JPS5979805A - Distance sensor - Google Patents

Abstract

PURPOSE:To measure distance at a high accuracy by computing distance with a distance computing means based on the radius of a spot light calculated with a means of calculating the radius of spot light from two output signals of a one- dimensional type semiconductor detector. CONSTITUTION:A light emitting element 7 is arranged on the optical axis of a projection/condenser lens 9 and irradiates a parallel spot light on the surface of an object on the opposite side of the lens 9 along the optical axis. A one-dimensional type semiconductor position detector 8 has the element 7 fuxed on one end of a light receiving surface and receives reflected lights from the surface of the object with the light receiving surface facing the lens 9 perpendicular to the optical axis. Based on first and second output signals of the one-dimensional type semiconductor position detector 8, the radius of the spot light is calculated with a means of calculating the radius of spot light and based on the radius value, the computation by the equation I is performed by a means 12 of computing distance. In the formula, L: distance from the center of the projection/condense lens 9 to the object 10, f: focal length of the lens 9; R: the radius of the lens 9; A: distance from the center of the lens 9 to the one-dimensional type semiconductor position detector 8; and r: the radius of spot light.

Description

[Detailed description of the invention] This invention relates to a single distance sensor.

The conventional distance sensor is 1. As shown in Figure 1, a light-emitting element 1 such as a semiconductor laser and a light-receiving element 2 are brought close to each other and integrated, and the light-emitting element 1 and light-receiving element 2 are used for emitting and transmitting light.
It is positioned on the optical axis of the condensing lens 3, and the parallel spot light from the light emitting element 1 is irradiated onto the surface of the object 4 through the projection/condensing lens 3, and the reflected light from the surface of the object 4 is projected/condensed. The light is received by the light receiving element 2 through the photonic lens 3, and the light receiving element 2
The received light signal V is amplified by the received light signal amplifier 5 and the correction circuit 6
A distance signal is obtained by adding the

In such a distance sensor, the light reception signal V becomes maximum when the reflected light from the object 4 focuses on the light receiving element 2, and as the position of the object 4 changes, the focus of the reflected light changes to either the front or back of the light receiving element 2. Even if the target 4 moves to the position X, the light receiving signal V decreases because the size of the light receiving element 2 is limited, and the position X of the object 4 and the light receiving signal V change as shown in FIG. Become.

To measure the distance to the target 4 using the distance sensor, light is irradiated from the light emitting element 1 to a reference plane 4' at a certain distance (one end of the measurement range) from the center of the light projecting/condensing lens 3. The reflected light from 4' (solid arrow) is received by the light receiving element 2,
By slightly moving the light-emitting element 1 and the light-receiving element 2 back and forth on the optical axis of the light emitting/condensing lens 3, the position where the received light signal V is maximized (the focus of the reflected light) is found, and the light-emitting element 1 and the light-receiving element are Move the element 2 a predetermined amount (1
ΔX: The light reception signal V at the measurement origin (a point at a constant distance from the reference plane) xo after moving by ΔX indicates the measurement range. This received light signal V. is input to the correction circuit 6 via the light receiving signal amplifier 5 to obtain the offset gain, the target 4 is irradiated with light from the light emitting element 1, and the reflected light (
(dashed line arrow) is the measurement origin X.

A light reception signal V is obtained from the light receiving element 2 at . and the light reception signal V. I try to find the difference between the two.

However, since such a distance sensor determines the change in distance to the object 4 based on changes in the amount of light, the amount of reflected light from the object 4 must always be constant, and it cannot be measured if the amount of reflected light changes. Ta.

In addition, measurement accuracy was low because it was affected by the amount of reflected light.

Therefore, an object of the present invention is to provide a distance sensor that can accurately measure distance even if the amount of reflected light from an object changes.

An embodiment of the present invention will be described based on FIGS. 3 to 5. As shown in FIG. 3, this distance sensor has a light emitting element 7 such as a semiconductor laser directed in the same direction at one longitudinal end of a -dimensional semiconductor device detector (51352: manufactured by Hamamatsu Television Co., Ltd.) 8. The light emitting element 7 is arranged on the optical axis of the light emitting/condensing lens 9, and the one-dimensional semiconductor device detector 8 is arranged so that the light receiving surface is directly aligned with the optical axis. Parallel spot light is irradiated onto the surface of the object 100 through the projection/condensing lens 9, and the reflected light from the surface of the object 10 is received by the one-dimensional semiconductor device detector 8 through the projection/condensing lens 9. - The diameter of the spot light irradiated onto the light receiving surface of the one-dimensional semiconductor device detector 8 by adding the first output signal and the second output signal of the one-dimensional semiconductor device detector 8 to the arithmetic circuit 11 and performing calculations. A spot barycenter position signal indicating the barycenter position in a direction is obtained, a radius of the spot light is determined based on the spot barycenter position signal in a distance calculation circuit 12, and a distance signal is obtained by further performing geometric calculations. There is.

Specifically, as shown in FIG. 4, the arithmetic circuit 11 inputs the first output signal and the second output signal (current signal) of the -dimensional semiconductor device detector 8 to an operational amplifier OP.

Convert the voltage with OF2 to obtain the output I-e I2, and add the output I-e I2 to the analog adder to get the output I-e + I2.
At the same time, the output ■0. I2 is subtracted by an analog subtracter G, and the subtraction power I+12 is extracted as an addition signal P, and
I'm taking it out right.

The distance calculation circuit 12 calculates the radius r of the spot light based on the spot gravity center position signal P from the calculation circuit 11. If the center of gravity of the spot light is known, the radius of the spot light can be easily determined using a table. That is, the light intensity of the spot light in the radial direction has a Gaussian distribution, for example, as shown in FIG. If ' is known, the radius r can be easily determined.

The center of the light projecting/condensing lens 9 and the object 1 based on the radius r
The calculation for determining the distance rs and L to 0 is as follows. That is, the radius r of the spot light at the location where the -dimensional type semiconductor device detector 8 is placed, the radius R of the light projecting/condensing lens, and the one-dimensional semiconductor device from the center of the light projecting/condensing lens 9. When data on the distance 1111A to the detector 8 is given, the distance a between the focal point of the reflected light by the projecting/condensing lens 9 and the center of the projecting/condensing lens 9 is determined by A-r. Therefore, the object 10 and the light projecting/condensing lens 9
The distance from the center to the center is given by (2+r), where f is the focal length of the light projecting/condensing lens 9. Here, C and C2 are constants given by the measurement system.

In such a distance sensor, when the reflected light from the target 10 is focused on the one-dimensional semiconductor device detector 8, the radius r of the spot light becomes the minimum, and the focus of the reflected light is focused on the one-dimensional semiconductor device detector 8. The radius of the spot light increases regardless of whether it moves around 80 or above.

Therefore, to measure the distance to the target 10 using the distance sensor, light is emitted from the light emitting element 7 from the center of the light projecting/condensing lens 9 to the reference surface 10', and the reflected light from the reference surface 10' (solid line arrow ) is received by the -dimensional type semiconductor device detector 8, and by slightly moving the light emitting element 7 and the one-dimensional type semiconductor device detector 8 back and forth above the light of the light emitting/condensing lens 9, one word P is added. Find a point (focal point of reflected light) where The distance MA from the center of the light emitting/condensing lens 9 to the one-dimensional semiconductor device detector 8 at this point is determined by moving the object 10 irradiate light from the light emitting element 7 to
The reflected light (broken line arrow) is irradiated onto the -dimensional semiconductor device and the detector 8, and the first output signal and the second output signal of the -dimensional semiconductor device detector 8 are processed to produce a syspot light. Find the center of gravity position P' of the light source, find the radius r of the spot light based on this, and perform the above-mentioned geometric alternating layer calculation.
L can be found.

In this way, since this example calculates the distance F@L geometrically, it is not affected by changes in the reflectance of the target 100, and is simple, non-contact, highly accurate, and fast. Distance measurements can be made.

As described above, the distance sensor of the present invention includes a light projecting and condensing lens, and a parallel spot light that is installed on the optical axis of the light projecting and condensing lens and is directed along the optical axis of the light projecting and condensing lens. A light emitting element that irradiates the surface of the object on the other side of the optical lens, and a light emitting element that is fixed to one end of a light receiving surface so that the light receiving surface is orthogonal to the optical axis and faces the light projecting/condensing lens, and a one-dimensional semiconductor device detector that receives reflected light from the surface of the semiconductor device; a first output signal of the one-dimensional semiconductor device detector;
It is equipped with a spot light radius calculation means for calculating the radius of the spotlight based on the output signal, and a distance calculation means for performing a predetermined calculation based on the radius of the spot light calculated by the spot light radius calculation means. Therefore, there is an effect that distance measurement can be performed with high accuracy without being affected by changes in the reflectance of the target.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional distance sensor, Fig. 2 is a characteristic diagram of the target position and light receiving element output, Fig. 3 is a block diagram of an embodiment of the present invention, and Fig. 4 is its main part. A detailed block diagram of FIG. 5 is an explanatory diagram of its operation. 7... Light emitting element, 8... -dimensional semiconductor device detector, 9... Light projecting/condensing lens, 10... Target, 11.
...Arithmetic circuit, 12...Distance calculation circuit

Claims (1)

[Claims] A light projecting and condensing lens, which is arranged on the optical axis of the light projecting and condensing lens, and parallel spot light is directed along the optical axis of the light projecting and condensing lens.
A light emitting element that irradiates the surface of the object on the other side of the condensing lens, and this light emitting element is fixed to one end of a light receiving surface, so that the light receiving surface is orthogonal to the optical axis and faces the light emitting/condensing lens. a one-dimensional semiconductor device detector that receives reflected light from the surface of the object; and a spot that calculates the radius of the spot light based on a first output signal and a second output signal of the -dimensional semiconductor device detector. A distance sensor comprising a light radius calculation means and a distance calculation means for calculating the following formula based on the radius of the spot light calculated by the spot light radius calculation means. Distance f between the center of the light lens and the object: Focal length R of the light projecting/condensing lens: Radius of the light projecting/condensing lens A: From the center of the light projecting/single light lens to the one-dimensional semiconductor device detector distance r: radius of spot light