JPH0366262A - solid-state image sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a solid-state imaging device such as a CCD.

[Prior Art] Conventionally, solid-state image sensors have been made with a rectangular width as shown in FIG.
As shown in Fig. 2(b), pixels are arranged in a staggered manner to make the aperture size larger than the sampling pitch of the image sensor, as described in Japanese Patent Application Laid-Open No. 53-124013, or the aperture shape is shown in Fig. 2(c). It is made up of a diamond shape.

[Problems to be Solved by the Invention] However, since the conventional solid-state image sensor has a rectangular aperture, when the reading pitch (sampling pitch) is determined, the solid-state image sensor inevitably The aperture size is determined.

Moreover, in reality, due to manufacturing constraints, the opening is smaller than the desired size.

For this reason, the resolvable frequency range of the solid-state image sensor expands, resulting in the acquisition of information higher than the sampling frequency. For this reason, if the manually generated image information has a frequency higher than the frequency components that can be resolved by the image sensor, a beat will occur between the sampling frequency and the frequency components of the input image, resulting in moiré (from the sampling theorem). Orthogonal function transformation is known as a means of investigating what kind of frequency components a signal is composed of.This orthogonal transformation is used to concentrate energy distribution on low frequency components, edge and line information on high frequency components as a result of the transformation. It has characteristics such as the reflection of As this orthogonal transformation, a discrete Fourier transform is generally used. Let T be the sampling interval of a solid-state image sensor, and let its function be g (x), as shown in FIG. 3(a). When this is Fourier transformed, G(ν)=f (g (x)) f: Fourier transform symbol and expression. On the spatial frequency plane, Figure 3 (b
). On the other hand, when the aperture of the solid-state image sensor is shown in Fig. 2(a), the size of the aperture is a, and the distribution inside the image sensor is c(x), it appears as shown in Fig. 4(a). Ru. The Fourier transform of this is shown in Figure 4 (
b).

FIG. 5(a) shows an image S(x). Also, Figure 5 (b
) shows an image after sampling S (x) using the element shown in FIG. 4(a) and the sampling function shown in FIG. 3(a). The Fourier transformed version of this is shown in Figure 6(a).
shall be. The characteristics shown in FIG. 6(a) are obtained when sampling is performed when the size of the aperture of the element and the sampling interval are equal.

However, in reality, since the aperture size of the element becomes smaller than the sampling pitch, overlapping occurs as shown in FIG. 6(b), causing moiré. Figure 7(a) shows the conventional 40
The plan view of the 0dpi element, FIG. 7(b) shows the waveform after Fourier transformation of the aperture of this element, and FIG. 7(C) shows the waveform of the 400dpi element.
The MTF projection line diagram at the time of pi reading is shown. Figure 7(e)
161 ines/mm for adjacent pixels in the main scanning direction
It can be seen that MTF values exist in the above locations.

This will overlap.

Therefore, as a means of making the aperture size of the elements larger than the sampling interval, there is a method of arranging the elements in a staggered manner as shown in Figure 2(b) or arranging diamond-shaped apertures as shown in Figure 2(c). It is being done.

However, arranging them in a staggered manner as shown in FIG. 2(b) is equivalent to having two line sensors, and it is necessary to perform control to align the upper and lower rows in the sub-scanning direction. Further, in the case of a diamond-shaped aperture as shown in FIG. 2(c), the aperture is large in one diagonal direction, but the aperture is small in the ground diagonal direction, so that moiré removal is effective only in one direction.

[Means for Solving the Problems] In the present invention, moire can be effectively removed by making the aperture shape of the solid-state image sensor larger than the sampling interval and by making the aperture shapes of adjacent elements different. It is something that

[Example] FIG. 1 shows the shape of the aperture of the solid-state image sensing device of the present invention. P indicates the sampling interval, and a indicates the size of the aperture of the device.

FIG. 8 shows a digital reading device using a solid-state image sensor according to the present invention. When a reading start button (not shown) is pressed, the illumination system 3 illuminates the original 2 on the original platen glass 1, the reading unit 4 moves in the direction of the arrow, and the solid-state image sensor 6 is scanned through the imaging lens 5. Information is transmitted to.

The reading ability at this time is 400 dpi (dotper
1 nch), the size of the solid-state image sensor is shown in Figure 9 (
As shown in a-1) and (a-2), the longest length in the main scanning direction is 1.
00 μm, and the size in the sub-scanning direction is 60 μm.

Figure 9 (b-1
) and (b-2). This figure represents the spatial frequency plane and the value M T F after Fourier transform in the range of ±401 ines/mm.
er Function) is shown.

Figures 9 (c-1) and (c-2) show MTF diagrams when reading at 400 dpi.

As a result, as shown in the figure, the resolvable spatial frequency characteristics of the reading element can be suppressed within the range of ±161 ines/mm. It should be noted that FIG. 10 is a diagram showing a second embodiment of the present invention, and it goes without saying that a plane opening may be configured in this manner.

[Effects of the Invention] As explained above, according to the present invention, one of the solid-state image sensors
It is now possible to make the aperture shape of the element larger than the sampling pitch, and it is possible to make the aperture shape of the element larger than the sampling pitch.
It becomes possible to remove moiré fringes that occur during reading.

Furthermore, by increasing the aperture of one element, the light-receiving area becomes larger than before, making it possible to reduce the amount of light, and also having the effect of suppressing problems such as heat treatment.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of the aperture configuration of a solid-state image sensor of the present invention, Figures 2 (a) to (C) are diagrams showing an example of the aperture configuration of a conventional solid-state image sensor, and Figure 3 (a) is a sampling diagram. Figure 3(b) is a diagram of the output function of a spacer image sensor, Figure 3(b) is a diagram after Fourier transformation of Figure 3(a), Figure 4(a) is an output function diagram of an element with aperture size a, Figure 4 (b) is a diagram after Fourier transformation of Figure 4 (a), Figure 5 (a) is a diagram showing image S (x), Figure 5 (b)
is a diagram when S (x) is sampled with the element in Figure 4 (a) using the sampling function in Figure 3 (a), Figure 6 (a) is a diagram obtained by Fourier transforming Figure 5 (b), Fig. 6(b) is a diagram showing the drawbacks of the conventional device, Fig. 7(a) is a diagram showing an example of the planar aperture of the conventional element, Fig. 7(b) is its MTF contour diagram, and Fig. 7(C) is an MTF contour diagram during reading scanning; FIG. 8 is a diagram showing an example of a reading scanning system; FIGS. Figures (b-1) and (b-2) are MTF contour diagrams, and Figures 9 (c-1) and (c-2) are MTF contour diagrams during scanning. FIG. 10 is a diagram showing a second embodiment of the present invention. α〉P JP-A-3 66262 (4) Rihe (λ-7) CCD type bar (a-2) Itlt/7u

Claims (2)

[Claims] (1) In solid-state imaging devices such as CCD sensors that convert optical information into electrical signals, the aperture length in the main scanning direction of the aperture of a unit pixel is larger than the sampling interval in the main scanning direction of the sensor, and the apertures of adjacent pixels A solid-state image sensor characterized by different shapes. (2) The solid-state imaging device according to claim (1), wherein the unevenness of the side surfaces of adjacent pixels are made to match.