JP2551344B2 - Photo sensor circuit for medium detection - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo sensor circuit for detecting a medium by combining a light emitting element and a light receiving element, and more particularly to a photo sensor circuit capable of automatically adjusting an output voltage level of the light receiving element.

[0002]

2. Description of the Related Art Conventionally, a printer or the like has been provided with a photo sensor circuit for detecting the presence or absence of the paper (medium). In this type of photo sensor circuit, a light beam emitted from a light emitting element is blocked or reflected by a medium, so that the amount of light received by the light receiving element fluctuates and the output voltage level becomes equal to or lower than a reference voltage value. That is, the presence or absence of the medium is detected.

In such a photo sensor circuit, when the sensitivity is adjusted, the amount of light emitted is adjusted by adjusting the current flowing through the light emitting element, or the gain of the amplifier for amplifying the output voltage obtained from the light receiving element. It was a general method to adjust the value by a variable resistance.

[0004]

The above-mentioned conventional photosensor circuit for detecting a medium has a drawback that it requires a lot of labor and time for the adjustment because it requires a manual operation for adjusting the sensitivity. It was Further, if the amount of light emitted from the light emitting element or the light receiving sensitivity of the light receiving element decreases due to dust or the like adhering to the light emitting element or the light receiving element, medium detection may become impossible. As described above, in the manual adjustment work, there is a problem that it is not possible to follow the decrease in sensitivity due to the adhesion of dust or the like.

The present invention has been made in order to solve such a conventional problem. By automatically adjusting the sensitivity, it is not necessary to manually adjust the sensitivity, and dust, dust, etc. are eliminated. An object of the present invention is to provide a medium detection photosensor that can be adjusted in accordance with a decrease in sensitivity due to adhesion.

[0006]

In order to achieve the above object, the present invention detects a medium in a medium detecting photosensor circuit which optically detects the medium by combining a light emitting element and a light receiving element. A reference voltage setting means for selectively outputting a detection reference voltage or an adjustment reference voltage composed of an upper limit voltage and a lower limit voltage having a larger value than the detection reference voltage by a switching signal, and an output voltage level of the light receiving element. Comparison means for comparing the detection reference voltage or the adjustment reference voltage output from the reference voltage setting means, and the switching signal to the reference voltage setting means, and the output of the light receiving element by the comparison means The presence or absence of the medium is determined based on the result of comparison between the voltage level and the detection reference voltage, and the output voltage level and the adjustment reference voltage A CPU that generates light emission amount data of the light emitting element based on a comparison result, a light emitting element driving unit that causes the light emitting element to emit light based on the light emission amount data output from the CPU, and the light emission generated by the CPU. And a memory for storing quantity data so that the CPU can refer to the quantity of light emission data so that the output voltage level of the light receiving element falls within a range of an upper limit voltage and a lower limit voltage of the adjustment reference voltage. Is adjusted.

[0007]

In the present invention, the CPU turns on the light emitting element with a light amount proportional to a certain light amount data. The light beam emitted from the light emitting element is received by the light receiving element, and the output voltage corresponding to the amount of light received is output from the light receiving element to the comparison means. The comparison means compares the output voltage with the adjustment reference voltage and outputs the comparison result to the CPU. The CPU determines from the comparison result whether the output voltage is higher than the adjustment reference voltage. If it is smaller than the adjustment reference voltage, the value of the light emission amount data is varied, and the adjustment processing is repeated until the output voltage becomes larger than the adjustment reference voltage.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a medium detecting photosensor circuit according to an embodiment of the present invention.
In FIG. 1, the medium detection photosensor circuit of this embodiment includes a light emitting element 11 formed of a photodiode, a light receiving element 12 formed of a phototransistor, a D / A converter 13, a voltage-current conversion circuit 14, a detection resistor 15, Voltage amplifier 16, voltage comparator 17, reference voltage setting circuit 18, C
It is composed of a PU 19 and a memory 20.

The D / A converter 13 uses the light emission amount data b written by the CPU 19 to generate the light emitting element 1
A light emission control voltage c for causing 1 to emit light is supplied. The voltage-current conversion circuit 14 converts the light emission control voltage c supplied from the D / A converter 13 into a current and supplies the current to the light emitting element 11.

The voltage amplifier 16 amplifies the voltage output from the light receiving element 12 and outputs it as an output voltage (Vr). The voltage comparator 17 includes the light receiving element 12 to the voltage amplifier 1
The output voltage (Vr) output via 6 is compared with the detection reference voltage (Vref) or the adjustment reference voltage (Va1, Va2) output from the reference voltage setting circuit 18, and the comparison result is sent to the CPU 19. Output.

The reference voltage setting circuit 18 is a detection reference voltage (Vref) for detecting the medium or the light receiving element 12.
Adjustment reference voltage (Va1,
Va2) is selectively switched and output under the control of the CPU 19. Here, Va1 is the upper limit value of the adjustment reference voltage, and Va2 is the lower limit value of the adjustment reference voltage. Va1>Va2> Vre with respect to the detection reference voltage Vref
It is set so that the relationship of f is established.

The CPU 19 outputs the output voltage (Vr) of the light receiving element 12 from the voltage comparator 17 and the detection reference voltage (Vre).
The presence / absence of the medium is determined based on the comparison result with f), and the output voltage level and the adjustment reference voltage (Va1, Va) are determined.
The light emission amount data b of the light emitting element 11 is generated based on the comparison result with 2). The memory 20 stores the light emission amount data b generated by the CPU 19.

The operation at the time of medium detection will be described. The D / A converter 13 outputs a light emission control voltage c based on the light emission amount data b written by the CPU 19, and the light emission control voltage c is output from the voltage-current conversion circuit 14. Is converted into a current and the light emitting element 11 is turned on with a light amount proportional to the light emission data b. The light beam emitted from the light emitting element 11 is received by the light receiving element 12, a voltage corresponding to the amount of light received is output from the light receiving element 12, and this voltage is output to the voltage comparator 17 as the output voltage Vr via the voltage amplifier 16. To be done.

In the voltage comparator 17, the output voltage Vr from the light receiving element 12 is compared with the detection reference voltage Vref output from the reference voltage setting circuit 18, and the comparison result is CP.
Output to U19. The CPU 19 determines the presence of the medium based on the comparison result from the voltage comparator 17. That is, in the case of the reflection type sensor, the medium is present when the output voltage Vr becomes equal to or higher than the detection reference voltage Vref due to an increase in the amount of light received by the light receiving element 12 due to the light rays reflected from the light emitting element 11 being reflected by the medium. Then, it is determined. Also,
In the case of a transmissive sensor, it is determined that the medium exists when the output voltage Vr becomes equal to or lower than the detection reference voltage Vref because the light beam from the light emitting element 11 is blocked by the medium and the amount of light received by the light receiving element 12 decreases. To be done.

Next, the operation of adjusting the sensitivity of the photo sensor circuit will be described with reference to the flowchart of FIG. 2 showing the processing contents of the CPU 19. At the time of adjustment, first CPU1
9 outputs the reference voltage switching signal a to the reference voltage control circuit 18 (step 201). As a result, in the reference voltage control circuit 18, the detection reference voltage Vref is switched to the adjustment reference voltages Va1 and Va2 (Va1>Va2> detection reference voltage Vref), and the adjustment reference voltages Va1 and V1.
a2 is input to the voltage comparator 17.

Further, the CPU 19 reads the light emission amount data b initially stored as a fixed value in the memory 20 or the light emission amount data b stored in the memory 20 at the time of the previous adjustment (step 202). Read light emission amount data b
Is written in the D / A converter 13 (203). As a result, the light emission control voltage c is output from the D / A converter 13, and the light emitting element 11 is output via the voltage-current conversion circuit 14.
Is turned on with a light amount proportional to the light emission amount data b.

The light beam emitted from the light emitting element 11 is received by the light receiving element 12, a voltage corresponding to the amount of light received is output from the light receiving element 12, and this voltage is output via the voltage amplifier 16 as an output voltage Vr to a voltage comparator. It is output to 17. The output voltage Vr obtained by the voltage amplifier 19 is the voltage comparator 1
Input to 3. In the voltage comparator 13, the output voltage Vr is compared with the adjustment reference voltages Va1 and Va2, and the comparison result is output to the CPU 19 as a sensor detection signal d.

The CPU 11 checks the sensor detection signal d and determines whether the relationship of Va1>Vr> Va2 is established (steps 204 and 205). Va1
If>Vr> Va2 is not satisfied, the value of the light emission amount data b is varied (step 206), Va1>Vr> V.
Until step a2 is established, the discard step 206 is started from step 203.
The adjustment process of is repeated. That is, in step 206, when Vr is larger than Va1, the light emission amount data b is set to be smaller than the previous value and generated, and when Vr is smaller than Va2, the light emission amount data b is set to be larger than the previous value and generated. To do.

At step 206, Va1>Vr> Va2
Is satisfied, the CPU 19 outputs the reference voltage switching signal a to the reference voltage setting circuit 18 to switch the adjustment reference voltages Va1 and Va2 to the detection reference voltage Vref (step 207), and at the same time, the CPU 19 generates the light emission amount. Write the data b to the memory 20 (step 20
7), the adjustment is completed. Although the present invention has been described with reference to the preferred embodiments, the present invention is not necessarily limited to the above embodiments.

[0020]

As described above, according to the medium detecting photosensor circuit of the present invention, a constant output voltage can be obtained based on the result of comparison between the output voltage level of the light receiving element and the adjustment reference voltage. By changing the light emission amount of the light emitting element like this, it is possible to automatically adjust the sensitivity, eliminating the need for manual labor and time-consuming adjustment work as before, and dust and dirt It is possible to make adjustments that follow the drop in output voltage that occurs. Further, since the light emitting element driving means stores the light emitting amount data for causing the light emitting element to emit light in the memory, and the CPU adjusts the light emitting amount data according to the comparison result of the comparing means, it is already used for control in the mechatronics device or the like. When the CPU is provided, the existing CPU for control and the memory such as ROM and RAM for storing programs and data are shared as the CPU for adjusting the light emission amount data and the memory for storing the light emission amount data. It is not always necessary to provide a dedicated CPU or memory for adjusting the light emission amount of the sensor. Further, since the light emission amount data held in the memory can be easily collected and transferred by the CPU, the maintainability of the device embodying the present invention is improved. Also,
The detection reference voltage is changed to the adjustment reference voltage only when the sensor is adjusted by the switching signal from the CPU, and the light emission amount is adjusted according to the comparison result by the comparison means based on the adjustment reference voltage. Only the comparison means is required, and it is not necessary to provide a dedicated comparison means for adjusting the light emission amount. Further, a range of adjustment reference voltage (upper limit voltage> lower limit voltage> detection reference voltage) consisting of an upper limit voltage and a lower limit voltage having a larger value than the detection reference voltage is set in advance as an adjustment target of the output voltage of the light receiving element. During the adjustment, the light emission amount data is adjusted so that the output voltage of the light receiving element falls within the range of the adjustment reference voltage. Therefore, in the transmissive photosensor, the effect of not requiring an adjustment medium is obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of a medium detection photosensor circuit of the present invention.

FIG. 2 is a flowchart illustrating the contents of adjustment processing by the CPU of the medium detection photosensor circuit according to the embodiment shown in FIG.

[Explanation of reference numerals] 11 light emitting element 12 light receiving element 13 D / A converter 14 voltage-current conversion circuit 17 voltage comparator 18 reference voltage setting circuit 19 CPU 20 memory

Continuation of front page (56) Reference JP-A-60-229527 (JP, A) JP-A-3-60517 (JP, A) JP-A-2-239720 (JP, A) JP-A-2-285713 (JP , A) JP 3-123119 (JP, A) JP 3-190419 (JP, A) JP 3-261219 (JP, A) JP 4-190497 (JP, A) 62-141223 (JP, U)

Claims (1)

(57) [Claims] 1. A medium detection photosensor circuit for optically detecting a medium by combining a light emitting element and a light receiving element, wherein a detection reference voltage for detecting the medium or a value higher than the detection reference voltage is used. Do not use large upper and lower voltage limits
Compares the reference voltage setting means and the detecting reference voltage or adjusting the reference voltage and the output voltage level output from the reference voltage setting unit of the light receiving element for selectively outputting the signal switching an adjustment reference voltage that And outputs the switching signal to the comparison means and the reference voltage setting means.
Then, the presence or absence of the medium is determined based on the comparison result between the output voltage level of the light receiving element and the detection reference voltage by the comparison means, and based on the comparison result between the output voltage level and the adjustment reference voltage. A CPU for generating light emission amount data of the light emitting element, a light emitting element driving means for causing the light emitting element to emit light based on the light emission amount data output from the CPU, and the light emission amount data generated by the CPU for the CPU
And a memory for storing so that the CPU can refer to the output voltage level of the light receiving element.
Make sure that it is within the upper and lower voltage limits of the adjustment reference voltage.
A photodetector circuit for detecting a medium , wherein the light emission amount data is adjusted .