Source: http://www.google.com/patents/US4703169?dq=%22Meaning-based+advertising+and+document+relevance+determination%22
Timestamp: 2016-05-27 14:27:04
Document Index: 546518443

Matched Legal Cases: ['art 2', 'art 12', 'art 129', 'art 129', 'art 129', 'art 129']

Patent US4703169 - Reading apparatus having PIN structure wherein storage and parasitic ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA reading apparatus including a plurality of photodiodes each provided with a storage capacitor, the photodiodes adapted to store electric charge in the storage capacitor upon receiving light, a plurality of analog switches each connected in series with one end of each of the photodiodes, an element...http://www.google.com/patents/US4703169?utm_source=gb-gplus-sharePatent US4703169 - Reading apparatus having PIN structure wherein storage and parasitic capacitance differsAdvanced Patent SearchPublication numberUS4703169 APublication typeGrantApplication numberUS 06/945,072Publication dateOct 27, 1987Filing dateDec 18, 1986Priority dateJun 21, 1984Fee statusLapsedAlso published asDE3522314A1, DE3522314C2, DE3546717C2, US4740710Publication number06945072, 945072, US 4703169 A, US 4703169A, US-A-4703169, US4703169 A, US4703169AInventorsHirotaka AritaOriginal AssigneeKyocera CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (3), Referenced by (20), Classifications (12), Legal Events (7) External Links: USPTO, USPTO Assignment, EspacenetReading apparatus having PIN structure wherein storage and parasitic capacitance differs
US 4703169 AAbstract
1. A reading apparatus comprising:a plurality of photoelectric converter elements each provided with electric charge storage means, said photoelectric converter elements adapted to store electric charge in said electric charge storage means upon receiving light; a plurality of switches each connected in series with one end of each of the photoelectric converter elements; means for leading out an amount of electric charge as a signal when the amount of electric charge is stored in said electric charge storage means; means for rendering said plurality of switches conductive successively in time sequence; said electric charge storage means comprising a storage capacitor; said photoelectric converter element comprising a photodiode; wherein said storage capacitor and said photodiode are substantially integrally formed of amorphous silicon photoconductor and said amorphous silicon photoconductor comprises a p-i-n semiconductor. 2. A reading apparatus as claimed in claim 1, wherein the film thickness of said amorphous silicon photoconductor is determined to be within the range of from 0.4 to 3.0 μm.
3. A reading apparatus as claimed in claim 1, wherein the film thickness of said amorphous silicon photoconductor is determined to be within the range of from 1.0 to 2.0 μm.
4. A reading apparatus as claimed in claim 1, wherein the film thickness of said amorphous silicon photoconductor is determined to be approximately 1.5 μm.
This is a division of application Ser. No. 747,062, filed June 20, 1985.
FIG. 1 is a perspective view showing a photo-detection part 2 in the reading apparatus of the prior art employing the focusing rod lense array. On a substrate 5, there are formed a common electrode 6 to be one electrode commonly for each photoelectric converter element, a photoconductor 7, and transparent electrodes 8 successively in this order as shown in FIG. 1. Additionally light-excluding metal layers 9 are applied on the transparent electrodes 8 except on light-introduction portions 10 for reflected light A. A transparent protective layer 11 made of SiO2 etc is so applied as to cover the common electrode 6, photoconductor 7, transparent electrodes 8, and light-excluding metal layers 9. A drive circuit part 12 such as a shift register is also provided on the substrate 5.
According to such conventional apparatus, the reflected light A from an original document 1 is passed through the transparent protective layer 11 and is received by the light-introduction portions 10, and then reading picture elements corresponding to the individual light-introduction portions 10 are produced.
However, the transparent protective layer 11 made of SiO2 is formed by means of sputtering method, or by applying alkoxide solution and heating the thus applied solution at approximately 400� to 500� C. in the above conventional apparatus, which leads to production of plasma or a temperature rise. Such severe layer-forming conditions reduce the quality of exposed portions of the photoconductor 7 made of amorphous silicon or the like which has already been formed. It has been found that dark current is remarkably increased to deteriorate the S/N ratio consequently.
According to a process of producing this apparatus, however, there are to be formed on the light-transmitting substrate 13, the light-excluding metal layer 15 normally made of Al, Cr, or the like by means of vacuum vapor deposition, the light-transmitting electrically insulative layer 16 made of SiO2 or the like by means of sputtering method, the light-transmitting individual electrodes 17 made of ITO (tin-indium oxide) or the like by means of vacuum vapor deposition method, the amorphous silicon photoconductor 18 by means of glow discharging method, and the common electrode 19 made of Al, Cr, and the like by means of vacuum vapor deposition method, successively in this order. Accordingly, it is impossible to form two layer of these five layers 15, 16, 17, 18 and 19 successively by means of the same thin film forming technique. Therefore, in order to form these layers it is required to use the suitable thin film forming apparatus depending on the layer to be formed. On the contrary, it is desirable to form at least two layers by a series of process of the same thin film forming technique in the light of the shrinkage of the required time or the improvement on the efficiency of the process.
Besides, there is a possibility that a short takes place between the light-excluding metal layer 15 and the light-transmitting individual electrodes 17 when pin-holes are produced in the light-transmitting electrically insulative layer 16. In consequence, such a problem is caused that the individual electrode 17 is electrically connected with other electrodes 17 via the light-excluding metal layer 15, thereby preventing the accurate reading picture elements from appearing and thus lacking in the reliability.
The present inventor who made elaborate and strenuous studies and researches with a view to solve the aforementioned problems has reached a recognition that the degree of clarity (contrast) of a reading image can be improved when the ratio of the capacitance of a storage capacitor to the capacitance of an analog switch is determined to be specified one.
A yet further objective of the invention is to elevate the characteristics of both the photodiode and the storage capacitor so as to make improvements in the degree of clarity and reproducibility of a reading image and thereby to further present a reading apparatus capable of effectuating a faithful image reading.
C1/SC&gt;1
C1/SC&gt;3
A reading apparatus according to a yet further aspect of the invention comprises: photo-detection means, said photo-detection means comprising: a substrate having at least a surface thereof made of electrically insulative material; a common electrode made of light-transmitting material and formed on the substrate; a light-excluding metal layer made of light-excluding material, formed on the common electrode, and having light-passing holes formed therein such that the light-passing holes are arranged in one directin to adjoin to each other; a photoconductor formed on the light-excluding metal layer and on those portions of the common electrode which face the light-passing holes of the light-excluding metal layer; and individual electrodes so formed on the photo-conductor as to respectively correspond to the light-passing holes of the light-excluding metal layer; and optical means for forming an image of an original document onto the substrate.
A reading apparatus according to yet another aspect of the invention comprises photo-detection means, said photo-detection means comprising: a substrate having at least a surface thereof made of electrically insulative material; a light-excluding metal layer made of light-excluding material, formed on the substrate, and having light-passing holes formed therein such that the light-passing holes are arranged in one direction to adjoin to each other; a common electrode made of light-transmitting material, and formed on the light excluding metal layer and on those portions of the substrate which face the light-passing holes of the light-excluding metal layer; a photoconductor formed on the common electrode; and individual electrodes so formed on the photoconductor as to respectively correspond to the light-passing holes of the light-excluding metal layer; and optical means for forming an image of an original document onto the substrate.
In another preferred embodiment, a protective layer is formed on the individual electrodes and on those portions of the photoconductor on whic hthe individual electrodes are not formed.
A method of producing a reading apparatus according to a yet further aspect of the invention comprises providing photo-detection means which comprises: a substrate having at least a surface thereof made of electrically insulative material; a light-excluding metal layer having light-passing holes formed therein, said light-excluding metal layer formed on the substrate by means of vacuum vapor deposition method; a common electrode made of light-transmitting material, said common electrode formed on the light-excluding metal layer and on these portions of the substrate which are exposed to the light-passing holes of the light-excluding metal layer; a photoconductor formed on the common electrode; and individual electrodes formed on positions in the photoconductor corresponding to the light-passing holes of the light-excluding metal layer; and providing optical means for forming an image of an original document onto the photo-detection means.
Besides it has also been proposed to present another type performing detection by means of such a light source as a flourescent 34a without this array 33 as shown in FIG. 5.
Namely, FIG. 6 illustrates an electric circuit diagram of electric charge stroage type. Photodiodes D11 to D1i, D21 to D2i, D31 to D3i, . . . , Dn1 to Dni effected by amorphous silicon semiconductor or the like fall into a plurality of n groups G1 to Gn. The photodiodes D11 to D1i are connected to a common electrode P1 in one group G1 among them. The common electrode P1 is connected to a bias power source 35 via a load resistance R1. The common electrode P1 is connected to a buffer amplifier A1 and applies a signal to a line 36. The photodiodes D11 to D1i are connected to a line 37 via analog switches S11 to S1i. The line 37 is connected to the other terminal of the bias power source 35 and is earthed. The analog switches S11 to S1i are connected to a shift register SR. Such arrangement of the group G1 is similarly applied to the other groups G2, G3, . . . , Gn and therefore the similar explanation is omitted, giving like reference marks to corresponding parts. The analog switches S11 to S1i, S21 to S2i, S31 to S3i, . . . , Sn1 to Sni are successively rendered conductive one at a time and scanned in time sequence by the shift register SR. That is, it is a single analog switch that is rendered conductive at a time. When the single switch is conductive, the other switches are non-conductive. The photodiodes D11 to D1i have element parallel capacitance shown by storage capacitors C11 to C1i respectively. Meanwhile the analog switches S11 to S1i have input capacitance SC11 to SC1i respectively. The other groups G2, G3, . . . Gn are also similarly arranged.
FIG. 7 is a fundamental electric circuit diagram of the electric charge storage type reading system shown in FIG. 6. Bias voltage is applied to a storage capacitor C connected in parallel with a photodiode D by a bias power source 35a. A predetermined amount of electric charge is therefore stored therein. The photodiode D receives the reflected light from the original document, and electric charge stored in the storage capacitor C is then discharged correspondingly to the amount of photoelectric conversion by such light-reception. Thereafter, when the analog switch S is suitably closed, voltage produced at the load resistance R is sent to an output terminal T at the time the storage capacitor C is recharged. A light signal is thus detected. Besides, reference sign TC designates a coupling capacitor, and SC does capacitance of the analog switch S. Likewise reference sign FC designated equivalent stray capacitance of the switch. The stray capacitance FC increases with the increase of the number n of the electric converter elements as shown in FIG. 6. The stray capacitance FC can be expressed by the following equation: ##EQU1## where C1 is capacitance of the storage capacitor C.
According to the apparatus of the invention, the reflected light l from the original document 1 comes from the side of the light-transmitting substrate 48. The reflected light l passes through the light-passing holes 50 corresponding to the respective photoelectric converter elements. Then the light l is converted into electricity in the photoconductor 52. Next, a reading signal is detected between the light-transmitting common electrode 49 and the individual electrodes 53.
In FIG. 10, (x) shows the result obtained by plotting the amount of increase of the output signal above the average value of the output signals while changing the ratio of C1 to SC with the value of C1 kept constant, and (y) likewise shows the result obtained by plotting the amount of decrease of the output signal below the average value of the output signals with the value of C1 kept constant.
As apparent from FIG. 10, it has been proved that the rate of variation of the output signal can be fixed within the range of �10% on condition that C1/SC>1. The reading apparatus adapted to be within such range is of no trouble in practical use whatsoever. It is apparent to be possible to reduce to a larger extent the rate of variation of the output signal caused by the non-uniformity of the capacitance C1 and the like, more preferably on condition that C1/SC>3.
Namely, amorphous silicon can be employed for the photoconductor to be formed on the common electrodes. Such employment of amorphous silicon (a-Si) as photoconductor assures that the ratio of Ip to Id can be the substantially large one, where Ip is a photo-current when light is emitted and Id is a dark current when light is not emitted. The present inventor's experiment has shown that the ratio if Ip to Id can be elevated to such a high value as 104 order at the illumination intensity of 100 lx when the p-i-n junction is provided in the semiconductor.
For example, in the case where the amount of incident light is 100 lx or so, the most suitable capacitance of the storage capacitor is approximately 15 pF. Accordingly, S: electrode area (m2) is determined by the following equation: ##EQU2## where C1=capacitance of the storage capacotor C(F)
.sup.ε r=specific dielectric constant of a-Si (approximately 11)
S is 2.3�10-3 cm2 when d is approximately 1.5 μm. When the area of the light-reception part is determined to be 100 μm�100 μm=10-4 cm2, the ratio of Ip to Id can be nevertheless thousandfold as shown in FIG. 11. Such value can be satisfactorily accepted as that required for the photoelectric converter apparatus. Furthermore, not only the present invention is based upon the recognition that the photodiode and the storage capacitor can be formed integrally when the a-Si photoconductor is utilized therefor, but also the present inventor who repeatedly conducted experiments has reached an absolutely unexpected recognition that various characteristics of each of the photodiode and the storage capacitor can be further effectively improved when the film thickness of such a-Si photoconductor is determined to be within the range of from 0.4 to 3.0 μm.
Precisely, as aforementioned, the capacitance SC of the analog switch includes that combination of the line capacitance of the wiring pattern formed on the substrate which is one of varying factors of the output signal. Accordingly, the wiring number must be made as small as possible with a view to reduce the influence of the line capacitance. According to the invention, the photoconductor of the photodiode and the dielectric of the storage capacitor are integrally formed of the substantially same material, viz. the photoconductor, thereby making no use of leads required for connection between photodiode and the storage capacitor. Consequently, the line capacitance accompanied thereby is decreased so as to reduce the capacitance SC.
In addition, according to the present invention, the material having relatively high resistance is chosen for such photoconductor in order to increase the capacitance C1 which further facilitates to effectively achieve the objectives of the present invention. In the foregoing embodiment, is used the amorphous silicon photoconductor.
FIG. 14 schematically shows an arrangement of the reading system of contact-type using the focusing rod lense array and provided with photo-detection part 129 according to the present invention. The photo-detection part 129 virtually corresponding to the original document 1 in a dimension of 1:1 is dispsed in close proximity to the original document 1 via the focusing rod lense array 93. LED 94 irradates the original document 1 with light. The reflected light from the original document 1 passes through the rod lense array 93 and is received by the photo-detection part 129.
FIG. 15 shows a perspective view of the photo-detection part 129 of FIG. 14. FIG. 16 is a cross section taken along the line VI--VI of FIG. 15. As shown in these FIGS. 15 and 16, on a substrate 71 having a surface thereof made of a light-transmitting electrically insulative material such as glass, there are formed a light-transmtting common electrode 72 made of, for example ITO (tin-indium oxide) or the like to be electrically connected with one electrodes of the respective photoelectric converter elements, a light-excluding metal layer 74 made of vapor-deposited metal of Al, Cr, or the like and provided with light-passing holes 73 for passing therethrough the reflected light D from the original document 1, a photoconductor 75 made of amorphous silicon, CdS etc, and individual electrodes 76 made of vapor-deposited metals of Al, Cr, and the like and provided in the respective photoelectric converter elements, sucessively in this order. Besides, the whole of substrate 71 may be made of light-transmitting electrically insulative material, or materials other than glass may be used therefor. In addition, a protective layer 77 is so applied as to cover the light-transmitting common electrode 72, the light-excluding metal layer 74, the individual electrodes 76. The protective layer 77 is not required to be transparent. The layer 77 is preferred to be so low with respect to light-transmittivity as to prevent entering of light into gaps among the individual electrodes 76, which would otherwise deteriorate the dissolution-capability of the reading picture elements. For material of the layer 77, relatively low-cost resin, for example silicon resin, epoxy resin, or the like may be utilized. A drive circuit 78 such as a shift register is disposed on the substrate 71, and connected with the common electrode 72 and the individual electrodes 76, thereby enabling the reading operation.
According to the producing method of the reading apparatus of the invention, to form the five layers, i.e. the light-transmitting layer 72 through the protective layer 77 successively on the light-transmitting substrate 71, either of the light-transmitting common electrode 72 and the light-excluding metal layer 74 can be effected by means of vacuum vapor deposition method. Hence, the two layers 72 and 74 can be succeedingly formed by means of vacuum vapor deposition method to be commonly employed. In effect, accordingly, thin film forming apparatus required to form only four layers 72; 74; 75; 76; 77 may be employed, thereby achieving the improvement in producing efficiency such as reduction in required time for producing.
Further, the protective layer 77 made of resin or the like is then formed on the exposed portion of the photoconductor 75 by means of printing method or coating method. Thereafter, these layers are heated at 280� C. or lower to be hardened. Such relatively loose condition will not deteriorate, for example, the characteristic of the amorphous photoconductor 75, thus effecting the reading apparatus excellent in S/N ratio and of high quality.
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