JPH04167654A - Scanner device - Google Patents

Abstract

PURPOSE:To reproduce a visually satisfactory picture by a reproducing device by using two image sensors which convert a picture signal to an electric signal and providing an ND filter on the optical path of one image sensor. CONSTITUTION:A first image sensor 1 and a second image sensor 2 are attached to a step driving device 3, and an ND filter (density filter) 4 provided closely to the second image sensor 2 attenuates the quantity of visible light to, for example, 1/10 in all bands. Since the ND filter is provided on the optical path of the image sensor for highlight light in this manner, a normal light area is converted with a high sensitivity by the image sensor for normal light, and the highlight part extending to the saturation area of the image sensor for normal light is converted by the image sensor provided with the ND filter without extending to the saturation area. Thus, the exposure which is wide-range as the whole is converted to an electric signal without losing picture information.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a scanner device that converts image information of a color document into an electrical signal and outputs the electrical signal.

(Prior art) Conventionally, the image information of a color original is passed through color separation filters of the three primary colors, red, green, and blue, and the pixel information is line-scanned for each color using a self-scanning image sensor such as a CCD. A color scanner that reproduces color information of a color original by sequentially reading images and combining three types of image signals is generally known.

FIG. 2 is a schematic diagram of a color scanner using a conventional reduction optical system. In the figure, 21 is an illumination light source for positive film, 22 is a positive film that will be a color original, 23 is a lens that forms an image of transmitted light from the positive film surface on an image sensor, and 24 is a lens that converts light emitted from the lens into red and green. , a color separation filter that switches the transmission of blue; 25 is a drive mechanism that moves the color separation filter stepwise at a predetermined pitch in the vertical direction; 26 is a line-type image sensor that converts color-separated image information into electrical signals. 127 is an amplifier, 2
8 is an A/D conversion circuit that converts the amplified analog signal from the image sensor into a digital signal, 29 is a buffer memory that stores digital signal data, 30 is a mass storage device, 31 is a microcomputer, and 32 is a frame. 33 is a display such as a CRT, 34 is a drive circuit, and a portion 35 surrounded by a dotted line constitutes the main part of the scanner device.

The image information photographed on the positive film 22 is transmitted to the illumination light source 2
After the brightness of the lens 1 and the aperture and focal position of the lens 23 are adjusted, an image is formed on the image sensor 26 by the lens 23. The image sensor 26 is moved vertically by a drive mechanism 25 in predetermined steps in synchronization with the movement of the color separation filter 24 to obtain image information for each color.

During this vertical step period, the image sensor 26 performs electrical horizontal scanning and converts the image information of each pixel into an electrical signal for each line, and the output is sent to the amplifier 27.
The signal is amplified by the A/D converter 28, converted into a digital quantity, stored in the buffer memory 29, and then stored in the mass storage device 30. As the mass storage device 30,
- For boat fishing, hard disks, optical disks, etc. are used.

These controls are performed by the microcomputer 31. The obtained image data is processed by a microcomputer 31 and stored in a frame memory 32, for example.
One page is stored and reproduced on the CRT display 33. Data processing of the reproduced image is corrected to match the gamma value (approximately 2°3) of the CRT. - When fishing on a boat, image reproduction is not performed at the same time as the image is taken, but is performed after the necessary image is taken and data processing is completed. A CCD or the like can be used as the image sensor, and is driven by a drive circuit 34 in synchronization with a drive mechanism.

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

When an image sensor that converts such an input image into an electrical signal uses a CCD (charge-coupled device), the relationship between the exposure amount and the output voltage exhibits a saturation characteristic. FIG. 3 is an example of this, and is shown in a diagram with the vertical axis representing the output voltage and the horizontal axis representing the illuminance of the exposure amount.

Both axes are expressed on logarithmic axes. As you will see from now on,
A CCD exhibits linear characteristics from the light amount of minimum sensitivity to a certain value, but beyond that it has a limit, that is, a saturation point, and the dynamic range is about 102.3.

However, the positive film used for color originals is
-For boat fishing, the concentration range is 3 (the dynamic range is about 1)
03), so even if you try to convert the transmitted light of the positive film into an electrical signal with an image sensor, as mentioned above, the image sensor has a narrow dynamic range, so the dark areas (high density areas) will be crushed. The highlights (areas with low density) will be blown out. However, even if the highlight area occupies a few tenths of the screen, it gives a strong visual impression in the reproduced image, so in order to actually obtain image information, it is necessary to sacrifice the dark area. Then, the lighting and lens aperture are adjusted so that the highlight area is below the saturation point of the image sensor, and recording is performed. Therefore, other parts are underleveled and dark, and the quality of the reproduced image on a display or the like is poor as a whole.

In this way, by converting an image with a wide dynamic range into an electrical signal, the reproduced image is not limited to extremely high-level highlights; It is also important to faithfully reproduce images. The final evaluation is determined by visual evaluation, but it must be possible to visually evaluate the reproduced image so that it feels almost the same as the original. However, due to the dynamic range of the image sensor described above, the dynamic range of the converted signal is narrow, making it difficult to convert any image in a way that will produce a high-quality reproduced image. .

Furthermore, CRT displays, which are most commonly used as a means of making reproduced images visually, have a small contrast ratio of about 50, and even when used in an environment that avoids external light, the contrast ratio is only 3. Even if the image information is 4 times larger than that of a positive film, the image simply converted into an electrical signal and reproduced on a display cannot be said to be a visually satisfactory image.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and it widens the substantial dynamic range of the image sensor to provide image information from high-density areas to low-density areas. The purpose is to provide a scanner device that can perform data conversion without basically losing data, and in the image processing process from the obtained data, the characteristics required on the playback device side, such as comma correction. It is an object of the present invention to obtain data that enables the reproducing apparatus to reproduce images that are sufficiently visually satisfying, and that also enables the reproduction of images from positive film, which are color images.

(Means for Solving the Problems) The present invention is characterized in that, in a scanner device, two image sensors that convert image information into electrical signals are used, and an ND filter is provided in the optical path of one of the image sensors. That is.

One of the image sensors
It is possible to perform gamma correction on the output from the image sensor, provide an ND filter in the optical path of the other image sensor, and perform highlight compression correction on the output.

Each of the corrections converts each of the outputs into a digital signal,
The converted digital data can be converted based on the conversion table.

(Function) In converting image information with a high contrast ratio into a digital signal, the present invention uses a plurality of image sensors divided into one for normal light and one for highlight light. By providing an ND filter in the optical path, the normal light region can be converted with high sensitivity by the normal light image sensor, and the highlight part in the saturated region of the normal light image sensor can be converted using the ND filter. The image sensor provided with a filter can perform conversion without entering the saturation region, and as a whole, it can be converted into an electrical signal without losing image information over a wide range of exposure amounts.

In addition, since the area assigned to each image sensor is divided, by giving different correction characteristics to each output, it is possible to apply correction according to the contrast ratio of the reproduction device, for example, C depending on the area of exposure
Performs correction according to the gamma characteristics of the RT display,
It is possible to synthesize image information signals in which the contrast ratio of the reproduced image is close to that of the actual image. Thereby, a visually high-quality image can be reproduced on the 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, an image sensor 13 denoted by 1 and 2 is a drive mechanism, which corresponds to the image sensor 26 and the drive mechanism 25 described in FIG. 2, and receives 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. 2. 4 is an ND filter provided on one image sensor 2; 5 and 6 are amplifiers; 7.
8 is an A/D converter, 9 and 10 are memory circuits, 11.12
13 is a conversion table, 13 is a control circuit, 14 is a D/A conversion circuit, 15 is a synthesis circuit, 16 is a digital output terminal, 17
is an analog output terminal. An EPROM or the like can be used for the conversion tables 11 and 12.

Image sensors 1 and 2 that convert image information into electrical signals
The first image sensor 1 converts the dark part of the light into normal light, and the second image sensor 2 is equipped with an ND filter 4 on the front that reduces the amount of light to one-tenth, and the second image sensor 2 converts the dark part of the light into normal light. Transform the light domain. The output signals from both image sensors are amplified by amplifiers 5 and 6, respectively, and then converted into digital values by A/D converters 7 and 8, and subjected to characteristic conversion 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 that is the image information of the first image sensor-1, and
The OM conversion table 11 has a characteristic of compressing the image information of the highlight portion from the second image sensor 2.

The digital data whose characteristics have been converted are combined and output as image information. When connected to a CRT display, it performs D/A conversion and outputs three types of analog images: red, green, and blue.

This will be explained in detail below.

First image sensor-1 and second image sensor-2
is attached to the step drive device 3 and driven in a direction perpendicular to the line direction of the image sensor. An ND filter (density filter) provided in close contact with the second image sensor attenuates the amount of light to, for example, one tenth over the entire visible light band. The scanning outputs of the image sensors 1 and 2 are amplified by amplifiers 7 and 8, respectively, and then linearly quantized as, for example, 8-bit data by A/D conversion circuits 7 and 8. is memorized. However, the light input to the image sensor 2 for the same pixel is delayed by the number of vertical steps corresponding to the difference in the arrangement distance between the two, compared to the light input to the image sensor 1, so it is difficult to process the signal. is for the output from image sensor-1,
A delay equal to the number of steps is given to combine the Ryoro forces of the same pixel.

