JPH02284085A - Photoelectric type object detector - Google Patents

Abstract

PURPOSE:To identify the presence or absence of the intrusion of an object by detecting the intensity of the reflected light from a monitoring section intermittently at prescribed sampling intervals and successively and relatively comparing the data on the intensities of a pair of the reflected light rays. CONSTITUTION:A photodetector 7 successively detects the modulating intermittent reflected light rays reflected from a background surface or object surface and intermittently outputs the modulating detection currents having the amplitudes corresponding to the light intensities thereof. An amplifier section 10 detects and amplifies the modulating detection currents and outputs an AD detection signal AC. A smoothing section rectifies and smoothes this signal and outputs a DC detection signal DC. A converting section 12 converts the crest components of the signal DC successively to the corresponding sampling data DATA in synchronization with the sampling signal CTL outputted by a control arithmetic section 14. A memory section 13 alternately records the data DATA and updates the recording data at every inputting. The arithmetic section 14 reads out the updated data DATA recorded in a pair of memory regions M 1, M 2 and computes the relative ratio. The signal indicating the intrusion of the object is outputted when the relative ratio exceeds the set threshold.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photoelectric reflective object detection device comprising a combination of a light emitting element and a light receiving element that detects light reflected from an object and generates an electric signal. More specifically, the present invention relates to a device that detects entry of an object into a monitoring area by relatively comparing the intensity of reflected light from an object surface and the intensity of reflected light from a background surface.

[Conventional technology]

2. Description of the Related Art Conventionally, a photoelectric reflective object detection device is known that detects an object by inputting light into a predetermined monitoring area and comparing the intensity of the light reflected from an object surface that has entered the area with a predetermined reference value.

[Problems to be solved by the invention]

However, in conventional detection devices, since the presence or absence of an object is detected and determined using an absolute reference value, erroneous detection often occurs due to various fluctuation factors, which poses a problem. Variation factors include a drift in emission intensity, variations in object surface reflectance, changes in the sensitivity of the light receiving element, and the influence of the background surface.

In particular, in the case of general-purpose photoelectric reflective detection devices that are installed in various locations, the reflectance and distance of the background surface differ, so the absolute reference value is the intensity of reflected light from the object surface and the reflection from the background surface. There were cases where the light intensity could not be determined, which was a problem.

[Means for solving problems]

The present invention aims to solve the problems of the prior art described above. To this end, the photoelectric object detection device according to the present invention includes a light emitting section that intermittently emits light in response to sampling signals input at predetermined intervals, and a light emitting section that emits light intermittently across the monitoring area of the object. It has an optical system for making the light incident on the surface, and a light receiving section that receives the intermittent reflected light reflected by the background surface or the object surface that has entered the monitoring area and sequentially generates sampling data according to the intensity of the intermittent reflected light. ing.

Furthermore, this photoelectric object detection device has a sampling data calculation processing unit, that is, an output unit, and sequentially calculates the relative ratio of a pair of temporally adjacent sampling data, and when the relative ratio exceeds a set threshold, for example, 1±α. An output signal indicating the entry of an object is output to the outside.

[For production]

According to the present invention, normally intermittent incident light is reflected by the background surface, and intermittent reflected light corresponding to the background surface reflectance is received and detected.

When an object enters the monitoring area at the begging timing, the intermittent incident light immediately thereafter is reflected by the object surface, and reflected intermittent light corresponding to the object surface reflectance is received and detected. The relative intensity ratio of the pair of intermittent reflected lights immediately before and after the timing deviates from the value 1±α by an amount β due to the difference in reflectance, thereby identifying the presence or absence of an object.

〔Example〕

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1A is a conceptual diagram showing the overall configuration of a photoelectric reflective object detection device according to the present invention, and shows a normal state in which an object exists outside the monitoring area.

As shown in the figure, the object detection device includes a case 1 containing a light emitting section, an optical system, a light receiving section, and an arithmetic processing section.

The light emitting section includes a light emitting element 2 made of a light emitting diode or the like.

