JPS6348962A - Image reading device - Google Patents

Abstract

PURPOSE:To control a period to apply automatic density adjusting to a video signal in a main scanning direction by removing a peak value from a holding means only in the period of the length detected by a detecting means and applying the automatic density adjusting of an electric signal. CONSTITUTION:An original presence absence detecting circuit 24, detects the length of the main scanning direction of an original 22, and in accordance with when the original 22 is not set to a prescribed position or it is not set, outputs respectively 0 and 1 level signals to a signal line. The output signal inputs through an inverter circuit 26 to a delaying circuit 28 and executes the delaying until the original 22 arrives at an original reading position. The original presence absence sensor of the detecting circuit 24 is arranged at a constant interval in the main scanning direction of the original 22, the length of the main scanning direction of the original 22, the peak value of the electric signal is removed from the holding means only during the period of the length and an automatic density adjustment is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Use of Bone IF] The present invention relates to an image reading device, and particularly to an image reading device having a function of automatically adjusting density.

[Conventional technology]

Conventionally, in an image reading device such as a facsimile, the threshold value for binarizing the image signal obtained by scanning is determined by detecting the background density of the original and based on the detected value, and the threshold is determined based on the detected value. is being implemented. Auto Back allows the binarization operation to be performed using the threshold value corresponding to each document.
It is called round control.

The detection area of this background density was determined in advance.

Original size and its A when using a conventional image reading device
auto Background Control (
FIG. 4 shows an example of the width of the background detection area (hereinafter referred to as ABC).

In FIG. 4, in the case of a document of A5 size or A4 size, that is, A4 size or smaller, the area (A), which is a slightly narrower area than the width of A5 size, can be considered as the background detection width of ABC. Further, in the case of a document of B4 size, that is, larger than A4 size and smaller than B4 size, the area (a), which is a little narrower than the width of F4 size, is considered as the background detection width of ABC.

^5 FIG. 5 shows an example of reading an original such as a blue print that is smaller than an original. In this case, as in the conventional example, ABC based on the background detection operation has the drawback that the read image becomes eyelid-black.

This is because the background detection is performed from the position where there is no original, so for example, if the position where there is no original is a pure white reference plate, that reference plate will be detected as the background of the original, which is 60% of the peak value of all white. Binarization will be performed at a certain level.

Therefore, a blue-printed original will be read as completely black.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to eliminate the above-mentioned conventional drawbacks and detect the actual length of the set document in the main scanning direction. An object of the present invention is to provide an image reading device that controls a period during which automatic density adjustment is applied to a video signal of a certain direction.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides an image processing system having a means for reading a document and converting it into an electric signal, and a means for automatically adjusting the density of Denki No. 48. In the reading device,
a detection means for detecting the length of the document in the main scanning direction; a holding means for holding the peak value of the electrical signal; and a peak value is retrieved from the holding means only within the period of the length detected by the detection means. and means for automatically adjusting the density of the electrical signal.

(Function) According to the present invention, it is possible to detect the length of the document in the main scanning direction and perform automatic density adjustment commensurate with the scanning reading period.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is an explanatory diagram showing one embodiment of an image reading device according to the present invention.

In FIG. 1, reference numeral 2 designates a white board as a reference, and the surface of the reference white board on the side of the shaded area is white.

4 is a fluorescent lamp, 6 is a document, and 8 is a document sensor (hereinafter referred to as DS) that detects whether or not a document is set.
It is. Reference numeral 14 designates a reflecting mirror, 16 a fluorescent lamp, a shading plate for mechanically correcting variations in the light amount distribution of lenses, 18 a lens, and 20 an image sensor. In this embodiment, a CCD is considered. The output signal of the CCO is
It is output to the signal line 20a.

If no original is set on the DS8, a signal with a signal level of "0" is output to the signal line 8a, and if an original is set on the DS8, a signal with a signal level of "0" is output to the signal line 8a. 1” signal is output.

Reference numeral 10 denotes a document edge sensor (hereinafter referred to as DES) that detects the leading edge of the document, and when no document is set on the DESIO, it outputs a signal of signal level "0" to the signal line 10a, and the DESIO When an original is set on the
” signal is output.

Reference numeral 12 denotes a detection circuit for detecting the length of the original in the main scanning direction, and applies ABC to a length slightly shorter than the length of the original in the main scanning direction.

Figure 2 (A) and Figure 2 (B) show the detection circuit and explanatory diagram for detecting a length slightly shorter than the length of the original in the main scanning direction.
Illustrated in

In FIG. 2(^), 22 is a document, and 24 is a document presence detection circuit used to recognize the length of the document in the main scanning direction. When the original 22 is set at that position, the original presence/absence detection circuit 24 outputs a signal level "" to the signal line 24a.
If there is no document at that position, a signal with a signal level of "1" is output to the signal line 24a. 26 is an inverter circuit, and the signal line 24a is connected to the signal line 26a.
The inverted signal of the signal output to is output. 2
Reference numeral 8 denotes a delay circuit that delays the original 22 until it reaches the original reading position.

