JPS61247164A - Automatic density adjusting original reader - Google Patents

Abstract

PURPOSE:To improve the picture quality by discriminating a binary-coded threshold value at each region from the density detected by the 1st original scanning and using the said threshold value at the 2nd original scanning so as to apply binary coding. CONSTITUTION:A signal detected by an image pickup element 20 at the 1st original scanning is written in a line RAM 50 via an AD converter 44 and a shading circuit 46. A CPU 42 discriminates the attribute of the original based on a data in the RAM 50. Whether binary-coding or dither is selected depending on a character picture or an intermediate tone picture and its threshold value is written in an attribute RAM 56 at each region of the picture. A signal obtained at the 2nd original scanning is compared with an output of the attribute RAM 56 or a pattern generating circuit 58 at a comparator circuit 48, the result is binary-coded and outputted to an output circuit 54. Thus, even when the density of the background of the original changes, a proper binary coding picture is obtained and the quality of picture is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a document reading device that reads the density of a document.

(Prior Art) A document reading device reads the density of a document using an image sensor, compares it with a predetermined threshold value, and outputs it as a binary image. For setting this threshold value, an optimal method must be selected from among the binary method, dither method, etc., depending on the nature of the image.

By the way, since the density of the background of a document differs from document to document, it is preferable to perform correction for each document in order to obtain a proper binary image. For this correction, various methods have been tried in the past, particularly in connection with copying machines, such as controlling the amount of light from an exposure lamp.

(Problems to be Solved by the Invention) By the way, when the background of a document itself changes within the same document, it is difficult to obtain a proper binary image.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic density adjustment document reading device that adjusts density reading so that an appropriate binary image can be obtained even when the background density of the document changes.

(Means for Solving the Problems) The automatic density adjustment document reading device according to the present invention includes a density detection device that detects the density of the document using an image sensor, and a density detection device that detects the density of the document in the first scan of the document. The density is memorized, and based on the detected density, a threshold value for binarization is determined for each area set by subdividing the document in advance, and in the second document scan, the threshold value is set based on the result of this determination. a threshold discrimination setting means; a binarization means for binarizing the density of each area detected by the density detection means using the threshold set by the threshold setting means; and a density detection means in the first document scanning. Detects the density of the document, then in the first scan, causes the threshold value discrimination setting means to discriminate the threshold value for each area, and then, in the second document scan, causes the density detection means to detect the density of the document, and sets the threshold value discrimination. The present invention is characterized in that a density reading control means is provided which prevents the binarization means from binarizing the detected density using a threshold value set by the means.

(Function) The document is subdivided into predetermined regions, and the threshold value is optimally determined for each region from the density detected by the first scan of the document.
In the second document scan, this threshold value is used to perform binarization.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

(a) Image reader FIG. 2 is a sectional view of the mechanism of the image reader according to the present invention. A halogen lamp 2 serving as an exposure source irradiates an original 6 placed on an original glass 4 . The original 6 is placed in parallel along the original scale provided on the original glass 4. The halogen lamp 2 is equipped with a reflecting mirror 8 and an infrared cut filter IO.

The reflected light from the original 6 is transmitted to the first mirror 12 and the second mirror 1.
4 and the third mirror 16, the light passes through the lens I8 and enters the one-dimensional C0D (imaging device) 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.

The magnification is adjusted by moving the moving table 24 in the optical axis direction using a moving mechanism (not shown).

The focus is adjusted by moving the holding portion 22 in the optical axis direction using a focus adjustment motor (not shown) 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.

(b) Internal structure of image reader FIG. 3 is a block diagram of a circuit for detecting the density of a document.

