JPH0531451U - Light source device for contact image sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a light source device of a contact type image sensor capable of significantly simplifying a manufacturing process and improving operation quality. [Configuration] LEDs at both ends of the light source device 22 in the arrangement direction
The element 24a is chosen so that its brightness is higher than the brightness of the remaining LED elements 24.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a light source device for irradiating a reading object such as a document with light in a contact image sensor.

[0002]

[Prior Art]

 FIG. 8 is an electric circuit diagram of a light source device 2 of a typical conventional contact type image sensor (hereinafter abbreviated as image sensor) 1, FIG. 9 is a plan view of the light source device 2, and FIG. 3 is a sectional view of the sensor 1. FIG. The image sensor 1 includes a plurality of LED elements 4 configured by arranging a plurality of LEDs (light emitting diodes) 3 as light sources, and each LED element 4 is linearly arranged on a wiring board 5. Current limiting resistors r1, r2, ..., rn are connected in series to each LED element 4, and these are connected in parallel to a power source 6.

The wiring board 5 is fixed in the recess 8 of the base 7 so that the LED element 4 faces inward, and the signal processing circuit 9 is mounted thereon. On the other hand, a through hole 10 through which light from the LED element 4 passes is formed in the base 7, and a glass substrate 11 is fixed in a range facing the through hole 10 at an end portion of the base 7 opposite to the wiring substrate 5. A plurality of photoelectric conversion elements (not shown) are formed on the glass substrate 11 at the positions corresponding to the through holes 10, and the light from the LED element 4 reflected from a document or the like is converted into an electric signal.

A wiring board 12 is fixed on the base 7 adjacent to the glass substrate 11, and a drive circuit element 13 for performing scanning and reading processing of the plurality of photoelectric conversion elements is arranged on the wiring board 12. The drive circuit element 13 is connected to the circuit wiring on the glass substrate 11 and the wiring substrate 12 by the bonding wire 14, and the installation area of the drive circuit element 13 and the bonding wire 14 is a protective film 15 made of silicone or a synthetic resin material. To be covered. The wiring boards 5 and 12 are connected to each other by a connector 16.

In such an image sensor 1, in order to read an optical image of a document or the like with high accuracy, the LEDs 3 of the LED elements 4 are required to generate light with uniform brightness. The first conventional example for achieving such an object is that the LED 3 and the LED element 4 manufactured by the semiconductor manufacturing technology have variations in the amount of light generated and the brightness even if the same drive voltage is applied. It is known to exist. For this reason, after the LED element 4 is manufactured, its optical characteristics are inspected and classified with high accuracy, and the LED element 4 constituting one image sensor 1 is selected to have the same optical characteristics.

In such a conventional example, there is a problem that labor is required for highly accurate inspection and classification work of the emitted light amount of all the LED elements 4, and the manufacturing efficiency is low. In such a case, the current limiting resistors r1 to rn are all selected to have the same electric resistance value.

On the other hand, each LED element 4 is allowed to have a slight variation in optical characteristics, and the current limiting resistors r1 to rn are mutually arranged so that the emitted light amount and the brightness of each LED element 4 become uniform, for example. A conventional example in which different electric resistance values are selected is known.

In this conventional example, the degree of variation in the actual optical characteristics of the LED elements 4 is determined, and a current limiting resistance r having an electric resistance value corresponding to this is selected over all the LED elements 4. Is difficult and extremely labor-intensive.

FIG. 11 is an electric circuit diagram of another conventional light source device 2a. The characteristic of this conventional example is that for each LED element 4, one LED element 4 is connected to a resistor r having a fixed electric resistance value, and the remaining LED elements 4 are respectively provided with variable resistors VR1, VR2 ,. , VRn-1 are connected. The resistance values of such variable resistors VR1 to VRn-1 are adjusted, for example, by angularly displacing the adjusting screw 17 shown by the chain double-dashed line in FIG.

That is, in this conventional example, after manufacturing the light source device 2a, the optical characteristics of the LED element 4 connected to the resistor r having a fixed resistance value are used as a reference, and the remaining LED elements 4 have variable resistances VR1 to VRn. Are used to provide uniform optical quantity and luminance and other optical characteristics. However, even in this conventional example, the adjustment work of the variable resistors VR1 to VRn-1 is required, which requires a great deal of labor and complicates the manufacturing process.

