JPS62142460A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To suppress a crosstalk from an adjacent picture element and to attain high resolution by arranging an interference filter having a prescribed spectral transmittivity between an original face and a photoelectric transducer array. CONSTITUTION:The interference filter is provided between the photoelectric transducer array and the original. A multi-layer thin film filter 14 transmits a light with a small incident angle in the photoelectric transducer 8 among the light reflected from the original face, reflects the light having a large incident angle and selects the light not almost transmitted. The original 1 runs relatively on the transmission spacer 9 of a solid-state image pickup device in a subscanning direction at a position apart by a prescribed distance L from the photoelectric transducer 8. The luminous flux 10 from the light source 15 is made incident in the original 1 from the back side of the transparent base 6 through a slit opening 11, a part 12 of the reflected luminous flux from the original 1 is received by the photoelectric transducer and scanned electronically. In this case, the oblique incident component such as the reflected luminous flux 12A is reflected by the multi-layer film filter 14, the crosstalk is suppressed and excellent reading with the high resolution is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a solid-state imaging device in a photoelectric conversion system such as a factor (IJ).

2. Description of the Related Art Recently, a type of linear INO-2 hepurge sensor called a contact image sensor has been developed as a photoelectric conversion means of the same magnification type, and has been put to practical use in facsimile reading units and the like. The structure of a conventional example of the reading section is shown in FIG. In FIG. 5, ■ is a document, 2 is a linear light source such as a fluorescent lamp, 3 is a rod lens array, 4 is a linear image sensor, document 1 is illuminated by light source 2, and document 1 is illuminated by an arrow X.
An erect equal-magnification image of the linear portion shown by is formed on the aperture array 4A of the image sensor 4 and electronically scanned. The direction of this arrow X is the main scanning direction, and the original 1 is fed in the sub-scanning direction Y that is perpendicular to this direction, and the entire surface of the original is read.

Here, the rod lens array 3 includes a large number of rod lenses 3.
A is arranged regularly and accurately, and the optical system can be made much smaller than a normal imaging optical system using a spherical lens to obtain the same Royal life-size image. A major feature of the imaging optical device using the rod lens array 3 is that it can be significantly miniaturized. However, the rod lens array 3 has the disadvantage that it is very expensive compared to an imaging optical system using a spherical lens, and the entire optical system using the image sensor described above uses a 3-hoen rod lens array 3. Because of this, there was a limit to miniaturization.

As a further miniaturization of the same size reading sensor,
A solid state in which a photoelectric conversion material made of a translucent photoconductive thin film is placed very close to the document surface, the document surface is illuminated from behind, and the reflected light is directly received by the photoelectric conversion material without using a lens system. An imaging device is proposed in Japanese Patent Publication No. 47-3482. Thereafter, as shown in FIG. 6, a solid-state imaging device 5 is formed, in which a photoelectric conversion element 8 is arranged on a transparent substrate 6 with a non-light-transmitting layer 7 interposed therebetween, and a light-transmitting spacer 9 is further provided thereon. Proposed. In the same figure, (a
) is a cross-sectional view in the main scanning direction, and width ) is a cross-sectional view in the sub-scanning direction.

In this solid-state imaging device 5, an original 1 is held by a light-transmitting spacer 9 at a constant minute distance from the photoelectric conversion element 8, and an illumination light beam 10 from an appropriate light source is directed to the back surface of the photoelectric conversion element 8. It enters the original 1 from the side through the aperture 11 formed in the non-transparent layer 7, and a part of the reflected light beam 12 enters the element 8.
The light is received and the document is read.

Problems to be Solved by the Invention However, according to this configuration, as shown in FIG. Although the reflected light 12A is incident on the conversion element 8A, other reflected light 12A as shown by the broken line is incident on the adjacent photoelectric conversion elements 8B and 8C, resulting in so-called crosstalk. This crosstalk has caused a problem in that the resolution is reduced.

