JPH01238368A - Device for reading color information of picture - Google Patents

Abstract

PURPOSE:To precisely synthesize the photoelectrical conversion information of each color of green, blue, and red by setting picture element pitches of image pickup elements other than a reference image pickup element by multiplying the picture element pitch of the reference element by the ratio of magnifications of the other elements to the magnification of the reference element when one of each image pickup element for each color light is used as the reference image pickup element. CONSTITUTION:When it is assumed that a relation of, for example, fR>fG>fB exists among the focal distance fR, fG, and fB of each color, a relation of lR>lG>lB exists among the optical distance lR, lG and lB from an image forming lens 21 of each image pickup element SR, SG, and SB. Moreover, when one of each image pickup element for each color light, for example, the image pickup element SB for blue color is used as a reference image pickup element, pitches PG and PR for the image pickup elements SG and SR for green and red colors respectively become those decided by PG=PB.lG/lB and PR=PB.lR/lB. Since each picture element is arranged at a position, at which the difference in magnification, namely, shift in the height direction is anticipated in such way, the color information of a picture can be read precisely even when a non-telecentric optical system is used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image color information reading device.

(Prior Art) In the field of image reading, many attempts have been made to read color images.

When reading a color image, it is naturally necessary to obtain the color information of this image. Generally, this color information is obtained by dividing the light from the image into B (red), G (green) and It is obtained by separating the light into each color of B (blue), making the light of each color incident on an image sensor, and synthesizing the information photoelectrically converted by the image sensor.

Here, it is possible to obtain photoelectric conversion information for each color light using the same image sensor, but due to chromatic aberration of the lens of the optical system, each color has a high MTF (Modulation
Transfer Function). Therefore, in order to obtain a high MTF for each color, an image sensor is dedicated to each color light, and these image sensors are placed at appropriate positions taking into account chromatic aberration, and photoelectric conversion information obtained from each image sensor is used. The color information of an image is obtained by compositing the images.

(Problems to be Solved by the Invention) However, when an image sensor is provided for each color of light as described above, the distance from the optical system to the image sensor becomes different for each color. Therefore, for example, when a non-telecentric optical system is used, a difference in magnification occurs between each image sensor, resulting in a deviation in image height. The color information obtained when the image height shifts in this way is no longer accurate for reasons explained below with reference to FIG. 2. FIG. 2 schematically shows a part of a device used for reading color information that obtains photoelectric conversion information of a certain color after three-color separation of light from an image.

In FIG. 2, 11 indicates a non-telecentric optical system. Further, those with SC are, for example, image pickup elements for green light, which are placed at the appropriate position II (this position N is indicated by the distance wif from the optical system 11) in consideration of chromatic aberration,
This is a line sensor having n pixels at a predetermined pitch.

Further, SII indicates, for example, an image sensor for red light. This image sensor SR is originally located at a different location, but for convenience of explanation, it is shown together in FIG. 2.The configuration of this image sensor SR is the same as that of the image sensor S0. but,
Since chromatic aberration is taken into consideration, the position of the image sensor SR is set at a position M (position of SG -
The difference between the two is indicated by Δf. )become.

In such a system, light from the image. is optical system 11
When the light is incident on the optical axis, the light near the optical axis is
. Further, the light is incident on the pixel at the same position indicated by SRO. However, as the distance from the optical axis increases, the light flux from the optical system 11 to the image sensor becomes angular with respect to the optical axis. Therefore, the light incident on the pixel indicated by 5GII of the image sensor indicated by Sa, for example, is indicated by SR. SR in image sensor? When the image height on the image sensor indicated by esG, which causes a shift in image height such that the light is incident on the pixel indicated by , is indicated by y, the shift in image height △y that occurs on the image sensor indicated by SR is, △ It is expressed as y=Δf −y/f.

If the information of each pixel of each image sensor for blue, green, and red is simply synthesized with pixels on the same level in a state where such an image height difference has occurred, it would originally be 5Gli, Sl
l? and S, x (S8x means the corresponding pixel position on the blue image sensor). Sea, SC8 and 5RE
Since the information of I is synthesized, the color information of the image is no longer accurate, causing color misalignment. The effect of such image height deviation becomes more pronounced as the pixels of the image sensor become smaller, that is, as the image is read with higher resolution.

To avoid this, conventionally, a telecentric optical system has been used that allows light from an image to enter the image sensor perpendicularly. However, the telecentric optical system has a complicated structure and is expensive, which complicates the structure of the image color information reading device and increases the cost of the device. It wasn't a good thing.

This invention was made in view of these points,
Therefore, an object of the present invention is to provide a color information reading device that can accurately read color information of an image even when a non-telecentric optical system is used.

(Means for Solving the Problems) In order to achieve this object, according to the present invention, there is provided a means for separating into three colors light from an image incident through an optical system, and means for separating chromatic aberration for each color light. In a device that reads color information of an image by combining information obtained from the pixels of each image sensor, the optical system described above is non-telecentric. When one of the above-mentioned image sensors for each color light is used as a reference image sensor, the pixel pitch of the other image sensor is equal to the pixel pitch of the above-mentioned reference image sensor. It is characterized in that the ratio is multiplied by the ratio of the magnification of the image sensor and the magnification of the reference image sensor.

Note that the image referred to here refers to visual information expressed or reproduced in a two-dimensional or more-dimensional area by some technical means.

Moreover, the image sensor mentioned here mainly means a solid-state image sensor, and examples thereof include a CCD type image sensor and a MOS type image sensor.

