JP2592055Y2 - Photoelectric sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

This invention illuminates an object to be detected conveyed to a detection position from a light projecting element and determines whether the object is appropriate based on the presence or absence of reflected light on the object. The photoelectric sensor that determines

[0002]

2. Description of the Related Art In a final stage of a manufacturing process of an electronic component, the product is conveyed to a detection position as an object to be detected in order to judge the suitability of the product, light is emitted from a light emitting element, and the product is reflected by its reflection state. A photoelectric sensor for judging suitability is generally used. This photoelectric sensor includes a different axis type and a coaxial type. In the former case, as shown in FIGS. 5A and 5B, the light receiving state of the light receiving element changes due to a change in the angle of reflection from the object at the detection position, and thereby the suitability of the object is determined. On the other hand, in the latter case, as shown in FIG. 6, the irradiation light path from the light projecting element coincides with the reflected light path from the object, and the reflected light reaches the light receiving element via the half mirror.

[0003]

However, in the above-mentioned off-axis type photoelectric sensor, not only when the object to be detected is improper as shown in FIG. The vertical direction, that is, even if an error occurs in the optical path direction, the reflection direction from the object to be detected changes,
There is a problem in that the object to be detected is determined to be inappropriate even though it is appropriate, resulting in malfunction.

In a coaxial photoelectric sensor, the direction of reflection from the object does not change even when the transport position of the object at the detection position causes an error in the optical path direction, and the state of the object is changed. On the other hand, since the light from the light projecting element passes through the half mirror and irradiates the object to be detected, the light quantity of the light projecting element is about four times larger than that of the off-axis type. Therefore, the voltage applied to the light emitting element becomes large, the driving circuit thereof becomes large, and the cost rises.

It is an object of the present invention to provide an off-axis type photoelectric sensor in which the range of change in the direction of reflection from the object when the transport position of the object at the detection position causes an error in the optical path direction is determined by the light receiving element. Provided is a photoelectric sensor capable of always determining the suitability of an object to be detected accurately by preventing the appropriate object from being determined to be improper when an error occurs in a transport position by setting a light receiving range. It is in.

[0006]

The photoelectric sensor of the present invention irradiates light from a light projecting element to a detection position, and responds to the light receiving state of the light receiving element of the reflected light on the detection object conveyed to the detection position. A light-receiving area of the light-receiving element, wherein the light-receiving area of the light-receiving element is set substantially equal to a fluctuation range of a reflection direction caused by a transport error of the object in the optical axis direction of the light-emitting element; Flow
Means for generating a detection signal based on the total current .

[0007]

According to the present invention, even if the object to be detected is conveyed with an error in the conveying position in the optical axis direction of the light projecting element with respect to the detection position, the reflected light from the normal object to be detected is normal. Is received by the light receiving element. Therefore, even if the detected object has a transport error, the suitability of the detected object can be accurately determined.

[0008]

FIG. 1 is a schematic view showing the structure of a photoelectric sensor according to an embodiment of the present invention. The photoelectric sensor 1 includes a light emitting diode 2 as a light emitting element, a PSD (position detecting element) 3 as a light receiving element, and lenses 4 and 5. The light emitting diode 2 transmits light through the lens 4 to the detection position 6. An object 7 to be detected is conveyed to the detection position 6 by a conveying means (not shown).

Light emitted from the light emitting diode 2 is reflected by the object 7 conveyed to the detection position 6, and the reflected light passes through the lens 5 and reaches the PSD 3. This P
SD3 receives light within a predetermined range, and changes the current value at both ends in accordance with the position at which the light is received. Generally, the SD3 is determined based on the current value at both ends caused by a change in the reflection angle of the object. It is used when measuring the distance to a detection object.

The light receiving range of the PSD 3 is displaced into upper and lower allowable error ranges 7b and 7c around the light receiving position Pa of the reflected light of the object 7 at the reference transport position 7a of the object 7 at the detecting position 6. Is set to a range including the incident positions Pb and Pb of the reflected light in the case of the above.

FIG. 2 shows an output circuit of a detection signal of the photoelectric sensor. The currents I ₁ and I ₂ at both ends of the PSD ₃ are
The sum is obtained as a total current, which is converted into a voltage by the current / voltage converter 11. This current / voltage converter 1
1 is input to the detector 14 via the filter 12 and the amplifier 13. The light-emitting diode 2 is included in the detector 14.
A synchronization signal for detection is supplied from an oscillator 16 that supplies a modulation signal to the drive circuit 15 of FIG. The detection unit 14 detects the output of the amplifier 13 in synchronization with the driving timing of the light emitting diode 2 based on the synchronization signal, and outputs the detection signal via the filter 17 and the buffer 18.

With the above configuration, the PSD 3 is connected to the object 7 to be detected.
Is received by the current / voltage converter 11 in a state (I ₁ + I ₂ ) in which the currents at both ends are added.

The output of the current / voltage converter 11 is amplified and detected in synchronization with the light irradiation timing of the light emitting diode 2, and is output as a detection signal. Therefore, P
When reflected light enters the light receiving range of SD3, a constant current (I ₁ + I ₂ ) is always input to the current / voltage converter 11 regardless of the light receiving position. As described above, the light receiving range of the PSD 3 is set corresponding to the transfer positions 7b to 7c of the detection target 7 with respect to the detection position, so that even if an error occurs in the transfer position of the detection target 7, the detection target is detected. Things can be detected accurately.

FIG. 3 is a schematic view showing an example of a use state of the photoelectric sensor. In this example, the lead frame 27 of the electronic component is an object to be detected, and is used to determine whether the lead frame 27 is in a normal horizontal state or in an abnormal bent state. As shown in FIG. 3A, when the normal lead frame 27 is transported to the reference position 7a of the transport position 6, the reflected light is input to the center position Pa of the PSD 3, and the detection signal is output from the output circuit. Is output. In addition, as shown in FIG.
Even when 7 is conveyed with an error on the upper side, if the error range is within the range of the upper allowable error position 7b, the reflected light on the lead frame 27 is received by the PSD 3,
A detection signal is output from the output circuit. On the other hand, as shown in FIG. 3C, when the abnormal lead frame 27 'is transported, even if the transport position is the reference position 7a, the PSD 3 receives no reflected light and outputs No detection signal is output from the circuit. Thus, even if an error occurs in the transport position, it is possible to accurately determine the suitability of the lead frame 27 based on the presence or absence of the detection signal.

In this embodiment, the light receiving element is a PSD.
However, as shown in FIG. 4A, a predetermined number of multi-point photodiodes 31a to 31c may constitute a light receiving region in a predetermined range. In this case, the output circuit is connected to each photodiode 3 as shown in FIG.
Each of the current / voltage converters for converting the currents 1a to 31c into a voltage is provided, and the output voltages of the plurality of current / voltage converters are added in an adding circuit.

Although a light emitting diode is used as a light emitting element in this embodiment, another light emitting element such as a laser diode may be used.

[0017]

According to the present invention, even when an error occurs in the transport position of the detected object with respect to the detected position, the reflected light from the detected object is received by the light receiving element, so that the detected object can always be accurately detected. There is an advantage that can be detected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a photoelectric sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing an output circuit of the photoelectric sensor.

FIG. 3 is a schematic diagram illustrating a usage state of the photoelectric sensor.

FIG. 4 is a diagram showing a photoelectric sensor according to another embodiment of the present invention.

FIG. 5 is a view showing a conventional off-axis photoelectric sensor.

FIG. 6 is a view showing a conventional coaxial photoelectric sensor.

[Explanation of symbols]

 1-photoelectric sensor 2-light-emitting diode (light-emitting element) 3-PSD (light-receiving element) 6-detection position 7-object to be detected

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-278111 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01B 11/00-11/30 G01B 9 / 00 G01V 9/04

Claims (1)

(57) [Scope of request for utility model registration] 1. A photoelectric sensor which irradiates light from a light projecting element to a detection position and outputs a detection signal according to a light receiving state of a light receiving element of reflected light on an object conveyed to the detection position, The light receiving range of the light receiving element is set substantially equal to the fluctuation range of the reflection direction caused by the transport error of the object in the optical axis direction of the light projecting element, and the total amount of light flowing through the light receiving element is set.
A photoelectric sensor, comprising: means for generating a detection signal based on a current .