JPH0216861A - Picture reading device - Google Patents

Abstract

PURPOSE:To read a picture by high precision at all times without being influenced by the variation of ambient temperature by reading plural reflection surfaces with different reflection factors, and obtaining correction data, and adjusting illumination light quantity and the reference voltage of a reference amplifier. CONSTITUTION:Reference reflection plates with different reflection factors extending from 0% to 100% are installed at one end of an original placing part in a main scanning direction successively. At the time of exposure adjustment, the minimum value and the maximum value of the reflection factor are obtained by operating a scanner input/output characteristic from the scanner output of the reference reflecting plate through a CPU 210. Then, they are compared with a target value previously set for the reference factor, and when the minimum value deviates from the target value, the reference voltage is adjusted by a reference voltage control circuit 206, and when the maximum value deviates from the target value, lamp voltage is adjusted by a lamp voltage control circuit 205. Thus, the read of high precision can be attained at all times without being influenced by the variation of the ambient temperature.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image reading device, particularly an image reading device that reads an original image with an optical sensor, converts it into a density signal, and then digitizes and reads the image with an analog/digital converter or the like. The present invention relates to an image reading device.

[Prior Art] Conventionally, this type of image reading device is equipped with a lighting device whose luminous intensity is variable, and the luminous intensity of the lighting device is adjusted (hereinafter referred to as dimming) before illuminating the image on the document, and the reflected light is then adjusted. Some devices are designed to be read using an image sensor such as a CCD.

In such an image reading device, when performing light control, a member having a reflective reference surface with uniform reflection density, such as a white plate (hereinafter referred to as a standard white plate), is illuminated, and this reflected light is read by an image sensor. , to determine the level of dimming. Furthermore, the image signal obtained from the reflected light from the standard white plate is stored in memory, and this is regarded as a reference signal corresponding to absolute white.

[Problems to be Solved by the Invention] However, the conventional device described above has the following problems because only the amount of light of the illumination device is adjusted. In other words, if the light amount of the illumination system is affected by changes in the dark current of the image sensor due to changes in ambient temperature, even if the light amount is adjusted, if the ambient temperature rises, the image will become whitish due to the dark current of the image sensor. It's put away.

The purpose of the present invention is to solve the problems of the above-mentioned conventional device,
An object of the present invention is to provide an image reading device that can always perform highly accurate reading without being affected by changes in the amount of light in an illumination system or the mouth sound current of an image sensor due to changes in ambient temperature.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an adjusting means for adjusting the luminous intensity of an illumination system that illuminates an original, and converting light reflected from the original illuminated by the illumination system into an electrical signal. An image reading means that converts and reads the image, a comparison and amplification means that compares and amplifies the electric signal at a predetermined set voltage, reads a plurality of reference reflective surfaces with different reflectances, and corrects it according to the image reading data obtained from the reflection density. The present invention is characterized by comprising a correction data calculation means for calculating data, and an adjustment means for adjusting the dimming means and the comparison and amplification means based on the correction data.

[Operation] According to the invention, the reflected light from a plurality of reference reflecting surfaces having different reflectances illuminated by the illumination system is read by the image reading means and converted into an electric signal, and this electric signal is converted to a predetermined signal by the comparison and amplification means. are compared and amplified at the set voltage.

Then, correction data is calculated and determined by the correction data calculating means according to the image reading data obtained from the reflection densities corresponding to the plurality of reference reflection surfaces.

Based on the correction data obtained in this manner, the adjustment means adjusts the dimming means and comparison amplification means of the illumination system.

Therefore, a predetermined reading density is always obtained and highly accurate reading is possible.

