JPH04255160A - Image reader - Google Patents

Abstract

PURPOSE:To reduce a transfer time with simple circuit constitution and to easily attain the processing at a host side and a controller side reading an image data. CONSTITUTION:A picture element data is latched in a line memory 1 by one line in the main scanning direction. While a logic circuit latches the image data in a line memory 1, the logic circuit detects a signal (1) representing all black levels and a signal (O) representing all white levels. Thus, the data transfer time is reduced.

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, and more particularly to an image reading device including a data output circuit in an image scanner. For example, it is applied to a device that raster-scans and reads an image and processes it digitally.

0002

[Prior Art] It has been proposed to optically scan the image of a document, convert it photoelectrically using a photoelectric conversion element, represent black and white as 1 and 0, and transfer the image to a host machine or the control unit of the entire device through a predetermined interface. has been done. However, image scanners simply transfer all data in a fixed number of bits, regardless of the content of the converted image data, and the only way to obtain information about the content of the image data is to read the data itself. . Image processing devices such as character recognition devices that read and process image data must read and process one line of data from an image scanner in units determined by the interface (e.g. 8 bits), which increases processing speed. This was a problem from this point of view.

0003

[Purpose] The present invention has been made in view of the above-mentioned circumstances, and is an image reading system that reduces transfer time with a simple circuit configuration and facilitates processing on the host side and controller side for reading image data. This was done for the purpose of providing equipment.

0004

[Structure] In order to achieve the above objects, the present invention provides (1)
In image scanners that scan originals such as documents as binary images and send the image data to a computer or workstation via a certain interface, there is a line memory that holds pixel data for one line in the main scanning direction. , a logic circuit for detecting a signal indicating that the pixel data of the line are all black and a signal indicating that the pixel data of the line are all white, while holding the image data in the line memory, and the signal indicating the white and the signal indicating the black. and the next line data request signal from the host machine in the interface signal to shorten the time for transferring image data to the host machine, or (2) scan an original such as a document and convert it into a binary image. In an image scanner that reads image data and sends it to a computer or workstation via a certain interface, there is a line memory that holds one line of pixel data in the main scanning direction, and a line memory that holds image data in the line memory. It consists of a logic circuit for detecting a signal in which all pixel data is black and a signal in which all pixel data is white. The interface signal includes a signal indicating the image data, and is processed by the host machine when reading the image data;
) In (2) above, the present invention is characterized in that it includes a signal indicating all white and a signal indicating all black corresponding to the line. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a block diagram for explaining an embodiment of an image reading device according to the present invention. In the figure, 1 is a one-line memory, 2 is an AND circuit, 3 is a black latch circuit, and 4 is an O
R circuit, 5 is a white latch circuit, and 6 is a NOT circuit. A line memory 1 that holds pixel data for one line in the main scanning direction, and a signal (1) that indicates that all the pixel data of that line is black while holding image data in the line memory 1.
and a logic circuit for detecting a signal (0) indicating all white. The logic circuit includes a circuit for detecting a signal all_blk (abbreviation for black) indicating all black, and a circuit detecting a signal all_white (abbreviation for black) indicating all white.
The circuit that detects the signal indicating all black consists of an AND circuit 2 and the black latch circuit 3, and the circuit that detects the signal indicating all white consists of an OR circuit.
It is composed of a circuit 4, a white latch circuit 5, and a NOT circuit 6.

In FIG. 2, the line memory having the configuration shown in FIG.
This shows a configuration in which image data for the next line is held in the other line memory.

The operation of the image reading device according to the present invention will be explained below. (1) First, as an initial operation, set the white latch to 0 and the black latch to 1. (2) Write the photoelectrically converted 1-bit image data to the line memory. (3) When the pixel data is 1, the white latch changes to 1,
1 is retained regardless of subsequent data. Therefore, al
The l_wt signal is Low. (4) When the pixel data is 0, the black latch changes to 0,
1 is retained regardless of subsequent data. Therefore, al
The l_blk signal is Low. (5) When one line of pixel data is written to the line memory, the control unit outputs the contents of the line memory by the number of bits determined by the interface, and
The all_wt signal and all_blk signal are also output as interface signals, respectively. (6) In parallel, the image data of the next line memory, the white latch, and the black latch are set in the other line memory of the duplicated line memories. (7) Image data is output by handshaking with the receiving side (the next data is output by the ack signal)
However, when the next line data request signal is activated from the receiving side, the control unit switches the output line memory and starts outputting the next line of image data. Although the figure shows duplicated line memories, the optimal number of line memories is set and managed in a ring buffer based on the relationship between the speed at which the original is scanned and photoelectrically converted and the output speed. You may.

With this configuration, the interface signal includes a signal indicating that the image of one scanned line is all white, a signal indicating that the image is all black, and a next line data request signal from the host machine, and the image is sent to the host machine. The aim is to shorten and speed up data transfer time. That is, by checking the levels of the all_wt signal and all_blk signal, it can be immediately determined that the image data of the line being read is all 0 or 1, and the process can skip reading the image data of the line and proceed with the process. Therefore, the data transfer time can be shortened.

[0009] Furthermore, by providing an interface signal with a signal indicating that all bits of image data to be transferred to the host machine at one time are white and a signal indicating that all bits are black, processing in the host machine when reading the image data is controlled. This is for your convenience. That is, although the image data transfer time is not shortened, all bits in the received data unit are known to be 0 or 1 without checking the contents of the image data on the receiving side, and the processing time on the receiving side is shortened.

0010

[Effects] As is clear from the above description, the present invention has the following effects. (1) Effect on claim 1: When reading image data from a conventional image scanner, even if one line of image data is all 0 or 1, data must be read for the number of bits set for one line. In terms of transfer time, and even after reading, it is impossible to know whether all one line is the same unless all bit data is checked, which hinders the improvement of processing speed in various ways. According to the invention, the all_wt signal, all_
By checking the level of the blk signal, it can be immediately determined that the image data of the line being read is all 0 or 1, and the processing proceeds by skipping the reading of the image data of the line, reducing the data transfer time. can be shortened. This is particularly effective for document manuscripts, which have a high proportion of continuous white lines. (2) Effect on claim 2: The image data transfer time is not shortened, but all bits are 0 in the received data unit without checking the contents of the image data on the receiving side.
or 1, and subsequent processing time on the receiving side is shortened. This method is effective for general document manuscripts because the percentage of consecutive 0's and 1's is high. (3) Effects on Claim 3: In addition to the effects on Claim 2, the data transfer time is also shortened, and on the receiving side, the processing time can be further shortened when one line is all 0 or 1.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram for explaining an embodiment of an image reading device according to the present invention.

FIG. 2 is a diagram showing a configuration in which the line memory of the configuration of FIG. 1 is duplicated.

[Explanation of symbols]

1...1 line memory, 2...AND circuit, 3...black latch circuit, 4...OR circuit, 5...white latch circuit, 6...NOT circuit.

Claims (3)

[Claims] Claim 1: In an image scanner that scans an original such as a document, reads it as a binary image, and transmits the image data to a personal computer, workstation, etc. via a certain interface, pixel data is divided into one line in the main scanning direction. It consists of a line memory for holding image data, and a logic circuit for detecting a signal indicating that all pixel data of the line is black and a signal indicating that all pixel data of the line is white while holding the image data in the line memory, and detecting the signal indicating white. An image reading device characterized in that an interface signal includes a signal indicating black and a next line data request signal from a host machine, thereby shortening the time for transferring image data to the host machine. 2. In an image scanner that scans an original such as a document, reads it as a binary image, and transmits the image data to a personal computer, workstation, etc. via a certain interface, pixel data is divided into one line in the main scanning direction. It consists of a line memory for holding image data, and a logic circuit for detecting a signal indicating that the pixel data of the line is all black and a signal indicating that the pixel data of the line is all white while holding the image data in the line memory. An image reading device characterized in that an interface signal includes a signal indicating that all bits of image data to be transferred are white and a signal indicating that all bits are black, and the interface signals are processed by a host machine when reading the image data. 3. The image reading device according to claim 2, further comprising a signal indicating all white and a signal indicating all black corresponding to the line.