JPH0453395B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention includes a light-emitting element and a light-receiving element, and projects pulse-modulated light from the light-emitting element so that the light is reflected on an object or transmitted through the object and enters the light-receiving element. It relates to a light modulation type detection device such as a so-called light modulation type photoelectric switch or a photointerrupter that detects the presence or absence of an object by detecting the presence or absence of incident light with the light emitting element, and is particularly effective against disturbance light noise. This invention relates to a light modulation type detection device that has a function to prevent malfunctions caused by. [Prior Art] The general configuration of a light modulation type detection device is as shown in FIG. That is, a light emitting element drive circuit 9 and a light emitting element 10 that emits pulsed light according to the pulsed wave are connected in sequence to the oscillation circuit 8 that generates the pulsed wave. In addition, the light receiving element 11 that receives the pulsed light and converts it photoelectrically includes the light receiving element 11.
AC amplifier 12 that amplifies the output and outputs the received light signal
and the first determination circuit 13 are sequentially connected. The oscillation circuit 8 and the first determination circuit 13 are connected to a synchronization detection circuit 14.
An integrating circuit 15, a second determination circuit 16, and an output circuit 17 are connected to. In such a conventional optical modulation type detection device, the synchronization detection circuit 14 consists of a D-flip-flop 14a shown in FIG. 5, and simply takes in data on light emission timing. Further, the integrating circuit 15 is
As shown in Figure 6, an external capacitor 15
It usually consists of a resistor 15b and a resistor 15b built into the IC. The light modulation type detection device having such a structure detects the presence or absence of pulsed light by simply performing synchronized detection using a sampling pulse synchronized with a pulse drive signal for pulse driving the light emitting element 10. Ta. Its operation is as follows. The pulse signal emitted from the oscillation circuit 8 is pulse-driven by the light emitting element drive circuit 9, and the pulse signal shown in FIG.
The signal is applied to the light emitting element 10 as a light emitting signal shown in FIG. As a result, pulse-modulated light is projected from the light emitting element 10. This pulsed light is reflected by the object 18 or transmitted through the object 18 and is incident on the light receiving element 11 . Therefore, the intensity of the pulsed light incident on the light receiving element 11 changes greatly depending on the presence or absence of the object 18, or the pulsed light is incident or blocked. At this time, if the device is of a transmission type, the pulsed light is blocked by the object 18 for a period shown in b of the figure. Here, when the disturbance light shown in the figure c is incident on the light receiving element 11, the light reception signal shown in the figure d appears on the output side of the AC amplifier 12. This light reception signal is waveform-shaped by the first determination circuit 13, and converted into a synchronization detection circuit output signal by the synchronization detection circuit 14 as shown in FIG. This signal passes through the integrating circuit 15 to become an integrated output signal shown in g in the same figure, is waveform-shaped again in the second determination circuit 16, and is output via the output circuit 17 as shown in h in the same figure. However, in the conventional structure described above, for example, in the case of a transmission type light modulation type detection device, the object 18 is interposed between the light emitting element 10 and the light receiving element 11, and the light emitted from the light emitting element 10 is transmitted to the light receiving element. In order to prevent malfunction when pulsed disturbance light noise from a fluorescent lamp, a remote control device, etc. is directly or indirectly incident on the light receiving element 11 during a period when the light is not incident on the light receiving element 11, an integrating circuit 15 with a long time constant is used. is required, which slows down the response speed of the circuit. Furthermore, since a large capacity capacitor is required,
It had drawbacks such as preventing miniaturization such as IC conversion. [Object of the Invention] The present invention has been made in consideration of the above-mentioned conventional problems, and is aimed at reducing disturbance light detected by the light receiving element, particularly fluorescent lamps and remote controllers, at a timing when the light emitting element is not emitting pulsed light. The object of the present invention is to provide an optical modulation type detection device that has excellent selection characteristics against periodic pulse noise of devices, etc., has a fast response speed, and can be miniaturized. [Structure of the Invention] The light modulation type detection device of the present invention has a function of detecting an object interposed in the optical path between the light emitting element and the light receiving element,
In an optical modulation type detection device including a synchronization detection circuit that performs synchronization detection of a light emission signal and a light reception signal, and an integration circuit that integrates an output of the synchronization detection circuit, the integration circuit integrates the output signal of the synchronization detection circuit. It consists of a digital integration circuit that detects coincidence of at least two or more consecutive output signals as input data, and the synchronization detection circuit includes means for detecting a light emission signal at a light emission timing and a non-light emission timing in synchronization with a light emission signal. , and receives the integral output from the above integration circuit, and in response to the detection of the light reception signal at the non-emission timing, if the light reception signal is not detected at the non-emission timing, the detection output of the light reception signal at the emission timing, and the light reception signal at the non-emission timing. and means for selecting the integral output of the integrating circuit as input data of the integrating circuit when detected, so that malfunctions due to ambient light noise can be prevented. . [Embodiment] An embodiment of the present invention will be described below based on FIGS. 1 to 4. The block diagram of the light modulation type detection device in this example is the same as the block diagram of the general light modulation type detection device shown in FIG. 4, and the same reference numerals are added to the overlapping parts. Therefore, the explanation will be omitted. As shown in FIG. 1, the synchronization detection circuit 14 shown in FIG.
and two D-flip-flops 1 and 2, AND gates 3a and 3b, and OR gates 3a and 3b for capturing and holding data at the light emission timing detection point B.
AND-OR gate 3 having a gate 3c, and a D-flip-flop 4 for holding the judgment result.
Consists of. AND gate 3 of AND-OR gate 3
b is connected to the terminal of D-flip-flop 1 that holds data at detection point A and the terminal of D-flip-flop 2 that holds data at detection point B, and to AND gate 3a is connected the terminal of D-flip-flop 1 that holds data at detection point A. The Q terminal and the output end of the digital integration circuit 15 are connected. That is, the integration circuit 15 is configured as shown in FIG. 2, and the AND gate 3
The output of this digital integration circuit 15 is fed back and input to one of the terminals a. AND gate 3 above
The output sides of a and 3b are connected to an OR gate 3c, and the output side of this OR gate 3c is connected to the D terminal of a D-flip-flop 4. This D
- The output of the flip-flop 4 is input to the integrating circuit 15 of FIG. The integrating circuit 15 also includes a three-stage shift register 5..., two AND gates 6a,
6b and RS latch 7. Note that the shift register 5 requires at least two stages in terms of function.
Each Q terminal of shift register 5... is AND gate 6
a, and each terminal is connected to AND gate 6
connected to b. Also, the above AND gate 6
The output sides of AND gate 6b are connected to the set input terminal and reset terminal of RS latch 7, respectively. The Q output terminal is connected to the second determination circuit 16 at the next stage. In the above configuration, the relationship between the determination output level at each detection point A, B in the synchronization detection circuit 14 and the output of the synchronization detection circuit is shown in Table 1 below. The operation will be explained below with reference to Table 1.

〔Effect of the invention〕

As described above, the light modulation type detection device of the present invention has the following features:
The synchronization detection circuit is provided with means for detecting the light reception signal at a plurality of timings in synchronization with the light emission signal, and selects the integral output from the integration circuit when the light reception signal is detected at a timing when the light emission signal is not emitted. In addition, the integrator circuit includes a digital integrator circuit that detects coincidence of output levels at least two consecutive times in the output of the synchronization detection circuit. This makes it possible to almost certainly prevent malfunctions due to the influence of ambient light. Furthermore, the number of times the output levels are matched can be set to a small number, thereby increasing the response speed of the circuit. Furthermore, by digitizing the integrating circuit, a large capacitor is no longer necessary, and it is possible to achieve effects such as miniaturization and integration into ICs.

[Brief explanation of the drawing]

Figures 1 to 3 show an embodiment of the present invention, in which Figure 1 is a circuit diagram of a synchronization detection circuit, Figure 2 is a circuit diagram of an integrating circuit, and Figure 3 is a light modulation type detection circuit. A time chart showing the output signals of each part of the device, FIG. 4 is a block diagram showing the basic configuration of the optical modulation type detection device, FIGS. 5 to 7 show conventional examples, and FIG. 5 shows the synchronous detection device. FIG. 6 is a circuit diagram of the detection circuit, FIG. 6 is a circuit diagram of the integrating circuit, and FIG. 7 is a time chart showing output signals of various parts in the optical modulation type detection device. 1, 2, 4 are D-flip-flops, 3 is
AND-OR gate, 5 is a shift register, 3a,
3b, 6a, and 6b are AND gates, 7 is an RS latch, 10 is a light emitting element, 11 is a light receiving element, 14 is a synchronization detection circuit, and 15 is an integrating circuit.

Claims (1)

[Scope of Claims] 1. A synchronization detection circuit that has a function of detecting an object interposed in the optical path between the light emitting element and the light receiving element and performs synchronization detection of the light emission signal and the light reception signal, and integrates the output of this synchronization detection circuit. an optical modulation type detection device comprising an integrating circuit, the integrating circuit comprising a digital integrating circuit that uses the output signal of the synchronization detection circuit as input data to detect coincidence of at least two consecutive output signals; The synchronization detection circuit includes a means for detecting a light emission signal at a light emission timing and a non-light emission timing in synchronization with a light emission signal, and receiving an integral output from the integration circuit, and in response to detection of a light reception signal at a non-light emission timing. When a light emission signal is not detected at non-emission timing, the detection output of the light reception signal at the emission timing,
A light modulation type detection device characterized by comprising means for selecting an integrated output of the integrating circuit as input data to the integrating circuit when a light emitting signal is detected at a non-light emitting timing.