JPH04181112A - Distance measuring device - Google Patents

Abstract

PURPOSE:To enable distance to an object to be measured measured easily and accurately by comparing an output sum of a light-receiving region with a reference voltage and controlling an amount of projected light of an light-projection element so that the comparison result may be a constant. CONSTITUTION:A voltage which is equal to an output sum of a light-receiving element 2 when a target object is at a closest position within a measurement range is set to a reference voltage Vth 10, an output sum obtained by adding 7 outputs Va - Vc of light-receiving regions 2a - 2c of the element 2 which is divided into three parts and the voltage Vth are compared 8, and the differential voltage Vs is input to a light-projection control circuit 6. This voltage Vs increases according to decrease in the amount of received light accompanied by remoteness of the target object, the circuit 6 controls the amount of projection light of the light-projection element 1 according to the level of the voltage Vs and maintains the amount of received light of the element 2 to be constant regardless of change in the target object. Then, the output Vc of the region 2c is output as a distance output V through an amplifier 9 but the amount of received light is exclusively due to change in inclination angle of the reflection light so that the output Vc (output V) is in straight-line relationship with a distance to the target object, thus enabling distance to the target object to be measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Field of Application This invention relates to a light projecting element that projects light onto a target object, and a light emitting element that emits light from the light projecting element in a direction perpendicular to the light projecting direction of the light projecting element. The present invention relates to a triangulation type distance measuring device that includes a light receiving element that receives reflected light from a target object at a position separated by a certain baseline length and outputs a signal corresponding to the amount of received light.

(b) Conventional technology In a distance measuring device that measures the distance to a target object using a triangulation method, generally a light emitting element 1 is used as shown in FIG.
The light is projected onto the target object 3 through the light projecting lens 4, and the reflected light from the target object 3 is received by the light receiving element 20 through the light receiving lens 5. Emitter lens 4 and receiver lens 5
and are installed apart from each other by the base line length in a direction perpendicular to the light projection direction of the light projection element 1. In this configuration, when the distance from the light projecting lens 4 to the target object 3 changes, the incident angle of the light reflected from the target object 3 to the light receiving lens 5 changes, and the light receiving point on the light receiving element 20 changes. The amount of light received by the light receiving element 20 changes due to the displacement of the light receiving point, and by detecting the output of this light receiving element 20, the distance tlR between the light projecting section and the target object is detected.

In such a distance measuring device, it is necessary to take versatility into consideration and to be able to set the distance measuring range according to the usage situation. Therefore, conventionally, the length of the base line is made variable so that the angle of incidence of the reflected light on the light receiving element 20 changes even if the position of the target object 3 does not change. That is, the outputs of different regions of the light receiving element 20 (for example, the outputs of divided regions 2 in FIG.
0a.

20b), the distance detection output can be varied by displacing the lens 5 so that the distance detection output matches the distance detection output.

To explain specifically, in the above state, the distance R to the target object
When the distance changes to become the distance HR', the light receiving point on the light receiving element 20 changes, and the outputs of the regions 20a and 20b no longer match. Conversely, it shows that when the region 20a and the region 20b match, the distance AiIR is reached.

This makes it possible to set a desired distance by moving the lens 5, and to obtain output information at that time.

[C) Problems to be Solved by the Invention However, in the conventional distance measuring device described above, the lens must be displaced in order to change the base line length, and a mechanism for this is required, resulting in a complicated and large structure. There was a problem that led to

An object of the present invention is to control the amount of light emitted by a light emitting element so that the amount of reflected light from a target object enters the light receiving element is constant, and to make it possible to change this constant amount. An object of the present invention is to provide a distance measuring device that can arbitrarily change the movement range of a target object in response to the same output signal, and that can reduce the size of the device by eliminating the need for a complicated mechanism related to lens movement. (d) Means for Solving the Problems The distance measuring device of the present invention includes a light projecting element that projects light onto a target object, and a constant direction from the light projecting element in a direction perpendicular to the light projecting direction of the light projecting element. In a triangulation type distance measuring device comprising a light receiving element that receives reflected light from a target object at a position separated by a baseline length and outputs a signal according to the amount of received light, the light receiving area of the light receiving element is set to the baseline. Comparing means that divides the light receiving area into a plurality of parts in the longitudinal direction, sets the output of a part of the plurality of light receiving areas as a ranging output, and compares the remaining light receiving area or the sum of outputs of all the light receiving areas with a reference voltage; The present invention is characterized in that it includes a reference voltage setting means for arbitrarily setting a reference voltage, and a light projection control means for controlling the amount of light emitted by the light emitting element so that the comparison result of the comparison means becomes a constant value.

te1 effect In this invention, triangulation distance measurement is performed in which the light reflected from the target object of the light projected from the light projecting element is received by the light receiving element, and the distance to the target object is measured based on the amount of light received by the light receiving element. It will be done. In such a triangulation distance measurement method, as the distance to the target object changes, the angle of incidence of the reflected light on the light receiving element changes as shown in Figure 1, and the light receiving point (light receiving range) of the reflected light on the light receiving element changes. center) changes. That is, when the target object is at position 3a in FIG. 1, if the light receiving point is at the center of the light receiving area 2c, as the target object moves away from position 3b to position 3c, the light receiving point moves to the left side of the light receiving element 2C. Moving. Therefore, the amount of light received by the light receiving element 2c gradually decreases as the target object moves away. Additionally, as the target object moves away, the optical path from the light projecting element l to the light receiving element 2 via the target object becomes longer, and the amount of attenuation of the light increases accordingly, causing the amount of light that enters the entire light receiving element 2. decreases.

At this time, the sum of the outputs of any light-receiving areas 2a, 2b or all light-receiving areas 2a to 2c of the light-receiving element 2 is compared with a reference voltage in the comparison means, and light is emitted so that the comparison result of this comparison means takes a constant value. The amount of light emitted from element 1 is controlled. As a result, the amount of light incident on the entire light receiving element 2 is always constant. Therefore, the output Vc of the light-receiving region 2c changes only according to the change in the angle of incidence due to the displacement of the target object, that is, the displacement of the light-receiving point, and the position of the target object can be specified by detecting the output Vc of the light-receiving region 2c.

Here, if the reference voltage in the comparison means is changed, the amount of light incident on the entire light receiving cable 2 is changed. Therefore, even if the target object is at the same position, the output of the light receiving area 2C changes before and after switching the reference voltage. In other words, the position of the target object corresponding to the output signal of the light receiving area 2C changes before and after switching the reference voltage. therefore,
By appropriately setting the reference voltage, the movement range of the target object corresponding to the range of the output signal of the light receiving element 2 can be arbitrarily set.

(f) Embodiment FIG. 2 is a block diagram showing the configuration of a distance measuring device that is an embodiment of the present invention.

A light projecting element 1 composed of an LED or the like is driven by a light projecting control circuit 6. The output of the comparator 8 is input to the light projection control circuit 6 . In this comparator 8, the output of the adder circuit 7 is compared with the reference voltage Vt1. The adder circuit 7 receives the output V of each of the light receiving areas 2a to 2c divided into three in the light receiving element (multi-division photodiode) 2.
The output sum is calculated by adding a−Vc. Therefore, the difference between the output sum of the light receiving elements 2 and the reference voltage Vi is input to the light projection control circuit 6.

The reference voltage Vth in the comparator 8 is supplied from a reference voltage setting circuit 10. In this reference voltage setting circuit 10, the reference voltage Vl supplied to the comparator 8 can be set to any value. The reference voltage setting circuit 10 controls the light receiving element 2 when the target object is at the closest position to the measurement range.
Set a voltage equal to the output sum of as the reference voltage vth,
The output of the comparator 8, that is, the differential voltage Vs input to the light projection control circuit 6 increases as the amount of light received by the light receiving element 2 decreases as the target object becomes more remote.

The light projection control circuit 6 increases the drive voltage applied to the light projection element 1 as the differential voltage Vs increases. As a result, the amount of light emitted by the light projecting element 1 changes depending on the magnitude of the differential voltage Vs, and the amount of light received by the light receiving element 2 is controlled so as to be always constant regardless of changes in the target object.

The output Vc of the light-receiving region 2c forming part of the light-receiving element 2 in which the amount of light received is maintained constant in this way is taken out as the ranging output V via the amplifier 9. Since the amount of light reflected from the target object that enters the light-receiving element 2 is always kept constant, the amount of light received in the light-receiving area 2C depends exclusively on changes in the angle of incidence of the light reflected from the target object. The output voltage Vc (distance measurement output V) has a linear relationship with the distance R to the target object within a predetermined range, as shown by the solid line in FIG. Therefore, by setting this predetermined range as the measurement range, the distance R from the ranging output V to the target object can be easily and accurately measured.

Here, the reference voltage V in the reference voltage setting circuit 10 is set to a lower reference voltage V'
When switched to , the distance measurement output V, which corresponded to the distance R3 at the reference voltage I, corresponds to the distance R2 at the reference voltage I'. In this way, the reference voltage
By changing the value of , the distance R to the target object corresponding to the distance measurement output V changes. Since the amount of light emitted from the light emitting element 1 is controlled so that the amount of light received by the light receiving element 2 is constant even at the reference voltage Vtk', the relationship between the ranging output V and the distance R is as shown by the broken line in FIG. There is a linear relationship between Here, since the ratio between the reference voltage Vth and the reference voltage V' is equal to the ratio between the distance Is Rl and the distance R2 in FIG. 4,
By changing the reference voltage V, the movement range of the target object corresponding to the output range of the ranging output V can be arbitrarily changed without changing other circuit configurations.

Note that the number of divisions of the light receiving element 2 is not limited to three.

FIG. 3 is a diagram showing the configuration of a distance measuring device according to another embodiment of the present invention.

As shown in the figure, the light-receiving element 12 is divided into two parts, and the output vb of one light-receiving area 12b is used as the ranging output V, and the output Va of the other light-receiving area 12a is set as the reference voltage V1 in the comparator 22. A comparison is made, and the difference voltage Vs is outputted to the light projection control circuit 21. If the amount of light received in the light-receiving area 12a is sufficient even if the target object is displaced within the measurement range, the amount of light received by only this light-receiving area 12a is considered to be a large amount of light reflected from the target object to the light-receiving element 12, and the second The configuration of the device can be further simplified by eliminating the adder circuit 7 shown in FIG. In this case, the light receiving area 1
The ranges of 2a and 12b do not need to be the same, and the light receiving area 12a may be larger than the light receiving area 12b.

(Effects of the Invention According to this invention, the amount of light emitted by the light emitting element is controlled so that the amount of light received by the light receiving element is constant, and the constant value of the amount of light received by the light receiving element can be changed. , the linear relationship between the amount of light received by a part of the light-receiving area of the light-receiving element and the distance to the target object can be set to an arbitrary range, and the distance to the target object can be determined without the need for a complicated mechanism related to lens displacement. This has the advantage that the measurement range can be set arbitrarily.

[Brief explanation of the drawing]

FIG. 1 is an optical path diagram showing the effects of this invention. Second
This figure is a diagram showing the configuration of a distance measuring device according to an embodiment of the present invention, and FIG. 3 is a diagram showing the configuration of a distance measuring device according to another embodiment of the present invention. FIG. 4 is a diagram showing the relationship between ranging output and distance in the embodiment of the present invention. Further, FIG. 5 is a diagram showing the positional relationship between a light projecting element, a light receiving element, and a target object of a general distance measuring device including an embodiment of the present invention. 1-light emitting element, 2-light receiving element, 2a-2c-light receiving area, 6-light emitting control circuit, 10-reference voltage setting circuit.

Claims (1)

[Claims] (1) A light projecting element that projects light onto a target object, and a light projecting element that receives reflected light from the target object at a position a certain baseline length away from the light projecting element in a direction perpendicular to the light projection direction of the light projecting element. A triangular distance measuring device comprising a light receiving element that outputs a signal according to the amount of received light, the light receiving area of the light receiving element being divided into a plurality of parts in the base line length direction, a comparison means that uses the output of some of the light-receiving areas as a ranging output and compares the output sum of any light-receiving area or all of the light-receiving areas with a reference voltage; and a reference voltage setting means that arbitrarily sets the reference voltage; A distance measuring device comprising: a light projection control means for controlling the amount of light emitted by a light emitting element so that the comparison result of the means becomes a constant value.