JPS61218909A - Photoelectric object detecting device - Google Patents

Abstract

PURPOSE:To reduce an error of distance measurement by slanting the light receiving face of a light spot position detecting element not face the photodetecting lens of a condensing device rightly, and at the same time, providing a trapping device of light reflected by the light receiving face of the light spot position detecting element on the inner face of a housing. CONSTITUTION:The light receiving face of a semiconductor position detecting element 4 (PSD) belonging to PIN type photodiode is slanted not to face the light receiving lens of a condensing device 3, and at the same time, a trapping device 8 of light reflected by the photodetecting face of PSD 4 is provided on the inner face of a housing 7. Thus, light reflected by the light receiving face of PSD 4 does not enter the photodetecting lens of the condensing device 3. Accordingly, light reflected by PSD 4 is not received again by PSD 4, and returning of light reflected by PSD 4 to PSD 4 is prevented by the trapping device 8. Thus, an error of distance measurement is reduced, and object detection can be made at high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a photoelectric object detection device that detects a detected object using a triangulation method.

[Background technology]

Conventionally, this type of photoelectric object detection device, which detects objects to be detected using a triangulation method, projects a light beam (P) toward the flash of the object to be detected, as shown in Figures 2 and 3. A light projecting means TI) and a light beam (
A condensing means (3) for condensing the reflected light (8) of P) and a condensing surface of the condensing means (3) are arranged and output two kinds of conflicting detection signals by movement of the condensed spot. It is composed of a line image sensor (4), a discrimination means (5) for discriminating the object to be detected based on the level ratio of both detection signals, and a light projection means (1), a synchronization signal for setting the light projection timing. An oscillation circuit that generates a light beam (P), a drive circuit (11), a light projecting element α such as a light emitting diode or a laser diode, and a light projecting optical system H such as a condenser lens that forms a light beam (P). The light-receiving means (2) is arranged in parallel with the light-emitting means (1) at a predetermined distance J0, and the light-emitting/light-receiving means (11) is arranged in a triangular manner with respect to the 21 detected objects (3). This light receiving means (2) includes a condensing means (3) consisting of a convex lens for condensing the light reflected by the object to be detected (3), and a condensing means (3) arranged on the condensing surface of the condensing means (3). It is composed of a line image sensor (4) that outputs two types of contradictory detection signals by the movement of a light spot (S), and this line image sensor (4) has a condensing means (3 ) is arranged in the light focusing plane of the light spot (S), and outputs a detection signal IA of Kintetsu 1 which increases in accordance with the amount of movement when the focused spot (S) moves in one direction, and 1g2 which decreases in accordance with the amount of movement. Outputs the detection signal ■.

This line image sensor (4) is, for example, a semiconductor device detection element (hereinafter P
SD(4)) is formed by Vc, and PSD(4) is formed with
) is shown in Figure 4(a)K, as shown in Figure 4(a)K.
0, a P layer (31a) is formed on the front surface, an N layer (31b) is formed on the back surface, and one layer (31c) is formed in the middle.

is now output. This signal current IA is a signal that increases in proportion to the amount of movement of the focused spot φ when it moves in one direction, and the signal current IB is a signal that decreases in proportion to the amount of movement. Of course, the signal current IA,
It goes without saying that I is proportional to the amount of light. Figure 4 (
b) shows the equivalent circuit of PSD (4) on the upper floor, in which (Pi) is a current source and (D.

) is the ideal diode, (Go) is the junction capacitance, (Rt)
is the parallel resistance, and (Ro) is the interelectrode resistance. In addition, P.S.
In place of D(4), contradictory signal current IA% according to the movement of the focused spot (S) when the distance J changes
Needless to say, anything that can get IB is good. Discrimination means (slaPSD) determines whether the detected object (3) is present within a predetermined detection area based on the output of 41 and controls the output circuit (6) and the operation display circuit (7). This determination method (5
) is the signal current IA% of P S D (4) 6- et al.
A light receiving circuit (2) that amplifies and converts B to signal voltage vA%VB
1a) (21b) and logarithmic amplification circuits (22a) (22b)
) and logarithmic amplification circuit (22a) output! A subtraction circuit that subtracts the output inv of the logarithmic amplification circuit (22b) from nvA is compared with the operation level Vs set by the subtraction circuit output JnV, /VB and the detection area setting volume (24a) K. Subtraction circuit @ Comparison circuit (24
1, the output of the logarithmic amplification circuit (22b) - a comparison circuit that compares the output of the logarithmic amplification circuit (22b) with gnVB and the signal vSI to determine whether the light emission and light reception levels are above the normal operating level, and the comparison circuit (241 (c)). AND circuit that takes the logical AND of outputs □□□
and the emission timing of the light beam (P) from the light emission element (11) (the synchronization signal output from the oscillation circuit (1 (ll))
sampling the output of the AND circuit in synchronization with K
It is formed with a signal processing circuit Qη that reliably determines whether or not the detected object (3) exists within the detection area, and the output of the signal processing circuit is connected to a relay for load control, The light receiving circuit (21a) (21b) passes only the pulsed optical signal and cuts the DC optical signal, It includes a bandpass filter circuit that passes only the frequencies of .

Now, when the object to be detected (3) is located at a distance of J, 42% from the photoelectric object detection device (to) as shown in Fig. 5(a), PS set up
The positions of the focused spots (S) relative to D(4) are as shown in FIG. S)
moves in the direction of arrow M, and the signal currents IA, IB output from the PSD (41) become position signals corresponding to the position of the condensed spot (S). 21b) A signal voltage vA%VB proportional to the signal currents IA and IB of the K lever is formed, and a logarithmic amplification circuit (
22a) Logarithmically amplified voltage in (22b) -gnVA,
By subtracting nonnVB in the subtraction circuit (c), the logarithm value of the level ratio of the signal voltages V, , VB is outputted from the subtraction circuit (c). This subtraction circuit @output JnV person/VB changes depending on the distance lid to the detected object (3). Therefore, an accurate detection area can be easily set by appropriately setting the operating level Vs using the detection area setting polyimum (24a) of the comparison circuit, and the subtracting circuit @output JnVA/VB will be lower than the operating level V8. When this happens, the output of the comparison circuit (to) becomes H level. At this time, the light emission and light reception levels are within the normal operating range, and the logarithmic term middle circuit (22b) output ff1n
If VB is equal to or higher than the reference level Vs1, the output of the comparison circuit (to) also goes to H level, and the AND circuit output goes to H level (to the output circuit via the signal processing circuit Qη) and to the operation display circuit). K is set to be activated. In this conventional example, the discriminating means (6) calculates the logarithm of the level ratio of the signal amplified by the signal current correction % Ii output from the PSD [4], and determines whether the calculated value is a predetermined value. Since the output circuit (6) is activated by determining whether the object to be detected (3) is within the detection area or not, it can be detected regardless of the light reflectance of the object to be detected (3). The area can be set, and the projection and reception optical system (L field 31) is designed to avoid being affected by dirt or deviation of the optical axis.

FIG. 6 shows an example in which the optical system is housed in a small housing (7). By the way, in such a photoelectric object detection device, the light-receiving lens of the condensing means (3) and the light-receiving surface of the PSD (4) face each other directly (the light-receiving lens and the PSDT 41 are parallel).
Therefore, the light imaged on PSD (4)
(There was a problem that the light was reflected by the light receiving surface of 41, further reflected by the rear surface of the light receiving lens, and received again by PSD (41), causing distance measurement errors.Especially when performing object detection with high accuracy of 1) had become a big problem.

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to provide a photoelectric object detection device that has little distance measurement error and is capable of detecting objects with high precision. .

[Disclosure of the invention]

(Embodiment) Fig. 1 shows an embodiment of the present invention, in which the light receiving surface of the PSD (4) is aligned with the light receiving lens of the condensing means (3) in a photoelectric object detection device similar to the conventional example. The trap means (8) for the light reflected by the light receiving surface of %PSD (41) is provided on the inner surface of the housing (7).
8) is formed by pasting a light absorbing material such as carbon-containing resin or malt plane for camera light-shielding on the inner surface of the housing (7), but it is not possible to paint it with low reflectivity such as black or matte black, or paint. may also be applied to the housing (7).
The trap means (8) may be formed by forming a diffused reflection surface by applying pear-shaped processing or sawtooth processing to the inner surface of the member. Furthermore, it goes without saying that the bottom of the housing (7) itself may be made of black resin containing carbon.

In the embodiment, the PSD [4] is tilted so that the reflected light from the light-receiving surface of the PSD (4) does not enter the light-receiving lens of the condensing means (3). ,
The reflected light reflected at PSD (41) is returned to PSDT41.
However, since the reflected light from the PSD (4) is prevented from returning to the PSD (4) by the trap means (81K), unnecessary light may be received by the PSD (41). This reduces distance measurement errors and enables highly accurate object detection.In addition, if the PSD (4) cannot be tilted slightly due to miniaturization, the PSD
A part of the reflected light in (4) may be made to enter the light receiving lens.

〔Effect of the invention〕

As described above, the present invention includes a light projecting means for projecting a light beam onto an object to be detected, and a light projecting means disposed at a predetermined interval on the side of the light projecting means to collect light reflected from the light beam by the object to be detected. A condensing means that emits light; a line image sensor that is disposed on the condensing surface of the condensing means and outputs two types of contradictory detection signals as the condensed spot moves; In a photoelectric object detection device comprising a discrimination means for discriminating an object, the light receiving surface of the line image sensor is tilted so as not to directly face the light receiving lens of the condensing means, and reflected light is trapped by the light receiving surface of the line image sensor. The means is provided on the inner surface of the housing, and since the light reflected by the light receiving surface of the line image sensor is not received by the line image sensor again, distance measurement errors are reduced and objects can be detected with high precision. There is an effect that it can be done.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main part of an embodiment of the present invention, FIG. 2 is a schematic diagram of the main part of a photoelectric object detection device according to the present invention, and FIG.
The figure is a block circuit diagram of the same as above, FIG. 4(a) is a sectional view of the main part of the same as above, FIG. 4(b) is an equivalent circuit diagram of the main part of same as above, FIG. 1 is a schematic configuration diagram of main parts of a conventional example. (1) is a light projecting means, (3) is a condensing means, (4) is a line image sensor, (5) is a discrimination means, (7) is an ilt housing, and (8) is a trap means. Agent Patent Attorney Ishi 1) Chief 7 Figure 1 Figure 4 (') (b) Figure 5 Figure 6 Procedural Amendment (Voluntary) 1985 5ri! 3rd, 1985 Patent Application No. 60004 2, Name of the invention Photoelectric object detection device 3, Relationship with the case of the person making the amendment Patent applicant address Address 1048 Kadoma, Kadoma City, Osaka Prefecture Name (58
3) Matsushita Electric Works Co., Ltd. Representative: Sadao Fujii 4, Agent postal code: 530 Address: 1-12-17-5 Umeda, Kita-ku, Osaka City Date of amendment order: 6 Number of inventions increased by amendment: None 1) The scope of claims of this application will be amended as follows. [(1) A light projecting means for projecting a light beam onto the object to be detected, and a condenser arranged at a predetermined interval on the side of the light projecting means to collect the summer light of the light beam from the object to be detected. and a light beam disposed on the condensing surface of the condensing means and outputting two types of contradictory detection signals by movement of the condensing spot.
In a photoelectric object detection device comprising a detector and a discrimination means for discriminating the object to be detected based on the level ratio of both detection signals, the light receiving surface of the center five and one detector is used as the light receiving surface of the light collecting means. The photoelectric type % type % is characterized by being tilted so as not to directly face the lens, and having means for trapping reflected light by the light receiving surface of the light receiving surface provided on the inner surface of the lens.Line 9, 11 In lines 13, 14, and 5th to 6th lines on page 11, we have corrected ``line image sensor'' to ``light spot position detection element.''

Claims (1)

[Claims] (1) A light projecting means for projecting a light beam onto an object to be detected, and a condenser arranged at a predetermined interval on the side of the light projecting means to collect light reflected from the light beam by the object to be detected. optical means;
A line image sensor disposed on a light collecting surface of the light collecting means and outputting two types of contradictory detection signals by movement of a focused spot; and a discrimination means for discriminating a detected object based on a level ratio of both detection signals. In a photoelectric object detection device consisting of
Photoelectric object detection characterized in that the light-receiving surface of the line image sensor is tilted so as not to directly face the light-receiving lens of the condensing means, and a means for trapping light reflected by the light-receiving surface of the line image sensor is provided on the inner surface of the housing. Device.