JPH07112241B2 - Image scanning device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image scanning device for an object to be scanned using a linear image sensor.

[0002]

2. Description of the Related Art An image scanning apparatus as disclosed in Japanese Laid-Open Patent Publication No. 56-23072 and the like first quantizes (5 bits) an image signal output for each unit area of a document by preliminary scanning, and quantizes the quantization. Threshold data is created using all the signals obtained. After the threshold has been obtained, the original is read by the image sensor during the main scanning to binarize the image signal. Further, image signal processing as known from JP-A-57-80858 is performed by reading a microfilm, a film frame thereof and a film outside thereof with a photoelectric converter and binarizing a signal from the photoelectric converter. The black signal or white signal in one scanning line is counted. Then, the area outside the microfilm is considered to be judged, and the band compression function is improved by setting the signals other than the film to be read (frame frame (horizontal frame and vertical frame) and the film outside thereof) to white signals. .

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the image scanning device such as Japanese Patent Laid-Open No. 72, when a holder or the like for holding the object to be scanned is detected during the pre-scan, the image signal including the holder will be quantized to create threshold data. . Therefore, the density level or the like is affected when an image is scanned during main scanning, resulting in an image with poor image quality. In the image signal processing disclosed in Japanese Patent Laid-Open No. 57-80858, the signal from the photoelectric converter is binarized as described above, and the frame frame (horizontal frame and vertical frame) is detected by the number of black signals. Is. Therefore, if it is a microfilm in which only characters and figures are exposed, the frame can be detected by binarizing and counting the black signal, but in the case of a photographic film having a multi-step gradation, If binarized and the black signal is counted, the frame frame portion cannot be accurately detected depending on the exposure state of the film and the subject (black object). Therefore, the present invention is
Even if the image signal of the scanned object having multiple gradations and the holder or the like that holds the scanned object is read, the image signal of the holder or the like is discarded and the image signal of only the scanned object having multiple gradations It is an object of the present invention to provide an image scanning device capable of obtaining the above.

An image scanning apparatus of the present invention is an image which is provided in the vicinity of an image plane of an imaging optical system and which scans an object to be scanned having multi-step gradation and outputs image information. A sensor (15), an A / D converter (46) for converting image information from the image sensor into an n-bit (n ≧ 2 natural number) digital signal, and a digital signal from the A / D converter. On the basis of the classification means (52) for distinguishing whether it is the holder part for holding the scanned object or the scanned object, and the standardization coefficient of the digital signal from the A / D converter, A processing unit (5) for outputting only the digital signal of the scanned object excluding the digital signal of the holder portion of the scanned object that is sorted by the sorting unit.
2) and are included.

According to the present invention, when the density of the image information of the film is output by, for example, an 8-bit digital signal (0-255 level), it is determined that the dark image information of 7 levels or less is in the holder portion (light shielding state). Then, only the digital signal of the film is output excluding the digital signal of 7 levels or less. Therefore, since the standardization coefficient is obtained only by the information of the film, it is possible to obtain an appropriate standardization coefficient and obtain high image quality information. Further, even the maximum density portion of the film allows light to pass therethrough, so that the digital signal of the maximum density portion of the film does not fall below 7 levels.
Further, since the under-exposure or over-exposure of the film can be determined only in the dark portion of the film, only the digital signal of the dark portion of 8 to 73 levels is output to obtain the standardization coefficient, excluding the digital signal of 74 levels or higher. be able to.

[0004]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the construction of the main parts of an optical system and a mechanical system according to an embodiment of the present invention. In FIG. 1, the subject is a 35 mm film and is indicated by (1). The film (1) is held by a film holder (3) that is rotatably attached to an XY stage (2) that can move vertically and horizontally. (4) is a dial for moving the XY stage vertically and horizontally. The film holder (3) has a window (5) corresponding to one frame of the film, and the film is sandwiched between flat glass sheets provided on both sides of the film (5).

The film is transilluminated and, for this purpose, an illumination lens (6), a filter (7), a heat ray transmissive dichroic mirror (8), a lamp (9) and a reflective mirror (1).
0) constitutes an illumination optical system. Reference numeral (11) is a zoom lens, and a zooming motor (12) with potentio is moved back and forth in the optical axis direction to obtain an appropriate magnification with a variable magnification raise (not shown). Further, the zoom lens (11) has a built-in diaphragm so that it can be opened and closed by a diaphragm motor (13) with a potentio. A flip-up mirror (14) after the zoom lens (11)
Is provided and is used to display an optical image in the viewfinder during trimming. The mirror (14) is flipped up during image scanning.

