JPH06342900A - One-dimensional color image sensor - Google Patents

Abstract

PURPOSE:To provide a one-dimensional image sensor in which an interval of adjacent sensor elements can be narrowed by commonly forming output lines of three photodiodes for one pixel. CONSTITUTION:Output lines 24 from cathodes of three photodiodes 20a-20b for one pixel are commonly connected, the commonly formed output lines are formed on the photodiode thereby to narrow an interval between adjacent sensor elements. The output lines are formed of transparent conductive films to further effectively use a photoreceiving surface of the photodiode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-dimensional color image sensor used in color digital copiers, color facsimiles, color image scanners and the like.

[0002]

2. Description of the Related Art FIG. 5 is an enlarged view of a sensor element portion of a conventional one-dimensional image sensor. In the figure, three photodiodes 10 that sense light for one pixel are shown.
a, 10b, and 10c are arranged in the vertical direction (sub-scanning direction), and the output lines 16a, 16b, and 1 are separately provided for each.
6c is provided. In addition, the blocking diodes 12a, 12b, 12c are connected to the wirings 14a, 14b, 14
The corresponding photodiodes 10a, 10b, 1 by c
0c and front-to-front (connect cathodes) or back-to-back (connect anodes). This one photodiode and one blocking diode constitute one sensor element, and a plurality of sets of such sensor elements are arranged in the lateral direction (main scanning direction) to form a one-dimensional color image sensor.

[0003]

By the way, the photodiodes 10a to 10c of FIG. 5 are respectively provided with output lines 16a to 16c. Therefore, a region for securing an output line is required between the photodiodes adjacent to each other in the main scanning direction. Moreover, it is necessary to secure a certain margin between the lines depending on the accuracy of the alignment when forming the wiring. However, in a high-density contact image sensor, it is desirable that the sensor elements are as close to each other as possible, and if the photodiodes are separated from each other to form the output line, the performance of the image sensor is reduced. There's a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a one-dimensional color image sensor capable of reducing the distance between adjacent sensor elements in the main scanning direction.

[0005]

According to a first aspect of the present invention for solving the above-mentioned problems, one pixel detecting means for sensing a color image is composed of a plurality of sensor elements each including a photodiode and a blocking diode. Is
Further, in the one-dimensional color image sensor in which a large number of the pixel detecting means are arranged in the main scanning direction, the output wiring of the photodiode of each of the pixel detecting means is formed in common, and the common output wiring is provided above the photodiode. It is characterized by being formed.

According to a second aspect of the present invention, for example, a region for forming a plurality of photodiodes and a region for forming a plurality of blocking diodes are separately provided for each of the pixel detecting means.

According to a third aspect of the present invention, for example, the output wiring of the common photodiode is formed of a transparent conductive film.

According to a fourth aspect of the invention for solving the above-mentioned problems, one pixel detecting means for sensing a color image is composed of a plurality of sensor elements each including a photodiode and a blocking diode, and the main scanning direction. In the one-dimensional color image sensor having a large number of the pixel detecting means arranged therein, the plurality of the pixel detecting means are divided into a plurality of blocks each having the same number of channels as the output circuit, and the one pixel detecting means is provided. While connecting the outputs of the multiple sensor elements that make up
For each block, the same number of inputs as the plurality of sensor elements forming the one pixel detection means are provided, and these inputs are commonly used as the inputs of the sensor elements of the pixel detection means that sense the same color. It is characterized by being connected.

According to a fifth aspect of the present invention, for example, a plurality of inputs of each block are connected to each other through corresponding transistors, gates of corresponding transistors of each block are commonly connected, and a signal supplied to the gates is supplied. According to the configuration, any one of the plurality of inputs of each block is selected and the image signal of the same color is output from each block.

According to a sixth aspect of the invention, for example, a shift register for supplying a signal to the gate of the transistor at a predetermined timing is provided.

According to a seventh aspect of the present invention, for example, the transistor is formed on the same substrate as the photodiode and the blocking diode.

[0012]

According to the first aspect of the present invention, with the above configuration, the output wiring of the photodiode of each pixel detecting means is formed in common, and the common output wiring is formed above the photodiode, so that the main scanning is performed. The distance between the photodiodes adjacent to each other in the direction can be reduced.

According to the second aspect of the present invention, since the blocking diode is formed in a region different from the photodiode, the area of the light receiving surface of the photodiode can be increased.

According to a third aspect of the present invention, the common output wiring is formed of a transparent conductive film such as ITO.
The light emitted to the photodiode is not blocked by this common output line, so that the light receiving surface of the photodiode can be effectively used.

According to a fourth aspect of the present invention, by the above configuration, the same number of inputs as the number of a plurality of sensor elements constituting one pixel detecting means are provided for each block, and these inputs are provided to the sensor elements of each pixel detecting means. Among them, the common connection to the input of the sensor element that senses the same color allows the operation of supplying the signal for reading the charge accumulated in the photodiode to the blocking diode in order for a plurality of inputs. As a result, the color image signal of each color can be sequentially taken out from the output wiring commonly formed for the plurality of photodiodes of each pixel detecting means.

According to a fifth aspect of the present invention, a plurality of inputs are connected to each other through, for example, three transistors, and the signals supplied to the connected inputs are switched by the transistors so that only a desired blocking diode is formed. Can supply a signal to. Accordingly, it is possible to select any one of the plurality of inputs of each block and output the image signal of the same color from each channel.

According to the sixth aspect of the invention, since the gate of the transistor is provided with a shift register for supplying a signal at a predetermined timing, the transistors can be sequentially driven with a simple structure.

According to a seventh aspect of the present invention, since the transistor is formed on the same substrate as the photodiode and the blocking diode, the number of mounting terminals can be reduced, and the cost and space can be reduced. You can

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a part of a one-dimensional color image sensor circuit which is an embodiment of the present invention, and FIG. 2 is an enlarged view of a sensor element part of a one-dimensional image sensor which is an embodiment of the present invention. 2 is a plan view similar to FIG. 2 for another embodiment, and FIG. 4 is a circuit diagram of an embodiment in which a transistor is connected to the input portion of the circuit of FIG. 1 as switch means.

FIG. 1 shows first to fifth blocks, and each block is assumed to be composed of 4 channels (actually, 16 channels, 32 channels, etc.) for convenience of explanation. ). And one photodiode of each block has three photodiodes 20.
a, 20b, 20c and three blocking diodes 2
2a, 22b, 22c are included, back to
The photodiode 20a and the blocking diode 22a connected to the back, the photodiode 20b and the blocking diode 22b, and the photodiode 20c and the blocking diode 22c constitute three sensor elements. One pixel detection means is composed of these three sensor elements and senses light of three primary colors for one pixel. In addition,
As will be described later, the light reflected from the original is refracted by the prism with a refractive index that depends on the wavelength, or only the light of a predetermined wavelength is transmitted by the filter and is incident on the photodiodes that sense each of the three primary colors.

As can be seen from FIG. 1, the output lines from the cathodes of the three photodiodes 20a to 20b for one pixel are connected in common, and the output lines of the corresponding channels of each block are connected in common. Two output lines 2a, 2
b, 2c and 2d, respectively. On the other hand, as for the input lines connected to the cathodes of the blocking diodes 22a to 22c, corresponding ones of the channels in one block are commonly connected, and for example, in the first block, the inputs 1a-1, 1b-1, 1c-1 are connected. Respectively connected to. Therefore, there are a total of 15 inputs, three for each block, and a total of four outputs.

Each of the four output lines is connected to an amplifier (not shown) for amplification. The input of this amplifier is virtually grounded by an imaginary short, and the four output lines are always maintained at the ground potential. As a result, it is possible to effectively prevent crosstalk with other output lines at the portions where the output lines intersect with each other.

