JP2000216997A - Image-reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably set a proper reading condition and image processing conditions even when the image processing condition, etc., of every frame is set based on the pre-scan data on plural frames by absorbing suitably the difference of pre-scan data, that is caused b the difference of reading conditions. SOLUTION: An input device reads odd and even pixel lines of the vertical scanning direction in different accumulation times, and a microprocessor 72 instructs a timing generator 96 according to the read odd and even pixel lines to read an image via a line CCD sensor of an image sensor 68 in the accumulation times corresponding to the odd and even pixel lines respectively. In other words, two types of images of different accumulation times are read in a pre- scan mode. With regard to the output signals of the sensor 68, the field through data are subtracted from the image data by a correlative double sampling circuit 102 via an amplifier 98 and an A/D converter 100. Then the image data are turned into the image data, corresponding to the accumulated charge value of every CCD cell of the sensor 68 and then outputted to an image processing part 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of image reading which is used for a digital photo printer or the like which photoelectrically reads an image photographed on a film and obtains a print (photograph) in which the image is reproduced. Belong.

[0002]

2. Description of the Related Art At present, an image photographed on a photographic film (hereinafter referred to as a film) such as a negative film or a reversal film is printed on a photosensitive material (photographic paper) by projecting an image of the film onto the photosensitive material. Surface-exposing the photosensitive material,
So-called direct exposure (analog exposure) is the mainstream.

On the other hand, in recent years, a printing apparatus using digital exposure, that is, an image recorded on a film is photoelectrically read, and the read image is converted into digital image data (image signal). The image processing is performed to obtain image data (output image signal) for recording, and the photosensitive material is scanned and exposed by a recording light modulated according to the image data (output image signal) to record an image (latent image). Digital photo printers for printing (finish) printing have been put to practical use.

In a digital photo printer, an image can be converted into digital image data, and the exposure conditions at the time of printing can be determined by image data processing. (Sharpening) processing, color or density feria correction, etc., can be suitably performed to obtain high-quality prints that could not be obtained by conventional direct exposure. Further, synthesis of a plurality of images, image division, and synthesis of characters can also be performed by image data processing, and a print that has been freely edited / processed according to the intended use can be output. Moreover, according to the digital photo printer, images are printed (photos)
The image data can be supplied to a computer or the like, or can be stored in a recording medium such as a floppy disk, so that the image data can be used for various purposes other than a photograph.

Such a digital photo printer basically includes an image input device having a scanner (image reading device) and an image processing device, and an image output device having a printer (image recording device) and a processor (developing device). Is configured. In a scanner, reading light emitted from a light source is incident on a film to obtain projection light carrying an image photographed on the film, and this projection light is imaged on an image sensor such as a CCD sensor by an imaging lens. After photoelectric conversion, the image is read, subjected to various image processing as needed, and then sent to an image processing device as film image data (image data signal). The image processing apparatus sets image processing conditions from image data read by a scanner, performs image processing according to the set conditions on the image data, and exposes output image data (output image signal) for image recording. Send to printer as condition. In a printer, for example, if the apparatus uses light beam scanning exposure, the light beam is modulated according to the image data sent from the image processing apparatus, and the light beam is deflected in the main scanning direction and the main scanning direction. The photosensitive material is conveyed in a sub-scanning direction perpendicular to the direction of exposure, and the photosensitive material is exposed (printed) by a light beam carrying an image to form a latent image. Then, an image photographed on the film is reproduced (printed) as a reproduced image.

In an image reading apparatus such as a scanner used for such a digital photo printer, which is required to output a high-quality image, it is necessary to read a density range of a document image with a density resolution as high as possible. Preferably, for that purpose a CCD arranged in the scanner
It is necessary to read an image by making the most of the dynamic range of an image sensor such as a sensor. For this reason, many apparatuses perform pre-reading (pre-scanning) for coarsely reading an image prior to main reading (main scanning) for obtaining image data for print output, and perform image reading based on the image data obtained by the pre-scanning. Based on the knowledge of the density range and the like, the reading conditions of the main scan are determined accordingly, and the processing conditions (image processing conditions) of the image data obtained by the main scan are determined.

Therefore, the pre-scan is performed under the condition that all the densities that can be recorded on the original can be read. In other words, when the negative film is a document, the pre-scan accurately and appropriately covers a wide range of densities exceeding 3 from under (underexposure) to over (overexposure) documents. It must be readable. However, there are few image sensors with a wide dynamic range that can read such a wide density range with high accuracy.

For this reason, in an apparatus which needs to read an image in a density range exceeding the dynamic range of an image sensor capable of reading a high-precision and proper image, it is necessary to change the accumulation time (exposure time) of the CCD sensor and to read with a different light amount. Under the conditions, a plurality of types of readings suitably corresponding to images having different density ranges are performed by pre-scanning, and according to the result, for example, pre-scanning data under reading conditions under which proper reading was performed is adopted, and It is conceivable to determine scan reading conditions and image processing conditions.

[0009]

By the way, in order to reproduce a higher quality image from an image photographed on a film, it is necessary to read the main scan in consideration of film characteristics (for example, base density of the film). It is preferable to determine conditions and image processing conditions. It is difficult to obtain proper film characteristics from one frame of image data, and it is preferable to determine the film characteristics by using the image data of a plurality of frames, preferably, the entire frame of one film. That is, it is necessary to use image data of a plurality of frames in order to set more preferable main scanning reading conditions and image processing conditions in consideration of film characteristics.

However, when image processing conditions and the like are set using pre-scan data of a plurality of frames, if pre-scan data having different reading conditions coexist, the pre-scan data cannot be treated as the same data. Reading conditions and image processing conditions cannot be set. Further, even if the difference between the pre-scan data is simply canceled from the reading condition, an appropriate image processing condition or the like cannot often be set due to the characteristics of an image sensor such as a CCD sensor.

A first object of the present invention is to solve the above-mentioned problems of the prior art and to read an original such as a CCD sensor which photoelectrically reads an original image having a wide density range such as a negative film or a reversal film. In order to broaden the image reading dynamic range of the means (device), when photoelectrically reading a document image under a plurality of reading conditions different in light quantity, a plurality of types of image signals read under a plurality of different reading conditions are used. When a correction is made based on the difference between the set reading light amounts, a difference between image signals (image density data) due to a difference in reading conditions is appropriately absorbed without causing an error caused by the characteristics of the document reading unit, and each reading is performed. It is an object of the present invention to provide an image reading method that can match the signal levels of image signals under conditions.