The optical system includes a lens 4 that converts the emitted light into a beam or parallel light and makes it incident on the background surface 3 that exists behind the monitoring area, and a lens 4 that is inserted between the lens 4 and the light emitting element 2 to input the reflected light that returns from the monitoring area. A beam splitter for separating light, for example, consists of a semi-transparent mirror 5. Note that in this normal state, the object 6, that is, the object to be inspected, is outside the monitoring area. The light receiving section is a light receiving element 7 composed of a phototransistor etc. for detecting the reflected light separated from the semi-transparent mirror 5.
Contains.

Figure 1B shows the same photoelectric reflective object detection device.
This shows a state in which the object 6 to be inspected has entered the monitoring area as indicated by the arrow. Since the incident light from the light emitting element 2 is blocked by the object 6 that has entered, the incident light is reflected by the surface of the object 6. The reflected light follows the same optical path as shown in FIG. 1A and is converged on the light receiving element 7.

FIG. 2 is a block diagram showing the overall circuit configuration of the photoelectric reflective object detection device according to the present invention. First, the light emitting section intermittently oscillates in response to a control signal, that is, a sampling signal CTL input at predetermined intervals, and generates a nine-frequency superimposed sampling signal O3 having a desired set frequency component.
It has an oscillation section 8 that outputs C. Furthermore, it includes a drive section 9 that supplies an intermittent modulated drive current to the light emitting element 2, which is frequency-modulated in accordance with the high frequency FF1 sampling signal. The light emitting element 2 is driven by a modulated drive current and emits frequency modulated light intermittently in accordance with a sampling signal.

The light receiving section includes a light receiving element 7 that sequentially receives modulated intermittent reflected light reflected from a background surface or an object surface and intermittently outputs a modulated detection current having an amplitude corresponding to the light intensity. An amplifier section io is connected to the light receiving element 7-, which detects and amplifies the modulated detection current and intermittently outputs an alternating current detection signal AC. The amplifying section 10 includes, for example, a narrow band filter circuit that filters a set frequency component and an AC amplifying circuit.

For example, the smoothing section 11 composed of an integrating circuit etc. is connected to the amplifier section I.
0, rectifies and smoothes the AC detection signal AC, and intermittently outputs a DC detection signal DC having a corresponding peak value. A conversion unit 12 made of an A/D converter is connected to the smoothing unit 11, and sequentially converts the wave height component of the DC detection signal DC into corresponding sampling data DATA in synchronization with the sampling signal CTL. Therefore, each sampling data DATA is data indicating the intensity of reflected light that is intermittently received.

Finally, the output section is composed of a memory section 13 and a control calculation section 14. The memory section 13 has at least two registers or memory areas M1 and M2, records the sampling data supplied from the conversion section 12 alternately, and updates the recorded data every time new sampling data is input. The control calculation unit 14 is composed of, for example, a CPU, and in addition to outputting the above-mentioned sampling signal CTL, it sequentially accesses the memory unit 13 using the address signal ADS and reads updated sampling data recorded in a pair of memory areas M1 and M2. , calculates the relative ratio of a pair of sampling data. Based on the calculation results, the whiteness of the object entering the monitoring area is determined.
An output signal OUT representing nothing is output to the outside.

Next, the operation of the photoelectric object detection device according to the present invention will be explained based on the timing chart of FIG. First, the control calculation unit 14 generates a sampling signal CTL at predetermined intervals. The sampling signal CTL includes clock pulses arranged in chronological order, and the sampling timing SL is sequentially arranged.
, S2°S3. S4... is defined. Oscillation section 8
oscillates for a time corresponding to the pulse width of the tarok pulse in synchronization with these sampling timings, and outputs a sampling signal O8C on which a high frequency is superimposed. Next, the drive section 9 supplies a frequency-modulated drive current to the light emitting element 2 at a predetermined sampling timing according to the high frequency superimposed sampling signal O3C. The light emitting element 2 emits frequency-modulated light at sampling timing S1. S2. S3
This occurs in the following order.

The light receiving element 7 sequentially receives the modulated reflected light at the above-mentioned timing, and intermittently outputs a modulation detection current having an amplitude corresponding to the intensity of the reflected light. An AC amplification unit IO detects and amplifies the modulation detection current and outputs an AC detection signal AC.

This detection removes noise components included in the modulated detection current, improving detection accuracy.