A linear image sensor (15) performs main scanning on the image plane, and the sensor (15) is a substrate (16).
It is placed in. The substrate (16) can be moved by a screw (17) in a direction perpendicular to the longitudinal direction of the image sensor (15), which serves as a sub-scan. The feed screw (17) is rotationally driven by a motor (18) via a gear.

Limit switches (19) and (20) are attached to both ends in the sub-scanning direction to generate a stop signal at the stroke end. Further, in addition to this, a photointerrupter (21) for detecting the start position is provided for the accurate detection of the image input scanning start position. For example, when a color image is input, three photo filters (7) or It is used for precise positioning when color separation is performed using four sheets and image scanning is sequentially performed for each color.

An example of the start position detecting photo interrupter is shown in FIG. This is the substrate (16) in which the deepest position of the cut of the fixed thin plate (22) having the wedge-shaped cut and the center of the light emitting element (23) and the center of the light receiving element (24) are aligned with each other. It is a combination of thin plates (25) attached to and is intended to detect the moment when light is transmitted. However, the limit switch (20) is in operation at the initial start position, and at this time, the photo interrupter (21) is in a light-shielding state.

Further, a photo interrupter (26) which does not require so much accuracy is provided for detecting the sub-scanning completion position. Since the photo interrupter (26) can be manually set at any position in the sub scanning direction, the size in the sub scanning direction can be set arbitrarily. Before describing the signals and the like in the embodiment of the present invention, an outline of one example of the operation sequence of the apparatus of the embodiment will be described with reference to the operation flowchart of FIG.

When the power is turned on, the lamp (9) is turned on. In this state, when the sensor board (16) is not at the stroke end on the limit switch (19) side, the board (16) is immediately driven at high speed and the switch ( 19) Stop at the position where it turns on. In this state, the diaphragm is opened and zooming and XY movement are performed, and if necessary, the film holder is rotated by 90 ° for trimming. When trimming is completed, if the preliminary scanning start switch is turned on, the diaphragm is narrowed down to the set aperture value according to the setting value of the zooming magnification, and immediately thereafter, the preliminary scanning is performed in the sub scanning direction limit switch (19) side up limit switch (20).
Started towards the side.

The specific aperture value is an aperture value such that the linear image sensor (15) is not saturated even with the maximum amount of light transmitted through the film. Further, this preliminary scan is usually a higher speed scan than the image input scan which is subsequently performed. The purpose of pre-scanning is to extract information about density from the film containing the subject to which an image is to be input in advance, provide the best image plane illuminance in the subsequent image input scanning, and automatically select the gamma correction curve. To obtain a good image signal. The measurement of the film density data is started at the time of detecting the change of the stop position detecting photo interrupter (26) from the light shielding to the light transmitting in the image input scanning, and when the limit switch (20) is turned on or the start position detecting photo. Interrupter (2
The process ends when 1) is shielded from light. The preliminary scanning itself is also completed by turning on the limit switch (20), the substrate (16) is stopped at the stroke end on the side of the limit switch (20), and is placed in a standby state for image input scanning.

Thereafter, when the image input scanning start switch is turned on, the substrate (10) is driven at a constant speed in the direction opposite to the pre-scanning, and the image sensor (1
The image signal is output from 5). However, immediately before the start of the image input scanning, the aperture of the diaphragm is adjusted and fixed so that the image sensor is not saturated and the image illuminance is as high as possible.

The image input scanning ends after detecting a change from light transmission to light shielding of the stop position detection photointerrupter (26). After this, the sensor substrate (16) is driven at high speed to the position where the limit switch (19) is turned on, and returns to the standby state immediately after the power is turned on. Of course, the sequence from the preliminary scanning to the image input scanning can be automatically continued without using the image input scanning start switch.

The apparatus according to the present invention is provided with two kinds of reset switches for interrupting the image input scanning in the middle thereof. One of them is a reset for saving the measurement data, which returns the substrate (16) to the start position of the image input scanning. The other one is a reset for clearing the measurement data, whereby the substrate (16) is driven at high speed toward the pre-scanning start position, that is, the stroke end on the side of the limit switch (20), and enters a standby state immediately after the power is turned on. The former is effective when scanning is performed again without changing the trimming conditions, and the latter is effective when changing the trimming conditions or replacing the film.