A second object of the present invention is to solve the above-mentioned problems of the prior art. In order to cope with a wide range of densities, a pre-scan is performed under a plurality of kinds of reading conditions different in light quantity. In the image reading for determining the scanning conditions and the image processing conditions for the main scan using the data, differences in image data caused by the differences in the scanning conditions for the pre-scan are appropriately absorbed, and each of the pre-scan data of a plurality of frames is used. An object of the present invention is to provide an image reading method capable of stably setting appropriate conditions even when setting image processing conditions and the like of frames.

[0013]

SUMMARY OF THE INVENTION In order to solve the first problem, the present invention provides a method of photoelectrically reading a document image under a plurality of kinds of reading conditions different in terms of light amount, and reading an image read under each reading condition. A signal characteristic value of the document image is obtained for each of the reading conditions from a signal, and a difference in signal level of the image signal under each reading condition is absorbed using the image characteristic value obtained under the reading condition. Further, the present invention provides an image reading method wherein the signal levels of the image signals under the respective reading conditions are matched.

Here, the image characteristic value is at least one of an average value over a predetermined range of the cumulative histogram of the image signal, a predetermined point of the cumulative histogram of the image signal, and an average value of the image signal. preferable. Further, it is preferable that the difference between the signal levels of the image signal is a light amount difference between the reading conditions. In addition, it is preferable that at least one of the number of times of reading a plurality of times and the color of a plurality of times of reading be switched according to the type of the original image as the reading condition.

Preferably, the document reading means for photoelectrically reading the document image under the plurality of kinds of reading conditions differing in light amount is a line sensor, and reads at predetermined exposure times between predetermined lines. . In addition, it is preferable that the difference between the signal levels of the image signal is a positional shift difference between the lines by the line sensor. Further, in the image reading method, for one of the plurality of corrected image signals obtained by matching the signal levels of the image signals under the respective reading conditions, one optimal corrected image signal is output, or It is preferable that at least two types of corrected image signals are combined and output from the corrected image signals.

In order to solve the second problem,
Reading the document image photoelectrically under the plurality of types of reading conditions different in light amount and matching the signal levels of the image signals under the respective reading conditions means that the document image is photoelectrically read in order to obtain an output image signal. It is preferable to perform the pre-reading that is performed prior to the main reading to be performed. Also,
In the image reading method, further using the pre-reading correction image signal obtained by matching the signal level of the image signal under the respective reading conditions in the pre-reading, using the pre-reading reading conditions and the main reading, It is preferable to determine at least one of the image processing conditions of the image processing applied to the main reading image signal. In addition, as the pre-reading corrected image signal, a plurality of corrected image signals obtained by matching the signal levels of the image signals under the respective reading conditions are one optimal corrected image signal or one of the plurality of corrected image signals. It is preferable to select a synthesized image signal obtained by synthesizing at least two types of corrected image signals.
In each of the above aspects, the image signal may be a digital density signal.

In order to solve the second problem, the present invention relates to an image reading method for photoelectrically reading an original image, wherein a plurality of pre-reads having different light amounts are performed prior to a main read for obtaining an output image signal. Performed under various reading conditions, using the image characteristic values of the image obtained by the pre-reading, absorbing the difference between the pre-read image signals caused by the difference in the reading conditions, and absorbing the difference between the image signals. It is an object of the present invention to provide an image reading method characterized in that at least one of a reading condition of the book reading and an image processing condition for performing image processing on an image signal obtained by the book reading is determined using a corrected image signal. is there.

Further, the image characteristic value is at least one of an average value between a predetermined percentage point and a predetermined percentage point of the histogram based on the image signal, a predetermined percentage point of the histogram based on the image signal, and an average value of the image signal. It is preferably one. Further, it is preferable that at least one of the reading condition and the image processing condition is set using the pre-read image data of a plurality of frames. By absorbing the difference between the reading conditions, even if an image read under the optimum reading condition is selected according to the image density of each frame, image data of a plurality of frames can be handled in the same manner.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image reading method according to the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 shows a block diagram of a photographic printing and developing machine for carrying out the image reading method of the present invention. A photographic printing / developing machine 10 shown in FIG. 1 is the above-described digital photo printer, and a scanner 12 for photoelectrically reading an image photographed on a film F and a predetermined image data (image signal) read by the scanner 12. An input device 16 having an image processing device 14 that performs image processing to produce image data (output image signal) for print output, and a light beam modulated according to the image data (output image signal) output by the image processing device 14 An output device 22 having a printer 18 for scanning and exposing a photosensitive material (photographic paper) to record a latent image, and a processor 20 for subjecting the exposed photosensitive material to wet development processing and drying processing and outputting as a (finished) print And
Here, the input device 16 implements the image reading method of the present invention (hereinafter, referred to as a reading method).

The image processing device 14 is read by the scanner 12 with a keyboard 24 a and a mouse 24 b for inputting and setting various conditions, selecting and instructing processing, and instructing color / density correction. A display 26 that displays the input image, various operation instructions, various condition setting / registration screens, and the like is connected.

FIGS. 2A and 2B show the state of the scanner 12.
FIG. 2A shows a front view of the scanner 12, and FIG. 2B shows a right side view thereof.

The scanner 12 includes a light source unit 28 and a reading unit 3
0. The light source unit 28 is housed in a casing 34 below the work table 32 of the scanner 12 (input device 16), and a reading light source 36 is disposed on the right side inside the casing 34. As the light source 36, various light sources used for ordinary photoelectric image reading, such as a halogen lamp and a metal halide lamp, can be used. Around the light source 36, a reflector 38 for efficiently entering the light emitted from the light source 36 into the film F is disposed. In addition, a cooling fan 40 for cooling the inside of the casing 34 and maintaining the casing at a predetermined temperature is disposed.

Further, a light source 36 is provided in the casing 34.
UV / IR cut filter 42, first CC filter 44, and second CC filter that cuts light of ultraviolet and infrared wavelengths toward the downstream side (hereinafter referred to as the downstream side) in the traveling direction of light emitted from 46, a variable aperture 48, and a light diffusion box 50 are arranged. 1st CC filter 4
The fourth and second CC filters 46 adjust the color components (light intensity in each wavelength range) of the read light emitted from the light source 36 using, for example, a color filter, in order to perform appropriate image reading. It is for correcting individual differences of the 36 color characteristics.

The variable aperture 48 adjusts the amount of reading light incident on the film F.
It is a known variable stop such as an iris stop or an ND filter whose transmission density changes continuously. Alternatively, a plurality of ND filters having different transmission densities may be used as the variable stop 48, or a combination of these may be used. These ND filters may be combined with the above-described contact / separation stop plate, iris stop, and the like. May be used. The variable aperture 48 is used to obtain image data for print output, on the other hand, at the time of pre-reading (hereinafter, referred to as pre-scan) described below, to an aperture value set under predetermined pre-scan reading conditions. At the time of main reading (hereinafter referred to as main scanning), the aperture value set from the image data obtained by the pre-scan is set to
Each is adjusted.

The light diffusion box 50 is a substantially L-shaped cylindrical body, and both open ends (the entrance and exit of the reading light) are closed by light diffusion plates 50a and 50b, respectively. And a mirror that deflects the light by 90 ° and reflects the light. The exit of the light diffusion box 50 has a slit shape extending in the same direction as an extension direction (hereinafter, referred to as a main scanning direction) of a line CCD sensor of an image sensor 68 described later. The incident light is diffused by the light diffusion plates 50a and 50b, and is emitted as slit light extending in the main scanning direction.

As described above, the light source unit 28 is located below the work table 32. On the upper surface of the work table 32,
The keyboard 24a, the mouse 24b, and the display 26 described above are placed thereon. In the scanner 12, a new photo system (Advanced Photo System)
In accordance with the type and size of a negative film or reversal film of 5 sizes or the like, the form of the film such as strips or slides, etc., a dedicated carrier 54 that can be mounted at a predetermined position on the work table 32 is prepared. Can be used for various films.

The illustrated scanner 12 reads an image by slit scanning exposure. The long film F is positioned at a predetermined reading position corresponding to the emission port of the light diffusion box 50 by the carrier 54, and the main scanning is performed by the pair of transport rollers 54a and 54b disposed across the reading position. The direction of the arrow b in the figure perpendicular to the direction
It is scanned and transported in the sub-scanning direction, and is irradiated with slit-like reading light from below. In this manner, in the scanner 12, the film F is two-dimensionally slit-scanned with the reading light to obtain projection light carrying an image, and the image of each frame captured on the film F is sequentially read. Also, the carrier 54
The mask also serves as a mask for restricting reading light incident on the film F and / or projection light transmitted through the film F into a predetermined slit shape.

The carrier 54 is provided with a photographing area for determining a print format and a sensor for reading a DX code, and necessary information is sent to the image processing apparatus 14.
Further, as is well known, a transparent magnetic recording medium is formed on the film F of the new photographic system, and the film type, cartridge ID, photographing date and time, whether or not strobe light is emitted at the time of photographing, and the like are recorded therein. However, on the carrier 54 corresponding to the new photo system, a magnetic head for reading information recorded on the magnetic recording medium and recording information is arranged.
The read information is sent to the image processing device 14.

Above the work table 32, a reading unit 30
Are housed in the casing 56 and arranged. An optical frame 58 is provided upright on the upper surface of the work table 32, and the casing 56 is movable in a direction in which the casing 56 comes into contact with or separates from the work table 32 (that is, the direction of the focus advance of the lens unit 64, which is referred to as a vertical direction). It is supported by the optical frame 58. A mounting table 60 is provided in the casing 56, and a plurality of support rails 62 hang down from the mounting table 60. A lens unit 64 is supported by the support rail 62 so as to be vertically movable.

The lens unit 64 is an imaging lens unit composed of a plurality of lenses, and forms an image of the projection light of the film F on the light receiving surface of the image sensor 68. Lens unit 6
A lens stop 66 is arranged between the four lenses.
The lens stop 66 is, for example, an iris stop, and adjusts the amount of projection light that passes through the lens unit 64 and forms an image on the image sensor 68.

An image sensor 68 is provided on the upper surface of the mounting table 60.
Is installed. The image sensor 68 includes a line CCD sensor extending in the main scanning direction and having any one of R, G, and B color filters attached to the light incident side. Are placed,
This is a so-called three-line color CCD sensor. The electric charges accumulated in each CCD cell (pixel) of each line CCD sensor of the R line sensor, the G line sensor, and the B line sensor are sequentially transferred from the corresponding transfer unit. The image sensor 68 is located upstream (below) of the image sensor 68.
A shutter 70 for taking data for dark correction is arranged.

The scanner 12 shown in the figure uses a line CCD sensor as an image sensor to photoelectrically read a film image by slit scanning exposure.
The present invention is not limited to this, and reading may be performed by surface exposure using an area CCD sensor. In this case,
For example, a turret having R, G, and B color filters is arranged between a light source and a scanner, one frame of the film is held at a predetermined reading position, and each color filter is sequentially inserted into an optical path to perform reading. Thus, the image photographed on the film is separated into the three primary colors of R, G and B and read.

FIG. 3 is a schematic configuration diagram of an electric system of the scanner 12. The scanner 12 has a microprocessor 72 that controls the entire scanner 12. The microprocessor 72 has a RAM 76 via a bus 74,
A ROM 78 (for example, a rewritable ROM) is connected, and the lamp driver 80 and the motor driver 8 are connected.
2 are connected.

The lamp driver 80 turns on and off the light source 32 in response to an instruction from the microprocessor 72. On the other hand, the motor driver 82 has
Aperture drive motor 86M for adjusting the aperture value by sliding A and 48B; aperture position sensor 8 for detecting the positions (aperture amounts) of plates 48A and 48B of variable aperture 48
6S; a reading unit drive motor 88M for vertically moving the casing 56 accommodating the reading unit 30; a reading unit position sensor 88 for detecting the position of the casing 56 (that is, the reading unit 30).
S: a lens drive motor 90M for vertically moving the lens unit 64; a lens position sensor 90S for detecting the position of the lens unit 64; a lens aperture drive motor 92M for adjusting the lens aperture 66; and detecting the position (aperture value) of the lens aperture 66 And a shutter drive motor 94M for switching the shutter 70 between a fully closed state and a fully opened state.

When reading the image of the film F by the image sensor 68, the microprocessor 72 adjusts the variable aperture 48 by the aperture drive motor 86M according to the position of the variable aperture 48 and the set reading conditions. The light amount of the reading light incident on the film F is adjusted (the density of the original image is adjusted). Further, the microprocessor 72 determines the zoom magnification in accordance with the size of the film F and an instruction to change the magnification, and adjusts the position of the reading unit so that the projection light of the film F forms an image on the image sensor 68 in accordance with the zoom magnification. Sensor 8
The reading unit drive motor 88M moves the casing 56 up and down based on the position detection of the casing 56 by 8S, and moves the lens unit 64 up and down with the lens drive motor 90M based on the position detection of the lens unit 64 by the lens position sensor 90S. Further, the lens stop driving motor 92M is driven according to the magnification and the like to adjust the lens stop 66.

Further, the image sensor 68 generates various timing signals (clock signals) for operating the image sensor 68, the A / D converter 100, and the like.
The timing generator 96 is connected. The microprocessor 72 issues an instruction to the timing generator 96 according to the set reading condition, and
The image is read by each line CCD sensor of the image sensor 68 during the exposure time for accumulating electric charge in each CCD cell of the sensor, that is, a predetermined accumulation time (electronic shutter speed).

