JPS6326064A - Color image reader - Google Patents

Abstract

PURPOSE:To prevent color smear by inserting a lenticular plate in which the direction of arrangement of element lenses conforms with the direction of arrangement of photodetectors in the plate of incidence of light of a color image pickup element in which photodetectors are arranged one-dimensionally, and making the amount of blur due to the lenticular plate become larger than the pitch of each color filter. CONSTITUTION:Element lenses of a lenticular plate 6 are arranged in the same direction with the direction of arrangement of the photodetectors of a color image pickup element 7. In the case of an optical system in which the incident light 10 reflected from an original forms an image at a point P on the color image pickup element 7, when the lenticular plate 6 is inserted, a luminous flux 10 is divided to each element of the lenticular plate 6 and each small luminous flux forms an image at the point P and further is diverged to spread over an area A on the color image pickup element 7, and blur is caused at the image forming point P. The amount of blurring amount DELTAbecomes equal in primary approximation in each element lens of the lenticular plate 6. If the blurring amount DELTA is larger than the pitch (d) of each color filter, luminous flux emitted from the same point on the original enters photodetectors having color filters of three colors R, G, B simultaneously, and thereby the color smear is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a color image reading device, and particularly relates to a color image reading device in which a plurality of light-receiving elements are arranged in one dimension and color filters are sequentially arranged on each light-receiving element. The present invention relates to a color image reading device using a color image sensor formed in this manner.

(Prior Art) As shown in FIG. 6, a conventional color image sensor has light receiving elements arranged in a row with red (R) and H (
It is formed by installing color filters of G) and blue (B) at a pitch of d.

Since this color image sensor has a tj4 structure in which rectangular photosensitive pixels and color filters are arranged in the X direction, there is a problem in that color shift occurs in the X and Y directions.

In order to solve this problem, Japanese Patent Application Laid-Open No. 59-181568
A color image sensor as described in the publication was proposed. As shown in Fig. 7, this color image sensor has color filters of the same shape arranged on a parallelogram photosensitive image at a pitch d in the X direction, and in both the X and Y directions. It has the advantage that only 1 color shift occurs.

(Problems to be Solved by the Invention) However, the color imaging device described above has a problem in that color blur occurs in a direction perpendicular to the oblique side of the parallelogram-shaped color filter, that is, in the W direction. There was also the problem that moiré occurred due to the sampling of the color image sensor.

An object of the present invention is to provide a color image reading device that can prevent color shift with a simple and inexpensive configuration when the color image sensor shown in FIG. 6.7 is used. Another purpose is to prevent moire from occurring.

(Means and operations for solving the problem) In order to solve the above problem, the present invention arranges a plurality of light receiving elements in one dimension, and sequentially arranges each color filter on each light receiving element. In a color image reading device using a color image sensor, a lenticular plate is inserted into the light incident surface of the color image sensor, and the lenticular plate is aligned with the arrangement direction of the element lenses or the arrangement direction of the light receiving element. The feature is that color shift is prevented by making the amount of blur caused by the plate larger than the pitch of each color filter.

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

FIG. 2 is a schematic diagram of an embodiment of the present invention.

In the figure, 1 is a platen glass on which the original is placed; 2
is a light source that illuminates the original; 3 is a mirror that reflects light reflected from the original; 4 is a rod lens array; 5 is a mirror; 6
7 is a lenticular plate according to the present invention, and 7 is the one-dimensionally arranged color imaging device described above.

A perspective view of the lenticular plate 6 and the color image sensor 7 is shown in FIG. In this embodiment, as shown in the figure, the element lenses of the lenticular plate 6 are provided in the same direction as the arrangement direction of the light receiving elements of the color image sensor 7, and the distance l between the two satisfies the following formula. ing.

1≧d x 2x (r/P) −””Mountain here,
r is the radius of curvature of the element lens of the lenticular plate 6, P is the pitch of the element lens, and d is the pitch of each color filter of the color image sensor 7.

Next, the reason why this embodiment can prevent color fading of the color imaging cable 7 will be explained.

Assume now that there is an optical system that forms an image of the incident light beam 10 on a point P on the color image sensor 7, as shown in FIG. At this time, when the lenticular plate 6 is inserted as shown in FIG. 4, the light beam 10 is divided into each element of the lenticular plate 6, each small light beam focuses on a point P, and further diverges to form a color image sensor. 7. The area above is A. In other words, the light will disappear on the original imaging point P.

Assuming that this amount of deformation is Δ, the amount of deformation Δ is the same for any element lens of the lenticular plate 6 in a first-order approximation. Therefore, when calculating the amount of blur, it is sufficient to consider one element lens of the lenticular plate 6.

Therefore, focusing on FIG. 5, the distance between the lenticular plate 6 and the image plane 8 on the color imaging probe 7 is 1, the distance between the lenticular plate 6 and the imaging point P is 1, and the distance between the lenticular plate 6 and the imaging point P is 1, and the distance of the element lens is 1. When the curvature is rl, the pitch is Pl, and the refractive index of the lenticular number 6 is n, the following equation holds true.

