JPS6355490A - Detecting system for stain of photosensor - Google Patents

Abstract

PURPOSE:To detect a proceeding degree of a stain of a photosensor, by dropping a driving voltage of a light emitting element, setting artificially the photosensor to a state being equivalent to a stained state, and comparing an output of a light receiving element at that time and a reference value. CONSTITUTION:A driving voltage variable means 7 consists of a resistance R, and a switch SW which has been connected in parallel to said resistance, connected in series between an LED 1 and a power source, the switch SW is set to a closed state in a usual state, and both ends of the resistance R are short-circuited. Accordingly, the resistance R is not related at all to an operation of a photosensor. Subsequently, at the time of checking a stain of the photosensor, the switch SW is opened, and the resistance R is interposed and inserted between the LED 1 and the power source. As a result, a driving voltage of the LED 1 drops by a voltage effect portion in the resistance R. Accordingly, the light quantity of an emitted light 2 of the LED 1 drops, and an output voltage Vout of a light receiving element 3 in case when an object to be detected 4 does not exist rises. By comparing the voltage Vout at this time and a reference voltage VS, by a comparator 5, a proceeding state of a stain of the photosensor can be detected.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a photosensor that includes a light-emitting element and a light-receiving cable that receives light emitted from the light-emitting element, and generates an output corresponding to the amount of light received by the light-receiving element. , the drive voltage of the light emitting element is lowered to virtually bring the photosensor into a state equivalent to the contaminated state, and the progress of the staining of the photosensor is determined from the comparison result between the output of the light receiving element at that time and the output reference value. The degree can be detected.

[Industrial application field]

The present invention relates to a photosensor that includes a light emitting element and a light receiving element that are arranged opposite to each other.

[Conventional technology]

A photosensor that includes a light-emitting element and a light-receiving element disposed facing each other so as to receive the light output from the light-emitting element, when an object enters between the pixel elements and blocks the light emitted from the light-emitting element, Utilizing the change in the output of the light receiving element, it is often used to detect objects in home appliances, industrial products, and automated equipment such as cash dispensers.

FIG. 3 is a basic circuit configuration diagram for explaining the operation of the above-mentioned photosensor. In the figure, 1 is a light emitting element, for example an LED (photodiode), and 2 is a light emitting element 1.
3 is a light receiving element such as a phototransistor,
Reference numeral 4 indicates an object to be detected, such as a banknote in a cash dispenser, for example. Further, Rt and Rt are load resistances of the LEDI and the phototransistor 2, respectively.

Light 2 emitted from a light emitting element such as a photodiode (LED) 1 is received by a light receiving element 1 such as a phototransistor 3, and an output current 2 corresponding to the amount of light is obtained.

This output current 1 changes in proportion to the amount of light received, so when the object to be detected 4 enters between the light emitting element 1 and the light receiving element 3, the amount of light received by the light receiving element 3 is blocked or reduced, so the amount of light received is The output current of element 3 decreases, and the load resistance RL
The voltage drop at V becomes smaller, and the output voltage V. UT rises.

FIG. 4 is a diagram showing the detection characteristics of the above-mentioned photosensor.
Part B represents the case where the object to be detected 4 does not exist between the light emitting element 1 and the light receiving element 3, part B represents the case where the light 2 entering the light receiving element is completely blocked by the object to be detected 4, part 0. indicates a state in which a portion of the light 2 is blocked by the moving detected object 4.

In this way, the output voltage of the light-receiving element 3 is ■. LIT changes depending on the presence or absence of the detected object 4. Therefore, as shown in FIG. 2, by setting an appropriate reference voltage V, the output voltage ■. L
By comparing IT with this, it is possible to know the presence or absence of the detected object 4.

Note that 5 shown in FIG. 2 is the output voltage V. U7 and reference voltage v
Comparator to compare with 3, 6 is reference voltage■.

This is a reference voltage generator that generates

As described above, photosensors can easily detect the presence or absence of the detected object 4, so they are often used in various devices as described above. Erroneous detection may occur, that is, the sensor may act as if the detected object 4 exists even though the detected object 4 does not exist.

This is because when the light emitting element 1 or the light receiving element 3 is contaminated, the amount of light emitted or the amount of light received decreases, and the detected object 4 decreases accordingly.
When there is no output current IL decreases, and the output voltage v0
This is because υ rises as shown by D in the figure and sometimes exceeds the reference voltage V.

Note that in the circuit configuration shown in FIG. 2, the output voltage V of the photosensor. As shown in FIG. 3, L17 is low when light is received and high when light is blocked, but this is just an example, and depending on the circuit configuration, this relationship can be reversed.

[Problem that the invention seeks to solve]

As described above, erroneous detection by the photosensor occurs when the light emitting element 1 or the light receiving element 3 becomes contaminated.

Conventionally, there was no means to check for this contamination, and therefore, the only way to prevent malfunctions due to contamination was to perform periodic cleaning, that is, periodic inspection. However, such inspection is generally performed regardless of the presence or absence of contamination, and therefore, in an apparatus in which a large number of photosensors are used, there is a drawback that a large number of man-hours are required.

An object of the present invention is to provide a photosensor that can check the state of contamination, in order to reduce the large number of man-hours required for periodic inspection of photosensors, and to prevent erroneous detection or failure of photosensors due to contamination. be.

[Means for solving problems]

In order to achieve the above object, the present invention provides a means for varying the drive voltage of the light emitting element of the photosensor, and this drive voltage variable means lowers the drive voltage of the light emitting element to reduce the amount of light emitted and The difference between the output voltage vouT when no object is present and the reference voltage V can be made smaller than usual.

[For production]

When the driving voltage of the light emitting element is lowered, the amount of light emitted decreases, and therefore the amount of light received by the light receiving element decreases, so the output current I. U.T.
decreases. Therefore, the output voltage V when there is no detected object. , JT and reference voltage V.

The difference between When contamination of the light emitting element or light receiving element is added to this, the output voltage becomes ■. LIT easily exceeds the reference voltage V. Therefore, by comparing the output voltage when the drive voltage is lowered with the reference voltage, contamination can be detected before malfunctions due to contamination occur.

〔Example〕

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, and the same parts as in FIG. 2 are given the same reference numerals. Further, reference numeral 7 denotes drive voltage lowering means, which is composed of a resistor R and a switch SW connected in parallel to the resistor R, and is connected in series between the photodiode 1 and a power source (not shown).

The switch SW is in a closed state under normal operating conditions,
Both ends of resistor R are shorted. Therefore, the resistor R has no involvement in the operation of the photosensor.

FIG. 2 is a diagram showing the detection characteristics of this embodiment.

Sections B and C are the same as in FIG.
Output voltage when there is no detection object, when the light is completely blocked by the detected object, and when the light is partially blocked
. It is LIT.

This output voltage V. If the photosensor is soiled, the A part of the UT rises and moves to the position of the F part in the figure, for example.

At this level of contamination, there is a sufficient difference from the reference voltage V, so
No false positives occur. However, as the contamination progresses and the difference vd between the A section and the F section increases, and the value of the voltage at the A section plus v4, that is, the voltage at the F section exceeds the reference voltage V, false detection may occur. becomes.

Next, a description will be given of an operation for checking contamination of the photosensor in this embodiment.

When checking the photosensor for contamination, the switch SW is opened and a resistor R is inserted between the photodiode 1 and the power source. As a result, the driving voltage of the photodiode 1 is reduced by the voltage effect at the resistor R. Therefore, the output voltage V when the amount of light 2 emitted from the photodiode 1 is reduced and the object to be detected 4 is not present. UT rises from part A to part G, and the difference from the reference voltage vs is V.

If the photosensor becomes contaminated as described above, ■4
If V is larger than V, the output voltage moves from the G section to the H section, which is higher by v4, and exceeds the reference voltage . Therefore, even though the detected object 4 does not actually exist, it operates as if the detected object 4 exists, resulting in false detection. Slight contamination is V, is V
, no false positives occur.

In other words, (1) above corresponds to the allowable value for contamination, and V can be set arbitrarily by selecting the value of the resistor R. As described above, in this embodiment, by opening the switch SW, the contamination of the photosensor You can easily check your progress.

Note that the drive voltage variable means 7 in the present invention is not limited to the configuration of the above embodiment. For example, it may be possible to provide two types of power supplies, one with regular voltage and one with low voltage, and switch between them.
It can be implemented with various modifications.

〔Effect of the invention〕

As described above, according to the present invention, the progress of staining of the photosensor can be easily checked at any time, so the number of steps required to prevent staining can be reduced, and the occurrence of failures due to staining of the device can be prevented.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the above embodiment, Fig. 3 is an explanatory diagram of the configuration of a conventional photosensor, and Fig. 4 is a problem with the conventional photosensor. FIG. 3 is a detection characteristic diagram of a photosensor for explaining the point. In the figure, 1 is a light emitting element, 2 is an emitted light, 3 is a light receiving element, 7 is a drive voltage variable means, 3 is a reference voltage/T, Invention - Amorphous Example Fan Sheet Light Concave Fig. 1 S → Output 77 Pawn Vout

Claims (1)

[Scope of Claims] A light emitting element (1), a light receiving element (3) arranged opposite to the light emitting element so as to receive the emitted light (2) of the light emitting element and generating an output corresponding to the amount of received light; The output of the light receiving element is compared with a preset reference value (V_3), and based on the comparison result, the detected object (
4), in which the light emitting element (1) is provided with drive voltage reducing means (7) for the light emitting element (1).
) is provided, and the driving voltage reducing means (7) is operated in a state where the object to be detected (4) is not present between the light emitting element (1) and the light receiving element (3), and the output of the light receiving element (3) is A method for detecting contamination of a photosensor, characterized in that it is configured to be able to determine whether or not the photosensor is contaminated based on a comparison result with the reference value (V_S).