JP2993705B2 - Optical detector - Google Patents

Description

The present invention relates to an optical detection device that optically detects the position of an object.

(B) Prior art FIG. 5 shows a conventional optical position detecting device, in which 11
Denotes a light emitting element array in which a plurality of light emitting elements 1 are arranged. A light receiving element array 12 is provided at a predetermined distance from the light emitting element array 11, and a light receiving element paired with the light emitting element 1 is provided therein. 2 are arranged. The microprocessor 3 includes a light emitting element driving circuit 4 and a multiplexer 5
Are sequentially scanned so that the light emitting element 1 and the light receiving element 2 # forming a pair can be operated. The received light amount obtained from the light receiving element 2 in the operable state via the multiplexer 5 is input to a comparator 7 via an amplifier 6 and compared with a reference level. Is output to the microprocessor 3 as presence / absence.

FIG. 6 is an explanatory view for explaining the operation of detecting the presence or absence of an object. In FIG. 6, the amount of light received by the light receiving element 2 is amplified via the amplifier 6 and sequentially output to the comparator 7. The input from the amplifier 6 is the reference level in the comparator 7.
The signal is compared with Vf, and outputs a low signal indicating no light blocking when the output is equal to or higher than the reference level, and outputs a high signal indicating light blocking (indicated by a broken line in FIG. 6) when the output is equal to or lower than the reference level. Thus, the presence / absence and position of the object can be optically detected.

(C) Problems to be solved by the invention The position (presence or absence) of an object in the optical position detection device
A light-blocking detection mode that outputs a position detection at the moment when the object shifts from a state in which the object does not block light (non-blocking state) to a state in which the object blocks light (blocking state);
There is a light-shielding end detection mode that outputs the final position at the moment when the light-shielded state is shifted to the light-shielded state. FIG. 7 shows a change in a signal input to the comparator 7 for each one scan of the light receiving element 2 in the process of blocking light by the object in the above-described detection mode at the time of light blocking. Input signal (A) ~
(F) decreases with the passage of time, and at the time (D) when the signal becomes lower than the reference level Vf, the comparator 7 detects the light shielding of the object and outputs the light shielding position.

However, when the light shielding of the object is not sufficient, that is, when the signal due to the light shielding of the object is near the reference level Vf, detection of the light shielding becomes unstable due to noise or vibration. Therefore, while the light shielding of the same object is continued, the presence or absence of the light shielding is repeatedly detected a plurality of times.
Even in the light-blocking end detection mode, there is a disadvantage that a large number of detection coordinates are output unnecessarily.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical detection device capable of reliably detecting a light-shielding position of an object only at the time of light-shielding or at the end of light-shielding.

(D) Means for Solving the Problems The present invention provides a plurality of pairs of a light emitting element and a light receiving element which are arranged apart from each other and an input of an amount of light received from one of the plurality of light receiving elements. Selecting means for leading to an analog / digital converter, an analog / digital converter for converting an analog signal of the received light amount into a digital signal,
While sequentially scanning the selecting means, receiving the digital signal from the analog / digital converter, storing the non-light-shielded reference level and the light-shielded reference level set higher than the non-light-shielded reference level, A microprocessor that switches so as to compare the digital signal with the non-light-shielding reference level when detecting a shift to light-shielding, and to compare the light-shielding reference level with the digital signal when detecting a shift from light-shielding to non-light-shielding of an object; including.

(E) Operation In the present invention, in the microprocessor, the digital signal representing the amount of received light is a non-light-shielding reference level which is at a low level when the object is shifted from non-light-shielded to light-shielded, By switching the reference level so as to be compared with a high-level light-shielding reference level to provide hysteresis, the position detection of an object at the time of light-shielding and at the time of non-light-shielding is ensured.

(F) Embodiment FIG. 1 shows a circuit configuration diagram for explaining an embodiment of the present invention, and the same parts as those in FIG. The microprocessor 3 monitors the output from the comparator 7, detects a change in the comparison output, and outputs a changeover signal to the changeover switch 8. Changeover switch 8-2
The two input terminals are connected to a light-shielding reference power supply 9 that supplies a light-shielding reference level Vfl to the comparator 7 and a non-light-shielding reference power supply 10 that supplies a non-light-shielding reference level Vfh. The switch 8 switches the output to the comparator 7 between the light-shielded reference power source 9 and the non-light-shielded reference power source 10 each time the switch signal is received. Note that the non-light-shielding reference level V is larger than the light-shielding reference level Vfl.
fh is set to a high voltage.

Next, an operation of detecting a light-shielding object in the apparatus having the above configuration will be described. When there is no shading of the object, the changeover switch 8 is connected to the side of the shading reference power supply 9, and a low shading reference level Vfl is given as a reference level of the comparator 7. At this time, if the object is shaded as shown in FIG. 2 (A) and the input of the scanned amount of received light to the comparator 7 is lower than the shading reference level, the output of the comparator 7 changes from low to high. Switch to The microprocessor 3 detects a change in the comparison output and outputs a changeover signal to the changeover switch 8. The changeover switch 8 switches the connection with the comparator 7 to the side of the non-light-shielded reference power supply 10, so that a high level non-light-shielded reference level Vfh is given to the comparator 7. As shown in FIG. 2 (B), when the object shifts from the light-shielded state to the non-light-shielded state for each scan, when the amount of light received by the comparator 7 exceeds the non-light-shielded reference level, Changes its output from high to low. The microprocessor 3 identifies a transition from light-shielded to non-light-shielded based on a change in the comparison output, and outputs a changeover signal to the changeover switch 8. The changeover switch 8 is a shading reference power source 9
The connection with the comparator 7 is switched to the side. Therefore, the light-blocking reference level Vfl is given to the comparator 7, and the light-blocking of the next object is detected as described above. As described above, the transition from the non-light-shielded state to the light-shielded state is detected by the low-level light-shielding reference level Vfl, and the transition from light-shielded to non-light-shielded is detected by the high-level non-light-shielded reference level Vfh. The detection at the end can be performed only once.

FIG. 3 shows only the main components related to FIG.
The other configuration is omitted because it is similar to the above-described case. In this configuration, instead of providing the changeover switch 8, the light-shielding reference power supply 9, and the non-light-shielding reference power supply 10, the microprocessor 3
The arithmetic and control circuit 3a provided in the digital / analog (D /
A) Use converter 3b and input port 3c. That is, the output from the comparator 7 is detected by the input port 3c as a 0/1 signal and supplied to the arithmetic and control circuit 3a, where the state of the signal change, that is, transition from light-shielded to non-light-shielded, or from non-light-shielded The transition to shading is identified. In the case of transition from light-shielded to non-light-shielded, a digital signal of the non-light-shielded reference level indicating the high level is output to the D / A converter 3b, where it is converted into an analog signal and given as a reference level of the comparator. Similarly, in the case of transition from non-light-shielded to light-shielded, the light-shielding reference level indicating the low level is given to the comparator 7 via the D / A converter 3b.

FIG. 4 shows an embodiment of the present invention, in which the function of the comparator 7 is substituted in the microprocessor 13. In the case of this embodiment, the amount of light received from the amplifier 6 is calculated by the A / D converter 14.
The received light amount is compared with a non-light-shielded reference level or a light-shielded reference level provided in the microprocessor 13, and the reference level is switched every time the reference level is exceeded. The same operation as the operation is performed.

(G) Effect In the present invention, the detection of the position of the object is made to have a hysteresis by lowering the reference level when shifting from non-shading to shading and increasing the reference level when shifting from shading to non-shading.
It is possible to reliably detect the object at the time of shading and at the end of shading without erroneous detection. Therefore, for example, erroneous detection caused by variation in the quality of a light emitting diode or a phototransistor element or deterioration in performance over time can be prevented, and the effect of disturbance light on detection accuracy can be minimized.

Further, since the present invention is configured to receive the amount of received light as a digital signal through an analog / digital converter and compare the light-shielded reference level or the non-light-shielded reference level stored in the microprocessor with the digital signal,
There is no need to provide a comparator separately, the configuration is extremely simple and miniaturization is possible, and the reference level can be easily changed and fine-tuned by changing the set value stored in the microprocessor. it can.

Further, since the microprocessor sequentially scans the selection means to select the input of the amount of light received from one of the plurality of light receiving elements and supplies the input to the analog / digital converter, once the reference level is switched, Until the next switching of the reference level, the switched reference level is sequentially compared with the digital signal indicating the amount of light received from each light receiving element, so that a plurality of pairs of light emitting elements and light receiving elements are used. In an optical position detecting device that performs position detection by scanning sequentially, not only can erroneous detection due to noise at the time of detection be prevented, but also variations in the quality of each light emitting element and light receiving element, changes over time, Since the erroneous detection that occurs for each element due to a change in light can be reliably reduced, the detection accuracy of a position detection device using a plurality of elements should be increased, and the life of element replacement should be increased. It can be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for explaining the present invention, FIG. 2 is a diagram for explaining the operation of the present invention, FIG. 3 is a diagram of another essential portion related to FIG. 1, and FIG. FIG. 5 is a schematic diagram showing an example of a conventional detection device of the present invention, FIG. 6 is a diagram illustrating a light-shielding detection operation of FIG. 5, and FIG. It is a figure explaining operation of time detection mode. 1 light-emitting element, 2 light-receiving element, 3, 13 microprocessor, 3a arithmetic circuit, 3b D / A converter, 3c
…… Input port, 14… A / D converter, 6 …… Amplifier, 7
...... Comparator, 8 ... Switch, 9 ... Shadow reference power supply, 10 ... Non-shade reference power supply.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroki Nagasaki 1-1-3 Higashicho, Kichijoji, Musashino-shi, Tokyo Musashino-ryo, Dowa Mining Co., Ltd. JP-A-61-102575 (JP, A) JP-A-50-90276 (JP, A) JP-A-60-179881 (JP, U) JP-B-54-21070 (JP, B2)

Claims (1)

(57) [Claims] 1. A plurality of pairs of a light emitting element and a light receiving element which are arranged apart from each other, and a selection of inputting an amount of light received from one of the plurality of light receiving elements and leading the input to an analog / digital converter. Means, an analog / digital converter for converting an input analog signal of the amount of received light into a digital signal, and sequentially scanning the selecting means,
When a digital signal is received from a digital converter, a non-light-shielded reference level and a light-shielded reference level set higher than the non-light-shielded reference level are stored, and the transition from non-light-shielded to light-shielded of the object is detected. A non-shading reference level, a microprocessor that switches so as to compare the shading reference level with the digital signal when detecting a transition from shading to non-shading of an object; An optical detection device that detects only at the end of shading.