1/l-1/l-=-(n-1)/rHere, if the refractive index n of the lenticular plate 6 is set to n=1.5, the above equation becomes as follows.

1/1-1/1-=-1/ (2r) Therefore, the following formula holds true.

1-=2 r 1/ (2r+shi...(2
) Furthermore, the displacement amount Δ is expressed by the following formula.

to-P1X (1-1-) /l -・・・・・・(3
) Substituting equation (2) into equation (3) yields the following.

Δ= l/ f2x (r/P) l ・・・・・・・
・(4) This amount of radiation △, which is thicker than the pitch d of each color filter shown in Fig. 1 or Fig. 6, is due to the light flux emitted from the same point on the document surface, or the R, G, B The light enters the light receiving element having three color filters at the same time, thereby preventing color shift of the color imaging element.

Therefore, the following conditions can be expressed as the following.

d≦1/ f2X Cr/P)1 Therefore, by making the interval l shown in Fig. 1 greater than or equal to ax2x(r/P), as shown in equation (1) above, color shift can be reduced. It can be prevented.

The above embodiment has been explained assuming that the color image sensor shown in FIG. 6 is used, but the color image sensor shown in FIG. If the distance I between the lenticular plate and the color image sensor is selected to satisfy the above conditions, color shift can be prevented.

However, in this case, the pitch d of each color filter in equation (1)
has the size shown in Figure 7 in the W direction, so
The following formula may be satisfied.

l≧2Xdsin (2X (r/P) where α is the angle formed between the arrangement direction and the hypotenuse of the photosensitive pixels.

Next, in the embodiment 1-, the distance l between the lenticular plate 6 and the color image sensor 7, the pitch P or the radius of curvature r of the element lenses of the lenticular plate 6,
By selecting a specific relationship, it is possible to eliminate moiré caused by sampling of a color image sensor. This will be explained below.

The response function of the lenticular plate 6 is expressed by the following equation with respect to the X direction, since if the element lens is considered to have no aberration, the light beam emitted from the - point spreads by Δ in the X direction.

sin (πΔf)/(πΔf) Here, [ is the spatial frequency.

The first zero-crossing frequency of this response function is 1/h, and if this is set to 1/2 of the sampling frequency, that is, the Nyquist frequency, the occurrence of moiré can be eliminated.

If we take into account the fact that it is an equilateral system, the Nyquist frequency is 1/(2d) (where d is the distance between the light receiving elements of the image pickup device), so the following equation should hold true.

1/Δ=1/(2d) By substituting the above equation (4) into this Δ, d is found as follows.

d= 1/ (4X (r/P)) Therefore, 1 = d X 4 x (r/P) =--15).

Therefore, as can be seen by comparing equation (1) with equation (5) above, if the distance between the lenticular plate and the color image sensor is doubled compared to when the equality holds in equation (1), , moiré can be removed. In other words,.

Moiré can be removed by making the brushing amount Δ twice the pitch of each color filter.

(Effects of the Invention) As is clear from the above description, the present invention achieves a similar effect.

(1) In the present invention, a lenticular plate element lens is arranged in the direction in which the light receiving elements of a color image sensor are arranged, and the amount of light image on the color image sensor is made larger than the pitch of each color filter. The light emitted from the lens enters at least three color filters to prevent color shift.

(2) Moiré can also be removed by making the brushing amount twice the pitch of each color filter.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main parts of the present invention, FIG. 2 is a schematic configuration diagram of a color image reading device to which the present invention is applied, and FIG. 3 is a point P
Fig. 4 is an explanatory diagram of the optical path when a lenticular plate is inserted into the optical system, and Fig. 5 is an explanatory diagram of the amount of displacement by one element lens of the lenticular plate. 6 and 7 are plan views showing examples of conventional color filters. 6 ・Lenticular plate, 7... Color filter,
10... Incident light flux agent Patent attorney Michito Hiraki 18 Figure 1 Figure 2 Mouth 3 Figure 2 Figure 4 Figure 6

Claims (3)

[Claims] (1) In a color image reading device using a color image sensor in which a plurality of light receiving elements are arranged one-dimensionally and each color filter is sequentially arranged on each light receiving element, the light incident surface of the color image sensor is A color image reading device characterized in that a lenticular plate is inserted in which the arrangement direction of the element lenses matches the arrangement direction of the light receiving elements, and the amount of blur caused by the lenticular plate is made larger than the pitch of each color filter. (2) The color image reading device according to claim 1, wherein the amount of blur caused by the lenticular plate is twice the pitch of each color filter. (3) The shape of the photosensitive pixel of the color image sensor is rectangular or parallelogram, and the color filter disposed thereon has the same shape. The color image reading device described in Section 1.