JPS6342611Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a compact contact type image sensor.

(Description of Prior Art) First, a conventional contact type image sensor will be explained. FIG. 1 is a diagram schematically showing the arrangement of components of a conventional contact image sensor.
1 is a document; 2 is a light-emitting element such as a light-emitting diode placed close to the document 1; the light-emitting device 2 illuminates the document and connects characters, figures, etc. in the illuminated portion; An image is formed on the light receiving section 4 by the image lens 3 and photoelectrically converted. This photoelectric conversion signal is controlled by the control section 5 and extracted as an image signal. These light receiving section 4 and control section 5 are generally formed on one substrate 6.

Next, a circuit diagram of the light receiving section 4 and the control section 5 will be explained with reference to FIG. In the same figure, the light receiving section 4
consists of a large number of linearly arranged (arrayed) light emitting elements, that is, photoelectric conversion elements 4a to 4n, and each of these light receiving elements 4a to 4n is formed into a plurality of sets, and the cathodes of the elements of each set are commonly connected. At the same time, these common connection points are commonly connected to the bias power supply 7 through the switches 5a to 5i constituting the matrix switch circuit of the control section 5, respectively. On the other hand, among the light receiving elements constituting each set, the anodes of the elements of the corresponding order are commonly connected, and the connection points are connected to the amplifiers 8 through other switches 5j to 5n constituting the matrix switch circuit of the control section 5, respectively.
Commonly connected to one input terminal of , and its output terminal 9
It is designed to get more output.

The operation of the conventional image sensor configured as described above will be explained using the signal waveform diagram shown in FIG.
The light receiving elements 4a to 4n are photovoltaic type photoelectric converters. First, in order to start reading the document 1, the power source (not shown) of the light emitting element 2 is turned on and a required voltage is constantly applied to cause the light emitting element to emit light at all times. This state is shown in FIG. 3A. Next, the switches 5a to 5n of the control section 5 are sequentially opened and closed in combination, first to turn on the element 4a as shown in FIG.
The element 4b as shown in FIG.
As shown in the figure, scanning is performed so as to operate the element 4n, and the light emitting elements 4a to 4n of the light receiving section 4 are sequentially and repeatedly brought into the operating state. As a result, a current proportional to the intensity of reflected light from the original 1 is obtained from each light receiving element in accordance with the sequential scanning, and an image signal as shown in FIG. 3E is obtained from the amplifier 9.

This conventional image sensor has the first drawback of high power consumption. This is because the light-emitting diode is always on when the original is placed in the reading section of the facsimile machine. is about
It is necessary to inject more than 100W of power into the diode. Furthermore, such a large amount of power generates a large amount of heat, which also causes a problem in that the light receiving element is adversely affected.

Second, it has the disadvantage of high manufacturing costs.
Regarding this point, first consider the light receiving section. This type of close-contact sensor is made smaller by making the width of the sensor the same as the width of the original to be read.For example, when reading an A4 size original at a resolution of 8 lines/mm. This requires a total number of light receiving elements (also called cells) of approximately 1,700 cells and a length of 210 mm. There are methods to manufacture such cells, such as using CdS as a photosensitive material or using amorphous silicon as a photosensitive material, but in order to make full use of the total number of cells, advanced thin film formation technology is required. Become. For example, if the cell size is about 100 μm square, it will be several tens of μm.
If a defect as small as this occurs in a cell, that cell becomes a defective product, resulting in poor cell manufacturing yield and ultimately increasing manufacturing cost. At present, basic data on the development technology for this type of high-yield sensor is still being accumulated.

The manufacturing cost of the control section is also high. For example, if the total number of cells is m=1700, the total number of switches 5a to 5n shown in FIG. 2 is at least n=2√=80
You will also need one. Furthermore, in order to faithfully output the intensity of the reflected light from the original, these switches need to be analog switches. This analog switch is more expensive than a normal digital switch. Furthermore, due to the relationship with cell impedance, analog switches are required to have high input impedance, and field-effect transistors are suitable switches for this purpose, but these elements are also expensive, and therefore the manufacturing cost of the entire control section is low. becomes higher.

(Object of the invention) An object of the invention is to provide a compact contact type image sensor that eliminates the drawbacks of conventional image sensors, has low power consumption, and is low in manufacturing cost.

(Structure of the invention) In order to achieve this object, an image sensor according to the invention includes a light emitting section, a light receiving section, and an optical imaging system, and makes light from the light emitting section incident on the original, and In an image sensor configured to receive reflected light at a light-receiving section and convert the intensity of this reflected light into electrical signal information; It is composed of a large number of light emitting elements blocked into groups, and one electrode of these light emitting elements is electrically insulated between different groups;
It has a first drive circuit provided on one side of the substrate and a second drive circuit provided on the other side of the substrate, and the first and second drive circuits are operated in combination with each other to cause these light emitting elements to emit light in sequence. One electrode of each of these light emitting elements is commonly connected to the corresponding switch of the first drive circuit for each group via a connecting means, and the connection is made using a through hole provided in the substrate. Furthermore, the other electrode of the light-emitting elements is commonly connected between the light-emitting elements selected from each group via the light-emitting element's light emission amount adjustment resistor, and each of these common connection points is connected to the second electrode. They are connected to the corresponding switches of the two drive circuits; the light-receiving section is formed of a band-shaped light-receiving element consisting of a single cell formed on a transparent substrate; It is characterized by having a dummy light-receiving element formed on the surface at a location where reflected light from the original does not enter.

(Description of Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are merely shown schematically to the extent that the structure of the present invention can be understood.

FIG. 4 is a diagram schematically showing the arrangement of the constituent components of the image sensor of the present invention. In this embodiment, 10 is a document, and a light emitting section 11 for irradiating light onto the document is attached to a substrate 12. 13,13
Reference numerals a and 13b are one drive circuit for controlling and driving the light emission of the light emitting section 11, and are attached to the light emitting section side of the substrate 12. The light from the light emitting unit 11 passes through the imaging optical system 14 and illuminates the original 10, and the light reflected from the original is detected by the light receiving unit 15 having light receiving elements (cells) 15a and 15b and photoelectrically converted. It is configured to receive electrical signals. This cell is attached to the opposite side of the transparent substrate 16 from the original. Reference numeral 17 denotes a dummy light receiving element provided in a location where reflected light from the original does not enter. Further, 18 is provided on the opposite side of the substrate 12 from the light emitting section 11.
This is the other drive circuit for driving the . As is clear from FIG. 4, in this configuration, the light receiving section is placed close to the original.

Next, the driving circuits 13 and 18 and the peripheral circuits of the light emitting section 11 will be explained using FIG. In this example, the light emitting unit 11 includes a total of m light emitting elements (cells),
For example, the light emitting diodes 11a to 1 of the light emitting unit 11
In order to form a monolithic array of 1 m and to reduce the number of switches, these cells are formed into blocks into a plurality of groups 19a to 19l. Generally, in the form of a monolithic array light emitting diode, a p-layer is formed in an array on an n-type substrate, so that the cathode side of each group is commonly connected. These groups 19
a~19l to each switch 20a~ of the drive circuit 18
20L, and are commonly connected to one electrode of the power supply 21 through the respective terminals. Further, the anodes of the light emitting elements 11a to 11m are connected in common with the anodes of the elements of the same order in each group, and grounded through common switches 22a to 22i of the drive circuit 13, respectively. Furthermore, in FIG. 5, reference numeral 23 denotes a light receiving section, which is composed of one or more single cell light receiving elements, receives light emitted from the light emitting elements in a point-sequential manner, and sequentially converts these incident lights into photoelectric elements. An electric signal is obtained, and this electric signal is sequentially outputted from an output terminal 25 via an amplifier 24.

When the switches of both drive circuits 13 and 18 of the circuit shown in FIG. 5 are combined to drive the light emitting elements 11a to 11m in sequence, the light emitting elements 11a to 11m are sequentially scanned.
By scanning the photodetector array once, first, the sixth
The element 11a is activated as shown in Figure A, and then the sixth
The element 11b operates as shown in FIG.
Finally, as shown in FIG. 6C, the element 11m is activated to emit light, and an output proportional to the intensity of reflected light from the original 10 is obtained from the output terminal 25, as shown in FIG. 6D.

The functional configuration of the image sensor of the present invention is shown in a block diagram as shown in FIG.
That is, the switches 20a to 20l and 22a to
Scanning unit 26 for operating 22i in combination
(not shown), a light emission driving section 27 including both drive circuits 13 and 18 and a stabilizing resistor to be described later, a light emitting section 11, a light receiving section 15, a signal processing section 28 having an amplifier 24, and a scanning section 26. , a clock 29 for synchronizing the light emission driving section 27 and the signal processing section 28.
It mainly consists of.

