JPS63156353A - Original reader - Google Patents

Abstract

PURPOSE:To make it possible to read an original having a plurality of colors at high resolution and a high speed, by laminating two photoconductive layers having the different optical forbidden band widths by commonly using a light transmitting common electrode, changing a voltage that is applied to the common electrode, and operating a photocurrent, in which a spectral sensitivity characteristic is changed in correspondence with the applied voltage. CONSTITUTION:As a first photoconductive layer 14, e.g., antimony sulfide is deposited. Electrodes 13 and 15 are formed on both surfaces in the direction of a thickness. Thus a sandwich type optoelectric transducer element 19 is formed. Then, as a second photoconductive layer 16, zinc solenoid is used, and a sandwich type optoelectric transducer element 20 is formed by the same way described above. The photoconductive layers 14 and 16 are laminated by commonly using the light transmitting common electrode 15. When light 18 is inputted from the side of a discrete electrode 17 on the second photoconductive layer 16, the second photoconductive layer 16 works as a filter. Therefore, a photocurrent indicates spectrums approximately close to the tristimulus values of a CIE. All pieces of color information (hue, saturation and lightness) can be accurately detected by the operation based on the photocurrent.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application Akira Honji relates to document reading devices used in facsimiles, image scanners, etc., and in particular, the ability to read multiple colors without using color filters or switching the color of the illumination light source. The present invention relates to a novel document reading device that reads documents with high resolution and high speed.

BACKGROUND OF THE INVENTION In recent years, close-contact image sensors for use in document reading devices such as facsimiles and image scanners have been actively developed. A contact-type image sensor is a photoelectric conversion device that uses a photoelectric conversion element with the same width as the document and reads the document by placing it in almost close contact with the document. Conventional integrated circuit image sensors such as CCDs (charge-coupled devices) require a precise reduction optical system that reduces the original image of the document and forms the image on the image sensor, but contact image sensors Since no optical system is required, the document reading device can be significantly reduced in size and weight.

The photoelectric conversion elements of contact type image sensors that are currently in practical use are basically, for example! It is constructed as a Brehner type shown in FIG. 1S9 or a so-called sandwich type shown in FIG. These photoelectric conversion elements are electrically insulating substrate 1
, photoconductor MJ2, metal electrode 3.4.5 and transparent conductor ff16. Electrodes 3, 4: 5.
When a DC voltage is applied to 6rffl and the photoconductor layer 2 is irradiated with light 7, carriers (Ti atoms, holes) generated by the light 7 move, and a photocurrent is generated between the electrodes 3, 4 and 5 and 6. flows, and light is detected by measuring this flow.

Such a photoelectric conversion element only performs charge conversion according to the spectral sensitivity of the photoconductor layer 2, and when used in a document reading device such as a facsimile or image scanner, it is used to distinguish the color of the document. It is not possible. Currently, many colors are used in office documents and the like, and there is a great demand for reading documents in multiple colors.

Therefore, in order to detect the color of the original, conventionally the ninth
A method of attaching a color filter to a pixel using a photoelectric conversion element as shown in FIG. 1 or FIG. 10, a method of switching the color of an illumination light source for each scan, and the like are used.

Problems to be Solved by the Invention However, when red, green, and blue color filters are attached to each pixel, the pixel density decreases to, for example, 1/3, and when the color of the illumination light source is switched, the reading speed decreases. In addition, there were problems in that the characteristics of the original 8S reader deteriorated, such as the need for a 3FII class light source, which forced the device to be larger.

The present invention has been made in view of the above points, and provides a document reading device that reads documents of multiple colors at high resolution and high speed without using color filters or switching the color of the illumination light source. The purpose is to

Means for Solving the Problems The present invention provides a first individual electrode, a first photoconductor layer, a translucent common electrode, and a tJS1 photoconductor layer having physical-optical properties on an electrically insulating substrate. Different second photoconductor layers and first individual electrodes are stacked in this order N! A first photoelectric conversion device comprising a first individual electrode, a first photoconductor layer, and a light-transmitting common electrode; Such a photoelectric conversion device including a second photoelectric conversion element constituted by two photoconductor layers and the second individual electrode, wherein at least 2f! Applying different voltages of and thus obtained? A document reading device characterized in that the optical condition of incident light is determined by detecting and arithmetic processing each photocurrent from a tS1 photoelectric conversion element and a second photoelectric conversion element. .