Assume now that the object 6 enters the monitoring area at time T between sampling timings S3 and 84, as shown in FIG. Then, before the approach time T, the AC detection signal AC has a small amplitude according to the reflection intensity of the background surface at each sampling timing Sl, S2, and S3, whereas at the sampling timing S4 immediately after the approach time, the AC detection signal AC has a small amplitude according to the reflection intensity of the background surface. The detection signal AC has a large amplitude depending on the reflection intensity of the object surface.

Next, the smoothing section 11 smoothes the AC detection signal AC and converts it into a DC detection signal DC having a peak value corresponding to the amplitude value. The converter 12 digitizes the analog DC detection signal DC at predetermined timings Sl, S2, S3, etc. in synchronization with the sampling signal CTL, and sequentially outputs sampling data DATA corresponding to each peak value. .

Finally, the sampling data DATA is alternately recorded in a pair of memory areas M1 and M2 of the memory section 13 and updated with the latest data. For example, data generated at timing S1 is written to area M1, and data generated at timing S2 is written to area Pwx2. Next, the data generated at timing S3 is written here after erasing the recorded data in area M1, and the data generated at timing S4 is written here after erasing the recorded data in area M2. The control calculation unit 14 addresses a pair of memory areas M1 and M2 at predetermined intervals and reads a pair of updated data. A relative ratio between the two is calculated. Before the object entry time T, there is no change in the reflected light intensity, so the relative ratio is equal to the value 1. However, when comparing the sampling data generated at timing S3 immediately before the 8.7 point of object entry and the sampling data generated at timing S4 immediately after, there is a change in the reflected light intensity, so the relative ratio of the two is within the predetermined setting threshold range. Exceeds 1 Sat α. Note that α is an amount indicating a detection tolerance. Therefore, depending on this change, the output signal OU
T is switched from a low level to a high level as shown, and the fact of object entry is detected.

As described above, in the present invention, changes in received and reflected light intensity are monitored as the object moves toward the object. Therefore, if the incoming movement of an object cannot be erroneously compared due to error fluctuations, there is a possibility that the presence of the object cannot be identified because there will be no change in the reflected light intensity after the incoming object comes to rest in the monitoring area. There is also. For this reason, in this embodiment, the latest sampling data is read at regular intervals considerably longer than the sampling interval of the control calculation unit 14, and compared with a previously set absolute reference value, the difference between the two exceeds the reference value. When this happens, an output signal is generated indicating the fact that the object has already entered the monitoring area and is stationary.

FIG. 4 is a sectional view showing another embodiment of the photoelectric reflective object detection device according to the present invention. A pair of light emitting elements 2 arranged at a predetermined interval are embedded in the resin substrate 15. Further, a light receiving element 7 is embedded between the pair of light emitting elements 2. A circuit board 16 on which a circuit part of the detection device is mounted is fixed to the back side of the board 15.

A strong refractive optical member I7 is attached to the light emitting surface of each light emitting element 2 to emit light in a divergent manner, and as shown in the figure, the diverging light is incident on the background surface 3 at a wide angle, and the object monitoring area is Irradiates the entire area. A part of the reflected light is received by the light receiving element 7 disposed at the center, and a change in the intensity of the reflected light as it enters the object is detected. Although this embodiment has the advantage of being able to monitor the entire area, its detection accuracy is inferior to the embodiments shown in FIGS. 1A and 1B. On the other hand, in the embodiment shown in FIGS. 1A and 1B, since convergent incident light is used, only the central part of the monitoring area can be irradiated, but the sensitivity is high.

Figure 5 shows the photoelectric object detection device shown in Figure 4.
FIG. 2 is a perspective view showing an example of use in which the OS system is incorporated into an end-unread device. Portable end unread device 1
8 is different from the installation type, and can be arbitrarily placed on a desired product counter 19. The reading device 18 includes an optical code reading element 20 for reading codes attached to products placed in the monitoring area, and a semiconductor laser is generally used as the light source. To extend the life of the semiconductor laser, the semiconductor laser is activated only when an object enters the system. In order to control the operation of this laser, a photoelectric object detection device 21 shown in FIG. 4 is incorporated into the reading device 18. The object detection device 21 illuminates the entire monitoring area on the product counter 19 and detects the entry of objects, i.e. products, with high precision without being affected by the magnitude of the absolute reflectance of the surface of the product counter 19, that is, the background surface. can be detected.

〔Effect of the invention〕

As described above, according to the present invention, the intensity of reflected light from a monitoring area is detected intermittently at predetermined sampling intervals, and by sequentially comparing a pair of reflected light intensity data, it is possible to identify whether or not an object has entered. Therefore, there is an effect that highly accurate object detection is possible regardless of various fluctuation factors such as emitted light intensity and light receiving sensitivity.

In addition, since it is possible to detect the movement of an object regardless of the absolute reflectance of the object surface or background surface, any object can be identified.
Also, since it can be set at any location, it has the effect of being extremely versatile.

Furthermore, the use of divergent incident light has the effect of irradiating a wide range of monitoring areas.

[Brief explanation of drawings]

FIG. 1A is a conceptual diagram showing the overall configuration of a photoelectric object detection device according to the present invention, and shows a state in which an object is outside the monitoring area. Similarly, m1 diagram B shows a state in which an object is within the monitoring area. FIG. 2 is a block diagram showing the overall circuit configuration of the photoelectric object detection device according to the present invention. FIG. 3 is a timing chart for explaining the operation of the circuit shown in FIG. 2. FIG. 4 is a sectional view showing another embodiment of the photoelectric object detection device according to the present invention. FIG. 5 is a perspective view showing an application example in which the photoelectric object detection device shown in FIG. 4 is incorporated into a portapull type PO8 end non-reading device. DESCRIPTION OF SYMBOLS 1... Case, 3... Background surface, 5... Semi-transparent mirror, 7... Light receiving element, 9... Drive part, 11... Smooth part, 13... Memory part, 15 ...Resin substrate, ■7...Light-diffusion member. 2... Light emitting element, 4... Lens, 6... Object, 8... Oscillator, lO... Amplifying unit, 12... Conversion unit, 14... Control calculation unit, 16・・・Circuit board,

Claims (1)

[Claims] 1. A light emitting unit that intermittently emits light in response to sampling signals input at predetermined intervals; an optical section, a light receiving section that receives intermittent reflected light reflected by a background surface or an object surface that has entered the monitoring area, and sequentially generates sampling data according to the intensity of the intermittent reflected light; A photoelectric object detection device comprising an output section that sequentially calculates a relative ratio of sampling data and generates an output signal indicating the entry of an object when the relative ratio exceeds a set threshold. 2. The light emitting part includes a point light emitting element, the light receiving part includes a light receiving element, and the optical part includes a lens for making the light emitted from the point light emitting element incident on the background surface as a light beam spot, and a combination of the lens and the point light emitting element. 2. The photoelectric object detection device according to claim 1, comprising a semi-transparent mirror interposed between the light emitting elements and directing the returned reflected light toward the light receiving element. 3. The light emitting section includes at least a pair of spaced apart light emitting elements, the light receiving section includes a light receiving element disposed between the pair of light emitting elements, and the optical section converts the light emitted from the pair of light emitting elements into divergent light. 2. The photoelectric object detection device according to claim 1, further comprising a diverging member for making the light incident on the background surface. 4. The light emitting section includes an oscillating section that oscillates intermittently in response to a sampling signal, a driving section that generates a drive current modulated according to the oscillation frequency, and a light emitting element that emits modulated light by the modulated drive current. The light receiving section includes a light receiving element that receives modulated reflected light and outputs an alternating current in accordance with the received modulated reflected light, an amplifier section that detects and amplifies the alternating current, and smoothes the amplified alternating current and outputs a corresponding direct current. 2. The photoelectric object detection device according to claim 1, further comprising: a smoothing section that converts the DC current value into sampling data in response to a sampling signal; 5. The output section includes a memory section having a pair of registers that alternately stores sequentially input sampling data and updates them sequentially, and an arithmetic processing section that calls the pair of updated sampling data and calculates a relative ratio between the two. 1. The photoelectric object detection device according to 1. 6. Claim 1, wherein the output section compares the latest sampling data with a preset absolute reference value at regular intervals longer than the sampling interval, and when the difference between the two exceeds the reference value, generates an output signal indicating the intrusion of the object. The photoelectric object detection device described in .