JPS60174570A - Image reader - Google Patents

Abstract

PURPOSE:To read an image while making invariably proper shading corrections by providing the 2nd photodetecting element in addition to the 1st photodetecting element on which an original image is formed, and detecting the basic waveform of a light quantity distribution for shading correction through the 2nd photodetecting element. CONSTITUTION:Images of reflecting plates 4 and 5 are formed on photodetection surface of photodetectig elements 8 and 7 before an original 2 reaches an original read surface 3, and the shading waveform and illuminanace of the light quantity distribution are read to store the difference in shading waveform and difference in illuminance between the elements 7 and 8 in a storage device. Then when the original 2 reaches the surface 3, an image on the original 2 on the surface 3 is formed on the element 8, and a shading correction of the output of the element 8 is performed to read the image. In this case, the shading correction is made on the basis of a reference waveform in consideration of the previously stored difference in shading waveform and difference in illuminance between the elements 7 and 8.

Description

[Detailed Description of the Invention] [Technical Field] The present invention (C) is a document reading device, more specifically, an electrical shading correction method in which reflected light from a document such as a facsimile or a copying machine is imaged on a light receiving element (H). The present invention relates to a document reading device that reads information by 1 or 1.

[Prior art]

Conventionally, when performing electrical shading correction with this type of device, just before reading the original, the reflected waveform of the white reflector plate provided as the base of the reading surface is memorized as a reference shading waveform, and the waveform is stored as a reference shading waveform while the original is being read. This is because the shading waveform is read out from memory and electrical shading correction is performed.

In addition to shading correction due to variations in the light intensity distribution, shading correction is required because the illuminance of the light source changes over time. Shading correction was performed by preventing the area from being hidden and detecting changes in illuminance in that area. Conventionally, electrical shading correction is performed using the waveform of the white reflector just before the document is read and the illuminance of the white reflector that is not covered by the document while the document is being read, but shading correction The reference waveform used for the correction differs from the illumination waveform at the time of correction, and if the difference becomes large, the correction will exceed the allowable range and become impossible.

In order to prevent this, conventional methods have been designed to shorten the time from when the reference waveform for shape ink correction is memorized until the time when a single document is read and shading correction is completed, thereby reducing the difference between the reference waveform and the actual waveform. I try not to be too different.

However, in the case of a communication device such as a facsimile, the reading speed of the document changes significantly depending on the speed of the line and the speed of the other party's machine, and it takes a long time to read one page of the document. There are cases where this occurs.

In such a case, the shading reference waveform is stored in the memory to substantially shorten the time required to read the document. However, in any case, there is a drawback that it is difficult to reset the reference waveform for shape ink correction while the original is being read.

Furthermore, if a fluorescent lamp is used as the illumination source, the ambient temperature will be 0.
At low temperatures such as °C, the waveform changes significantly immediately after lighting.
For this reason, conventional devices have drawbacks such as the need for temperature control.

〔the purpose〕

Therefore, the present invention eliminates these conventional drawbacks, and provides a document reading device that can omit complicated configurations such as temperature control, high-speed document reading, and memory installation, and can respond to changes in light intensity during document reading. The purpose is to provide

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

[First Embodiment] FIG. 1 shows the configuration of a reading section 9 in a first embodiment of the present invention.

The reference numeral 1 in the figure is, for example, an illumination device such as a fluorescent lamp, by which a document 2 to be read is sent in the direction of the arrow X in the figure by a paper feeding means (not shown). The passing document reading υ surface 3 and its vicinity are illuminated.

Further, a reflection plate 4 is disposed on the original travel path corresponding to the position of the original reading surface 3, and is also illuminated by the illumination device 1. This reflective plate 4 reads the original when there is no original 9
It is painted white to bring out the light reflected on surface 3 in its brightest state.

Further, a reflector plate 5, which is exactly the same as the above-mentioned reflector plate 4, is arranged very close to the document reading surface 3 and at a position closer to the illumination device 1 than the document 2. be done.

On the other hand, in this embodiment, two light receiving elements 7.8 are provided, and these are composed of, for example, a CCD or the like.

The image of the document reading surface 3 is displayed on one of the light receiving elements 8 through the lens 6.
An image of the reflecting plate 5 is formed on the other light receiving element 7 via the same lens 6.

Next, the operation of this embodiment configured as above will be explained.

First, before the original 2 is read, that is, before the original 2 fed by a paper feeding means (not shown) enters the original reading surface 3, the images of the reflectors 4 and 5 are reflected on the light receiving elements 8 and 7, respectively. An image is formed on each light-receiving surface, the shading waveform of the light amount distribution and the illuminance are read, and the difference in the shading waveform and the difference in illuminance between the light-receiving elements 7 and 8 are stored in storage means (not shown).

Next, when the original 2 enters the original reading surface 3, an image of the original 2 on the original reading surface 3 is focused on the light receiving element 8, and shading correction is applied to the output of the light receiving element 8. The reading is performed.

In this case, the shading correction takes into consideration the shading waveforms detected by the light receiving element 1 from time to time, and the differences in shading waveforms and illuminance between the light receiving elements 7 and 8, which are stored in advance as described above. This is done based on the reference waveform entered in the .

In particular, if the light-receiving elements 7 and 8 are used with substantially the same characteristics, the difference in the output of the pixel elements can be considered to be only the difference in illuminance resulting from the difference in the position of the pixel elements. By simply adding to or subtracting from the output difference of 7.8, shading-corrected image data can be obtained.

As described above, the shading correction according to this embodiment is performed based on the shading waveform detected by the light receiving element 7, and this shading waveform is obtained continuously or at arbitrary timing, so that the illumination amount 1 It can continuously respond to changes in light amount and illuminance.

[Second Embodiment] FIG. 2 shows the configuration of a second embodiment of the present invention. In this embodiment, the lighting device 1 and the document reading surface 3
A spectrometer 9 composed of a prism is provided on the optical path between them. .

Irradiation light l of the illumination device 1. is the cross section of the spectrometer 9, so the hypotenuse 9a
The light is separated into reflected light 1 and transmitted light 12. Of these, the reflected light 11 is guided to the light receiving element 7 via the lens 10 and is imaged on the light receiving element 7. Also, the transmitted light 12 is the original reading 9
The surface 3 is irradiated, and the reflected light is guided to the light receiving element 8 via the lens 11, and the image of the original 2 on the original reading surface 3 or the image of the reflecting plate 4 is formed on the light receiving element 8.

Even with such a configuration, the shading waveform can be constantly detected via the light receiving element 7, and the light receiving element 8 is detected based on this shaved waveform in the same manner as in the previous embodiment.
The image data can be read by applying shading correction to the output.

Further, in the case of this embodiment, it is sufficient to provide only one reflecting plate just below the document reading surface 3.

Note that the configuration of the optical system for forming an image to obtain a shading waveform on the light receiving elements 7 and 8 or an image on the document reading surface 3 is not limited to that of the above embodiment, and various configurations may be used. I can do it.

〔effect〕

As is clear from the above description, according to the present invention, a second light receiving element is provided in addition to the light receiving element (first light receiving element) on which the original image is formed, and shading is performed through the second light receiving element. Since the reference waveform of the light intensity distribution for correction is detected, the above-mentioned light intensity distribution can be detected at any time, and appropriate shading is always achieved by continuously responding to changes in the light intensity and illuminance of the illumination device during document reading. Image reading can be performed by applying shading correction using the reference waveform. Complex and expensive configurations such as temperature control, high-speed reading, and memory in this fruiting device are omitted, resulting in cost reduction and the ability to read images with high quality such as stable halftone images. is obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a reading section 9 according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram showing the construction of a reading section 9 according to a second embodiment. 1... Illumination device 2... Original 3... Original reading surface 4, 5... Reflective plate 6.10
．． 11... Lens 7, 8... Light receiving element 9... Spectrometer patent applicant Canon Co., Ltd. agent Patent attorney Takashi Kato Figure 1 Question 2

Claims (1)

[Claims] a light source that irradiates the original and the reflective member; a first light-receiving element that receives reflected light from the original that has been irradiated with the light source; and a second light-receiving element that receives the reflected light from the reflective member that has been irradiated with the light source. Particularly, a light-receiving element is provided, image information of the document is read through the first light-receiving element, and light intensity distribution for shading correction is detected through the second light-receiving element. An image reading device with a characteristic.