Function According to the present invention, at least two different voltages are applied to the light-transmitting common electrode, and each light is changed in accordance with the voltage applied to the first photoelectric conversion element and the $2 photoelectric conversion element. Detects current and processes it to identify the color of light.

EXAMPLES First, the present invention will be explained in detail. An example of the spectral sensitivity and light absorption coefficient of photocurrent generally exhibited by a photoconductor layer is shown in Figure 2, Line No. 1. It is shown in No.2. Wavelength input O with maximum spectral sensitivity 11
At closer wavelengths, the spectral sensitivity decreases in response to the optical absorption coefficient. That is, since light is no longer absorbed, the spectral sensitivity of photocurrent decreases. However, in the region where the wavelength of light is shorter than 0, the optical absorption coefficient is a dot-dashed line! As shown by 2, the photocurrent continues to decrease even though it is increasing.

This is because as the light absorption coefficient increases, light is absorbed closer to the surface of the photoconductor layer on the light incident side, and the lifetime of the generated carriers (electrons, genuine tags) is shortened due to recombination at surface levels. It is thought that this is because it becomes dark. Therefore, if the carriers generated near the light incident surface are moved from the light incident surface to the inside of the photoconductor layer so as not to be recombined by the surface states, the spectral sensitivity of the photocurrent will be lower than the wavelength λ0. It is thought that the decrease in the margin on the shorter wavelength side becomes smaller.

Based on this -V assumption, the present invention is based on a sandwich-type light film having two different spectral sensitivities, each having a photoconductor layer and electrodes disposed on both sides of the photoconductor layer in the thickness direction. In a structure in which +1 conversion elements are stacked using a common light-transmitting electrode, the voltage applied to the common electrode is changed, and each photocurrent whose spectral sensitivity characteristics change in response to the applied voltage is calculated. The color of incident light is classified by fJ.

In addition, several inventions have already been proposed for simply stacking photoconductor layers with different spectral sensitivities (
For example, JP-A-56-27561, JP-A-57-841
85, Japanese Patent Publication No. 6O-160660). However, in order to accurately determine color information (hue, saturation, brightness),
For example, CIE tristimulus values are required, and generally three types of independent photocurrents with different spectral sensitivities are required. For this reason, if only 2/ll photoconductor layers are laminated, it is possible to distinguish a single spectral color, but it is not possible to distinguish the color of a complex document with mixed spectra9. It is conceivable to laminate 3 layers, but if a 3-layer laminate structure is constructed, the number of manufacturing steps increases, and 1! Pole wiring becomes extremely complicated and impractical. Accurately determining color information using a simple photoelectric conversion element structure without using color filters or without switching the color of the illumination light source focuses on modulating spectral sensitivity using an electric field, as described later. This becomes possible for the first time with the present invention.

The present invention will be specifically described below based on examples.

FIG. 3 shows V and document reading device r! of an embodiment of the present invention. 121 is a block diagram illustrating the configuration of 121. FIG. The photoelectric conversion element 11, which is a photoelectric conversion device having a configuration as described below and which reads the original 22, is configured by stacking photoelectric conversion elements 19 and 20, which are first and second photoelectric conversion elements. A DC voltage from the DC layer 1fi23 is applied to each photoelectric conversion element 19, 20, respectively. The applied voltage from the DC'yl source 23 is turned on/off by the switching means SW1.5W2.
It is controlled to be cut off. This switching means sW1. sW2
A current detection means 24 is provided between the photoelectric conversion elements 19 and 20.
．． 25 is interposed to detect the current flowing through the photoelectric conversion elements 19 and 20.

The operations of the switching means SWI, SW2 and the DC power supply 23 are controlled by a control section 26, and the current values detected by the current detection means 24, 25 are read by the control section 26. That is, the control unit 26 detects the optical image of the original 22. The detected results are output to the display device 27 or the printing device 28.

FIG. 1 shows a cross section of a photoelectric conversion element 11, which is a photoelectric conversion device used in the document reading device 21 of the present embodiment described above. The charging conversion cable 11 of this embodiment includes an electrically insulating substrate 12, an fjS1 individual electrode 13, a first photoconductor M14,
It is formed by laminating a light-transmitting common electrode 15, a second photoconductor layer 16, and a light-transmitting second individual electrode 17 in this order. The light 18 is assumed to be incident from the second individual electrode 17 side,
The optical forbidden band width of the second photoconductor layer 16 is configured to be larger than the optical forbidden band width of the first photoconductor layer 14 .

The operating principle of this embodiment is as follows:
A detailed explanation will be given based on the spectral sensitivity when each photoconductor layer 16 is used alone. For example, antimony sulfide (Sb2Ss) is used as the Pt51 photoconductor layer 14. Antimony sulfide 5b2S can be easily produced uniformly over a large area by vapor deposition technology.

A sandwich-type photoelectric conversion element 19 was prepared by depositing alethimony sulfide S[1,S, to a thickness of about 1 μm (up to) to form electric fi 13, 15 on both surfaces in the thickness direction, and by varying the applied voltage. Figure 4 shows the spectral sensitivity of photocurrent when

The photocurrent 11 when the applied voltage v=vi (r, say 5 ports) is shown by line 13, and the photocurrent 12 when V=V2 (for example 1 volt) is shown by line 4. This photocurrent i1. When i2 is mt++, the photocurrent J1 is calculated by the following formula.
Find +J2.

jl =al ii +a2 i2...
・(1) j2 = b1i1 +b2 i2
...(2) Here, for example, al=-1,0, a2
= 2.07, b1 = 2.0, and b2 = -2.0, the changes in photocurrents j1 and j2 are shown in line 5. of Fig. 5. ! 6
Shown below.

Next, as the rjfJ2 photoconductor layer 16, zinc selenide (Z
The spectral sensitivity of the photocurrent when the sandwich type photoelectric conversion element 20 is produced in the same manner as above using nS e) is
It is shown in FIG. The photocurrent j3 at this time is represented by a line NOR. Photoconductor layer 14.16 having such properties
are laminated by sharing a light-transmitting common electrode 15, and when light is incident from the individual electrode 17 side of the second photoconductor layer 16, the second
Since the photoconductor layer 16 acts as a filter, the photocurrent j11j2tj3 is equal to the line 128.79 in FIG.
,,/10. This is CIE's r+
It was confirmed that the g+b tristimulus value showed a spectrum close to ;r. By calculation based on this photocurrent J1+J2+J3, all the color information (hue, saturation, brightness) can be detected accurately.

When detecting color information, it is sufficient to have three types of independent photocurrents with different spectral sensitivities, but if you take into account the connection with output equipment, the spectral sensitivity of photocurrents of class 3!11 is CI
E'Igr b spectral tristimulus values are most desirable. In this example, the obtained photocurrent Jl +J2
Another major feature is that the spectral sensitivity of +J3 is very close to the r+li+tl spectral tristimulus values.

In addition to the photoconductor material of the above embodiment, first photoconductor scrap 14
Nitrogen-doped amorphous hydrogenated silicon (a-
S iN -A s -T e),
Indium sulfide (In2S*) or the like may be used as the second photoconductor layer 1G, and the above a-SiNx:
) I, a-S iCx : H1 Cadmium sulfide (CdS), zinc sulfide (Z no ), etc. may be used. In addition, as a result of manufacturing the photoelectric conversion element 11 using these combinations, if the optical forbidden band width and the calculation method of the applied voltage and photocurrent are optimized for each combination of materials, the manuscript can be converted as in the above embodiment. color information was detected accurately.

A cross-sectional view of a photoelectric conversion element 11a according to another embodiment of the present invention is shown in diagram vJB. This example is similar to the previous example;
Corresponding parts are given the same reference numerals. The feature of this embodiment is that the optical forbidden band width of the Pt51 photoconductor layer 14 is
The materials of the first and second photoconductors 14 and 16 of the above embodiment are reversed so that the width is larger than the optical forbidden band width of the photoconductor N16, and the Pt51 individual electrodes 13 and the electrically insulating substrate 12 is made transparent so that light 18 enters from the insulating substrate 12 side. As a result, a photoelectric conversion element 11a capable of accurately detecting color information of a document was manufactured, similar to the above embodiment.

Note that, in general, most photoconductor materials have a reduced spectral sensitivity on the shorter wavelength side of incident light due to recombination involving surface strata, so if a document reading device is manufactured based on the principles of the present invention, It goes without saying that the same effects as in the examples can be obtained even if materials other than those mentioned above are used as the photoconductor material.

Effects As explained above, according to the present invention, two photoconductor layers having different optical forbidden band widths are laminated using a common transparent electrode, and the voltage applied to the common electrode is changed. Then, a photocurrent whose spectral sensitivity characteristics change in response to the applied voltage is calculated. This allows the color of the incident light to be accurately f
It is possible to distinguish between JI and C. As a result, it is possible to obtain a document reading device that can read documents of multiple colors at high resolution and high speed without using color filters or switching the color of the illumination light source.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a photoelectric variable element 11 used in a document reading device according to an embodiment of the present invention, and FIG. 2 is a graph showing the spectral sensitivity and light absorption coefficient of photocurrent generated by a photoconductor. Third
The figure is a block diagram showing the configuration of a document reading device 21 according to an embodiment of the present invention, FIG. 4 is a graph showing the spectral sensitivity when the voltage applied to the first photoconductor W114 is changed, and FIG. Graph showing the calculation results according to equation 1 and equation 2, f:t
Figure S6 is a graph showing the spectral sensitivity of the second photoconductor layer 16;
FIG. 7 is a graph showing the spectral sensitivity obtained by laminating the first and second photoconductor layers 14 and 16 and calculating the photocurrent that changes in response to the voltage applied to the common voltage ff115,
Figure m8 is a cross-sectional view of a photoelectric conversion element 11a of a document reading device according to another embodiment of the present invention, Figure tpJS is a cross-sectional view of a photoelectric conversion element of a conventional contact type image sensor, and Figure 10 is a cross-sectional view of a photoelectric conversion element 11a of a document reading device according to another embodiment of the present invention. It is a sectional view of a photoelectric conversion element of a contact type image sensor of the technology. 11.11a, 19.20---Photoelectric conversion X T112
... electrically insulating substrate, 13 ... first individual electrode, 1
4.16... Photoconductor layer, 15... Transparent common electrode, 17... Transparent second individual electrode, 21... Original reading device, 23... DC power supply, 24. 25...Current detection means, 26...Control unit agent Patent attorney Number of strokes Keiichi 1st figure person O□ 2nd figure: i table? , ; 3m 4th prisoner Figure 7 Figure 9 Figure 10

Claims (1)

[Scope of Claims] A first individual electrode, a first photoconductor layer, a light-transmitting common electrode, and a second photoconductor having physical-optical characteristics different from those of the first photoconductor layer are formed on an electrically insulating substrate. A photoelectric conversion device configured by laminating a body layer and a second individual electrode in this order, the first photoelectric conversion device consisting of a first individual electrode, a first photoconductor layer, and a translucent common electrode. and a second photoelectric conversion element constituted by the light-transmitting common electrode, the second photoconductor layer, and the second individual electrode; By applying at least two different voltages to the electrodes, and detecting and arithmetic processing each photocurrent from the first photoelectric conversion element and the second photoelectric conversion element obtained thereby, the incident light is A document reading device characterized in that the optical condition of the document is determined.