JP2506643B2 - History correction reader - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading device for a facsimile machine or the like, and more particularly to improving the resolution or scanning speed in the sub-scanning direction even when an image sensor having poor photoresponsiveness is used. The present invention relates to a history correction reader.

2. Description of the Related Art As shown in FIG. 5, a conventional reading device of this type includes an image sensor 1, an amplifier 2, a comparator 3, a lens 4, a light source 5, an original 6 and the like. 6
Is irradiated, and the reflected light forms an image on the image sensor 1 via the lens 4.

On the image sensor 1, so-called photosensitive elements whose electromotive force, resistance value, accumulated charge amount, and the like change according to the amount of light are arranged linearly in one line or a plurality of lines in the main scanning direction. Main scanning is performed by sequentially and electronically switching out photoelectric conversion output signals.

Further, the original 6, the lens 4, or the image sensor 1 is relatively moved by mechanical or optical means to perform sub-scanning.

The photoelectric conversion output signal from the image sensor 1 is guided to the amplifier 2 and amplified, and this is output from the amplifier 2 as a photoelectric conversion output Vs.

The processing mode of the photoelectric conversion output Vs differs depending on the transmission method of the facsimile signal, that is, the analog transmission method or the digital transmission method.

That is, in the case of analog transmission system, photoelectric conversion output
Vs is guided to the modulator as it is, and in the case of a digital transmission system, Vs is quantized via an A / D (analog / digital) converter and, in some cases, further encoded and transmitted.

The conventional example of FIG. 5 shows the case of the digital transmission method, and the A / D conversion is the simplest binarization (1
An example of performing bit quantization) is shown. That is,
In FIG. 5, the photoelectric conversion output Vs is binary-quantized by the reference voltage Vr (slice level) of the comparator 3, and this is output from the output terminal e as a binary-quantized signal.

Explaining this further, when a so-called slow photoresponsive image sensor such as a cds image sensor is used as the image sensor 1, as shown in FIG. 6A, the rise and fall changes of the photoelectric conversion output Vs are Get loose. Therefore, when the scanning cycle is τ, the rising time or the falling time is less than the scanning cycle τ.

Therefore, as shown in FIG. 10A, the slice level is fixed at about 50% and binary quantization is performed.

By such means, the conventional apparatus obtains a binary quantized signal in a state in which almost original image information is held as shown in FIG. 6B.

However, even with this type of conventional means, it takes time to reach the photoelectric conversion output level according to the reflectance of the document due to the slow photoresponse of the image sensor. Therefore, the resolution in the sub-scanning direction is deteriorated or the image quality is deteriorated, or the scanning speed is limited due to the deterioration.

The deterioration of the resolution or the image quality becomes more remarkable as the high speed scanning is performed. A specific example thereof is shown in FIGS. 7A and 7B.

FIGS. 7A and 7B are waveforms corresponding to FIGS. 6A and 6B when the scanning speed is doubled, that is, the scanning period is τ / 2. As is apparent from the figure, in this case, the rise and fall of the photoelectric conversion output for the image information are much worse than when the scanning period is τ, and a thin signal (image information) is lost. Therefore, it can be understood that the binary quantized signal output also has a waveform far from the original image information (see FIG. 6B) as shown in FIG. 7B, and the resolution or the image quality is extremely deteriorated.

Further, from FIGS. 7A and 7B, it is clear that the higher the scanning speed, the finer the signal is lost, and there is a limit to the scanning speed, that is, the original image is scanned unless scanning is performed at a constant scanning period τ. That is, a binary quantized signal output close to information cannot be obtained.

Therefore, the present invention has been made in view of the above-described circumstances, and performs high-speed scanning without degrading the resolution in the sub-scanning direction or the image quality even when an image sensor having poor photoresponsiveness is used. It is an object of the present invention to provide a history correction reading device that can be obtained.

Means for Solving the Problems In order to achieve the above object, the prior history correction reading apparatus of the present invention stores a photoelectric conversion information (image information) of each photosensitive element corresponding to a past scanning line which has already been scanned in a buffer memory. And a weighting of photoelectric conversion (image information) output of each photosensitive element of the current scanning line based on the past image information and the current scanning line information output from the buffer memory. And means.

Operation With the above-described configuration, the photoelectric conversion output of each photosensitive element of the current scanning line is quantized with respect to the photoelectric conversion output level determined based on the past scanning line information and the current scanning line information in the buffer memory. Is done.

Therefore, a binary quantized signal faithful to the original image information can be obtained,
It is possible to improve the resolution or the image quality and the scanning speed.

Example As a method of correcting the history in a reading apparatus such as a facsimile apparatus, a method of controlling a quantization level and a method of controlling an output level are considered.

FIG. 1 is a schematic block diagram of a reader in which a priori correction is executed by controlling a quantization level.
Reference numerals 2, 4, 5, and 6 are the same as those of the constituent members shown in FIG. Reference numeral 11 is an A / D converter for converting analog information from the amplifier 2 into digital information, and 12 is photoelectric conversion information (hereinafter referred to as past scanning line information) of each photosensitive element corresponding to a past scanning line which has already been scanned. .) B and photoelectric conversion information of each photosensitive element corresponding to the current scanning line (hereinafter,
This is called current scan line information. ) A and compare both information a,
Comparator for judging whether b is large or small, 13 is past scanning line information b
A buffer memory circuit (hereinafter, referred to as a storage circuit) for accumulating the current scanning line information a based on a large / small comparison determination output signal (hereinafter, simply referred to as a determination output signal) c from the comparator 12. Binary quantization judgment is performed, and the result of this judgment is
That is, it is a binary encoder that outputs a binary quantized output signal (hereinafter, referred to as a binary quantized signal) d to an output terminal e.

Next, in order to explain the operation, the reflected light of the document 6 emitted by the light source 5 is photoelectrically converted by the image sensor 1 (for example, cds image sensor) through the lens 4 for each photosensitive element, and this is converted into an amplifier 2. After being amplified by, the signal is converted into a digital signal (current scanning line information) a by the A / D converter 11. The signal a is represented by, for example, a 4-bit multivalued digital signal, and can represent 16 gradations per pixel.

Therefore, the digitized current scanning line information a
Is input to the binarization encoder 14 and, of course, is input to the comparator 12 and simultaneously stored in the storage circuit 13.
The current scanning line information a stored in the storage circuit 13 is the past scanning line information b when the next scanning line information is stored.
Used as.

That is, the current scanning line information a is input to the storage circuit 13 and at the same time, the past scanning line information b is input from the storage circuit 13.
Is read out and input to the comparison supply 12.

Here, the comparator 12 makes a comparison determination of the image information a and b, and outputs a determination output signal c, which is the determination result, to the binarized encoder 14.

For example, the value of the determination output signal c is determined by an encoder (not shown) provided inside the comparator 12 when c <1011 (binary value) = 11 when a <b and when c = 10 when a = b.
00 (binary) = 8, and when a> b, c = 0101 (binary) =
5 is output. Then, as shown in Table 1, this judgment output signal c fluctuates up and down depending on the comparison result of both image information a and b, and is a slice for binarizing the current scanning line a. It becomes a level.

That is, when a <b, the determination output signal c (slice level of the binary encoder 14) is determined to be about 69%. When a> b, it is determined to be about 31%.

In the binarized encoder 14, the determination output signal c (slice level) determined in this way
As the binary quantization level of the current scanning line information a input to 14, the information a is binary quantized.

That is, in this embodiment, the slice level (judgment output signal c) sequentially determined by the large / small comparison judgment of the current scanning line information a and the past scanning line information b is set as the quantum of the current scanning line information a. It is a level.

2A and 2B are waveform charts showing the relationship between the change in image information in the sub-scanning direction and the photoelectric conversion output, focusing on a specific photosensitive element.

In FIG. 2, the sampling point that determines the binary quantization is at the dotted line position in the figure. Then, at each sampling point, the scanning line information at the immediately preceding sampling point is compared, and the slice level is sequentially determined.

As is clear from FIGS. 2A and 2B, the slice level moves while following the image information while changing its value (69%, 50%, 31%) at the sampling point. The binary quantized signal output that faithfully reproduces
(See) is obtained.

FIG. 3 is a schematic block diagram showing an embodiment of the present invention in which the history correction is performed by controlling the output level. In FIG. 3, the same parts as those in FIG. 1 are designated by the same reference numerals. 13 is the first
It is a memory circuit as a memory means. Further, in the present embodiment, the calculating means for calculating the output level difference between the past scanning line information and the current scanning line information sequentially read from the storage means 13 for each photosensitive element, and the calculating means Second storage means for storing a plurality of correction data according to the obtained difference amount, and correction data according to the magnitude of the difference amount for each scanning with respect to the photoelectric conversion output signal output from the image sensor. Reference numeral 15 denotes an encoder for comparing the present scanning line information a with the past scanning line information b, and generating the corrected data f by weighting the present scanning line information a according to Table 2.

In this embodiment, the binarization encoder 14 which is a quantizing means is used.
Keep the slice level of binarization in
The current scanning line information a and the past scanning line information b are weighted based on Table 2 and the weighted data (corrected data f) has the constant slice level. The binary encoder 14 performs binary quantization to obtain a binary quantized signal faithful to the original image information from the output terminal e.

