JPH04154259A - Complete contact type image sensor - Google Patents

Abstract

PURPOSE:To eliminate the necessity of memory and white level from an image sensor by using the first sensor section to read reflected light from an original, by using the second sensor section to directly read only light of a light source to detect the variation of illumination of the light source, and using an external circuit to take a ratio of output signals of two sensors. CONSTITUTION:The preset image sensor consists of a glass substrate 1, sensors 2, and 3, and a LED 4, and further as an external circuit the present image sensor has amplifiers 6A and 6B and an external circuit 7. In this case, sensor section 2 reads reflected light from an original while sensor section 3 directly reads only light of light source to detect the variation of illumination of light source, and the external circuit 7 takes a ratio of output signals of two sensors to carry out shading compensation. With this, the present image sensor requires no memory, can track secular change of illumination, and further when detecting the variation of illumination, the present image sensor need not have a complex mechanical section necessary to read a white level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contact type image sensor used as a reading section of a small facsimile, an image scanner, etc., and particularly relates to a complete contact type image sensor that is in complete contact with a document.

[Conventional technology]

FIG. 4 shows a principle diagram (cross-sectional view in the sub-scanning direction) of a conventional complete contact type image sensor. In Fig. 4, 1 is a glass substrate, 2 is a reading sensor section, and 4 is an LED (Light).
t Emitting Diode), 5 is the manuscript. In this way, the LED 4 is provided on the opposite side of the original 50 with the glass substrate 1 in between, and the light from the LED 4 is transmitted through the glass substrate 1 and irradiated onto the original, and the sensor unit 2 reads the reflected light. .

Both the sensor 2 and the LED 4 are arranged in an array in one row in the scanning direction.

Here, the illuminance of the LED array on the document surface has some variation in the scanning direction (shading: usually ±30%).
(degree) occurs, so a means to correct this is required. A block diagram of a conventional shading correction circuit is shown in FIG. 5. In the conventional shading correction method, first, by reading a white reference (a white board used as a reference when measuring illuminance), individual LEDs are After detecting the illuminance variation on the document surface, the correction coefficient for correcting this is stored in ROM (Read Only Memory) or RAM (Random Access Mes+or
y), in this example, is stored in the ROM 12, and the integrated δ
13, this and A (Analog) / D (D
igital) A method is adopted in which the product is multiplied by the sensor output signal outputted via the converter 11 and output.

[Problem to be solved by the invention]

This conventional shading correction method requires memory to store correction coefficients for LED illuminance variations, and usually uses ROM, but in this case, it is not possible to follow changes in illuminance variations over time. There is a problem. Furthermore, when a RAM is used and data can be rewritten at any time, the problem arises that the white reference becomes dirty because the white reference is read while being in complete contact with the sensor each time. Furthermore, an extra mechanical part is required to incorporate the white reference.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks and provide a fully contact type image sensor that does not require a memory or a white reference.

[Means for Solving the Problems] The present invention provides a fully contact image sensor that uses a light source attached to one surface of a glass substrate to shine light onto the document surface through the glass substrate, and reads the reflected light. , a first sensor section that is provided on the other side of the glass substrate, is in close contact with the document, and reads reflected light from the document using a charge storage type photodiode; A second sensor unit is provided on the other side of the glass substrate and is in close contact with the original, and directly reads the light from the light source, and the ratio of the signals from the first and second sensor units is calculated and output. It is characterized in that it has an output section.

[Function] The present invention uses a charge accumulation type sensor section using a photodiode, and further includes a second sensor section for shading correction, separate from and adjacent to the sensor section for reading an original. The former sensor section reads the reflected light from the document, while the latter sensor section directly reads only the light source light to detect variations in the illuminance of the light source, and an external circuit calculates the ratio of the output signals of the two sensors. By taking the following values, shading correction can be performed.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view in the sub-scanning direction showing an embodiment of the present invention, and FIG. 2 is a block diagram of a shading correction mechanism with respect to FIG. 1. Note that FIG. 1 is also a diagram of the principle.

This complete contact type image sensor includes a glass substrate 1, sensor sections 2 and 3, and an LED 4, as shown in FIG. Furthermore, as shown in FIG. 2, an amplifier 6A is provided as an external circuit.

