JPH0240538A - Variable density detecting apparatus - Google Patents

Abstract

PURPOSE:To prevent malfunction, to obtain a stable output and to make it possible to detect the index of a material to be detected whose variable density ratio is small by receiving both light beams from a light emitting element with two photodetectors, and outputting said output into a detecting circuit. CONSTITUTION:A light emitting element 13 has directivity in two directions toward the following positions: a first illuminated position A where an index 12 of a material to be checked 11 which relatively moves on a main body 10 passes; and a second illuminated position B where a part other than the index 12 passes. First and second reflected light beams 14 and 16 from the positions A and B are received with first and second photodetectors 15 and 17. Outputs VE and VL from the photodetectors 15 and 17 are compared in a detecting circuit 18, and the index 12 is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a density detection device, and relates to an improved structure for detecting end marks on facsimile recording paper, for example.

<Prior art> As shown in Fig. 8.9, a conventional grayscale detection device for facsimile end mark detection includes a grayscale detection device main body 1, a light emitting element 2 having unidirectional directivity, and light from the light emitting element 2. It is composed of a light receiving element 3 that receives light and a detection circuit 4.

Then, as shown in FIG.
The detection circuit 4 compares the standard output voltage VL of the light receiving element 3 with the output voltage VE of the light receiving element 3 to detect the index 6 of the object 5.

At this time, the standard output voltage VL of the light receiving element 3, the output voltage VEI of the light receiving element 3 when detecting the index 6, and the voltage VE of the light receiving element 3 when detecting an index other than the index 6.
2 is set as VEl<VL<VF6.

Problems to be Solved by the Invention 〉However, in the conventional density detection device, the standard output voltage VL of the light receiving element 3
As shown in FIG. 9, is fixed in the detection circuit 4 by dividing the voltage by the resistors R1 and R2, and is initially adjusted by changing the gain of the variable resistor R3. When the voltage decreases, the output voltage VE2 of the light-receiving element 3 when detecting an index other than the index 6 after a certain period of time is
As shown in FIG. 11, the standard output voltage VL of the light-receiving element 3 is lowered, and the relationship of VEI < VL < VF6 cannot be maintained, and as shown in FIG. This will result in malfunction.

Furthermore, even if the output of the light emitting element decreases due to difficulty in detecting the index 6 and the object 5 with a small contrast ratio other than the index 6, stable output can be maintained without malfunction. It is an object of the present invention to provide a density detection device that can detect an index of an object to be detected with a small density ratio.

<Means for Solving the Problems> The means for solving the problems according to the present invention, as shown in FIGS. A light emitting element 13 that has directivity in both directions between a first irradiation position A through which objects 12 pass and a second irradiation position B through which objects other than the index 12 pass, and a first reflected light 14 from the first irradiation position A. A first light receiving element 15 that receives light, a second light receiving element 17 that receives second reflected light 16 from the second irradiation position B, an output VE of the first light receiving element 15, and an output VL of the second light receiving element 17. and a detection circuit 18 that detects the index 12 by comparing the index 12 and the index 12.

<Operation> In the above problem solving means, the density detection device irradiates the object 11 with bidirectional light from the light emitting element 13, and directs the first reflected light 14 from the first irradiation position A to the first light receiving element 15. The second reflected light 16 from the second irradiation position B is received by the second light receiving element 17. Then, the detection circuit 18 compares the outputs of the first light receiving element 15 and the second light receiving element 17 to detect the index 12 of the object 11 to be detected.

At this time, even if the output VE of the first light receiving element 15 decreases due to a decrease in the output of the light emitting element 13 due to aging, etc., the bidirectional light of the light emitting element 13 is transferred to the first and second light receiving elements 15.17.
receive light and output their outputs VE and VL to the detection circuit 18, so the output VL of the second light receiving element 17 can be reduced following the reduction in the output VE of the first light receiving element 15.

<Examples> Examples of the present invention will be described below with reference to the drawings. 1st
The figure is a vertical sectional view of the density detection device according to the first embodiment of the present invention, and the second
The figure is an electric circuit diagram of the detection circuit, FIG. 3 is a plan view showing the state in which the detection circuit detects objects other than the index of the object to be detected, FIG. 4 is a plan view showing the state in which it detects the target, and The figure shows the relationship between the output voltages of the first light-receiving element and the Z detection circuit when detecting an index and something other than the index. , is a diagram showing the relationship between the output voltages of the second light receiving element.

As shown in the figure, the density detection device for facsimile end mark detection of the present invention includes a density detection device main body 10;
11 indicators (e.g. facsimile end mark) of a detected object (e.g. facsimile recording paper) that moves relatively above
A light emitting element 13 that has directivity in both directions between a first irradiation position A through which objects 12 pass and a second irradiation position B through which objects other than the index 12 pass, and a first reflected light 14 from the first irradiation position A. The first light receiving element 15 that receives light and the second irradiation position Bh-
a second light receiving element 17 that receives the second reflected light 16 from the second light receiving element 17; and a detection circuit 1 that detects the index 12 by comparing the output VE of the first light receiving element 15 and the output VL of the second light receiving element 17.
It consists of 8.

The main body 10 is formed into a rectangular parallelepiped, as shown in FIG. In the main body 10, the light emitting element 13 disposed at the center, the first light receiving element 15 disposed on the side of the first irradiation position A of the light emitting element 13, and the second irradiation position B.
The second light receiving element 17 arranged on the side is attached.

As shown in FIG. 2, the detection circuit 18 includes a variable resistor R1 that initially adjusts the output voltage VL of the second light receiving element 17, an output voltage VE of the first light receiving element 15, and an output voltage VL of the second light receiving element 17. It is composed of an amplifier 19 which outputs a detected output voltage (2) of 0 by comparing the two, and resistors R2, R3, and R4.

The variable resistor R1 previously adjusts the output voltage VL of the second light receiving element 17 to the first light receiving element 15 when detecting the index 12.
The initial adjustment is made to have an intermediate value between the output voltage VEI of the first light receiving element 15 and the output voltage VE2 of the first light receiving element 15 when detecting an object other than the index 12, that is, VEl<VL<VF6.

The density detection device irradiates bidirectional light from the light emitting element 13 onto the object 11 to be detected, and a first reflected light 1 from the first irradiation position A.
4 is received by the first light receiving element 15, and the second reflected light 16 from the second irradiation position B is received by the second light receiving element 17. Then, the detection circuit 18 compares the outputs of the first light receiving element 15 and the second light receiving element 17 to detect the index 12 of the object 11 to be detected.

For example, as shown in FIG.
1, the first light receiving element/element 15 receives the first reflected light 14, so the output voltage V of the first light receiving element 15
E is the output voltage VL of the second light receiving element 17, as shown in FIG.
, the amplifier 19 in the detection circuit 18 outputs a high detection output voltage ■O, and the index 1 of the detected object 11
2 is detected.

In addition, as shown in FIG.
, the first light receiving element 15 receives the first reflected light 1
4, the output voltage VE of the first light receiving element 15
As shown in FIG.
is detected.

At this time, even if the output of the light emitting element 13 decreases due to aging, etc., the light emitting element 13 having bidirectional finger directionality is installed in the main body 10, and the light emitting element 13 from the first irradiation position A of the light emitting element 13 is The first reflected light 14 is received by the first light receiving element 15, and the second reflected light 16 from the second irradiation position B of the light emitting element 13 is received.
is received by the second light receiving element 17, so the second light receiving element 17
As shown in FIG. VEI<VL<VF6 can be maintained.

That is, in the density detection device of the present invention, since the light receiving elements 15 and 17 each receive the bidirectional reflected light 14.16 of the light emitting element 13 and output it to the detection circuit 18, the output of the light emitting element 13 due to aging etc. Even if the output voltage VE of the first light receiving element 15 decreases due to the decrease, the output voltage VL of the second light receiving element 17 can be reduced accordingly.

Therefore, even if the output of the light emitting element decreases due to aging or the like, a stable output can be obtained without malfunction, and an index of an object with a small contrast ratio can be detected.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a longitudinal sectional view of a density detection device according to a second embodiment of the present invention.

As shown in the figure, in the density detection device of this embodiment, the first and second light receiving elements 15, 17 are not disposed with the light emitting element 13 in between, as in the first embodiment, but the first and second light receiving elements 15, 17 are The light receiving elements 15 and 17 are arranged without sandwiching the light emitting element 13. The structure, function, and effect of the pond are the same as in the first embodiment.

It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that many modifications, changes, and changes can be made to the above-described embodiments within the scope of the present invention.

For example, in this embodiment, the variable resistor R1 is used to initially adjust the output voltage VL of the second light receiving element 17, but a simple ordinary resistor is used to adjust the output voltage so that the relationship VEI < VL < VF6 can be maintained. Even if the initial adjustment of VL is performed, the object of the present invention can be achieved.

<Effects of the Invention> As is clear from the above description, according to the present invention, there is a first irradiation position through which an indicator of an object to be detected moving relatively on the main body passes, and a position other than the indicator in the main body of the density detection device. A light emitting element that has directivity in both directions with respect to a second irradiation position passing through, a first light receiving element that receives the first reflected light from the first irradiation position, and a second reflected light from the second irradiation position. A detection circuit compares the output of the first light-receiving element and the output of the second light-receiving element to detect an index. The output of the second light receiving element can be decreased following the decrease in the output of the second light receiving element.

Therefore, even if the output of the light emitting element decreases due to aging etc., stable output can be obtained without malfunction, and it has the excellent effect of being able to detect indicators of objects with a small contrast ratio. .

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a density detection device according to a first embodiment of the present invention;
FIG. 2 is an electric circuit diagram of the detection circuit, FIG. 3 is a plan view showing the state in which the detection circuit detects objects other than the index of the object to be detected, and FIG. 4 is a plan view showing the state in which it detects the target. Figure 5 is a diagram showing the relationship between the output voltages of the first light receiving element and the detection circuit when an indicator is detected and an object other than the indicator is detected;
The figure also shows the relationship between the output voltages of the first and second light-receiving elements as the output of the light-emitting element decreases due to changes over time.
FIG. 7 is a vertical cross-sectional view of a grayscale detection device according to a second embodiment of the present invention, FIG. 8 is a vertical cross-sectional view of a conventional grayscale detection device, FIG. 9 is an electrical circuit diagram of the detection circuit, and FIG. FIG. 11 is a plan view showing the installed state, and FIG. 11 is a diagram showing the change over time in the output voltage of the light-receiving element, and FIG. 12 is a diagram showing the output voltage of the detection circuit. 10: Density detection device main body, 11: Object to be detected, 12: Index, 13: Light emitting element, 14: First reflected light, 15: First light receiving element, 16: Second reflected light, 17: Second light receiving element 17 .1
8: Detection circuit. Applicant Sharp Corporation

Claims (1)

[Claims] A light/darkness detection device main body, a light emitting element having directivity in both directions: a first irradiation position through which an indicator of an object to be detected moving relatively on the main body passes, and a second irradiation position through which objects other than the indicator pass; , a first light receiving element that receives the first reflected light from the first irradiation position; a second light receiving element that receives the second reflected light from the second irradiation position; 1. A grayscale detection device comprising: a detection circuit that detects the index by comparing outputs of two light receiving elements.