image input device, 51.53 is a level This is a setting control circuit. To the castle of Honkou B-Sangshi Zhao Yi'10. , 7i Figure 1 VD = ℃
No. 8/17 Letter > 7 "° 1000↑-t Figure 2 A/D Suspicious staff, qt > Imperial Decree Figure 4

Claims (2)

[Claims] (1) Optically scan an image recorded on a recording medium,
The photoelectric converter (1) sequentially photoelectrically converts the analog signal output by the photoelectric converter (1), using the reference signal level generated by the level setting circuit (2) following the medium surface level as a threshold. , analog/digital conversion circuit (3
) for converting the data into digital signals and outputting digital data of pixels constituting the image.
), comprising means for fixing the reference signal level in a preset scanning area of one scanning line in which the image is scanned, to a level immediately before the scanning area. (2) The image data input method according to claim 1, wherein the level fixed immediately before the scanning area is one level selected from a plurality of preset levels.