JPH04309063A - Image sensor and image sensor unit using the same - Google Patents

Abstract

PURPOSE:To improve the resolution in the subscanning direction and to simplify the adjustment of a lens by providing two sets of optical sensor arrays and subtracting a video signal of the 2nd optical sensor array from a video signal of the 1st optical sensor array to obtain a video signal. CONSTITUTION:Optical sensor arrays 1, 2 are provided and a video signal of the 2nd array is subtracted from a video signal of the 1st array and an angle between an original and an image forming lens is set to be 30-60 deg.. That is, the 1st optical sensor array 1 is used for original read and the 2nd optical sensor array 2 is placed before the 1st optical sensor array 1 in the subscanning direction and a video signal of the 2nd optical sensor array is subtracted from a video signal of the 1st optical sensor array 1 to obtain a video signal as an image sensor 30. The image sensor 30 and a lighting light source are placed above the original and the image forming lens leading the reflected light from the original to the optical sensor arrays 1, 2 is tilted with respect to the original. Thus, let a deviation of the image forming lens be L and that of the original be l, the relation of l=LX(sin(theta)) is obtained and the alignment accuracy is substantially relaxed by 1/sin(theta).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor and an image sensor unit for optically reading document information.

0002

2. Description of the Related Art In recent years, image sensors for reading originals have been developed for use in image input for facsimiles, office equipment, digital copying machines, and the like.

An example of the above-described conventional image sensor and image sensor unit will be described below with reference to the drawings.

FIG. 6 shows the basic configuration of a conventional image sensor. In FIG. 6, 101 is a photosensor array, 102 is a scanning circuit, and 103 is a video signal output line. FIG. 7 shows the basic configuration of a conventional contact type reading image sensor unit, in which 110 is an image sensor, 111 is an imaging lens, 112 is an LED array for illumination, and 113 is a document. The operation of the image sensor and unit configured as above will be described below.

First, optical sensors 101a, 101b, and 101c constituting optical sensor array 101 are arranged at regular intervals. For example, if the resolution is 8 lines/mm, it is 125 μm.
spaced apart, each photosensor operates in a charge accumulation mode. These optical sensors are sequentially accessed by a scanning circuit 102, and a video signal corresponding to the amount of light irradiated for a certain period of time (referred to as an integral time) is output to a video signal output line 103. Further, in FIG. 7, light is irradiated from the LED array 112 onto the original 113, and the light reflected by the original passes through the imaging lens 111 and reaches the image sensor 110. Reflected light corresponding to the density of characters and images on the original is photoelectrically converted by each optical sensor, and original information is obtained as an electric signal in time series. FIG. 8 shows time-series electrical signals. 12 in the diagram
0 is a document pattern in the sub-scanning direction, which is a 4LP/mm document in which black and white patterns are drawn at a pitch of 125 μm. An ideal video signal for this pattern is shown at 121. It is 0 for black and 1 for white, but in reality, the video signal is as shown at 122 in the in-phase and 123 in the out-phase. In the out phase, black and white cannot be read at all.

[0006] (For example, "Sensor Technology" Vol. 5 No. 9 3
(pages 1-43)

[0007]

[Problems to be Solved by the Invention] However, in the above configuration, since the optical sensor operates in charge accumulation mode, the integrated amount of light irradiated within the integration time becomes the video signal, so This has a problem in that the resolution in the sub-scanning direction is reduced.

Another problem with the image sensor unit is that precision is required for positioning the imaging lens.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a unit that allows easy positioning of an image sensor and an imaging lens that corrects the reduction in resolution in the sub-scanning direction.

0010

[Means for Solving the Problems] In order to solve the above problems, an image sensor of the present invention and an image sensor unit using the same are provided with two rows of optical sensor arrays, and the optical sensor array of the first row is used to read a document. The second row of optical sensor arrays is installed in front of the first row of optical sensor arrays in the sub-scanning direction, and the video signal of the second row of optical sensor arrays is subtracted from the video signal of the first row of optical sensor arrays. An image sensor that obtains a video signal and an illumination light source are installed above the original, and an imaging lens that guides reflected light from the original to a photosensor array is tilted with respect to the original.

[0011]

[Operation] With the above-described configuration, the present invention subtracts the information of the previous line from the information of the target pixel to be read in the sub-scanning direction, thereby emphasizing the boundaries between black and white and light and dark of the document, and thereby improving the fundamental resolution of the charge accumulation mode. It becomes possible to reduce and correct the decrease. Further, if the angle between the document and the imaging lens is θ, the alignment accuracy increases by a factor of (1/SINθ), allowing easy alignment.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image sensor according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration diagram of an image sensor according to an embodiment of the present invention. In FIG. 1, 1 is a first row optical sensor array, 2 is a second row optical sensor array, 3 is a scanning circuit, and 4 is a video signal output line.

The operation of the image sensor configured as described above will be explained with reference to FIG. Below resolution 8
The case of books/mm will be explained. first row optical sensor array 1,
The second row photosensor array 2 is 125 μm in the main scanning direction.
Photosensors 1a, 1b, 1c, 2a, 2b, and 2c are arranged at intervals, and a second row photosensor array is arranged 125 μm ahead in the sub-scanning direction. Odd-numbered access signal lines (3o, 3e) from the scanning circuit 3 access the second column optical sensor array, and even-numbered access signal lines access the first column optical sensor array. When the scanning circuit 3 sequentially accesses the video signal output line 4, the optical sensor 2a → 1a → 2b → 1b → 2c →
1c→, the second row photosensor array, the first row photosensor array, the video signal output is obtained alternately, (1a-2a), (1b
-2b), (1c-2c), and the amount obtained by subtracting the video signal output of the second row photosensor array from the video signal output of the first row photosensor array is defined as a video signal.

The resolution performance in the sub-scanning direction of the video signal obtained with the above configuration will be explained with reference to FIG. In the figure, numeral 10 indicates a pattern of the original in the sub-scanning direction, which is a 4LP/mm original in which black and white patterns are drawn at a pitch of 125 μm. 11 and 12 are amounts of light reaching the second row photosensor array and the first row photosensor array, respectively. 13, 14
are the video signal outputs obtained by subtracting the video signal output of the second row photosensor array from the video signal output of the first row photosensor array in the case of in-phase and out-phase, respectively. Even when the video signal output 14 is out of phase, it becomes a signal that allows the difference in density between black and white to be confirmed when compared with the video signal output 123 in FIG.

In other words, it is possible to realize an image sensor that corrects the fundamental reduction in resolution in the sub-scanning direction in the charge accumulation mode. It is effective to set the light receiving area of the second row photosensor in the sub-scanning direction to about half of the light receiving area of the first row photosensor.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a basic configuration diagram of an image sensor showing a second embodiment of the present invention. 20 is a first row optical sensor array, 21 is a second row optical sensor array, 2
2 is a scanning circuit, and 23 and 24 are video signal output lines.

The operation of the image sensor configured as described above will be explained with reference to FIG. The first row optical sensor array 20 and the second row optical sensor array 21 are the same as those shown in FIG. The access signal line of the scanning circuit 22 is wired such that the first row optical sensor and the second row optical sensor are accessed at the same time. Further, video signal output lines are provided independently for the first row optical sensor array and the second row optical sensor array. The operation is almost the same as the first embodiment, and the difference is that the video signal outputs of the first row optical sensor array and the second row optical sensor array are generated at the same timing; The same effect can be obtained by means of obtaining (sensor output) - (second row optical sensor output)}.

A third embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a basic configuration diagram of an image sensor unit showing a third embodiment of the present invention. 30 is an image sensor, 31 is an imaging lens, 32 is an illumination LED, and 33 is a document.

[0020] The illumination LED 32 is located above the document,
The original 33 and the image sensor 30 are positioned parallel to each other. The original and the imaging lens are tilted (angle θ) as shown in the figure. FIG. 5 shows a diagram when the position of the imaging lens is shifted. 31' is an imaging lens in case of misalignment, L is the amount of the misalignment, and l is the amount of misalignment in the direction perpendicular to the document. The relationship between L and l is l=L×(SIN(θ)), which effectively reduces the precision of 1/SIN(θ) times the mounting, making it easier to implement.

[0021]

As described above, the present invention provides two rows of optical sensor arrays, the first row of optical sensor arrays is used for reading documents, and the second row of optical sensor arrays is used as a sub-row of the first row of optical sensor arrays. It is installed in the front direction of the scanning direction, and by subtracting the video signal of the second row photosensor array from the video signal of the first row photosensor array to obtain a video signal, it can sub-scan a black and white document pattern with the same pitch as the photosensor. Even in the direction and out-phase, a recognizable black and white video signal output can be obtained. In addition, the image sensor and illumination light source are installed above the document, and the imaging lens that guides reflected light from the document to the photosensor array is tilted relative to the document, which eases the positional accuracy of the lens. It becomes easier.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of an image sensor in a first embodiment of the present invention.

FIG. 2 is a video signal output diagram for explaining the operation in the same embodiment.

FIG. 3 is a basic configuration diagram of an image sensor in a second embodiment of the present invention.

FIG. 4 is a basic configuration diagram of an image sensor unit in a third embodiment of the present invention.

FIG. 5 shows displacement of an imaging lens in an image sensor unit according to a third embodiment of the present invention.

FIG. 6 is a basic configuration diagram of a conventional image sensor.

FIG. 7 is a basic configuration diagram of a conventional image sensor unit.

FIG. 8 is a video signal output diagram for explaining the operation of a conventional image sensor.

[Explanation of symbols]

1 First row photosensor array 2 Second row photosensor array 3 Scanning circuit 4 Video signal output line 10 Original black and white pattern 11 Amount of light reaching the first row photosensor array 12
Amount of light reaching the second row photosensor array 13 Video signal output 14 obtained by subtracting the video signal output of the second row photosensor array from the video signal output of the first row photosensor array in the case of in-phase. Video signal output 30 obtained by subtracting the video signal output of the second row photosensor array from the video signal output of the first row photosensor array Image sensor 31 Imaging lens 31' Imaging lens 32 in case of positional deviation
Illumination LED 33 Original θ Angle between original and imaging lens

Claims (6)

[Claims] 1. An image sensor comprising an optical sensor array for reading originals and a scanning circuit for scanning each optical sensor, in which two rows of optical sensor arrays are provided, the first row of optical sensor arrays is used for reading originals, and the second row of optical sensor arrays is used for reading originals. A row of optical sensor arrays is installed in front of the first row of optical sensor arrays in the sub-scanning direction, and a video signal is obtained by subtracting a video signal of the second row of optical sensor arrays from a video signal of the first row of optical sensor arrays. An image sensor featuring: 2. The image sensor according to claim 1, wherein the image signal is obtained by scanning the optical sensors in each column alternately. 3. The image sensor according to claim 1, wherein the difference between the video signal outputs of the optical sensor arrays in each column is used as the video signal. 4. The image sensor according to claim 2, wherein the light receiving area of the photosensors in the second row photosensor array is half of the light receiving area of the photosensors in the first row photosensor array. 5. A unit comprising a document reading optical sensor array, an illumination light source, an imaging lens, and a base,
An image sensor unit characterized in that an illumination light source is installed above a document, and an imaging lens that guides reflected light from the document to a photosensor array is tilted with respect to the document. [Claim 6] The imaging lens is set at an angle of 30 to 60 degrees with respect to the original.
6. The image sensor unit according to claim 5, wherein the image sensor unit is tilted.