FIG. 4 is a block diagram of a signal system of the image scanning apparatus according to the embodiment of the present invention, and particularly shows a portion related to the signal processing system. 4, the linear image sensor (15) to the A / D converter are shown in the upper part, the aperture control circuit of the zoom lens is shown in the central part, and the gamma correction circuit is shown in the lower part. The linear image sensor (15) is driven by the sensor drive circuit (41) and is operated in a volume time determined in consideration of the usage environment temperature range, the light source light amount, and the like. The output of the sensor (15) is amplified by the preamplifier (42), and the light shielding part (optical black part) provided in a part of the sensor by the subsequent dark current correction circuit (43).
Is clamped using a clamp pulse (44) so as to be a standard level, and the floating due to the dark current component is corrected. The first γ-correction circuit (45) is an analog γ-correction circuit, and keeps the number of bits of the A / D converter (46) within a reasonable range, for example, within 8 bits, and also digitizes noise and false artifacts by subsequent digital processing. It is provided so as not to generate limbs.

If a negative film is considered as a subject, the gamma value of the negative film is usually about 0.6 to 0.7, though it varies depending on the developing conditions, the film used, etc., and when this is used as a positive image signal, printing is performed. It is necessary to perform gamma correction similar to paper. There are several gamma values for photographic paper, from soft to hard, but pergamma values from 1.5 to 3.5.
Ranges of rank are used. Therefore, it is necessary to prepare a value corresponding to the gamma correction in this device.

However, if the gamma correction is all performed digitally, for example, the density of a negative film is high, so that the quantization is relatively coarse in a portion where the output level of the image sensor is low and image deterioration such as a false ring portion occurs. Will cause Therefore, in the embodiment, the A / D converter (4
An analog γ correction circuit is provided before 6), and by setting the gamma value here to 0.4, for example, the low level output is expanded and the effect of finely quantizing the white part in the positive image is obtained. ing. It should be noted here that a large gamma value on a photographic printing paper handling a positive image corresponds to a small gamma value in the analog gamma correction circuit (45) handling a negative image.

The A / D converter (46) used here is assumed to have a linear characteristic that the input analog signal is divided into equal levels, but of course it is a non-linear characteristic having the characteristic of the first gamma correction circuit (45). That is, the circuits (45) and (46) may be replaced with one A / D converter with fine quantization level jumps at low level. In the embodiment of the present invention, the output digital signal of the A / D converter (46) thus obtained is subjected to two kinds of processing in the preliminary scanning, and the effective scanning range (the photo interrupter (26) and the limit switch (in FIG. 1) are processed. The maximum value and the minimum value of the output level of the sensor (15) in the area scanned with (20) are obtained.

(47) is a maximum detection circuit, and (48) is a storage circuit for storing the detected maximum value. Here, the maximum value is detected digitally, but of course, the analog signal in front of the A / D converter (46) may be peak-held to obtain it. Also (49),
(50) is a minimum value detection and storage circuit, respectively. A light-shielding dark area detection circuit (51) is particularly connected to the minimum value detection circuit (49). The function of this circuit (51) is to prevent the influence on the minimum level by identifying the film holder other than the film as the object when it happens to enter the scanning area. More specifically, the light-shielding dark area detection circuit (51) detects by using the difference between the sensor output of the maximum density of the film and the sensor output of the light-shielding portion (holder portion). For this reason, the fogging on the sensor surface due to the stray light of the optical system must be sufficiently reduced.

FIG. 5 is a block diagram showing an example of a circuit for obtaining the minimum sensor output level. (52) A ROM (read-only memory) that outputs 16 bits at an 8-bit address. There are 256 possible input codes, of which 0 (00), which corresponds to the black level side.
7,000,000 to 7 (00000011) and 7
For 4 (01001010) and above, 16 outputs are always logic zero. Levels 8 to 73 are divided into 16 in 4 level increments. For example, output 0 is logic 1 for input levels 8 to 11, output 1 is logic 1 for 12 to 15, and Similarly, from 70 to 73, the output 15 becomes logic 1.

In light-shielded areas such as film holders, the data is less than 7 levels, while in bright areas of the film exceeds 74 levels, both of which are not detected by this circuit. R
Two-input AND gates (53) to (68) are connected to each of the output lines of the OM (52), and a data clock (69) is applied to one input of the AND gate.

As a result, the input level is 1 of the output of the ROM.
The corresponding AND gate generates a pulse only when a logic 1 is output to the book. Counters (70) to (85) are connected to the outputs of the AND gates (53) to (68) to count the pulses. Also, counters (70) to (8
The output of 5) is AND gates (86) to (1
01) to the SR flip-flops (102) to (1)
17) is connected so that a logic 1 is output to the output of the SR flip-flop only when the counter counts a certain number or more of pulses. As a result, the minimum value detection circuit for the digitized sensor output detects a level range in which the sum of pixels having the same output level accounts for a certain ratio or more with respect to the sum of the screen areas in the scanned range. Become. That is, the fact that the output of the flip-flop becomes logic 1 means that the film density in the corresponding level range occupies a certain area or more of the screen. Since the fixed area varies depending on the read area, in order to make it correspond to the area ratio, the counter is set to a presettable counter and its preset value is changed according to the scanning area, that is, the position of the stop position detection photointerrupter (26). You can do it.

Here, the minimum value detection circuit is the A / D converter 46.
It can also be configured to process analog values before the.
The counter and the SR flip-flop are reset using the reset signal (117) immediately after the start of the preliminary scanning.
The clock (69) is generated only during the preliminary scanning. (118) is a priority encoder, and 1
Six SR flip-flops (102) to (117)
It is provided in order to code and output the one having the lowest level that outputs the logic 1 among them. The output of the priority encoder (118) is the ROM (11
9) is connected to the ROM (119), and the standardization coefficient used for standardizing the input data range and limiting the data within a certain range (for example, the range from 0 to 192) is written in advance. It is rare.

Now, returning to FIG. 4, the operation around the ROM (119) in the image input scanning will be described again.
The 8-bit normalization coefficient which is the output of the LUT (lickup table) (119) of the ROM is multiplied by the output of the A / D converter (46) in the image input scanning digital multiplier (120). At this time, standardization should not be performed similarly for all detected minimum values,
In that sense, standardization is hard to say.

That is, in the area where the minimum detection value is small, the standardized data range may be, for example, a range from 0 to 192, but the value of 192 is gradually decreased as the minimum detection value increases. . However, here, the side of 192 is the inverting circuit (1
In 21), the result of obtaining the one's complement is described, and therefore, it means the side of higher density in the film.

When the minimum value is not detected by the minimum value detection circuit within the predetermined level (in the range of 8 to 73 in this embodiment), the correction coefficient is no longer constant and the multiplier (12
The output of 0) changes according to the level range of the input data. The purpose of doing this is to avoid over-correction for a film that originally has only a limited density range.

In this way, the output of the multiplier (120) whose level range is kept within a certain range is subsequently stored in the ROM.
Is added to the LUT (lickup table) (122) as part of the address. The remaining 3 bits of the address of the ROM (122) are connected to the output encoder (124) of the reference gamma selection switch (123), and any one of the five reference gamma curves can be selected here.
The output of the ROM (122) is output as it is, the high-speed digital output OUTH and the 1-line memory (1
It is possible to selectively output a low-speed digital output OUTL which is input to 25) and subjected to speed conversion to a low speed and then output. The OUTL is effective for photographic transmission or the like through a telephone line. The 1-line memory (125) includes an inverting circuit (12
It may be provided before and after step 1).

Further, in this embodiment, in order to normalize the data and keep it within a predetermined range, the predetermined gamma value changes depending on the level because it is multiplied by a predetermined normalization coefficient corresponding to the minimum detection value. When the multiplier (120) is combined and replaced with one ROM and used as an LUT, standardization while keeping the gamma value is possible. Subsequently, the control of the diaphragm will be described.

Two control signals are input to the aperture control circuit of FIG. 4 from a control circuit (not shown). One of them is a waiting signal and commands whether the apparatus is in the waiting state or the scanning execution state. The other one is a diaphragm data selection signal, which is a signal indicating whether the scanning is being executed, the preliminary scanning is being performed, or the image input scanning is being performed. When the apparatus is in the waiting state, the optimum aperture value calculation circuit (126) outputs the aperture opening voltage as the output signal (127) to the aperture servo circuit (128), and the aperture servo circuit (128) outputs the motor (130). The motor (130) is driven to a position where the output voltage of the directly connected potentio (129) becomes equal to the aperture open voltage of the output signal (127). Of course, the motor (130) also works in conjunction with the diaphragm (131) to open the diaphragm and brighten the fining screen.

