JP2522707B2 - Image pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is applied to a scanner or the like, and corrects a phase error of an image pickup signal in an electric superposition portion of a plurality of line sensors (image sensor, photoelectric conversion element). The present invention relates to an image pickup device that creates a split image signal.

[Prior Art] In a scanner for printing plate making, when capturing an image of an original, a plurality of line sensors such as CCDs are used to move the original in order to cope with a relatively large original and high resolution. One-dimensional imaging (main scanning) is performed by arranging (hereinafter referred to as “optical linear”) to overlap the connecting portion so as to perform imaging of one imaging line orthogonal to the direction (sub scanning), and sub scanning. A two-dimensional image information signal is generally created together with scanning.

As an example in which such a plurality of line sensors are arranged in an optical straight line, Japanese Patent Laid-Open Nos. 63-72262 and 63-72263 are known.
The image pickup device disclosed in the publication can be mentioned.

As described above, in order to read the image information of one line in the main scanning, the driving pulse synchronized with the movement of the document in the sub-scanning direction is sequentially applied to the plurality of line sensors to derive the two-dimensional image information. . The image pickup signal derived here is
In a scanner or the like, the image is reproduced after being subjected to frequency gradation and halftone dot signal generation processing.

[Problems to be Solved by the Invention] However, in the image pickup device according to the above-mentioned conventional technique, the level of the image pickup signal in the main scanning direction is not uniform on the time axis, for example, the mechanical arrangement state changes with time. Due to the deviation of the connection due to, that is, the phase difference of the image pickup signal in the electrical superposition portion of the line sensor, the deterioration of the MTF characteristic is caused.

In such a case, a uniform signal processing means for deriving the derived image pickup signal through a slice circuit or the like is adopted, but it is difficult to obtain good image reproducibility. For example, in a reproducing system, when reproduced on a film or the like, density unevenness occurs, and when a shading process is performed, it causes nonuniformity of sharpness of a reproduced image. ing.

The present invention has been made in view of the above point, and in a relatively simple configuration, a deviation of connection portions in the main scanning direction of a plurality of line sensors from an image pickup signal of a grid pattern, that is, in an electrical superposition portion. An object of the present invention is to provide an image pickup device that creates an image signal in which the phase difference of the image pickup signal is corrected with high accuracy.

[Means for Solving the Problems] In order to solve the above problems, an image pickup apparatus of the present invention takes an image pickup signal by picking up an image of a grid pattern orthogonal to a main scanning line in each pixel in the main scanning line direction. Image signal deriving means having a plurality of line sensors for deriving, a storage means for quantizing and storing the image pickup signal, and of the image pickup signals relating to both sides of the connection part of the plurality of line sensors from the stored image pickup signal An operation unit that detects a phase and compares the phases to create a phase difference signal, and controls the timing of reading the image pickup signals of the plurality of line sensors based on the phase difference signal to control the electrical characteristics of the line sensor. Image pickup signal correction means for generating an image pickup signal in which the deviation of the dynamic superimposition portion is corrected, and the calculation means is configured to increase or decrease the output level corresponding to the grid pattern. A number is assigned to each peak of the signal to form a peak number, a pixel number corresponding to the peak number is a peak pixel number, and each line is on a coordinate system in which the peak number and the peak pixel number are two-dimensional orthogonal coordinates. The regression line for each sensor is obtained, the deviation of the regression line between adjacent line sensors is read on the coordinate system, and this deviation is created as the phase difference signal in the main scanning direction between adjacent line sensors. To do.

[Operation] In the image pickup device of the present invention configured as described above, the image signal deriving unit is configured such that an image related to a grid pattern is a plurality of, for example, optical straight lines in which connecting portions are superposed through an objective lens or the like. An image is formed on the line sensor, and drive pulses are sequentially supplied to the line sensor to perform main scanning. At the same time, it is supplied to the line sensor switching means. As a result, the image pickup signal is created in synchronization with the drive pulse.

In the storage means, the image pickup signal is supplied to the quantization means, converted into a digital signal, and then stored.

The calculation means performs peak detection of a waveform related to the image pickup signals of the line sensors on both sides of the connection portion. After this,
Obtain the equations for the straight lines of the line sensors on both sides, and then
The deviation of the connection portion in the main scanning direction, that is, the phase difference of the image pickup signal of the electrical superposition portion is obtained from the equations of the two straight lines.

Alternatively, from the detection of the maximum point, the minimum point, the zero point, etc. of the waveform inclination, the equations of two straight lines are obtained in the same manner as described above, and the deviation of the connection portion in the main scanning direction is obtained to detect the phase difference.

Further, the image pickup signals obtained by a plurality of times of image pickup are averaged, or the phase is detected from a plurality of waveforms to obtain the phase difference.

In the correction signal processing means, the drive pulse whose time axis is changed to change the read position is supplied to the corresponding plurality of line sensors based on the phase difference signal to electrically connect the line sensors. An imaging signal in which the deviation of the superimposing portion is corrected is created. Alternatively, the signal of each line sensor is once quantized and stored in the memory, and then the address for reading the memory is controlled and corrected.

[Embodiment] Next, an embodiment of the image pickup apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the configuration of an embodiment in which the present invention is applied to a scanner, and FIG. 2 shows the signal processing system in detail. Also, FIGS. 3 and 4 are diagrams relating to the description of the signal processing system.

The example shown in FIG. 1 has an image pickup system Op and a signal processing system Cs. The main image pickup system Op and the signal processing system Cs pick up an image with a clock signal having a cycle corresponding to the size of the reading range of the image recording medium Ga, and perform signal processing to improve the image quality of reproduced images thereafter. It is supposed to be given.

First, the image pickup system Op has a roller 12 for moving the test pattern Pc and the image recording medium Ga in the sub-scanning direction M, and further has a grid pattern A or an image drawn on the test pattern (measurement document) Pc. The recording medium Ga is irradiated with light from the light projecting unit 14.

Then, the obtained image light is condensed by the objective lens 18 via the reflection mirror 16 and is led out. Next, reflection / transmission is performed by the half mirrors 20a and 20b, and the CCD line sensor 22
It is incident on a, 22b, 22c and 22d. The photoelectric conversion is performed here, and the image pickup signal S ₁ from the CCD line sensors 22a to 22d,
S ₂ , S ₃ , and S ₄ are supplied to the signal processing system Cs. In this case, the read drive pulses C _K1 , C _K2 , C _K3 , and C _K4 are derived from the signal processing system Cs and are input to the CCD line sensors 22a to 22d with their time axes aligned, and one line related to the main scan. (X direction)
Is read.

Next, the signal processing system Cs includes a line sensor drive clock signal generation circuit 30, and the read drive pulses C _{K1 to} C _K4 derived _therefrom are supplied to the switching circuit 32. In synchronization with this, the CCD line sensors 22a to 22d are selected. The basic clock signal is input from the timing generator 33.

In addition, the dark correction circuit 34 that corrects the dark level and CC
A shading circuit is provided which corrects the sensitivity deviation between the pixels of the D line sensors 22a, 22b, 22c, 22d and the fluctuation of the dark signal due to the illuminance difference. The signal derived here is further supplied to the memory changeover switch 40a via the A / D converter 38. Further, the first and second memories 42 and 44 are arranged between the memory changeover switches 40a and 40b.

Further, a correction changeover switch 45 is arranged between the first memory 42 and the memory changeover switch 40b.

Further, the signal derived from the memory changeover switch 40b is supplied to the magnification conversion circuit 46. A write address counter 47 and a read address counter 48 are connected to the first and second memories 42 and 44.

Further, a bus 50 connected to the timing generator 33 is connected to a CPU 50 that controls the whole, a RAM 52 that stores a control program, the line sensor drive clock signal generation circuit 30 and a sequence control register 58.

In such a case, when the correction changeover switch 45 is connected to the memory changeover switch 40b, clock signals with different cycles based on a known licing signal supplied from the outside are sent from the timing generator 33. , CCD line sensors 22a to 22a corresponding to an image pickup range (not shown)
22d is selected.

In the embodiment having such a configuration and operation, first, the grid pattern A is imaged and the CCD line sensor 2
Image signals S _{1 to} S ₄ derived from 2a to 22d, that is, the analysis / calculation related to the image signal S ₁₀ is performed, and the phase difference information related to the connection part (electrical superposition part) of the CCD line sensors 22a to 22b. (Phase difference signal) is obtained.

In this case, the image pickup signal of one image pickup line is stored in the first memory 42, and then the CPU 52 and the RAM 52 in which the control program is stored and external instructions, that is, for each so-called image recording medium Ga, or for each work process, and for starting work every day. Under the control operation performed before, etc., the CPU 50 carries out the analysis / calculation of the image pickup signal S ₁₀ sent from the first memory 42 to the bus line Bs via the read address counter 48.

Next, the n value of the sequence control register 58 is changed based on the phase difference information obtained by the analysis / calculation, and the read drive pulses C _{K1 to} C _K4 sent from the line sensor drive clock signal generation circuit 30 are changed. Change the time axis of the transfer start signal. Image pickup signal S ₁ of the image recording medium Ga after this
To S ₄ will not have a phase difference to the electrical superimposing unit.

Hereinafter, regarding the CCD line sensor 22a that is separated from the optical linear joint, the first and second arithmetic processing relating to the detection of the phase difference information of the connection portion of the CCD line sensors 22a and 22b will be described as the third operation.
A description will be given with reference to the drawings and FIG.

The phase difference may be detected by obtaining the phase difference of the peak of each cycle for the imaging signal that changes periodically due to the reading of the grid pattern A. Therefore, in the first arithmetic processing, the coordinates (pixel number) of the peak in the main scanning direction are obtained,
In the second arithmetic processing, the peak phase difference is obtained.

