JPH0698172A - Picture reader - Google Patents

Abstract

PURPOSE:To attain exact gradation correction to an essential object to satisfy an operator by providing the subject picture reader with a means which designates a specific area in an original, means which measures the original density of the specific area, and means which decides a gradation correction function based on the measured result. CONSTITUTION:The level of the opening of a diaphragm 3 is judged by a control circuit 27 by the output of the brightest part, that is, the maximum value peak hold circuit at the time of the end of a reciprocating pre-scan, and outputted the result to a motor driving control circuit 35. The state of the diaphragm is inputted to the circuit 27 by a potentiometer 11, and when the setting of a diaphragm 3 is ended, the returning scan is started, the set level of the clamp voltage of a clamp circuit 30 is judged by the circuit 27 by the output of the darkest part, that is, the minimum value peak hold circuit at the time of end of the returning scan, and outputted to the circuit 30. The clamp is operated by the shaded optical black of a linear sensor 12, and the darkest part of the output of the sensor 12 is matched with the minimum value of the input range of an A/D converter 15. Moreover, a diaphragm fine control is operated by the circuit 27 by the output voltage of the maximum value peak hold circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, for example, in a photographic transmission machine, an image recorded on a film is remotely received via a telephone line or a signal line, an image processing computer or the like. The present invention relates to an apparatus for reading an image from a film for sending to a sheet.

[0002]

2. Description of the Related Art A conventional photo-electric transmitter has developed a photographed film, converted a stretched print (reflected original) into an electric signal, and sent it through a telephone line. This method requires darkroom equipment and skilled darkroom work. Therefore, if an electric signal can be directly obtained from the developed film, that is, a transparent negative image (negative film) or a positive image (positive film), the work in the dark room can be omitted, and the equipment, technology and time can be shortened.

A technique for directly obtaining an electric signal from a transparent negative image or a positive image is used in a telecine used in television broadcasting.

[0004]

However, in order to convert a transparent negative image into a positive electric signal, complicated processing is required to correct the gradation. In particular, when the type of the transparent negative image or the exposure condition at the time of shooting changes, the gradation characteristics greatly change, and it becomes difficult to obtain an image signal with an optimum gradation. It is an object of the present invention to obtain an image reading apparatus capable of transmitting a high quality image signal having an optimum gradation from a transparent negative image or a positive image having different kinds and exposure conditions at the time of photographing.

[0005]

In order to solve the above-mentioned problems, according to the invention of claim 1, in the image reading apparatus,
Specifying means for specifying a specific area in the original, measuring means for measuring the density of the original in the specific area, and gradation correction function determining means for determining a gradation correction function based on the measurement result of the measuring means. Prepared

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the designating means sets the X of the original document.
The direction and the Y direction are independently set to specify the specific area.

[0007]

According to the present invention, since the original density of the specified specific area is measured and the gradation correction function is determined, the gradation can be adjusted to the specific area.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. 1 is a developed transparent film that is a subject, that is, a transparent negative image, or
It is a positive picture. Reference numeral 2 (hereinafter abbreviated as a film) is an image forming optical system for forming an image of the film 1 on an image pickup surface of an image pickup device. Reference numeral 3 denotes a diaphragm, and the brightness of an image can be controlled by a diaphragm control motor 9. An illumination system 7 illuminates the back surface of the film 1. Reference numeral 12 is a linear sensor that converts the image of the film 1 formed by the imaging optical system 2 into an electric signal, and is mechanically moved by a linear sensor moving motor 10 to a plane perpendicular to the longitudinal direction of the linear sensor. Enter a realistic image. Instead of moving the linear sensor 12, the subject 1 may be moved, but since the moving speed must be changed when the imaging magnification of the optical system 2 is changed, control becomes difficult. Reference numeral 14 denotes an analog gradation correction circuit that corrects the gradation of the analog video signal obtained from the linear sensor 12, and is an amplifier capable of selecting linear or non-linear amplification characteristics, for example. Reference numeral 15 denotes an A / D converter that converts the gradation-corrected analog video signal into a digital signal.

Reference numeral 16 is a digital gradation correction circuit for correcting the gradation of the digital video signal. A one-line memory 17 has an address terminal and a data input / output terminal, and temporarily stores the gradation-corrected digital video signal.
Reference numeral 4 is a reflective original document such as a paper on which characters of a photographic task and an explanation (caption) are written. Reference numeral 6 denotes a caption illuminating device for illuminating the reflection original 4 and uses an LED (light emitting diode) here. Reference numeral 5 denotes a caption image forming optical system for forming an image of the reflection original 4 on the linear sensor 13. The reflection original 4 is sent by a reflection original feeding motor 8 in a direction perpendicular to the longitudinal direction of the linear sensor 13, and a planar image is input. The linear sensor 13 may be moved without moving the reflection original 4. Linear sensor 13
The analog video signal obtained by the
Is converted into a binary signal. Reference numeral 31 is a one-line memory that temporarily stores the binary signal. Reference numeral 19 is a synthesizing circuit for synthesizing the signal from the 1-line memory 17 and the signal from the 1-line memory 31. Reference numeral 20 denotes a D / A converter which converts the combined video signal into an analog signal. Reference numeral 21 denotes a modulation circuit, which is a circuit that performs modulation necessary for electric transmission. 11
Is a potentiometer that works in conjunction with opening and closing of the diaphragm 3.
The signal is input to the control circuit 27 that controls the transmitter. Reference numeral 22 is a mode selector for selecting a digital gradation correction mode, and can select three modes of an auto mode, a correction mode and a cursor mode. Reference numeral 23 is a changeover switch for changing over depending on whether the film 1 is negative or positive. 24
Is a density setting volume that operates in the correction mode and sets the overall density level of the image to be transmitted, and 25 also operates in the correction mode to change the correction characteristic of the digital gradation correction circuit 16, that is, the slope of the gamma characteristic. So-called hard tone,
A tilt setting volume for adjusting the degree of soft adjustment, 26 is a switch input circuit for inputting a signal from the mode selector 22 and the changeover switch 23 to the control device 27, and 28 and 29 are X and Y cursor operation volumes in the cursor mode. Are provided with potentiometers which are interlocked with the movements of the X cursor and the Y cursor, respectively, and the potentiometer signals are input to the control device 27. Reference numeral 30 denotes a clamp circuit, and the clamp level is controlled by the control device 27. A peak hold circuit 32 stores the maximum value and the minimum value of the output of the linear sensor 12, and outputs it to the control device 27. 33 is a digital video signal line, 34 is a linear sensor 1
2, 13 and 1 line memories 17 and 31, a clock generation circuit for supplying a clock signal, and 35 is a motor drive control circuit which is controlled by the control circuit 27 to cause a reflection and document feed motor 8,
The drive of the diaphragm control motor 9 and the linear sensor movement motor 10 is controlled. Obtaining high-quality images by directly converting a transparent negative or positive image into an electric signal and transmitting the electric signal The most important problem with this device is the problem of how to determine the optimum exposure for the transparent negative or positive image of the subject. Then, there is a problem of how to perform gradation correction. In order to solve this problem, in this apparatus, pre-scanning for preliminary scanning is performed prior to transmission. This point will be described in detail. Prescan starts by pressing a prescan start switch (not shown). Here, the diaphragm 3 is previously narrowed down so that the linear sensor 12 is not saturated with any subject before the prescan. When the prescan starts, the peak hold circuit 32 starts operating. The peak hold circuit includes a maximum value peak hold circuit and a minimum value peak hold circuit. The peak hold output is input to the control circuit 27.

The prescan is reciprocated with respect to the scan screen. Maximum value at the end of the prescan going to (the brightest part)
Based on the output of the peak hold circuit, the control circuit 27 determines how much the aperture 3 should be opened, and the motor drive control circuit 3
Output to 5. The state of the diaphragm is input to the control circuit 27 by the potentiometer 11. When the setting of the diaphragm 3 is completed, the return prescan is started. The control circuit 27 determines how much the clamp voltage of the clamp circuit 30 should be set by the output of the minimum value (darkest part) peak hold circuit at the end of the return prescan, and outputs it to the clamp circuit 30. The clamping is performed by the light-shielded several pixels (optical black) of the linear sensor 12. Therefore, by changing the clamp voltage, the minimum value (darkest part) of the image part of the output of the linear sensor 12 is A / D.
It is adjusted to the minimum value of the input range of the converter 15.

Further, the control circuit 27 finely adjusts the diaphragm with the output voltage of the maximum value peak hold circuit. In this way, the linear sensor 12
The maximum value and the minimum value of the output signal of are matched with the input range of the A / D converter 15. The pre-scan is transmitted at a higher speed than the scan because it is an electric transmission. The analog gradation correction circuit 14 differs depending on whether the film 1 is a negative image or a positive image. Here, FIG. 2 is a correction characteristic curve of the analog gradation correction circuit. In the case of a negative image, image information is concentrated on the side of lower density, and as a result, the output voltage of the linear sensor is low as shown by the curve a in FIG. It is desirable to have a characteristic that the amplification degree becomes high at the level. This can be done to some extent by the digital gradation correction circuit after A / D conversion, but in the correction by the digital value, if the inclination of the correction characteristic curve is made too large, the gradation becomes large and the false contour Will be the cause.

Therefore, a satisfactory gradation correction can be obtained by first performing the analog gradation correction in the front stage and then performing the digital gradation correction in the rear stage. In the case of a positive image, the film 1 is the image that can be viewed as it is, and a large gradation correction is not required. Therefore, in the analog gradation correction in the previous stage, as shown in FIG. The amplification characteristic of the amplifier as the gradation correction circuit 14 may be linear. If some gradation correction is required, it can be performed by the digital gradation correction circuit 16 in the subsequent stage.

In this way, the maximum value of the video signal is adjusted by the setting of the diaphragm 3, and the minimum value of the video signal is adjusted to the input range of the A / D converter by the setting of the clamp voltage (or the offset to the amplifier). Is converted to. The digital signal is input to the digital gradation correction circuit 16 and final gradation correction is performed. There are three types of modes that determine the characteristics of the gradation correction circuit, and any one of them can be selected by the mode selector 22. When the film 1 is a positive image, the state of gradation can be visually observed, and the correction itself is easy. The problem is with negatives. Therefore, only the case where the subject is a negative image will be described below.

The gradation characteristic of a negative image greatly changes depending on the exposure condition and the developing condition at the time of photographing. The characteristics of the digital gradation correction circuit (hereinafter referred to as the gradation correction curve)
Two parameters need to be set to determine. One is information relating to the density at which the density of a certain specific video signal level is finally reproduced, and the other is the gradient of the gradation correction curve near the specific video signal input level. Information about, that is, the degree of hard and soft tones. Hereinafter, these are referred to as density information and inclination information.
FIG. 3 is a diagram showing a digital gradation correction characteristic curve. The input video signal level of c is reproduced at a density of d on the γ-1 gradation correction curve and at a density of e on the γ-2 gradation correction curve. The vertical axis is brighter toward the top (white on monochrome films), that is, point d is brighter than point e.

Further, at the point c, the curve of γ-1 has a gentler slope than the curve of γ-2. So the curve of γ-1 is
The information at point c is whiter than that of the γ-2 curve, and
The change in density near the point will be reproduced gently. Note that the curves γ-1 and γ-2 are sloping down to the right, that is, the reproduced density is white when the video signal level is low, which means that the film is a negative image, and in the case of a positive image, it is naturally an upward curve.

As described above, there are three modes for determining the characteristics of the digital gradation correction circuit: the auto mode, the correction mode and the cursor mode, which can be satisfied for a film in any state. It is possible to transfer images. The auto mode, which is the first mode, is a fully automatic mode and is a mode for automatically correcting the difference in gradation due to the difference in the exposure conditions and the development conditions. Obtained by prescan,
The gradation of the transparent negative image of the subject is judged from the outputs of the maximum value peak hold circuit and the minimum value peak hold circuit and corrected. For example, when the maximum peak hold output is small (the brightest part is dark) and the aperture must be widened, the negative image is overexposed, so the information is gathered at the low level of the linear sensor, and The adjustment curve is adjusted to the overexposed negative image. For example, it is a γ-2 correction curve in FIG. Similarly, if the maximum peak hold output is large and you do not have to open the aperture so much, the density of the negative image is generally thin and the exposure is underexposed, so information is gathered at the high level of the linear sensor. The characteristics of the gradation correction circuit may be adapted to an under-image. For example, it is a γ-1 correction curve in FIG. As described above, the auto mode automatically determines the characteristics of the digital gradation correction circuit 16. The correction mode, which is the second mode, artificially changes the characteristics of the digital gradation correction circuit determined in the auto mode, and the degree of change is determined by the density setting volume 24 and the inclination setting volume 25. is there. Digital gradation correction circuit 1 to be set in the automatic mode according to the setting positions of these two volumes
From the characteristics of 6, how much the degree of hard / soft tone, that is, the slope is changed, and how much the overall density (in the received image)
Determines whether to turn white or black.

The density setting volume 24 and the inclination setting volume 25 in the correction mode serve as a relative measure as to how much the gradation characteristics to be set in the auto mode are changed. In the cursor mode, which is the third mode, an arbitrary point on the scanning screen is set by the X and Y cursors in FIG.
It is set by the volume control No. 5 to determine the entire gradation correction. FIG. 4 is a diagram showing the relationship between the cursor and the transmission screen for explaining the cursor mode. When the cursor mode is selected, one round-trip prescan for determining the diaphragm and clamp voltage is performed, and then another round-trip prescan is performed. And in the second round trip, after setting the diaphragm and clamp voltage,
The video signal level of the point P (very narrow area) designated by the intersection of the X and Y cursors is taken into the control circuit 27.

In FIG. 4, the position of the Y cursor 42 is input as a voltage to the control circuit 27 by the Y cursor pointing potentiometer 43 which is interlocked with the Y cursor 42, and the position of the X cursor 41 is in the sensor block 44 to which the linear sensor 12 is attached. Attach a light emitting element 45 such as an LED,
The linear sensor 12 is provided by a light receiving element 46 such as a photodiode in which the light from the light emitting element 45 is attached to the X cursor.
A signal is obtained when is aligned with the setting position of the X cursor 41,
It is input to the control circuit 27.

The position of the intersection P is specified by the positions of the X cursor and the Y cursor. The input of the signal at the cursor set point P can be performed by the maximum value peak hold circuit. That is, the cursor set point P after the start of the second prescan
Until the maximum value peak hold circuit is reset, and the maximum value peak hold circuit is operated when both the main scanning sub-scanning position reaches the cursor setting point P, the video signal level at the cursor setting point P is changed. It can be input to the control circuit 27.

In FIG. 4, arrow S-1 indicates the main scanning direction of the linear sensor, and arrow S-2 indicates the sub-scanning direction of the linear sensor. The video signal level of the cursor set point P is input,
When the set values of the density setting volume 24 and the inclination setting volume 25 that determines the degree of hard / soft adjustment are determined, the video signal level at the cursor set point P is set to the set density, and
Digital gradation characteristics that satisfy the degree of soft tone are set. For example, the video signal input level at the cursor set point P is c in FIG. 3, the output density set by the density setting volume 24 is f, and the tilt information set by the tilt setting volume 25 is the curve γ2.
If it is larger than that, the curve γ3 is obtained.

The cursor mode is a mode for externally specifying the density information and the tilt information in this way. As described above, the analog gradation correction is performed in the former stage, and the above-mentioned 3 is performed in the latter stage.
The digital tone-corrected signal in one of the modes is rolled into the one-line memory 17. This memory is for band conversion for converting the signal of the linear sensor 12 of a relatively high speed into a signal of a low speed comparable to that of a conventional electric transmitter using a telephone line. The video signal band-converted by the 1-line memory 17 is modulated by the modulation circuit 21 and sent out. Here, 33 is a digital video signal line from which a high-speed digital video output can be extracted and used.

FIG. 5 shows an example in which a microcomputer is used as the control circuit 27 of FIG. The same reference numerals as in FIG. 1 indicate the same effects. Reference numeral 51 is a CPU, 2 is a ROM containing a program, and stores a program for the CPU 51 to operate as a control circuit. Reference numeral 53 denotes an input board, which corresponds to the switch input circuit 26 in FIG.

The output of the D / A converter 54 is connected to the clamp circuit 30 of FIG. 1 and supplies a clamp voltage. A / D
The converter 56 is an A / D converter with a 6-channel analog multiplexer, and outputs the potentiometer 11 interlocking with the diaphragm 11 shown in FIG. 1, the maximum value output of the peak hold circuit 32, and the minimum value output thereof. , 6 signals of the output of the concentration setting volume 24, the output of the inclination setting volume 25, and the output of the Y cursor operation volume 29 are input. The clock generation circuit 34 normally controls writing to and reading from the line memory 56. The digital gradation correction circuit 16 is composed of a RAM (random access memory),
In normal operation, the address selector 57 causes the A / D converter 15 to operate.
Of the output signal of the A / D converter, and works to correct the gradation of the output signal of the A / D converter. The digital gradation correction circuit 16 composed of RAM can create a look-up table by RAM so that a large number of correction characteristics can be obtained with a small memory capacity. Especially as digital gradation correction, auto mode, correction mode,
If the three modes of the cursor mode can be selected, if the digital gradation correction circuit 16 is composed of a ROM (read only memory), a memory capacity is required in proportion to the number of correction characteristics, and a ROM with a huge memory capacity is required. I have to prepare. Therefore, a RAM is used as the digital gradation correction circuit 16 in this embodiment.

Reference numeral 64 is a data bus, and 65 is an address counter. Address selectors 57, 58, 59 are CPUs
51 is the digital gradation correction circuit 16 or the line memory 5
Only when 6 is accessed, the CPU 51 switches to the address bus 60 or the control bus 61. In the bidirectional bus driver 62, the CPU 51 uses the digital gradation correction circuit 16,
Data is exchanged by the bidirectional bus 63 only when the 1-line memory 56 and the D / A converter 20 are accessed. In other cases, the correction circuit 16 and the 1-line memory 56 and the D / A converter 20 are exchanged. It serves to separate from the CPU 51.

With such a configuration, the digital gradation is used for the calculation to obtain the gradation curve from the information obtained by the prescan, the digital gradation correction curve setting mode and the density information, the inclination information, and the like. The RAM constituting the correction circuit 16 and the memory of the 1-line memory 56 can be used, and it is not necessary to provide a separate memory for each.