(132) is a motor drive amplifier, and (13)
3) is a buffer amplifier of potentio voltage. A voltage is applied to the optimum aperture value calculation circuit (126) from a potentio (134) used to detect the position of the zooming lens through a buffer amplifier (135). This is used to detect changes in image plane illuminance due to zooming magnification.

The motor (136) for driving the variable power lens inside the zoom lens (11) can be manually applied with positive and negative voltages to change from the tele side to the wide side. (137) is a switch that can be momentarily turned on in tele or wide, and (138) is a motor drive amplifier. When executing the pre-scan, the selector (139) selects the A input, that is, the data from the pre-scan-like aperture data generation circuit (140), and the optimum aperture value calculation circuit (126) outputs the data and the zooming magnification detection signal (141). ) And the sensor (15) calculates an aperture value that never saturates, and an output signal (12
7) is output to the aperture servo circuit (128). When executing the image scanning, the selector (139) selects the maximum value storage circuit (48) so that the B input, that is, the maximum level value obtained in the preliminary scanning is output. The optimum aperture value calculation circuit (126) calculates and outputs the aperture value with the aperture as wide as possible from the maximum level value and the zooming magnification detection signal (141) within a range where the sensor (15) is not saturated. Of course, the diaphragm (131) is fixed during scanning.

FIG. 6 is a diagram for explaining the signal processing for the negative film of the image scanning apparatus according to the embodiment of the present invention. In the lower part of FIG. 6, the horizontal axis represents the output level of the sensor (15), and the upper part (a) thereof is the A / D converter (46).
The input range of is shown. In this way, the input range of the A / D converter (46) does not necessarily have to match the saturation level rather than the level of the sensor. (B) shows the output binary code of the A / D converter (46) converted into a decimal number. All 255 are output for the input voltage exceeding the input range of the A / D converter (46).
(C) shows the one's complement of the A / D converter output binary code. In (d), the sensor (1
An example of the output level range of 5) is shown. In the image input scanning, the diaphragm is set to a level that does not saturate the sensor (15) as described above, and it is intended to correspond this to the maximum input level of the A / D converter (46). However, in actuality, there is a slight error in the control of the diaphragm, and the input level of the A / D converter may exceed the maximum input level that can be coded as shown in (d). However, in the negative, this portion is on the transmission side and corresponds to nothing in the positive image, so it may be slightly crushed.

The result of normalizing this as described above and setting it in the range of 0 to 192 is shown in (e).
The graph above (e) shows the input of the ROM (122) on the horizontal axis and the output on the vertical axis. Numbers γ1 to γ5 with respect to the curves in the figure show selectable gamma curves.
Similar to the number of printing papers, No. 1 expresses the soft side and No. 5 expresses the hard side.

Therefore, when operating the apparatus of the embodiment, the gamma curve can be freely selected as if the number of the printing paper is selected. FIG. 7 shows another embodiment relating to gamma correction of the present invention, and FIG. 8 is a characteristic diagram thereof. In this case, as shown in the characteristic diagram of FIG. 8, the λ point near the center of the density distribution is fixed and the five gamma characteristics γ _{1 to} γ _{6 on the} black side and the five gamma characteristics γ ′ _{1 to} γ ′ on the white side. ₆ can be selected independently.

In the embodiment shown in FIG. 7, the white side gamma curve and the black side gamma curve are independently selected using two thumbwheel digital switches (143) and (144), respectively, and their output codes are standardized. The generated image data SD is used as the address of the ROM (145) to obtain the output having the characteristics shown in FIG. Next, the structure of the apparatus for the reflection original will be described with reference to FIG. Instead of a film holder, a mirror (15
0), a diffusing lens (151), an original placing table (152) for placing a reflective original such as photographic paper, an imaging lens (153) and a mirror (154).

In this case, however, it should be noted that one direction of the image is reversed and an electric circuit for correcting this is required. This can be easily dealt with by making a change such that the sub operation direction can be reversed. FIG. 10 shows another embodiment of the gamma correction circuit according to the present invention.

In this embodiment, the A / D converted data is once stored in the random access memory (RAM) (16).
1) It is stored and then read at a predetermined low speed timing. Another random access memory (163) is used for gamma correction. When the RAM (163) is used as an LUT, the selector (162) is selected as the A input side, and when the LUT is created, the B input side is selected. To do.

(165) is a circuit for measuring the density of the film (printing paper) in the prediction operation. This circuit (165) is reset at the same time as the start of the preparatory operation, and when the preparatory operation is completed, a hold signal is given from the outside to hold the measurement result. The output of the circuit (165) is given to the γ correction table creation circuit (164) and an optimum gamma correction curve is created in consideration of the external instruction switches (166) and (123) before the image input scanning. . When this result is written to RAM (163), the device is ready for image input scanning.

When inputting a color image, at least three image input scans are required. Also, four scans of yellow, magenta, cyan and black are usually required to make a printing plate for printing. To do this, the filter (7) of FIG. 1 may be replaced with three or four filters before each prescan. In this way, color separation is possible by changing the spectral distribution of the illumination light. A change in illumination light for each filter can be corrected in the same manner as described above by performing preliminary scanning. However, it should be noted here that it is necessary to put a reference white color in a part of the subject at the same time. In the preliminary scanning, this white level is detected, and correction is performed for each color for image input scanning so as to make it constant.

When the subject is photographic paper, a color magnification chart including white is attached to a part of it. When considering printing, the photo interrupter (21) for start position detection is effective. As described above, the photo interrupter (21) is capable of precise position detection, and the marker signal electronically generated according to this operation is positioned at the same position in the sub-scanning direction and at the end in the main scanning direction. It suffices to mix the image signals as described above.

Of course, it is also easy to generate the markers when they are separated in the sub-scanning direction. In this way, it is possible to easily align the positions of a plurality of printing plates. In the above embodiment, the preliminary scanning is performed at a high speed in the direction opposite to the image input scanning, but it is not limited to this. Further, in the above-described embodiment, the sub-scanning moves the linear image sensor, but the present invention is not limited to this, and the linear image sensor and the image formed by the imaging optical system may be moved relative to each other.

As described above, according to the present invention, only the digital signal of the scanned object is output excluding unnecessary information such as a holder for holding the scanned object. Therefore, if the standardization coefficient for standardizing the image signal is obtained only from this signal, it is possible to obtain image information with high image quality.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part of an optical system and a mechanical system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a photo interrupter for detecting a start position.

FIG. 3 is an operation flowchart of an embodiment of the present invention.

FIG. 4 is a block diagram of a signal system according to an embodiment of the present invention.

FIG. 5 is a block diagram showing an embodiment of a minimum sensor output level detection circuit.

FIG. 6 is an explanatory diagram of signal processing for a negative film.

FIG. 7 is a block diagram showing an embodiment of a gamma correction circuit.

8 is a characteristic diagram showing the output of the gamma correction circuit according to FIG. 7.

FIG. 9 is a diagram showing a configuration of a main part of an optical system and a mechanical system of another embodiment.

FIG. 10 is a block diagram showing another embodiment of the gamma correction circuit.

[Explanation of symbols for main parts]

 1 film 2 XY stage 3 film holder 6 illumination lens 7 filter 8 heat ray transmitting dichroic mirror 9 lamp 10 reflection mirror 11 zoom lens 12 zooming motor with potentio 13 aperture motor with potentio 15 linear image sensor 19, 20 limit switch 21 start position detection Photo interrupter 26 Photo interrupter 152 Original platen

Claims (3)

[Claims] 1. An image sensor, which is provided in the vicinity of the image plane of an imaging optical system, outputs image information by scanning a scanned object having multiple gradations, and outputs image information from the image sensor. A / to convert to n-bit (n ≧ 2 natural number) digital signal according to the key
A D converter, a sorting means for sorting the holder part holding the scanned object or the scanned object based on a digital signal from the A / D converter, and the A / D converter Processing means for outputting only the digital signal of the scanned object, excluding the digital signal of the holder part of the scanned object, which is sorted by the sorting means, in order to obtain the normalization coefficient of the digital signal from An image scanning device characterized by. 2. The sorting means is the holder portion or the scanned object based on the difference between the digital signal of the maximum density portion of the scanned object and the digital signal of the holder portion. The image scanning device according to claim 1, wherein the image scanning device separates the two. 3. The classification means separates a bright portion and a dark portion of the object to be scanned, and the processing means excludes a digital signal of the bright portion detected by the sorting means, and a digital signal of the dark portion. The image scanning device according to claim 1, wherein only the image scanning device outputs the image.