Moreover, the ratio of the magnification of the other image pickup device and the magnification of the reference image pickup device mentioned here is as follows, taking the green image pickup device SG and the red image pickup device SR shown in FIG. 2 as an example. It can be said that it is explained as follows. The ratio of the image height y on the green image sensor SO to the image height (y+Δy) on the red image sensor SR, or the distance f from the optical system 11 to the green image sensor S0, and the optical system 11 to the red image sensor SR (f+Δf).

(Function) According to this configuration, each pixel of each image sensor for each color is mounted at a position that takes into account the difference in image height. Photoelectric conversion information of each blue and red light can be appropriately combined.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

However, each figure used in the following explanation is only a schematic illustration to the extent that this invention can be understood, and therefore,
It should be understood that the dimensions, shapes, Mm distributions, etc. of each component are not limited to the illustrated example.

FIG. 1(A) is a diagram schematically showing a configuration for reading color information of an image and creating a drawing according to an embodiment of the present invention.

In FIG. 1(A), 21 indicates a non-telecentric imaging lens, and this imaging lens 21 receives light Lo from the image.
It focuses the light. Reference numeral 23 indicates a three-color separation system, which in this case is composed of glycoic mirrors. This three-color separation system 23
is light from an image focused by the imaging lens 21. of,
Three color lights of R (red), G (green) and B (blue) R, L
It is decomposed into c and 8.

The separated color lights are respectively incident on individual image pickup devices indicated by SR, SG, or S8, which are prepared for each color light and placed at positions that take into account chromatic aberration.

Note that each image sensor is connected to a control circuit indicated by 25. The control circuit 25 samples the photoelectric conversion information obtained from the pixels of each image sensor, performs A/D conversion, and stores the obtained digital signal in a predetermined area of a memory (not shown). Then, the photoelectric conversion information of corresponding pixels for each color is combined to obtain color information of the image. Since the control circuit 5 can be constructed from a known circuit that has been conventionally used for reading information from an image sensor, a description of its internal configuration will be omitted.

In addition, each image sensor S, , S, and S8 are in this case CCO
This is a line sensor composed of a shaped image sensor. These image sensors have different pixel pitches for each image sensor. Regarding this, Figure 1 (B)! Explain with reference.

FIG. 1(B) is a diagram in which the image sensors SR, S, and s8 are shown together in a common drawing for convenience of explanation. Note that for convenience of explanation, the size of each pixel is exaggerated.

Since each image sensor S pI, S a or S takes into account chromatic aberration, the focal length of each color f R, f G
Assuming that +f8 is in the relationship f R > f a > f [l, the optical distance of each image sensor from the imaging lens 21 is β5. ρ0 or ρ8 is β6〉! . 〉The relationship is β8. It goes without saying that the relationship between f , f , and f is determined by the achromatic design of the optical system.

Furthermore, the pixel pitches PR, PG, or P8 of each image sensor have a predetermined relationship with each other, but are different pitches from each other. That is, when one of the image sensors for each color light, for example, the image sensor S for blue light, is used as a reference image sensor, the image sensor S for green light. pixel pitch P. , the pixel pitch P6 of the image sensor SR for red color is Pa = Pa ·β. /ρ8 PR=Ps ・β, /18 In other words, the pixel pitch of the reference image sensor is multiplied by a value corresponding to the ratio of the magnification of another image sensor to the magnification of the reference image sensor. It has become a thing.

In the example shown in FIG. 1B, the dimensions Xs, Xo, or Xll of the effective imaging area (aperture) of one pixel of each image sensor in the longitudinal direction of the image sensor are XII x C.

<X, l, and each dimension is set to correspond to the magnification ratio. however,
It should be understood that these dimensions Xs, XG, or X may be changed depending on the design of the color information reading device, and are not limited to this example.

(Effects of the Invention) As is clear from the above description, according to the image color information reading device of the present invention, each pixel of each Furukawa image sensor is positioned at a position that takes into account the difference in magnification, that is, the deviation in image height. Since the light beams are respectively placed in the same area of the image, the photoelectric conversion information obtained from each of the green, blue, and red lights from the same area of the image can be accurately synthesized.

Therefore, even when a non-telecentric optical system is used, the color information of an image can be accurately read.

[Brief explanation of the drawing]

FIG. 1(A) is a diagram schematically showing the overall configuration of the image color information reading device according to the embodiment, and FIG. 1(8) is an image sensor provided in the image color information reading device of the present invention. FIG. 2 is a diagram schematically showing the Hitotsubashi construction example, and is a diagram used to explain the conventional method and the present invention. 21...Non-telecentric imaging lens 23-...
- Three-color separation system 25...Control circuit Lo...Light SR from the image...Image sensor Sa for red light, Image sensor Ss for green light, Image sensor P for blue light, - ...Pixel pitch P0 of the image sensor for blue light...
Pixel pitch of the image sensor for green light PR""Pixel pitch of the image sensor for red light Xa""Aperture size of the pixels of the image sensor for blue light xG...Pixel aperture of the image sensor for green light Part dimension Distance β□: Optical distance between the optical system and the red light image sensor. Patent applicant: Asahi Optical Industry Co., Ltd. Figure 1 (B)

Claims (1)

[Claims] (1) It has a means for separating light from an image incident through an optical system into three colors, and an image sensor having a large number of pixels prepared for each color light and provided at positions that take chromatic aberration into account,
In a device that reads color information of an image by combining information obtained from pixels of each image sensor, the optical system is a non-telecentric optical system, and one of the image sensors for each color light is used as a reference image. When used as an element, the pixel pitch of the other image sensor is the pixel pitch of the reference image sensor multiplied by the ratio of the magnification in the other image sensor and the magnification in the reference image sensor. An image color information reading device characterized by: