JPH0628451B2 - Solid-state imaging device - Google Patents

Description

The present invention relates to a solid-state image pickup device, and is preferably applied to a solid-state image pickup device using a solid-state image pickup device such as a CCD or a MOS.

B. Summary of the Invention The present invention provides a solid-state image pickup device in which an optical filter having a point diffusion function is inserted between solid-state image pickup chips having an image pickup lens system green chip, blue chip, and red chip,
The optical filter has frequency positions (f _s = 1 and f _v = 0),
By forming a trap straight line that passes through (1 ≦ f _s ≦ 2, f _v = 0), it is possible to easily obtain a solid-state imaging device that can effectively remove unnecessary carrier components without attenuating the baseband components. You can

C Conventional Technology A solid-state imaging device is, for example, a CCD (charge cou).
PLED device, MOS (metal ox)
By arranging solid-state image pickup devices such as a side semiconductor on a two-dimensional plan view in a grid pattern,
It has a configuration for discretely sampling an image captured from an image pickup lens system, and has been put to practical use as a suitable image pickup means when applied to a small color television camera or the like.

However, in principle, this type of solid-state image pickup device uses two primary color pixels arranged in a two-dimensionally regular image.
Since dimensional sampling is performed, the sampling output is a horizontal frequency f _x and a vertical frequency f _x that are determined based on the pitch between the image pickup elements forming each pixel.
Based on _y , it has a spatial frequency spectrum having a carrier frequency component at a predetermined frequency position with respect to the carrier frequency of the baseband.

Carrier components other than these baseband components may cause adverse effects such as moire and cross color phenomenon when the image is reproduced based on the sampling output if left as they are. It is desirable to remove the carrier component.

As a method for solving this problem, by utilizing the birefringence effect of the quartz plate, the light coming from the imaging lens system is optically separated into 7 or 8 based on the point diffusion function, An optical low-pass filter capable of forming traps in a spatial spectrum ram is Japanese Patent Application No.
No. 20503.

The optical filter disclosed in Japanese Patent Application No. 59-20503 is inserted between a solid-state imaging chip composed of a single chip and an imaging lens system as shown in FIG. The solid-state imaging device is configured to sequentially arrange the solid-state imaging device (e.g., CCD image sensor) in the horizontal direction (H direction) pitch _{P x} (e.g. 17 [μm]) interval in the vertical direction (V direction) pitch _P y ( = 13 [μm]), the CCD image sensors are arranged at intervals.

Here, in the pixel group configured by the CCD image sensor, the blue element 1B is provided adjacent to the green element 1G in the H direction, and the green element 2G is provided adjacent to the V element in the V direction. Further, the red element 2R is provided at a position adjacent to the green element 2G in the H direction and at a position adjacent to the blue element 1B in the V direction. Thus, a set of four elements 1G, 1B, 2G, and 2R is sequentially arranged in the H direction and the V direction, so that a two-dimensional solid-state image pickup device pattern is formed.

D. Problems to be Solved by the Invention When an image coming from an imaging lens system is sampled by the solid-state imaging device having such a configuration, the sampling output has a spatial frequency spectrum as shown in FIG. In FIG. 8, the horizontal axis and the vertical axis are P _y v / 2 based on the pixel pitches P _x and P _y in the H direction and the V direction, respectively.
It is shown as a value normalized by the formulas of π and P _x u / 2π, and an arrow R at each frequency position,
G and B indicate the phases of carrier components of red, green and blue signals, respectively.

As apparent from FIG. 8, the sampling output obtained from the solid-state imaging device of FIG. 7 arrangement, the frequency position in the H direction f _{x =} 0,1 / 2,1 ...... and V directions of the frequency position f _y
= 0, 1/4, 1/2, 3/4 ... Carrier components are present at frequency positions.

Of these, the baseband component occurs at the frequency position (f _x = 0, f _y = 0), while the carrier component that occurs at the other frequency positions is an unnecessary signal component, and depending on the object to be imaged. However, this may cause deterioration of the image quality of the image when this sampling output is reproduced.

For example, the carrier component generated around the position of the frequency position (f _x = 1 and f _y = 0) has a fine striped pattern consisting of black and white stripes extending in the vertical direction when the object to be imaged has a fine stripe pattern. Moire is generated in the reproduced image of the video output signal.

Further, the carrier component generated around the frequency position (f _x = 1/2, f _y = 0) causes a cross color phenomenon for green and magenta when the object to be imaged has a slightly rough vertical stripe.

Further, the carrier component generated around the frequency position (f _x = 0, f _y = 1) causes moire when the object to be imaged has a fine horizontal stripe.

Carrier component further generates a frequency position a position of _{(f x = 0, f y} = 1/2) as the center causes a flicker in a vertical edge.

Therefore, if it is possible to obtain a filter means capable of removing a carrier component generated at a frequency position other than the frequency position (f _x = 0, f _y = 0) without attenuating the base band component, the solid-state imaging device can be used. It is considered that the captured image can be reproduced with good reproducibility based on the obtained video signal.

The optical low-pass filter described in Japanese Patent Application No. 59-20503 is intended to solve such a problem by optical means, and the principle of its construction is as shown in FIG. Horizontal scanning direction (H direction) of the main surface including the axis
The angle formed with respect to each other changes by 45 ° 3
The crystal plates 11, 12, and 13 are laminated in this order and bonded to each other, and light obtained through the image pickup lens system is incident from the first crystal plate 11 side from a lower position orthogonal to the paper surface, and this incident light is incident. Light sequentially passes through the first crystal plate 11, the second crystal plate 12, and the third crystal plate 13 and is emitted to the solid-state imaging chip.

Here, in the first crystal plate 11, the main surface 14 included in the optical axis is H
The angle is set to + 45 ° with respect to the direction, the second crystal plate 12 is set to have an angle such that the main surface 15 coincides with the H direction, and the third crystal plate 1
3 is set so that the main surface 16 forms an angle of −45 ° with respect to the H direction.

By doing so, the ordinary ray o ₁ and the extraordinary ray e having a light amount that is ½ of that of the incident ray on the first quartz plate 11
₁ is obtained, and the extraordinary ray e ₁ is +45 with respect to the ordinary ray o ₁ .
It is separated by a distance corresponding to the thickness of the crystal plate 11 in the direction of °. Thus, two separated rays are obtained.

The ordinary ray o ₁ and the extraordinary ray e ₁ are respectively incident on the second crystal plate 12, and in the second crystal plate 12, the ordinary ray o ₂ and the extraordinary ray having a light amount of ½ of each incident light ray. e ₂ is obtained, and the extraordinary ray e ₂ is separated from the ordinary ray o ₂ in the H direction by a distance corresponding to the thickness of the quartz plate 12. Thus, four separated rays are obtained.

Further, the ordinary ray o ₂ and the extraordinary ray e ₂ are respectively incident on the third crystal plate 13, and in the third crystal plate 13, the ordinary ray o ₃ and the extraordinary ray having a light amount of ½ of each incident light ray. e ₃ is obtained, and the extraordinary ray e ₃ is separated from the ordinary ray o _{3 in the} direction of −45 ° by a distance corresponding to the thickness of the quartz plate 13. Thus, 8 separated rays are obtained.

In this way, the eight separated light beams from which the third crystal plate 13 is obtained are emitted to the solid-state imaging chip.

Here, the separation distance of the extraordinary rays e ₁ and e ₃ in the first and third quartz plates 11 and 13 is And the extraordinary ray e _{2 on} the second crystal plate 12
If the separation distance is selected as P _x , the three crystal plates 11, 1
As shown in FIG. 10, the eight separated light rays emitted through the different optical paths 2 and 13 are H with respect to the light rays o ₁ o ₂ o ₃ obtained at the incident position of the incident light from the object to be imaged. The light rays o ₁ e ₂ o ₃ and e ₁ o at positions separated by P _{x in the} direction.
₂ e ₃ are emitted redundantly. Also, the light beam o _{1 at the} reference position
The light rays o ₁ o ₂ o ₃ and o ₁ e ₂ o ₃ , e ₁ o in the directions of + 45 ° and −45 ° from o ₂ o ₃ to the H direction.
A substantially central position between ₂ e _3, respectively ray _e 1 _o 2 _{o 3}
And o ₁ o ₂ e ₃ are emitted. Further rays e ₁ o ₂ o ₃
And o ₁ o ₂ e _{3 at} a position separated by P _{x in the} H direction (that is, rays o ₁ e ₂ o ₃ , e ₁ o ₂ e ₃ and e ₁ e ₂
relationship as rays _e 1 _e 2 _{o 3} and _o 1 _e 2 _{e 3} from a substantially central position) emits between e ₃ is obtained.

By doing so, the frequency position in the H direction f _x = ...
It is possible to form a trap line having positive and negative slopes passing through -2, -1, 1, 2, ... And a trap line in the V direction passing through the frequency position f _x = 1/2. As a result, it is possible to obtain an optical filter capable of trapping the carrier component generated at other frequency positions while not giving harmful attenuation to the baseband component at the frequency position (f _x = 0, f _y = 0). You can

The present invention has been made in consideration of the above points, and is a practical trap for a solid-state imaging chip having three chips (that is, a red chip, a green chip, and a blue chip) based on the above-described principle configuration. An attempt is made to propose a solid-state imaging device having an effect.

E Means for Solving the Problems In order to solve the above problems, in the present invention, the ordinary ray o ₁ and the extraordinary ray e _{1 are} directed at + 45 ° with respect to the horizontal direction (H direction) of the solid-state imaging chip 21. And a second crystal plate 12 for separating the ordinary ray o ₂ and the extraordinary ray e ₂ in parallel with the horizontal scanning direction, and a normal direction in the direction of −45 ° with respect to the horizontal direction. Ray o ₃ and extraordinary ray e ₃
And a third crystal plate 13 for separating the second crystal plate 1
2 includes an optical filter in which a first crystal plate 11, a second crystal plate 12 and a third crystal plate 13 are laminated so that 2 is located in the middle, and the incident light is point-diffused to solid-state. In the solid-state imaging device that is adapted to enter the imaging chip 21, the solid-state imaging chip 21 includes a green chip 21G, a blue chip 21B, and a red chip 21R, and the optical filter is included in the spatial frequency spectrum of the sampling output. First and second trap straight lines L passing through the frequency position (f _s = 1 and f _v = 0) and having positive and negative slopes
(1), R (1) and frequency position (1 ≦ f _s ≦ 2, f _v
= 0) and a third trap straight line TR (2) extending along the vertical scanning direction (V direction) is formed.

F-action The optical filter has a point spread function, so that
Eight diffuse rays can be obtained based on the rays incident on the point, which allows positive and negative slopes through the frequency position (f _s = 1 and f _v = 0) on the spatial frequency spectrum of the sampling output. First and second trap straight lines L having
(1), R (1) can be formed and the frequency position (1
≦ f _s ≦ 2, f _v = 0) and a third trap straight line TR (2) extending along the vertical scanning direction is formed.

Thus frequency position _{(f s = 0, f v} = 0) without attenuating the baseband components in, it is possible to easily realize a solid-state imaging device formed by effectively remove unwanted carrier components.

G Embodiment One embodiment of the present invention will be described in detail below with reference to the drawings. In this case, the solid-state imaging chip 21 of the solid-state imaging device has three chips 21G, 21B, 2 corresponding to the three primary color signals G, B, R.
In principle, the light having 1R, which is taken in from the image pickup lens system is decomposed by the color separation means and is incident on the chips 21G, 21B, and 21R, similarly to a general three-plate solid-state image pickup device. As shown in FIG. 4, by stacking three chips on top of each other, a solid-state imaging chip 21 as a means for photoelectrically converting one color image by combining image sensors of each chip is configured. There is.

As shown in FIG. 5 (A), the green chips 21G are sequentially C-positioned at positions separated by pitches P _x in the H and V directions, respectively.
It has a configuration in which CD image sensors IMG are arranged in a grid pattern. Similarly, the blue chip 21B and the red chip 21R each have a configuration in which CCD image sensors IMB and IMR are sequentially arranged in a grid pattern, as shown in FIGS. 5B and 5C.

As shown in FIG. 6, these chips 21G, 21B and 21R have a positional relationship such that the image sensors IMB and IMR of the blue chip 21B and the red chip 21R are inserted between the image sensors IMG of the green chip 21G. It is relatively positioned to hold.

Further, the optical filter is inserted in a part of the optical system from the image pickup lens system to each chip of the solid-state image pickup chip 21, for example, at a position between the image pickup lens system and the color separation means, and the principle configuration is described above with reference to FIG. Similarly, a first crystal plate 11 having a main surface 14 at an angle position of + 45 ° with respect to the H direction and a second crystal plate 12 having a main surface 15 in the H direction.
And a third surface having a major surface 16 of −45 ° with respect to the H direction
Of the extraordinary crystal plates 13 and the moving distances P ₂ of the extraordinary rays e ₁ and e ₃ of the first and third crystal plates 11 and 13
But, Has been selected.