More specifically, in the encoder 15, the difference (ab) between changes in the current scanning line information a and the past scanning line information b is observed, and this difference (ab) is 0 or If the value is ± 1, the current scanning line information a is output as it is as the corrected data f. If the difference (ab) ga2 has changed, the value obtained by adding +1 level to the current scanning line information a is output as the corrected data f. That is, the amplification of the image signal is adjusted digitally, and this is output as a signal of the corrected data f.

The binarized encoder 14 determines whether the signal of the corrected data f is greater than or less than the slice level set as the integral value of the encoder 14 and determines whether it is white 1 or black 0, and thus the binary value is obtained. Quantization is performed.

That is, if the current scanning line information a is weighted as shown in Table 2, the photoelectric conversion output shown in FIG.
The corrected image information is output as shown in Fig. 4, and even if the slice level is constant (50%), 2 as shown in Fig. 4B.
The output waveform of the value-quantized signal is obtained.

In FIG. 4A, what is shown by the solid line is the weighted so-called post-correction image information output, and the x mark indicates the value of the post-correction data f at the sampling point. Information is latched. Black marks are sampling points that determine binary quantization before correction. When the difference (ab) has only a change of 0 or ± 1,
The black mark and the X mark appear to overlap.

Further, the output waveform of FIG. 4B is the same as that of FIG. 2B. From this, it can be understood that the same effect as the previous correction by the control of the quantization level can be obtained in this embodiment as well. .

As described above, in this embodiment, as the past scanning line information a,
An example in which only the scan line information immediately before the current scan line information (referred to as previous scan line information) is used has been described, but scanning is performed using further previous scan line information (referred to as pre-previous scan line information). It is also possible to increase the speed and stabilize the operation.

Generally, the effect can be obtained even if the number of scanning lines is increased up to the range where the transient time of the image sensor extends.

Further, although this embodiment has been described with respect to the binary quantization, the present invention is not limited to this, and can be applied to the case of multilevel quantization.

As described above, according to the present invention, one or a plurality of scanning line information is stored in the memory circuit as the past scanning line information within the transient time and range of the image sensor, and the stored information is compared with the current scanning line information. Based on the result, the quantization level is controlled by weighting the current scanning line information. Therefore, the optical response cannot rise or fall to the threshold level within one main scanning period. Even when an image sensor having poor performance is used, high image quality and high scanning speed can be realized with a relatively simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a reading device in which the history correction is executed by controlling the quantization level, FIGS. 2A and 2B are waveform diagrams for explaining the operation of FIG. 1, and FIG. 3 is an implementation of the device of the present invention. A schematic block diagram showing an example, FIGS. 4A and 4B are waveform diagrams for explaining the operation of FIG. 3, FIG. 5 is a schematic block diagram of a conventional reader, and FIGS. 6A and 6B are of FIG. Waveform diagrams for explaining the operation and FIGS. 7A and 7B are waveform diagrams for explaining the problems of FIG. 1 ... Image sensor, 2 ... Amplifier, 4 ... Lens,
5 ... Light source, 6 ... Original, 11 ... A / D converter, 12 ... Comparator, 13 ... Memory circuit, 14 ... Binary encoder, 15 ...
... encoder, a ... current scanning line information, b ... past scanning line information, c ... determination output signal, d ... quantization output signal, e ... output terminal, f ... corrected data.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Kobayashi 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Electric Transport Co., Ltd. (56) Reference JP-A-58-179061 (JP, A) JP 54-146530 (JP, A) Norihiko Fukibuki, "Signal processing of images for FAX / OA", (57-10-20), Nikkan Kogyo Shimbun, page 12, lines 1-5, page 23 2.13 (a)

Claims (1)

(57) [Claims] 1. An optical means for irradiating an original with a light source and condensing reflected light on a photosensitive element through a lens, an image sensor in which the photosensitive elements are arranged in one row or a plurality of rows, and this image sensor. Main scanning means for performing main scanning by sequentially electronically switching photoelectric conversion outputs of the respective photosensitive elements, sub-scanning means for performing sub-scanning by relatively moving the document and the image sensor, and the image. Quantization means for quantizing the photoelectric conversion output signal output from the sensor, first storage means for sequentially storing the photoelectric conversion output signal input to the quantization means, and past read out sequentially from this storage means Computation means for calculating the difference between the output levels of the scanning line information and the current scanning line information for each photosensitive element, and a plurality of correction data according to the difference amount obtained from the computing means. A prior history correction reading apparatus having a second storage unit for storing and a unit for adding correction data according to the magnitude of the difference amount for each scanning to the photoelectric conversion output signal output from the image sensor. .