KR19980077355A - Distance measuring method - Google Patents

Abstract

The present invention relates to a distance measuring method for calculating a distance by calculating a time required to return after light is emitted toward a measurement object. The present invention relates to a photodetector output signal having a level set from a point at which a driving signal indicating light output of a light source is generated. The stored delay time is subtracted from the time counted up to the generator's starting point, and the calculated flight time is calculated by subtracting the compensation time corresponding to the output peak of the photodetector from the stored table table, and multiplying the total luminous time by the luminous flux. And divide this value into the measured distance. Here, the delay time corresponds to the response delay time between the driving signal generation time and the actual light output of the light source. The delay time is a fixed value according to the application system, and the compensation time indicates the light distribution of light incident on the photodetector according to the distance. Normalized from the highest value of the detector's electrical signal level.

Description

Distance measuring method

The present invention relates to a distance measuring method for calculating a distance by calculating a time required to return after light is emitted toward a measurement object, and specifically, a measurement accuracy by compensating a measurement error component generated when the required time is measured. Relates to a distance measuring method.

The distance measuring device is used alone or applied as a component of a system for using the measured distance value in other control functions.

For example, in an anti-collision system that controls a collision of a vehicle, a distance measuring device is applied to measure a distance between vehicles, and is applied to shape recognition of an object in a robot system.

As a general distance measuring method, the electromagnetic wave such as laser, microwave, or millimeter wave is fired to reflect the time difference from the measurement object to the reception, and then the light flux is multiplied by the calculated time difference. There is a distance measuring method that converts.

In the conventional distance measuring device, the light travel time is calculated from the time point at which the driving signal for light output is generated to the light source and the time point at which the electric signal of a predetermined level is input from the light detector.

However, in the conventional distance calculation, the error component corresponding to the delay time from the time when the driving signal is generated to the time when the light source responds substantially emits light is included in the calculated distance. In addition, an increase in the reciprocating distance of the light emitted from the light source leads to attenuation of the incident light amount of the photodetector. Conventionally, the output of the photodetector in which the count completion point is not buffered calculated in response to the light attenuation, and the completion of the flight time count is set. By collectively performing at the level, an error between the calculated distance and the measured distance occurred.

SUMMARY OF THE INVENTION The present invention has been made to improve the above problems, and more particularly, the object of the present invention is to provide a distance measuring method which improves distance measurement accuracy by compensating for an error component included in calculating a light travel time by measurement.

1 is a block diagram showing a distance measuring device for explaining the distance measuring method according to the present invention.

FIG. 2 is a timing chart showing an output waveform of each element of the distance measuring device of FIG. 1. FIG.

FIG. 3 is a view illustrating a change in output signal waveform of the photodetector of FIG. 1 with time; FIG.

Explanation of symbols for main parts of the drawings

11: light source 12: measurement operation unit

13: photodetector 14: measuring object

In order to achieve the above object, the distance measuring method according to the present invention includes a light source and a photodetector, and after calculating the time from the light emitted from the light source to the light detector after the light is reflected from the measurement object, the measurement object A method for calculating the distance from the light source, wherein the measurement operation unit calculates a first time from the time of light emission of the light source to the time of occurrence of a predetermined level of electrical output signal from the light detector, and monitors the electric signal level of the light detector. While calculating the electrical signal value at which the electrical signal level of the photodetector reaches the highest value, and the light amount distribution incident on the photodetector according to the distance is normalized from the highest value of the electrical signal level of the photodetector. The compensation time corresponding to the electrical signal value is extracted from the table and the first After multiplying the luminous flux by the sum of the compensation time and the time, it is characterized in that it is divided into two to calculate the distance.

The first time is substantially measured by the light source at the estimated time counted from the time when the measurement operation unit instructs the light emission of the light source to the time when the electric output signal is generated from the photodetector. Calculated by subtracting the delay time until the light is emitted.

Hereinafter, a distance measuring method according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a distance measuring system for explaining the distance measuring method according to the present invention.

Referring to this, the light source 11 is controlled by the measurement operator 12 to emit light, and the photodetector 13 measures the electrical signal corresponding to the light received through the measurement object 14. To be supplied to

Here, the measurement operation unit 12 calculates the distance by determining the driving of the laser light source 11 and the electrical signal input from the photodetector 13.

2 is a timing chart showing an output waveform of each element of the distance measuring system of FIG.

Referring to this, the delay time Td until the light source 11 responds to the light output substantially after the pulse signal corresponding to the driving signal instructing the light output from the measurement operator 12 is output. ) Is generated. In the present invention, this delay time Td is computed so as to fall out of the calculation of the flight time corresponding to the actual optical travel time. Although the generation of the delay time Td is related to the circuit configuration and the response characteristics of the light source 11, the occurrence of the delay time Td is constant every time in the measurement system in which each component and the circuit configuration are completed. Therefore, in the present embodiment, the delay time Td is measured in advance and stored in the measurement calculation unit 12, and then the output signal generation point Tf of the photodetector having the set level from the pulse signal generation point Ts corresponding to the drive signal is generated. The first time T is calculated by subtracting the stored delay time Td from the counted time.

In addition, since the first time T is constantly completed and calculated at the set output level Vth of the photodetector 13, the compensation time ΔT for the accurate count completion time is separately calculated in response to the incident light quantity variation. Thus, the flight time of the actual light is calculated by adding or subtracting the first time T.

The light intensity distribution incident on the photodetector 13 has a Gaussian shape corresponding to the light emission waveform of the pulsed light source 11, and even though the laser has excellent linearity, some of the emitted light spreads at a predetermined angle with respect to the optical axis. Since the divergence increases, the amount of light incident on the photodetector 13 is attenuated as the traveling distance increases. As a result of the attenuation of light, the output signal of the photodetector 13 corresponding to the set level is delayed.

Therefore, in the present invention, the compensation of the amount of light incident on the photodetector 13 according to the distance is compensated by calculating the compensation time ΔT corresponding to the actual flight time completion point from the highest value of the electrical signal output from the photodetector.

This will be described in detail with reference to FIG. 3, which shows a change in output signal waveform of the photodetector of FIG. 1 with time.

In the figure, a is a standard waveform serving as a compensation reference, and b and c are modeled waveforms when the amount of light is increased or attenuated relative to the standard waveform. The electrical signal output here corresponds to a voltage signal.

The standard waveform (a) shows the output voltage waveform when the emitted light is normally incident on the photodetector 13 without being subjected to external factors, and the curves b and c indicated by dotted lines indicate external influences or beam divergence. The output voltage waveform of the photodetector 13 modified by the above is shown. When the output value is the standard waveform (a), the count of the first time T ends at T2 corresponding to the set level (Vth). However, in the case of the curve b, the increase in incident light intensity increases and is substantially larger than the T2 starting point. Since the count of the first time Tb in the previous T1 is terminated, the corresponding compensation time, that is, the compensation time ΔT1 corresponding to the difference between T2 and T1, should be added to the calculated first time Tb. Similarly, in the case of the curve c, since the count of the first time Tc is terminated at T3 after the incident light intensity increase rate is attenuated from the standard curve a and is substantially later than the T2 starting point, the corresponding compensation time, that is, T3 The compensation time ΔT3 corresponding to the difference between and T2 should be subtracted from the calculated first time Tc.

In the present invention, the compensation time calculation is calculated from the curve corresponding to the highest voltage Vpn in each modeled output waveform curve. The calculation of the compensation time [Delta] T from the highest voltage Vpn can be calculated in advance from each of the modeled curves and the standard curve a. Therefore, if only the peak value Vpn is known, the corresponding compensation time [Delta] T is automatically determined.

That is, through the table, when the highest voltage is relatively higher than the standard maximum voltage, for example, when the peak voltage (Vp ₁ ) of the b curve is high, the compensation time becomes + ΔT1 and the peak voltage (Vp3) corresponding to the c curve. The compensation value is -ΔT2. In the table, the compensation time corresponding to the highest voltage Vpn is calculated by curve modeling in the unit of calculation of the detection voltage and stored in the measurement calculation section 12 in advance.

As a result, the delay time Td stored in the measurement time from the drive signal generation point Ts to the set output level Vth of the photodetector 13 is subtracted, and the first time T is calculated. The value obtained by adding or subtracting the compensation time ΔT from the highest voltage Vpn of the photodetector 13 to the first time T is the total flight time T + ΔT.

Then, when the speed of light is multiplied by this moving time, that is, the flight time, the distance is two minutes.

As described above, by providing the distance measuring method according to the present invention, the measurement error at the time measurement is compensated, thereby making more accurate distance measurement.

Claims (5)

In the method comprising a light source and a photodetector, to calculate the time from the light emitted from the light source to the photodetector after reflecting from the measurement object to calculate the distance to the measurement object, The measurement operation unit calculates a first time from the time of light emission of the light source to the time of occurrence of a predetermined level of electrical output signal from the photodetector, and monitors the electrical signal level of the photodetector while the electrical signal level of the photodetector is highest. The compensation time corresponding to the calculated electrical signal value is calculated by referring to a table table in which the calculated electrical signal value is normalized and the light distribution distribution incident on the photodetector according to the distance is normalized from the highest value of the electrical signal level of the photodetector. A distance measuring method, characterized in that it is taken out from the table and multiplied by the luminous flux at a time obtained by adding the compensation time to the first time, and calculating the distance by dividing the light beam. The method of claim 1, wherein the first calculation time is calculated by starting the time count from the point at which the driving signal indicating light emission of the light source is generated, and counting the time until the point at which the electrical output signal is generated from the photodetector. And subtracting a delay time from when the driving signal is generated until the light is substantially emitted from the light source. 3. The distance measuring method according to claim 2, wherein the delay time is stored in advance in the measurement calculating section in accordance with a light source and a distance measuring device employing the driving circuit thereof without any measuring means. The distance measuring method according to claim 1, wherein the table table is stored in a memory device provided in the measurement calculation unit. The method of claim 1, wherein the light source is a laser light source.