6B and an external circuit 7.

Such a complete contact type image sensor has two rows of sensor arrays on the same substrate. By using a charge accumulation type sensor using a photodiode in the sensor array, that is, the sensor section 2.3, output characteristics with good uniformity and faithful to the light intensity can be obtained.

The sensor unit 3 is a sensor provided for shading correction, and directly reads only the light from the light source to detect variations in illuminance of the light source. Here, by arranging two rows of sensor arrays close to each other and in close contact with the original, it can be considered that the variation in illuminance on the original surface is almost the same as the variation in illuminance read by the correction sensor array.

At the same time, the sensor section 2 reads the reflected light from the document, and at the same time, the sensor section 3 directly reads only the light from the light source, detects variations in the illuminance of the light source, and uses the external circuit 7 to calculate the ratio of the output signals of the two sensors. , shading correction can be performed.

The external circuit 7 is a circuit that calculates the ratio of the sensor output signals of the two sensor sections 2 and 3 and outputs the ratio.

FIG. 3 is a more detailed cross-sectional view of FIG. 1 in the sub-scanning direction. In Fig. 3, 1 is a glass substrate, 4 is an LED, and 5 is a glass substrate.
is the manuscript. In addition, the sensor section 2゜3 is made of Cr8, a-
Three layers, 3i:H9 and ITOIO, are formed as thin films, and an a-3i photodiode is constructed by a Schottky junction of ITOIO and a-3i:H9.

The document reading sensor section 2 and the shading correction sensor section 3 are configured so that the window (ITO) side of the sensor is in the direction in which light enters.

In addition, the interval between the two rows of sensor arrays is 10 [μm],
Further, by setting the distance between the sensor array and the document to 50 [μm], it can be considered that the variation in illuminance on the document surface is almost the same as the variation in illuminance read by the correction sensor array.

Shading correction can be realized using the sensor section with the above configuration and an external circuit that calculates the ratio of the two sensors.

〔Effect of the invention〕

As explained above, in the present invention, a sensor surface is brought into close contact with a document, and a light source attached to the back side of the sensor surface with a glass substrate in between is used to transmit light through the glass substrate and illuminate the document surface, and the reflected light is In a fully contact image sensor that uses a sensor to read the image, the sensor part uses a charge storage type photodiode, and in addition to the sensor that reads the reflected light from the document, a second sensor that directly reads the light from the light source is installed on the same substrate. The sensor is disposed close to the top, and is further provided with an external circuit that calculates the ratio of both sensor output signals and outputs the ratio.

As a result, the present invention does not require position adjustment of LEDs, can use light sources with large illuminance variations, and can reduce the number of man-hours for sorting LEDs. It has the advantages of not requiring memory, being able to track changes in illuminance over time, and eliminating the need for complicated mechanical parts required to read the white reference when detecting variations in illuminance.

Furthermore, in the present invention, since the two sensor sections are simultaneously formed on the same substrate, there is an advantage that the size can be reduced as in the conventional sensor without increasing the number of manufacturing steps.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view in the sub-scanning direction showing an embodiment of the present invention, FIG. 2 is a block diagram of a shading correction mechanism for the embodiment of FIG. 1, and FIG. 3 is a more detailed sub-scanning diagram of the embodiment of FIG. 1. FIG. 4 is a cross-sectional view in the sub-scanning direction showing an example of a conventional fully contact type image sensor. FIG. 5 is a block diagram of a conventional shading correction circuit. 1... Glass substrate 2... Original reading sensor section 3... Shading correction sensor section 4...
・LED 5...Original 6A, 6B・Amplifier 7...External circuit 8...Cr 9...a-3i:H 10...ITO

Claims (1)

[Claims] (1) In a full contact image sensor, a light source attached to one side of the glass substrate shines light through the glass substrate onto the document surface and reads the reflected light. a first sensor section that is provided and in close contact with the document and uses a charge storage type photodiode to read reflected light from the document; A second sensor section that is provided and in close contact with the document reads the light from the light source directly, and an output section that calculates the ratio of signals from the first and second sensor sections and outputs the ratio. Fully contact type image sensor.