JPS5855712B2 - Facsimile scanning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning method for a facsimile machine that uses an optical reading device such as a photodiode array as a scanning device.

Some facsimile transmitters have transmission speed modes (for example,
There are many types available (2 minute mode, 3 minute mode).

However, in order to perform solid-state scanning using a photodiode array (image sensor) or the like, there are the following problems.

In other words, the image sensor integrates the incident light over one scanning period and converts it into a video signal, and the longer the interval between start pulses (scanning start pulses), the greater the amount of integration for the same incident light intensity, which is apparently The sensitivity increases, and conversely, the shorter the interval between start pulses, the lower the sensitivity (this is called charge accumulation mode).

Therefore, unless the start pulse intervals are made the same in some way, the output level of the video signal will change depending on the scanning speed.

Therefore, in order to keep the video signal output level constant, the amount of integration must be kept constant.

Conventionally, this problem was solved by the method shown below.

Figure 1 is a signal waveform diagram showing the relationship between frequency and period.
The figure is a diagram showing the relationship between the charge amount of the image sensor and the storage time in the conventional facsimile scanning method.

First, the first method is to scan at a common multiple of the main scanning frequency and the writing scanning frequency from the image sensor to the memory (hereinafter referred to as the basic scanning frequency), and use dummy pulses at unnecessary timings in each scanning cycle. was used to discharge the image sensor.

Note that the frequency of write scanning from the image sensor to the memory matches the main scanning frequency on the receiving side.

However, in this method, the video output level is only output at the charge amount of the basic scanning frequency (that is, the frequency of a common multiple), for example, 3Hz or 5Hz.

With three types of scanning frequencies such as 6 Hz, the basic scanning frequency is 30 Hz, which is quite high.

As a result, the output level was quite low, which necessitated the use of better-performing light sources and lenses.

Another method is to change the output of the video amplifier each time to keep the video signal output level constant, or to change the amount of light from the light source that illuminates the transmitted document, but due to the characteristics of the image sensor, Since the output of a video amplifier has characteristics of high gain and high speed, it is not desirable to change the state of the amplifier each time, and the method of changing the light intensity of the light source each time takes into account the color characteristics of the fluorescent lamp. Due to the characteristics of fluorescent lamps, it is extremely difficult to maintain light intensity adjustment and stability, which is impractical.

In the present invention, when a solid-state scanning type facsimile transmitting device using the above-mentioned image sensor transmits data to facsimile receiving devices having different main scanning frequencies, a common multiple of the main scanning frequency of each receiving device, for example, 3Hz and 5Hz in FIG. To solve the drawbacks of the method of performing basic scanning at the least common multiple of 15 Hz and discharging the image sensor with a dummy start pulse (hereinafter referred to as dummy pulse) when there is an unnecessary period in each scanning frequency period as shown in Figure 2. In other words, since only the charge amount of the basic scanning frequency is output as the video output level, the video output level becomes smaller as the basic scanning frequency increases.

In other words, the present invention performs basic scanning in unnecessary parts of the basic scanning video signal and adds dummy pulses during this period, and in necessary parts of the video signal, starts pulses based on the highest frequency among a plurality of main scanning frequencies. Since the video signal is output without applying the voltage, the above-mentioned problem is solved.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is an explanatory diagram showing the relationship between charge amount and storage time of a facsimile scanning type image sensor in one embodiment of the present invention.

Conventionally, the storage operation was performed as shown in Figures 2a and 2b, whereas in the present invention, storage is performed as shown in Figures 3a and 3b according to the main scanning frequency on the receiving side. It is.

In Fig. 3, a indicates a scanning period based on 5Hz, which is the higher frequency of 3Hz and 5Hz, and b indicates a scanning period of 3Hz.
It is a figure which shows the scanning period in the case of.

Figure 4 is a block diagram for performing the operations shown in Figure 3;
6 are signal waveform diagrams of this embodiment when transmitting to a facsimile receiving apparatus having main scanning frequencies of 5 Hz and 3 Hz, respectively.

Reference numeral 1 denotes a clock pulse a' and start pulse f generation circuit, which receives as external inputs a clock a having the same frequency as a/ and a start timing pulse d that determines the timing of the start pulse.

First, when a start pulse f is applied to the photodiode array 8, a video signal synchronized with the clock a' is output for a certain number of scan lines (note that the clocks a and a' are the same).

a” (7) frequency is the same).

2 is a selector that selects the clock a" for writing the video signal from the photodiode array 8 into the shift register 10 and the clock b for reading from the shift register 10, and shifts the clock k for speed conversion (clock a" 51 is b). This is a circuit that sends data to the register 10.

The selection of the clocks a'' and b is performed by the output signal k of the selector 2 which inputs the select signal C, and when the select signal C is low, the video signal is written from the photodiode array 8 to the shift register 10 and is high.
It is read out at hour h.

In other words, the select signal C serves as the scanning timing.

4 is a flip-flop which is set by the start timing d, reset by the carrier g of the counter 5 which is counting at the rising edge of the video enable signal e, opens the gate γ by the signal for the set period, and starts the start pulse i. is applied to the photodiode array 8.

Reference numeral 6 denotes an enable signal generation circuit which counts a predetermined number from the start pulse f and the clock a/, and converts the video signal j output from the photodiode array 8 into an enabled image via the video amplifier 12 and shift register 10. Create a signal t.

Next, a method of determining the count setting value M of the counter 5 will be explained.

Each receiver has a plurality of main scanning frequencies [(Fl.

F2-...Fn) Hz, l is 3Hz, 5H
z, of which the highest frequency (FmaXH2) is 5Hz,
The least common multiple frequency (FOMH2) of each main scanning frequency,
That is, the fundamental frequency is 15 Hz, and the arbitrary frequency FiHz is 3 Hz or 5 Hz.

Here, the time required to output a video signal from an optical reading device that reads images from a document is 10M71m, x 1/
FcM(sec)-”/Fmax(sec).

Therefore, if the fundamental frequency (FC!M) is used as a reference, in this embodiment, the same line is repeated FOM/Fmax times, that is,
The scan will be performed three times, and the time will be three cycles of FOMn2.

Therefore, the enable period of the start enable signal,
That is, the setting value M of the counter 5 that sets the number of times of application of the dummy pulse is the case when transmitting to the receiver with F i =5 and when transmitting to the receiver with i3.

The start timing pulse generation circuit 3 is FiHz.

That is, a start timing pulse d is generated at the falling edge of the signal C to synchronize the entire system.

That is, the clock and start pulse generation circuit 1 and F-F4 are set by the start timing pulse d, and the counter 5 is initialized to the counter setting value M.

First, the video output j of the photodiode array 8 output at the first pulse is sent to the shift register 10 by a clock pulse a.
From the second pulse, the clock is switched to clock b by the selector 2, and the video signal is read out as the output.

A start pulse i is applied as a dummy pulse to the photodiode array 8 from the second pulse until the counter 5 counts M pulses, thereby discharging the photodiode array.

When Fi=5, no dummy pulse is needed, so
As shown in FIG. 5
It increases gradually line by line as shown in the figure.

On the other hand, when Fi=3, two dummy pulses are applied to the photodiode array 8 at time t2 after the elapse of the time t1 for reading the signal from the photodiode array 8, as shown by signal i4 in FIG. The charge amount also becomes '0'' each time as shown in section A of FIG. 6X.

Then, when the counter 5 counts M, the output of F/F4 becomes high, the gate door closes, and the start pulse i
is no longer applied to the photodiode array 8, and the charge in the photodiode array 8 is accumulated until the next start pulse is applied.

This accumulation time t3 is one period of 5 Hz, that is, three periods of the basic scanning frequency of 15 Hz, as shown in FIGS. 5 and 6.
As shown by X in the figure, the case of Fi=5 and the case of Fi=3 are the same.

This accumulation time t3 is given by FmaxHz as mentioned above, but since the following relationship always holds, it is necessary to accumulate a sufficient amount of charge compared to the conventional method of accumulating the photodiode array at the basic cycle. Therefore, the output signal t can also maintain a high level.

As described above, the present invention enables a solid-state scanning type facsimile transmitter using an image sensor to transmit data to facsimile receivers having different main scanning frequencies.
When transmitting to a facsimile receiver having an arbitrary main scanning frequency (FiHz) among (Fl, F2...Fn)Hz:), FcM (1/ In the part where dummy pulses are applied Fi1/Fma
It accumulates data in the image sensor by scanning the time of the ax cycle, and it is possible to send stable video signals even to facsimile receivers with different main scanning frequencies, and it also allows video signals to be transmitted at maximum speed. Since it can be obtained with high efficiency, it has the effect that the performance of the light source lens can be made rough.

[Brief explanation of the drawing]

FIG. 1 is a signal waveform diagram showing the relationship between frequency and period, FIG. 2 is a diagram showing the relationship between image sensor charge amount and storage time in a conventional facsimile scanning method, and FIG. 3 is an embodiment of the present invention. Figure 4 shows the relationship between charge amount and storage time of a facsimile scanning type image sensor in
This figure is a block diagram for performing the operation shown in FIG. 3, and FIGS. 5 and 6 are signal waveform diagrams of this embodiment when transmitting to a facsimile receiving apparatus having main scanning frequencies of 5 Hz and 3 Hz, respectively. 1... Clock and start pulse generation circuit, 2
...Selector 3...Start timing pulse generation circuit, 4...Flip-flop, 5...Counter, 6...Enable signal generation circuit, 1,9゜11... Ant game, 10... Schiff amplifier. 8...Photodiode atresistor, 12...Video

Claims (1)

[Claims] 1. A plurality of main scanning frequencies (-p 1. F 2...
...Fn)Hz, and when transmitting at any main scanning frequency FiHz among the main scanning frequencies, if the highest frequency among the main scanning frequencies is Fma In each period of the main scanning frequency, FcM(
Discharging the image sensor every time a dummy nozzle is applied 1/Fi 1/"max) times, and then accumulating the video signal in the image sensor for a period of F.M/Fmax of the F.Mn2, A facsimile scanning method that then reads data from the image sensor.