JPS63245175A - Image reader - Google Patents

Abstract

PURPOSE:To execute proper density adjustment simply by calculating the difference between a prescribed density level of data by one read line (density level of background part of original) and a corresponding reference density level and adjusting a binarized reference voltage to eliminate the difference and executing the operation in parallel with reading. CONSTITUTION:When an automatic exposure adjusting mode is set, image data is written in a line RAM 50 via a shading circuit 46 based on a shift pulse SH signal. Density data corresponding to the background of no data of images and corresponding to a black level is extracted from the data. A CPU 42 controls a binarized reference voltage signal DTH of the RAM 56 based on the data to adjust the reference voltage of a comparator circuit 48. The data for density adjustment is read in the unit of line and the binarized reference voltage is controlled based on the data and since the density adjustment is executed in parallel with image reading, neither preparatory scanning nor special sensors for density detection is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention is directed to image reading 5Ai! Regarding (image reader), in detail, it is possible to use image PI! without the need for preliminary scanning or special sensors for detecting document density. The present invention relates to an image reader capable of adjusting density.

The image reader of the present invention is used, for example, to read a text document with a non-white background.

[Prior Art] Conventionally, an image reading device uses a one-dimensional image carrier (COD)! (image reader) is provided.

The apparatus scans the reflected light from, for example, a document placed on a document table while photoelectrically converting it using COD, performs predetermined signal processing on the reflected light, and sequentially outputs the image data as image data.

When an image is read by the image reader, an image is created ii! In order to adjust the density of the image to the appropriate level, read the density of the original image by preliminary scanning,
Adjustments are made by adjusting signals or the like to bring the density closer to a reference level, or by detecting the density using a sensor that detects the density of the original image.

[Problems to be Solved by the Invention] As mentioned above, in order to adjust the density in conventional image readers, time-consuming operations such as preliminary scanning are required, or operations such as a density detection sensor are required. This requires special equipment and is a waste of time or cost.

The present invention provides an image reader that can eliminate such waste and easily perform appropriate density adjustment.

Means and operation for solving the L problem] The present invention performs photoelectric conversion using a one-dimensional image carrier while exposing and scanning an original image, and then performs A/D conversion and binarization using the area coverage modulation method. An image reading device that performs predetermined processing such as processing and outputs the image data, the device comprising: storage means for storing at least one line of image data; and a predetermined density level of the stored one line of data;
a calculation means for calculating a difference by comparing it with a corresponding reference concentration level; an adjustment means for adjusting a reference voltage for binarization in order to eliminate the calculated difference; the memory, the calculation, and the The image reading apparatus includes a control means that sequentially executes adjustment in parallel with image reading.

In the above, the predetermined density level is, for example, white area 11 of the original image! 11 from the reflected light from (plain background area)
means the data that is

Further, the reference density level means, for example, data obtained from reflected light from an ideal white original. For example, if the output signal from the COD is quantized with 7 pits and the black level is set to "0" and the white level to N27J, the data value becomes 127.

Therefore, comparing a predetermined density level with a reference density level to eliminate the difference means, for example, that the plain background area of @product is pale blue, and the density data of the area is rl 00J.
In the case of a numeric value of culm, it means to bring the level closer to N27J and make the background area of the image created closer to white. In the present invention, the above-mentioned approach is achieved by controlling the reference voltage for binarization.

Further, detection of the predetermined 11 degree level and adjustment of the reference voltage for binarization are sequentially executed in parallel with image reading. Therefore, neither a preliminary scan nor a special sensor device is required for density adjustment.

[Example] Hereinafter, the present invention will be described in detail in the following order with reference to the accompanying drawings.

(1) Schematic structure of image reader (2) Control means of image reader (3) Explanation of test pattern (4) Explanation of operation (1) Schematic structure of image reader FIG. 1 shows the mechanism of the image reader according to the embodiment. It is a schematic cross-sectional view.

A halogen lamp 2 serving as an exposure source irradiates an original 6 placed on an original glass 4 . yKKO2, original glass 4
The originals are placed parallel to each other along the original scale provided on the screen. On the bottom surface of the edge of the original glass 4, there is a test pattern for magnification and focus adjustment, or shading correction (see Figure 4).
will be installed.

The halogen lamp 2 is equipped with a reflector 118 and an infrared cut filter 10.

The reflected light from the source H56 is reflected by the first mirror 12, the second mirror 14, and the third mirror 16 in order.
The light passes through the lens 18 and enters the one-dimensional C0D (!1iff!! element) 20.

The COD 20 is held by the COD holding section 22, and its position and angle are adjusted. Further, the CCD holding section 22 and the lens 18 are attached to a moving table 24.

To adjust the magnification, use the lens motor 2 as shown in Figure 2.
6, the moving stage 24 is moved along the guide rail 30 in the optical axis direction via the wire 28.

Further, the focus is adjusted by moving the COD holding section 22 in the optical axis direction using a focus motor 32 attached to the moving table 24.

When scanning the original 6, the light source 2 and mirrors 12 to 16 are moved in the scanning direction, as is well known.

(2) Image reader control means FIG. 3 is a block diagram of a circuit for detecting the density of the original.

The clock generation circuit 40 includes an image sensor (one-dimensional C0D) 2
It provides a necessary SH (shift pulse) signal to 0, and is also connected to the CPU 42 and used as a clock signal. The image sensor 20 converts the reflected light signal from the original into an electrical signal. The A/D converter 44 converts the analog signal from the image sensor 20 into a digital signal.

The shading circuit 46 operates in the main scanning direction (line direction).
This is a circuit for correcting unevenness in the amount of light and variations between bits (pixels) of the Wi image element 20, and its timing is given by the shading signal from the CPU 42. The output signal from the shading circuit 46 is input to a comparison circuit 48 for binarization and a line RAM 50.

The comparison circuit 48 compares the shading-corrected image signal with the reference signal (reference signal for binarization) selected by the selector 52, and outputs the result to the output circuit 54 in one bit. The output circuit 54 outputs a 1-bit image signal and a valid image signal to the outside.

The line RAM 50 stores the shading-corrected image signal for one line. This hit-or-miss signal is CPtJ
42, and the CPU 42 reads this line RAM5.
From 0, image information for one line is obtained.

The RAM 56 stores attribute information and uniform threshold information for binarization (binarization without dithering). 21
The i11 or dither attribute is determined by the CPU 4 based on the image information for one line that was hit or missed by the line R△M50.
2. Further, the uniform threshold value is also determined based on the image information for one line.

The pattern generation circuit 58 generates equivalence (ununiform equivalence) information in the dither method, and r174m is (
mx n ) matrix.

The selector 52 selects threshold information for binarization to be sent to the comparison circuit 48 based on the attribute information from the RAM 56. That is, if the attribute is dither, the dither pattern data from the pattern generation circuit 58 is used as threshold information,
Furthermore, if the attribute is binary, uniform level data from the RAM 56 is sent to the comparison circuit 48 as threshold information.

In addition, the selector 52 is connected to the CP (J42 to 7-pit 2
11 [Converting reference voltage signal D@ is transmitted, and based on this, the reference voltage when binarizing is performed at the same value at a uniform level is controlled. This control is based on one line of image information stored in the line RAM 50 (feedback control, and corresponds to, for example, the background part of the document (plain color, but not necessarily white). This is done so that the image data has a white level.

Furthermore, CPLJ42 has a motor signal, a lamp signal,
Input position signal and command signal. Also, to adjust the magnification and focus, drive the lens motor 26 and focus motor 32 via the drivers 60 and 62, respectively.
I will do it.

(3) Description of test pattern The test pattern 7 for magnification and focus adjustment, shading correction, etc. consists of a white shading part 7a in the upper half and a pattern part 7 in the lower half, as shown in FIG.
It consists of b.

The shading correction is performed by photoelectrically converting the reflected light from the uniform white test pattern 7 using the wl image element 20.
This is done by reading the signal into the A/D converter 44 and the shading circuit 46 and correcting the deviation between the read signal and the ideal signal.

Note that the above-mentioned deviation is caused by unevenness in the optical system such as the lamp 2 or by C0D.
This is thought to be due to the shadow W of the variation in characteristics of the 20 pixels. In addition, the correction data is stored in the shading circuit 4.
6.

The pattern portion 7b of the test pattern 7 includes a black pattern 7c17c provided on both sides and a striped pattern 7d provided in the center.
It consists of. The magnification is calculated by measuring the distance between the black pattern parts 7G and 70 using C0D20 and comparing it with a preset length. In addition, the focus adjustment is performed using measured data (i
The CCD 20 is moved by the focusing motor 32 so that *solid line in Figure 5 approaches the state shown by the broken line.

In the manner described above, density adjustment is performed by the apparatus of this embodiment.

As can be seen from the above, in the apparatus of this embodiment, the reference voltage for binarization is adjusted at the same time as image reading to obtain image data with optimal density. Therefore, neither preliminary scanning nor special sensors are required for density adjustment.

(4) Operation explanation The operation of the apparatus of this embodiment will be explained below.

FIG. 6 is a flowchart showing 1 and 1ltll by the control CPU 42 of the image reader, and FIG. 7 is a time chart. Note that in this flowchart, illustrations of processes that are not directly related to the essential parts of the present invention, such as A8 ratio adjustment, focus adjustment, and image data output, are omitted.