The circuit of FIG. 1 operates as follows. First, when a driving input pulse is supplied to the input 1a-1 of the first block, the leftmost four blocking diodes 22 of each of the four channels included in the first block are supplied.
a is turned on. As a result, the charges accumulated in the corresponding four photodiodes 20a are taken out as a current, the signal of the first channel is output from the output line 2a, the signal of the second channel is output from the output line 2b, and the signal of the third channel is output line. From 2c, the signal of the fourth channel is output line 2d
, Respectively, are taken out at the same time. Next, when a drive input pulse is supplied to the input 1a-2 of the second block,
Similar to the block, the signals stored in the four photodiodes 20a of each channel are simultaneously taken out from the output lines 2a to 2d. Thereafter, the same operation is sequentially performed up to the fifth block, so that the signal of the photodiode 20a is taken out from each channel of each block.

Next, in order from the first block, this time, a drive input pulse is supplied to the inputs 1b-1, 1b-2, ..., 1b-5, and the signal of the photodiode 20b is supplied from each channel of each block. Take out. Further, inputs 1c-1, 1c-2, ..., 1c-5 are sequentially input from the first block.
Is supplied with a drive input pulse to extract the signal of the photodiode 20c from each channel of each block. As a result, all color image signals for one line are extracted.

FIG. 2 is a diagram showing a part of the actual semiconductor structure of the circuit of FIG. 1, and corresponds to FIG. 5 showing the conventional structure.
As shown in the figure, three photodiodes 20a-20
c are arranged vertically, and the blocking diodes 22a to 22c are formed under the blocking diodes 22a to 22c and are connected to the input line 1a-1 and the like as shown in FIG. By forming the blocking diodes 22a to 22c in a region different from the region where the photodiodes 20a to 20c are formed in this manner, it is possible to secure a wider light receiving surface of the photodiodes 20a to 20c.

As shown in FIG. 2, the area of 20a of the three photodiodes is formed to be the largest, and this is used as a photodiode for sensing blue (B) light. It is natural that all three photodiodes have the same area, but the blocking diodes 22a ...
Due to the wiring connection with 22c, the areas are different in this way. However, when the photodiode is composed of the most general amorphous silicon (a-Si), the sensitivities of the three primary colors of light, red (R), green (G), and blue (B), are different, and therefore the sensitivity is not necessarily three. It is not necessary for the two photodiodes to have the same area. Rather,
It is desirable to increase the area of the photodiode for receiving blue (B), which has the lowest sensitivity. Therefore, if the photodiode 20a having the largest area in FIG. 2 is for blue (B), there is an advantage that the weak sensitivity can be compensated. When the incident light is refracted by the prism and is split into red (R), green (G), and blue (B) colors, the order of the remaining photodiodes 20b and 20c is determined by the wavelength of light. Is a green (G) photodiode, and 20c is a red (R) photodiode.

Further, in FIG. 2, as explained in FIG. 1,
The state where the output lines 24 of the three photodiodes 20a to 20c are common is clearly shown. Therefore, it is possible to significantly reduce the distance between the adjacent sensor elements, as compared with the case where the output line is separately provided for each photodiode. The reason why the three output lines 24 can be shared in this way is that the matrix connection having the configuration as shown in FIG. 1 is adopted.

Further, as shown in FIG. 2, each output line 24 is formed so as to pass over the photodiodes 20a to 20c. In the conventional one-dimensional color image sensor,
The output line was formed between adjacent photodiodes,
In this way, in addition to the width of the output line itself of 10 μm, it is necessary to provide a space of 10 μm on both sides of the output line in consideration of a margin due to the accuracy of alignment. It had to be about 30 μm. If the photodiodes are spaced apart from each other in this way, there is a problem that an image signal cannot be obtained with high sensitivity when the density is increased.

In order to solve such a problem, in this embodiment, the output line is formed on the photodiode as described above. In this way, the light-receiving surface of the photodiode is narrowed by the width of the output line, but the width of the output line is at most about 10 μm, so the reduction in sensitivity due to this has no significant effect. Since the distance between adjacent photodiodes can be narrowed more than that, there is an advantage that a high-density image signal can be obtained with high sensitivity. Since the above-mentioned output line 24 can be formed at the same time as the electrode lines formed in other portions, a special process for forming this output line 24 is unnecessary. Even if the output lines 24 are formed on the photodiodes in this way, each output line is electrically connected to the transparent electrode of each photodiode, so that there is no problem of generating extra capacitance.