[Embodiments] Hereinafter, embodiments of the wooden invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, A is a reference reflective surface having a plurality of reflective surfaces with different reflectances, B is a dimming means for adjusting the luminous intensity of the illumination system that illuminates the document, and C is reflected light from the document illuminated by the illumination system. image reading means that converts the image into an electrical signal and reads the image;
D is a comparison and amplification means that compares and amplifies the electrical signals of the image reading means C at a predetermined set voltage, and E is a comparison and amplification means that reads a plurality of reference reflection surfaces A having different reflectances, and according to image reading data obtained from a plurality of reflection densities. Correction data calculating means for calculating correction data, F is an adjusting means for adjusting the dimming means B and the comparison and amplification means based on the correction data obtained by the correction data calculating means E.

Next, FIG. 2 shows the internal configuration and planar configuration of an embodiment of a document image reading device to which the invention is applied. Reference numeral 1 denotes a document image reading device main body, in which a document placed on a document placement section 18 on a platen glass 17 is irradiated by a document illumination unit 15, and a plurality of light beams arranged in the main scanning direction are illuminated by a lens 14 via a reflection mirror 16. It is configured to form a document image on a CGDI 2 made up of a light receiving element.

The original illumination unit 15 and the reflection mirror 16 are movable in the sub-scanning direction perpendicular to the main-scanning direction by a drive system (not shown).

Further, reference numeral 10 denotes a reference reflector plate provided on the right side of the document placement section 18 in the drawing to have a reflective surface having a reflectance that sequentially varies from 0% to 100% with respect to the main scanning direction.

In the figure, 19 is a platen cover, 11 is a control unit, and 13 is a CCD driver, and the circuit configuration of both is shown in FIG.

First, the operation of the document image reading device will be explained using FIGS. 2 and 3. The document reading device (hereinafter referred to as scanner) in this example is always connected to an external device (digital printer, personal computer, etc.).
Communication of control signals with these external devices and image output to the external devices are performed via the interface circuit 211. The original is placed on the platen glass 18 so that the right end in FIG. 2 is the leading edge of the original.

Further, the original illumination unit 15 of the optical system has its initial position at the right end in FIG. 2, and its position is confirmed by an optical position sensor (not shown). Further, with the document placed on the platen glass 17, instructions for various modes are manually given by an external device. For example, set the pixel density to 4
00dpi, 300dpi.

200 dpi, whether the image signal should be a binary code or a multi-value signal, etc. CPU that received this
210 outputs a control signal in advance to set the pixel density and image signal. Next, when a manual reading start command is input from an external device, the CI'LI 210 first outputs a signal to the lamp voltage control circuit 205 and
Turn on 1. At this point, scanning for reading the document does not begin immediately, but the process continues for approximately 300 seconds until the amount of light from the lamp 201 stabilizes.
Wait for ~500m5ec. During this time, whether the image signal is input manually to the interface circuit 211 or CP +1210
The control signal is not output to external devices.

Thereafter, the document illumination unit 15 starts scanning in the direction of arrow A in FIG. The distance from the initial position of the original illumination unit 15 to the leading edge position of the original on the platen glass 17 is approximately 2 to 3 m.
m, during which the scanning speed of the optical system by the motor is controlled to be stable.

When the document illumination unit 15 reaches the document leading edge position, the CPU 210 outputs a control signal to enable image signal output to the interface circuit 211, and the read image signals are sent one after another to an external device. The scanning length of the optical system is
210 is uniquely determined by the number of pulses that drive the motor, the CPII 210 determines that document reading is complete when the required number of pulses are output to the motor, and turns off the lamp, disables image signal output, and reverses the motor. It performs control and outputs a document reading completion signal to an external device. Under the motor reversal control of the CPU 210, the original illumination unit 15 moves in the direction of arrow B in FIG. 1, and stops when the optical position sensor detects that it has reached the initial position. If there is no command from the external device to start reading the next document during this optical system return period, the optical system stops at the initial position and ends the operation.

Furthermore, the circuit operation of this example will be explained using the block diagram of FIG. The image analog signal output from the CCD 12 on the CCD driver 13 is compared and amplified with the voltage value of the comparison voltage control circuit 206 by the eight MP 203.