The CPU 42 starts processing by turning on the power, for example, and first sets an initial state (8102).

When a scan command is input (S104), if the slider is not at the reference position (8200), a drive signal is generated to a slider drive motor (not shown) (8201>
After returning the sliders (the first slider carrying the halogen lamp 2, etc., and the second slider carrying the mirror 14, etc.) to the reference position, an off signal for the motor is generated (S20
2). The return is confirmed, for example, by a predetermined home position signal from the scanning system. After that, an on signal is generated to the exposure lamp 2 and the slider drive motor (8108, 51
10) Start exposure scanning of the original.

The light emission intensity of the exposure lamp 2 is set to an optimal level based on the reflected light from the white pattern portion 7a of the test pattern 7 (8112). For example, when the analog image signal from the CCD 20 is converted to 7 bits (128 levels from black level O to white level 127), the maximum value of the digital image signal obtained from the reflected light of the white pattern section 7a is The light emission intensity of the lamp 2 is adjusted so that the value becomes 127.

Based on the reflected light from the white pattern portion 7a of the test pattern 7, shading correction data is loaded into the RAM of the shading circuit 46 (S114). The correction data is data for multiplying the output data from each pixel of the C0D20 by a predetermined coefficient for each pixel. For example, the data obtained from the white pattern section 7a is uniformed by the shading correction. be converted into

When the scanning reaches the leading edge of the image (8116), a valid image signal is generated and image data output from the output circuit 54 is started.

If automatic exposure adjustment mode is set (8118
:Yes), st- is synchronized with the line RAM 11 write signal @C which rises every three clocks of the signal A (see FIG. 7), and the image data B is written to the line RAM 50 via the shading circuit 46 ( 8120).

From the line RAM data D written above, 15 degree data corresponding to the white level (meaning the plain background part, not necessarily white) and black level (character part) of the image, specified by the operator. Alternatively, the automatically specified density data of the original 1i area (for example, A4 size) or the density data of the trimmed area is extracted (8122).

Based on the extracted density data, the binarized reference voltage signal Dr1. ．． (3124>Adjust the reference voltage of the comparison circuit 48. The adjustment is, for example, so that the background portion corresponding data after shading correction has a maximum value of 127 (see 81121).

As can be seen from the time chart in FIG. 7, the adjustment start time using the binarized reference voltage signal DT) is 3 clocks of SH and other signals, that is, scanning 3 lines late.

If the automatic exposure adjustment mode is not set in step 8118, the binary reference voltage signal SDTH is set to a predetermined value (S132). The predetermined value is, for example, a value corresponding to the light emission intensity that makes the image data corresponding to the white pattern portion 7a of the test pattern 7 have the maximum value 127.

When the exposure scan reaches the trailing edge of the document (8126), the effective image signal is turned off to stop data output from the output circuit 54, and an off signal for the exposure lamp 2 is generated (512).
8>, also generates a return signal for the slider drive motor (8130), and after returning the slider to the reference position (S133), generates an off signal for the motor (8130).
134).

In the above, when specifying editing image creation such as trimming, for example, the above control can be executed for only the trimming ffi area of the document area, as shown in FIG.

[Effects] As described above in detail, the present invention reads data for density adjustment in units of one line in an image reading device using one-dimensional 1llf1 elements, and performs binarization based on the data. This is to control the reference voltage of.

As is clear from the examples described, 'According to the present invention, density adjustment can be performed in parallel with image reading, so there is no need for preliminary scanning or special sensors for density detection. be.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an image reader according to an embodiment. FIG. 2 is a plan view of a mechanism for moving the lens and COD. FIG. 3 is a block diagram of the control circuit of the image reader. FIG. 4 is a plan view of the test pattern. The fifth factor is a diagram of the density distribution near the inner edge of the test pattern black pattern. Figure 6 shows the CP of Figure 3.
3 is a flowchart showing control of U. FIG. 7 is a time chart showing the control of the CPU in FIG. 3. FIG. 8 is a diagram showing the series control area in the trimming mode.

Claims (2)

[Claims] (1) An image reading device that performs photoelectric conversion using a one-dimensional image sensor while exposing and scanning a document image, then A/D conversion, performs predetermined processing such as binarization processing using the area modulation method, and outputs the result. a storage means for storing at least one line of image data, and a predetermined density level of the stored one line of data,
a calculation means for calculating a difference by comparing it with a corresponding reference concentration level; an adjustment means for adjusting a reference voltage for binarization in order to eliminate the calculated difference; the memory, the calculation, and the An image reading device comprising: a control unit that sequentially performs adjustment in parallel with image reading. (2) The image reading device according to claim 1, wherein the predetermined density level is a density level of a background portion of the document.