As a method to solve the above problem, as shown in FIG. By arranging the body 13, it is possible to block 1.2 A of reflected light from other pixels. However, there are also problems with the method using such a light shielding body 13. That is, in FIG. 7, the reflected light 12A from one pixel is blocked and does not enter the photoelectric conversion element from the pixel IA on the original surface to the photoelectric conversion element 8D, which is 3 pitches away from the pixel IA on the original surface. 1.2B of reflected light from pixels or 5 pixels separated by 3 or more pitches like IB enters the photoelectric conversion element through the slit of the light shield 13, causing crosstalk. Furthermore, a new manufacturing problem occurs in that the positional relationship between the photoelectric conversion element and the slit differs from pixel to pixel due to the difference between the error in the slit spacing of the light shielding body and the error in the spacing of the photoelectric conversion element.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a fully contact solid-state imaging device that suppresses crosstalk from adjacent pixels, provides high resolution, and is easy to manufacture. shall be.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses a light source that does not have at least a component on the short wavelength side as a light source for illuminating the document surface.
A light source having a predetermined spectral distribution characteristic is used, and an interference filter having a predetermined spectral transmittance characteristic that does not transmit at least light on the long wavelength side is arranged between the document surface and the photoelectric conversion element array. It is something that

Effects of the present invention With the above configuration, the interference filter transmits light having a wavelength that overlaps with the transmission wavelength band of the filter for light having a small incident angle (incident perpendicularly to the filter surface); For light with a large angle of incidence, the light transmission wavelength band of the filter shifts to the shorter wavelength side, so that almost no light of the wavelength is transmitted, and therefore, light with a large angle of incidence is not transmitted.

As a result, among the light reflected from the document surface, the light that is incident at right angles to the photoelectric conversion element passes through the filter and reaches the photoelectric conversion element, but most of the light that is incident in the oblique direction is reflected by the filter. As a result, crosstalk is suppressed, high resolution can be obtained, and the aperture of the photoelectric conversion element in the main scanning direction can be made large.

EXAMPLES The present invention will be described in detail below. FIG. 1 shows an embodiment of the present invention, in which (a) is a sectional view in the main scanning direction, and (b) is a sectional view in the main scanning direction.
) is a sectional view in the sub-scanning direction. In the figure, the solid-state imaging device 5 according to the present invention includes a transparent substrate 6 and an opaque layer 7 on the upper surface of the transparent substrate 6 in the main scanning direction (X direction).
A photoelectric conversion element row consisting of a large number of photoelectric conversion elements 8 arranged at appropriate intervals for seven pages, and a surface on which the original 1 is brought into close contact and moves in the sub-scanning direction (Y direction), and the photoelectric conversion elements A light-transmitting spacer 9 for protecting the photoelectric conversion element 8 and an interference filter, that is, a multilayer thin film filter 14 interposed between the light-transmitting spacer 9 and the photoelectric conversion element 8, are stacked and integrated. A slit opening 11 having a width comparable to the reading width W□ in the sub-scanning direction is formed in the non-transparent layer 7 along the photoelectric conversion element array. Below the transparent substrate 6, Ts are arranged discontinuously in a linear manner in the main scanning direction.
An ED (light emitting diode) light source 15 is arranged, and a radiant beam 10 from the light source 15 irradiates the document 1 with a width of W through a slit opening 11 . As the light source 2, one having predetermined spectral distribution characteristics related to the characteristics of the multilayer thin film filter 14 is used, the details of which will be described later.

The multilayer thin film filter 14 is deposited on the side of the light-transmitting spacer 9 facing the photoelectric conversion element array. The multilayer thin film filter 14 used here filters out the light reflected from the document surface as shown in FIG.
1) As shown in Figure 1 (al), the light that enters the photoelectric conversion element 8 at a small angle of incidence is transmitted, but as shown in Figure 1 (al), from one pixel IA to other photoelectric conversion elements as shown by the broken line. A filter is selected that has characteristics that reflect light that enters at a large angle of incidence and hardly transmit it.A filter with such characteristics is determined in relation to the spectral distribution characteristics of the light source.

For example, an LED with an energy peak in the wavelength range consisting of
With respect to the light source, the angle of incidence θ=08(
a predetermined transmission limit wavelength λ at which the spectral transmittance characteristic with respect to normal incidence is longer than the shortest wavelength of light from the light source; A low pass filter with . In this low-pass filter, the spectral transmittance characteristic when the incident angle of light is θ is the above-mentioned λ.

is λ toward the short wavelength side. It is shifted by −λθ and satisfies the well-known relational expression. Here, n is the average refractive index of the multilayer thin film filter 14. In this embodiment, the light source 10 is a GaP-based LED light source with a main wavelength λm, = 57 Qmya and a half-value width Δλ9 = 7' 1/2 = 20 nm, and the multilayer thin film filter 4 is Chita 7 (
IV) (T + 02, nt gradient 2.2) and silicon dioxide (SI Os, nx #1.46) are used to form a multilayer film alternately. The average refractive index n of this filter 4 is n, 10n.

