JPH1082633A - Distance-measuring sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distance-measuring sensor by which a distance up to an object can be measured precisely even when disturbance light exists. SOLUTION: A light-emitting diode(LED) 1 intermittently emits a beams of light to an object. A position-sensitive device(PSD) 2 generates a current according to the intensity of received light, and the current is distributed in a ratio which is decided by a light receiving position so as to be output as a current I1 and a current I2 . A switch 4 and a switch 5 transfer the output of the PSD 2 to a signal processing part 6 when the LED 1 emits the light, and they transfer the output to a quantity-of-light computing part 7 when the LED does not emit light. The signal processing part 6 computes the ratio of the I1 to the I2 . The quantity-of-light computing part 7 computes the intensity of disturbance light on the basis of the sum of the I1 and the I2 when the LED 1 does not emit light. A distance computing part 8 comprises a table 9 in which the relationship between the output data (the ratio of the I1 to the I2 ) of the PSD when the LED 1 emits light and a distance up to the object is stored while the intensity of the disturbance light is used as a parameter. By using the output of the signal processing part 6 and that of the quantity-of-light computing part 7, the table 9 is retrieved so as to obtain the distance up to the object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring sensor for measuring a distance to an object using light.

[0002]

2. Description of the Related Art Sensors (distance measuring sensors) for measuring the distance from a reference point to an object using light are widely used in various fields. One of the distance measurement sensors is PSD (Po
A configuration using a sitionSensitive Device) is known. Hereinafter, a distance measuring sensor using a PSD will be described.

FIG. 7 is a diagram for explaining the principle of distance measurement using a PSD. When detecting the distance to the object by using the PSD, as shown in FIG. 7A, the beam output from the LED 1 is irradiated on the object, and the reflected light from the object is received by the PSD 2. If the distance to the object is different, the angle of incidence of the reflected light on the lens 3 is different.
The position where light is condensed on the second light receiving surface differs.
FIG. 7 shows that the light receiving position of the reflected light in the PSD 2 is different between the case where the target object is at the point A and the case where the target object is at the point B.

[0004] The output of PSD2 is the intensity of the received light and P
It depends on the light receiving position on the light receiving surface of SD2. That is, the PSD 2 generates a current having a magnitude corresponding to the intensity of the received light. The PSD 2 has two output terminals, as shown in FIG. 7B, and distributes the current generated according to the intensity of the received light at a ratio determined by the light receiving position on the light receiving surface. And outputs the current I ₁ and the current I ₂ .

As described above, in the distance measuring sensor using the PSD, the light receiving position of the reflected light is determined according to the distance to the object, and the currents I ₁ and I ₂ are output at a ratio determined by the light receiving position. Therefore, the distance to the object can be obtained by detecting the ratio between the current I ₁ and the current I ₂ .

FIG. 8 is a diagram showing the relationship between the distance to the object and the output of the PSD. Here, the PSD output is a ratio of the current I _{1 to} the current I ₂ . As shown by a solid line in the figure, the output of the PSD decreases in a hyperbolic manner as the distance to the target increases. The distance measurement using the PSD is usually performed in such a range that the output decreases in a hyperbolic manner.

[0007] The distance measurement using the PSD is in principle as described above.
Not only the reflected light of the beam output from the device, but also disturbance light. Therefore, in order to measure the distance to the target, the influence of disturbance light must be removed.

In order to remove the influence of disturbance light, PSD
Note that LED2 is always receiving disturbance light, and LED1
Is output as discontinuous light emission (pulse output). And L
Output of PSD2 when ED1 is emitting light and LED
The disturbance light is canceled by determining the difference from the output of PSD2 when 1 is not emitting light.

[0009] For example, the output of PSD2 when LED1 is emitting light, a _{I 1 = 150, I 2 =} 200, the output of PSD2 when LED1 is not emitting light is, I ₁ = 50, I ₂ = 50
The output of PSD2 due to reflected light beam output from the _{1, I 1 = 100 (= 150-50} ), I 2 = 150
(200-50). In this case, the distance to the object can be obtained from the graph shown in FIG. 8 based on PSD output = I ₂ / I ₁ = 1.5.