The eighth light emitting drive unit 27 and the light emitting unit 11
This will be explained using figures. Stabilizing resistors 30, 30a to 3 are provided at the anodes of each of the light emitting elements 11a to 11m of the light emitting unit 11 to adjust the amount of light emitted from the light emitting elements.
Connect 0m. Both drive circuits 1 of the light emission drive section 27
Reference numerals 3 and 18 are constructed of one-chip silicon ICs, and include shift registers 31 and 32, latch circuits 33 and 34, and switches 20a to 20, respectively.
Driving transistors 35a to 35i and 36a to 36l forming transistors 1 and 22a to 22n, respectively.
Contains. Further, these drive circuits 13 and 18 are connected to input lines 13a to 13c and 18a to 18c.
and shift registers 31 and 32, respectively.
Latch circuits 33, 34 and transistors 35a~
It is connected to the main electrode of 35i and the control electrodes of 36a to 36l.
The clock signal is also connected to the input line 13b and 18b.
A power signal is input to each of the terminals c and 18c. These signals are input to input lines 13a to 13.
c, and transistors 35a to 18c via 18a to 18c.
35i, 36a to 36l are operated in combination to drive the light emitting diodes 11a to 11m individually in a predetermined order. In this embodiment, the transistors 35 to 35i are current discharge transistors, and the transistors 36a to 36l are current sink transistors. Further, the number of these transistors 35a to 35i matches the number of light emitting elements in each block, and the number of transistors 36a to 35i corresponds to the number of light emitting elements in each block.
It is preferable that the number of 6l corresponds to the number of blocks.

Next, an example of the mounting state of the light emitting section 11 and the light receiving section 15 will be explained using FIGS. 9 and 10. First, FIG. 9A is a schematic plan view showing the side of the board 12 on which the light emitting section 11 and the drive circuit 13 are mounted, FIG. 9B is a schematic bottom view of this board, and FIG. 9C is a diagram showing this board. FIG. This substrate 12 is, for example, a thick film ceramic substrate, and this substrate 12 has
As shown in FIG. 9C, a wiring pattern (top conductor layer) 37 is printed with a thick film of gold paste, and as shown in FIG.
As shown in FIGS. and C, the blocked light emitting element groups 19a to 19l of the light emitting section 11 are electrically isolated from each other by using silver paste 38 or the like on the conductor layer 37 of this pattern. In this manner, it is attached and disposed at the center of the substrate 12. Individual stabilizing resistors 30, 30a are distributed on both sides of the array of light emitting parts 11 and correspond to each element.
~30m is provided as a thick film resistor. This resistor is used to uniformly adjust the amount of light emitted from the light emitting diode, which is a light emitting element, and is trimmed by, for example, a laser. Each resistance 30a~30m
The drive circuits 13 and 1 are connected to each other via a total of i output lines 40 using crossover tapes 39 from
It is connected to one main electrode of transistors 35a to 35i of transistors 3a and 13b. In this embodiment, the drive circuit 13 is divided into two parts 13a and 13b, but this is merely a design problem, and the arrangement is not limited to this.

As shown in FIG. 9B, individual conductors (bottom conductor layer) 41 are provided on the back surface of the substrate 12 corresponding to each light emitting diode, and one electrode of these light emitting diodes, that is, the cathode in this example, is the same. They are formed so that they can be connected to the drive circuit 18 provided on the back surface of the substrate 12, respectively. Therefore, as is clear from FIG. 9C, there is a conductor 41 on this substrate 12.
A through hole 42 and its wall conductor layer 43 are provided for electrically connecting the light emitting diodes 11a to 11m to the cathode sides thereof. Thereby, the groups 19a to 19l of light emitting diodes are electrically connected to the lower surface conductor layer 41.

Next, the light receiving section 15 will be explained using FIGS. 10A and 10B. This light receiving section is formed as a thin film light emitting element in the shape of a transparent substrate, and for example, as shown in FIG.
Elongated strip-shaped light receiving element portions 15a and 15b are arranged on a glass substrate 16 in parallel to each other. In this case, light from the light emitting elements 11a to 11m passes between both light receiving element portions 15a and 15b, and the light from the original 10
The reflected light from the surface of both light receiving element portions 15a and 1
Both light emitting elements are arranged apart from each other so that the light can be incident on the light emitting element 5b. Further, the length of the light receiving element is set to a length that can sufficiently receive reflected light from both the right and leftmost edges of the document.