The amplified analog signal is converted to/D converter 204
is input. The to/D converter 204 converts the image signal from an analog signal to a 4-bit digital signal. This digital image signal can be output to an external device in either of the two modes mentioned above, ie, binary mode or multilevel mode. Which of these two modes to output is determined by a command from an external device, and the CPII2
10 outputs a control signal to the selector 209.

In the binary mode, a 4-bit image signal is converted into 1-bit by the binary conversion circuit 208 according to the slice level output from the CP+1210, and the signal is manually input to the selector 209.

Next, a density adjustment method performed in the tree embodiment will be described. Figure 4 shows the scanner's human output characteristics (GSTC: Gra
y 5cale Tramsfer Curve), and the straight line part is expressed as y=ax+
b (y: scanner output, X: reflectance), and the slope al
The scanner output value when the reflectance (the method of least squares).

FIG. 5 is a flowchart showing an example of the processing procedure of the image reading device according to the tree embodiment.
1, the reference reflector 10 is read by a scanner to obtain a multivalued digital value (in this example, an image analog signal is converted into a 4-bit digital signal).

Next, in step 542, the equation G-5-T-C is used to calculate the curve and H shown in FIG.

L is the point with the lowest reflectance (y = 15 + 4 wood examples)
, H is the point with the highest reflectance (y=o).

Then, whether L and H obtained in step S43 are within predetermined target values L' and H' (here, L': the target value of L, and H': the target value of H). Compare. Here, if the comparison result is outside the target value, step S
At 44, when L is outside the target value, the comparison voltage control circuit 206 adjusts the comparison voltage H when it is outside the target value.→The lamp voltage control circuit 205 adjusts the lamp voltage and ends when the voltage reaches the target value.

In the above-described embodiment, the reference reflector was provided inside the apparatus, but the reference reflector may be provided at a normal image reading position and read in to perform density correction. In this way, it is possible to eliminate the adverse effects of aging of the reference reflector.

Furthermore, even if the reference reflector is configured with two reflecting surfaces, one with a reflectance of 0% and the other with a reflectance of 100*, the same effect as in the wood embodiment can be obtained.

[Effect of the invention] As is clear from the above explanation, according to the invention, a plurality of reflective surfaces having different reflectances are read, correction data is obtained,
Since the amount of illumination light and the comparison voltage of the comparison and amplification means are adjusted based on this, it is possible to always read images with high precision without being affected by fluctuations in ambient temperature.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the invention; Fig. 2 is a side view and plan view showing an image reading device to which the invention is applied; Fig. 3 shows the circuit configuration of a CCD driver/control unit. FIG. 4 is a human output characteristic diagram of the scanner, and FIG. 5 is a flowchart showing an example of a control procedure for density adjustment. DESCRIPTION OF SYMBOLS 1... Original image reading device, 10... Reference reflection plate, 11... Control unit, 12... CCD line sensor 13... CCD driver, 14... Lens, 15... Original illumination Unit, 16... Reflection mirror 17... Platen glass, 18... Document placement section, 19... Platen cover 201... Lamp, 203... Video map, 204... A/D converter , ...Lamp voltage control circuit, ...Comparison voltage control circuit, ...Arithmetic circuit, ...Binarization circuit, ...Selector...cpo. ...Interface circuit. Sumo Vsu's

Claims (1)

[Claims] (1) An adjusting means for adjusting the luminous intensity of an illumination system that illuminates the original; an image reading means for converting reflected light from the original illuminated by the illumination system into an electrical signal and reading an image; Comparison and amplification means for comparing and amplifying with a set voltage; correction data calculation means for reading a plurality of reference reflection surfaces having different reflectances and calculating correction data according to image read data obtained from the reflection density; An image reading apparatus comprising: an adjustment means for adjusting the light adjustment means and the comparison and amplification means based on the light control means.