[0010]

SUMMARY OF THE INVENTION As described above, the PSD
The distance measuring sensor using the method measures the distance to the target object while removing the influence of the disturbance light. However, in the above method, the error increases as the intensity of the disturbance light increases. That is, the above method is an effective approximation when the disturbance light is small, and the error increases as the disturbance light increases.

[0011] For example, in the measurement of when the actual distance to the target is x _0, PS when ambient light was not
D output is assumed to be y _0. However, when the ambient light is increased, the remaining even error to cancel the disturbance light by using the above method, the output of the PSD is the y ₁ when the actual distance to the object was x _0. In other words, when the PSD output is y ₀ and the distance to the object is to be obtained from the value, it is estimated that the distance = x ₀ from the PSD output-distance curve shown by the solid line in FIG. The relationship between the PSD output and the distance when the disturbance light is large is as shown by a broken line, and the actual distance to the object at that time is x ′.
It is. As a result, x ₀ −x ′ as an error due to disturbance light
Will occur.

As described above, in the conventional distance measuring sensor using the PSD, when the disturbance light becomes large, the influence cannot be completely canceled and a measurement error occurs. An object of the present invention is to provide a distance measuring sensor that can accurately measure the distance to an object even when there is disturbance light.

[0013]

The distance measuring sensor according to the present invention comprises:
A light-emitting means for intermittently outputting light for distance measurement, and a light-receiving means for receiving light output from the light-emitting means and reflected on the object and outputting light-receiving information according to the position at which the light was received and the amount of light, Signal processing means for generating position information data based on the light receiving information output by the light receiving means; light amount calculating means for generating light amount data based on the light receiving information output by the light receiving means; and the light emitting means outputting light Switch means for transferring the output of the light receiving means to the signal processing means when the light emitting means is not outputting light, and transferring the output of the light receiving means to the light quantity calculating means when the light emitting means is not outputting light; Distance data determined by a combination with the light amount data is stored, and the stored distance data is output based on the outputs of the signal processing means and the light amount calculating means. And a calculating means for calculating a distance to the object by extracting data.

In the above configuration, the position information data output from the signal processing means is output from the light receiving means when the light emitting means emits light, and is information relating to the distance to the object. Further, the light amount data which is the output of the light amount calculating means is the output of the light receiving means when the light emitting means is not emitting light, and thus represents the intensity of disturbance light.

A distance to an object and position information data corresponding to the distance are obtained in advance using the intensity of disturbance light as a parameter. At the time of distance measurement, the distance to the target object is calculated by detecting disturbance light intensity and position information data.

A distance measuring sensor according to another aspect of the present invention includes a light receiving means for outputting position information data in accordance with a position at which reflected light output from a light emitting element and reflected by an object is received; A light quantity detecting means for detecting the light quantity, and distance data determined by a combination of the position information data and the light quantity near the light receiving means, and the stored distance based on the outputs of the light receiving means and the light quantity detecting means. Calculating means for obtaining a distance to the object by extracting data.

In the above arrangement, the light quantity detecting means provided near the light receiving means detects the intensity of disturbance light applied to the light receiving means. Other operations are the same as those described above.

[0018]

Embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a distance measuring sensor using a PSD will be described. The method of measuring the distance of the distance measuring sensor using the PSD is as described in the related art.

In the distance measuring sensor according to the present embodiment, how the relationship between the distance to the object and the PSD output data (the ratio between the current I ₁ and the current I ₂ ) changes depending on the intensity of disturbance light. Obtain it in advance. When measuring the distance to the object, the intensity of disturbance light is measured. Then, the distance data corresponding to the PSD output data is extracted according to the intensity of the disturbance light using the correspondence relationship determined in advance.

FIG. 1 is a configuration diagram of a distance measuring sensor according to an embodiment of the present invention. In the configuration shown in the figure, PSD2 is regarded as receiving only disturbance light when LED1 is not emitting light, and PSD2 when LED1 is not emitting light.
The intensity of the disturbance light is obtained from the output of. Hereinafter, the operation of each unit will be described.

