JPH0640619B2 - Optical sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical sensor for detecting the presence or absence of an object with a pair of a light emitting element and a light receiving element, and in particular, the present invention relates to a dedicated amplifier for control. The present invention relates to an optical sensor with a built-in amplifier and an amplifier.

<Summary of the Invention> The present invention makes it possible to use one dedicated amplifier IC for both the transmission method and the reflection method by switching the sensitivity of the light emitting element, and also to reduce the size of the product and reduce the cost. To be realized at the same time.

<Background of the Invention> Conventionally, as shown in FIG. 2 and FIG. 3, the optical sensor of the related art has a pair of a light emitting element 1 and a light receiving element 2 and a dedicated amplifier IC 21 for control integrated in one case 20. The light emitting element 1 and the light receiving element 2 are formed by being incorporated into
In the transmissive method shown in FIG. 2, they are opposed to each other with a groove 22 therebetween, and in the reflective method shown in FIG. 3, they are arranged in parallel in the same direction. In the figure, 23 is a detected object.

Generally, in the case of the transmissive method, the light emitting element 1 and the light receiving element 2 are opposed to each other with a short distance (about several millimeters) therebetween, and therefore, higher detection sensitivity than that of the reflective method is not required. Therefore, in the transmission method, in order to prevent the consumption current from unnecessarily increasing, it is necessary to lower the light emitting / receiving efficiency and lower the detection sensitivity as compared with the reflection method.

For the above reason, when it is necessary to change the detection sensitivity between the transmission method and the reflection method, in the conventional optical sensor,
According to the detection method, a separate dedicated amplifier IC is provided for each, or a dedicated amplifier IC is provided with a separate circuit for both systems. However, any of the methods causes a high cost of the product, and particularly in the case of the latter method, there is a problem that the dedicated amplifier IC becomes large and hinders downsizing of the product.

<Object of the Invention> The present invention is for solving the above problems,
It is an object of the present invention to provide an optical sensor in which a dedicated amplifier IC can be used for both the transmission method and the reflection method, and at the same time, cost reduction and downsizing can be realized.

<Structure and Effect of the Invention> The present invention is an optical sensor having a light emitting element, a light receiving element, and a sensitivity switching circuit section, wherein the sensitivity switching circuit section changes the light emission amount of the light emitting element greatly. The first state in which the sensitivity of the light receiving element is changed to a higher one, and the second state in which the sensitivity of the light receiving element is changed to a lower one when the light emission amount of the light emitting element is changed to a small state. It is provided with means for setting.

According to the present invention, since the sensitivity switching circuit section that switches the sensitivity of the light receiving element to high or low in accordance with the change in the light emission amount of the light emitting element is provided, one dedicated amplifier IC can be used as a transmission type or a reflection type. Can be shared. Also, the sensitivity switching circuit section can be configured with a relatively simple circuit,
There is no fear that the dedicated amplifier IC will become large, and the product can be made compact and the cost can be reduced. Furthermore, when the light emission amount of the light emitting element is changed to a large amount, the sensitivity of the light receiving element is changed to a higher direction, and when the light emission amount of the light emitting element is changed to a smaller amount, the sensitivity of the light receiving element is changed to a lower one. There is an effect that the detection operation is stable because it is hardly affected by ambient light.

<Description of Embodiments> FIG. 1 shows a circuit configuration example of an optical sensor with a built-in amplifier according to the present invention.

The illustrated optical sensor is formed by integrally incorporating a pair of light emitting element 1 and light receiving element 2 and a dedicated amplifier IC3 for control in one case (not shown). Thus, the light emitting element 1 and the light receiving element 2 face each other or are installed in parallel (see FIGS. 2 and 3). In the case of the illustrated example, the light emitting element 1 is a light emitting diode and constantly emits light, while the light receiving element 2 is a phototransistor, and a current flows when light from the light emitting element 1 is received.

The dedicated amplifier IC3 has an amplifier circuit 4 and a sensitivity switching circuit section 5 built-in, and a power supply terminal Vcc,
Output terminal OUT, ground terminal GND, sensitivity switching terminal A,
B etc. are pulled out. The sensitivity switching circuit section 5 includes the light emitting element 1
And the transistors Q ₁ and Q ₂ which function to switch the current value flowing to the light emitting element 1 by changing the value of the current flowing to the light receiving element 2 to switch the detection sensitivity according to the detection method. The diode D ₁ which functions to switch the value of the current flowing through the element 2 is included. Of the sensitivity switching terminals A and B, one terminal A is for switching the current value of the light emitting element 1, and the other terminal B is for switching the current value of the light receiving element 2. Are either open or grounded depending on the detection scheme applied.

In the figure, 6 to 12 represent current sources, current sources 6 and 7 to the light emitting element 1, current sources 8 and 9 to the light receiving element 2, and current source 1
0 and 11 supply drive currents to the transistors Q ₁ and Q ₂ , and the current source 12 supplies drive current to the amplifier circuit section 4.

If both sensitivity switching terminals A and B are opened,
The base potential of the transistor Q ₁ rises and turns on, and the base potential of the transistor Q ₂ falls and turns off. Therefore, the light emitting element ₁ is supplied with the current I ₁ only by the current source 6. The diode is _{D 1,} conductive given the current _{I 3} by the current source 8, the current sum of the current _{I 4} due to _{I 3} and the current source 9 _(I 3 + I
₄ ) will be supplied to the light receiving element 2. Therefore, in this case, the current flowing through the light emitting element 1 is small and the light receiving element 2
Since the current flowing through is large, the detection sensitivity is low and it is applied to the transmission method.

Next, when the sensitivity switching terminals A and B are both grounded, the transistor Q ₁ is turned off without being supplied with the base current, while the transistor Q ₂ is turned on because the base potential rises. , The total current (I ₁ + I ₂ ) is supplied by the current sources 6 and 7. Further, the current I ₃ from the current source 8 directly flows to the ground, and the diode D ₁
Does not conduct, and the current I ₄ generated only by the current source 9 is applied to the light receiving element 2
Will be supplied to. Therefore, in this case, since the current flowing through the light emitting element 1 is large and the current flowing through the light receiving element 2 is small, the detection sensitivity is high and the method is applied to the reflection method.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a circuit configuration example of an optical sensor according to the present invention, and FIGS. 2 and 3 are explanatory diagrams for explaining a structural example of the optical sensor. 1 ... Light emitting element, 2 ... Light receiving element 3 ... Dedicated amplifier IC 5 ... Sensitivity switching circuit section A, B ... Sensitivity switching terminal

Claims (3)

[Claims] 1. An optical sensor having a light emitting element, a light receiving element, and a sensitivity switching circuit section, wherein the sensitivity switching circuit section detects the sensitivity of the light receiving element when the amount of light emitted from the light emitting element is significantly changed. A means for setting either of the first state for changing to a higher direction and the second state for changing the sensitivity of the light receiving element to a lower side when the light emission amount of the light emitting element is changed to a small state is provided. Optical sensor consisting of. 2. The sensitivity switching circuit section increases the current flowing through the light emitting element when the light emitting amount of the light emitting element is changed to a large amount, and the light emitting element is changed when the light emitting amount of the light emitting element is changed to a small amount. The optical sensor according to claim 1, wherein a current flowing through the sensor is reduced. 3. The sensitivity switching circuit section reduces a current flowing through the light receiving element when the sensitivity of the light receiving element is changed to a higher side, and the light receiving element is changed when the sensitivity of the light receiving element is changed to a lower side. The optical sensor according to claim 1, wherein a current flowing through the sensor is increased.