FIG. 2(B) is an explanatory diagram of FIG. 2(A) viewed from above. Here, 30 is a document table. The document presence/absence sensors of the document presence/absence detection circuit 24 are arranged at regular intervals in the main scanning direction of the document 22, as shown in FIG. By sampling the output signal from the document presence detection circuit 24, it is possible to create a signal that is active for a period shorter than the main scanning direction of the document.

FIG. 3 is a block diagram showing one embodiment of the present invention.

In FIG. 3, 32 is a circuit that generates various timing pulses, and the timing circuit 32 sends transfer pulses φ1. φ2. Shift pulse SH, reset pulse R5, and sampling pulse φ5. While the dark time output is being output, a DC reproduction signal VREF that becomes active is output.

34 is a drive circuit that converts a pulse generated at the c2yos or TTL level to a level that can drive the CCD and supplies the pulse to the COD.

36 is an amplifier circuit that increases the gain of the COD output (signal on the signal line 20a), and the signal line 36a has an amplified C
A CD output signal is output.

38 is a sample and hold circuit, and the signal line 36
The signals output to a include signals other than the image signal (optical signal), such as a reset signal and a dark output signal, so the data can be output at the timing when the image signal (optical signal) is output. This is a sample-and-hold circuit that samples and holds the sample, and only analog optical signal components are output to the signal line 38a.

Reference numeral 40 denotes a DC regeneration circuit that corrects the DC component of the signal being output to the signal line 38a so that the dark output level comes to ground, and the DC regenerated waveform is output to the signal line 40a.

42 is AB for the waveform output to the signal line 40a.
C is a peak hold circuit that holds the peak value in the section where signal line 12a is on (signal level "1");
The peak value of the waveform in the section where BC is on is output to the signal line 42a.

Reference numeral 44 denotes an absolute white background detection circuit. For example, when an all-black original is inserted, the signal level output to the signal line 42a becomes "0", making it impossible to read the all-black original. For this reason, take the peak value of the data in the section other than the original, that is, the standard white board, and, for example,
The percentage is output to the signal line 44a. By doing this, it becomes possible to read the original with all black information.

46 is a voltage dividing circuit, and AB outputted to the signal line 42a.
A signal with a higher level of about 40% of the peak value of section C or the peak value of the entire reading area outputted to the signal line 44a is manually input, and a signal of about 60% of that signal is sent to the signal line 46.
Output to a and create a slice level.

48 is a voltage comparison circuit which inputs the video waveform after direct current reproduction outputted to the signal line 40a and the slice level outputted to the signal line 46a and performs binarization, and the signal level of the signal line 40a is , when the signal level is higher than the signal level of the signal line 45a, that is, it is a white signal, the signal line 48
A signal with a signal level "rO" is output to a. Also,
When the signal level of the signal line 40a is lower than the signal level of the signal line 45a, that is, it is a black signal, the signal line 18
A signal with a signal level of "1" is output to a.

Reference numeral 50 denotes a signal processing circuit that inputs the binarized signal output to the signal line 48a and performs various signal processing.

As described above, the signal level of the signal line 12a becomes "1" in a section slightly shorter than the length of the document in the main scanning direction. For this reason,
In that section, it became possible to use 8 BC.

Further, the present invention can change the ABC width in accordance with the length of the original in the main scanning direction even for an original whose length in the main scanning direction changes.

(Effects of the Invention) As is clear from the above, according to the present invention, it is possible to clearly read a blue-printed original or the like which is smaller than the minimum original width.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of an image reading device to which the present invention is applied. FIG. 2 (A) and FIG. 2 (8) are examples of detecting the length of a document in the main scanning direction according to the present invention. FIG. 3 is a block diagram showing an embodiment of the present invention. FIG. 4 is an explanatory diagram showing an example of document size and its ABC width when using a conventional image reading device. FIG. 5 is a timing diagram showing the case of reading a blue-printed original whose width is smaller than A5 size. 2... Reference white board, 4... Fluorescent lamp, 6... Document, 8... Document sensor (O5), lO... Document edge sensor (DES), 12... Main scanning direction of document Length detection circuit, 14... Reflection mirror, 16... Shading plate, 18... Lens, 20... Image sensor, 22... Document, 24... Original presence/absence detection circuit, 26. ... Inverter circuit, 28 ... Delay circuit, 30 ... Original table, 32 ... Timing circuit, 34 ... Drive circuit, 36 ... Amplification circuit, 38 ... Sample and hold circuit, 40 ...DC regeneration circuit, 42...Peak hold circuit, 44...Absolute white background detection circuit, 46...Voltage dividing circuit, 48-...Voltage comparison circuit, 50...Signal processing circuit.

Claims (1)

[Scope of Claims] An image reading device comprising means for reading an original and converting it into an electrical signal, and means for automatically adjusting the density of the electrical signal, comprising: a detection means for detecting the length of the original in the main scanning direction. and a holding means for holding the peak value of the electric signal, and automatic concentration adjustment of the electric signal by extracting the peak value from the holding means only within a period of length detected by the detection means. An image reading device characterized by comprising: means.