JPH0748787B2 - Scanner device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanner device that converts image information of a color original into an electric signal and outputs the electric signal.

(Prior Art) Conventionally, image information of a color original is passed through color separation filters of three primary colors, red, green, and blue, and pixel information is sequentially scanned line by line with a self-scanning image sensor such as a CCD. It is generally known that a color scanner is configured to read in 3 to synthesize three types of image signals to reproduce color information of a color original.

FIG. 2 is a schematic configuration diagram of a color scanner using a conventional reduction optical system. In the figure, 21 is an illumination light source for a positive film, 22 is a positive film that is a color original, 23 is a lens that focuses the transmitted light of the positive film surface on an image sensor, and 24 is light emitted from the lens in red and green, A color separation filter that switches blue transmission, 25 is a drive mechanism that moves the color separation filter stepwise in a vertical direction by a predetermined pitch, 26 is a line type image sensor that converts color separated image information into an electric signal, and 27 is An amplifier, 28 is an A / D conversion circuit for converting the amplified analog signal from the image sensor into an odidigital signal, 29 is a buffer memory for storing digital signal data, 30 is a mass storage device, 31 is a microcomputer, 32 Is a frame memory, 33 is a CRT
And the like, 34 is a drive circuit, and a portion 35 surrounded by a dotted line constitutes a main part of the scanner device.

The image information photographed on the positive film 22 is imaged on the image sensor 26 by the lens 23 after the brightness of the illumination light source 21, the diaphragm and the focus position of the lens 23 are adjusted. The image sensor 26 is driven by a drive mechanism in synchronization with movement of the color separation filter 24 for obtaining image information for each color.
It is moved vertically in a predetermined step by 25. During this vertical step period, the image sensor 26 performs an electrical horizontal scan, converts the image information of each pixel into an electrical signal for each line, and the output is amplified by the amplifier 27 and A / D converted. It is converted into a digital amount by the device 28, stored in the buffer memory 29, and stored in the mass storage device 30. A hard disk, an optical disk, or the like is generally used as the mass storage device 30. These controls are performed by the microcomputer 31. The obtained image data is processed by the microcomputer 31, one page is stored in the frame memory 32, and reproduced on the CRT display 33. The data processing of the reproduced image is corrected to match the gamma value (about 2.3) of the CRT. Generally, image reproduction is not performed at the same time as image capturing, but is performed after the required image capturing and data processing are completed. A CCD or the like can be used for the image sensor, and is driven by the drive circuit 34 in synchronization with the drive mechanism.

In the above description, as an input image to be converted into image data, an image transmitted through a photographed color film is taken as an example, but it is obvious that a reflection original can be used as an input image depending on the optical system used. .

When a general CCD (charge coupled device) is used as an image sensor that converts an input image into an electric signal, the relationship between the exposure amount and the output voltage shows a saturation characteristic. FIG. 3 is an example thereof, and is shown in a diagram in which the vertical axis represents the output voltage and the horizontal axis represents the illuminance of the exposure amount. Both axes are logarithmic. As can be seen, the CCD shows a linear characteristic from the light amount of the minimum sensitivity to a certain fixed value, but beyond that, it has a limit, that is, a saturation point, and the dynamic range is 10
It is about ^2.3 .

However, the positive film used as a color original is
Generally, the concentration range is 3 (the dynamic range is about 10
^Since it is about ³ ), even if an attempt is made to convert the transmitted light of the positive film into an electric signal by the image sensor, as mentioned above, the dark part (high density part) is crushed due to the narrow dynamic range of the image sensor, The highlight part (the part where the density is low) is skipped. However, the highlight part gives a strong visual impression in the reproduced image even when the area occupies about several tenths of the screen. Therefore, in order to actually obtain image information, the dark part is sacrificed. Then, the illumination and lens aperture are adjusted so that the highlight area is below the saturation point of the image sensor for recording. Therefore, the other part becomes an under level and becomes dark, and the reproduced image on the display or the like is of poor quality as a whole.

In this way, an image with a wide dynamic range is converted into an electric signal, and the reproduced image is not limited to the highlight part of extremely high level, but generally, the light amount range occupying most of the area is covered. It is also important to faithfully reproduce the image. Although the final evaluation is of the nature determined by visual evaluation, it must be capable of visual evaluation so that the reproduced image feels almost the same as the original. However, due to the above-mentioned dynamic range of the image sensor, the converted signal has a narrow dynamic range, and it has been difficult to perform conversion on any image so as to obtain a high quality reproduced image.