Here, in the scanner 12, a main scan for reading an image finely and densely (high resolution) in order to obtain image data for print output to be supplied to the printer 18, and reading conditions and image processing conditions for the main scan are described. In order to determine the image, two times of image reading are performed for one frame (one image) of a pre-scan, which is performed prior to the main scan and reads the image coarsely (low resolution). The pre-scan is normally performed under reading conditions under which all the documents that can be read by the scanner 12 can be read, that is, under such a reading condition that the output is not saturated even with the lightest density (lowest density) film. From the image data obtained by the prescan (hereinafter referred to as prescan data), the image density range of the image sensor 68 such that the output of the image sensor 68 is saturated at a density slightly lower than the minimum density of the frame. The reading conditions of the main scan that can be read by making the most of the dynamic range are set, and the main scan is performed according to the conditions.

Input device 16 for implementing the reading method of the present invention
In the scanner 12, the prescan is performed under a plurality of types of reading conditions that differ in light amount. As a result, the dynamic range of the image sensor 68 is widened (apparently), and in pre-scanning, from under exposure to over exposure, a film image in a wide density range exceeding 3 in density is stably, accurately and appropriately. It becomes possible to read. Further, as will be described in detail later, in the present invention, the difference in signal level of the prescan data (image signal) is absorbed by using image characteristic values based on a plurality of prescan data having different read conditions, and each of the read conditions , The signal level of the pre-scan data is matched, and the reading conditions and image processing conditions for the main scan are set from the corrected pre-scan data (corrected pre-scan image signal) corrected so that the signal levels match. Thus, even when the image processing conditions and the like of the main scan data are determined using the image data of a plurality of frames, the signal level difference of the pre-scan data for each frame caused by the reading conditions is absorbed to reduce the signal level. It is possible to set the image processing conditions so as to set suitable image processing conditions and the like. Here, pre-scan data (image data) for performing an operation of absorbing the difference in signal level and making the signal level coincide with each other is output from the image sensor 68, A / D-converted, and Log-converted digital density signal (density). Data).

In the illustrated input device 16 (scanner 12), an odd pixel line (odd line) in the sub-scanning direction is used.
And the even pixel line (even line) are read at different accumulation times, and the microprocessor 72 issues an instruction to the timing generator 96 accordingly, and the odd pixel line and the even pixel line correspond to the respective accumulation times. The image is read by the line CCD sensor of the image sensor 68 at a certain time. That is, in the illustrated example, two types of image reading with different light amount conditions (accumulation time) are performed in the pre-scan. For example, in an odd pixel line, even when the image density is extremely low (for example, under exposure in a negative film), the image sensor 68
The reading is performed with an accumulation time that does not saturate the output of the even-numbered pixel line.
Reading is performed with the accumulation time determined so that the maximum density can be detected with high accuracy.

In the present invention, the plurality of types of image reading with different light amounts in the pre-scan are not limited to the above-described example, and may correspond to high and low density images with odd and even pixel lines. Reading may be performed under different conditions for each of a plurality of pixels, such as every two pixels. Also, the reading conditions are not limited to two types. For example, three different types of reading conditions corresponding to a high-density image, a standard-density image, and a low-density image, respectively, may be used for each pixel or a plurality of pixels. Reading may be performed sequentially, or reading may be performed under four or more different reading conditions. In addition, reading may be performed by changing the reading conditions for odd-numbered pixels and even-numbered pixels in the main scanning direction instead of the sub-scanning direction, or for each of a plurality of pixels. In addition, in the case of a scanner that reads an image by surface exposure using the above-described area CCD sensor, the reading light in the pre-scan is adjusted not by the accumulation time of the area CCD sensor but by adjustment of a variable aperture arranged in a light source unit or a lens unit. By changing the light amount, a plurality of types of image reading with different light amount conditions may be performed in the pre-scan.

The storage time of each line CCD sensor may be independently set and controlled according to the type of the original image (original image), the color balance, the density, and the like. Here, in the pre-scan by the image sensor 68, any type of reading conditions having different light amounts may be used, and the number of times of image reading under reading conditions having different light amounts may be determined.
That is, the number of times of reading a plurality of times may be any number of times, and the number of colors to be read a plurality of times under reading conditions different in light amount, Good. For example, any of R, G, and B may be used, or any of 2
It may be a color or all three colors. Of course, four or more colors may be targeted. The type of these reading conditions, the number of times of image reading, and the color to be read a plurality of times may be set and switched according to the type of the document image, its color balance, density, and the like. For example, in the pre-scan by the image sensor 68, as a reading condition that differs in light amount, according to the document type, the color balance or the density of the original image, etc. The number of times may be switched, for example, from two to three, or the color to be read may be changed, for example, B to G or B only to B and G without changing the number of image readings. Good, and both at the same time, for example, twice with B, G
May be switched to three times, or two times at B, to three times at B and twice at G.

The signal output from the image sensor 68 is amplified by the amplifier 98 and converted into digital image data by the A / D converter 100. The digital image data converted by the A / D converter 100 is processed by a correlated double sampling circuit (CDS) 102, and is processed by an interface (I / D).
F) The signals are sequentially output to the image processing unit 14 via the circuit 1040. Note that the CDS 102 subtracts the feed-through data representing the level of the feed-through signal from the image data, thereby converting the image data to the image sensor 68.
Is image data that accurately corresponds to the amount of charge stored in each CCD cell.

Since the R, G and B photometric signals are output in parallel from the image sensor 68, the amplifier 9
8. The signal processing systems of the A / D converter 100 and the CDS 102 also have three systems, and the I / F circuit 104 outputs R, G, and B image data in parallel.

FIG. 4 shows a block diagram of the image processing apparatus 14. The image processing device 14 includes a scanner correction unit 106, an image processing unit 108, a condition setting unit 110, a personal computer 112, and an input / output controller 114.

The scanner correction unit 106 includes the scanner 12
There are provided three signal processing systems including a dark correction circuit 116, a defective pixel correction unit 118, and a light correction circuit 120, corresponding to the R, G, and B image data output in parallel from.

The dark correction circuit 116 includes an image sensor 68
Dark (dark current) correction, for example, the shutter 7
Image data (data representing the dark output level of each CCD cell (pixel) of the image sensor 68) output from the scanner 12 when 0 is closed is measured and stored for each pixel. The data of the dark output level is subtracted from the image data of the film F output from the camera to perform dark correction. The defective pixel correction unit 118 stores, for example, the address of an output abnormal pixel (defective pixel) obtained from the reference document, and when reading the film F, replaces the image data of the defective pixel with the image of the surrounding pixels. Generated by interpolation with data. The brightness correction circuit 120 corrects the variation of each pixel of the image sensor 68, and uses a gain that corrects the output variation of each pixel obtained from the reference original,
The image data of the film F output from the scanner 12 is corrected.