Further, reference numeral 17 denotes a thin film-like dummy light-receiving element for removing dark current and spike noise, which is provided in a portion of the glass substrate 16 that is not exposed to reflected light from the document surface, and its characteristics are similar to those of the original light-receiving element. 1
It is equivalent to the characteristic of 5. This dummy light receiving element 1
7 can be formed as two light receiving element portions 17a and 17b. Therefore, these light receiving elements 1
5, 17, the light receiving element portions 15a, 15b,
17a and 17b can be formed simultaneously in the same manufacturing process. In this case, dummy element part 1
The area of 7a is the same as the area of the light receiving element portion 15a or 15b, and the area of the dummy element portion 17b is the same as the sum of the areas of both light receiving element portions 15a and 15b. With this configuration, when only one of the light-receiving element portions 15a or 15b is used, dark current or spike noise can be canceled by taking a differential with the dummy element portion 17a. In addition, when using both light receiving element portions 15a and 15b, dummy element portion 17b
It is possible to similarly achieve a canceling operation by taking the differential between the two. Moreover, the light receiving element portion 15a or 15b
When either one of them is of a light-shielding type, a differential can be established between both of these light-receiving element portions to eliminate dark current and the like. There is also a risk of spikes occurring due to the drive current when driving a light emitting element, but depending on how the element is used as described above,
Spike noise can be effectively canceled out.
In FIG. 10A, 44 and 45 are connection conductors provided for the light receiving element and the dummy element.

FIG. 10B is a schematic enlarged sectional view showing an example of the configuration of a light receiving element, in which a transparent electrode 46 is provided on a transparent substrate 16, and a light receiving layer made of, for example, an amorphous silicon photoreceptor is provided on this electrode 46. 47 is formed, and a metal electrode 48 is further formed above it.

(Effects of the invention) According to the configuration of the invention as described above, the following advantages can be obtained.

First of all, the image sensor of the present invention is cheaper than conventional image sensors. The reason for this is that the shape of the light-receiving element is a very simple single line, and the light-receiving area is large, so even if there are some defects, the defect area can be made smaller than the total light-receiving area, which reduces the variation in sensitivity. In addition, since the length of these elements is shortened by providing a dummy light-receiving element to remove dark current and spike noise, the yield rate due to micro defects can be reduced. It is possible to make it even smaller, and by using a suitable combination of a light-receiving element and a dark current removal element, it is possible to increase the yield in use.
The light-emitting element array of the light-emitting part is actually used in large quantities for optical printers, and can be manufactured using existing technology.Moreover, since the light-emitting elements are divided into small pieces, the manufacturing yield can be improved. It depends.

Further, according to the present invention, since a dummy light receiving element is provided for removing dark current and spike noise, a large S/N ratio can be achieved and temperature changes can be appropriately compensated for.

Furthermore, according to the present invention, since one light emitting element is constantly blinking, power consumption can be extremely reduced.For example, conventional image sensors consume approximately 100W of power, but the present invention's sensor According to , if the total number of light emitting elements m=1700, the power consumption is only about a few watts.

Furthermore, the drive circuit can be manufactured as a one-chip silicon device, and this is an all-digital circuit, and the drive transistor used as a switch can be simply switched digitally, making it easy to manufacture. Yes, and there is no need to make any special adjustments to the impedance of the light emitting element.

Furthermore, according to the present invention, the lead wire of the cathode of the light-emitting element is processed by providing a through hole in the substrate, so thick film printing on the substrate only needs to be done in one layer on both the front and back sides, which eliminates the problem of wire breakage and short circuits. The advantage is that there is no

As described above, the image sensor of the present invention maintains the small size and adhesive properties of conventional image sensors, reduces manufacturing costs, reduces power consumption, and can be driven at high speed, making it suitable for facsimile reading. It can be used as a sensor.