In addition, the CRT display, which is most often used as a means for visualizing reproduced images, has a small contrast ratio of about 50, and even if it is used in an environment that avoids external light, Even if the image information of the positive film is 4 times at most, the image that is simply converted into an electric signal and reproduced on the display cannot be said to be an image that is visually satisfactory.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, in which a substantial dynamic range of an image sensor is widened and image information from a high density portion to a low density portion is basically used. It is an object of the present invention to provide a scanner device that can convert data without being lost, and characteristics required on the reproducing device side in an image processing process from the obtained data,
That is, it is possible to perform gamma correction and reproduce a visually satisfactory image by the reproducing device.
The purpose is to obtain data that can sufficiently reproduce an image from a positive film which is a color image.

(Means for Solving the Problems) According to the present invention, in a scanner device, a first image sensor for converting image information into an electric signal and an ND filter provided in the optical path in parallel with the first image sensor are provided. A second image sensor, A / D conversion means for digitally converting the signal output of the first image sensor and the signal output of the second image sensor, respectively, and the converted digital image of the first image sensor. A first table for gamma-correcting the signal output, a second table for compressing and correcting the converted image information of the highlight portion of the converted digital signal output of the second image sensor, and the corrected digital signal output It is characterized in that it has a synthesizing means for obtaining a synthesized signal based on the above.

(Operation) In the present invention, when converting image information having a high contrast ratio into a digital signal, a plurality of image sensors for normal light and for highlight light are used, and the optical path of the image sensor for highlight light is used. By providing an ND filter, the normal light area can be converted with good sensitivity by the image sensor for normal light, and the highlight part of the saturated area of the image sensor for normal light is
An image sensor equipped with an ND filter can be converted without affecting the saturation region, and as a whole, it can be converted into an electric signal without losing image information over a wide range of exposure dose.

Further, since the area shared by each image sensor is divided, it is possible to give a correction according to the contrast ratio of the reproducing apparatus by giving different correction characteristics to each output. CR according to quantity area
It is possible to perform the correction according to the gamma characteristic of the T display and synthesize the image information signal in which the contrast ratio of the reproduced image is close to the actual image. This makes it possible to reproduce a visually high quality image on a CRT display at the same time as the image is taken.

(Embodiment) FIG. 1 is a schematic configuration diagram of a scanner device for explaining an embodiment of the present invention. In the figure, 1 and 2 are image sensors, and 3 is a drive mechanism, which correspond to the image sensor 26 and the drive mechanism 25 described in FIG. 2, and receive an image from the reduction optical system. Although not shown, a color separation filter is provided in front of the image sensor as in FIG. 4 is an ND filter provided on one image sensor 2, 5 and 6 are amplifiers, 7 and 8 are A / D converters, 9 and 10 are memory circuits, 11 and 12 are conversion tables, 13 is a control circuit, 14 Is a D / A conversion circuit, 15 is a combining circuit, 16 is a digital output terminal, and 17 is an analog output terminal. An EPROM or the like can be used for the conversion tables 11 and 12.

The image sensors 1 and 2 for converting image information into electric signals are used. The first image sensor 1 performs normal light conversion from a dark portion of light, and the second image sensor 2 has a front surface.
The ND filter 4 that reduces the light amount is provided to one-half to convert the highlight light region. Output signals from both image sensors are amplified by amplifiers 5 and 6, respectively, converted into digital values by A / D converters 7 and 8, and characteristic conversion is performed by EPROM conversion tables 11 and 12. In this embodiment, the EPROM conversion table 12 has a characteristic of performing gamma correction on the digital signal which is the image information of the first image sensor 1, and the EPROM conversion table 11 has the highlight portion from the second image sensor 2. It has a characteristic of compressing image information of. The characteristic-converted digital data are combined and output as image information. CRT
When connecting to a display, convert D / A, red,
Outputs three kinds of green, blue, and analog images.

The details will be described below.

First image sensor 1 and second image sensor 2
Is attached to the step drive device 3 and is driven in a direction perpendicular to the line direction of the image sensor. The ND filter (density filter) provided in close contact with the second image sensor attenuates the amount of light over the entire visible light band to, for example, 1/10. The scan outputs of the image sensors 1 and 2 are amplified by amplifiers 7 and 8, respectively, and then linearly quantized as 8-bit data by the A / D conversion circuits 7 and 8 and stored in the memory circuits 9 and 10. To be done.
However, the image sensor 2 for the same pixel
The light input to the image sensor 1 is delayed from the light input to the image sensor 1 by the number of vertical steps corresponding to the difference in the arrangement distance between the two. , So that both outputs of the same pixel are combined by delaying the number of steps.

For these controls, the control circuit 13 receives the start / stop command signal from the microcomputer, and the memory circuit 9,
This is done by controlling the reading of 10. Although illustration of each color is omitted in this description, in the case of three colors of color separation filters red, green, and blue, the data for one pixel is 3 for each image sensor, and a total of 6 data are available. As a result, a total of 6 screens are output for one screen. These screen outputs are stored in the large-capacity storage device. In this embodiment, characteristic conversion is performed to combine the respective color outputs to be stored in the large-capacity storage device.

