JPH0782529B2 - Character scanning device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character scanning device, and more particularly to a character scanning device that scans characters and patterns at high speed.

[Conventional technology]

Conventionally, in this type of character scanning device, a one-dimensional image sensor has been used as a means for electrically converting a character / pattern on a running form into a two-dimensional image signal.

The commercially available one-dimensional image sensor has a limitation in the number of pixels and scanning speed, and is a method of arranging a plurality of one-dimensional image sensors in series in order to realize a wide area, high resolution and high-speed processing. Has been taken. The resolution of the video signal is vertical and horizontal, that is,
The one-dimensional image sensor is divided into a scanning direction (hereinafter referred to as a main scanning direction) and a document conveyance direction (hereinafter referred to as a sub scanning direction). The former is given by the scanning area and the number of pixels of the image sensor covering the scanning area, and the latter is given by the repetition time of the main scanning and the conveyance speed of the form. These relationships are shown by the following equation.

Resolution in the main scanning direction: Rv = S / P Resolution in the sub-scanning direction: Rt = tv where S is the scanning area, P is the number of pixels, t is the time required for one main scanning, and v is the conveyance of the form. It's speed.

Under the condition that the form is conveyed at a high speed, in order to obtain a video signal having a wide scanning area and a high resolution, the time required for one scanning is shortened in the resolution in the main scanning direction. That is, it is necessary to make the reading speed per pixel as high as possible.

FIG. 3 shows an example in which one-dimensional image sensors are used in series.

In FIG. 3, 31 is a form, 32, 33 and 34 are condenser lenses, a, b and c.
Is a one-dimensional image sensor. The light source is omitted in FIG. The image sensor a scans between A and B on the form and the image sensor b scans B and C on the form.
The image sensor c scans between C and D on the form. The number of pixels scanned between A and D on the form is the sum of the number of pixels of each one-dimensional image sensor. On the other hand, the time required to scan between A and D depends on the image sensor a, b, c
Are simultaneously scanned, which corresponds to the time for scanning between A and B. That is, the scanning time per scan is apparently shortened to 1/3. As a result, the character scanning device of FIG. 3 realizes wide area, high resolution and high speed processing.

[Problems to be Solved by the Invention]

The above-described conventional character scanning device has the following problems in extracting the video signal at the boundary of the one-dimensional image sensor.

In the AD (Analog / Digital) converter that is a means of quantizing the analog signal output by the image sensor, when the reference signal that sets the paper surface level is a follow-up type (envelope detection method) for the video signal, If the characters / patterns on the form exist at the boundary of the image sensor, there is a problem that the characters / patterns at the scanning start point of the image sensor disappear. FIG. 4 shows a specific example.

In FIG. 4, 41 is a scanning area of the image sensors a and b, 42 is an example of a figure in the area, and 43 and 44 are AD converters of the image sensors a and b. 3 shows an input waveform input to.

S3 and S5 are video signals, S2 and S4 are reference signals that follow the video signals, and in the figure S1 on the form, there is a potential difference between the video signal of the image sensor a and the reference signal (T1 portion in 43). As the output of the converter,
Can be extracted as a figure. However, since there is no potential difference between the video signal of the image sensor b and the reference signal (T2 portion in 44), the character disappears as the output of the AD converter. The output of the AD converter at this time is shown in 45. At 45, the graphic at the boundary between the image sensors a and b is output as in S6.

[Means for Solving the Problems]

In order to solve the above problems, the present invention provides an electric signal obtained by scanning a paper surface in the same direction at the same time by a plurality of one-dimensional image sensors arranged in series, and an envelope curve following the electric signal. In the character scanning device for detecting the pattern on the paper surface based on the level, the means for holding the envelope level at the end of one scan of the first image sensor, and the held envelope level as the first A second image sensor adjacent to the image sensor in the scanning direction is used as an initial value of the envelope level of the electric signal.

[Action]

The character scanning device of the present invention has a solution shown in FIG. 5 in order to prevent the disappearance of the character / pattern when the character / pattern to be scanned is present at the boundary of the image sensors arranged in series. The solution means shown in FIG. 5 will be described below.

In FIG. 5, reference numeral 51 indicates a scanning area of the image sensors a and b, and 52 indicates an example of a figure in the area. Reference numerals 53 and 54 show input waveforms input to the respective AD converters in the image sensors a and b.

S10 and S13 are video signals, and S9 and S12 are reference signals. Reference signal of the image sensor a shown in 53
The level of S9 is stored at the time of S8 (at the end of the scanning of the image sensor a) and injected at the time of S11 of the reference signal S12 of the image sensor b shown at 54 (before the start of the scanning of the image sensor b). As a result, when the figure S7 on the form of 52 existing in the scanning area of each image sensor shown by 51 is scanned, the output of the AD converter shown by 55 is S1
As 4, the figure corresponding to S7 can be extracted.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a timing chart showing the operation of the character scanning device of FIG.

In FIG. 1, 1 is a form, 2 is a light source, 3-5 are photoelectric conversion units including a one-dimensional image sensor, 6-8 are analog switches, 9-11 are envelope detection circuits, and 12-14 are peak hold ( A level holding circuit, 15 is an initial value injection control signal generating circuit, 16 is a level holding control signal generating circuit, and 17 to 19 are AD converters 20 having initial values.

In the character scanning device of the present invention, the form 1 is illuminated by the light source 2 and the reflected light is incident on the photoelectric conversion units 3 to 5. The photoelectric conversion units 3 to 5 convert optical signals into electric signals, and envelope detection circuits 9 to 11 and AD converters 17 to 19 respectively.
Output to. The envelope detection circuits 9 to 11 create the reference signals of the AD converters 17 to 19 described above. With this circuit,
When creating the reference signal, analog switch 6 ~
8 and the peak hold circuits 12-14 are involved.

Hereinafter, description will be made with reference to FIG.

In FIG. 2, reference numerals 21, 22, 23 denote photoelectric conversion units 3 to 3 in FIG.
5 shows the input waveforms input to the AD converters 17 to 19 from 5 (using the one-dimensional image sensors ac of FIG. 3). L1, L3, L5 are video signals, L2, L4, L6 are
It is a reference signal. Reference numeral 24 is an initial value injection signal created at 15 in FIG. 1, and 25 is a level holding signal created at 16. Incidentally, the signal of 24 is generated within the period before the image sensor starts one scan (portion P2 in 21), and the signal of 25 is generated at the end of one scan of the image sensor. P1 is 1
The scanning period is shown. That is, it is a period during which the pixels of the image sensor are being read. V ₁ indicates the first pixel, and V _n indicates the last pixel. P2 is the blanking period. That is, it is a period during which no video signal is output.

The reference signal in the photoelectric conversion unit 3 is held by the line l3 in the peak hold circuit 12 in FIG. 1 at the timing of the level holding signal 25 (generated in FIG. 16 in FIG. 1). Then, at the timing of the initial value injection signal 24 (generated in the first 15), the analog switches 6 of FIG. 1 operates, with respect to the envelope detection circuit 9 initial value 20 is the line l _1, l ₂ Is output. Since the photoelectric conversion unit 3 has no adjacent photoelectric conversion unit in the scanning start direction, the virtual value is set to 20 as an initial value.
The envelope detection circuit 9 is injected.

The reference signal in the photoelectric conversion unit 4 is the peak hold circuit 13 shown in FIG.
Held by line l ₆ . Similarly, the reference signal in the photoelectric conversion unit 5 is held in the peak hold 14 by the line l ₉ .

Next, the level held in the peak hold circuit 12 in FIG. 1 is passed through l ₄ and l ₅ by the operation of the analog switch 7 in FIG. 1 at the timing of the initial value injection signal 24 in FIG. Then, it is injected into the envelope detection circuit 10. That is, as the reference signal at the timing of the initial value injection signal 24 of the photoelectric conversion unit 4, the reference signal at the timing of the level holding signal 25 of the photoelectric conversion unit 3 is injected. Similarly, the level held by the peak hold circuit 13 of FIG. 1 is operated by the analog switch 8 of FIG. 1 at the timing of the initial value injection signal 24 of FIG.
It is injected into the envelope detection circuit 11 via l ₇ and l ₈ . That is, as the reference signal at the timing of the initial value injection signal 24 of the photoelectric conversion unit 5, the reference signal at the timing of the level holding signal 25 of the photoelectric conversion unit 4 is injected.

The level held by the peak hold circuit 14 in FIG.
This circuit is not used because there is no photoelectric conversion unit adjacent to the photoelectric conversion unit 5 in the scanning end direction.

As the circuit configuration, the above-described operation is performed for each scan of each image sensor.

Also, the reference signal generated by the envelope detection circuit 9-11 in the first figure, AD converter by the line l ₁₀ to l ₁₂ 17
Output to ~ 19.

〔The invention's effect〕

As described above, according to the present invention, the electric signals output from the respective image sensors arranged in series are envelope-detected, the detection signal at the end of one scan is stored, and the adjacent images in the scan end direction are stored. By injecting before one scan of the sensor, there is an effect that the character / pattern existing on the boundary of the image sensor can be faithfully extracted.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG.
3 is a timing chart showing the operation of the character scanning device shown in FIG. 3, FIG. 3 is a diagram showing a state in which a plurality of one-dimensional image sensors are used in series, and FIG. 4 is a diagram showing a plurality of one-dimensional image sensors used in series. FIG. 5 is a diagram showing a problem in this case, and FIG. 5 is a diagram showing a means for solving the problem when a plurality of one-dimensional image sensors are used in series. 1 ... form, 2 ... light source, 3 ... photoelectric conversion part a, 4 ...
Photoelectric conversion part b, 5 ... Photoelectric conversion part c, 6-8 ... Analog switch, 9-11 ... Envelope detection circuit, 12-14 ... Peak hold circuit, 15 ... Initial value injection control signal generation circuit , 16 …… Level hold control signal generator, 17〜19 …… AD
converter.

Claims (1)

[Claims] 1. A paper surface is simultaneously scanned in the same direction by a plurality of one-dimensional image sensors arranged in series, and based on the obtained electric signal and an envelope level following the electric signal, the paper surface is printed. And a means for holding the envelope level at the end of one scan of the first image sensor, and the held envelope level in the scanning direction with respect to the first image sensor. A means for setting an initial value of an envelope level of an electric signal obtained by an adjacent second image sensor.