The LED 1 emits a beam intermittently.
This beam is, for example, an infrared pulse. PSD
2 is a light receiving element having a light receiving surface extending on a straight line,
The light receiving information is output according to the light receiving position on the light receiving surface and the light amount. That is, the PSD 2 generates a current according to the intensity of the received light, distributes the generated current at a ratio determined by the light receiving position on the light receiving surface, and outputs the current I ₁ and the current I ₂ . In FIG. 1, a lens for narrowing the output beam of the LED 1 to an appropriate spot diameter, a lens for collecting reflected light from an object on the PSD 2, and the like are omitted.

The switches 4 and 5 switch the destination of the output data of the PSD 2 in synchronization with the light emission / extinction timing of the LED 1. That is, as shown in FIG. 2, the switches 4 and 5 are connected to the terminal A when the LED 1 is emitting light, transfer the output of the PSD 2 to the signal processing unit 6, and
When 1 is off, it is connected to the B terminal and PSD2
Is transferred to the light quantity calculation unit 7.

The signal processor 6 calculates the ratio between the current I ₁ and the current I ₂ . These currents I ₁ and I ₂ are
The output of PSD2 when LED1 is emitting light. During the period when LED1 is emitting light, PSD2 is at LE level.
The light emitted from D1 and reflected on the object (reflected light) and the disturbance light are received. For this reason, the signal processing unit 6
Calculates the ratio between the current I ₁ and the current I ₂ generated by receiving the reflected light and the disturbance light. The output of the signal processing unit 6 is passed to the distance calculation unit 8 as position information y.

A distance measuring sensor using a PSD is shown in FIG.
As described with reference to, but it is possible to know the distance to the target by calculating the ratio of the current I ₁ and the current I _2, which is the case when the disturbance light did not. Therefore, in the distance measuring sensor of the present embodiment, the ratio between the current I ₁ and the current I ₂ is calculated in the signal processing unit 6 in a state that the reflected light and the disturbance light are included, and the distance calculation unit 8 is used.
Calculates the distance to the object in consideration of the ratio and the intensity of disturbance light.

The light amount calculator 7 calculates the sum of the current I ₁ and the current I ₂ . These currents I ₁ and I ₂ are LE
The output of PSD2 when D1 is not emitting light,
During the period when LED1 is not emitting light, PSD2 receives only disturbance light. Therefore, light intensity calculator 7 will calculate the sum of the currents I ₁ and the current I ₂ that is generated by receiving the disturbance light. Here, the PSD 2 generates a current according to the intensity of the received light, distributes the generated current at a ratio determined by the light receiving position, and distributes the currents I ₁ and I ₂
Therefore, the sum of the current I ₁ and the current I ₂ is P
The value indicates the intensity of the received light of SD2. Therefore, the light amount calculation unit 7 calculates the intensity of the disturbance light. The output of the light quantity calculator 7 is passed to the distance calculator 8 as disturbance light intensity information L.

The distance calculator 8 calculates the relationship between the output of the PSD 2 when the LED 1 is emitting light (the ratio of the current I ₁ to the current I ₂ when the LED 1 is emitting light) and the distance to the object. It has a stored table 9. FIG. 3 shows the relationship between the output of PSD2 and the distance to the object when LED1 emits light.

In FIG. 3, the vertical axis is the position information y calculated by the signal processing unit 6, and is the ratio between the current I ₁ and the current I ₂ when the LED 1 is emitting light. In the figure, the relationship between the position information y and the distance to the object when there is no disturbance light is drawn by a solid line. As for the relationship between the position information y and the distance to the object, the deviation from the curve shown by the solid line increases as the disturbance light increases. In the figure,
The relationship between the position information y using the intensity of disturbance light as a parameter and the distance to the object is indicated by a wavy line, a one-dot chain line, and a two-dot chain line.

A graph as shown in FIG. 3 is obtained by detecting the output of the PSD 2 one by one while changing the intensity of disturbance light and the distance to the object. The relationship between the position information y and the distance to the object may be obtained by simulation without actually performing the measurement.

Returning to FIG. Table 9 stores the data of the graph shown in FIG. That is, the table 9, the disturbance light intensity _{L 1, L 2, L 3} , L 4,. . . , Position information y ₁ , y ₂ , y ₃ , y ₄ ,. . . Is stored in advance. When creating the table 9, the distance to the target is measured under the condition that the intensity of disturbance light is Li and the position information is yi, and the distance data is written to a corresponding area in the table 9. For example, when the distance to the target is measured under the conditions of disturbance light intensity = L ₂ and position information = y ₂ , the distance data is written in a region corresponding to a hatched portion in the drawing. The position information y detected here is output data when the PSD 2 receives reflected light and disturbance light.

When the distance calculator 8 receives the position information y from the signal processor 6 and the disturbance light intensity information L from the light amount calculator 7, the distance calculator 8 retrieves the distance data by searching the table 9 using the information. . This distance data is the distance to the object.

As described above, in the distance measuring sensor having the above configuration, the intensity of the disturbance light received by the PSD is measured, and a calibration curve corresponding to the disturbance light intensity is taken out from a table prepared in advance, and the calibration curve is obtained. Since the distance from the curve to the object is obtained, the distance to the object can always be accurately measured even when disturbance light changes.

FIG. 4 is a configuration diagram of a distance measuring sensor according to another embodiment of the present invention. In the configuration shown in the figure, a light receiving element 11 is provided near the PSD 2 and the light receiving element 11 is
The intensity of the disturbance light received by SD2 is obtained. Light receiving element 11
Is, for example, a photodiode.

In the distance measuring sensor shown in FIG. 4, the output of the PSD 2 is passed to the signal processing section 6 and the output of the light receiving element 11 is passed to the light quantity calculating section 7. The configurations of the signal processing unit 6, the light amount calculation unit 7, and the distance calculation unit 8 are basically the same as those shown in FIG.

As described above, in the distance measuring sensor shown in FIG.
Since the intensity of the disturbance light is detected using the light receiving element 11 provided near the PSD 2, there is no need to switch the output of the PSD 2 using the switches 4 and 5 as in the configuration shown in FIG. It becomes unnecessary.

FIG. 5 is a flowchart for explaining the operation of the distance measuring sensor shown in FIG. 1 or FIG. Step S1
Then, the intensity of disturbance light is detected. This step is performed when the LED 1 is not emitting light in the configuration of FIG.
This is a process for obtaining the sum of the output currents of D2, and in the configuration of FIG. 4, a process for detecting the output current of the light receiving element 11.

In step S2, a PSD output-distance curve corresponding to the disturbance light intensity detected in step S1 is selected from table 9. This step is a process of selecting a row corresponding to the detected disturbance light intensity Li in the table shown in FIG.

In step S3, a PSD output is detected. Here, the PSD output is the ratio of the current I ₁ and the current I ₂ when LED1 is emitting light. Step S
In step 4, the PSD output detected in step S3 is converted into distance data using the PSD output-distance curve selected in step S2. That is, this step is a process of extracting distance data corresponding to the detected PSD output yi from the row selected from the table shown in FIG. 1 in step S2. And step S
In step 5, the distance data extracted from the table 9 is output as data indicating the distance to the object.

In the above embodiment, a linear light receiving surface is used.
Configuration using PSD with (one-dimensional configuration)
However, the present invention provides a two-dimensional PSD as shown in FIG.
It can be applied to the distance measuring sensor used. Two-dimensional PSD
In a distance measurement sensor using
And the distance to the object in each direction is 1
One PSD can be measured. The two-dimensional PSD is
The ratio of the current flowing to the opposite terminals with four output terminals
Rate (current I₁And current I_TwoAnd the current I _ThreeAnd electricity
Style I_FourFrom the ratio). Above PSD
Calculate the distance to the object from the intensity of the force and disturbance light
The procedure is basically the same as that of the distance measuring sensor of FIG. 1 or FIG.
is there.

Further, in the above embodiment, the description has been given of a distance measuring sensor using a PSD, but the present invention can be applied to a distance measuring sensor using a light receiving element whose output changes depending on a light receiving position.

[0040]

According to the distance measuring sensor of the present invention, the relationship between the distance to the object and the output of the device that receives the reflected light from the object is obtained in advance using the disturbance light applied to the device as a parameter. Since the distance data is obtained from the relationship obtained in advance by measuring the intensity of the disturbance light applied to the device and using the intensity of the disturbance light and the output of the device, even if the disturbance light changes, the target is always measured. The distance to an object can be measured accurately.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a distance measuring sensor according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the light emission timing of an LED and the operation of a switch of the distance measuring sensor shown in FIG. 1;

FIG. 3 is a diagram illustrating a relationship between a PSD output and a distance to a target object using the intensity of disturbance light as a parameter.

FIG. 4 is a configuration diagram of a distance measuring sensor according to another embodiment of the present invention.

FIG. 5 is a flowchart illustrating an operation of the distance measuring sensor according to the embodiment.

FIG. 6 is a diagram schematically showing a configuration of a distance measuring sensor using a two-dimensional PSD.

FIG. 7 is a diagram illustrating the principle of distance measurement using a PSD.

FIG. 8 is a diagram illustrating a relationship between a distance to an object and a PSD output.

[Explanation of symbols]

 Reference Signs List 1 LED 2 PSD (Position Sensitive Device) 4, 5 switch 6 Signal processing unit 7 Light amount calculation unit 8 Distance calculation unit 9 Table 11 Light receiving element

Claims (4)

[Claims] A light emitting means for intermittently outputting light for distance measurement; a light receiving means for receiving light output from the light emitting means and reflected on an object; receiving light information in accordance with a position at which the light is received and a light amount thereof; Light receiving means for outputting, signal processing means for generating position information data based on the light receiving information outputted by the light receiving means, light quantity calculating means for generating light quantity data based on the light receiving information outputted by the light receiving means, Switch means for transferring the output of the light receiving means to the signal processing means when the light emitting means is outputting light, and for transferring the output of the light receiving means to the light quantity calculating means when the light emitting means is not outputting light. And distance data determined by a combination of the position information data and the light quantity data, and stores the distance data based on the outputs of the signal processing means and the light quantity calculation means. Distance measuring sensor having a computing means for calculating a distance to the object, the by extracting the distance data stored. 2. A light emitting means for intermittently outputting light for distance measurement, and at least two output terminals for receiving light output from the light emitting means and reflected by an object, and receiving the light. Light receiving means for changing the ratio of the current flowing through the at least two output terminals according to the determined position; signal processing means for generating position information data based on the ratio of the current flowing through the at least two output terminals; Light amount calculating means for generating light amount data based on the sum of currents flowing through the at least two output terminals; and when the light emitting means is outputting light, transferring the output of the light receiving means to the signal processing means. Switch means for transferring the output of the light receiving means to the light quantity calculating means when the light emitting means is not outputting light, the position information data and the light And a calculating means for calculating a distance to an object based on the output of the signal processing means and the light amount calculating means and referring to the table based on an output of the signal processing means and the light quantity calculating means. Distance sensor. 3. A light receiving means for outputting position information data in accordance with a position at which the reflected light output from the light emitting element and reflected on the object is received; a light amount detecting means for detecting a light amount near the light receiving means; The distance data determined by the combination of the position information data and the light amount near the light receiving means is stored, and the stored distance data is extracted based on the output of the light receiving means and the light amount detecting means to reach the object. Calculating means for calculating the distance of the distance measuring sensor. 4. A distance measuring sensor for measuring a distance to an object using a PSD (position sensitive device), wherein the distance to the object and the intensity of disturbance light received by the PSD are used as parameters. The relationship with the output of the PSD is obtained in advance, and when measuring the distance to the object, the above PS is used.
A distance measuring sensor that measures the intensity of disturbance light received by D, and obtains a distance to an object by referring to the relationship obtained in advance using the measured disturbance light intensity and the PSD output.