JPS6053374A - Fluctuation correcting device of light quantity in original reader - Google Patents

Abstract

PURPOSE:To reproduce an original with fidelity by correcting a background level based on an original reading signal when the original is a black-and-white original, deciding a gain based on the light quantity of a light source for illumination when the original is an intermediate tone to correct the level of an original reading signal. CONSTITUTION:The device consists of a light source 7 irradiating light to the original 6, a lens 8 forming the image on a CCD9 photoelectric transducing reflected light, a preamplifier 10 amplifying the output signal of the CCD9, and a switch 14 synthesizing the original reading signal of the preamplifier 10 and the sensor signal of a photo sensor 13 monitoring the light quantity of the light source 7. The output of the sensor 13 is adjusted to a prescribed level by an adjusting circuit 15 having an operational amplifier 16. An amplifier circuit 1 is connected to a control section 3 via a comparator 2. The control section 3 consists of a transistor 17, a switch 18, an operational amplifier 19, and a capacitor 20 or the like and the switches 14 and 18 are controlled by switch control signals 21 and 22.

Description

Detailed Description of the Invention (Technical Field) Misfire nA is a document reading system that accurately reproduces all halftones by determining the gain of the document reading signal level based on the brightness of a light source for illuminating the document when reading a halftone document. The present invention relates to a light amount fluctuation correction device in an apparatus.

(Prior Art) As an example of a background level correction device for a conventional document reading device, there is one shown in FIG. 1, for example. This background level correction device is indicated by 100, and includes an amplifier circuit 1 that amplifies the peak value of an input original reading signal with a gain that adjusts it to a white level, and outputs the resultant signal, and an original reading signal output from the amplifier circuit 1 and a white level. Set value Vrf determined based on the level, comparator 2 to compare, and comparator 2
It has a control section 3 that outputs a control signal for controlling the amplifier circuit 1 based on the output of the amplifier circuit 1. The amplifier circuit 1 includes a field effect transistor (
(hereinafter referred to as FET) 4, document reading signal f, FET 4
The operational amplifier 5 has an input resistor R that divides the voltage according to the resistance value and inputs it, a ground resistor R, and a feedback resistor R3. In addition, in Figure 1, 6! /: is the original, 7 is a light source for illuminating the original (for example, a fluorescent lamp), 8 is a condenser lens, 9 is a CCD for photoelectric conversion, and 101'l is a program that amplifies the output of CCD 9 and outputs it as an original reading signal. 1) It is an amplifier.

In the above configuration, to explain the entire operation, the original 6f
f, when irradiated with light source 7, the reflected light from document 6 is reflected by lens 8.
CCD 9 (photodiode group not shown)
(a photoelectric conversion section comprising a photoelectric conversion section, an accumulation section that accumulates photoelectrically converted signal charges, and a shift register that outputs the product contents of the nucleus #j every time it receives a clock).

The signal photoelectrically converted by the CCD 9 is sent to a preamplifier 10.
The signal is amplified and input to the circuit 1 through 911 as a document reading signal. If the original reading signal input to the amplifier circuit 1 is smaller than the reference value vr of the comparator 2, the comparator 2
outputs a full value of "1", and the control unit 3 controls the resistance value of the FET 4 so as to set it at a constant value. Therefore, the input level to the operational amplifier 5, which is determined by the resistance value of the FET 4 and the resistance R weight, acts in the direction of increasing, and the level of the original reading signal, which is the output thereof, becomes 1/2. When the level of this read signal increases and becomes equal to Vr, which is the reference value of the white level, the comparator outputs "0".
4, and the input level to the operational amplifier 5 is reduced.

In this way, the pack ground level is fully corrected by outputting it as an image signal with a reference value vr that is equal to the peak gold/black level of the original reading signal and the white level having a constant amplitude.

However, according to the background level correction device in the conventional document reading device, the light source is Since the light meter fluctuations are corrected, when a half-tone original such as a photograph is read, the peak value becomes the white level, resulting in a whitish reproduced image.

(Objects and Structure of the Present Invention) The present invention has been made in view of the above, and in order to be able to faithfully reproduce the original even if the original is in halftone, when the original is black and white, the original Fluctuations in light intensity in an original reading device that fully corrects the pack ground level based on the reading signal, and when the original is in halftone, the gain is determined based on the light intensity of the illumination light source and the level of the original reading signal is corrected. A correction device is provided.

Hereinafter, a light amount fluctuation correction device in a document reading device according to the present invention will be described in detail.

(Embodiment) FIG. 2 shows an embodiment of the present invention, which includes a light source 7 that irradiates light onto a document 6, and a CCD Q that converts this reflected light into light 'Ht.
A lens 8 that forms an image on the top, a preamplifier 10 that amplifies the signal output from the CCD 9, and a photosensor 13 (F & A switch 14 (
switches 14a, 14b'f) are provided.

The photosensor '13 is provided near the light source 7, and its output is adjusted to a predetermined level by an adjustment circuit 15 and then input to the switch 14. This adjustment circuit 15 has an operational amplifier 16, and its positive terminal has a resistor vR for adjusting the offset of the black signal level, and a resistor R that slides into the resistor vR.
4 and a voltage-dividing earth resistor R are connected, and a variable resistor R@ for adjusting the gain is connected between its negative terminal and output terminal. The amplifier circuit 1 has the same circuit configuration as that shown in FIG. 1, and is connected to a control section 3 via a comparator 2. The control unit 3 outputs “1” of the comparator 2 via the resistor R.
7, a switch 18 that determines the operation time limit for gain adjustment, an operational amplifier 19 that outputs the full control signal to the gate of FET 4, a capacitor 20 connected between its old terminal and ground, and its negative Resistors ■7- and R@ connected between the terminal and ground and between the output terminals,
It has resistors R10 and R11 connected between a switch 18, one transistor 17, and ground. Switchers 4 and 18 are controlled by switch control signals 21 and 22.

In the above configuration, the operation will be explained using the time chart of the PI3 diagram.

(1st adjustment operation White original 6'f: Set it on the reading device. The light from the light source 7 illuminates the original 41.16, and this reflected light is CC-controlled by the lens 8.
Focus on D9. When amplified by the output sound preamplifier 10 of the CCD 9, the amplification factor is determined so that the peak value becomes the white level (equal to the reference value/vrl).
South (a) A). In this case, the light source 7, which is the fluorescent lamp, is brightest in its middle part, so the peak value appears there. Next, monitor the output of 7 Otose/Sate Gaku13. Mar1
All light sources 7 are turned off, and the resistor vR is adjusted to make the output of the operational amplifier 16 equal to the black level (B in FIG. 3(a)).

Also, all light sources 7 are turned on, and variable resistor R6 is turned on! II adjustment to make the output of the operational amplifier 16 equal to the white level (see Fig. 3).
C) of B). FIG. 3(b) shows the switch control signal 21, which turns on the switch 14m when it is "0" and turns on the switch 14m when it is tAriJ. When this switch control number 1d 21 is applied to the switch 14, the output of the switch 14 is the third
It will look like figure (c).

The IfC draft reading operation will be explained below.

A switch control signal 225c (shown in FIG. 3) is applied to the switch 18 of the control section 3 in the case of a 2-inch black and white original. When the switch control signal 22 is rlJ, the switch 18 is turned on to adjust the gain of the amplifier circuit l,
When it is "O", the switch 18 is turned off and the capacitor 2
The amplifier circuit 1'f is controlled with a gain determined according to the amount of charge of zero. A switch control signal 21 (see Fig. 3) is sent to the switcher 4.
(b)) When signal (b)) is given, the signal +I9 in FIG. A' is a reading signal of a black and white original. When this is input, the switch 18 is on, so if the level of the reading signal A' is smaller than the reference value Vr (equal to the white level), the comparator 2 will be set to "1". ”
outputs and turns on the transistor 17, and the capacitor j)
Connect to 201 negative power supply. As a result, a negative gate voltage is applied to the FF:, T4 via the operational amplifier 19 depending on the time constant of the circuit, and the resistance of the J FET 4 increases. F
As the resistance of the ET 13 increases, the input voltage division value of the operational amplifier 5 increases, so that a large output image signal can be obtained.