First, in the first arithmetic processing, focusing on the x-th pixel (0 ≦ x ≦ n) in a predetermined range in the main scanning direction including the connecting portion,
The signal level of the pixel immediately before (x−1) th and the pixel level after (x + 1) th is compared, and if the level of the pixel of interest is higher than the pixels before and after (L _x−1 <L _x And if L _Y > L _{x + 1} ) consider that pixel to be the i-th peak. By repeating this process for the pixels in the above predetermined range (0th to nth), the coordinates of the peak of each cycle in the main scanning direction can be obtained.

Next, in the second arithmetic processing, the peak numbers and the coordinates (pixel numbers) in the main scanning direction are plotted on the horizontal axis and the vertical axis, respectively, and a straight line formula (corresponding to CCD on both sides of the connection portion ( x = a ₁ + b ₁ · i and x = a ₂ + b ₂ · i), respectively. It should be noted that the precision of phase difference detection can be improved by using a regression line that uses the least squares method when obtaining these straight line expressions. Then, the difference Δx in the value of x at the center (i ^* ) of the connection part of each equation becomes the phase difference obtained by Δx = (a ₂ + b ₂ · i ^* ) − (a ₁ + b ₁ · i ^* ).

The above second arithmetic processing is effective when the S / N ratio of the image pickup signal is not good.

Further, in the above-mentioned first and second arithmetic processing,
Main scanning is performed a plurality of times, the average of the imaged signals that are derived and input a plurality of times is calculated, and the peak of the waveform is detected from the averaged imaged signal or the maximum or minimum point of the waveform slope or zero. It is also possible to detect points.

Note that the averaging may be performed not only on the image pickup signals, but also may be calculated on each of the image pickup signals a plurality of times, and then the averaging may be performed.

Also, by differentiating the waveform and obtaining the coordinates of the peak from the point that crosses the zero level, CCD line sensors 22a and 22d
The phase may be detected.

Furthermore, the phases of a plurality of waveforms of the image pickup signal may be detected.

The value calculated in this way is detected as the phase difference information.

The phase difference information (phase difference detection signal) derived here is
Furthermore, via the bus line Bs, the sequence control register
Supplied to 58.

The sequence control register 58 stores the phase difference (phase difference detection signal) in the image pickup signal as its content,
That is, the n value is changed and the read drive pulse C sent to the CCD line sensor 22a and / or 22b to the line sensor drive clock signal generation circuit 30 based on the phase difference.
Change the time axis of the transfer start signal of _K1 and C _K2 and send.
Here, the next image recording medium Ga is imaged. Therefore,
Deviations of the optical straight lines of the CCD line sensors 22a and 22b in reading, that is, the image pickup signals S _{1 to} S ₄ in which the phase difference in the electrical superposition portion of the connection portion is corrected are obtained, and thereafter,
It is sent out as an image pickup signal S ₁₀ .

EFFECTS OF THE INVENTION According to the present invention, in a relatively simple configuration, the deviation of the connection portion of the plurality of line sensors in the main scanning direction from the image signal of the grid pattern, that is, the position of the image signal of the electrical superposition portion. An effect that an image signal whose phase difference is corrected with high accuracy is created is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the image pickup device of the present invention, FIG. 2 is a block diagram showing a detailed structure of a signal processing system incorporated in the image pickup device of FIG. 1, FIG. 3 and FIG. FIG. 4 is a diagram provided for explaining the operation of the signal processing system. 22a to 22d …… CCD line sensor 30 …… Line sensor drive clock signal generation circuit 33 …… Timing generator 50 …… CPU, 52 …… RAM 58 …… Sequence control register A …… Lattice pattern C _{K1 to} C _K4 … … Read-out drive pulse Cs …… Signal processing system, S _{1 to} S ₄ … Imaging signal Op …… Image imaging system

Claims (1)

(57) [Claims] 1. An image signal deriving means having a plurality of line sensors for deriving an image pickup signal by picking up an image of a grid pattern orthogonal to the main scan line for each pixel in the main scan line direction, and the image pickup signal being quantized. Storage means for storing the converted image, and calculating means for detecting the phases of the image pickup signals respectively on both sides of the connection portion of the plurality of line sensors from the stored image pickup signals, and comparing the phases to create a phase difference signal. And, based on the phase difference signal, an image pickup signal correction unit that controls the timing of reading the image pickup signals of the plurality of line sensors to create an image pickup signal in which the deviation of the electrical superposition portion of the line sensor is corrected, The calculating means assigns a number to each peak of the image pickup signal whose output level increases or decreases corresponding to the grid-like pattern as a peak number, and corresponds to the peak number. The regression line for each line sensor is obtained on the coordinate system in which the pixel number is the peak pixel number, and the peak number and the peak pixel number are two-dimensional orthogonal coordinates, and the deviation of the regression line between adjacent line sensors is calculated. An image pickup device characterized by reading on the coordinate system and creating the shift as the phase difference signal in the main scanning direction between adjacent line sensors.