JPS62166649A - Original reader - Google Patents

Abstract

PURPOSE:To accurately discriminate the position of a movable body at the time of scanning and restoration, by providing a an original position recognizing means, original scanning time measuring means, and means for calculating the moving distance for scanning of the movable body from a measured scanning time and performing reading processes of binary coding, etc., corresponding to an original area. CONSTITUTION:In order to read the picture information of an original 102 placed on an original platen 101 and pressed down by an original cover 110, an image pickup element 103 of CCD, etc., is used and lighting rays of light from a light source 104 are reflected by the surface of the original 102 and caused to form an image on the image pickup element 103 by means of a lens 108 through mirrors 105-107. An optical unit is moved toward the right from the left at a fixed speed while PLL control is applied by a DC servo motor 109. The moving speed of the optical unit is variable in a range from 90mm/sec to 360mm/sec in the returning trip. Coordinates (X1, Y1), (X2, Y2), (X3, Y3), and (X4, Y4) of four points when the main scanning direction and auxiliary scanning direction from reference coordinates SP on the original platen 101 are respectively set to X and Y are detected by pre-scanning the optical system.

Description

[Detailed description of the invention] (Field) The present invention relates to a document reading device.

(Prior Art) Conventionally, as an optimal binarization processing method for image signals, a method has been proposed in which a document is pre-scanned to determine the density of the image, and then the data during main scanning for image processing is binarized. There is.

There are two methods of reading the original density using preliminary scanning performed by reciprocating the optical system or the original table: (1) reading the original density during forward movement, and (2) reading the original density during backward movement. be. In addition, in order to avoid errors in determining image density due to reading parts other than the original, such as the original pressure plate, the position and size of the original are recognized and the image density of only the original part is determined before determining the original density. It is proposed to determine.

However, when method (1) is used, it is difficult to scan the original for recognition.

Scanning for reading image density (hereinafter referred to as AS scanning) and scanning for image formation (hereinafter referred to as main scanning) must be performed three times, and it takes time to start copying, causing inconvenience to the user. It's going to happen.

On the other hand, when method (2) is used, the document recognition scan is performed during the forward movement of the preliminary scan, the AS scan is performed during the backward movement, and the next second scan becomes the main scan, so there is no waste in the sequence. . However, conventionally, the sensor at the reversal position of the optical system has been omitted in order to reduce costs, and there are many cases where there is no sensor at the reversal position. In this case, there is a drawback that the exact position of the optical system cannot be determined due to fluctuations in the rise time of the speed of the optical system when the optical system changes from forward movement to backward movement. Furthermore, when the optical system moves back, the speed of the optical system is not controlled, and the speed is left to the motor torque and the load on the optical system, because it does not contribute to image formation and to reduce costs. is being carried out. This case also has the disadvantage that the position of the optical system during the backward movement is not accurate.

(Objective) The present invention has been made to eliminate the above-mentioned drawbacks, and for the purpose of highly accurate document density or document content determination, the present invention includes a document position recognition means, a document scanning time measuring means, and a scanning method based on the measured scanning time. It is characterized by having means for calculating the moving distance and performing reading processing such as binarization corresponding to the document area, thereby making it possible to accurately determine the scanning position and the position of the movable body during backward movement. Therefore, it is not necessary to provide all position sensors for each reversal position, and speed control during reverse movement can be performed with a limited amount.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of a document reading device to which the present invention can be applied. In order to read the image information of the original 102 which is pressed by the original bar 110 and placed on the original platen 101, a CCD is used.
The illumination light from the light source 104 is reflected on the surface of the original 102, and the mirror 105.10
6, 107 and the image sensor 103 by the lens 108.
imaged on top. Light source 104. Mirror 105 and Mirror 1
06 and 107 are designed to move at a relative speed of 2:l. This optical unit moves from left to right at a constant speed while being subjected to PLL control by a DC servo motor 109. This movement speed is 90 m depending on the magnification on the outward journey.
m/sec to 360 m/sec
It is variable up to c, and on the return trip, the center value is 360 m.
It is designed to be m/sec. The main scanning line perpendicular to the sub-scanning direction in which this optical unit moves is captured by an image sensor at l 6 p e I / m
The optical unit is moved forward from the left end to the right end while reading at a resolution of m, and then moved back to the left end to complete one scan.