However, in the case of this embodiment, the separation distance P ₁ of the extraordinary ray e ₂ of the second crystal plate 12 is such that the image sensor pitch P _{x in the} H direction is P _x.
Against It is different in that it is selected.

Thus, the emitted light o obtained by the ordinary rays o ₁ , o ₂ and o ₃ respectively passing through the three quartz plates 11, 12 and 13
Considering the position where ₁ o ₂ o ₃ is obtained as a reference, the pitch between the light rays becomes the intervals _DH , _DH = P ₁ (3) in the H direction, as shown in FIG. On the other hand, the interval D _v D _v = 2P ₁ (4) in the vertical direction.

That is, the first ray o ₁ o ₂ o ₃ consisting of the ordinary ray o _{1 of} the quartz plate 11, the ordinary ray o ₂ of the quartz plate 12 and the ordinary ray o ₃ of the quartz plate 13 is obtained at the reference position.

The extraordinary ray e ₁ of the crystal plate 11 is separated by a separation distance P _{2 in the} direction of + 45 ° from the reference position.
By the ordinary ray o ₂ and ordinary ray o ₃ obtained from 2 and 13, a second ray e ₁ o ₂ o ₃ is obtained at a position separated from the reference position by 2D _H and D _v in the H and V directions. To be

Extraordinary ray e ₁ of crystal plate 11 and extraordinary ray e of crystal plate 12
_{When 2} emits as an ordinary ray o _{3 on the} crystal plate 13,
The third light ray e ₁ e ₂ o ₃ occurs at a position moved by _{DH in the} H direction from the position of the light ray e ₁ o ₂ o ₃ .

Extraordinary ray e ₁ of the crystal plate 11 and ordinary ray o _{2 of the} crystal plate 12
There When emitted as extraordinary ray _{e 3} of the quartz plate 13, light rays _e 1 _o 2 _{e 3} of the fourth occurs at a position apart rays _e 1 _o 2 _{o 3} from -45 ° direction separation distance _{P 2.} As a result, the light rays e ₁ o ₂ e ₃ are generated at a position moved by 4D _{H in the} H direction from the reference position.

Extraordinary ray e ₁ of crystal plate 11 and extraordinary ray e of crystal plate 12
₂ is emitted as an extraordinary ray e ₃ of the quartz plate 13, this fifth ray e ₁ e ₂ e ₃ is moved from the position of the ray e ₁ e ₂ o _{3 by} a separation distance P _{2 in the} direction of −45 °. Occur in. As a result, the light ray e ₁ e ₂ e ₃ is generated at a position further moved by _{DH in the} H direction from the light ray e ₁ o ₂ e ₃ .

Ordinary ray o ₁ of the crystal plate 11 and extraordinary ray e _{2 of the} crystal plate 12
Is emitted as the ordinary ray o ₃ of the crystal plate 13,
Ray o ₁ e ₂ o _{3 of} is generated at a position moved by _DH from the reference position on the line in the H direction passing through the reference position.

When ordinary rays _{o 2} of the ordinary ray _{o 1} and quartz plate 12 of the quartz plate 11 is separated as extraordinary ray _{e 3} of the quartz plate 13, light rays _o 1 _o 2 _{e 3} of the seventh, the reference position -45 Occurs at a position separated by a separation distance P _{2 in the} direction of °. As a result, the light ray o ₁ o ₂ e ₃ is 2D in the H direction and the V direction from the reference position.
It occurs at a position moved by _H and D _v .

Ordinary ray o ₁ of the crystal plate 11 and extraordinary ray e _{2 of the} crystal plate 12
Is separated as an extraordinary ray e ₃ of the quartz plate 13, this eighth ray o ₁ e ₂ e ₃ is separated by a separation distance P _{2 in the} direction of −45 ° from the position of the ray o ₁ e ₂ o _3. Occurs at the designated position. Thus, the light ray o ₁ e ₂ e ₃ becomes the light ray o ₁ o ₂ e.
It occurs at a position moved by _DH from _{3 in the} H direction.

In this way, eight light rays are diffused in the positional relationship shown in FIG. 1 based on the incident light rays that have entered the reference position from the object to be photographed and emitted from the crystal plate 13 with a light amount of ⅛. As shown in FIG. 2, the sampling output sent from the chip 21 (FIG. 4) exhibits trap characteristics for carrier components other than the baseband component included in the spatial frequency spectrum.

