JPS6388963A - Original reader - Google Patents

Abstract

PURPOSE:To execute the inclination correction even to an original to be read, which is obliquely travelled, without fail by detecting the edge of the original to be read, arranging the detecting edge and storing a reading signal to a memory means. CONSTITUTION:Since the difference occurs at a density level for an original part and a non-original part in reading and scanning by a reader 15, a level detecting part 41 detects a level difference between original edges 31 and 32 of an original. When the detecting part 41 detects the original edge 31, an original edge detecting signal 42 goes to 'L', a clock is supplied to a memory 23 and the memory writing of a picture signal 26 is started. By the edge where the original edge detecting signal 42 is transited from 'H' to 'L', the output of an FF 44, namely, a stopping signal 43 comes to be effective and the level detecting part 41 stops an action.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for correcting image distortion caused by skew feeding of a document in a document reading device such as a facsimile machine.

(Prior Art) The configuration of a conventional document reading device of this type will be described using a facsimile device as an example. FIG. 4 shows the external structure, with reference numeral 11 a document guide plate, 12 a document detection sensor,
13//i original self-feeding roller, 16 original ejection roller, 1
4 is a light source, 15 is a reading device such as a CCD, 17 is a reference back plate, and 18 is a reading surface. A soft platen is normally used for the document self-feeding roller 13 and the document discharge roller 16 so that appropriate pressure is evenly applied to the surface of the document.

Next, a method of driving the configurations 11 to 16 described above when reading a document will be described. The operator sets the document guide plate 11 in the paper of the document to be transmitted or copied, and sets the document in the self-feed slot. When the document setting is detected by the document detection sensor 12, the apparatus drives the document self-feeding roller 13 and starts self-feeding the document. When the original reaches the original reading surface 18, the light source 14 is turned on, the reading device 15 is driven, and image input is started. -! Further, the document is ejected by a document ejection row 216.

The document is read through the above-described sequence. Next, a signal processing method for image signals serially taken out from the reading device 15 will be described with reference to FIG. In FIG. 3, 21 is the reflected light from the document surface, 22 is an A/D converter, 23 is a memory for storing binarized images, 27 is an image signal transfer start signal, and 28 is an image signal transfer lock. , 25 is an analog serial image signal, 26 is a binarized image signal, and 24Jl'i is a reading 9 control section that controls the timing of the above-mentioned 27 and 28 and controls writing to the memory 23.

When the image signal transfer start signal 27 is applied to the reading device 15ti, the image signal transfer lock 28 causes the image signal=i A
/ Transfer to the D converter 22. The A/D converter 22 is
At the same clock 28 timing as above, the input image signal is binarized and stored in the memory 23.

The reading device 15 is composed of a certain number of reading elements, and even if a device having a width larger than the largest original of a normal facsimile machine is used, the reading of the original is performed in the above manner.

(Problems to be Solved by the Invention) As explained above, in the above-mentioned apparatus, the image signal transfer lock is the same as the number of reading elements, and skewing of the original is attempted to be prevented only by mechanical methods.

However, there is a drawback that the document may be read diagonally due to slight skew that cannot be prevented by mechanical methods, such as when the operator does not set the document guide plate correctly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a document reading device that can eliminate the above-mentioned drawbacks and correct distortion of an input image caused by skewed document feeding in a document reading section.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes a reading device, and an A/D conversion means for converting an analog read signal read and lost by the reading device from analog to digital and outputting a digital read signal. , a storage means for holding the digital read signal output from the A/D conversion means, and a detecting means for detecting an edge of the read document based on the level of the read signal, and the detecting means. and control means for storing the digital read signal in the storage means based on the detection result obtained by the method.

(Function) In the present invention, the edge of the read document is detected by the detection means,
By aligning the detected edges and storing the read signal in the storage means, it is possible to reliably correct the inclination even for a skewed original to be read.

