JPH05191644A - Picture reader - Google Patents

Abstract

PURPOSE:To attain shading correction in the picture reader at an analog section. CONSTITUTION:The picture reader in which a light from a light source 3 radiates to an original 1, a light from the original 1 is received by a photoelectric conversion element 4 to read the original 1 is provided with a reference voltage generating section 5 generating a reference voltage to obtain data correcting distortion of an output due to dispersion in the illuminance of the light source 3 and the sensitivity of the photoelectric conversion element 4, a divider circuit 6 dividing the reference voltage by an output of the photoelectric conversion element 4, an A/D converter section 7 digital-converting the divided signal to obtain correction data, a memory section 8 storing the correction data subjected to digital conversion by the A/D converter section 7 through the use of a reference white level board 2, a D/A converter section 9 analog- converting the correction data stored in the memory display section 8 in the case of reading of the original 1 to obtain a correction signal and a multiplier circuit 10 multiplying the analog-converted correction signal by an output of the photoelectric conversion element 4, and various analog signal processing is attained after shading correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device for irradiating a document or the like with light from a light source to read the same, and more particularly to an image reading device having a shading correction function for correcting image distortion due to an output signal. It relates to the device.

[0002]

2. Description of the Related Art Conventionally, in this type of image reading apparatus, an output is produced due to variations in the illuminance of a light source that outputs the irradiation light of an original or the like and the sensitivity of a photoelectric conversion element (CCD sensor) that receives light from the original or the like. Distortion occurs.

Therefore, the image reading apparatus is designed to perform shading correction. For this shading correction, a reference white plate (for white balance) or the like is used in place of the original, and photoelectric conversion is performed. The output of the element is A
A / D converter performs A / D conversion, and this digitally converted correction data is stored in a memory unit. When reading a document or the like, the correction data in the memory unit is analog-converted and applied to the reference output of the A / D converter. The method of changing the reference voltage is adopted.

[0004]

By the way, in the image reading apparatus, since the reference voltage of the A / D converter is changed, the shading correction is digitally performed.

However, in the image reading apparatus, various kinds of analog signal processing may be preferable. For example, in the case of γ correction, digital processing is performed after the shading correction. However, this γ correction causes a defect in a lower bit. Because there is.

The present invention has been made in view of the above problems, and an object of the present invention is to perform shading correction in an analog system.
An object of the present invention is to provide an image reading device capable of analog processing such as correction.

[0007]

In order to achieve the above object, the present invention irradiates an original with light from a light source, converts the light from the original into an electric signal by a photoelectric conversion element, and outputs the original. In an image reading apparatus for reading, a reference voltage is generated in order to obtain correction data for correcting a reference white plate used before reading the original document and output distortion due to variations in illuminance of the light source and sensitivity of the photoelectric conversion element. A reference voltage generator, and a divider circuit that divides the reference voltage by the output of the photoelectric conversion element by the reference voltage generated by the reference voltage generator,
An A / D conversion unit for digitally converting the output signal of the division circuit to obtain the correction data, a memory unit for storing the digitally converted correction data, and a memory unit for storing the original data in reading the original. A D / A conversion unit for converting the correction data into an analog signal to obtain a correction signal and a multiplication circuit for multiplying the output of the photoelectric conversion element by the analog-converted correction signal are provided. The gist is that the shading correction is performed in an analog manner.

[0008]

With the above configuration, the shading correction data is stored in the memory section, and the correction data in the memory section is read out and converted into analog when reading the original. This analog-converted correction signal is multiplied by the output of the photoelectric conversion element which is currently reading the original.

As a result, since the shading correction is performed on the output signal of the photoelectric conversion element, the distortion of the output of the image reading apparatus can be eliminated.

Further, since the shading correction is performed in an analog system, various analog signal processing such as analog γ correction can be performed after the shading correction.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the image reading apparatus of the present invention, it is preferable that the output (analog) signal of a photoelectric conversion element for reading an original or the like is digitally converted, that is, it is preferable that shading correction is applied in an analog state and processed in analog. For example, γ correction and the like can be performed after the shading correction.

For this reason, this image reading apparatus has, for example, the configuration shown in FIG. 1, and includes a light source 3 for irradiating the original 1 or a reference white plate (for white balance) 2 with light, and the original 1.
Alternatively, a photoelectric conversion element (CCD sensor; line sensor) 4 that receives light from the reference white plate 2 and converts it into an electric signal
In order to obtain data for correcting output distortion due to variations in the illuminance of the light source 3 and the sensitivity of the photoelectric conversion element 4, a reference voltage generator 5 that generates a reference voltage, and the generated reference voltage are converted into the photoelectric conversion signals. Division circuit 6 that divides by the output of the element
And an A / D conversion section 7 for digitally converting the output signal of the division circuit 6 to obtain correction data, and the reference white plate 2 used for storing the correction data digitally converted by the A / D conversion section 7. Memory section 8, a D / A conversion section 9 for converting the correction data stored in the memory section 8 into an analog signal to obtain a correction signal when the original 1 is read, and the analog correction signal for converting the correction signal into the photoelectric signal. A multiplication circuit 10 for multiplying the output of the conversion element 4 is provided.

The image reading apparatus is provided with various circuits (not shown) for reading and outputting the original 1.

In the image reading apparatus having the above-mentioned structure, the reference white plate 2 is set and the reference white plate 2 is read before reading the predetermined original 1.

In this case, the light from the reference white plate 2 is converted into an electric signal by the photoelectric conversion element 4, and the reference white plate 2 is converted into an electric signal.
Signal is input to the division circuit 6. As a result, the reference voltage from the reference voltage generator 5 is divided by the input signal, that is, an analog signal having a magnification (fraction) of the output of the photoelectric conversion element 4 with respect to the reference voltage is obtained.

The signal obtained by the division circuit 6 is digitally converted by the A / D conversion section 7, that is, white balance correction data for keeping the output of the photoelectric conversion element 4 constant is obtained.

When the photoelectric conversion element 4 is a line sensor, all the reference white plates 2 are read by the line sensor, and correction data for making the output of the line sensor constant is provided for all the reference white plates 2. And the correction data are recorded in the memory unit 8.

After the reading of the reference white plate 2 is completed, a predetermined original 1 is set in place of the reference white plate 2 and
The original 1 is read. When reading the original 1, the light from the original 1 is transferred to the photoelectric conversion element 4
The light is received by, and the signal (analog signal) of the original 1 is output from the photoelectric conversion element 4.

At this time, the correction data of the memory section 8 is read at the read timing of the line sensor of the photoelectric conversion element 4, and this correction data is read by the D / A conversion section 9.
Is converted to analog.

Then, in the multiplication circuit 10, the analog-converted correction signal is multiplied by the output signal of the photoelectric conversion element 4, and shading correction is performed on the output signal of the photoelectric conversion element 4.

In this case, since both the output signal of the photoelectric conversion element 4 and the signal multiplied by the same are analog signals, the shading correction is performed in the analog part.

As a result, the distortion of the output due to the variations in the illuminance of the light source 1 and the sensitivity of the photoelectric conversion element 4 can be eliminated, and since the shading correction is performed in the analog system, the analog γ after the shading correction is performed.
Various analog signal processing such as correction can be performed.

Here, γ correction will be described as an example. As in the conventional example, when digitally performed, the lower bits are omitted, and in order to suppress the omission, the A / D converter has a high resolution. You need to use one.

However, in the image reading apparatus of the present invention, when the original 1 is read, since shading correction is performed in the analog portion, the signal subjected to the shading correction is subjected to signal processing such as analog γ correction. However, even if digital conversion is performed thereafter, there is no omission in the read data of the original 1 that has been digitally converted as in the conventional example, and various types of preferable analog signal processing can be performed.

In the image reading apparatus, the output signal of the multiplication circuit 10 is subjected to predetermined processing and converted into a digital signal (image data), whereby the reading of the original 1 is completed.

[0026]

As described above, according to the image reading apparatus of the present invention, the reference voltage is multiplied by the output of the photoelectric conversion element at the time of taking in shading correction, and the multiplied value is stored in the memory unit as correction data. When reading an original, the output of the photoelectric conversion element is multiplied by the correction data, and shading correction is performed in the analog part.Therefore, variations in the illuminance of the light source that outputs the irradiation light of the original and the sensitivity of the photoelectric conversion element It is possible to eliminate the distortion of the output due to the above, and it is possible to perform various kinds of analog signal processing such as analog γ correction after the shading correction, that is, it is possible to perform extremely preferable signal processing.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of an image reading apparatus showing an embodiment of the present invention.

[Explanation of symbols]

 1 Original 2 Reference white plate (for white balance) 3 Light source 4 Photoelectric conversion element (CCD sensor) 5 Reference voltage generation section 6 Division circuit 7 A / D conversion section 8 Memory section 9 D / A conversion section 10 Multiplier circuit

Claims (1)

[Claims] 1. A reference used in an image reading device for irradiating light from a light source onto a document, converting the light from the document into an electric signal by a photoelectric conversion element, and reading the document before reading the document. A white plate, a reference voltage generating section for generating a reference voltage, and a reference generated by the reference voltage generating section in order to obtain correction data for correcting output distortion due to variations in the illuminance of the light source and the sensitivity of the photoelectric conversion element. A division circuit that divides a reference voltage by the output of the photoelectric conversion element by a voltage, an A / D conversion unit that digitally converts the output signal of the division circuit to obtain the correction data, and stores the digitally converted correction data. A memory section, a D / A conversion section for converting the correction data stored in the memory section into an analog signal to obtain a correction signal when reading the document, and an output of the photoelectric conversion element. Serial and a multiplication circuit for multiplying the correction signal analog conversion, the image reading apparatus being characterized in that to perform the analog to shading correction on the output of the photoelectric conversion element.