FIG. 2 shows a schematic block diagram of a circuit that processes image signals from the image sensor 10.3. The image signal VD read by the image sensor 103 is converted into a 6-bit digital signal by the A/D converter 201, and sent through the latch 202 to the latch 203. Comparators 204, 207. It is sent to latches 205 and 208. The comparator 204 receives the 6-bit image signal sent from the latch 202 and the l sent from the latch 203.
The 6-bit image signal before the clock is compared, and if the new image signal sent from the latch 202 is smaller, a cover output is output to the AND gate 206. AND gate 206 sends the comparison output from comparator 204 to latch 205 in synchronization with sampling clock SCL.

The comparator 207 compares the 6-bit image signal sent from the latch 202 with the 6-bit image signal sent from the latch 203 one clock ago.
If the new image signal sent from 02 is larger, it is compared and outputted to the AND gate 209, and the AND gate 209 synchronizes the comparison output from the comparator 207 with the sampling clock SCL and outputs it to the latch 20.
Send to 8.

When the latches 205 and 208 receive the comparator output, they send the image signal sent from the latch 202 to the CPU 211.

In addition to the comparator output and sampling clock SCL, the AND gates 206 and 209 also have an imaging connector 103.
An enable signal EN indicating a valid section of the image signal from the latches 205 and 208 is sent to the CPU 211 from the latches 205 and 208. The CPU 211 takes in the image signals from the latches 205 and 208 in synchronization with the main scanning line synchronization signal MS, thereby determining the lowest density level (hereinafter referred to as white peak) and the highest density level (hereinafter referred to as black peak) of each main scanning line. ) can be detected.

The CPU 211 determines a slice level based on the white peak and black peak detected for each line using an algorithm described later, and sends it to the comparator 210. Comparator 21
0, both signals from the latch 203 and the slice level from the CPU'211 are compared to generate a binary signal (VIDEO).

FIG. 3 shows a state in which a document is placed on the document table 101 of the document reading device (FIG. 1). In this case, the manuscript table 101
From the above reference coordinate sp, the main scanning direction is X, and the sub-scanning direction is Y.
The coordinates of the four points (XI, Yl), (X2°Y2)
, (X3.Y3), and (X4.Y4) are detected by pre-scanning the optical system.

The document cover 110 (FIG. 1) is mirror-finished so that image data outside the area where the document is placed is always black data. In order to perform the pre-scanning over the entire glass surface, main scanning and sub-scanning are performed.

The circuit diagram of FIG. 4 shows the logic for detecting the coordinates.

The image data VIDEO that has been binarized by the previous scan is input to the shift register 301 in units of 8 bits. When the 8-bit input is completed, the gate circuit 302 checks whether all of the 8-bit data is a white image, and
If s, 1 is output to the signal line 303.

F/F when the first 8-bit white appears after scanning the original
304 is set. This F/F is reset in advance by VSYNC (image leading edge signal). After that, it is left set until the next VSYNC comes.

When the F/F 304 is set, the value of the main scanning counter 351 at that time is loaded into the latch F/F 305.

This becomes the x1 coordinate value. Also, the value of the sub-scanning counter 305 at that time is loaded into the latch 306. The kneading becomes the Y1 coordinate value. Therefore, P+ (XI, Yl) is found.

Also, each time 1 is output to the signal 303, the value from the main scanning is loaded into the latch 307. This value is immediately stored in latch 308 (until the next 8 bits enter shift register 301). When the value from the main scan when the first 8 bits of white appear is loaded into latch 308, 31O(
This is compared in magnitude with the data (which is set to "0" at the time of VSYNC) by a comparator 309. If latch 3
If the data in latch 308 is larger, the data in latch 308, that is, the data in latch 307, is loaded into latch 310. Also, at this time, the value of the sub-scanning counter is loaded into the latch 311.

This operation is processed until the next 8 bits enter shift register 301. Like this, latch 308 and latch 31
If 0 data is applied to the entire image area, the latch 31
The maximum value of the document area in the X direction remains at 0, and the coordinate in the Y direction at this time remains in the latch 311. This is P2
(X2.Y2) coordinates.

