JPS6231655A - Paper end mark detector - Google Patents

Abstract

PURPOSE:To detect the paper end mark reliably by dividing the photoelectrically converted output voltage from first photo-sensor for photoelectrically converting the light reflected from the ground color section of paper on the basis of threshold level of comparator to be detected by means of a resistor. CONSTITUTION:It is comprising first photo-reflector PR1 constructed with first photo-transistor TR1 for detecting existence of recording paper and first light emission diode D1 and first comparator CMP1 for comparing the photoelectrically converted voltage from first phototransistor TR1 with a threshold level to be fed from voltage source VT to produce a binary signal indicating the existence of recording paper. Furthermore, second photo-reflector PR2 constructed with second photo-transistor TR2 for detecting the endmark of recording paper and second light emission diode D2, resistors R5, R6 for dividing the photoelectrically converted output voltage from first transistor TR1 and second comparator CMP2 for comparing the photoelectrically converted output voltage from second phototransistor TR2 with said divided voltage to produce a binary signal indicating the existence of endmark are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an end mark detection device for recording paper in facsimile machines and the like.

[Conventional technology]

The light emitted from a light-emitting diode, etc. is irradiated onto the recording paper to be detected, and the resulting reflected light is photoelectrically converted by a phototransistor. The voltage is proportional to the amount of reflected light, so the background color (white) of the recording paper and the voltage are proportional to the amount of reflected light. A voltage difference occurs between the photoelectric conversion output voltages (color width of the end mark).

The conventional paper end mark detection device identifies the end mark by comparing the above-mentioned photoelectric conversion output voltage using a threshold appropriately set within the difference between these two voltages and converting it into a z value.

[Problem that the invention seeks to solve]

Figure 4 is a general graph showing the characteristics of the photoelectric conversion output voltage V with respect to the distance LK between the phototransistor and the recording paper.
Curve A shows the background color of the recording paper, curve B shows the characteristics for the end mark, and the shaded area shows the displacement due to variations in the phototransistors. In this graph, the bias current of each phototransistor is adjusted so that the photoelectric conversion output voltage V for the end mark is at the same level when the distance between the phototransistor and the recording paper is the minimum.

As is clear from this graph, the fixed threshold value that allows the background color of the recording paper and the end mark to be distinguished with sufficient margin is around dotted line C, and the distance between the phototransistor and the recording paper @
L is kept short.

In this way, the conventional paper end mark detection device described above is
As the distance between the phototransistor and the recording paper, which is a reflector, increases, the magneto-optical conversion output voltage will drop rapidly, and the characteristics of the phototransistor will vary widely. The disadvantage is that it has to be kept short.

[Means for solving problems]

The paper end mark detection device of the present invention irradiates light onto the ground color portion of paper and converts the reflected light into electricity.
A sensor, a first comparator that compares the photoelectric conversion output voltage of the first photo sensor with a predetermined threshold value and determines the presence or absence of paper; a second photosensor that photoelectrically converts the reflected light, and a photoelectric conversion output voltage of the second photosensor is compared with a partial voltage value of the photoelectric conversion output voltage of the first photosensor,
It has a second comparator that discriminates between the ground color part of the paper and the end mark.

In this way, the threshold value of the comparator that detects the paper end mark is not a fixed value as in the conventional case, but the photoelectric conversion output voltage of the first photo sensor that photoelectrically converts the partially reflected light of the background color of the paper. Since the voltage is divided by a resistor, the threshold voltage of the second comparator is always the same even if the distance between the phototransistor and the recording paper has to be increased or the characteristics of the phototransistor vary. It is between the photoelectric conversion output voltage of the first photo sensor and the photoelectric conversion output voltage of the second photo sensor, and it becomes possible to detect the end mark well.

〔Example〕
First, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the paper end mark detection device of the present invention.

The present embodiment includes a first photoreflector PR composed of a first phototransistor TR for detecting the presence or absence of recording paper, a first light emitting diode p, and a resistor for applying an appropriate bias to the first photoreflector PR. R1 and the voltage source V〒
and a first comparator CMPi that compares the photoelectric conversion output voltage of the first phototransistor TR1 with the threshold value given by the voltage source VT and outputs a binary signal indicating the presence or absence of the memory paper; The second one detects the paper end mark.
phototransistor T- and a second light-emitting diode D
, a second photoreflector PR1 configured with a resistor R8 and a melon that apply an appropriate bias to the second photoreflector PR1,
The resistor that divides the photoelectric conversion output voltage of the first phototransistor TR1 is also
R2, ), and a second comparator CMP that compares this divided voltage value with the magneto-optical conversion output voltage of the second phototransistor T- and outputs a binary signal indicating the presence or absence of the end mark.
It is made up of. Figure 2 shows memory paper, end marks, 1. Second photo reflector PR,,pRl
It is a figure showing the positional relationship of.

FIG. 8 shows the phototransistor TR in this embodiment.
□ is a graph showing the characteristics of photoelectric conversion output voltage V with respect to the distance between TR1 and recording paper. Here, the first. The photoelectric conversion output voltage V with respect to the end mark of the second phototransistor TRI tTR* is a resistance of -1R, respectively.
By adjusting 4, the distance to the recording paper is adjusted to be the same when the distance is at its minimum, and the curves A and 4 are adjusted to be the same when the distance to the recording paper is at its minimum, and the curves A and 4 are adjusted for the ground color and end mark of the recording paper, respectively, as in the case of Fig. 8. (The shaded area indicates displacement due to variations.) Also, as mentioned above, the reference voltage of the second comparator CMP for detecting the end mark is the voltage of the first photo that photoelectrically converts the reflected light of the background color of the recording paper. - Since it is the value obtained by dividing the photoelectric conversion output voltage of the transistor TR by the resistor island and the bird, the curve E is always between the curve A and the curve B. Therefore, the first
．． Even if the distance between the second phototransistors TR1, TR2 and the recording paper becomes large, or the characteristics of the first and second phototransistors vary, the photoelectric conversion output voltage of curves A and B may change. , the output voltage of curve E changes in the same way, and the end mark can be identified.Furthermore, the threshold of the first comparator CMP, which detects the presence or absence of recording paper, is the same as that of the first comparator when there is no recording paper. Since the photoelectric conversion output voltage of the phototransistor TR has a value close to zero, a low value such as the voltage VT shown by the dotted line is sufficient.

〔Effect of the invention〕

As explained above, in the present invention, the threshold value of the comparator for detecting the paper end mark is not a fixed value as in the past, but a first photo centimeter that photoelectrically converts the reflected light from the ground color part of the paper. Since the photoelectric conversion output voltage is divided by resistors, even if the distance between the phototransistor and the recording paper becomes large and the photoelectric conversion output voltage changes suddenly
Further, even if there are large variations in the photoelectric conversion output voltage of the phototransistor, there is an effect that the paper end mark can be reliably detected.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the paper end mark detection device of the present invention, and FIG.
FIG. 8 is a perspective view showing the relative positions of the reflectors PR, PR2, and the distance between the phototransistors PR, PR, and the recording paper in the embodiment of FIG. 1, and the photoelectric conversion of the phototransistors PR1-PRt. A graph showing threshold voltage characteristics of the output voltage V and the second comparator CMP,
FIG. 4 is a graph showing the characteristics of the distance between the phototransistor and recording paper of the conventional detection device and the phototransistor photoelectric conversion output voltage V. PR, ......First photo reflector. TR, ......lth phototransistor. Dl......First light emitting diode. R8, -...Bias resistance, PR1.
...Second photo reflector. T-...Second phototransistor. D, . . . second light emitting diode. R,,R,...Bias resistance. Bird, R6......divider resistance. CMP,...first comparator. CMP, ... second comparator. 77,...Threshold voltage. Patent applicant: Japan Electric Co., Ltd. Company representative: Patent attorney Uchihara, Press, Shinryo

Claims (1)

[Scope of Claims] A first photo sensor that irradiates light onto the ground-colored portion of paper and converts the reflected light into electricity; and a photoelectric conversion output voltage of the first photo sensor that is set to a predetermined threshold value. A first comparator that compares the paper to determine the presence or absence of paper;
A second photo sensor photoelectrically converts the reflected light, and the photoelectric conversion output voltage of the second photo sensor is compared with the partial pressure value of the photoelectric conversion output voltage of the first photo sensor, and the background color of the paper is determined. A paper end mark detection device having a second comparator that discriminates between a portion of the paper end mark and an end mark.