JPH07302323A - Image input device - Google Patents

Abstract

PURPOSE:To input an accurate image with a high SN ratio by storing an A/D converted digital electric signal and computing a mean value of plural times of reading. CONSTITUTION:A storage part 42 alternately executes storage and reading by the capacity of one line. At the time of storing, a digital signal inputted from an A/D conversion part 41 is stored, and at the time of reading, the stored image is outputted to a computing part 43. At the reading time of the storing part 42, the computing part 43 computes a mean value between the digital signal outputted from the A/D conversion part 41 and a signal read out from the storage part 42 in each picture element and an output part 5 outputs a picture signal outputted from the computing part 43 to the outside of the device or a storage device. A driving part 6 moves an illuminating part 8, an image forming part 2 and a photoelectric conversion part 3 in a sub-scanning direction vertical to the array direction of a photoelectric conversion element 31 relatively to an original and a control part 11 controls the state, sequence, etc., of the whole device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device for converting a document into an image signal, such as an image input scanner used in a computer image processing system for processing an image.

[0002]

2. Description of the Related Art In a conventional image input device, as shown in FIG. 2, a document 9 is irradiated with light from a lighting unit 8 and the light from the document 9 is imaged by a focusing unit 2 and a CCD or the like is used. A plurality of photoelectric conversion elements 31 arranged in a line in the main scanning direction in the photoelectric conversion unit 3.
Is converted into an electric signal by the driving unit 6, and the driving unit 6 moves the illuminating unit 8, the imaging unit 2 and the photoelectric conversion unit 3 in a direction perpendicular to the arrangement direction of the photoelectric conversion elements 31, and the output unit 5 drives the driving unit 6. The image signal is output to the outside of the device or the recording device in synchronization with the position.

Here, in the conventional image input apparatus, the light input to the photoelectric conversion unit 3 is a photon, and the reflectance of the document is estimated from the number of photons incident for a certain period of time. Therefore, the output of the photoelectric conversion unit 3 includes a statistical error called shot noise. In addition to this,
The analog electric signal output from the AD converter includes various electric noises.

[0004]

The conventional method has a problem that the S / N ratio of the image input from the image input device is deteriorated due to the shot noise and the electrical noise described above. Therefore, an object of the present invention is to increase the S / N ratio by storing an AD-converted digital electric signal and calculating an average value of a plurality of readings in order to solve the conventional problem. To obtain an image input device for inputting an accurate image.

[0005]

In order to solve the conventional problems, according to the present invention, a supporting means for supporting an original, an illuminating means for illuminating the original, and a light from the original are imaged on a photoelectric conversion portion. Image forming means, a photoelectric converting means for converting light imaged by a plurality of photoelectric converting elements arranged in the main scanning direction on the image forming surface of the image forming means into an analog electric signal, and the photoelectric converting means AD conversion means for inputting an analog electric signal to be output and outputting a digital signal; storage means for storing the digital signal output by the AD conversion means;
Computation means for computing the digital signal output from the D conversion means and the signal stored in the storage means, output means for outputting the image signal output by the computation means to the outside of the device or a storage device, the illumination means and the connection. Image input device by drive means for moving the image means and the photoelectric conversion means relative to the original in a direction perpendicular to the arrangement direction of the photoelectric conversion elements, and a control means for managing the state and sequence of the entire apparatus. Configured.

[0006]

In the image input apparatus constructed as described above, the light from the illuminating means is applied to the document, and the light from the document is imaged on the photoelectric conversion means by the image forming means, and the light is converted by the photoelectric conversion means. The imaged light is converted into an analog electric signal by a photoelectric conversion element arranged in the main scanning direction corresponding to each pixel,
The analog electric signal from the photoelectric conversion means is converted into a digital signal by the AD conversion means. The storage means stores and reads. The digital signal from the AD conversion means is stored at the time of storage, and the stored image is output to the calculation means at the time of reading. The arithmetic means calculates the average value of the digital signal output by the AD conversion and the output of the storage means when the storage means is read, and the output means outputs the image signal output by the arithmetic means to the outside of the device or the storage device. To do. The driving means relatively moves the illuminating means, the image forming means and the photoelectric conversion means with respect to the original in the sub-scanning direction perpendicular to the arrangement direction of the photoelectric conversion elements, and the control means controls the state of the entire apparatus and Manage sequences etc.

As described above, by averaging the AD-converted digital image signals of a plurality of lines, an image input device for inputting an image having a high SN ratio can be realized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the supporting section 91 supports the original 9 by a known method, and the illumination section 8 by the known method.
Then, the image forming section 2 forms an image of the reflected light from the original 9 on the photoelectric conversion section 3, and the light formed by the image forming section 2 in the photoelectric conversion section 3 is converted into each image as shown in FIG. The plurality of photoelectric conversion elements 31 arranged in the main scanning direction corresponding to the pixels convert the electric signals into analog electric signals, and the AD conversion unit 41 converts the analog electric signals output from the photoelectric conversion unit 3 into digital signals.
Convert. The storage unit 42 has a capacity of one line and alternately stores and reads. At the time of storage, the AD conversion unit 41
The stored digital image signal is stored, and the stored image is output to the arithmetic unit 43 at the time of reading. The arithmetic unit 43 calculates the average value of the digital signal output from the AD converter 41 and the read signal of the storage unit 42 for each pixel when reading the storage unit 42, and the output unit 5 calculates the average value. The image signal output by is output to the outside of the device or a storage device. Here, the driving unit 6 includes the illumination unit 8 and the image forming unit 2.
Also, the photoelectric conversion unit 3 is moved relative to the original in the sub-scanning direction perpendicular to the arrangement direction of the photoelectric conversion elements 31, and the control unit manages the state and sequence of the entire apparatus.

The photoelectric conversion section 3, the AD conversion section 41, the storage section 42, and the calculation section 4 which are the main constituent elements of the present invention are described below.
3 will be described in detail. However, the light input to the photoelectric conversion unit 3 is a photon, and the reflectance of the document is estimated from the number of photons incident in a certain time. Therefore, the output of the photoelectric conversion unit 3 includes a statistical error called shot noise. In addition to this, the analog electric signal output from the AD converter includes various electric noises.

In general, in order to increase the SN ratio, the accumulation time of photoelectric conversion may be lengthened or the area of the photoelectric conversion element may be increased. However, since the photoelectric conversion unit 3 detects the amount of light when a photon collides with an electron in the semiconductor and the level of the electron changes, the saturation level becomes a problem, and a sufficient storage time cannot be secured. . Further, when the resolution is high, the area of the photoelectric conversion element is usually about several squares. Therefore, in normal use, the SN ratio is limited to the ratio of the noise level to the saturation level of the photoelectric conversion element. Therefore, in the present invention, when the image data is read, by averaging the converted values of the photoelectric conversion elements twice, it is possible to input an image with a high SN ratio that is not subject to the saturation level limitation even when the resolution is high. it can.
If the converted values of two times are simply added, the signal level will be doubled because it comes in the same phase, and the noise level will be randomly entered, so it will be double the square root of 2, so the SN ratio will be the square root of 2. Become.

Conventionally, in the shading correction in the AD converter for correcting the variations in the sensitivity and the dark output of each photoelectric conversion element, the SN is calculated by calculating the average value of a plurality of lines with respect to the white reference and the black reference. Although a method for improving the ratio is known, in the present invention, the average of two adjacent lines can be calculated for image input in order to further improve the SN ratio. For this reason, the resolution in the sub-scanning direction up to the AD conversion unit is twice the resolution of the image after averaging in the calculation unit 43.

An example of averaging read data of two lines has been described above. However, when the storage unit 42 has a capacity of a plurality of lines, the average value of a plurality of lines can be calculated. When averaging is performed on n lines, the SN ratio is improved to the square root of n. Further, as shown in FIG. 4, by increasing the storage capacity of the storage unit 42 to an extent necessary for the average calculation, the output of the AD conversion unit 41 is temporarily stored in the storage unit without being directly connected to the calculation unit 43. The read data of a plurality of lines may be calculated by the calculation unit 43.

Further, the storage unit 42 may have any capacity as long as it can carry out an averaging operation, for example, if it has a capacity for a plurality of screens. Further, an example of the image input device in which the illumination unit 8, the image forming unit 2, and the photoelectric conversion unit 3 are integrated and moves in the sub-scanning direction with respect to the document has been described above. Any image input device such as the image input device described above that inputs an image by the photoelectric conversion unit may be used.

Furthermore, in this embodiment, an example of a mono-color one-dimensional image input device is shown, but the same applies to a color image input device and a two-dimensional image input device.

[0015]

As described above, in the image input device according to the present invention, the supporting means, the illuminating means, the image forming means, the photoelectric converting means, the AD converting means, the storing means, the calculating means, the outputting means, the driving means, The image input device is constituted by the control means.

With this configuration, the image input device according to the present invention has an effect that an image having a high SN ratio can be input, as compared with the conventional image input device.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an image input device according to the present invention.

FIG. 2 is a configuration diagram showing a configuration of a conventional image input device.

FIG. 3 is a configuration diagram showing a configuration of a photoelectric conversion unit of the present invention.

FIG. 4 is a diagram showing a configuration of an image input device according to another embodiment of the present invention.

[Explanation of symbols]

 2 Image forming section 3 Photoelectric conversion section 5 Output section 6 Driving section 8 Illumination section 9 Original document 11 Control section 31 Photoelectric conversion element 41 AD conversion section 42 Storage section 43 Computing section 91 Support section

Claims (1)

[Claims] 1. An illumination unit for irradiating an original, an image forming unit for forming an image of reflected light from the original, and a plurality of photoelectric conversion elements arranged with the light formed by the image forming unit in a main scanning direction. In an image input device for inputting an image having photoelectric conversion means for performing photoelectric conversion by AD, an analog electric signal output by the photoelectric conversion means is input and converted into a digital signal.
Conversion means, storage means for storing the digital signal output from the AD conversion means, and calculation means for calculating an average value for each pixel in the main scanning direction from the output of the AD conversion means and the output of the storage means. A sequence of the entire apparatus and an output means for outputting a signal output from the arithmetic means to the outside, a drive means for moving the illuminating means and the light collecting means in a direction perpendicular to the main scanning direction with respect to the original. An image input device comprising: a control unit for controlling.