JPH0113264B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document reading device such as a facsimile machine, and more particularly to a document reading device in which the reading sub-scanning speed changes slowly.

Conventionally, as this type of device, Fig. 1 and Fig. 2 have been used.
I got what is shown in the figure. In Fig. 1, 1 is a document to be read, 2 is a light source for illuminating the document, 3 is a lens, and 4 is a
An image sensor such as a CCD image sensor; 5 a transport roller for transporting the original 1; 6 a control circuit that controls lighting of the light source 2 and scanning of the image sensor 4;
7 is a lighting circuit for the light source 2;

FIG. 2 shows the image sensor 4 using the control circuit 6 shown in FIG.
and the timing of controlling the light source 2. In the figure, a indicates the transport state of the original 1, that is, the position of the scanning line with respect to time, b indicates the lighting timing of the light source 2, c indicates the scanning of the image sensor 4, and d indicates the signal output.

Next, the operation will be explained. The original 1 is illuminated by a light source 2, the illuminated portion is imaged onto the image sensor 4 by the lens 3, the original 1 is read, and the original 1 is conveyed by the conveyance roller 5.
can be read on. The document 1 is conveyed smoothly as shown in FIG. 2a. As a result, the sub-scanning speed changes as shown in the figure. In such a case, if an attempt is made to read the document 1 using specially spaced scanning lines, the sub-scanning timing will not be at regular intervals, as shown in the figure. Therefore, scanning is performed as follows. That is, when the sub-scanning timing comes, the light source 2 is turned on for a certain period _t1 , and after that, the next sub-scanning timing is at time _T1.
If it comes later, at this point the light source 2 is turned on again and scanning of the image sensor 4 is started. During this period, the signal output obtained from the image sensor 4 is the one accumulated in the period _T1 shown in FIG. 2d,
In other words, the document was read at the timing of the previous sub-scanning. In the next period T ₁ as well, the light source 2 is turned on for a certain period t ₁ and then turned off, as in the previous period. This series of operations is performed every time the sub-scanning timing is input, and read signals of scanning lines at regular intervals are obtained.

Conventional document reading devices are configured as described above, and the light source is controlled so that it is turned on only for a certain period of time from the sub-scanning timing and is turned off at other times. The filament cools during the time the light is turned off, and the next time it is turned on, a load is placed on the filament, shortening the life of the tube.The temperature of the tube also decreases, making it difficult to turn on the lamp, and even when the lamp is turned on, the amount of light is unstable. There were some drawbacks.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional ones.By shortening the period when the light source is turned off, the temperature drop in the filament and tube is reduced, thereby extending the tube life. The object of the present invention is to provide a document reading device that can provide long, stable lighting and stable illumination brightness.

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

FIG. 3 shows the configuration of a document reading device according to an embodiment of the present invention, and in the figure, the same reference numerals as in FIG. 1 indicate the same parts. A control circuit 6' controls lighting of the light source 2 and scanning of the image sensor 4.

4 and 5 are for explaining the operation of the control circuit 6' of FIG. 3.

Next, the operation of this embodiment will be explained. As shown in FIGS. 4 and 5, the control operation of the control circuit 6' differs depending on whether or not the sub-scan timing is input during effective scanning of the image pickup device. First, in the case of FIG. 4, when the image sensor 4 is scanned and an effective read signal is obtained, that is, during the period when the document 1 is read and the accumulated signal is output at the previous sub-scan timing, the next sub-scan timing is applied. If entered,
Similar to the conventional device, the light source 2 is turned on for a certain period of time _t1 ,
Then the lights go out. Subsequently, after both the scanning period t ₂ of the image sensor 4 and the light source lighting period t ₁ have ended, the next scan (period t ₃ ) of the image sensor 4 is started. The signal output in this scanning is accumulated during the period _T1 , and therefore, the document 1 is read during the period _t1 when the light source 2 is turned on after the sub-scanning timing is input. Therefore, it is a valid read signal.

Next _, in the case of FIG. 5, the sub-scanning timing does not come during the scanning period t ₅ of the image sensor 4 during which an effective read signal is obtained; After the scanning is completed, the light source 2 is turned on. Until the subsequent sub-scanning timing is input, scanning of the image sensor 4 is free, that is, scanning may or may not be performed. Next, when the sub-scanning timing is input, scanning of the image sensor 4 is simultaneously started. Scan t ₆ during this period is for discharging unnecessary signals that have been accumulated in the image sensor 4 up to that time, and the signals obtained here are invalid and have no relation to the reading of the original 1. be. The light source 2 is turned off after a certain period t ₄ (t ₄ =t ₁ in this case) after the scanning of the image sensor 4 starts. Next, after the scanning of the image sensor 4 is completed, the next scanning is started. The signal obtained in this scanning (period t ₇ ) was accumulated during the same period T ₂ as the immediately preceding scanning period t ₆ of the image sensor 4, and during this period, the light source 2 was turned on for the period t ₄ . Therefore, the original 1 is read when the sub-scanning timing is input. That is, the signal obtained during this period _t7 is valid for reading the original 1.