Characteristic conversion is performed on the data read from the memory circuits 7 and 8 in consideration of the number of steps based on the arrangement of the image sensor described above, for example, the data value based on the conversion tables 11 and 12 stored by the EPROM. Is converted and output from the synthesizing circuit 15 to the output terminal 16. Of course, the composite output is D / A converted to analog output, and the analog output terminal 17
To an image output device such as a CRT.

Here, the relationship between the exposure amount and the image sensor output will be described.

First, the output of the image sensor 1 will be described. Ignore highlight light and select 10 bright areas across the entire screen.
At the 0% level, for example, looking at point a in FIG. 3, a light output corresponding to a density of 2 lux · sec gives an amplified output voltage of 1V. Consider a case where quantization is performed by A / D conversion using 8 bits. With 8 bits, the highest level value is 256. Generally, the 100% level of TV is treated as 235, but here the quantization is 85% considering the highlight part.
In order to obtain the level that becomes, the image output 1V with the input exposure amount of 2 lux · second is digitally converted to 200,
It is stored in the memory circuit 10.

On the other hand, the output signal of the image sensor 2 is less than that of the output of the image sensor 1 due to the provision of the ND filter.
Since it is one-half the size, the exposure amount of 2 lux · sec at point a in FIG. 3 in the image sensor 2 corresponds to the exposure amount of 20 lux · sec before passing through the ND filter. Even with such a large amount of exposure, it is possible to take a photograph without reaching the saturation voltage, and it is converted into a digital value and stored in the memory circuit 9. In the image sensor 2, the input exposure amount of 2 lux · sec becomes the exposure amount of 0.2 lux · sec at the point b, and the output becomes 0.1V.

Next, an example of the EPROM conversion tables 11 and 12 that receive these outputs will be described.

The EPROM conversion table 12 that corrects the output of the image sensor 1 uses the gamma value γ = 2.2 of the CRT display as γ
A case where the characteristic is converted to have a value of 0.45 will be described as an example. FIG. 4 shows the relationship of the output to the input. The input digital value 50 is converted into 116, 100 is converted into 156, and 200 is converted into 200. When the input is 201 or more, the converted output is 0.

The EPROM conversion table 11 corrects the output of the image sensor 2 which receives the exposure amount attenuated by the ND filter. The input exposure amount of 2 lux seconds corresponding to point a in Fig. 3 is
As it is attenuated to 1/10 and becomes 0.1V output and the digital value is 100, the conversion characteristics are as shown in Fig.5.
The input less than 100 is converted into 201 with 0 and 101, and thereafter, the data is linearly converted so that 256 inputs are output to 256 outputs. As a result, when the maximum output level is 100, 85
In the range of 100% to 100%, it is possible to record / reproduce an image having a light amount 10 times the light amount at the 85% point.

Output of two EPROM conversion tables 11 and 12, 0-200
And the digital value in the range of 201 to 256 is the synthesis circuit of Fig. 1.
It is synthesized by 15 and becomes a digital output. The converted digital value may be converted into an analog value by the D / A conversion circuit 14 and led to a CRT display or the like. In the D / A conversion, a synchronization signal is guided from the control circuit 13, and the timing can be matched with the reading of the memory circuits 9 and 10 and the data conversion by the EPROM conversion table.

(Effects of the Invention) As is apparent from the above description, according to the present invention, there is provided a scanner device capable of reading image information and the like of a positive film by eliminating crushing of a dark portion and jumping of a highlight portion. It has the effect of being able to reproduce visually high quality images when used in CRT displays and the like. Further, the read image information can be immediately reproduced or can be stored in the storage device.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a scanner device for explaining an outline of an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a color scanner using a conventional reduction optical system, and FIGS. 5
The figure is an explanatory diagram of data conversion. 1,2 …… Image sensor, 3 …… Drive mechanism, 4 …… ND
Filter, 5,6 ... Amplifier, 7,8 ... A / D converter, 9,10 ...
… Memory circuit, 11,12 …… Conversion table, 13 …… Control circuit, 14 …… D / A conversion circuit.

Claims (1)

[Claims] 1. A first image sensor for converting image information into an electric signal, a second image sensor provided in parallel with the first image sensor and having an ND filter in an optical path, and the first image sensor. A / D conversion means for digitally converting the signal output of the image sensor and the signal output of the second image sensor, and a first gamma correction for the converted digital signal output of the first image sensor.
Table, a second table for compressing and correcting the converted image information of the highlight portion of the converted digital signal output of the second image sensor, and a synthesizing means for obtaining a synthesized signal based on these corrected digital signal outputs. A scanner device comprising: