JPH0787515B2 - Image reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an image reading apparatus which is applied to a facsimile apparatus or the like and which scans a document by conveying an original by a drive system having a step motor as a drive source. Is.

(B) Conventional technology Recently, an electrophotographic method has been applied to the printing section for the purpose of high speed and high definition recording.
A plain paper recording type facsimile machine incorporating PPC (plain paper copier) technology has been put into practical use. Such a facsimile machine is disclosed, for example, in the article "Ultra-high-speed facsimile machine" on pages 197 to 206 of Research and Practical Report Vol. 33, No. 11 (1984) of the Telecommunications Research Institute.

By the way, as a document reading device in such a facsimile apparatus, a document stationary type reading device is used in which a document to be transmitted is placed on a document placing table and a reading system is moved to perform sub scanning. Also in this type of facsimile apparatus, if a moving document reading device for reading a document while feeding it with a driving system (hereinafter referred to as a feeder) using a step motor as a driving source is added, it is longer than a predetermined size, that is, a so-called "long size". It becomes possible to send a "material" manuscript.

(C) Problems to be Solved by the Invention In the above-described conventional reading device, as the reading control, the driving pulse of the step motor and the reading start signal for one line are synchronized, and the document is intermittently read according to the encoding speed. Reading while sending.

However, when the step motor is driven intermittently, there is a problem that the read image is expanded or contracted in the sub-scanning direction due to the response delay between the motor pulse and the drive system.

Therefore, in order to eliminate image distortion in the sub-scanning direction, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Application Laid-Open No. 19466, the step motor stop control is improved by continuously applying a constant number of forward rotation motor pulses and then immediately applying a reverse rotation pulse. An intermittent sub-scanning control method has been proposed, which is started at a certain time after the start of application of the rolling pulse.

However, this method is not preferable because the motor load suddenly increases when the reverse pulse is applied, and the higher the speed, the more the motor is forced to overload. The noise at this time is also a problem.

The present invention provides an image reading apparatus that eliminates distortion in the sub-scanning direction of an image read from a feeder during transmission, reduces noise caused by driving a step motor, and does not force an overload operation on the step motor. To do.

(D) Means for Solving the Problems The present invention is a reading means for reading a document sent by a drive system having a step motor as a drive source by photoelectric conversion and outputting a binary image signal, and a reading means for reading the read image. Storage means for storing the image signal, encoding means for processing the image signal into a redundancy suppression encoded signal, second storage means for accumulating the image signal to be supplied to the encoding means, the first storage means The storage amount detection means for detecting that the storage state of the storage means 11 has reached a predetermined amount or more, and the read image signal in the first storage means or the image signal stored in the first storage means. This is a facsimile apparatus provided with transfer means for transferring to a second storage means.

(E) Operation When the original is longer than a predetermined size and is a so-called "long object", the step motor is stopped immediately before the page memory acting as the first storage means is filled, and then the drive system is operated. After the experimentally determined number of lines is read in consideration of the response delay of, the reading is also stopped, and the transfer from the first storage means to the second storage means for encoding is performed by the read stop line. When the document reaches N lines before, the document feeding and the reading are started again, and the reading and stopping of the document are repeated until the reading of the document is completed, so that the long document is not distorted and the motor noise is transmitted with little noise. be able to.

(F) Embodiment FIG. 1 is a block diagram of a facsimile apparatus to which an embodiment of the present invention is applied. The facsimile apparatus includes a system control unit (1). The system control unit (1) is composed of a microcomputer, and its function includes a main controller and an internal memory. The main controller is shown in FIG. The internal memory includes an area for storing data necessary for transmission processing such as document reading and a flag area for storing various operation states.

Reading device (2) connected to the system control unit (1)
Is a document feed mechanism driven by a step motor, a light source,
It is composed of an optical lens system, a photoelectric conversion circuit, and an image signal binarization circuit. The system control unit (1) outputs a forward rotation pulse of the step motor and a reading start signal of an image signal to the reading device (2) in response to the timer interrupt of the microcomputer. Then, the reading device (2) outputs a binarized image signal for one line as a time-series signal in bit units after a certain time delay from the reading start pulse.

A serial / parallel conversion circuit (hereinafter referred to as S / S) inserted between the reading device (2) and a page memory (4) described later.
It is called P circuit. ) (3) converts the image signal output as a time-series signal in bit units from the reading device (2) into an image signal of time-series data in byte units, and outputs the image signal to the system data bus.

A page memory (4) acting as a first storage means is connected to the system control section (1), and the page memory (4) stores the image signal output from the reading device (2).
The S / P circuit (3) converts it to an image signal of time series data in byte units and stores it. And this page memory (4)
Includes a storage area of a predetermined number of pages (for example, one page of a document).

A buffer memory circuit (5) acting as a second storage means for accumulating an image signal to be supplied to the encoding means is connected to the system control section (1) and includes a page memory (4) and an encoding circuit (6). This buffer memory circuit (5) is inserted between the first buffer memory (5a) and the second buffer memory circuit (5a).
The image data to be encoded is stored for one line by including the buffer memory (5b). Thus, the reason why the buffer memory is divided into two is that if there is only one buffer memory, the code processing operation must be stopped during the memory transfer from the page memory (4), and the code speed becomes slow. This is because it cannot support high-speed transmission. That is, the buffer memory is divided into the code memory and the transfer memory, and the roles are alternately shared so as to prevent the code speed from decreasing.

The encoding circuit (6) converts the image signal stored in the buffer memory (5a) or (5b) line by line into a redundancy suppression encoded signal such as a modifide Huffman code. When the encoding circuit (6) completes the encoding for one line, for example, the encoding of the image information written in the buffer memory (5a), the next one line, that is, the buffer memory (5b). From the page memory (4) to the buffer memory (5b) for encoding, the system control unit (1) is set to a writable state in the buffer memory (5a) that has started encoding and has completed encoding. The image signal transfer request signal is output. When the transfer of one line corresponding to this transfer request is completed, the system controller (1) clears the transfer request signal.

The encoded image signal encoded by the encoding circuit (6) is transmitted via a modem (not shown).

The DMA (Direct Memory Access) controller (7) responds to an instruction from the system control unit (1).
The image signal output from the S / P circuit (3) to the system data bus is DMA-transferred to the page memory (4), or
The image signal is DMA-transferred from the page memory (4) to the buffer memory (5a) or (5b).

The system controller (1) reads the image signal and controls the DMA transfer to the page memory (4) in parallel, and if there is a transfer request from the encoding circuit (6), the page memory of the image signal for one line Immediately after the transfer to the DMA controller (7), the page memory (4) is instructed to transfer the image signal to the buffer memory (5a) or (5b), and the page memory (4) to the buffer memory (5a). Or (5b)
DMA transfer to.

FIG. 2 is a timing chart showing transfer timings of image signals by the system controller (1) and the DMA controller (7). In FIG. 2, (A) shows a motor pulse applied to the step motor, and the drive system starts the operation in response to this motor pulse to convey the original by one line. Further, the original is read by the CCD or the like of the reading device (2) in synchronization with this motor pulse. (B)
Is a read transfer busy signal indicating that the image signal is being transferred to the page memory (4), and is output in synchronization with the trailing edge of the motor pulse (A). (C) is an image signal transfer request signal from the page memory to the buffer memory (5a) or (5b).
It falls when the image signal transfer to the buffer memory (5a) or (5b) is completed. (D) is a memory-to-memory transfer busy signal indicating that data is being transferred to the buffer memory (5a) or (5b), and is output during the transfer of the image signal to the page memory (4).

FIG. 3 is a schematic side view showing the relationship between the reading position of the reading device and the position of the document detection sensor. The document detection sensor (21)
The document reading operation is completed by performing the document feeding and reading operation for a predetermined line (L line) after is turned off. In FIG. 3, (22) is a document feed roller driven by a step motor, (23) is a document, and (2)
1) is a document position detection sensor, and (24) is a document reading position. The distance between the document position sensor (21) and the reading position (24) corresponds to (L) lines of the document feed pitch.

FIG. 4 is a response characteristic diagram showing the relationship between the motor pulse and the document feeding displacement when the step motor is started.

In FIG. 4, the broken line shows the reading position with respect to the motor pulse, and in the present embodiment, when transferring to the buffer memory for encoding, by thinning out the line marked with X in the drawing, the reading pitch is made constant. The image distortion is eliminated. That is, in consideration of the response characteristics of the driving source such as the step motor, the thinned lines are determined so as to have a constant pitch.

Next, the specific operation of this embodiment will be described with reference to FIGS.

The operation of the system controller will be mainly described with reference to the flowchart of FIG.

(A) When the transmission document has a predetermined size and less than one page When the transmission operation is started, a motor pulse is output in step S1, the document is conveyed by one line, and the process proceeds to step S2. In step S2, one line is read. Image signal DM
DMA transfer to the page memory (4) is performed by the A controller (7), and the process proceeds to step S3. In step S3, it is determined whether the document detection sensor has detected the end of the document. Immediately after the start of the transmission operation, it is determined that the document end has not been detected, and the process proceeds to step S4. In step S4,
It is determined whether or not the page memory (4) has stored a predetermined amount or more, that is, whether or not the page memory (4) is almost full. Immediately after the start of transmission, it is determined that the predetermined amount has not been reached, and the process proceeds to step S5.

As described above, the page memory (4) is selected to have a capacity to store one sheet with a margin if the original is within a predetermined size. If the original is long, the page memory may overflow. Therefore, when the image signal is transferred to the page memory up to a predetermined address M before the overflow, a detection signal is output. Of. Further, as will be described later, the remaining storage capacity of the page memory (4) is divided by the time reading cycle after the motor pulse is stopped until the drive system is completely stopped in consideration of the response delay of the drive system to the motor pulse. Since it is configured to read and transfer a larger number L of lines, the address M is determined so that this L line can be stored from the address M to the last address of the page memory.

In step S5, it is determined whether or not there is a transfer request to the buffer memory (5a) or (5b). That is, since the transfer request signal is output when the encoding process of the first line and the encoding circuit (6) is completed, it is determined that the transfer request is present in the case of the first line and step S6 is performed.
Proceed to. When the encoding circuit (6) is in the process of encoding, no transfer request is output, so it is determined that there is no transfer request, and the process proceeds to step S7. In step S7, it is determined whether or not the reading is stopped. Then, in step S7,
If the reading is not stopped, the process proceeds to step S8 and it is determined whether or not the step motor is stopped. If the size of the document is the predetermined size, the motor is not stopped until the end of the document is detected and the reading of the predetermined number of lines is completed as described later, so it is determined in step S8 that the step motor is not stopped. Is done and returns to step S1,
The above-described operation is repeated, and image signals obtained by reading an original document that moves at a constant pitch at a predetermined pitch even during the encoding process are sequentially transferred and stored in the page memory (4). If it is determined in step S8 that the motor is stopped, step S2
Then, one line worth of DMA is transferred to the page memory.

On the other hand, if it is determined in step S7 that the reading is stopped, the process returns to step S5 and waits until the encoding process is completed in steps S5 to S7.

When it is determined in step S5 that the transfer request is present, the process proceeds to step S6, and in step S6, it is determined whether or not immediately after the start of the step motor start. That is, since there is a delay in the response of the drive system as shown in FIG.
In consideration of this response delay, it is determined whether or not the number of lines is a predetermined number before the constant speed pitch is sent immediately after the start.

In step S6, if the number of lines is the predetermined number after the start of activation, the process proceeds to step S9. In step S9, the operation of keeping the reading pitch constant is performed. That is, the line marked with X in FIG. 4 is not transferred to the buffer memory, and
The lines to be transferred to the buffer memory are determined so that the read lines are thinned and transferred so that only the marked lines are transferred, the read address of the page memory (4) is controlled, and the process proceeds to step S10. In step S10, the determined line is transferred from the page memory (4) to the buffer memory (5
DMA transfer is performed to a) or (5b), and the process proceeds to step S11. After the transfer request is cleared in step S11, the process proceeds to step S12. In step S12, whether or not the reading stop line is within a predetermined line (N line), that is, in the case of a document or a long object and the reading is stopped as described later, only the transfer from the page memory to the buffer memory is performed thereafter. Become. In step S12, it is determined whether or not this transfer has advanced to the line N lines before the reading stop line. If the minimum transmission time is 10 ms / line and the reading period is 3 ms, the predetermined line number N is 3 times or more as high as the encoding speed, and therefore N is 20.
It is enough to choose. In the case of the predetermined document size, it is determined in step S12 that the reading stop line is not within N lines, and the process proceeds to step S13. In step S13, it is determined whether the transfer of all lines to the buffer memory is completed. Immediately after the transmission, it is determined that the transfer of all the lines is not completed, the process proceeds to step S5, and the above-described operation is repeated. If it is determined in step S13 that the transfer of all lines has been completed, the document is discharged in step S14, and the operation is ended by waiting until the encoding processing of all lines is completed in step S15.

On the other hand, if it is determined in step S6 described above that the document has not just been started, that is, if the document has been fed line by line at a constant pitch, the process proceeds to step S16. Step S
At 16, the read address of the page memory (4) is controlled to perform the DMA transfer from the page memory (4) to the buffer memory (5a) or (5b), and the process proceeds to step S11 and step S1.
From 2 to step S13, step S5 or step S14, the above-described operation is repeated.

Next, when the reading operation proceeds and the document detection sensor detects the document end, in step S3, it is determined that the document end is detected, and the process proceeds to step S17. It is determined whether the number of lines (L lines) corresponding to the document reading position from the detection sensor has been read. If not, it is determined in step S4 whether the page memory (4) is almost full. The process proceeds to step S5, and the above operation is repeated until a predetermined number of lines are read. When it is determined in step S17 that the predetermined number of lines have been read, the process proceeds to step S18, and in step S18, the motor stop flag and the read stop flag are set, the motor and the reading are stopped, the process proceeds to step S4, and the codes of all lines are read. The above-described operation A is repeated from step S4 to S15 until the encoding is completed, and the series of operations is completed after the encoding is completed.

(B) When the transmission original is a long one Even when the transmission original is a long one, the operations of steps S1 to S13 are performed in the same manner as in the case of less than one page. And
In this case, before the transfer of the image signals to the buffer memory of all lines is completed in step S13, the page memory (4) is nearly full in step S4, that is, the page memory (4) stores It is determined that the image signal being displayed has reached the address M, and the process proceeds to step S19. In step S19, the motor stop flag is set, the step motor stops, and the process proceeds to step S20. Step S
At 20, it is determined whether or not a predetermined number of lines have been read after stopping the step motor. That is, as described above, in consideration of the response delay of the drive system, after the stop, it waits until a predetermined number of lines (L lines) are read. Then, the process returns to step S2 until the predetermined number of lines (L lines) are read, and if it is determined that the L lines have been read, the step
The process proceeds to S21, the reading stop flag is set, the reading is stopped, and the process proceeds to step S5.

Subsequently, steps S5, S6 and S16, steps S11 to S13.
In, the image signals are sequentially transferred from the page memory to the buffer memory (5a) or (5b) and sequentially encoded. When the transfer and encoding processing from the page memory progresses and it is determined in step S12 that the transfer and reading from the page memory (4) has reached N lines up to the read stop line, the process proceeds to step S22. In step S22, it is determined whether the document end has been detected. When it is determined that the document end is not detected, the motor stop flag and the reading stop flag are cleared in step S23, the process returns to step S1, and the reading operation is restarted. After the reading operation is restarted, the above-described steps S1 to S22 are repeated until the end of the document is detected and the reading is completed. If it is determined in step S22 that the end of the document has been detected, the process proceeds to step S13, and in steps S13 to S15, the encoding process for all lines ends and the operation ends.

After the motor is stopped, the predetermined line is read and stored in the page memory (4) in consideration of the response delay of the drive system. At this time, the pitch interval of one line is as shown in FIG. Is similar to the inverse response characteristic.

Therefore, when this part is transferred from the page memory (4) to the buffer memory (5a) or (5b), the image signals to be read from the page memory are thinned out so as to have a predetermined pitch and read just as when the motor is started. It is configured to specify the address.

As described above, in the present embodiment, the image signals are thinned out and transferred to the buffer memory so as to be encoded so that the reading pitch becomes constant at a portion where the reading pitch differs due to the response delay at the time of starting and at the time of stopping. The image signal read at a constant pitch is stored in the page memory. Then, the image signal is transferred from the page memory to the buffer memory for encoding while the image signal is stored in the page memory,
Further, the image signal is stored at a constant pitch in the page memory without stopping the step motor during encoding until the page memory is almost full.

(G) Effect of the Invention As described above, according to the present invention, in the reading device of the facsimile apparatus using the step motor as a driving source, the image distortion caused by the response delay between the motor pulse and the document feeding mechanism can be reduced. Since the problem can be solved without applying reverse braking to the motor, the original can be read quietly without causing the motor to overload when replying not only the original within a predetermined size but also the long original, and the first storage means. High-speed reading is possible because the reading can be performed in parallel even during the encoding process until is almost full.

[Brief description of drawings]

FIG. 1 is a block diagram of a facsimile apparatus according to an embodiment of the present invention, FIG. 2 is a timing chart showing transfer timing of image signals, FIG. 3 is a schematic side view showing an example of a reading apparatus, and FIG. FIG. 5 is a response characteristic diagram showing the relationship between the motor pulse and the document feeding displacement, and FIG. 5 is a flow chart showing the operation of the system controller. 1 ... System control unit, 2 ... Reader, 4 ... Page memory, 5 ... Buffer memory circuit, 6 ... Encoding circuit, 7 ... DMA controller.

Claims (1)

[Claims] 1. A reading unit for reading a document sent by a drive system having a step motor as a drive source by photoelectric conversion and outputting a binary image signal, and the image signal read by the reading unit is used for a predetermined number of pages of the document. First storage means for storing the minute portion, encoding means for processing the image signal into a redundancy suppression encoded signal, second storage means for accumulating the image signal to be supplied to this encoding means, the first storage Storage amount detecting means for detecting that the storage state of the means has reached a predetermined amount or more; and the read image signal in the first storage means, or the image signal stored in the first storage means in the second storage means. Before the output of the detection means during reading, the step motor is driven at a constant speed, and an image signal read at a constant document feed speed and a reading cycle is provided. The image signal is transferred from the first storage means to the second storage means in accordance with the encoding speed while being transferred to and stored in the first storage means, and after the output of the detection means, the step motor is stopped. , When the image signal stored in the first storage means is transferred to the second storage means, and when the image signal transfer of the first storage means reaches a predetermined line before the line at which reading is stopped, When the reading operation is restarted and the image signal stored in the first storage means is transferred to the second storage means at the time of starting and stopping the step motor, the interval between the reading lines becomes a predetermined interval, An image reading apparatus for controlling a read address of the first storage means.