As described above, in any case, a signal is obtained that indicates that the document 1 was read correctly without being missed at the time when the sub-scanning timing was input.

Note that the light source lighting period t ₁ in FIGS. 4 and 5,
_t4 is the period during which the light source 2 is actually lit, and is not the period of the control signal sent from the control circuit 6' to the lighting circuit 7. In other words, the light source 2 is turned on (or turned off) after the control signal is input to the lighting circuit 7 until the lighting voltage is applied to the light source 2 (or the voltage is turned off), and after the lighting voltage is applied (or after the voltage is turned off). ), there is generally a delay, so the control signal from the control circuit 6' to the lighting circuit 7 must take this into consideration.

For example, in the case of FIG. 4, the sub-scanning timing is input, a lighting signal is output from the control circuit 6', and the light source 2
There is a delay t _d1 until the light source 2 turns on, and there is a delay t _d2 until the light source ₂ turns off after the light-off signal is output. The length of the control signal from ' (the time from the lighting signal to the lighting signal output) is t ₁ + t _d1 −
Must be t _d2 .

In the case of Fig. 5, the sub-scanning timing is input,
The light source 2 is already turned on at the time when the image sensor 4 starts scanning. Similarly to the above, if the delay from when the control circuit 6' outputs the light-off output until the light source 2 is turned off is t _d2 , then in order to turn off the light source 2 after a certain period of time t ₄ after the start of scanning of the image sensor 4, Control circuit 6'
The light-off signal from t ₄ − after the start of scanning of the image sensor 4
Must be output in t _d2 .

An example of scanning using the above control operation is shown in FIG. 6 below. As can be seen from the figure, compared to the conventional example shown in Fig. 2, the light source 2 is turned on more during the period t _x shown in Fig. 6, and the temperature of the filament etc. is prevented from dropping during this period. There is.

In the embodiment shown in FIG. 6, the image sensor 4 is not scanned during the period t _x , but as shown in the explanation of the operation, the image sensor 4 is scanned during the period t _x . You can get exactly the same effect.

In the configuration shown in FIG. 3, the original 1 is conveyed, but as shown in FIG. 7, the original 1 is fixed in reverse and
The optical section 8 that integrates the light source 2, lens 3, and image sensor 4 may be moved.

As described above, according to the present invention, when controlling the lighting of the light source and the scanning of the image sensor in accordance with the timing of sub-scanning, the turn-off time of the light source is shortened, so that the temperature of the filament and tube increases. Since the fall of the light source can be suppressed and the load placed on the filament during lighting can be reduced, the life of the light source can be extended. At the same time, a stable amount of light can be obtained when the light is turned on, and an adverse effect on the read signal due to instability in the amount of light can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional document reading device, FIG. 2 is an explanatory diagram of the control operation of the control circuit shown in FIG. 1, FIG. 3 is a block diagram of a document reading device according to an embodiment of the present invention, and FIG. 5 and 5 are explanatory diagrams of the control operation of the control circuit of FIG. 3, FIG. 6 is an explanatory diagram of the operation of the entire apparatus of FIG. 3, and FIG. 7 is a configuration diagram showing another embodiment of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Original document, 5... Conveyance roller (document conveyance means), 2... Light source, 7... Lighting circuit, 4... Image pickup element, 6'... Control circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A document transport means for transporting a document at a speed that slowly changes, a light source for illuminating the document, a lighting circuit for lighting the light source, and an image sensor for reading information on the surface of the document. , a control circuit that controls scanning of the image sensor and lighting of the light source, and the control circuit controls the image sensor while scanning the image sensor (hereinafter referred to as effective scanning) to obtain an effective read signal. When it is time to read one scanning line of the document (hereinafter referred to as reading time), the light source is turned on for a predetermined period of time after the reading time, and after the light source is turned off and the above-mentioned effective scanning is completed, effective scanning is performed again. and
In cases other than the above, the light source is turned off during a valid scan, the light source is turned on after the valid scan is completed, the image sensor is scanned at the next reading time, an invalid scan is performed, and the image sensor is scanned. The document reading device is characterized in that the light source is turned off after a predetermined period of time has elapsed since the start of scanning, and effective scanning is performed after the light source is turned off and the ineffective scanning is completed. 2. The time between the light source turn-on signal and the light-off signal output from the control circuit when the reading time comes while the image sensor is performing effective scanning, and the time between the light source turn-on signal and the light-off signal output from the control circuit, and 2. The document reading device according to claim 1, wherein the time from the start of scanning to the output of the light-off signal from the control circuit is the same time.