These controls are performed by the control circuit 13 controlling reading of the memory circuits 9 and 10 in response to a start/stop command signal from the microcomputer.

In this explanation, illustrations for each color have been omitted, but in the case of color separation filters of three colors, red, green, and blue, the data for one pixel is 3 for each image sensor, making a total of 6 data. is obtained, so in the end, 1
A total of six screens of output will be obtained.

These screen outputs are stored in mass storage,
In this embodiment, characteristic conversion is performed and the respective color outputs are combined and stored in a mass storage device.

Characteristic conversion is performed on the data read out from the memory circuits 7 and 8, taking into account the number of steps based on the arrangement of the image sensor described above, based on conversion tables 11 and 12 stored in an EPROM, for example. The value is converted and output from the synthesis circuit 15 to the output terminal 16. Of course, the synthesized output can be D/A converted into an analog output, which can be supplied from the analog output terminal 17 to an image output device such as a CRT.

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

First, the output of the image sensor 1 will be explained.

If you ignore the highlight light and take the bright area over the entire screen as the 100% level, for example, looking at point a in Figure 3, the light intensity corresponding to a density of 2 lux/second is 1v.
Obtain an amplified output voltage of

Consider the case where 8-bit quantization is performed in A/D conversion.

For 8 bits, the highest level value is 256. - The 100% level of TV for fishing on a boat is treated as 235, but in order to take the highlight part into account and quantize it to a level of 85%, the manual exposure amount is 2 lux seconds. Perform digital conversion so that the image output IV is 200,
The data is stored in the memory circuit 10.

On the other hand, since the output signal of image sensor 2 is one-tenth the size of the output of image sensor 1 due to the provision of the ND filter, The exposure amount of lux/second is equivalent to the exposure amount of 20 lux/second before passing through the ND filter, so even with such a large exposure amount, images can be taken without reaching the saturation voltage, and the digital value and stored in the memory circuit 9. In the image sensor 2, the manual exposure amount of 2 lux/second becomes the exposure amount of 0.2 lux/second at point b, and the output becomes 0°1V.

Next, EPROM conversion table 1 that receives these outputs
An example of 1.12 will be explained.

The EPROM conversion table 12 for correcting the output of the image sensor 1 has a comma value γ of the CRT display.
:2,2 is to be converted into a characteristic having γ=0.45. Figure 4 shows the relationship between output and human power, and the human power digital value 50 is 116.1.
00 is converted to 156.200 is converted to 200, human power is 20
If it is 1 or more, the converted output is O.

The EPROM conversion table 11 corrects the output of the image sensor 2 which receives the exposure amount attenuated by the ND filter. The manual exposure amount of 2 lux seconds corresponding to point a in FIG. 2 is attenuated to 1/10 to 0. It becomes the output of IV,
Since the digital value is 100, the conversion characteristics are as shown in Figure 5. If the human power is 100 or less, it is converted to 201 at 01101, and thereafter the data is converted linearly so that the human power of 256 becomes an output of 256. Convert. As a result, it is possible to record and reproduce an image with a light intensity 10 times the light intensity at the 85% point in the range of 85% to 100% when the maximum output level is 100.

Digital values in the ranges 0 to 200 and 201 to 256, which are the outputs of the two EPROM conversion tables 11 and 12, are synthesized by the synthesis circuit 15 in FIG. 1 to form a digital output. The converted digital value may be converted into an analog value by the D/A conversion circuit 14 and then introduced to a CRT display or the like. For D/A conversion, a synchronization signal is led from the control circuit 13 and the memory circuit 9
It is possible to synchronize the timing with the data conversion using the EPROM conversion table.

(Effects of the Invention) As is clear from the above description, the present invention provides a scanner device that can read image information, etc. of a positive film while eliminating the collapse of dark areas and skipping of highlight areas. It can be used for CRT displays, etc.
This has the effect of reproducing visually high-quality images. Also,
The read image information can be played back immediately.
It can also be stored in a storage device.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a scanner device for explaining the 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-13... Drive mechanism, 4
...ND filter, 5, 6... Amplifier, 7, 8...
・A/D converter, 9, 10... memory circuit, 11.1
2... Conversion table, 13... Control circuit, 14...
・D/A conversion circuit.

Claims (1)

[Claims] A scanner device characterized in that it uses two image sensors that convert image information into electrical signals, and that an ND filter is provided in the optical path of one of the image sensors.