JPH04287561A - Picture input device - Google Patents

Abstract

PURPOSE:To attain high picture quality data with a matched focus even when an original is not in close contact with a base by detecting a distance between the original and an original platen to apply mobile control to a lens and a photoelectric conversion element in response to the distance. CONSTITUTION:A distance sensor 8 having an ultrasonic wave sensor moving in the scanning direction integrally with a lighting source 6 is provided in the vicinity of an original platen 4 to detect the distance between the original 5 and the platen 4 located by several lines of reading. Then the resolution accuracy of the sensor is selected to be one unit of sensor movement. Moreover, the lens 2 and a photoelectric conversion element 1 are fitted to a movable base 9 moved in the scanning direction A and the base 9 is controlled by a pulse motor. Thus, even when the original 5 is not in close contact with the base 4, a picture data with high quality with matched focus is obtained.

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 particularly suitable for reading an uneven original such as a book into a device having an image reading function such as a scanner or a character recognition device.

0002

[Prior Art] In a conventional image input device that supports a document,
Since the document reading position where the image is formed on the photoelectric conversion element is fixed on the surface of the document table, when the document has a folded part, such as a book, there is a gap between the document table and the document, and the document cannot be focused at the folded part. The image was blurred.

[0003] A conventional document-standing type image input device will be described below. FIG. 3 is a configuration diagram of a conventional image input device having a fixed image sensor. As shown in FIG. 3, the positions of the photoelectric conversion element (one-dimensional image sensor) 1 and the lens 2 are fixed, and the ratio of the moving speeds of the mirror 3A and the mirrors 3B and 3C is set to 2:1. The document reading position is fixed to the surface of the document table 4 by keeping the optical path length between the surface of the document table 4 and the lens 2 constant. Therefore, even if the document 5 is located at a position away from the surface of the document table 4, there is no means for adjusting the focus, and a clear image cannot be obtained. Note that 6 is an illumination light source that is movable along the scanning direction A.

0004

[Problems to be Solved by the Invention] As explained in the prior art, conventionally, when reading the original 5, the original reading position where the image is formed on the photoelectric conversion element 1 is fixed on the surface of the original platen 4. In the case of a document 5 with a folded part, such as a book, there were parts that were out of focus, resulting in a blurred image.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an image input device that can obtain clear images even when reading manuscripts such as books.

[0006]

[Means for solving the problem] Conventional original-standing type image input devices fix the original reading position on the surface of the original platen, so if there is a gap between the original platen and the original, the image will be out of focus and blurry. However, in order to solve this problem, the image input device of the present invention is equipped with a detection means for detecting the distance between the document table and the document, and uses the distance information from the detection means to detect the distance between the document table and the document. The photoelectric conversion element and the lens are moved to constantly image document surface information on the photoelectric conversion element.

[0007]

[Operation] By measuring the distance between the document table and the document as described above and moving the position of the photoelectric conversion element and lens so that the document surface information is always imaged on the photoelectric conversion element,
It is possible to obtain a focused, high-quality image.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. FIG. 1 is a block diagram of an image input device according to an embodiment of the present invention. Components with the same functions as those of the conventional device are given the same reference numerals and their explanation will be omitted.

As shown in FIG. 1, a distance sensor 8 consisting of an ultrasonic sensor that moves integrally with the illumination light source 6 in the scanning direction is provided near the document table 3. The distance between the document table 3 and the document 5 in front of the line is detected. A high-performance ultrasonic sensor has a resolution of ±0.2 when the measurement distance is 0.5 to 20 cm.
Since an accuracy of mm 2 can be obtained, this resolution accuracy is taken as one unit of sensor movement.

Further, the photoelectric conversion element 1 and the lens 2 are attached to a moving table 9 that is movable in the scanning direction A, and the moving distance of the moving table 9, that is, the photoelectric conversion element 1 and the lens 2 is controlled by a pulse motor 10, which will be described later. controlled. Since the photoelectric conversion element 1 uses a one-dimensional image sensor, the distance between the document table 3 and the document 5 for one line scanning needs to be uniform.

FIG. 2 is a block diagram of the image input device.
is the first amplifier, 12 is the A/D converter, 13 is memory, 1
4 is an arithmetic unit, 15 is a motor driver for driving the pulse motor 10, 16 is a second amplifier, and 17 is a binarization circuit.

The operation of the image input circuit having the above configuration will be explained below. First, the distance between the document table 3 and the document 5 is detected by the distance sensor 8, and this distance information is converted into an electrical signal. The obtained electrical signal is amplified by the first amplifier 11, and the amplified electrical signal is converted into a digital signal by the A/D converter 12. The distance information thus converted into a digital signal is stored in the memory 13. Before the photoelectric conversion element 1 reads one line of image information, the arithmetic unit 14 reads the memory 13
The distance information of the line to be read is taken out, the amount of movement of the photoelectric conversion element 1 is determined, and a control signal is sent to the motor driver 15. The motor driver 15 drives the pulse motor 10 based on the received control signal, and moves the photoelectric conversion element 1 and the lens 2 integrally via the moving table 9. That is, the photoelectric conversion element 1 and the lens 2 are moved by the amount of change in the distance between the original platen 3 and the original 5 to accurately form an image of document surface information on the photoelectric conversion element 1. The optical signal obtained as described above is amplified by the second amplifier 16, and the amplified electric signal is
The data is binarized by the value conversion circuit 17 to obtain clear image data.

As described above, the distance measurement position between the document table 3 and the document 5 is set several lines before the reading line, distance information for several lines is stored in the memory 13, and the distance information for that line is stored before reading the image. By retrieving the distance information from the memory 13, the position determination of the photoelectric conversion element 1 can be dynamically controlled.

Although an ultrasonic sensor is used as the distance sensor 8 in this embodiment, since ultrasonic waves are reflected by glass, when using an ultrasonic sensor, a slit-like cut must be made in the glass of the document table 3. There must be. Therefore, by using a distance sensor that uses light such as a laser that is not reflected by glass, it is no longer necessary to cut the glass of document table 3, and this problem is solved.

[0015]

As described above, according to the present invention, the distance between the document and the document table is detected and the movement of the lens and the photoelectric conversion element is controlled according to this distance. High-quality, in-focus image data can be obtained even when the document is not in close contact with the document table. As a result, it is possible to realize a high-performance copying machine and improve the recognition rate of a character recognition device.

[Brief explanation of the drawing]

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

FIG. 2 is a block diagram of an image input device of the present invention.

FIG. 3 is a configuration diagram of a conventional image input device.

[Explanation of symbols]

1 Photoelectric conversion element 2
Lens 3A, 3B, 3
C mirror

Claims (1)

[Claims] 1. A document table on which a document is placed, a detection means for detecting a distance between the document table and the document, and a focal position of an optical system can be freely controlled based on the distance information obtained from the detection means. and a photoelectric conversion element that converts an optical signal obtained by optically scanning a document into an electrical signal, and based on the distance information obtained by detecting the distance between the document table and the document by the control means. An image input device configured to move a lens of an optical system and a photoelectric conversion element so that document surface information is always imaged on the photoelectric conversion element.