An object of the present invention is to solve the above-mentioned technical problems, to make the distribution of the emission intensity of each light emitting element uniform, to improve the operation quality, and to simplify the manufacturing process. It is to provide a light source device of a contact image sensor that can be used.

[0012]

[Means for Solving the Problems]

 The present invention provides a wiring board in which a plurality of light emitting elements that emit / extinguish light according to on / off of a driving current are linearly arranged, a housing that guides light from each light emitting element to an object to be read, and the arrangement. The light source device for a contact image sensor is characterized in that each light emitting element near both ends in the direction is selected to have higher brightness than the remaining light emitting elements.

Further, according to the present invention, a wiring board in which a plurality of light emitting elements that emit / extinguish in response to on / off of a drive current are linearly arranged, and light from each light emitting element is guided to an object to be read. A light source device for a contact image sensor, comprising: a housing; and light amount adjusting means for adjusting the amount of light emitted from the light emitting elements, which are provided in the light emitting elements near both ends in the arrangement direction, respectively.

[0014]

[Action]

 In the light source device according to the present invention, a plurality of light emitting elements linearly arranged on the wiring board emits light / extinguishes according to on / off of the drive current. At this time, in the vicinity of both ends of the arrangement direction of the light emitting elements, light is diffused in the opposite direction to the adjacent light emitting elements, so that the substantial intensity distribution of light obtained from each light emitting element is reduced near the both ends. Therefore, when the light emitting elements near the both ends in the arrangement direction are selected to have higher luminance than the remaining light emitting elements, it is possible to cancel the diffusion of the light and make the light intensity distribution of each light emitting element uniform. As a result, the operation quality is significantly improved.

Further, according to the present invention, a physical adjusting means is not required for adjusting the brightness of each light emitting element, whereby the adjusting work is unnecessary and the manufacturing process can be simplified.

Further, light amount adjusting means for adjusting the light emission amount and the brightness of the light emitting devices are respectively provided only to the light emitting devices near the both ends in the arrangement direction where the substantial light intensity distribution is lower than the remaining light emitting devices. Set up. According to this, although it takes time and effort to adjust the light amount adjusting means, the light amount adjusting means only needs to be connected to the light emitting elements near both ends in the arrangement direction of the light emitting elements. Compared with the conventional example in which the means is provided, the manufacturing process is greatly simplified, and the number of parts of the variable resistance element having a more complicated structure than the normal resistance element can be significantly reduced, and the structure is simplified. And cost reduction can be achieved at the same time.

[0017]

【Example】

 1 is an electric circuit diagram showing a configuration of a light source device 22 of an image sensor 21 according to an embodiment of the present invention, FIG. 2 is a block diagram of the entire image sensor 21, and FIG. 3 is a plan view of the light source device 22. FIG. 4 is a cross-sectional view of the image sensor 21. The light source device 22 of the image sensor 21 includes a plurality of LED elements 24 configured as an integrated circuit element in which a plurality of LEDs (light emitting diodes) 23, which are light emitting elements, are arranged in a straight line. In each LED element 24, each LED 23 is connected in series in series, for example, the anode side is connected to the positive electrode of the power supply 25, and the cathode side is connected to the negative electrode side of the power supply 25. , Rn, which are current limiting resistors, are connected in series on the negative electrode side of each LED element 24, and each LED element 24 and a resistor Ri (i = 1 to n) are connected in series. The circuit is connected in parallel with the power supply 25.

The image sensor 21 is provided with a reading unit 26 that photoelectrically converts and reads the reflected light from the reading object illuminated by the light source device 22. The reading unit 26 is provided with a sensor substrate 27 in which a large number of photoelectric conversion elements (not shown) that receive reflected light from the object to be read and photoelectrically convert the reflected light are arranged. Then, each photoelectric conversion element is sequentially scanned and a signal is read. The read signal is subjected to waveform shaping processing in the signal processing circuit 29 and output. A large number of the LED elements 24 are arranged on the wiring board 30 shown in FIG. 4 in the direction perpendicular to the paper surface of FIG. 4, and the signal processing circuit 29 is provided on the back surface of the wiring board 30.

The wiring board 30 is fixed to a base 32 having a recess 31 so that the LED element 24 faces the inside. A glass substrate 33 is fixed on the side opposite to the wiring substrate 30 of the base 32, and the plurality of photoelectric conversion elements described above are linearly arranged on the glass substrate 33. A through hole 34 through which light from the LED element 24 passes is formed in the base 32 at a portion corresponding to a region where the photoelectric conversion element is formed. On the base 32, a wiring substrate 35 having the scanning circuit 28 and the circuit wiring is formed adjacent to the glass substrate 33 is fixed, and is provided between the photoelectric conversion element on the glass substrate 33 and the scanning circuit 28. The circuit wiring on the wiring board 35 and the scanning circuit 28 are connected by bonding wires 36, respectively, and the wiring boards 30, 35 are connected by a connector 37. The area where the scanning circuit 28 and the bonding wire 36 are installed is covered with a protective film 38 made of silicone or a synthetic resin material.

The inventor of the present invention measured the output of the image sensor 21 when a reference white original was read using the conventional light source device shown in FIG. The result is shown in line L1 of FIG. That is, in addition to the fluctuation of the output caused by the variation of the optical characteristics of the LEDs constituting the light source device, the output of the image sensor is reduced in the arrangement direction of the LEDs 23, that is, in the vicinity of both ends of the image sensor 21 in the main scanning direction. A characteristic phenomenon was confirmed. This phenomenon does not depend on variations in the optical characteristics of the LEDs 23, but the LEDs 23 arranged in a straight line on the wiring board 30 as shown in FIG. While the light from the LEDs 23 adjacent in the array direction is included in the light source, the light source substantially emits light to the object to be read, while there is no LED 23 near both ends in the array direction near the free end in the array direction. This is because the light of the LED 23a near the end portion diffuses outward in the arrangement direction.

Therefore, in the present embodiment, among the LED elements 24 on the wiring board 30 shown in FIG. 3, the LEDs 23a at both ends in the arrangement direction have higher brightness than the remaining LEDs 23 for the same current value. Try to choose the type.

In this embodiment, the variation in the brightness of the LED element 24 was measured. In this measurement, coated paper having an OD value (optical density) of 0.07 is read by an image sensor, and the variation amount PRNU is defined by the following equation using the maximum value Vwa and the minimum value Vwb of the read output shown in FIG.

[0023]

[Equation 1]

As an example of the image sensor 21 having a size corresponding to Japanese Industrial Standards (JIS) A-row No. 4, that is, a total length of 216 mm in the main scanning direction, the entire luminance range is shown in Table 1 below based on the measurement results. It was divided into 3 groups G1, G2 and G3.

[0025]

[Table 1]

(1) Configuration Example 1 Based on the above-mentioned findings relating to FIG. 5, the inventor of the present invention described the LED element 24 shown in FIG. A configuration example was selected in which the second LED group 24 is selected from the second group G2 shown in No. 1 and the remaining LED elements 24 are selected from the first group G1. In addition, when the LED elements 24 other than the LED elements 24 at both ends in the arrangement direction are selected from the second group G2 in Table 1, the LED elements 24 at both ends are selected from the third group G3. Therefore, the current limiting resistors R1 to Rn are all selected to have the same electric resistance value. In the image sensor 21 using the light source device 22 having such a configuration example, the distribution of the variation amount PRNU is shown in the column of Example 1 in Table 2 below.

[0027]

[Table 2]

(2) Configuration Example 2 All the LED elements 24 are selected from the second group G2 shown in Table 1, and the resistance value R1 = Rn, the resistance value R2 = R3 = ... = Rn−1 with respect to the current limiting resistance. , R 1 / R 2 = 0.8. That is, although the optical characteristics of each LED element 24 are substantially uniform, the LED elements 24a at both ends in the arrangement direction have the remaining brightness when emitting light by selecting different resistance values of the current limiting resistors R1 to Rn. The number of elements is set to be larger than that of the element 24. The measurement result of the variation amount PRNU using the light source device 22 having such a configuration example is shown in Example 2 of Table 2 above.

(3) Configuration Example 3 As a conventional configuration example described with reference to FIG. 8, all the LED elements 24 are selected from the second group G2 in Table 1 and the current limiting resistors R1 to Rn are all equal. The measurement result in that case is shown in Example 3 of Table 2 above.

In the image sensor 21 using a plurality of LED elements 24, it is desirable that the value of the variation amount PRNU be ± 30% or less. Therefore, in the above-mentioned configuration examples shown in Example 1 and Example 2 of Table 2, it was confirmed that the variation amount PRNU was improved by ± 4 to ± 6%, and the variation amount of ± 30% or more was almost eliminated.

Therefore, in the present embodiment, it is possible to prevent the occurrence of uneven brightness of the light source light from the light source device 22, and it is possible to remarkably improve the operation quality of the light source device 22. Further, in any of the above configuration examples, the inconvenience of using a variable resistor having a mechanical adjustment mechanism as described in the conventional example is solved, the number of parts and the cost can be reduced, and the adjustment process is not necessary. The manufacturing process can be greatly simplified.

FIG. 7 is an electric circuit diagram showing a configuration example of another embodiment of the present invention. This embodiment is similar to the above-mentioned embodiment, and corresponding parts are designated by the same reference numerals. In the light source device 22a of the present embodiment, regarding the current limiting resistors connected to each LED element 24, the ones connected to the LED elements 24a located at both ends in the arrangement direction are variable resistors VR1 and VR2, and the remaining The resistors connected to the LED element 24 are resistors R1, R2, ...

In this embodiment, all the LED elements 24 including the LED elements 24a at both ends in the arrangement direction are selected from any one of the groups G1, G2 and G3 in Table 1 above. After that, the resistance values of the variable resistors VR1 and VR2 are reduced from the resistance values of R1, R2, ..., In order to obtain the same brightness in all the LED elements 24.

That is, even with such a configuration example, the same effect as the effect described in the above-described embodiment can be achieved.

[0035]

[Effect of the device]

 As described above, in the light source device according to the present invention, when the light emitting elements near the both ends of the arrangement direction are selected to have higher luminance than the remaining light emitting elements, the light diffusion is canceled out and the light intensity distribution by each light emitting element is made uniform. can do. As a result, the operational quality is significantly improved. Further, according to the present invention, no physical adjusting means is required to adjust the brightness of each light emitting element, which eliminates the need for adjusting work and simplifies the manufacturing process.

Further, light amount adjusting means for adjusting the light emission amount and the brightness of the light emitting device are respectively provided only to the light emitting devices near the both ends in the arrangement direction where the substantial light intensity distribution is lower than the remaining light emitting devices. Set up. According to this, although it takes time and effort to adjust the light amount adjusting means, the light amount adjusting means only needs to be connected to the light emitting elements near both ends in the arrangement direction of the light emitting elements. Compared with the conventional example in which the means is provided, the manufacturing process is greatly simplified, and the number of parts of the variable resistance element having a more complicated structure than the normal resistance element can be significantly reduced, and the structure is simplified. It is possible to reduce the number of parts of the variable resistance element and reduce the cost.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a light source device 22 according to an embodiment of the present invention.

FIG. 2 is a block diagram of an image sensor 21.

FIG. 3 is a plan view of a light source device 22.

FIG. 4 is a cross-sectional view of the image sensor 21.

FIG. 5 is a graph showing a level distribution of light reading output by each LED element.

FIG. 6 is a graph illustrating the operation of this embodiment.

FIG. 7 is an electric circuit diagram of another configuration example of the present invention.

FIG. 8 is an electric circuit diagram of a first conventional example.

9 is a plan view of the light source device 2. FIG.

FIG. 10 is a cross-sectional view of the image sensor 1.

FIG. 11 is an electric circuit diagram of another conventional light source device 2a.

[Explanation of symbols]

 21 image sensor 22 light source device 23 LED 24 LED element R1 to Rn current limiting resistor VR variable resistor

Claims (2)

[Scope of utility model registration request] 1. Light emission / corresponding to ON / OFF of drive current
A wiring board in which a plurality of light emitting elements to be extinguished are linearly arranged, a housing that guides light from each light emitting element to an object to be read, and each light emitting element near both ends in the arrangement direction has higher brightness than the rest of the light emitting elements. The light source device of the contact type image sensor, which is characterized in that 2. Light emission / corresponding to ON / OFF of drive current
A wiring board in which a plurality of light-emitting elements to be extinguished are linearly arranged, a housing for guiding light from each light-emitting element to an object to be read, and a light-emitting amount of the light-emitting element is adjusted for each light-emitting element near both ends in the arrangement direction. A light source device for a contact image sensor, characterized in that each light amount adjusting means is provided.