In the image sensor 68, R, G,
Since the three B line CCD sensors are arranged at intervals in the sub-scanning direction, there is a time difference between the timings at which the scanner 12 starts outputting the R, G, and B image data. The scanner correction unit 106 delays the image data output timing with a different delay time for each component color so that the R, G, and B image data of the same pixel line on the image is output at the same timing.

The image data output from the scanner correction unit 106 is input to the selector 122. The input terminal of the selector 122 is also connected to the data output terminal of the input / output controller 114.
, The image data input from the outside is
2 is input. The output terminal of the selector 122 is connected to the input / output controller 114 and the image processing unit 108. The selector 122 selectively outputs the supplied image data to the input / output controller 114 and the image processing unit 108.

The image processing unit 108 includes a memory controller 124, a processing unit 126, and three frame memories 128.
A, 128B and 128C. Each of the frame memories 128A, 128B, and 128C has a capacity capable of storing one frame of main scan image data, and the image data input from the selector 122 is processed by the processing unit 12B.
6, and sent to the input / output controller 114.
Alternatively, it is stored in any of the three frame memories 128 as needed. The memory controller 124 controls an address when the image data is stored in the frame memory 128 such that the pixels of the input image data are stored in a storage area of the frame memory 128 in a predetermined order.

The processing section 126 performs predetermined image processing such as color balance adjustment, gradation adjustment, density adjustment, and the like on image data obtained by the main scan (hereinafter referred to as main scan data).
A dodging process (compression / expansion of density dynamic range), a saturation adjustment, an electronic scaling process, a sharpness (sharpening) process, and the like are performed to obtain image data for print output. Note that these processes are performed by a well-known method that appropriately combines arithmetic processing, processing using an LUT (look-up table), matrix (MTX) arithmetic, processing using a filter, and the like. , L
UT and MTX calculation etc.)
Along with the reading conditions, they are set by a condition setting unit 110 described later. The processing unit 126 is connected to the input / output controller 114, and the image data subjected to the image processing is
At a predetermined timing (after being temporarily stored in the frame memory 128 if necessary), the input / output controller 114
Output to

As described above, in the photographic printing / developing machine 10 that carries out the reading method of the present invention, there are two methods, a pre-scan for coarsely reading the image of each frame photographed on the film F and a main scan for reading at high resolution. The image reading is performed twice. Also,
In the pre-scan, the accumulation time (exposure time), that is, the reading condition of each pixel line is optically different between the odd-numbered pixel line and the even-numbered pixel line. The image data obtained by the prescan is sent from the selector 122 to the input / output controller 1.
14 and output from the input / output controller 114 to the condition setting unit 110.

The condition setting unit 110 includes a CPU 130, RA
M132, a ROM 134 (for example, a ROM whose storage content can be rewritten), an input / output (I / O) port 136,
These are connected to each other via a bus 138, and data of an area corresponding to each frame (image) of the film is extracted using the pre-scan data input from the input / output controller 114, and the position of each frame is extracted. Is detected, and the image processing conditions for each frame and the reading conditions for the main scan are set (calculated).

Specifically, as described above, in the input device 16 (scanner 12) according to the present invention, reading is performed under a plurality of types of optically different reading conditions by pre-scanning. The condition setting unit 110 (CPU 130) first matches the signal level of each pre-scan data using the image characteristic value of the pre-scan image data (pre-scan data) under each reading condition. Prescan data (hereinafter, referred to as corrected prescan data) that absorbs the difference due to the difference is generated. In the illustrated example, since the accumulation time of the image sensor 68 is different between the odd-numbered pixel line and the even-numbered pixel line, the difference in the accumulation time is absorbed by using the image characteristic value of each pre-scan data, and the signal levels of the two coincide. The corrected pre-scan data is generated and output as so-called pre-scan image data for calculating main scan reading conditions and image processing conditions.

As a method of matching the signal levels of image data read under optically different conditions, a method of taking the ratio of different reading conditions (in the illustrated example, the ratio of the storage time) and absorbing the difference can be considered. . However, in many cases, the output of the image sensor does not change linearly with respect to the image density (light reception amount). In the above method, the output is obtained particularly in a high density (low output) region according to the characteristics of the image sensor. Prescan data does not correspond to the actual image density. On the other hand, in the method of the present invention, the difference due to the reading condition is absorbed by using the image characteristic value of the pre-scan data. Therefore, it is possible to appropriately absorb the difference between the reading conditions regardless of the characteristics of the image sensor.

Here, the difference between the signal levels of the pre-scan data under a plurality of different reading conditions due to the difference in the reading conditions is, for example, a line CCD sensor or an area CC.
A difference in the accumulation time of the D sensor and a difference in the exposure time can be cited. In the present invention, the difference in the light amount between the reading conditions, that is, the difference in the amount of light received by the CCD sensor between the reading conditions is defined as the difference. it can. When reading is performed for different scanning lines by the line CCD sensor, for example, at different accumulation times (exposure times) between odd-numbered pixel lines and even-numbered pixel lines, the difference in signal level of each pre-scan data is:
It is also possible to use the positional deviation difference between scanning lines by the line CCD sensor. That is, when the odd-numbered pixel line is used as a reference, the even-numbered pixel line is aligned with the position of the odd-numbered pixel line by interpolation between even-numbered pixel lines, for example, by using preceding and following even-numbered pixel lines. By generating the image data of In this way, an image consisting only of the image data of the odd-numbered pixel lines and an image consisting only of the image data of the even-numbered pixel lines can be aligned with each other, and the position of each line of each image is the same. Image.

The image characteristic values used for calculating the corrected pre-scan data, that is, for absorbing the difference in the reading conditions, are determined from a predetermined% point of the density histogram such as average density and highlight (lowest density), and a predetermined% point of the density histogram. The average value up to the% point, that is, the average value between the predetermined ranges (hereinafter, referred to as the predetermined% point) is exemplified. In particular, the average value between the predetermined% points of the density histogram is preferable, and among them, the average value between the predetermined% points in the low density (high output) area is suitably used. The use of the information on the low-density region is preferable because the influence of the nonlinearity of the input / output characteristics of the high-density region of the image sensor 68 can be reduced. The value between the predetermined% points to be used depends on the characteristics of the image sensor 68 to be used,
It is appropriately set in accordance with the reading conditions and the like. For example, a 10% point to 60% point on the low density side is preferably exemplified.