F/F 312 is an F/F that is set when 8-bit white appears for the first time in each main scanning line and outputs the horizontal synchronizing signal HS.
It is reset by YNC and the first 8 bits are set to white and held until the next H8YNC. When the F/F 312 is set, the value of the main scanning counter is set in the latch 313, and is loaded into the latch 314 until the next H3YNC. Then, the latch 315 and the comparator 316 compare the magnitude. The latch 315 has an X value when VSYNC occurs.
The max value of the direction is preset. If the data in latch 315 is greater than the data in latch 314, signal 317 becomes active and the data in latch 314 or latch 313 is loaded into latch 315. This operation is performed between H5YNC and H3YNC.

If the above comparison operation is performed for the entire image area, latch 3
15 remains the minimum value of the document coordinates in the X direction.

This is x3. Also, when signal line 317 outputs, the value from the sub-scan is loaded into latch 318. This will be Y3.

Latches 319 and 320 are loaded with the main scanning counter value and sub-scanning counter value at that time every time 8-bit white appears in the entire image area. Therefore, when the document pre-scanning is completed, the count value at the time when 8-bit white appears last remains on the counter. This is (X4.Y4
).

The above eight latches (6, 11, 20, 18, 5, 1,
The data line 0.15°19) is connected to the pass line BUS of CpLl, and the CPU reads this data at the end of the previous scan.

FIG. 5 shows the flow of the document reading sequence.

First, in step 501, the optical system performs forward scanning from the left end to the right end in FIG. 1 to detect the coordinates of the document on the document table as described above.

Next, in step 502, the area in which the peak value for determining the slice level for binarization should be sampled is calculated from the coordinate data detected in step 501. For example, from the coordinates detected for a document such as the shaded area in FIG. 3, the peak value sampling area of this document is Y3.
Choosing the rectangular area bounded by Y2 and XI, X4 is actually prompting. This is because the original is normally placed as parallel as possible on the original table, and even if the original is placed at a slight angle as shown in FIG. 3, there is no risk of picking up unnecessary information from outside the original. The sampling area may be determined in a natural manner.

As can be seen from FIG. 6, when the document coordinate detection is completed, the optical system is at the point in the sub-scanning direction Ymax, and the peak value sampling start point Y2 and end point Y3 are known, so steps 504, 505, and 506 are executed. You can make a schedule to do so. That is, when the backward movement is started in step 503, the CPU 211 calculates the distance (Y m a x
-Y 2) After counting the main scanning line synchronization signals for a corresponding amount (main scanning line synchronization signals and moving distance will be described later), start detecting the white peak value and black peak value described above, and then proceed from that point. After counting the main scanning line synchronizing signals corresponding to the distance (Y2 to Y3), peak value detection is finished, and after counting the main scanning line synchronizing signals corresponding to the distance Y3, the backward movement is stopped.

Furthermore, when starting peak value detection in step 504,
It goes without saying that the enable signal EN mentioned above is set corresponding to the detected coordinates XI. and X4 as shown in FIG.

With the above operations, the white peak and black peak of the image density can be detected for each main scanning line in the document located at any position on the document table.

Next, an algorithm for determining slice levels for binarization will be explained. Using the above-described means, the CPU 211 takes in the black peak value and white peak value for each main scanning line from within the document area. Now the black peak on the i-th main scan is B
Pi and the white peak as W P i, the image data is 6
Since they are bit values, they each range from 00 (HEX) to 3F (H
EX), and BPi > W
It is Pi. The CPU is 64x prepared in RAM.
The contents of the 2-byte area corresponding to the detected data BPi and WPi in the 2-byte black peak histogram area and the 64 x 2-byte white peak histogram area are counted up one by one, and the next main scanning line is counted up. Waiting for synchronization signal MS, data BPi+ from i+1st line
I and W P ++1 are taken in, the corresponding area of the histogram is counted up again, and the process continues until the sample is completed in step 505.

However, at this time, the detected BPi and W P i are not necessarily used as histogram data.

For example, if there is a band of uniform density in the main scanning line direction, the sample values BPi and WPi from that band will be almost equal, regardless of whether it is pure white or completely black, or even at other densities. This is not suitable as information for binarization, which requires data that distinguishes background information from information. Therefore, in CPTJ, when B P i −W P i <α, B P i and W P i are not used as histogram data and are discarded, and B P i++, W P
I'll have to wait for i++. This α is a constant set empirically, and is, for example, 4 or 3. Also, in step 504, before starting sampling, the entire histogram area 64×2
It is natural to clear the X2 bar and light to O.

As a result, when the sample is completed in step 505, a histogram as shown in FIG. 7, for example, is constructed for each of the black peak and white peak. After completing the sample, the optical system returns to the starting point and completes the backward movement in step 506. Next, in step 507, the slice level is set. First, the density level showing the peak frequency of each histogram is considered to be the respective representative value.

According to the example in FIG. 7, the density of the document information area is 36 H1, and the density of the background area of the document is OA H, and for example, the median value is 20H.
Let be the slice level. There are other ways to consider determining this slice level. Finally, in step 508, the document is read and scanned, and the operation ends.

Next, the relationship between the position of the optical system during backward movement and the main scanning line synchronization signal will be explained (FIG. 8).

The main scanning line synchronization signal (H3YNC) is a regular signal generated by a crystal oscillator, etc., and there is no disturbance in the time of one cycle (it can also be thought of as a complete timer. Therefore, the position of the optical system The relationship with the main scanning line synchronization signal can be considered in terms of the relationship between the position and time of the optical system.

The optical system starts moving at a certain acceleration 11 hours after the optical system drive motor ON signal is issued, reaches a constant speed after t2 hours, and continues to move at a constant speed thereafter (Figure 8 (a), (
b)).

However, since section B can be considered as a model of uniform acceleration motion, it can be considered separately as A: stationary section, B: uniform acceleration motion section, and C: uniform velocity motion section, as shown in Figure 8 (C). I can do it.

Also, the difference in motor torque and optical system load is due to C.
It can be approximated as the difference in speed between sections (uniform motion sections).

Therefore, the times in section A and section B have almost no difference between machines and can be considered constant. In other words,
When mass producing the same type of machine, tl.

There is almost no difference in the value of t2 between machines, and if the value of one machine is measured, that value can be applied to other machines. Therefore, by measuring the time from when the optical system drive signal is issued to when the optical system completes its backward movement (image leading edge signal (FIG. 8(d)), it is possible to calculate the speed in section C. In other words, Assuming that X: distance traveled, V: speed after t3 seconds,
When tl<t<t2, when t>T2 Therefore, by measuring the time t3, it is possible to obtain ■, and the relationship between the time t and the moving distance X can be obtained.

The time t3 is measured by measuring the time from the optical system movement start signal to the reception of the image leading edge signal (signal from the optical system sensor located at the position corresponding to the leading edge of the document) by the microcomputer that controls the sequence. can be obtained by measuring with an internal timer by counting H3YNC or an external timer.

Further, this measurement may be performed by a service person or the like in a special mode when the machine is shipped from the factory or installed, and the mode is hidden from the user.

Further, this measured value t3 can be stored in a non-volatile memory or a battery-backed memory so that it will not be erased when the power is turned on and off.

Further, by performing this measurement mode using a switch located in a hidden location, a special key operation, or a combination of the above, general users can be prevented from being bothered.

Based on the data at t3 from this measurement, the document coordinates YMAX
Step 503 of Fig. 5 calculates the reversal timing necessary for
The return movement begins at . Note that the data to be stored is not limited to t3, but also the initial parameters tI+j2, . It suffices if it is X, etc.

It is also possible to invert at Y2 using a storage parameter instead of YMAX.

(Effects) By measuring the time during reversal as described above, the position of the scanning system can be accurately determined without having to install a scanning system reversal position sensor for each reversal, and without having to perform significant speed control during reverse movement. It is possible to understand the error in the image information of the original (and import it).

[Brief explanation of drawings]

Figure 3 is a drawing of the manuscript placement; Figure 5 is a discrimination flowchart; Fig. 6 is a scanning explanatory diagram; Figure 7 is a histogram diagram. Figure 8 is a time chart diagram, lOl is the platen, 103 is a reading sensor.

Claims (2)

[Claims] (1) It has an original position recognition means, a means for measuring the original scanning time, and a means for calculating the scanning movement distance based on the scanning time, and the image signal is used to determine the appropriate output corresponding to the area of the original. A document reading device characterized in that it performs processing such as importing. (2) The document reading device according to item 1, wherein the time measurement during scanning is measured in a special mode and the value is retained even when the power is turned off or the device is cleared.