CN114355373A

CN114355373A - Laser distance measuring device

Info

Publication number: CN114355373A
Application number: CN202210244585.6A
Authority: CN
Inventors: 宋小亮; 李杨
Original assignee: Chengdu Liangxin Integrated Technology Co ltd
Current assignee: Chengdu Liangxin Integrated Technology Co ltd
Priority date: 2022-03-14
Filing date: 2022-03-14
Publication date: 2022-04-15
Anticipated expiration: 2042-03-14
Also published as: CN114355373B

Abstract

A laser distance measuring device mainly comprises a laser, a transmitting lens, a receiving lens, a laser receiver and a reference light reflection/scattering passage. The principle is that a laser emits modulation pulses, most of measuring signal light is collimated by an emitting lens and then emitted to a measured object, and a receiving lens receives and focuses reflected/scattered light of the measured object on a laser receiver and then converts the light into a measuring electric signal A. A small part of reference signal light can be simultaneously irradiated on the laser receiver through the reference light back/scattering path and then converted into a reference electric signal B. The measuring electric signal A and the reference electric signal B contain the distance information of the object to be measured, and the distance of the object to be measured is obtained through the analysis of the A/B signals. The invention adopts the open reference light reflection/scattering channel with the different axes of the central optical axes of the transmitting lens and the receiving lens, the light energy of the measuring signal light and the reference signal light can simultaneously irradiate the laser receiver, the light path isolation and switching are not needed, the structure is simple and reliable, the speed measurement is fast, and the cost is low.

Description

Laser distance measuring device

Technical Field

The invention belongs to the field of photoelectric distance measurement, and relates to a laser distance measurement device.

Background

At present, two methods for realizing a phase type laser range finder mainly exist: continuous wave phase ranging, which is typically employed by Laika (LEICA), and pulse wave phase ranging, which is typically employed by lillti (HILTI) (patent application No. US 6917415B 2). The two technologies are identical in that both the technologies transmit laser with modulation information to an object to be measured, receive the reflected/scattered light of the object to be measured, and finally obtain the distance information of the object to be measured by the phase difference between the transmitted light and the received light.

As shown in fig. 1, continuous wave phase ranging requires two channels of same-frequency sinusoidal signals to be formed, and measures distance information of light propagation by using phase difference of the two channels of sinusoidal signals. Two sinusoidal signals, one from the outer optical path, usually called the measurement signal, and the other from the inner optical path or generated directly by the internal correlation circuit, usually called the reference signal. The distance information is determined from the phase difference between the measurement signal and the reference signal. The generation of the reference signal may occur using circuit signals rather than having to use an internal optical path. For example, using a circuit mixer to generate a phase waveform for the reference path or directly generating a trigger signal that characterizes the start of the phase reduces the complexity of the optical path, but must ensure that the only path traveled by the external optical path, no additional anti-scatter path, or otherwise, an accurate measurement signal is not formed, as shown in fig. 5.

In the ranging process adopting the continuous wave phase method, a signal processor needs to sample a measurement signal and a reference signal, the measurement signal channel and the reference signal channel are required to be independent from each other or have precedence in sampling time, otherwise, two same-frequency signals can be mixed, phase difference information cannot be extracted, and therefore distance information cannot be calculated. The implementation manner may adopt two independent signal channels or a time-sharing switching signal channel, which specifically includes: two or more transmitters, two or more receivers, one transmitter and one receiver, and the addition of a channel switching device. Specifically, the following description is provided: the reference signal of the continuous wave phase distance measuring scheme of a transmitter and a receiver can be generated by channel switching in the modes of an electromagnetic physical switch or a liquid crystal light valve and the like, or can be directly generated by a related mixing circuit or a single-pole double-throw switch.

The basic principle of the pulse wave ranging technology is to divide the laser emitted by the pulse into two parts at the same time, which are used for generating a measuring signal and a reference signal (see fig. 2), respectively, and because the transmitting and receiving laser pulse has a fixed frequency difference, a double peak signal related to the phase of the transmitting and receiving signal is formed on the receiving wave, wherein one peak value is the measuring signal, and the other peak value is the reference signal. The distance between the two peak values is related to the optical path difference of the pulse laser propagating in the optical path, so that the distance of the measured object is obtained.

During the measurement, only one pulse sequence has to be transmitted to form an echo with a measurement signal peak and a reference signal peak. The pulsed laser used to generate the measurement and reference signals must be homologous to ensure measurement accuracy, and cannot be isolated on the optical and electrical paths, or otherwise a bimodal signal cannot be formed.

Continuous wave phase ranging requires that a measurement signal optical path and a reference signal optical path must be isolated or switched in a time-sharing manner; pulse wave phase ranging requires that the measurement signal path and the reference signal path cannot be isolated.

In view of the requirement of pulse wave phase ranging, the HILTI (HILTI) proposed a method of ranging with coaxial transmitting and receiving optical axes (patent application No. 201210157923.9 fig. 3), in which the reference optical path is scattered to the detector by a scattering structure near the mirror, but this method results in a loss of part of the transmitted optical power due to the common mirror for transmitting and receiving, and thus weakens the ranging capability. Meanwhile, coulter, giger, germany, also proposed a reference optical path scheme (patent application No. CN01814664.3, publication No. CN1449501A, fig. 4) with separate transmitting and receiving optical axes (paraxial), which realizes generation of reference signals by a mirror and a laser receiver, and performs time-sharing switching on the reference signal and measurement signal paths by using a switch to achieve the purpose of isolating the reference signals and the measurement signals. Due to the consistency problem of the two laser receivers, the distance measurement precision is poor, the production yield is low, and the production cost is high.

Disclosure of Invention

The invention aims to provide a laser ranging technology, which improves the precision, speed and range of laser ranging by simultaneously receiving a pulse reference signal sent by a laser and a pulse measurement signal reflected/scattered by a measured object through a laser receiver. In the structure of the distance measuring device, the simultaneous receiving of the reference signal light and the measurement signal light is realized, and the non-coaxial central optical axes of the transmitting lens and the receiving lens are also met.

In order to achieve the purpose, the invention provides the following technical scheme:

a laser distance measuring device is characterized by comprising a device body, a laser, a transmitting lens, a receiving lens, a laser receiver and a reference light back/scattering passage; the device main body is composed of a sending cavity, a receiving cavity and a cavity isolation belt, wherein a transmitting lens and a receiving lens are respectively positioned at the front parts of the sending cavity and the receiving cavity, a laser and a laser receiver are respectively positioned at the rear parts of the sending cavity and the receiving cavity, a reference light back/scattering path is positioned at the cavity isolation belt, the laser emits modulation pulses, most of light in the modulation pulses is projected to a measured object after being collimated by the transmitting lens, the receiving lens converges the light reflected by the measured object and irradiates the laser receiver, and the small part of light in the modulation pulses directly irradiates the laser receiver through the reference light back/scattering path.

Further, the reference light reflection/scattering path is composed of a reflection/scattering device, a light guide/hole or an open scattering structure.

Furthermore, the laser ranging device is provided with only one laser and one laser receiver, and the central optical axes of the transmitting lens and the receiving lens are not coaxial.

Further, the laser and the laser receiver form a conjugate imaging relationship through the diffuser, so that part of the light emitted by the laser is received by the laser receiver after passing through the diffuser and forms a pulse reference signal.

Further, the anti/diffuser is located between, on or outside the emission lens and the reception lens.

Further, the anti/diffuser may be composed of a single sheet, two sheets, or multiple sheets of reflectors, as in example 5.

Further, the laser ranging device completely removes the isolation between the transmitting part and the receiving part, and the laser detector receives a small amount of internal stray light or diffuse reflection light to complete the reception of the pulse reference signal, as in embodiment 4.

In summary, the invention adopts a laser and a laser receiver, and the transmitting and receiving central optical axes are not coaxial, so the invention has the following obvious advantages:

1. compared with the continuous wave phase measurement scheme, the pulse wave phase measurement has the characteristics of long measurement distance, high measurement speed and high measurement precision.

2. Compared with the coaxial pulse wave phase measurement scheme, the paraxial pulse wave phase measurement scheme has the advantages of less energy loss, simple and efficient production and lower cost.

3. Compared with a pulse wave phase measurement scheme of one laser transmitter and two laser receivers, the pulse wave phase measurement method has the advantages that the transmitting and receiving are homologous, and the consistency of the performance of devices and systems is guaranteed, so that the measurement precision is guaranteed, the complexity of the system is reduced, the power consumption is reduced, and the size is reduced.

Drawings

Fig. 1 is a schematic diagram of a continuous wave phase ranging signal.

Fig. 2 is a schematic diagram of a pulse wave phase ranging signal.

Fig. 3 is a diagram of a coaxial pulse wave phase ranging scheme.

Fig. 4 is a schematic diagram of paraxial pulse wave phase ranging (dual laser receiver scheme).

FIG. 5 is a schematic diagram of a continuous wave phase ranging apparatus.

FIG. 6 is a schematic view of a distance measuring device according to the present invention.

Fig. 7 is a schematic view of a distance measuring device according to embodiment 2 of the present invention.

Fig. 8 is a schematic view of a distance measuring device according to embodiment 3 of the present invention.

Fig. 9 is a schematic view of a distance measuring device according to embodiment 4 of the present invention.

Fig. 10 is a schematic view of a distance measuring device according to embodiment 5 of the present invention.

Detailed Description

Example 1

As shown in fig. 6, a laser ranging apparatus is characterized by comprising an apparatus body, a laser 1, a transmitting lens 2, a receiving lens 3, a laser receiver 4, and a reference light back/scattering path. The device main body is composed of a sending cavity 9, a receiving cavity 10 and a cavity isolation belt 8. The transmitting lens 2 and the receiving lens 3 are respectively positioned in front of the transmitting cavity 9 and the receiving cavity 10, the laser 1 and the laser receiver 4 are respectively positioned in rear of the transmitting cavity 9 and the receiving cavity 10, the reference light back/scattering path is positioned in the cavity isolation strip 8, the laser 1 transmits modulation pulses, most of light in the modulation pulses is collimated by the transmitting lens 2 and then projected to a measured object, the receiving lens 3 converges light reflected by the measured object and then irradiates the laser receiver 4, and the small part of light in the modulation pulses directly irradiates the laser receiver 4 through the reference light back/scattering path. The reference light anti/scattering path in this embodiment is an anti/scatterer 5 located in the cavity isolation strip 8. The laser emitted by the laser 1 can collimate and emit main energy to an object to be measured through the emitting lens 2 due to a large divergence angle of the laser, and after being reflected/scattered by the object, the reflected/scattered light is focused on the laser receiver 4 by the receiving lens 3. At the same time, a small portion of the light beyond the transmitting lens is directed onto the laser receiver 4 via the anti/diffuser 5, so that a simultaneous reception of the reference signal and the measuring signal is formed at the laser receiver 4.

The laser 1 is located at the focal position of the emitting lens 2. The laser receiver 4 is located at the focal position of the receiving lens 3. The anti/diffuser 5 is located between or on the transmitting lens 2 and the receiving lens 3.

The curvature and position of the anti/diffuser 5 satisfy that the laser 1 and the receiving chip 4 form a conjugate imaging relationship.

Example 2

As shown in fig. 7, the present embodiment is similar to embodiment 1 except that the anti/diffuser 5 is adjusted to the outside of the emission lens 2 and the reception lens 3 from the position between or above the emission lens 2 and the reception lens 3.

Example 3

As shown in fig. 8, this embodiment is similar to embodiment 1, except that the reference light anti/diffuser is implemented by a light guide/aperture 5' and the reference signal is transmitted by the laser 1 to the laser receiver 4.

Example 4

As shown in fig. 9, the present embodiment completely removes the isolation between the transmitting and receiving portions, and the laser receiver 4 receives a small amount of stray light to complete the reception of the reference signal.

Example 5

As shown in fig. 10, the present embodiment achieves the acquisition of the reference signal by adding one or more back/scattering mirrors. After passing through the transmitting lens 2, a part of laser emitted by the laser 1 enters the laser receiver 4 through at least one reflector 6 and a reflector 7, and the reception of the reference signal is completed.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A laser distance measuring device is characterized by comprising a device body, a laser (1), an emitting lens (2), a receiving lens (3), a laser receiver (4) and a reference light back/scattering path, wherein the device body is composed of a sending cavity (9), a receiving cavity (10) and a cavity isolation belt (8), the emitting lens (2) and the receiving lens (3) are respectively positioned at the front parts of the sending cavity (9) and the receiving cavity (10), the laser (1) and the laser receiver (4) are respectively positioned at the rear parts of the sending cavity (9) and the receiving cavity (10), the reference light back/scattering path is positioned at the cavity isolation belt (8), the laser (1) emits modulation pulses, most of light in the modulation pulses is collimated by the emitting lens (2) and then projected to a measured object, the receiving lens (3) converges light reflected by the measured object and then irradiates the laser receiver (4), a small part of light in the modulated pulse directly irradiates a laser receiver (4) through a reference light back/scattering path.

2. A laser rangefinder apparatus according to claim 1, wherein said reference light anti/scattering path is comprised of an anti/diffuser (5), a light guide/aperture (5') or an open scattering structure.

3. A laser rangefinder apparatus according to claim 2, characterized in that the light guide/hole (5') consists of a light guide or hole through the separating belt between the receiving and transmitting parts, and the laser receiver (4) receives a small amount of light guided by the light guide/hole to complete the reception of the reference signal light.

4. A laser ranging device as claimed in claim 2, characterized in that said open scattering structure, the transmitting and receiving parts are completely free of isolation structures, and the laser receiver (4) receives only a small amount of internal stray light or diffuse reflected light to complete the reception of the reference signal light.

5. A laser rangefinder apparatus according to claim 1, characterized in that it has only one laser (1) and one laser receiver (4), and the central optical axes of the transmitting lens (2) and the receiving lens (3) are not coaxial.

6. A laser rangefinder apparatus according to claim 2, characterized in that when an anti/diffuser (5) is used in the reference light anti/diffuser path, the laser (1) and the laser receiver (4) are brought into a conjugate imaging relationship by means of the anti/diffuser (5), so that part of the light emitted by the laser (1) is received by the laser receiver (4) after passing through the anti/diffuser (5) and forms a pulsed reference signal.

7. A laser distance measuring device according to claim 6, characterized in that the anti/diffuser (5) is positioned between, on or outside the transmitting lens (2) and the receiving lens (3).

8. A laser ranging device as claimed in claim 6, characterized in that the reference signal anti/scatterer (5) consists of a single piece, two pieces or a plurality of pieces of reflectors.