JPH02244974A - Image sensor - Google Patents

Abstract

PURPOSE:To prevent the generation of a reading error of an image by successively arraying sensor chips on a main scanning line so that the rear face of the end part of the succeeding sensor chip is super posed to the surface of the end part of its adjacent sensor chip to optically shield the photodetecting element whose photodetecting element is opposed to the rear face of the end face of the adjacent sensor chip. CONSTITUTION:The surface of a base 8 is formed like steps and five sensor chips(CCDs) 91 to 95 are successively arrayed on the main scanning line so that the rear face of the end part of the succeeding sensor chip is superposed to the surface of the end face of its adjacent sensor chip. The photodetecting element 2a whose photodetecting face is optically shielded is formed on the position opposed to the rear face of the end part of the adjacent CCD 9. The image sensor 7 formed by said constitution is arranged in the inclined state from a platen glass 11 forming the carrier of an original 10 so that distances from the photodetecting face are averaged. Consequently, an output voltage at a dark time can be corrected and the generation of a reading error can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image sensor used in document reading devices of various devices such as digital copying machines.

2. Description of the Related Art In recent years, there has been a demand for equipment that optically reads and processes original documents, and image sensors have been developed. Currently, as one such image sensor, there is a close-contact type image sensor that reads the surface of a document while adjusting the contact closely with the document. This close-contact image sensor is one in which sensor chips with light-receiving elements arranged in an array are arranged in a straight line or in a staggered manner. Execute image reading.

Therefore, a first conventional example of an image sensor will be explained based on FIGS. 6 and 7. This image sensor 1 is
Four C0Ds (charge-coupled devices), which are sensor chips in which light-receiving elements 2 are arranged in an array; 3.
34 are arranged in a straight line on the substrate 4.

Here, the continuous CCD3. ~3. Due to manufacturing constraints, it is difficult to make the spacing between the light-receiving elements 2 as small as the arrangement pitch P of the light-receiving elements 2. Therefore, in order to correct the difference in arrangement density of the light-receiving elements 2 between the C0D3 to C0D34 that occurs due to this, in this image sensor l, the arrangement pitch P of the light-receiving elements 2 is changed as illustrated in FIG. Said CC
D3. It becomes smaller near the end of ~34. It should be noted that such an image sensor 1 can be adapted to read color images by sequentially attaching RGB filters (not shown) to successive light receiving elements 2.

In such a configuration, the image sensor 1 is arranged opposite to a paper conveyance path of a device and reads an image of a document that moves relatively in the sub-scanning direction. At this time, each light-receiving element 2 outputs a digital value based on the intensity of incident light from the image and the set threshold value, and the image is recorded or transferred using the dot-to-matrix method based on this output value.

Next, a second conventional example of an image sensor will be explained based on FIG. 8. This image sensor 5 includes five CCDs 6
．． ~6. are arranged in a staggered manner on the substrate 4. Here, in this image sensor 5, each of the CCDs 6. ~
6. The arrangement pitch P of the upper light receiving elements 2 is uniform, and this arrangement pitch P is the same as that of the CCD 6. These CCD6. ~6. are arranged so that their ends overlap in the sub-scanning direction. And this CCD6. ~6. A light-receiving element 2a whose light-receiving surface is optically shielded is provided in the overlapped portion, and is configured to output a dark time amount or [pressure] separately from image scanning.

In such a configuration, the image sensor 5 also reads an image of a document that moves relatively in the sub-scanning direction. At this time, in this image sensor 5, the CCDs 6, to 6. are arranged in two rows in the sub-scanning direction, so there is a shift in the timing of scanning one line on the image. Therefore, in such a staggered arrangement of image sensors 5, for example, the two preceding CCDs 6, 6, Temporarily store the output value in a memory etc., and then output it to the next three CCDs 6. ．． 6□6. Although time-division correction is performed to synchronize the output with CCD6. ~6I, due to its characteristics, dark current charges may be accumulated and a dark output voltage may be generated. This dark output voltage increases due to temperature rise or extension of scanning time, causing reading errors, so in this image sensor 5, each CCD 6. ~6. At each time, the output value of the light receiving element 2a whose light receiving surface is optically shielded is subtracted as the dark output voltage from the output value of the light receiving element 2 which performs image reading, thereby preventing the occurrence of reading errors due to temperature changes, etc.

Problems to be Solved by the Invention In the image sensor 1 illustrated in FIG. 6, each CCD 3. ~
34 are arranged in a line, it is not necessary to time-divisionally correct the output value, and the width of the device from front to back is short. However, CCD3
．． In order to correct the expansion of the arrangement pitch P of the light receiving elements 2 between . ~34
This makes the device expensive. Furthermore, in this image sensor 1, each CCD 3. ~3
4 do not overlap, all the light receiving elements 2 are used for image reading, and since there is no optically shielded light receiving element 2a, the dark output voltage cannot be corrected. For this reason, image reading errors are likely to occur in this image sensor l due to temperature changes and the like.

On the other hand, in the image sensor 5 illustrated in FIG. 8, the CCDs 6. ~6. By overlapping the end portions of , a light-shielded light-receiving element 2a is provided here to prevent reading errors due to dark output voltage and to make the array pitch P uniform. However, CCD6. ~6. are arranged in two rows in the sub-scanning direction, the width of the front and back of the device is large, and there is also a shift in the timing of image scanning (which requires time-sharing correction of the output values of CD6. to CD6.). Current digital copying machines, etc. are required to perform image scaling processing, and scaling in the main scanning direction generally involves interpolation or thinning of image data, or sub-scanning. The magnification in the direction is changed by changing the image scanning speed.However, C
CD6. ~6. In the image sensor 5 in which the images are arranged in two rows, it becomes necessary to change the timing of time-sharing correction as the image size changes, and an extremely complicated processing circuit is required.

Means for Solving the Problems The invention as set forth in claim 1 provides a plurality of sensor chips in which light receiving elements are arranged in an array, and connects these sensor chips to the end surfaces of adjacent sensor chips for the next sensor. The chips are sequentially arranged on the main scanning line with their end back surfaces overlapping each other, and the light receiving elements whose light receiving surfaces face the end surfaces of adjacent sensor chips are optically shielded.

According to the second aspect of the invention, an optical correction means having a focal length corresponding to the distance from the document surface is provided for each light receiving element.

A plurality of sensor chips each having active light-receiving elements arranged in an array are provided, and these sensor chips are sequentially arranged on the main scanning line by overlapping the end surface of the next sensor chip with the end surface of the adjacent sensor chip. However, by optically shielding the light-receiving element whose light-receiving surface faces the back side of the end of the adjacent sensor chip, it is possible to correct the output voltage in the dark, thereby preventing image reading errors due to temperature changes, etc. Since the sensor chips are arranged linearly in a single line and there is no need for time-division correction of image data, there is no need for a complex processing circuit.

Embodiment The first embodiment of the invention as claimed in claim 1 is shown in FIGS. 1 to 3.
This will be explained based on the diagram. Note that the same parts as in the conventional example described above are given the same names and numerals, and explanations thereof will be omitted. First, as illustrated in FIGS. 1 and 2, the image sensor 7 of this embodiment.

9. The surface of the substrate 8 is formed in a step-like manner and has five CCD sensor chips. ~9° are sequentially arranged on the main scanning line so that the end surface of the adjacent one overlaps the end back surface of the next one. A light-receiving element 2a whose light-receiving surface is optically shielded is formed at a position facing the rear surface of the end of the adjacent CCD 9.

Therefore, the image sensor 7 formed as described above
For example, as shown in FIG. 3, the platen glass 11 forming the conveyance path for the original 10 is inclined so that the distance from the light-receiving surface is average.

In such a configuration, this image sensor 7 has the following features:
Each CCD9. ~9. The light-receiving element 2 located approximately at the center of the document 10 focuses on the surface of the document 10. At this time,
Each CCD9. ~9. In the light receiving elements 2 located on both sides of
Although the front and back sides of the surface of the original IO are focused, this difference is small and falls within the allowable depth of focus of the light receiving element 2, so it does not pose a practical problem. Furthermore, since the image sensor 7 includes the light-shielded light receiving element 2a, the dark output voltage is corrected similarly to the image sensor 5 described above, thereby preventing the occurrence of reading errors.

Next, a first embodiment of the invention as claimed in claim 2 will be described based on FIG. This image sensor 12 has a structure in which a roof mirror lens array 13 serving as an optical correction means is attached to the image sensor 7 illustrated in FIG. 1, and is arranged parallel to the platen glass 11. . Here, the roof mirror lens array 13 includes each CC
D9°~9. Each light receiving element 2 is designed to have a different focal length, and all the light receiving elements 2 are accurately focused on the surface of the original 10.

In such a configuration, this image sensor 12 functions similarly to the image sensor 7 described above.

In addition, in this image sensor 12, the focal length of all the light receiving elements 2 is corrected using the roof mirror lens array 13, so the resolution of image reading is extremely high. The productivity of the device is also good because it can be attached easily.

Furthermore, a second embodiment of the invention as claimed in claim 2 will be described based on FIG. This image sensor 14 includes the image sensor 7 and platen glass 1 of the apparatus illustrated in FIG.
A roof mirror lens array 15, which is an optical correction means, is arranged between the lens and the lens. Here, this roof mirror lens array 15 is designed so that each light receiving element 2 has a different focal length.

In such a configuration, this image sensor 14 functions similarly to the previously described image sensor 7.12.

In the image sensor I4 of this embodiment, the roof mirror lens array 15 has a different focal length for each light receiving element 2, but for example, even if the predetermined distance of the roof mirror lens array is uniform, the focal length shown in FIG. Similar to the illustrated image sensor 7, the focus error is within the allowable value of the image sensor 14, and there is no problem in practical use.

Effects of the Invention The present invention provides a plurality of sensor chips in which light-receiving elements are arranged in an array as described above, and attaches these sensor chips to the end surface of an adjacent sensor chip at the end of the next sensor chip. By stacking their back surfaces and arranging them sequentially on the main scanning line, and optically shielding the light-receiving elements whose light-receiving surfaces face the back surfaces of the ends of adjacent sensor chips, it is possible to correct the output voltage in the dark, making it possible to correct images due to temperature changes, etc. reading errors are prevented,
Moreover, each sensor chip is arranged linearly in a row, and there is no need for time-division correction of image data, so there is no need for a complex processing circuit, and it is easy to change the magnification of image reading. By providing an optical correction means having a focal length corresponding to the distance to the surface, it is possible to easily prevent the resolution of image reading from decreasing.

2... Light receiving element, 7, 12.14... Image sensor, 8... Substrate, 9... Sensor chip, 13.15
...Optical correction means

Claims (1)

[Claims] 1. A plurality of sensor chips each having a light-receiving element arranged in an array is provided, and the back surface of the end of the next sensor chip is overlapped with the end surface of the adjacent sensor chip. What is claimed is: 1. An image sensor characterized in that light-receiving elements are arranged sequentially on a main scanning line and whose light-receiving surfaces face opposite end back surfaces of adjacent sensor chips, and are optically shielded. 2. The image sensor according to claim 1, further comprising an optical correction means having a focal length corresponding to the distance from the document surface for each light receiving element.