That is, the optical low-pass filter described above corresponds to the distribution of the spatial frequency spectrum included in the sampling output as shown in FIG. 2 in correspondence with FIG. 1), L (3) ... and trap straight lines ... R (-1), R (1), R (3).
A trap straight line TR (2) extending parallel to the V direction is generated.

Trap straight line …… L (-1), L (1), L (3) ……
Are frequency positions ... (-1, 0), (1 ,,
0), (3, 0) ... Parallel lines with a negative slope, and trap straight lines ... R (-1), R (1), R
(3) ... are frequency positions ... (-1, 0), (1,
0), (3, 0) ... and parallel lines having a positive gradient. Thus the trap straight line …… L (-1), L
(1), L (3) ..., and ... R (-1), R
(1), R (3) ... are extended so as to intersect with each other, so that a large number are symmetrically developed on the spatial frequency spectrum with the frequency position (f _s = 0, f _v = 0) as the center. Will form a diamond-shaped region.

The third trap straight line TR (2) has a frequency position (f _s
= 2, f _v = 0) and extend parallel to the V-axis, and thus expanded along the V-axis direction at a frequency f _s higher than the frequency position (f _s = 1, f _v = 0). Form a trap straight line that crosses the existing rhombus area.

As a result, the trap effect on the unnecessary carrier component included in the sampling output is, as shown in FIG. 3, the trap straight line L at the frequency position (f _s = 1) and f _v = 0.
Due to the double trap effect due to (1) and R (1), the carrier component at the frequency position can be sufficiently removed. In addition, the frequency position (f _s =
0, f _v = 1) with respect to the unnecessary carrier component, the trap lines L (1) and R (-1) intersect each other in the vicinity position, so that the trap effect is doubled and the carrier component is removed. It can be removed sufficiently.

In addition to this, the trap straight line TR (2) is formed in parallel with the V axis, so that the frequency position (f _s = 2, f _v =
0), (f _s = 2, f _v = 1/2), (f _s = 2, f _v =
Unnecessary carrier components generated in 1) are trapped straight TR
It can be effectively removed by (2).

Although the trap straight line TR (2) is generated at the position of the frequency position (f _s = 2, f _v = 0) in the above description, this frequency position may be expressed by the following equation 1 ≦ TR (2 ) ≦ 2 (5), it may be arbitrarily selected between f _s = 1 and 2. The position of the trap straight line TR (2) can be easily adjusted by adjusting the separation distance P ₁ of the extraordinary ray by the second crystal plate 12.

H Effect of the Invention As described above, according to the present invention, the frequency position (f _s = 0,
It is possible to easily obtain a solid-state imaging device that can effectively remove other unnecessary carrier components without attenuating the baseband component at f _v = 0).

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an optical filter according to the present invention, FIGS. 2 and 3 are characteristic curve diagrams showing the spatial frequency trap characteristics thereof, and FIGS. 4 to 6 are the configurations of solid-state imaging chips. 7 is a schematic diagram showing the configuration of a conventional solid-state imaging chip, FIG. 8 is a characteristic curve diagram showing the spatial frequency characteristic of the sampling output, and FIG. 9 is the principle configuration of an optical filter. FIG. 10 is a schematic diagram showing the positional relationship of light rays diffused by the point diffusion function of the optical filter shown in FIG. 11, 12, 13 ... Crystal plate, 21 ... Solid-state imaging chip, 21G, 21B, 21R ... Green, blue, red chip.

Claims (1)

[Claims] 1. A horizontal scanning direction of a solid-state imaging chip is +
A first crystal plate that separates an ordinary ray and an extraordinary ray in the direction of 45 °; a second crystal plate that separates an ordinary ray and an extraordinary ray in parallel with the horizontal scanning direction; At least a third crystal plate for separating an ordinary ray and an extraordinary ray in the direction of 45 °, and the first crystal plate and the second crystal so that the second crystal plate is located in the middle. A solid-state imaging device comprising an optical filter in which a plate and the third crystal plate are stacked and arranged, and the incident light is point-diffused by the optical filter to enter the solid-state imaging chip, the solid state imaging chip, the green chip has a blue chip and red chip, the optical filter passes a frequency position included in the spatial frequency spectrum of the sampled output _{(f s = 1, f v} = 0), and Positive and negative Forming a first and a second trap straight line having a slope and a third trap straight line extending along the vertical scanning direction through the frequency position (1 ≦ f _s ≦ 2, f _v = 0) A characteristic solid-state imaging device.