JPH0451775A - Picture reader - Google Patents

Abstract

PURPOSE:To eliminate shading distortion of a light source included in a picture signal in an excellent way by giving a reflected light from a standard white level board to a 2nd photoelectric conversion element so as to generate a picture signal having shading distortion information therefrom. CONSTITUTION:An original 3 is fed to a sample-and-hold circuit 13 as a picture signal. The sample-and-hold circuit 13 gives the signal to an A/D converter 15 as an analog signal. Moreover, a light radiating from a light source 4 strikes on a standard white level board 5, and a 2nd photoelectric conversion element 11 receiving the reflected light gives the information as to intensity distribution of the light from the light source 4 to a sample-and-hold circuit 14. The sample- and-hold circuit 14 gives the information to the A/D converter 15 as a reference voltage. The A/D converter 15 corrects shading distortion by using an output signal from the sample-and-hold circuit 14 as a reference voltage used when a picture signal is converted into a digital signal.

Description

[Detailed description of the invention]

[Industrial application field] The present invention relates to an image reading device.

[Conventional technology]

It is well known that various configurations have been proposed for image reading devices that use photoelectric conversion elements to photoelectrically convert light from a subject into electrical signals for each pixel. be. ! Issue 111 to be solved by the invention By the way, when an image reading device reads a document,
If the light from the light source used to illuminate the original has an uneven intensity distribution, shading distortion corresponding to the uneven intensity distribution of the light from the light source will occur in the read image signal. In many cases, a decoding distortion removing means is provided, but the signal distortion correcting device in conventional devices has a complicated structure, for example, using a memory.

[Means for solving problems]

The present invention provides means for applying reflected light from a document irradiated with light from a light source to a first photoelectric conversion element via a first imaging optical system, and means provided at a position where the light from the light source is always applied. Comes with standard white board. The light reflected from the standard white plate by the light from the light source described above is
and means for correcting the output of the first photoelectric conversion element based on the output signal of the second photoelectric conversion element. An image reading device is provided.

[Effect 1] The reflected light from the document irradiated by the light emitted from the light source is applied to the first photoelectric conversion element, which is equipped with an element with the number of pixels to generate a regular image signal, to generate a regular image signal. let Further, the second photoelectric conversion element, which may have a smaller number of elements than the first photoelectric conversion element, converts the reflected light from the standard white plate provided at a position where the light from the light source is always applied. , an image signal having shading distortion information is generated, and the shading distortion in the output signal from the first photoelectric conversion element is corrected by the image signal having the shading distortion information. Thereby, shape-in distortion of the light source in the image signal generated from the first photoelectric conversion element is effectively removed. Embodiments The specific contents of the image reading apparatus of the present invention will be explained in detail below. 1 and 2 are block diagrams of different embodiments of the image reading apparatus of the present invention, and FIG. 3 is a waveform diagram for explaining the operation. In FIGS. 1 and 2, 1 is the body of the reading device, 2 is the document table, 3 is the document, 4 is the light source, 5 is the aS white plate, 6 to 8
, 17 to 19 are reflecting mirrors, 9 and 10 are lenses, and 11 is a second
12 is a first photoelectric conversion element, 13.1
4 is a sample hold circuit, 15 is an analog-to-digital conversion circuit, and 16 is an output terminal. In the image reading device shown in FIGS. 1 and 2, a first photoelectric conversion element 12 and a second photoelectric conversion element 1
For example, a CCD line sensor (CCD line image sensor) may be used as the first sensor.
As the photoelectric conversion element 12, one configured with a large number of elements capable of generating high-resolution image signals is used, and as the second photoelectric conversion element 11, the above-mentioned first photoelectric conversion element is used. A structure having fewer elements than element 12 is used. In the image reading apparatus shown in FIGS. 1 and 2, during the 1MM3C reading operation, for example, the optical system is moved at a predetermined moving speed in the space below the document table 2 by a transport mechanism (not shown). Or, for example, the document table 2 on which the document 3 is set is moved at a predetermined transfer speed by a transfer mechanism (not shown), so that the document 3 is read and scanned. There is. The standard white plate 5 is provided at a position where it is always illuminated by the light from the light source 4, and the reflected light from the standard white plate 5 contains information indicating the intensity distribution of the light from the light source 4. First, in the image reading device shown in FIG.
When the reading operation of the original 3 is performed, the light emitted from the light source 4 illuminates the original 3 through the original platen 2, and the reflected light generated on the original 3 is reflected from the reflecting mirror 6 → reflection II 7 →
The light is incident on the imaging lens 9 through the optical path of the reflecting mirror 8→. Then, the image information of the original 3 is imaged on the first photoelectric conversion element 12 by the above-mentioned imaging lens 9, and the first photoelectric conversion element 12 outputs a high-resolution image signal ( (see (a) in FIG. 3) is sent out and supplied to the sample and hold circuit 13. Note that Pr, Pr, . . . in FIG. 3(a) are waveforms that appear due to a reset pulse with a period of A. The above-mentioned sample hold circuit 13 converts the image signal of the document 3 generated by the first photoelectric conversion element 12 supplied thereto and shown in FIG. 3(a) into the image signal shown in FIG. 3(b). Sample and hold pulse P1 illustrated
The output signal 5shl is sampled and held as shown in FIG. 3(c), and is supplied to the analog-to-digital converter 15 as an input analog signal. Further, the light emitted from the light source 4 irradiates the S semi-white plate 5 and also irradiates the original 3 on the original table 2. The reflected light from the semi-white plate 5 having information on the intensity distribution of the light from the light source 4 described above is transmitted to the second photoelectric conversion element 1 by the lens 10.
1, the second photoelectric conversion element 11 focuses on the light source 4.
An image signal having information on the light intensity distribution ((d) in Figure 3)
)) and sends it to the sample and hold circuit 14.
give to The above-mentioned sample and hold circuit 14 receives an image signal (in the figure) having information about the intensity distribution of the light from the light source 4 as illustrated in FIG. 3(d), which is generated by the second photoelectric conversion element 11. Pr. (Pr... indicates the waveform appearing by the reset pulse of period B) is sampled and held by the sample-hold pulse P2 illustrated in (e) of Fig. 3. Output signal 5s illustrated in (f)
h2 is generated and supplied to the analog-to-digital converter 15 as a reference voltage. In this way, the analog-to-digital converter 15 has a reference voltage that is used when converting the image signal of the original 3 output from the first photoelectric conversion element 12 into a digital signal.
Since the output signal 5sh2 from the sample and hold circuit 14, that is, the voltage that is changing according to the information on the intensity distribution of light from the light source 4, is applied, the original 3 output from the analog-to-digital converter 15 The digital signal corresponding to the image signal has been corrected for the shading distortion of the light source 4. Next, the image reading device shown in FIG. The first photoelectric conversion element 12 and the second photoelectric conversion element 11 are mounted on the same mounting board, and when the original 3 is read, the light emitted from the light source 4 is Reflected light generated on the original 3 by irradiating the original 3 through the original platen 2 is focused on the first photoelectric conversion element 12 via the imaging lens 9 through the optical path of the reflecting mirror 17 → the reflecting mirror 18 → the reflecting fi 19 →. At the same time, the reflected light from the standard white plate 5, which has information on the intensity distribution of the light from the light source 4 described above, passes through the imaging lens 1o through the optical path of 1 reflecting mirror 17→reflecting mirror 18→reflecting mirror 19→. The image is formed on the photoelectric conversion element 11 of No. 2. As shown in this second illustration, the first. second photoelectric conversion element 12,
The configuration in which the optical systems 11 and 11 are mounted on the same substrate is advantageous when, for example, the configuration of the optical system is changed due to zooming or the like. 1 in the image reading device shown in FIG. The image signals outputted from the second photoelectric conversion elements 12 and 11 are respectively output from the first and second photoelectric conversion elements 12 and 11 in the image reading device described above with reference to FIG. This is the same as the image signal output from the second photoelectric conversion element 12.11. That is, the first photoelectric conversion element 12 outputs a high-resolution image signal indicating image information of the original 3 (see (a) in FIG. 3).
The output signal from the sample-and-hold circuit 13 is supplied to the analog-to-digital converter 15. Further, the second photoelectric conversion element 11 generates an image signal (see (d) in FIG. 3) having information on the intensity distribution of the light from the light source 4, and supplies it to the sample and hold circuit 14. The sample and hold circuit 14 uses a light source 4 generated by the second photoelectric conversion element 11 as illustrated in FIG. 3(d).
The image signal having information on the light intensity distribution of
The sample and hold pulse P2 illustrated in e) generates the output signal 5sh2 illustrated in FIG. do. Therefore, in the analog-to-digital converter 15, the output signal 5sh2. That is, since a voltage is applied that is changing according to the information on the intensity distribution of light from the light source 4, the digital signal corresponding to the image signal of the document 3 output from the analog-to-digital converter 15 is output from the light source. The shading distortion of No. 4 is corrected. In the embodiment already described with reference to FIGS. 1 and 2, the first
The reference voltage of the analog-to-digital converter 15 used for analog-to-digital conversion of the image signal output from the photoelectric conversion element 12 is changed according to information on the light intensity distribution of the light source 4. The shading distortion caused in the image signal by the light intensity distribution of the light source 4 is corrected by changing the state voltage. The means for correcting shading distortion performed on the output image signal of the photoelectric converter 12 is not limited to the above-mentioned means; for example, it may be performed using a variable gain amplifier at the analog signal stage. , and can be implemented by any other means. [Effects of the Invention] As is clear from the above detailed description, the image reading device of the present invention converts light reflected from a document irradiated by light emitted from a light source into pixels capable of generating regular image signals. The light reflected from the standard white plate provided at the position where the light from the light source is always applied is applied to the first photoelectric conversion element, which is equipped with several elements, to generate a regular image signal. A second photoelectric conversion element, which may have a smaller number of elements than the first photoelectric conversion element, generates an image signal having shading distortion information, and generates an image signal having shading distortion information as described above. By,
By the simple means of correcting the shading distortion during output decoding from the first photoelectric conversion element described above, it is possible to effectively remove the shading distortion of the light source contained in the image signal. can.

[Brief explanation of drawings]

1 and 2 are block diagrams of different embodiments of the image reading apparatus of the present invention, and FIG. 3 is a waveform diagram for explaining the operation. 1... Main body of reading device, 2... Original table, 3...
Manuscript. 4... Light source, 5... Standard white plate, 6-8, 17-1
9... Reflector, 9, 10... Lens, 11... Second
photoelectric conversion element, 12...first photoelectric conversion element, 13
, 14... Sample hold circuit, 15... Analog-to-digital conversion l, Patent applicant: Victor Japan Co., Ltd.

Claims (1)

[Claims] means for applying reflected light from a document irradiated by light from a light source to a first photoelectric conversion element via a first imaging optical system; and a standard provided at a position where the light from the light source is always applied. a white plate, means for applying reflected light from the standard white plate by the light from the light source to a second photoelectric conversion element via a second imaging optical system, and an output signal of the second photoelectric conversion element. and means for correcting the output of the first photoelectric conversion element based on