In this way, since the peak value of the read signal A' is corrected to the white level, variations in the amount of light from the light source 7 can be corrected.

(3) For halftone originals Switch 18 of control unit 3 as shown in FIG.

control signal 22 is provided. On the other hand, when the switch control signal 21 (FIG. 3 (b)) is applied to the switch 14, the third
The signal in figure (g) (synthetic signal of the output A'' of the amplifier 117 and the output C of the operational amplifier 16) is input to the amplifier circuit l. A'' is the reading signal of the halftone original, and this is the input signal. When doing so, the switch 18 is turned off. On the other hand, when the output C of the operational amplifier 16 corresponding to the output of the photo sensor 7 is input, since the switch 18 is on, the output C becomes smaller than the reference value Vr due to the light amount fluctuation. If so, the comparator 2 outputs "1" and the control section 8 controls the amplifier circuit 1 to amplify the output C so that it becomes equal to the white level.

This fixes the gain of the amplifier circuit 1, and when the reading signal A'' of the halftone original is input to the amplifier circuit 1, it is increased by 1@@ by the gain. Therefore, the halftone is not corrected to its own level. , an image signal faithful to halftones is output from the amplifier circuit l.

In this case, the operator may select whether or not it is a halftone original, or it may be controlled by a microcomputer, etc. by counting the levels of white No. 46 and black signals in the image signal. It may be possible to do so.

(Effects of the Invention) As described above, according to the light amount fluctuation correction device in the document reading device according to the present invention, when the document is black and white, the background level is corrected based on the document reading signal, and when the document is in halftone, the background level is corrected based on the document reading signal. Since the gain is determined based on the light intensity of the illumination light source and the level of the original reading signal is corrected, even if the original is in halftone, it can be faithfully reproduced to 1#.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a pack ground level correction device in a conventional document reading device. Figure 2 shows manuscript reading according to the present invention.
FIG. 4 is a circuit diagram of a pre-light and fluctuation correction device in the obscuring device. Figure 3a
)←)4-)IF-)?)(＼)对) is an explanatory diagram of waveforms of signals at various parts in the circuit diagram of FIG. 2. Explanation of symbols 1... Amplifier circuit, 2... Comparator 1/-ri, :3...
・Control unit, 4... Field effect transistor (FET)
, 5... operational amplifier, 6... original, 7... original illumination light source (fluorescent lamp), 8... condensing lens, 9... C
CD, 10... Preamplifier, 13... Photo sensor, 14... Switch, 15... Adjustment circuit, 16...
...Operation amplifier, 17...Transistor, 18...
Switch, 19... operational amplifier, 20... capacitor, 21.22... switch control signal, 100...
Pack ground level correction device. Patent applicant: Fuji Xerox Co., Ltd., l,! 11 people Ben JQj lawyer Shin Matsuhara 2nd patent attorney Kiyoshi Muraki Same amount Patent attorney Taira 1) Tadashi Shiima Patent attorney Atsushi Ueshima - Same La PIl! I! Hitoshi Suzuki

Claims (1)

[Claims] Detecting means for outputting all leading signals according to the light intensity of a light source for document illumination, and a peak value of the input signal as a white level KM! The light amount fluctuation correcting means includes a light amount fluctuation correcting means that performs the following operations when a monochrome original is read.
The level of the original reading signal 46 is adjusted based on the gain determined by using the original reading signal as the input signal, and when a halftone original is read, the original reading signal is adjusted based on the gain determined by using the light amount signal as the input signal. 1. A light intensity fluctuation correction device for a document reading device, characterized in that: