JPH0420892A - Measuring of distance with laser - Google Patents

Abstract

PURPOSE:To measure distance correctly by putting a directional reflective body reflecting to the direction of incident on an object, radiating laser pulse to the object, and extracting only the object based on the distance obtained from the intensity and time delay of the coming back light. CONSTITUTION:A reflective body 1 is a reflecting body put on a object and it reflects laser light to the direction of incident. A laser generator 2 radiates laser scanning two dimensionally onto the reflective body put on the object based on the pulse signal put in from a pulse generator 2-1. A reflection light receiver 3 receives the laser pulse reflected back by the reflective object 1. A photo-electric converter 6 converts the pulse received by the receiver 3 to electric signals. A distance measuring part 7 calculates the time difference between the pulse generated by the generator 2-1 and the pulse after the photo-electric conversion by the converter 6 and measure the distance to the reflective body 1 put on the object. An object extracting part 9 refers to a table 4 of light intensity to distance relation based on the distance measured with the distance measuring part 7 and the light intensity measured with a light intensity measuring part 8 and extracts the object in the object existence region.

Description

[Detailed description of the invention] [Summary 2] Regarding the laser distance measurement method for measuring the distance to an object, a directional reflective object that reflects in the direction of incidence is added to the object, and a laser pulse is emitted to the object. returned light intensity,
The aim is to extract only the target object and accurately measure its distance by referring to a light intensity-distance relationship table created in advance based on the distance determined from the time delay and time delay. A light intensity distance relationship table created by pre-measuring the relationship between the light intensity and distance of the laser beam reflected back from an object to which a reflective object has been added, and the pulse of the laser emitted toward the object and the object. Based on the distance determined from the time difference between the pulse reflected by a reflective object attached to the object and the returned pulse, and the light intensity of the returned pulse, the distance within the object existence range is determined by referring to the light intensity distance relationship table above. The object distance measurement section extracts objects as objects, and is configured to output the distance of the object extracted by the object distance measurement section.

Further, among the objects extracted by the object distance measuring section, an object having a size within a certain range is determined as an object by two-dimensional scanning with a laser, and the distance thereof is output.

[Industrial application field]

The present invention relates to a laser distance measurement method for measuring the distance to an object. In autonomous vehicle driving systems, it is desired to automatically measure the distance to marks on the road (white lines, yellow-green lines, etc.) and marks attached to the front, rear, and sides of the vehicle.

[Conventional technology]

2. Description of the Related Art Conventionally, there is a device (laser radar) that irradiates a target object with laser light, receives the reflected light, and measures the distance to the reflective object. For example, you can calculate the distance by finding the phase difference between the amplitude modulated laser beam and the reflected light.
The distance is calculated by emitting a laser pulse and finding the time difference between the reflected pulse and the reflected pulse.

[Problem to be solved by the invention]

When measuring the distance to an object by irradiating the conventional laser described above, the object (reflecting object) has no directivity and the fifth
As shown in figure (A), when the angle of the reflecting surface to the incident light is 90°, the intensity of the reflected light is strong as shown on the right (
large amplitude). However, if the angle of the reflective surface is 90”,
As shown in FIG. 5(b), as the object shifts, the intensity of the reflected light becomes weaker as shown on the right, making it difficult to capture the object. Further, since reflected light also returns from unnecessary portions, there is a problem in that it is necessary to perform a process of deleting this unnecessary signal portion by some method after receiving the light.

In the present invention, a directional reflective object that reflects in the incident direction is added to the target object, and a laser pulse is emitted to the target object and a laser pulse is created in advance based on the intensity of the returned light and the distance determined from the time delay. The purpose is to extract only the target object and accurately measure its distance by referring to the light intensity distance relationship chifur.

[Means to solve problems]

FIG. 1 shows a block diagram of the principle of the present invention.

In FIG. 1, a laser emitting unit 2 emits laser pulses.

The reflected light receiver 3 receives laser pulses reflected and returned from the reflective object 1 attached to the object.

The light intensity distance relationship table 4 is a table created by measuring in advance the relationship between the light intensity of the laser pulse reflected and returned from the reflective object 1 attached to the target object and the distance.

The object distance measurement unit 5 calculates the distance calculated from the time difference between the laser pulse emitted towards the object and the pulse reflected by the reflective object 1 attached to the object and the returned pulse. Based on the light intensity, an object within the object existing range is extracted as an object by referring to the light intensity distance relationship table 4, and the distance to this object is measured.

[Function] As shown in the first leap, the laser emitting section 2 emits laser pulses toward the reflective object 1 added to the object, and the reflected light receiving section 3 collects the reflected light applied to the object. The laser pulse reflected from the object 1 is received, and the laser pulse emitted toward the object by the object distance measuring section 5 is reflected by the reflecting object 1 attached to the object and returned. Based on the distance calculated from the time difference between the pulse received by the reflected light receiver 3 and the pulse converted into an electric signal, and the light intensity of the returned pulse, the light intensity distance relation chifur 4 is referred to and the target object is within the existing range. The object is extracted as an object and its distance is output. In addition, the laser is scanned two-dimensionally to determine an object within a certain size range, and the distance to the object is output.

Therefore, a directional reflective object 1 that reflects in the incident direction is added to the target object, a laser pulse is emitted toward the reflective object 1 of the target, and the distance is determined from the intensity of the returned laser pulse and the time delay. By referring to the light intensity distance relationship table 4 created in advance based on By determining the distance to the target object, it becomes possible to extract only the target object and accurately measure its distance.

8 [Embodiment] Next, the configuration and operation of an embodiment of the present invention will be sequentially explained in detail using FIGS. 2 to 4.

In FIG. 2, a reflective object 1 is a reflective object added to an object, and when a laser beam is incident thereon, it is reflected in the direction of incidence. The reflective object 1 is a plate or tape coated with minute spherical glass balls called cat's eyes, for example.

The pulse generating section 2-1 generates a pulse signal for causing the laser emitting section 2 to emit laser pulses.

The laser emitting unit 2 emits laser pulses based on the pulse signal input from the pulse generating unit 2-1 toward the reflective object 1 added to the target object in a two-dimensional scanning manner. .

The reflected light receiver 3 receives the laser pulse reflected by the reflective object 1 and returned.

The photoelectric converter 6 converts the pulse received by the reflected light receiver 3 into an electrical signal.

The distance measuring section 7 calculates the time difference between the pulse generated by the pulse generating section 2-1 and the pulse after photoelectric conversion by the photoelectric conversion section 6, and measures the distance from this to the reflective object 1 added to the target object. It is something.

The light intensity measurement section 8 performs A/D conversion on the analog pulses that have been photoelectrically converted by the photoelectric conversion section 6, and measures the digital light intensity.

The object extracting section 9 refers to the light intensity distance relationship table 4 based on the distance measured by the distance measuring section 7 and the light intensity measured by the light intensity measuring section 8, and calculates the value shown in FIG. 4 (b), which will be described later. This is to extract objects existing within the object existence range as objects. The distance of this extracted object is the distance of the object to be sought. Furthermore, among the objects that have light intensity and distance that exist within this object existence range, the laser is further scanned two-dimensionally to determine the distance of objects that have a size within a certain range. .

FIG. 3 shows an explanatory diagram of the reflective object according to the present invention. This shows the directivity of the reflective object 1 added to the objects of FIGS. 1 and 2. Here, the reflective object 1 has a third Figure (a) When a laser pulse is incident obliquely as shown by the dotted line, the laser pulse is strongly reflected in the direction of incidence as shown by the arrow.

Therefore, as shown in FIG. 3(b), a strong pulse is received, and even if the reflecting object 1 is tilted, reflected light of approximately equal light intensity can be obtained.

Next, according to the order shown in the flowchart in Figure 4 (a),
The operation of the configuration shown in FIG. 2 will be explained in detail.

In Fig. 4 (a), ``■'' emits a laser. In this case, the laser emitting unit 2 in FIG. 2 emits a laser pulse toward a reflective object attached to the object.

■Receives laser light. The reflected light receiver 3 in FIG. 2 receives the laser pulse reflected from the reflective object 1 attached to the object and returned.

■Measure the light intensity. The light intensity measuring section 8 in FIG. 2 converts the laser pulse received by the reflected light receiving section 3 into an analog electrical signal at the photoelectric conversion section 6, and
It is measured as digital light intensity using a /D converter.

0 performs distance measurement based on pulse delay. This calculates the time difference between the pulse emitted by the second open circuit M measurement unit 7 and the pulse received, and measures the distance to the object.

[Phase] refers to the light intensity distance relationship table based on the light intensity, and extracts the phase within the object existing range. This is the fourth
With reference to the light intensity distance relationship table 4 shown in figure (b),
It is determined whether the distance measured in (2) corresponding to the light intensity measured in (2) is within the object existing range, and the object within this range is determined to be the object.

For [phase], an object of a certain size is determined as an object by two-dimensional scanning. In this case, among the objects that were determined to be within the object existence range by referring to the light intensity distance relationship table 4 in ①, the laser pulse is further scanned two-dimensionally to identify objects within a certain size range. I decide.

FIG. 4 (b) shows an example of a light intensity distance relationship table.

This is done by measuring in advance the relationship between the distance of the reflective object 1 added to the target object and the intensity of the reflected light and setting that relationship. The intensity of light reflected back from a directional reflective object 1 is approximately constant regardless of the angle at which the reflective object 1 is attached to the object (see Figure 3 (a)), so here When the light intensity is greater than a certain value at a certain distance, the object is considered to be within the existing range. In addition, the laser pulse emitted toward the reflective object 1 attached to the target object is scanned two-dimensionally, and when the size of the reflective object 1 is within a certain size range, it is determined to be the target object, and only the target object is detected. I try to extract it correctly and measure the distance.

[Effects of the Invention] As explained above, according to the present invention, a directional reflective object 1 that reflects in the incident direction is added to an object, a laser pulse is emitted toward the object, and the laser pulse that returns is By referring to the light intensity distance relationship table 4 created in advance based on the pulse intensity and time delay, only the objects within the object existence range are extracted and distances are determined, and the laser is further scanned two-dimensionally. Since the system uses a configuration that calculates the distance to objects that have a size range, it is possible to extract only the objects and accurately measure their distances.

[Brief explanation of drawings]

Figure 1 is a block diagram of the principle of the present invention, and Figure 2 is a block diagram of the principle of the present invention.
Embodiment configuration diagram, FIG. 3 is an explanatory diagram of a reflective object according to the present invention, FIG. 4 is a flowchart explaining the operation of the present invention, and FIG. 5 is an explanatory diagram of problems in the conventional technology. In the figure, 1 is a reflective object added to the target object, 2 is a laser emitting part, 3 is a reflected light receiving part, 4 is a light @ variable distance relationship table,
Reference numeral 5 represents an object distance measurement section, 6 represents a photoelectric conversion section, 7 represents a distance measurement section, 8 represents a light intensity measurement section, and 9 represents an object extraction section.

Claims (2)

[Claims] (1) In the laser distance measurement method that measures the distance to an object, the distance and the light intensity of the laser reflected back from the object with a directional reflective object (1) that reflects in the direction of incidence are calculated. A light intensity distance relationship table (4) created by measuring the relationship in advance, and a table showing the relationship between the laser pulse emitted toward the target object and the pulse reflected by the reflective object (1) attached to the target object. An object distance measurement unit (object distance measurement unit) that extracts objects within the object existence range as objects by referring to the light intensity distance relationship table (4) based on the distance calculated from the time difference and the light intensity of the returned pulse. 5), and is configured to output the distance of the object extracted by the object distance measuring section (5). (2) Among the objects extracted by the object distance measurement unit (5), the object is determined to be a target object by two-dimensional scanning with a laser, and the distance thereof is output. A laser distance measuring method according to claim (1), characterized in that: