JPS5967773A - Original reader - Google Patents

Abstract

PURPOSE:To obtain an excellent reproducing picture to an original having intermediate tone, by providing a part of reference color to a part of an effective reading area of an image pickup element, adjusting the irradiated light amount to the original so that a reference color picture signal level is made coincident with a predetermined reference signal level for obtaining a photoelectric converting signal of a prescribed level at all times. CONSTITUTION:A light reflected from a white color coating section 11 is formed on an image pickup element 5 through a condenser lens 4 and a photoelectrically converted signal is amplified at an amplifier 6. The signal is converted into a digital signal at an A/D converter 7, inputted to a microcomputer 12, and the size of a picture signal level L' obtained from the white color coating section 11 and a reference signal level L are discriminated. When it is discriminated that the luminous amount is small, the lighting time of a fluorescent lamp 2 is extended by one clock's share. That is, the irradiated light to the original 3 from the fluorescent lamp 2 is increased. When the luminous amount is large on the contrary, the lighting time width of the fluorescent lamp 2 is shortened and the irradiated luminous amount to the original 3 from the fluorescent lamp 2 is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to light intensity adjustment of a document reading device that reads image information of a document as an electrical signal by scanning the surface of the document using an image pickup device consisting of a charge storage type photoelectric conversion element or the like. It is something.

2. Prior Art A conventional reading device of this type includes one shown in FIG. 1, for example.

In the figure, 1 is a lighting circuit, 1 is a document illumination light whose blinking is controlled by the lighting circuit 1, 3 is a document to be read, 1 is a condenser lens, and ! 1 is an image sensor, 7 is an image signal amplifier, 7 is a converter, and 2 is an automatic gain control circuit (AGC). Pixel information of the document irradiated by the fluorescent lamp is imaged on the light receiving surface of the image sensor j by a condensing lens. The imaged pixel information is photoelectrically converted and extracted as an image signal, which is then amplified by an amplifier (B). Further, after being digitized by the φ converter 7, fluctuations in the signal output level are corrected by the automatic gain control circuit 1, and the photoelectric conversion signal level is kept constant and outputted sequentially.

Here, in photoelectrically converting the surface of the document, the signal output level depends on fluctuations in the brightness of the fluorescent lamp, IQ, differences in the background density of the surface, or the jet nl of the amplifier circuit.
It varies greatly depending on the degree of change. The automatic gain control circuit r is used to correct this variation in signal output level, and detects the background density of the document surface, that is, the white area of the original itself, and outputs a signal based on the signal level of this white area. This is to keep level fluctuations at a constant value. In other words, in the case of normal I, there is a white part in every scanning line, and the signal level is the same in that part, and if the signal level of this part is taken as the maximum value of the photoelectric conversion signal, then , the level is constant, so the above-mentioned correction can be realized based on this value.

However, in originals that have halftones all over the surface, such as photographs, there is no background part (white area) that serves as a reference like in ordinary document originals, so the maximum value of the photoelectric conversion signal differs for each scanning line. There is a fear. Therefore, when the level of the photoelectric conversion signal is corrected using the conventional method, the density of the reproduced image partially changes, and faithful halftones may not be reproduced.

Therefore, for originals such as photographs, it is necessary to keep the amplification of the photoelectric conversion signal constant while reading the original. If there is a change in the amount of light caused by this, the level of the photoelectric conversion signal of the entire document will fluctuate, making it impossible to reproduce a good image.

Purpose The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, provide a white background part as a reference in a part of the effective reading area of the image sensor, and set the level of the photoelectric conversion signal obtained from this part to a predetermined level. The amount of light irradiated to the original is adjusted based on the comparison result with the reference signal level, so that a photoelectric conversion signal of a constant level can always be obtained even for originals whose entire surface has halftones, such as photographs. The object of the present invention is to provide an original reading device that can obtain good reproduced images.

Example The present invention will be described in detail below with reference to the drawings.

FIG. 2 shows the original 4R16 reading system and writing system in a laser beam printer to which the present invention is applied.

Here, in the document reading system lθ, /l is a white painted part in the effective reading area of the image sensor 3, for example, disposed on the document holding member, for obtaining a read signal, and 12 is a white painted part for obtaining a read signal, and 12 is a comparison between the reference signal and the read signal. /3 is a counter that calculates the number of clock pulses CK, /g is a counter that calculates the number of clock pulses CK, and /3 receives the count from the counter 13 and the calculation result from the microcomputer /λ at input terminals A and B, respectively, as described later. This is a comparator that compares the magnitude of both values. /3 is a flip-flop whose input end is supplied with a comparison output from the comparator /4', and whose output end Q sends a control signal to the lighting circuit l. Next, in the writing system, 〃 is a position detection element for laser light, n is a photoreceptor for forming an electrostatic latent image, katana is a laser oscillator, 2 is a laser beam emitted from laser oscillator n, B 26 is a rotating polygon mirror for scanning a laser beam 24I on the photoreceptor n, and a photoelectric conversion device 26 is for converting a photodetection signal into an electric signal and sending it to the reading system lθ.

Under such a configuration, the photoelectric conversion signal level of the white painted portion // is compared with a reference signal due to a change in the light amount of the fluorescent lamp 2, and calculations are performed to control the duration of illumination of the document by the fluorescent lamp, Furthermore, by synchronizing the lighting cycle of the fluorescent lamp with the one-line scanning cycle of the writing system, the amount of light irradiated onto the original 3 can be controlled.
It is something that exercises control. A detailed explanation will be given below.

Microcomputer/2 output capo) Initial value n to PO
1 and set the initial value O to counter/3 (Cn>0),
Input the reset signal RE8 to the microcomputer/2. This allows the microcomputer/! The operation of each part starts under the control of In the comparator/g, input terminal A
A comparison is made of the values (4) and (B) supplied via and B. Now, (A) −0, (B) −n, so (
It is determined that A) < (B), and the comparator output becomes high level. As a result, the fluorescent light is turned on under the control of the lighting circuit, and the light is turned on.

The light reflected from the white painted portion // forms an image on an image sensor j through a condensing lens l, and the signal converted into light 1 is amplified by an amplifier B.

Thereafter, the signal is converted into a digital signal by the converter 7 and input to the microcomputer/2. Here, the white reference signal level L is set as (000/) in the programmer, and the magnitude of the image signal level L' obtained from the white painted part // and the reference signal level L is determined as described above. . For example, if the image signal level is L' (001O), the light J
' = k is determined to be small, and in this case, the value n preset in the output port (PO) is
is added to (n+/), and this value is sent to the comparator l.
Output to II. As a result, the output of the converter becomes low level when the value (A) supplied via the input terminal A, that is, the count value of the clock pulse CK reaches (n+/). The lighting time of the fluorescent pair λ is increased by /clock. That is, the fluorescence pair λ
The amount of light irradiated to the source 0%3 increases. Below, 111
The same operation as the primary one is performed, and the image signal level L' becomes (000
/) Microcomputer until it becomes /! Node Capo)
The value of PO is increased by l.

Conversely, if the amount of light is large, that is, the image signal level L'
If is (oooo), a value (n-/) obtained by subtracting / from the initial setting value n is output to the comparator pufferfish. As a result, the lighting time width of the fluorescent pair becomes shorter, and the amount of light irradiated onto the document 3 by the fluorescent pair decreases.

Next, the operation of the write system configured to generate the horizontal synchronization signal @Hsync will be explained. This writing system
is an optical scanning device that uses a laser as a light source for optical recording, and is configured to irradiate the laser light onto a photoreceptor through an optical system such as a lens and a light deflection element to form a beam spot. The above-mentioned single image signal of the reading system /θ is input to the laser oscillator blade and converted into a laser beam 21 according to the image signal. This laser beam 2II is reflected by the rotating polygonal mirror and forms a beam spot on the 4 (column n).Here, the beam spot passes through the laser beam detection and the +8 element 2/ for every -line scan. So fI'
q is formed, and the optical signal detected by the detection twin, 2/ is converted into a trigger pulse by a photoelectric conversion device ζ1°,
Input of counter /3 in reading system /θ as horizontal synchronization signal 11sync! /1IllLD. Counter/3 is fit due to the arrival of this ID number H8yne.
kt value is reset to 0 and clock pulse CK'
tNle'( starts again from 0, i.e. the counter /
Iil value of 3 and output cap of microcomputer 12
) The magnitude determination with respect to the value of PO is performed at the cycle of this signal Hsync.

The above operation is repeated to determine the lighting time width of the fluorescent pair. j adjustment is performed by numerical control of the output capo) PO, and the lighting period is synchronized with the horizontal synchronization signal Hsyne, so that the white pixel signal level L' becomes NO! It is controlled to be at the same level as the quasi-signal level L.

In the above-mentioned embodiment, the light amount was controlled by using a combination of a microcomputer and peripheral elements, but it is of course possible to control the amount of light by using a microcomputer alone. In this case, in FIG. 1, the output of the microcomputer/2 is directly supplied to the lighting circuit l, and the counter/3. Comparator pufferfish and flip-flop/
The operation achieved by S may be written in the ROM of the microcomputer/2 as a program, and the ig-r may be configured to control the lighting time width in accordance with the period of the horizontal synchronizing signal f'LBync.

Furthermore, in this embodiment, the signal level is corrected based on the image signal obtained from the white painted portion l/.
This is not limited to a white painted part, but may be a painted part of another color, and in that case, the reference signal level L to be compared may be changed to a corresponding level.

Effects As explained above, according to the present invention, a reference color portion is provided in a part of the effective reading area of the image sensor, and the reference color pixel signal level obtained from this portion is made to match the predetermined reference signal level. So, 1 to Haraina! (Since the amount of light emitted is adjusted, it is possible to always obtain a constant level of light T? and conversion signal, and it is possible to obtain good reproduction of H7i images even for originals that have halftones on the entire surface, such as photocopy tools.) can be obtained.

Furthermore, in this embodiment, the amount of light irradiated to the original is adjusted by increasing or decreasing the irradiation time to the original (7,), and the increase or decrease in the irradiation time is adjusted every l line scanning period of the writing system. By doing this, it is possible to reliably achieve the 1゛1coat level of Hikari'jib U exchange No. 13.

4.1.4 Explanation of surface no. An example of the system is shown (11/ diagram).

l...Lighting circuit, 2...Hokkaido, 3... Manuscript, G... condensing lens, ! ...imaging device, ≦...Amplifier, 7... A/D converter, And... automatic gain control mode 11 (circuit, /θ...reading system, //...white painted part, /λ...microcomputer, /3...Counter, /G... comparator, lS...Flip-flop, 〃...Writing thread, 〃...Laser light detection element, n...photoreceptor, 3...Laser oscillator, Nori...laser beam, Δ...Rotating polygon mirror, Bu...photoelectric conversion device υ.

Patent applicant: Canon Co., Ltd.

Claims (1)

[Scope of Claims] /) In a document reading device in which image information of an exposed document is read as an electrical signal by an imaging device, a reference color portion formed in an effective reading area by the imaging device and read by the imaging device is provided. 1. A document reading device comprising: control means for controlling exposure light onto the document so that the image signal level of the reference color portion thus obtained coincides with a predetermined reference signal level. λ) The apparatus according to claim 1, further comprising a writing means for scanning a photoconductor to form an electrostatic latent image based on an image signal of the document read by the imaging means, A document reading device characterized in that the control means controls an exposure time width of the document in synchronization with a one-line scanning period of the writing device.