If the reduction of the light receiving surface by forming the output line on the photodiode becomes a problem, the output line may be formed of a transparent conductive film such as ITO. In this way, the light can pass through the transparent conductive film, so that the light reaching the photodiode is not blocked. However, in this case, a separate step for forming ITO or the like is required.

FIG. 3 is a plan view showing another embodiment of the present invention. In this case, three photodiodes 20a to 20c for one pixel are formed so as to be included in one square 31. ing. A color filter (not shown) that transmits only a predetermined color is used for the spectral distribution of the incident light, and the color filter is arranged above each photodiode. The color filter does not need to consider the order of wavelengths as in the case of a prism, and in this embodiment, photodiodes of each color are arranged in the order of red (R), blue (B), and green (G) from the top. is there. The configurations of the blocking diodes 22a to 22c are the same as in the case of FIG. This embodiment also has substantially the same actions and effects as the above-mentioned embodiments.

FIG. 4 shows a thin film transistor (TFT) 30 as a switching means on the input side of each block of the circuit of FIG.
It is a circuit diagram of an example which provided a, 30b, and 30c. The TFTs 30a to 30c are photodiodes 20a to 20c.
c and the blocking diodes 22a to 22c are preferably provided on the same substrate. In FIG. 1, input 1a
-1, 1b-1, 1c-1, ..., 1a-5, 1b-
5, 1c-5 are connected to each block via the TFTs 30a to 30c, whereby the inputs of the blocks are single inputs 36-1 to 36-5. Then, three gate lines 32a, 32b, 32c having a common gate of the corresponding TFT 30 of each block are connected to the shift register 34. If the shift register 34 is provided, by supplying a pulse to one input of the shift register 34 at a predetermined time interval, the gate lines 32a, 32
Since signals can be sent to b and 32c in a predetermined order, the switching operation becomes easy.

In FIG. 4, the signals supplied to the inputs 36-1 to 36-5 can pass only the TFTs to which the gate signal is supplied among the gate lines 32a to 32c. Therefore, by supplying signals to the gate lines 32a to 32c in a predetermined order, an image signal of a predetermined color can be obtained from the output line. Moreover, as described above, the image signal for one line is the first one for the first color.
Since the next color is read out by one line and the last color is read out by one line after the line is read out, the gate lines 32a to 32c may be switched line by line. For example, in the case of 5 ms / line reading, switching is performed at intervals of about 5 ms. This relatively slow switching operation can be sufficiently performed using the shift register 34. If the shift register 34 is also formed on the same substrate by using thin film transistors, it is not necessary to separately connect a shift register circuit.

With the circuit configuration shown in FIG. 4, the circuits of the monochrome image sensor which have been conventionally used can be used for the circuits other than the part shown in FIG. 4, so that the existing apparatus can be effectively utilized. You can Moreover, as in the embodiment of FIG.
If 0c is provided, there is an advantage that the number of bondings of the entire circuit can be reduced and the assembling process can be simplified.

The present invention is not limited to the above embodiments, but various modifications can be made within the scope of the invention.

[0036]

As described above, according to the invention described in claim 1, the output wiring of the photodiode is formed in common,
Furthermore, by forming this common output wiring on top of the photodiodes, the spacing between adjacent photodiodes is greatly increased compared to the conventional one in which output wiring is formed between adjacent photodiodes in the main scanning direction. It can be narrowed, thus providing a high density one-dimensional color image sensor.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, the blocking diode is formed in a region different from the photodiode, so that the area of the light receiving surface of the photodiode can be increased. Therefore, it is possible to provide a one-dimensional color image sensor capable of improving the sensitivity.

According to the third aspect of the present invention, the common output wiring is formed by the transparent conductive film such as ITO, so that the light radiated to the photodiode is not blocked by the common output line. Therefore, it is possible to provide a one-dimensional color image sensor capable of improving the sensitivity by effectively using the light receiving surface of the photodiode.

According to the fourth aspect of the present invention, by virtue of the above-mentioned configuration, the color image signals of the respective colors are sequentially output from the output wiring commonly provided for the plurality of photodiodes included in each pixel detecting means. Therefore, the number of output wirings can be reduced and the distance between the photodiodes can be narrowed, and thus a high density one-dimensional color image sensor can be provided.

According to the invention of claim 5, in addition to the effect of the invention of claim 4, by connecting a plurality of inputs of each block to each other through corresponding transistors, the connected inputs can be connected. One signal to be supplied can be switched by the transistor to supply a signal to only a desired blocking diode, whereby any one of the plurality of inputs of each block can be selected to output the same color from each channel. It is possible to provide a one-dimensional color image sensor capable of outputting an image signal and thus reducing the number of inputs.

According to the sixth aspect of the present invention, by further providing a shift register for supplying a signal to the gate of the transistor at a predetermined timing, the transistors can be sequentially driven with a simple structure. A one-dimensional color image sensor can be provided.

According to a seventh aspect of the present invention, by further forming the transistor on the same substrate as the photodiode and the blocking diode, there is provided a one-dimensional color image sensor capable of saving space. You can

[Brief description of drawings]

FIG. 1 is a circuit diagram of a one-dimensional color image sensor that is an embodiment of the present invention.

2 is an enlarged plan view showing a part of the one-dimensional color image sensor of FIG. 1. FIG.

FIG. 3 is a plan view showing an enlarged part of a one-dimensional color image sensor according to another embodiment of the present invention.

FIG. 4 is a circuit diagram of a one-dimensional color image sensor according to another embodiment of the present invention.

FIG. 5 is an enlarged plan view showing a part of a conventional one-dimensional color image sensor.

[Explanation of symbols]

2a to 2d, 16a to 16c, 24 Output wiring 10a to 10c, 20a to 20c Photodiode 12a to 12c, 22a to 22c Blocking diode 14a to 14c Wiring 30a to 30c Thin film transistor (TFT) 34 Shift register 36-1 to 36-5 Input Terminal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H04N 5/335 C // H01L 31/10

Claims (7)

[Claims] 1. A one-dimensional color image in which one pixel detecting means for sensing a color image is composed of a plurality of sensor elements including a photodiode and a blocking diode, and a large number of the pixel detecting means are arranged in the main scanning direction. In the sensor, the one-dimensional color image sensor is characterized in that the output wiring of the photodiode of each of the pixel detection means is formed in common, and the common output wiring is formed above the photodiode. 2. The one-dimensional color image sensor according to claim 1, wherein each of the pixel detection means is provided with a region for forming a plurality of photodiodes and a region for forming a plurality of blocking diodes separately. 3. The one-dimensional image sensor according to claim 1, wherein the output wiring of the common photodiode is formed of a transparent conductive film. 4. A one-dimensional color image in which one pixel detecting means for sensing a color image is composed of a plurality of sensor elements consisting of a photodiode and a blocking diode, and a large number of the pixel detecting means are arranged in the main scanning direction. In the sensor, the plurality of arrayed pixel detection means is divided into a plurality of blocks having the same number of channels as the number of channels of the output circuit, and outputs of a plurality of sensor elements constituting the one pixel detection means are commonly connected. At the same time, the same number of inputs as the number of the plurality of sensor elements forming the one pixel detection means are provided for each block, and these inputs are used as the inputs of the sensor elements that sense the same color among the sensor elements of each pixel detection means. A one-dimensional color image sensor that is connected in common. 5. The plurality of inputs of each block are connected to each other through corresponding transistors, the gates of the corresponding transistors of each block are commonly connected, and the plurality of inputs of each block are supplied by a signal supplied to the gates. 5. The one-dimensional color image sensor according to claim 4, wherein any one of the above is selected to output the image signal of the same color from each block. 6. The one-dimensional color image sensor according to claim 5, wherein a shift register for supplying a signal to the gate of the transistor at a predetermined timing is provided. 7. The one-dimensional color image sensor according to claim 5, wherein the transistor is formed on the same substrate as the photodiode and the blocking diode.