The clock generation circuit 40 generates S necessary for the image sensor 20.
H (zumble hold) signal is given, and on the other hand the CPU
42 and is used for a clock signal. The imaging probe 20 converts optical signals into electrical signals. The A/D converter 44 converts the analog output of the image sensor 20 into a digital signal. The shading circuit 46 is used to correct unevenness in the amount of light in the main scanning direction and variations between bits of the image sensor, and is given its timing by the CPU 42 . The output of the shading circuit 46 is input to a comparison circuit 48 and a line RAM 50. The comparison circuit 48 compares the image signal corrected through the shading circuit 46 with the signal selected by the selector 52, and outputs the result in one bit. The output circuit 54 outputs a 1-bit image signal and a valid image signal (synchronization signal) to the outside.

The line RAM 50 stores the shading-corrected signal for one scan in memory. This write signal is
42, and the CPU 4.2 uses this line RAM
By referring to 50, image information for -lines is obtained. The attribute information stored in the attribute RAM 56 has a binary or dither attribute determined by the CPU 42 based on the information written in the line RAM 5G, and this attribute is not used during data transfer (scanning). The selector 52 is changed to the original and output to the comparison circuit 48.

The pattern generation circuit 58 generates a threshold value at the time of dither selection, and the threshold value is generated in a matrix of (mXn).

The selector 52 selects threshold data to be sent to the comparison circuit 48 from the threshold information and attribute information from the pattern generation circuit 58 and the RAM 56. If the attribute is dither, data from the pattern generation circuit 58 is sent to the comparison circuit 48, and if the attribute is binary, threshold information from the attribute RAM 56 is sent to the comparison circuit 48. C.P.
U42 controls the entire system from the above signals, motor signals, lamp signals, fixed position signals, etc., and command signals.

(c) Flow of reading image information The flow of reading image information will be explained with reference to the flowchart shown in FIG.

One feature of this embodiment is that xlof
Determine the data processing attribute (binary or dither) from the density data obtained from the preliminary scan for each nm), and determine the threshold value corresponding to this determined attribute when reading the density in the main scan. It is to be.

In this embodiment, the document position is also detected from the density data obtained by preliminary scanning.

First, a command signal is input (step P1). It is determined whether this command signal is a start command (step P2). If the start command has been input, the process moves to the following scanning operation. The magnification of the scanning system and the like are set according to each usage mode.

First, turn on the lamp for exposure (step PIO
). Next, it is determined whether the scanning system (slider) has returned to its home position (step pH).

If it has returned, the process advances to step P20. If not, the motor is driven in the return direction to return to the home position (step P12), and it is determined whether the scanning system has returned to the home position (step P13). If not, the process returns to step P12. If it has not returned, the motor is turned off (step P14).

Next, shading processing is performed. Since the slider is at the reference level, the shading signal is turned on (step P20), and it is determined whether an sH (sample and hold) signal, which is a synchronizing signal of the output of the C0D 20, is input (step P21).

After waiting for the SH double signal to be input manually, the shading signal is turned off (step P22).

Next, a preliminary scan is performed for threshold attribute determination and original document detection. First, it is determined whether or not the SH multiplier signal is manually operated. When the SH multiplied signal is input, the current output of the C0D 20 subjected to shading correction is written into the line RAM 50 (step P31).

It is determined whether or not the next SH multiplied signal is input (step P32), and at the time of input, the write signal of the line RAM 50 is turned off (step P33).

Next, the position of the document is detected from the data written in the line RAM 50 (step P34). The position of the document is determined by detecting the range in which the image exists within the document. Next, based on the data written to the line RAM 50, the attribute of the data processing, ie, whether it is binary or dithered, is determined and written to the selector 52 (step P35). This attribute determination will be explained in detail later. Next, it is determined whether the scan is completed (step P36). If not, the process returns to step P30.

Next, the motor is driven in the return direction to return the scanning system to the normal position (step P37), and it is determined whether the scanning system has returned to the normal position (step P38). If not, the process returns to step P37.

Next, perform the main scan. The motor is driven in the scanning direction, and scanning for data output is started (step P40). Next, the scanner waits until the scanning reaches the leading edge position of the document measured during the preliminary scan (step P41). In addition,
The size of the margin is determined from the detected document size and paper size, and the paper feed timing or synchronization signal timing of the printer is changed. When the leading edge of the document is reached, the valid image signal is turned on (step P42), the output signal is made valid, and the output device (printer) is activated.

Step P43) Determine whether the document has reached the rear edge position.
When the document reaches the trailing edge position, that is, when scanning is completed, the effective image signal is turned off and the output signal is made invalid.

Next, clarify the lamp for exposure (step P50
). Step P51 to drive the motor in the return direction.
), it is determined whether the scanning system has returned to its home position (step P52). If it has returned, the motor is turned off (step P53). Then, the process returns to step pt to prepare for the next start command.

(d) Attribute Judgment Based on the density of the read original, the original density is processed using a binary method suitable for characters and a dither method suitable for halftone images. The attribute judgment (step P35) as to which of the two to select is made in the line RAM in a preliminary scan.
is determined from the data stored in , according to the flowchart shown in FIG.

In this case, the text/graphics information area has a predetermined size, for example,
It is divided into 10×10×10 blocks, and attributes are determined for each block.

First, in the document detection (step P34), it is determined whether or not there is content of the document (step P20). If not, simply return. If there is content of the manuscript, import the information of the next block (step P121
), determine the attributes as follows:

First, find the concentration distribution within the block (step P13
0). When the difference in concentration levels is smaller than a predetermined value,
Next, it is determined whether the density center is near either the white level or the black level (step P132). If so, the attribute is set to binary, and the threshold is set to an intermediate level between black and white (step P133). Next, the selected attribute and threshold are written and the detection block is updated (step PI34). Next, it is determined whether the block is larger than the document edge 2 (step P135), and if not, the process returns to step P130 to continue attribute determination. If it is large, return it.

If it is determined in step P131 that the density level difference is large, then it is determined whether there are two density peaks (step P140). If so, the attribute is set to binary, and the threshold is set to the middle of the two peaks (step P14).
1). Then, the process advances to step PI34.

In the density distribution, if the density level difference is small and the density center is not near either the white level or the black level, the attribute is set to dither (step P150). Also,
Even when the density level difference is large and there are no two density peaks, the attribute is set to dither (step P150). Then, the process advances to step P134.

Next, the attributes determined by the above discrimination are selected by the selector 52.
The density is written to the output circuit 54 using this selection. Then, the information of the block of the next scanning line is taken in (step P13.4).

Next, it is determined whether the position of the block is larger than the document edge 2 (step P I 35). If it is large, return it as is. If not, the process returns to step P130 and the attribute of this block is determined.

(Effect of the invention) The image quality is improved because the document is subdivided into multiple regions and an appropriate threshold value is set for each region.

[Brief explanation of drawings]

FIG. 1 is a flowchart for attribute determination. FIG. 2 is a sectional view of the image reader. FIG. 3 is a block diagram of the internal configuration of the image reader. FIG. 4 is a flowchart of document reading. 2...Light source, 6...Original, 2o...cc
D0 Patent Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Aobai Ao and 2 others 1st Period 21! 1 Procedural Amendment (Self-Restricted June 6, 1985)

Claims (1)

[Claims] (1) A density detection means for detecting the density of the original using an image sensor; and a density detection means that stores the density detected by the density detection means in the first scanning of the original, and sets the original by subdividing the original in advance based on the detected density. a threshold value determination setting means for determining a threshold value for binarization for each region, and setting a threshold value based on the result of this determination in a second document scan; Binarization means performs binarization using the threshold value set by the threshold value setting means; In the first scanning of the document, the density detection means detects the density of the document; Then, in a second document scan, the density detection means detects the density of the document, and the detected density is converted into a binarization means using the threshold set by the threshold discrimination setting means. An automatic density adjustment document reading device characterized by being provided with density reading control means for binarizing.