(Example) Hereinafter, the present invention will be described in detail based on an embodiment of the present invention. FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, numeral 41 is a level detection unit composed of a difference device that calculates the density difference between adjacent pixels, and a comparator that compares the calculated difference with a certain set value. Active °L when the set value is also larger than the set value.
”, the document edge detection signal 43 is the level detection section 42
This is an active "H" detection unit stop signal that stops the operation of the detector.

FIG. 2 is a diagram for explaining the density level of a read image. When read and scanned by the reading device 15, the output is as shown in FIG. 2, and there is a difference in density level between the original portion and the non-original portion. The level detection section 41 detects the level difference between the document edges 31 and 32 of the document.

The operation will be explained below. As in the conventional example, when the document comes at the scanning position i-t, the control unit 24 outputs the image signal transfer start signal 2.
7 and the image signal transfer lock 28 is sent. Here, as in the conventional example, the image signal transfer start signal 27 is an active °L pulse signal generated for each line, and the image signal transfer lock 28 is the 27 image signal transfer start signal 27, which causes the reading device to Image signal transfer is started in synchronization with the signal transfer lock 28. The image signal is the same clock 28, A/
The signal is taken into the D converter 22, binarized, and then sent to the memory 23 and the level detection section 41 in parallel format.

On the other hand, the image signal transfer start signal 27 clears the 7-lip flop 44, cancels the detection unit stop signal 43, and the level detection unit 41 starts level comparison between pixels at the timing of the transfer start point RI28. do.

If an appropriate value is set in the comparator here, the comparator output will be °H'? up to the level change point 31. That is, it is possible to make it undetected.

While the output of the comparator, that is, the document end detection signal 42, is -H-, the image signal transfer lock 28 is not sent to the memory 23 by the AND gate, and the image signal 26 is not written into the memory.

When the level detection section 41 detects the document edge 31, the document edge detection signal 42 becomes 0, a clock is supplied to the memory 23, and writing of the image signal 26 to the memory is started. Also,
When the document edge detection signal 42 transitions from °H'' to -L-, there is a process where the document edge detection signal 42 transitions from °H'' to -L-.

When the output of the switch 44, that is, the stop signal 43 is valid, the level detection section 41 stops operating.

By repeating the above operation for each line, memory 2
It becomes possible to always input the image signal to the document edge at the end of the document.

〔Effect of the invention〕

As explained above and as follows, by applying the present invention, it is possible to store the read signal from the edge of the document in the storage means.
It is possible to correct image distortion caused by skewing or meandering of a document. For example, in the case of a facsimile machine, it is possible to obtain an image in which the edge of the recording paper and the edge of the image are parallel.

Especially in recent years, the skew that occurs in document reading units with precise mechanical systems is extremely small, and if the correction of the present invention is applied to the subsequent image obtained from this, an image without distortion can be obtained. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the density level of a read image, FIG. 3 is a block diagram showing a conventional image reading device, and FIG. 4 is a block diagram showing an example of the present invention. FIG. 3 is a diagram for explaining the operation of reading a document. 11... Original guide plate, 12... Original detection sensor,
13... Original self-feeding roller, 14... Light source, 15...
・Reading device, 16... Original ejection roller, 17...
-Reference back plate, 18... Original reading surface, 21... Reflected light from the original, 22... A/D converter, 23... Memory, 24... Control unit, 25... Image signal (analog), 26... Image signal (digital), 27... Image signal transfer start signal, 28... Image signal transfer lock, 29.
...Memory write signal, 20...Write signal, 31
, 32...Document edge 1 inside≠;-41...Level detection section, 42...(Document edge) detection signal, 43...Stop signal, 44...Clip/70 Tsubu attorney's attorney Ken Nori Chika borrows a question
Yamashita - Figure 4

Claims (1)

[Claims] a reading device, an A/D conversion means for converting an analog read signal read by the reading device from analog to digital and outputting a digital read signal;
In a document reading device comprising a storage means for holding a digital read signal outputted from the conversion means, a detection means for detecting an edge of the read document based on the level of the read signal, and a detection result by the detection means, A document reading apparatus comprising: a control means for storing the digital read signal in the storage means, and performs tilt correction when reading a document.