Next, in the case of processing the cursor mode, that is, the mode in which the density of the film in the minute range P at the intersection of the X and Y cursors is measured and the density of the range P and the slope of the γ characteristic curve are designated by the microcomputer. This will be described below. FIG. 6 is a flowchart of the cursor mode. In (1), measure the position of the Y cursor by potentiometer. Start scanning the line sensor in (2). (3) Repeatedly reset analog peak hold until the line sensor reaches the X cursor position in (4). When the line sensor comes to the X cursor position in (5),
A counter value (the number of main scanning lines corresponding to the width in the X axis direction) that determines the time in the sub scanning direction is set. (6) A pulse having a certain width is output at the Y cursor position in the main scanning direction. Peak hold is performed only during this pulse period. In (7), the counter set in (6) is decremented by -1. When the counter reaches 0 in (8), that is, when the sub-scan is performed for a certain period, the maximum and minimum densities are read. By performing the calculation of (maximum + minimum) / 2 in (10), the average density of the spot portion is calculated (1
In 1), the spot measurement data of point P is obtained by the microcomputer. FIG. 7 shows X in the transmitted image of the film.
A portion where spot photometry is performed at an intersection P of the cursor and the Y cursor is shown. The width of the pulse P _X in the sub-scanning direction is the reading time of the line sensor output in the sub-scanning direction, whose width is determined by the counter set in FIG. 6 (5). Main scanning direction pulse P _Y
Is the duration of the peak hold operation of the line sensor output in the main scanning direction with a pulse of constant width generated by the Y position detection.

The operator observes the transmission screen with a finder device (not shown) guided to a movable reflection mirror (not shown) provided in front of the linear sensor 12 while observing X.
By moving the cursor and the Y cursor, their intersection P can be set to an arbitrary portion of the transmission screen. X cursor 4
1, the Y cursor 42 is a colored transparent resin plate having a width of pulses P _X and P _Y , respectively, in the finder, and a black line is provided at the center thereof, so that the operator can easily confirm the photometric range with the finder. So convenient.

FIG. 8 shows an embodiment of the peak hold circuit 32. Reference numerals 81 and 82 denote switches, and a pulse P in the main scanning direction.
_It turns ON only while _Y is rising. Reference numerals 83 and 84 are diodes, 85 and 86 are capacitors, and 87 and 88 are reset switches, which are controlled by a reset pulse P _R. Reference numerals 89 and 90 are buffer amplifiers. While the line sensor 12 is scanning, the reset switches 87 and 88 are closed in portions other than the setting position of the X cursor 41, and the capacitors 85 and 86 are not charged. Further, since the switches 81 and 82 are turned on only while the pulse P _{Y in the} main scanning direction is rising, at the point P, the switches 81 and 82 are turned off.
Since N and the switches 87 and 88 are turned off, the peak hold is performed and the minimum density and the maximum density are fetched by the microcomputer. The microcomputer determines the density at the point P by calculating the average of the maximum value and the minimum value as described above.

[0029]

Since the gradation correction function is determined based on the original density of the specified specific area, accurate gradation correction can be performed on the specific area, for example, the main subject, and an image with gradation satisfying the operator can be obtained. Obtainable.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an analog gradation correction characteristic curve.

FIG. 3 is a diagram showing a digital gradation correction characteristic curve.

FIG. 4 is a diagram showing a relationship between a cursor and a transmission screen.

FIG. 5 is a block diagram showing an embodiment in which a control circuit is composed of a microcomputer.

FIG. 6 is a flowchart of a cursor mode.

FIG. 7 is a diagram illustrating photometry at the intersection of cursors.

FIG. 8 is a circuit diagram showing an embodiment of a peak hold circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Film 12 ... Linear sensor 14 ... Analog gradation correction circuit 15 ... A / D converter 16 ... Digital gradation correction circuit 20 ... D / A converter 21 ...・ Modulation circuit 22 ・ ・ ・ Mode selector 33 ・ ・ ・ Digital video signal line

Claims (2)

[Claims] 1. A designation unit for designating a specific region in a document, a measuring unit for measuring a document density of the specific region, and a gradation correction for determining a gradation correction function based on a measurement result of the measuring unit. An image reading apparatus comprising: a function determining unit. 2. The designating means is configured so that the X-direction and the Y-direction of the original document.
The image reading apparatus according to claim 1, wherein the direction is set independently of each other and the specific area is designated.