It is clear that the invention is not limited only to the embodiments described above, but can be subjected to many variations and modifications. For example, it is clear that the materials constituting each component are not limited to those mentioned above. Furthermore, since the drive circuit for driving the light emitting elements only needs to operate to drive each element in a matrix manner, it does not have to be a circuit constituted by the above-described shift register, latch circuit, or transistor. Furthermore, the connection polarity of the light emitting diode can be reversed from that of the above embodiment, in which case it is necessary to reverse the polarity of the other components.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the arrangement of the components of a conventional image sensor, FIG. 2 is a circuit diagram for explaining the electric circuit between the control section and the light receiving section of the sensor shown in FIG. 1, and FIG. Fig. 1 is a signal waveform diagram for explaining the operation of the sensor, Fig. 4 is a diagram showing a configuration example of the image sensor of the present invention, and Fig. 5 is a diagram for explaining the driving method of the sensor shown in Fig. 4. A circuit diagram, FIG. 6 is a signal waveform diagram for explaining the operation of the sensor in FIG. 4, FIG. 7 is a block diagram showing the configuration of the sensor in FIG. 4, and FIG. 8 is a light emission drive section in FIG. 7. and a circuit diagram for explaining the light emitting section, FIGS. 9A to 9C are line diagrams for explaining the mounting state of the light emitting section used in the image sensor of the present invention, and FIGS. 10A and B are circuit diagrams for explaining the image sensor of the present invention. FIG. 3 is a diagram for explaining a light receiving section of FIG. 10... Original, 11... Light emitting section, 11a to 11m...
Light emitting element, 12...substrate, 13, 13a, 13b,
18... Drive circuit, 14... Imaging optical system, 15, 23
...Light receiving part or light receiving element, 15a, 15b... Light receiving element part, 16... Transparent substrate, 17... Light receiving element for dummy, 17a, 17b... Light receiving element part for dummy, 1
9a, 19l... Group of light emitting elements, 20a to 2
0l, 22a to 22i...Drive circuit switch, 2
1...Power supply, 24...Amplifier, 25...Output terminal, 26
...Scanning unit, 27...Light emission drive unit, 28...Signal processing unit, 29...Clock, 30, 30a to 30m...Stabilizing resistor, 31, 32...Shift register, 33,
34...Latch circuit, 35a-35i, 36a-3
6l... Drive transistor, 37... Wiring pattern (upper conductor layer), 38... Paste, 39... Crossover tape, 40... Output line, 41... Conductor (lower surface conductor layer), 42... Three holes, 43... Wall conductor layer , 44, 45... Connection conductor, 46... Transparent electrode,
47... Light-receiving layer, 48... Metal electrode.

Claims (1)

[Claims for Utility Model Registration] 1. Includes a light emitting section, a light receiving section, and an optical imaging system,
In an image sensor configured to allow light from the light emitting section to enter a document, to receive reflected light from the document at the light receiving section, and to convert the intensity of the reflected light into electrical signal information, the light emitting section is configured to , consists of a large number of light emitting elements arranged linearly on one side of the substrate and blocked into groups of multiple light emitting elements, and one electrode of these light emitting elements is electrically insulated between different groups. further comprising a first drive circuit provided on one side of the substrate and a second drive circuit provided on the other side of the substrate, the first and second drive circuits being operated in combination with each other. and a switch for causing the light emitting elements to emit light sequentially, and the one electrode of the light emitting element is commonly connected to the corresponding switch of the first drive circuit for each group via a connecting means. , the connection is made using a through hole provided in the substrate, and the other electrode of the light emitting element is connected to a light emitting element selected from each group through a resistor for adjusting the amount of light emitted from the light emitting element. A common connection is made between the elements, and each of these common connection points is connected to a corresponding switch of the second drive circuit, and the light receiving section is a band-shaped light receiving element consisting of a single cell formed on a transparent substrate. further comprising a dummy light-receiving element formed on the same side of the transparent substrate as the light-receiving element and at a location where reflected light from the document does not enter. image sensor. 2. The image according to claim 1 of the utility model registration claim, characterized in that the band-shaped light-receiving element is constituted by two light-receiving element portions having the same light-receiving area and spaced apart from each other and arranged in parallel. sensor. 3. The image sensor according to claim 1, wherein the light receiving area of the dummy light receiving element is configured to be equal to the light receiving area of the light receiving element of the light receiving section. 4. The image sensor according to claim 1, wherein the light receiving element of the light receiving section and the dummy light receiving element are formed as amorphous silicon light receiving elements. 5. The image sensor according to claim 1, wherein the length of the strip-shaped light receiving element of the light receiving section is longer than the scanning length of the light emitting element. 6. The image sensor according to claim 2, wherein one of the two light-receiving element portions is configured to be used as the dummy light-receiving element in a light-shielded manner. 7 The dummy light-receiving element is formed by two dummy light-receiving element parts, the light-receiving area of one of the dummy light-receiving element parts is made equal to the light-receiving area of one light-receiving element part of the light-receiving part, and the other The image sensor according to claim 2, wherein the light-receiving area of the dummy light-receiving element portion is configured to be equal to the total light-receiving area of the two light-receiving element portions of the light receiving portion. .