The method of calculating the corrected prescan data using the image characteristic values is not particularly limited, and various methods according to the image characteristic values to be used can be used. For example, when the average density is used as the image characteristic value, the image data of each pixel of the odd-numbered pixel line is image 1 and the average density is D.
1. Image data of each pixel of the even pixel line is image 2,
When the average density is D2 and image 1 of the image data of each pixel of the odd pixel line is used as a reference, corrected image data (corrected pre-scan data) image 2 ′ of each pixel of the even pixel line is calculated by the following equation. do it. Corrected prescan data (image 2 ') = image 2+
(D1-D2) Here, D1-D2 is a difference in signal level of image data due to a difference in reading conditions to be absorbed.

The corrected pre-scan data (image 2 ′) thus obtained is combined with image 1 of the reference odd-numbered pixel line image data having the same signal level as in the following equation to obtain the corrected pre-scan data. (Image 3). Corrected pre-scan data (image 3) == image 1 (for odd pixel lines) = image 2+ (D1-D2) (for even pixel lines) Corrected pre-scan data (image 3) thus obtained
Can be output as so-called pre-scan image data for calculating main scan reading conditions and image processing conditions.

In both the case where the average value between the predetermined% points of the density histogram is used and the case where the predetermined% point itself of the density histogram is used, it is possible to calculate the corrected prescan data in the same manner as in the above-described method using the average density. Good. For example, when the odd pixel line is used as a reference, the difference between the average value of each of the odd and even pixel lines or the difference between the predetermined% points is determined as the difference between the signal levels of the image data due to the difference in the reading conditions to be absorbed. The correction pre-scan data may be calculated by adding the pixel data to the image data of the pixel line.

In the above example, the two types of image data of the odd and even pixel lines are combined to calculate the corrected prescan data (image 3), which is output as so-called prescan image data. However, the present invention is not limited to this. For example, pre-scan data (image
1) and the corrected pre-scan data (image 2 ′), the most appropriate pre-scan data may be output as so-called pre-scan image data, or a pre-scan image data selecting means may be provided. It is also possible to select whether to output the optimal pre-scan data or to output the synthesized corrected pre-scan data.

When pre-scanning is performed under three or more different reading conditions, three or more types of corrected pre-scan data corrected so that the difference between each signal level is absorbed and each signal level is matched. (Including pre-scan data serving as a reference that is not corrected), the optimum corrected pre-scan data may be output from among these three or more types of corrected pre-scan data, or three or more types of corrected pre-scan data may be output. At least two or more types of corrected prescan data of the prescan data may be combined and output. Further, a pre-scan image data selecting means is provided,
An optimal corrected pre-scan image data is output from among three or more types of corrected pre-scan data, or at least two or more types of corrected pre-scan data among the three or more types of corrected pre-scan data are combined and output. May be selected.

The condition setting unit 110 then creates a density histogram using the corrected pre-scan data, and calculates the average density, LATD (large area transmission density), highlight (lowest density), shadow (highest density), etc. Calculation of an image characteristic value such as a predetermined% point of the density histogram is performed.

Next, the state of the original image is determined from these results and the film information detected from the DX code or the like read by the carrier 54, and the image density is determined for each frame at a density slightly lower than the minimum density of the original image. The accumulation time of each line CCD sensor of the image sensor 68 and the aperture value of the variable aperture 48 are calculated so that the output from the sensor 68 is saturated, and the reading conditions for the main scan (hereinafter referred to as the main reading conditions) are obtained. I do. In addition to the density histogram, image characteristic values, film information, and the like obtained from the corrected pre-scan data, the condition setting unit 110 further responds to an instruction from an operator using the keyboard 24a or the like to set the above-described gray level for each frame. Image processing conditions (hereinafter, processing conditions) such as balance adjustment and density correction are set.

Here, in the input device 16 (scanner 12) of the illustrated example, after performing pre-scanning of all frames, the processing conditions and the processing conditions of each frame are reversed in the reverse order of the pre-scanning.
Set the main reading conditions. Therefore, as a preferable mode, the processing condition can be set in consideration of not only the corrected pre-scan data of the frame but also a plurality of frames, more preferably the corrected pre-scan data of all the frames.
High-quality output image by setting processing conditions by accurately grasping film characteristics such as base density of film F, and setting more appropriate processing conditions according to the original image (including original type) Can be obtained. Further, according to the present invention, in order to cope with a wide range of densities, pre-scan is performed under a plurality of reading conditions. However, since image processing conditions are set using the above-described corrected pre-scan data, a plurality of frames are set. Even if the pre-scan data is used, there is no inconvenience due to the difference in the reading conditions.

As will be described later in detail, the condition setting unit 110 sets image processing conditions and main scan reading conditions when performing image verification, and then sets the set processing conditions and pre-scan image data to the personal computer 112.
Output to This image is a personal computer 112
Is displayed as a simulation image on the display 26 connected to the image processing device, and if necessary, the image, that is, the image processing condition is corrected by the operator, and the image processing condition is determined.

When the processing conditions are determined, the condition setting section 110
Is the processing unit 12 of the image processing unit 108
6 and the detected position of each frame and the reading conditions are output to the microprocessor 72 of the scanner 12. The microprocessor 72 adjusts the storage time of each line CCD sensor and the aperture value of the variable aperture 48 according to the supplied reading conditions for each frame, and performs image reading according to the positional information of each frame sent. Do.

The personal computer (hereinafter, referred to as PC) 112 includes a CPU 140, a memory 142, a hard disk 144, a CD-ROM driver 146, a transport control unit 148, and an expansion slot 150, which are connected via a bus 154. Connected to each other. Further, the bus 154 includes the keyboard 24a and the mouse 24 described above.
b, the display 26 is also connected. Transport control unit 1
Reference numeral 48 is connected to the carrier 54, and controls the transport of the film F by the carrier 54. The storage medium drive, information processing equipment, communication means, etc.
It is connected to PC 112 via 50.

As described above, when performing the test, when the condition setting unit 110 sets the processing conditions, the pre-scan data and the set processing conditions are output to the PC 112.
The PC 112 processes the pre-scan data of each frame under the corresponding processing conditions, and displays it on the display 26 as a simulation image. In the test by the operator,
The image correction instruction is mainly input using a density correction key, a color correction key, and the like set on the keyboard 24a.
At C112, the processing conditions are set and corrected (changed) in accordance with the correction instruction, the simulation image on the display 26 is changed accordingly, and the image correction information is supplied to the condition setting unit 110. The condition setting unit 110 also sets and corrects processing conditions according to the correction instruction.

The input / output controller 114 is connected to the printer 18 via an I / F circuit 156. Normally, image data for print output that has been subjected to image processing by the image processing unit 108 is transmitted from the input / output controller 114 to the
The image data is output to the printer 18 via the / F circuit 156 as output image data. When outputting image data to the outside, the image data processed by the image processing unit 108 is transmitted from the input / output controller 114 to the condition setting unit 1.
10 to the PC 112.