nm □-1,8. λ in Figure 2. -602nm, n==1.8
The spectral transmittance characteristics of the multilayer thin film filter 4 with respect to the incident angle θ of light (solid line) and the spectral energy characteristics of the LED light source (dashed line) are shown as models for simplicity. In the figure, a portion where the spectral characteristics of the light source and the multilayer thin film filter intersect (for example, △ABC
) corresponds to the amount of light that passes through the multilayer thin film filter 14 at an incident angle θ (for example, θ = 40°), and this amount of light does not change between θ = 0 and 27°, but decreases when the angle is higher than that. 1/4 at θ=400 compared to when θ=0°
Below, at θ=45°, it is 1/10 or less, and at θ=50°, it is almost O (almost no transmission).
becomes. Therefore, by combining the light source and the multilayer thin film filter, it is possible to prevent the transmission of light greater than the angle of incidence, and the limit of the angle of incidence that can be transmitted is determined by adjusting the spectral characteristics of the light source or filter as appropriate. By selecting
It can be set to any desired value.

The combination of the light source 15 and the interference filter 14 for blocking the transmission of light exceeding the incident angle is an LED YG light source with a dominant wavelength in the yellow-green band and a low-pass filter as shown in FIG. It is not limited to the combination with , and various changes are possible. For example, as shown in Figure 3(a), a YG light source is used in combination with a bandpass filter whose transmission wavelength band is the same as the spectral distribution characteristic of the light source, but whose transmission wavelength band extends to the longer wavelength side by several tens of nanometers. The above effect can also be obtained. Furthermore, the combination of a G light source using a fluorescent tube with a dominant wavelength in the edge band and a band-pass filter as shown in FIG. 3(1)), and the combination of a G light source and a low-pass filter as shown in FIG. 3(e) can also be used. , the above effect can be obtained by selecting the wavelength inclination width and the transmission limit wavelength of the filter so as not to transmit the energy on the long wavelength side adjacent to the main wave 11'' long band of the G light source.Furthermore, as shown in FIG. Combination of mountain red band LED light source and bandpass filter, 3rd
The above effect can also be obtained by the combination of the R light source and the low-pass filter shown in FIG. In short, by combining a light source with a spectral distribution characteristic that does not include at least a component on the short wavelength side and an interference filter with a spectral transmittance characteristic that does not transmit at least light on the long wavelength side, the light enters the interference filter perpendicularly and at a small incident angle. It is possible to allow light to pass through, but not to allow light that is incident at an angle greater than the inclination angle to pass through.

Furthermore, in FIG. 1, the aperture size W of each photoelectric conversion element 8 in the main scanning direction is selected in consideration of the characteristics of the light source 15 and filter 14 so as to suppress crosstalk. That is, the reflected light 12A from one pixel on the document surface is incident on photoelectric conversion elements other than the photoelectric conversion element 8A facing one pixel at a large incident angle, for example, 54 degrees or more as shown in the figure. has been selected. For this reason, for example, the reflected light 12A from the pixel IA has an incident angle of 50° or more with respect to the photoelectric conversion element adjacent to the photoelectric conversion element 8A, so it is reflected without passing through the multilayer thin film filter 14.
It becomes possible to sufficiently suppress crosstalk. 1st
In the figure, the incident angle 19(7) value shown in the figure is W”
P/4 = 0.03 wn, T.

= O408 skin, whereas λma
x ” 570 nm, △λ1/2-2-20n λ
.

= 602 nm and n = 1.8, an imaging system with suppressed crosstalk was realized.

Note that when a light source and filter having the characteristics shown in FIG. 2 are used, it is possible to further increase the aperture size W of the photoelectric conversion element in the main scanning direction, and as shown in FIG.
Even if the maximum Wm is x=2W (=P/2)=0.06m, crosstalk can be suppressed. At the same time, the aperture size W of the photoelectric conversion element 8 in the sub-scanning direction. By widening the spacer, a highly sensitive photoelectric conversion element output can be obtained, and the aperture area of the photoelectric conversion element is expanded.
It is possible to prevent resolution degradation and fluctuations in the amount of received light due to disturbances in reflected light from the original 1 caused by scratches on the third page.

゛ At this time, as described above, the irradiation width of the original 1 from the light source in the sub-scanning direction is limited by the non-transparent layer 7 to the reading width W1.
Therefore, even if Wo>Wl, the resolution in the sub-scanning direction is not reduced.

Next, the operation will be explained. In FIG. 1, a document 1 relatively travels on a transparent spacer 9 of a solid-state imaging device, and thus travels in a sub-scanning direction (Y direction) at a position a certain distance away from a photoelectric conversion element 8. At this time, as shown in FIG. 2B, the light beam 10 from the light source 15 is incident on the original 1 through the slit opening 11 from the back side of the transparent substrate 6. A portion 12 of the reflected light beam from the original 1 is received by a photoelectric conversion element and electronically scanned. At this time, the obliquely incident component such as the reflected light beam 12A is reflected by the multilayer thin film filter 14 as described above, crosstalk is suppressed, and good reading with high resolution is performed.

In the above embodiments, the non-light-transmitting layer 7 is provided between the transparent substrate 6 and the photoelectric conversion element array, and only the incident light from the original is incident on the photoelectric conversion elements. The present invention is not limited to this type, and the light beam for illuminating the original passes through the photoelectric conversion element 8 and illuminates the original surface,
The present invention can also be applied to a solid-state imaging device configured to receive reflected light from a document.

Furthermore, in the above embodiment, the case in which a thin film type photoelectric conversion element array formed on a transparent substrate was used was explained in detail.
It goes without saying that the present invention is not limited to this case, and that it is also possible to use a CCD type image sensor or an α-8i type element. Particularly in the case of a CCD type image sensor, it is possible to increase the aperture size in the main scanning direction while suppressing crosstalk, so it is also possible to improve the signal/noise ratio (S/N ratio).

Effects of the Invention As is clear from the above description, the present invention combines the property of an interference filter that the transmission wavelength band changes depending on the incident angle of light and the spectral energy distribution property of the illumination light source.
By providing the interference filter between the document surface and the photoelectric conversion element, among the reflected light from the document surface 15', the incident angle that is vertical or near vertical is incident on the photoelectric conversion element through the interference filter. It is possible to reflect objects with a large angle of incidence and prevent them from entering the photoelectric conversion element, and by suppressing crosstalk, it is possible to improve the front and back sensitivity distribution, allowing for good reading with high resolution. It has the effect of becoming

Further, while suppressing crosstalk, it is possible to increase the aperture width in the column direction of the photoelectric conversion element array to approximately 1/2 of the photoelectric conversion element spacing (P), and highly sensitive photoelectric conversion element output can be obtained.

Furthermore, since the interference filter itself has an incident angle selection characteristic, a desired effect can be easily achieved without requiring special positional accuracy, and a highly reliable imaging device can be provided.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, in which (a) is a cross-sectional view in the main scanning direction, (b) is a cross-sectional view in the sub-scanning direction, and FIG. 2 is a multilayer thin film filter used in the above embodiment. and a graph showing the spectral characteristics of the light source, No. 311. L to e are graphs showing the spectral characteristics of the multilayer thin film filter and light source that can be used in the present invention, Figure 4 is a cross-sectional view in the main scanning direction showing another embodiment of the present invention, and Figure 5 is a conventional close-up image. A schematic perspective view of the sensor, FIG. 6 shows an example of a conventional solid-state imaging device, and (a
) is a cross-sectional view in the main scanning direction, (1)) is a cross-sectional view in the sub-scanning direction, and Figure 7 is a cross-sectional view in the main scanning direction of a solid-state imaging device that is considered to be able to solve the problems of the device shown in Figure 6. FIG. ]...Original 5...Solid-state imaging device 6...Transparent substrate 7...Non-transparent layer 8...Photoelectric conversion element 9...Transparent spacer 14...Multilayer thin film filter 15...・Name of Hikaru Gen's agent Patent attorney Toshio Nakao and one other person, 'C1
[2 f Kangana 5 Gotomine shoulder base 1 (b) 8・、Kyudenwoshugo 5 Word 3 Figure:,':sFigure'Pc) (J 500 600
700 Figure 4 Figure 5 A Figure 6 (a) Cb)

Claims (1)

[Claims] A light source having a predetermined spectral distribution characteristic that illuminates the document surface, a photoelectric conversion element array disposed close to the document surface and facing each other in the main scanning direction, and intervening between the photoelectric conversion element array and the document surface. and an interference filter having predetermined spectral transmittance characteristics, and the spectral distribution characteristics of the light source and the spectral transmittance characteristics of the interference filter are such that the interference filter mainly absorbs the incident light from the reflected light from the document surface. A solid-state imaging device characterized in that it is selected to transmit objects with small corners.