JPH0724851Y2 - Image reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an image reading apparatus used in a facsimile apparatus, a digital copier, an image scanner, or the like.

[Conventional technology]

In an image reading apparatus that reads an image on the image forming surface of a document by applying illumination light to the image forming surface of the document and focusing reflected light from the image forming surface on the image sensor on the image sensor, contamination of the light source and An appropriate read image may not be obtained due to secular change in the amount of emitted light.

Therefore, as proposed in JP-A-62-133860,
There is a type in which a part of the image sensor is used as a detector for detecting the amount of light emitted from the light source, and the amount of emitted light of the light source detected by the detector is feedback-controlled so as to be a predetermined amount.

Further, as proposed in Japanese Patent Laid-Open No. 62-32764, there is one that reads a reference white image at the start of reading and controls the emitted light amount so that the white level of this white image becomes a set level. is there.

[Problems to be solved by the device]

However, in the device disclosed in Japanese Patent Laid-Open No. 62-133860, the image sensor has to be larger than the reading range of the original image, so that the image sensor becomes expensive, and eventually the cost of the device increases. There is.

On the other hand, in the device disclosed in Japanese Patent Laid-Open No. 62-32764, even if the amount of light emitted from the light source changes due to a temperature change or the like during the reading operation of one document, this is set to an appropriate amount of light in real time. There is a problem that it cannot be controlled, and as a result, one original image cannot be read with a uniform density. Further, since the background color of the original is used as the reference white image, there is a problem that it is not possible to read an original with gradation such as a photograph.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus which has an inexpensive structure and can read an original image with gradation evenly.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides an image reading apparatus which irradiates a document with a light source and reads reflected light from the document with a line image sensor, and a light amount sensor for detecting the amount of light emitted from the light source, and the line image sensor. The number of bits of which the read output of each bit of the line image sensor exceeds a predetermined value while the reference white surface is being read by the light source so that the counted value falls within a preset value range. Light source optimizing means for optimizing the amount of emitted light of the light source, a non-volatile memory for storing the detection value of the light amount sensor in a state in which the amount of emitted light of the light source is optimized by the light source optimizing means, and an original by the line image sensor. The light source emits light so that the detection value of the light amount sensor is within an allowable range of the value stored in the nonvolatile memory during reading Characterized by comprising a light source control means for controlling the amount.

[Action]

According to the present invention, while the line image sensor is reading the reference white surface, the number of bits in which the read output of each bit of the line image sensor exceeds a predetermined value is counted, and the counted value is preset. The amount of light emitted from the light source is optimized by the light source optimization means so that the value falls within the range of values. Then, the detection value of the light amount sensor in the state where the light emission amount of the light source is optimized by the light source optimization means is stored in the non-volatile memory, and the detection value of the light amount sensor is stored in the non-volatile memory during the reading of the original by the line image sensor. The amount of light emitted from the light source is controlled by the light source control means so that the value is stored within the allowable range.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1a and 1b are originals 3 through the platen glass 2.
The light reflected by the image forming surface of the original 3 is imaged on the light receiving surface of the image sensor 5 by the image forming optical system 4 such as the SELFOC lens array. Reference numeral 6 denotes a platen roller having a white surface. The platen roller 6 is used to bring the original 2 into close contact with the surface of the platen glass 2 and prevent blurring of an image. 7 is a light source
A light amount sensor that detects the amount of light emitted from 1a and 1b by leaking light from a hole 9 provided in a part of the shield member 8,
The detection signal is converted into a digital value by the AD converter 10 and input to the central processing unit (CPU) 12. 11 is a non-volatile memory that stores the value of the emitted light amount detected by the light amount sensor 7 in the proper reading state, 13 is a lamp controller that drives the light sources 1a and 1b, 14 is an operation panel, and 15 is a digital value of the output of the image sensor 5. AD converter to convert to, 16
Is a line memory that stores read data of the original image in the main scanning direction for one line. The read data of the line memory 16 is subjected to shading correction and the like by the image processing unit 17 and output to the outside. Further, the read data of the line memory 16 is input to the CPU 12 via the line memory 18 of the next stage.

In the above configuration, first, the operation of setting the light quantity to the proper light quantity in the reading state will be described.

First, an instruction is input from the operation panel 14 to the CPU 12 to cause the CPU 12 to start a process for bringing it into a proper reading state. Then, the control signal is input to the lamp controller 13 and the light source
1a and 1b are turned on. Therefore, the CPU 12 reads the reflected light from the white platen roller 6 when the original 3 is not inserted in the current light emitting state of the light sources 1a and 1b through the image sensor 5, the AD converter 15, and the line memories 16 and 18. Put in. And
The density level of each pixel in one line in the main scanning direction is compared with a predetermined threshold value, and the number of pixels having a density level exceeding the threshold value is counted. Next, if this count value exceeds a predetermined set value, the light emission amounts of the light sources 1a and 1b are reduced by the lamp controller 13 by an amount corresponding to the difference from the set value. On the other hand, if it is less than the set value, the amount of emitted light is increased by the difference from the set value. If the number of pixels having the density level exceeding the threshold value falls within the allowable range of the set value by repeating such operation, it is determined that the proper reading state is obtained, and then the light emission amount in this state is determined. Move on to detection processing.

In this detection processing, the amount of light emitted from the light sources 1a and 1b (the amount of light leaked from the hole 9) detected by the light amount sensor 7 and converted into a digital value by the AD converter 10 is read, and the nonvolatile memory 11 is read.
Finish by writing in.

Such an appropriate light amount setting process is performed when the device is shipped from the factory.
Alternatively, it is performed when the light sources 1a and 1b are replaced.

When the image of the original 3 is actually read after setting the appropriate light quantity in this way, the CPU 12 reads the current value of the emitted light quantity detected by the light quantity sensor 7 in real time through the AD converter 10 when the reading is started. The light emission amounts of the light sources 1a and 1b are feedback-controlled via the lamp controller 13 so that the value is within the allowable range of the value of the appropriate light amount written in the nonvolatile memory 11.

Therefore, according to this configuration, it is not necessary to make the image sensor 5 larger than the reading width of the original image, and the cost increase of the image sensor 5 can be eliminated.
In addition, since the amount of emitted light is feedback controlled in real time during the reading operation of the original image, it is possible to obtain a read image with uniform density even if the amount of emitted light changes due to temperature changes, etc. It is also possible to read a document image with a certain margin. In the example of the prior art, it is affected when the white platen becomes dirty, but in the present invention, since the suitable light amount can be set at the time of factory shipment or at the time of cleaning the white platen,
Even if the platen becomes dirty after that, the light amount control value does not change. The light quantity sensor detects only the direct light from the lamp which is not affected by the dirt on the white platen.

When setting the proper light amount, the number of pixels in which the density of the reflected light from the white platen roller 6 exceeds the threshold value is counted, and it is determined whether the proper light amount state is reached or not by comparing the count value with the set value. However, this is because, for example, in the contact type image sensor using amorphous silicon, the variation in sensitivity between each pixel is about 30% of the average value, and it is highly accurate with only the density level of a specific pixel. This is because the light quantity cannot be set.

By the way, in the above-mentioned embodiment, the amount of light emitted from the light sources 1a and 1b is detected by the leaked light from the hole 9, but it may be directly detected in the internal space of the shield member 8. Further, it can be similarly applied to those provided with a reduction optical system and the like.

[Effect of device]

As described above, according to the present invention, the number of bits in which the read output of each bit of the line image sensor exceeds a predetermined value is counted while the line image sensor is reading the reference white surface, and the count value is counted. Is adjusted so that the light emission amount of the light source is optimized by the light source optimization means, and the detection value of the light amount sensor in a state where the light emission amount of the light source is optimized by the light source optimization means is stored in the nonvolatile memory. During reading of a document by the line image sensor, the light source control means controls the light emission amount of the light source so that the detection value of the light amount sensor falls within the allowable range of the value stored in the nonvolatile memory. Therefore, 1) the amount of light emitted from the light source can be easily adjusted to a state in which an optimum signal can be obtained from the line image sensor. 2) During the reading of a document. The amount of light emitted from the light source is also emitted light quantity is changed in the source an effect such that can be controlled in real time in a state of optimal signal from the line image sensor is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1a, 1b ... Light source, 2 ... Platen glass, 3 ... Original,
4 ... Imaging optical system, 5 ... Image sensor, 6 ... White platen roller, 7 ... Light intensity sensor, 9 ... Hole, 10, 15
... AD converter, 11 ... non-volatile memory, 12 ... central processing unit, 13 ... lamp controller, 14 ... operation panel,
16,18 …… Line memory.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Tasaki 1275 Iwatsuki, Iwatsuki City, Saitama Prefecture Inside the Iwatsuki Plant of Fuji Xerox Co., Ltd. (56) Reference JP 62-68362 (JP, A) JP A 62-279777 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. An image reading apparatus for irradiating an original with a light source and reading reflected light from the original with a line image sensor; and a light amount sensor for detecting an emitted light amount of the light source; In the reading state, the number of bits in which the read output of each bit of the line image sensor exceeds a predetermined value is counted, and the emitted light amount of the light source is adjusted appropriately so that the counted value falls within a preset value range. A non-volatile memory for storing the detection value of the light quantity sensor in a state where the light emission quantity of the light source is optimized by the light source optimization means; A light source that controls the amount of light emitted from the light source so that the detection value of the light amount sensor falls within an allowable range of the value stored in the nonvolatile memory. An original reading device comprising: a control unit.