The output device 22 includes a printer 18 and a processor 20. The output device 22 exposes a photosensitive material (photographic paper) in accordance with image data output from the image processing device 14 (input device 16) to form a latent image. It is recorded, subjected to a predetermined development process, and output as a (finished) print. The printer 18
As an example, a latent image is recorded on a cut sheet-shaped photosensitive material by light beam scanning exposure.After cutting the photosensitive material into a predetermined length corresponding to the print to be made, a back print is recorded, and then R exposure, By modulating three types of light beams of G exposure and B exposure according to image data (recorded image) and deflecting them in the main scanning direction, and conveying the photosensitive material in a sub scanning direction orthogonal to the main scanning direction, The photosensitive material is two-dimensionally scanned and exposed by a light beam to record a latent image, and the exposed photosensitive material is sent to the processor 20. In the processor 20, the supplied photosensitive material is subjected to a predetermined wet development process such as color development, bleach-fixing, washing with water to visualize the latent image, and then dried to form a print. Sort and accumulate on a case-by-case basis.

Hereinafter, the operation of the photographic printing / developing machine 10 will be described, and the image reading method of the present invention will be described in more detail.

After the photographic printing / developing machine 10 is started and the carrier 54 corresponding to the film F is mounted at a predetermined position on the operation table 32, the input device 16 (the scanner 12, the image processing device 14) such as the light amount of the light source 36, etc. Is in a predetermined state, and the film F used for print production is
Is mounted on a predetermined position of the carrier 54. Here, as an example, print production of the film F of 24 frames is performed.

The input device 16 (the scanner 12 and the image processing device 14) rises, and the carrier 54
Is confirmed, the scanner 12 enters a pre-scan enabled state (pre-scan mode), and the microprocessor 72 controls the aperture value of the variable aperture 48 and each line C of the image sensor 68 according to the pre-scan reading conditions.
The accumulation time of the CD sensor and the like are set. Here, the accumulation time of each line CCD sensor is different between the odd-numbered pixel line and the even-numbered pixel line in the sub-scanning direction.
Reading is performed under a plurality of kinds of optically different reading conditions. At the same time, the magnification is adjusted by moving the casing 44 and the lens unit 64 up and down according to the type and print size of the film F.

When the scanner 12 enters the state corresponding to the pre-scan, the carrier 54 starts scanning and transporting the film F in the sub-scanning direction (the direction of the arrow b) at the pre-scan speed, and is emitted from the light source 36. The reading light modulated by the variable aperture 48 and diffused by the light diffusion box 50 is incident on the film F conveyed by the carrier 54 so as to be located at the reading position, and the image of the film F is two-dimensionally formed by the slit light. The projection light is focused on the image sensor 68 by the lens unit 64, and the image on the film F is photoelectrically read by the R, G, and B line CCD sensors of the image sensor 68. In the illustrated example, prescanning of all frames is performed first, and the film F is continuously conveyed and prescanned until all of the first to 24th frames are read.

In parallel with the prescan, the DX code and the like recorded on the film F by the carrier 54 are read. In the case of a new photographic system, the magnetic information recorded on the film F is further read. These are sent to the processing device 14 as appropriate, and film information such as a film type and a frame number is detected.

The output signal from the image sensor 68 is amplified by the amplifier 98, converted into digital image data by the A / D converter 100, corrected by the CDS 102, and converted as prescan data from the I / F circuit 104 to the image processing device. 1
4

The pre-scan data sent to the image processing device 14 is subjected to dark correction, defective pixel correction and light correction by the scanner correction unit 106, and is output to the input / output controller 114 by the selector 122, from which the condition setting unit Sent to 110. The condition setting unit 110 extracts the prescan data and the frame position of each frame using the prescan data and the film information. Next, an average value between a predetermined percentage of the pre-scan data of the odd-numbered pixel line of each frame and an average value between a predetermined percentage of the pre-scan data of the even-numbered pixel line are calculated. Can data is calculated. The condition setting unit 110 further creates a density histogram and calculates an image characteristic value for each frame using the calculated corrected pre-scan data of each frame, and uses the image characteristic values of all the frames. Then, film characteristics such as base density are calculated, and book (scan) reading conditions and (image) processing conditions for each frame are set as described above. These processes are, as an efficient example, the reverse order of pre-scan,
That is, the processing is sequentially performed from the 24th frame.

When performing the verification by the operator, the corrected pre-scan data and the processing conditions are sequentially sent to the PC 112. The PC 112 processes the sent corrected pre-scan data under the corresponding processing conditions, and sequentially displays the processed image on the display 26 as a simulation image of an image to be reproduced on a print.

The operator looks at the simulation image displayed on the display 26, sequentially performs the verification from the 24th frame, and adjusts the image for each frame using the adjustment keys of the keyboard 24a as necessary. Do. In response to this, the previously set processing conditions are adjusted (corrected), and at the same time, the simulation image displayed on the display 26 also changes. When the operator determines that the image of the frame is appropriate (verification OK), the operator issues an instruction to end the verification of the frame and performs verification of the next frame.

When the verification of the predetermined number of frames is completed in this way, the operator issues a print start instruction. As a result, the processing conditions of these frames are determined, and the position, reading condition, processing condition, and the like of each frame are sent to the processing unit 126 of the image processing unit 108 and the microprocessor 72 of the scanner 12. Next, in the scanner 12, the carrier 54 starts transporting the film F at a speed corresponding to the main scan in a direction opposite to the prescan, and the main scan is sequentially performed from the 24th frame.

On the other hand, at the same time as the print start instruction, the following simulation images are sequentially displayed on the display 26 in accordance with the setting of the processing conditions by the condition setting section 110. Similarly, the operator performs the verification. Then, a print start instruction is issued, and in response to this, the processing conditions of these frames are determined and transferred to a predetermined portion together with the main reading conditions, and a main scan is performed. Then, the main scan is performed, and the image reading of the film F ends.

The input device 16 for implementing the reading method of the present invention is not limited to the one in which the verification by the operator is always performed, and the print may be created without performing the visual verification. In this case, when the condition setting unit 110 sets the image processing condition and the main scan reading condition, the image processing condition is determined. For example, the image processing condition of a predetermined number of frames and the main scan reading condition are set. At this point, the main scan starts from the 24th frame. When the test is not performed, the display of the simulation image on the display 26 may not be performed. The presence or absence of the test is preferably configured to be selectable as a work mode.

In the scanner 12, the main scan is performed by a press except that the reading conditions such as the pixel density and signal level of reading, the accumulation time (exposure time) of each line CCD sensor of the image sensor 68, and the transport direction of the film F are different. It is performed in the same way as can. The main scan data output from the scanner 12 is processed by the scanner correction unit 106, sent to the image processing unit 108 by the selector 122, and processed by the processing unit 126 according to the processing conditions set for each frame. Is given as image data for output.
The data is sent to the printer 18 via the F circuit 156.

Printer 18 that has received image data for output
As described above, the back print is recorded, and the photosensitive material is scanned and exposed with a light beam modulated according to the image data to form a latent image, and is conveyed to the processor 20. The exposed photosensitive material conveyed to the processor 20 is subjected to predetermined processing such as wet development processing and drying, output as prints, sorted, and accumulated.

In the input device 16 described above, the scanner 12
By reading the original image at a high resolution (main scan) to obtain the image data for print output, and reading the original image at a low resolution to determine the reading conditions and image processing conditions of the main reading prior to the main reading, In a system for performing pre-reading (pre-scan) for obtaining pre-read image data, the image reading method of the present invention is applied to pre-reading. However, the present invention is not limited to this, and a document image is read at a high resolution. In a system in which book reading is performed twice, the present invention may be applied to the first book reading for determining the reading conditions and image processing conditions for the second book reading, or the book reading for reading the original image at high resolution may be performed only once. The present invention may be applied to a system that does not perform this operation. When the present invention is applied to a system in which book reading is performed only once, image processing conditions are determined using corrected book reading image data obtained by applying the present invention to the obtained book reading image data. At the same time, the obtained image processing conditions may be applied to the previously corrected main-read image data to generate print output image data.

Although the image reading method of the present invention has been described in detail, the present invention is not limited to the above-described embodiment, and various changes and improvements may be made without departing from the gist of the present invention. Of course.

[0088]

As described in detail above, according to the image reading method of the present invention, in order to cope with a wide range of densities, pre-scan is performed under a plurality of kinds of reading conditions different in light quantity. In the image reading that determines the reading conditions and the image processing conditions of the main scan using the data, the difference in the pre-scan data caused by the difference in the reading conditions is appropriately absorbed,
Even when image processing conditions and the like for each frame are set from pre-scan data of a plurality of frames, appropriate reading conditions and image processing conditions can be set stably.

[Brief description of the drawings]

FIG. 1 is a block diagram of an example of a photographic printing / developing machine for implementing an image reading method of the present invention.

FIGS. 2A and 2B are schematic views of the scanner of the photographic printing apparatus shown in FIG. 1, wherein FIG. 2A is a front view, FIG.
Shown respectively.

FIG. 3 is a block diagram of an electric system of the scanner shown in FIG.

FIG. 4 is a block diagram of an image processing apparatus of the photographic printing apparatus shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Photo printing developing machine 12 Scanner 14 Image processing device 16 Input device 18 Printer 20 Processor 22 Output device 26 Display 28 Light source part 30 Reading part 36 Light source 44 1st CC filter 46 2nd CC filter 48 Variable diaphragm 48A, 48B Plate 54 Carrier 64 Lens Unit 66 Lens aperture 68 Image sensor 72 Microprocessor 74, 138, 154 Bus 96 Timing generator 106 Scanner correction unit 108 Image processing unit 110 Condition setting unit 112 Personal computer (PC) 114 Input / output controller 122 Selector 156 Interface (I / F) circuit

Claims (13)

[Claims] An original image is photoelectrically read under a plurality of types of reading conditions that differ in light amount, and image characteristic values of the original image are obtained for each of the reading conditions from image signals read under each of the reading conditions. Using the image characteristic values obtained under the respective reading conditions, a difference between signal levels of the image signals under the respective reading conditions is absorbed, and the signal levels of the image signals under the respective reading conditions are matched. Image reading method. 2. The image characteristic value is at least one of an average value over a predetermined range of the cumulative histogram of the image signal, a predetermined point of the cumulative histogram of the image signal, and an average value of the image signal. 2. The image reading method according to claim 1, wherein: 3. The difference between the signal levels of the image signal is:
3. The image reading method according to claim 1, wherein the difference is a light amount difference between the reading conditions. 4. The apparatus according to claim 1, wherein at least one of the number of times of reading a plurality of times and the color of a plurality of times of reading is switched as the reading condition in accordance with the type of the original image. The image reading method described in the above. 5. A document reading means for photoelectrically reading the document image under the plurality of kinds of reading conditions having different light amounts, wherein the document reading means is a line sensor, and reads at different exposure times between predetermined lines. The image reading method according to claim 1. 6. The difference between signal levels of the image signal is:
The image reading method according to claim 5, wherein the difference is a positional deviation difference between the lines by the line sensor. 7. The image reading method according to claim 1, wherein one of a plurality of corrected image signals obtained by matching the signal levels of the image signals under the respective reading conditions is one. An image reading method comprising selecting whether to output an optimal corrected image signal or to combine and output at least two types of corrected image signals from the plurality of corrected image signals. 8. The method of photoelectrically reading the original image under the plurality of types of reading conditions that differ in light amount and matching the signal level of the image signal under each of the reading conditions, includes: The image reading method according to claim 1, wherein the reading is performed in a pre-read performed prior to a main read in which a document image is photoelectrically read. 9. The image reading method according to claim 8, further comprising: using a pre-read correction image signal obtained by matching a signal level of the image signal under each of the reading conditions in the pre-reading. An image reading method, comprising: determining at least one of a reading condition of a main reading and an image processing condition of image processing to be applied to a main reading image signal obtained by the main reading. 10. An optimal corrected image signal or a plurality of corrected images for a plurality of corrected image signals obtained by matching signal levels of the image signals under the respective reading conditions as the pre-read corrected image signal. The image reading method according to claim 9, wherein a combined image signal obtained by combining at least two types of corrected image signals is selected from the signals. 11. The image reading method according to claim 1, wherein said image signal is a digital density signal. 12. An image reading method for photoelectrically reading a document image, wherein prior to main reading for obtaining an output image signal, pre-reading is performed under a plurality of kinds of reading conditions having different light amounts, and the pre-reading is performed. Using the image characteristic value of the image, absorbs the difference between the pre-read image signals caused by the difference in the read conditions, and uses the pre-read corrected image signal that has absorbed the difference between the image signals, and uses the read-ahead read conditions and An image reading method, wherein at least one of image processing conditions for performing image processing on an image signal obtained by the main reading is determined. 13. The image characteristic value is at least one of an average value between a predetermined percentage point and a predetermined percentage point of the histogram based on the image signal, a predetermined percentage point of the histogram based on the image signal, and an average value of the image signal. The image reading method according to claim 12, wherein: