CN109917415B - Laser range finder - Google Patents
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- CN109917415B CN109917415B CN201910323720.4A CN201910323720A CN109917415B CN 109917415 B CN109917415 B CN 109917415B CN 201910323720 A CN201910323720 A CN 201910323720A CN 109917415 B CN109917415 B CN 109917415B
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Abstract
The application relates to the technical field of distance measurement, and provides a laser distance meter. The phase-locked circuit in the range finder is respectively connected with the clock pin of the controller, the emission driving circuit and the local oscillation processing circuit and is used for providing clock signals; the emission driving circuit is also connected with the first emission tube and the second emission tube respectively and is used for driving the first emission tube to emit an external light path signal and driving the second emission tube to emit an internal light path signal; the local oscillation processing circuit is also connected with the laser receiving device and is used for outputting local oscillation signals to the laser receiving device; the laser receiving device is also connected with a first analog-to-digital conversion pin of the controller and is used for mixing an inner light path signal with a local oscillation signal and outputting the mixed inner light path signal to the controller, and mixing an outer light path signal reflected by a measured object with the local oscillation signal and outputting the mixed outer light path signal to the controller so that the controller can calculate the distance to be measured. The luminous intensity of the light-emitting diode adopted by the second transmitting tube is little affected by temperature, so that the distance measurement precision is improved.
Description
Technical Field
The application relates to the technical field of distance measurement, in particular to a laser distance meter.
Background
A laser rangefinder is a device that measures the distance of a target using a laser. At present, laser phase ranging is generally adopted by a laser range finder, and the light path measured by the laser range finder is mainly divided into four modes: single-shot, single-shot double-shot, double-shot single-shot and double-shot.
The dual-emission single-receiving mode generally adopts two laser diodes to emit laser signals, one of the two laser diodes is an outer light path signal, the other one of the two laser diodes is an inner light path signal, the outer light path signal is received by a laser receiving device after being reflected by a measured object, the inner light path signal is directly received by the laser receiving device after being transmitted by a preset light path in a laser range finder, and in the laser receiving device, the outer light path signal and the inner light path signal are mixed with local oscillation signals respectively. When the characteristics of the two laser diodes are consistent, the phase change amounts of the inner and outer light paths are approximately equal and can cancel each other, so that the phase difference of the inner and outer light paths is kept unchanged, and the distance from the laser range finder to the measured object can be calculated according to the mixed signals.
In practice, the light emission intensity of the laser diode is affected by temperature, and it is difficult to always keep the temperatures of the two laser diodes consistent, which eventually results in a decrease in the accuracy of the distance calculated according to the above-described distance measurement principle.
Disclosure of Invention
In view of the above, the embodiment of the application provides a laser range finder, which utilizes a light emitting diode to emit an internal light path signal, and the light emitting intensity of the light emitting diode is less affected by temperature, so that the range finding accuracy can be improved.
In order to achieve the above purpose, the present application provides the following technical solutions:
the embodiment of the application provides a laser range finder, which comprises: the device comprises a controller, a phase-locked circuit, a transmitting driving circuit, a first transmitting tube, a second transmitting tube, a local oscillation processing circuit and a laser receiving device, wherein the first transmitting tube is a laser diode or a light emitting diode, and the second transmitting tube is a light emitting diode; the phase-locked circuit is respectively connected with the clock pin of the controller, the emission driving circuit and the local oscillation processing circuit and is used for outputting a synchronous clock signal to the controller, outputting a driving clock signal to the emission driving circuit and outputting a local oscillation clock signal to the local oscillation processing circuit; the emission driving circuit is also connected with the first emission tube and the second emission tube respectively and is used for driving the first emission tube to emit an external light path signal and driving the second emission tube to emit an internal light path signal; the local oscillation processing circuit is also connected with the laser receiving device and is used for outputting local oscillation signals to the laser receiving device; the laser receiving device is also connected with a first analog-to-digital conversion pin of the controller and is used for mixing the received internal optical path signal with the local oscillation signal and outputting the mixed internal optical path signal to the controller, and mixing the received external optical path signal reflected by the measured object with the local oscillation signal and outputting the mixed external optical path signal to the controller; the controller is used for calculating the distance from the laser range finder to the measured object according to the mixed frequency signal after analog-to-digital conversion.
The light emission intensity of the light emitting diode is little affected by temperature, that is, the light emission intensity thereof can be maintained substantially constant even if the light emitting diode is in a light emitting state for a long time (and thus the temperature rises). By utilizing the characteristics of the light emitting diode, the laser range finder provided by the embodiment of the application adopts the light emitting diode as the second transmitting tube to transmit the inner light path signal, so that the intensity of the inner light path signal is basically unchanged with temperature, and therefore, the laser range finder can be used as a reference signal during range finding and used for counteracting the phase variation in the outer light path signal and improving the range finding precision of the range finder.
In some implementations of the embodiments of the present application, a first pwm pin of the controller is connected to the emission driving circuit, and is configured to output a first pwm signal to the emission driving circuit, so as to control the light emission intensities of the first emission tube and the second emission tube.
For laser ranging, the temperature characteristics of the light emitting diode are better than those of the laser diode, but the response time is slower, and the generated optical signal is weaker, so that the ranging is adversely affected. In the implementation manner, the first pulse width modulation signal output by the controller can modulate the driving signal generated by the emission driving circuit, so that the energy of the driving signal is more concentrated under the condition of unchanged power by changing the duty ratio of the first pulse width modulation signal, the light emitting diode can be effectively driven, the response time of the light emitting diode is shortened, and the instantaneous light intensity of the light emitting diode is improved. On the other hand, if the first emitting tube adopts a laser diode, the laser diode can work intermittently, so that the temperature rise of the laser diode is avoided, and the luminous intensity of the laser diode is kept unchanged as much as possible.
In some implementations of the embodiments of the present application, an input/output pin of the controller is connected to the emission driving circuit, and is configured to output a time-sharing control signal to the emission driving circuit, so as to control the first emission tube and the second emission tube to emit light in different periods.
In the above implementation manner, the two emission tubes may operate in a time-division manner, so that the design of the receiving circuit may be simplified, and in addition, if the first emission tube adopts a laser diode, it is also convenient to separately evaluate the influence of the temperature on the light intensity of the laser diode.
In some implementations of embodiments of the application, the laser rangefinder further includes: the temperature sensor is connected with the controller and is arranged among the first transmitting tube, the second transmitting tube and the laser receiving device; when the first emitting tube is a laser diode, the controller is further configured to adjust a duty cycle of the first pulse width modulation signal according to the temperature collected by the temperature sensor, so as to control the luminous intensities of the first emitting tube and the second emitting tube.
In the above implementation manner, if the first emitting tube adopts the laser diode, the temperature change can be monitored by setting the temperature sensor, so that the temperature compensation is performed on the laser diode by changing the duty ratio of the first pulse width modulation signal, so that the luminous intensity of the laser diode is kept unchanged as much as possible, and the influence on the ranging accuracy is avoided. Of course, if both laser emitting tubes are light emitting diodes, they may not be temperature compensated, or even provided with no temperature sensor.
In some implementations of embodiments of the application, the laser rangefinder further includes: the voltage bias adjusting circuit is respectively connected with the second pulse width modulation pin, the second analog-to-digital conversion pin and the laser receiving device of the controller; the controller is further used for adjusting the duty ratio of a second pulse width modulation signal output by the second pulse width modulation pin according to the temperature acquired by the temperature sensor so as to control the bias voltage provided by the voltage bias adjusting circuit for the laser receiving device, and the second analog-to-digital conversion pin is used for acquiring the voltage in the voltage bias adjusting circuit.
Some laser receiving devices, such as avalanche photodiodes, are susceptible to temperature effects to cause unstable gain, in the above implementation manner, by setting a bias circuit and adjusting the bias voltage of the laser receiving device by using a second pulse width modulation signal, the gain of the laser receiving device is kept constant, so that the laser receiving device can work normally, and the influence on the ranging accuracy is avoided.
In some implementations of the embodiments of the present application, the laser range finder further includes a filtering and amplifying circuit, where the filtering and amplifying circuit is respectively connected to the laser receiving device and the first analog-to-digital conversion pin, and is configured to perform low-pass filtering and amplify a mixing signal output by the laser receiving device, and output the mixing signal to the controller.
Mixing two high frequency signals can generate a sum frequency signal and a difference frequency signal, and for laser ranging, the difference frequency signal can be an intermediate frequency signal, wherein phase information is carried, in the implementation mode, the difference frequency signal is filtered and amplified by the filter amplifying circuit, so that the controller can conveniently perform subsequent distance calculation (the high frequency signal cannot be processed by the implementation modes of many controllers).
In some implementations of embodiments of the application, the laser rangefinder further includes: the laser receiving device comprises a transmitting collimating mirror and a receiving collimating mirror, wherein the transmitting collimating mirror is arranged at a first transmitting tube and the receiving collimating mirror is arranged at a laser receiving device, the transmitting collimating mirror is used for focusing the external light path signal transmitted by the first transmitting tube and then emitting the external light path signal to the object to be measured, and the receiving collimating mirror is used for focusing the external light path signal reflected by the object to be measured and then emitting the external light path signal to the laser receiving device.
In the implementation mode, the transmitting collimating lens and the receiving collimating lens can improve the transmission light path of the external light path signal and improve the ranging precision.
In some implementations of embodiments of the application, the laser rangefinder further includes: and the optical filter is arranged on the optical path between the receiving collimating mirror and the laser receiving device and is used for filtering out signals with other wavelengths except the emission wavelength of the signals of the external optical path.
In the implementation mode, the optical filter can filter clutter and improve the ranging precision.
In some implementations of embodiments of the application, the laser rangefinder further includes: and the display module is connected with the controller and is used for displaying the distance measurement result calculated by the controller.
In the above implementation manner, the display module is configured to display the ranging result to the user in real time, so as to improve the practicability of the range finder, and it can be understood that the display module can also display other information.
In some implementations of embodiments of the application, the laser rangefinder further includes: and the key module is connected with the controller and is used for supporting the operation of a user on the laser range finder.
In the implementation mode, man-machine interaction is supported by arranging the key module, so that the practicability of the range finder is improved.
In order to make the above objects, technical solutions and advantageous effects of the present application more comprehensible, embodiments accompanied with the accompanying drawings are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 shows a schematic general structure of a first laser range finder according to an embodiment of the present application;
FIG. 2 is a schematic diagram showing a timing relationship among a driving clock signal, a first PWM signal, and a time-sharing control signal;
FIG. 3 is a schematic diagram of a voltage bias adjustment circuit according to an embodiment of the present application;
fig. 4 is a schematic diagram showing a partial structure of a first laser range finder according to an embodiment of the present application;
fig. 5 shows a schematic general structure of a second laser range finder according to an embodiment of the present application.
In the figure, a 10-laser range finder; 100-a controller; 110-a phase lock circuit; 120-an emission driving circuit; 122-laser diode; 123-a first light emitting diode; 124-light emitting diodes; 125-a second light emitting diode; 126-emission collimator; 130-a local oscillator processing circuit; 140-a laser receiving device; 142-receiving a collimating mirror; 143-an optical filter; 150-a temperature sensor; 160-a voltage bias adjustment circuit; 170-a filter amplification circuit; 180-a display module; 190-a key module; 20-a laser range finder; 200-power module.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the description of the present application, it should be noted that, directions or positional relationships indicated by terms such as "center", "upper", "lower", "left", "right", etc., are directions or positional relationships based on those shown in the drawings, or those that are conventionally put in use in the application, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
In the description of the present application, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the embodiments of the application. The objectives and other advantages of the application will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings.
First embodiment
Fig. 1 shows a schematic general structure of a first laser range finder 10 according to an embodiment of the present application. Referring to fig. 1, the laser rangefinder 10 includes a controller 100, a phase lock circuit 110, a transmit drive circuit 120, a laser diode 122 (i.e., a first transmitting tube), a light emitting diode 124 (i.e., a second transmitting tube), a local oscillator processing circuit 130, and a laser receiving device 140.
The controller 100 is a unit with arithmetic processing capability, and a plurality of functional pins are arranged outside the controller 100 and can be connected with other components to transmit signals and realize corresponding functions. The controller 100 may be implemented by, but is not limited to, a single-chip microcomputer (Micro Controller Unit, MCU), such as a STM32 series single-chip microcomputer. It will be appreciated that in particular implementations, the controller 100 employed should have the functional pins mentioned in the embodiments of the present application, or pins that may perform similar functions.
The phase lock circuit 110 is connected to a clock pin (CLK 1 in fig. 1) of the controller 100, and the phase lock circuit 110 can generate a synchronous clock signal, and input the synchronous clock signal into the controller 100 from the clock pin, so as to be used as a clock source used in the controller 100, and the clock source can be used when performing functions such as analog-to-digital conversion (for details, see later).
The phase lock circuit 110 is also connected to the emission drive circuit 120, and the phase lock circuit 110 is also capable of generating a drive clock signal (rf_clk in fig. 1) and outputting the drive clock signal to the emission drive circuit 120.
The phase lock circuit 110 is also connected to the local oscillation processing circuit 130, and the phase lock circuit 110 is also capable of generating a local oscillation clock signal (lo_clk in fig. 1) and outputting the local oscillation clock signal to the transmission driving circuit 120.
All three signals are generated by the same circuit, so that complete synchronization can be realized. The phase-locked circuit 110 may be implemented by, but not limited to, a phase-locked loop (Phase Locked Loop, PLL), a field programmable gate array (FieldProgrammable Gate Array, FPGA), a complex programmable logic device (Complex Programmable Logic Device, CPLD), a direct digital frequency synthesizer (Direct Digital Synthesizer, DDS), etc. In some implementations, the phase-lock circuit 110 may also be connected to a serial bus pin of the controller 100, so that the controller 100 may control signal generation of the phase-lock circuit 110. Such serial bus pins may be, but are not limited to, serial peripheral interface (Serial Peripheral Interface, SPI) pins, inter-Integrated Circuit, IIC pins, and the like, as shown in FIG. 1.
The emission driving circuit 120 is further connected to the laser diode 122 and the light emitting diode 124, respectively, and the emission driving circuit 120 generates driving signals (RF in fig. 1) according to the received driving clock signals, and the driving signals are used for driving the laser diode 122 to emit light and driving the light emitting diode 124 to emit light, respectively. The optical signal emitted by the laser diode 122 is received by the laser receiving device 140 after being reflected by the surface of the measured object, and the optical path of the signal transmission is outside the laser range finder 10, so that the optical signal is called an external optical path signal (S1 in fig. 1); the optical signal emitted by the light emitting diode 124 is received by the laser receiving device 140 after being transmitted in a predetermined optical path inside the laser rangefinder 10, and is thus referred to as an internal optical path signal (S2 in fig. 1). The inventor finds that the laser diode is more suitable for use in an external light path due to better directivity (small divergence angle), higher luminous efficiency and convenient long-distance transmission, while the light emitting diode is more suitable for use in an internal light path due to worse directivity (large divergence angle), lower luminous efficiency and inconvenient long-distance transmission, and of course, the temperature characteristic of the light emitting diode is advantageous compared with that of the laser diode, which will be explained later. Furthermore, if the laser rangefinder is indeed used mainly for measuring objects at close distances, the external light path signal may also be emitted by means of a light emitting diode, as will be given later.
The local oscillation processing circuit 130 is further connected to the laser receiving device 140, where the local oscillation processing circuit 130 has a signal conditioning function (such as filtering and amplifying), and is capable of generating a local oscillation signal (LO in fig. 1) according to the received local oscillation clock signal, and outputting the local oscillation signal to the laser receiving device 140.
The laser receiving device 140 is further connected to a first analog-to-digital conversion (ADC 1 in fig. 1) pin of the controller 100, where the laser receiving device 140 performs photoelectric conversion on the received internal optical path signal, mixes the received internal optical path signal with the local oscillator signal, generates a first mixing signal, inputs the first mixing signal into the controller 100 from the first analog-to-digital conversion pin, performs photoelectric conversion on the received external optical path signal, mixes the received external optical path signal with the local oscillator signal, generates a second mixing signal, and inputs the second mixing signal into the controller 100 from the first analog-to-digital conversion pin. The laser receiving device 140 may be implemented by, but not limited to, an avalanche photodiode, a normal photodiode, a PIN photodiode, etc. Mixing can be accomplished, for example, using the non-linearities of the avalanche photodiodes.
The first analog-to-digital conversion pin is connected to an analog-to-digital conversion unit inside the controller 100, and can sample and quantize an input analog signal into a digital signal. Further, the controller 100 may have a built-in operation program, and calculate the distance from the laser rangefinder 10 to the measured object according to the two mixed signals after analog-to-digital conversion. Possible calculation modes include: first, an inner optical path distance is calculated according to a first mixing signal, an outer optical path distance is calculated according to a second mixing signal, and then the inner optical path distance is subtracted from the outer optical path distance to obtain a distance to be measured. Second, a phase difference between the first mixed signal and the second mixed signal is calculated, and then a distance to be measured is calculated according to the phase difference. It should be understood that the first mixed signal and the second mixed signal employed in the calculation refer to the quantized signal being sampled instead of the original analog signal. On the other hand, the calculation method for the distance to be measured belongs to the prior art, and the principle and the calculation formula of the method are not explained in detail.
Unlike the prior art, the laser rangefinder 10 of the present application employs light emitting diodes 124 to emit an internal optical path signal. The light emission intensity of the light emitting diode 124 is little affected by temperature, that is, the light emission intensity can be maintained substantially constant even if the light emitting diode 124 is in a light emitting state for a long period of time (e.g., the temperature rises after a long-time measurement). Therefore, in the laser range finder 10, the intensity of the inner optical path signal does not change with the temperature basically, so that the inner optical path signal can be used as a reference signal during ranging to offset the phase variation in the outer optical path signal or calibrate the outer optical path distance by using the inner optical path distance, thereby improving the accuracy of laser ranging.
In some implementations of the embodiments of the present application, the controller 100 is provided with a first PWM pin (PWM 1 in fig. 1) connected to the emission driving circuit 120, and the controller 100 may generate and output a first PWM signal to the emission driving circuit 120, and the controller 100 may modulate the driving signal generated by the emission driving circuit 120 by changing the duty ratio of the first PWM signal, so as to control the light emission intensities of the laser diode 122 and the light emitting diode 124, for example, to increase the duty ratio in the first PWM signal, and the light emission intensities of both diodes will increase under other conditions.
As described above, although the light emission intensity of the light emitting diode is little affected by temperature, the inventors have studied and found that the response time is slow relative to the laser diode and the generated optical signal is weak, which adversely affects ranging. Therefore, after the driving signal is modulated by the first pwm signal, the driving signal can be more concentrated (concentrated in the on-period of the first pwm signal, the on-state can correspond to the high level of the signal) under the condition of unchanged power, so that the led 124 can be effectively driven, the response time of the led can be shortened, the instantaneous light intensity of the led can be improved, the defect of the characteristics of the led can be overcome, and the performance of the laser rangefinder 10 can be improved. On the other hand, since the laser diode 122 and the light emitting diode 124 are driven by the same signal, the laser diode 122 also emits light intermittently (emits light in the on period of the first pwm signal, does not emit light in the off period, and turns off the light at a low level corresponding to the signal), so as to avoid the temperature rise caused by the continuous light emission, and thus, the light emission intensity of the laser diode 122 is kept unchanged, and the ranging accuracy is improved.
In some implementations of embodiments of the present application, the controller 100 is further provided with an input/output pin (I/O in fig. 1) connected to the emission driving circuit 120, and the controller 100 may generate and output a time-division control signal to the emission driving circuit 120, where the time-division control signal may include different levels to indicate which diode should be driven by the emission driving circuit 120 to emit light. For example, the time division control signal may contain periodically repeating high and low levels, wherein a high level indicates that the light emitting diode 124 emits light and a low level indicates that the laser diode 122 emits light. The term "time division" means that the light emission periods of the laser diode 122 and the light emitting diode 124 are shifted, and the light emission states are not simultaneously performed. The two diodes can be operated in time-sharing mode, so that the laser receiving device 140 is simpler in processing, which is beneficial to simplifying the design of a receiving circuit, and in addition, the influence of temperature on the luminous intensity of the laser diode 122 can be evaluated independently.
Fig. 2 shows a schematic diagram of a timing relationship of the driving clock signal, the first pwm signal and the time-sharing control signal, wherein the first pwm signal and the time-sharing control signal may be generated using the aforementioned synchronous clock signal as a clock source so as to be synchronous with the driving clock signal.
With continued reference to fig. 1, in some implementations of the embodiments of the present application, the laser rangefinder 10 further includes a temperature sensor 150, where the temperature sensor 150 is disposed between the laser diode 122, the light emitting diode 124, and the laser receiving device 140, and a specific location is not limited, and one end of the temperature sensor 150 is connected to the controller 100 for sending the collected temperature information to the controller 100. The temperature sensor 150 may be digital or analog, and may be connected to one or more input/output pins of the controller 100 if a digital temperature sensor is used, or to a serial bus pin, and may be connected to an analog-to-digital conversion pin of the controller 100 if an analog temperature sensor is used, which pin of the controller 100 is not indicated in fig. 1 for simplicity.
Considering the position where the temperature sensor 150 is provided, it may be considered that the average temperatures (not necessarily the average in a strict sense) of the laser diode 122, the light emitting diode 124, and the laser receiving device 140 are collected, that is, the controller 100 may monitor the temperature change conditions of the laser diode 122 and the laser receiving device 140 through the temperature sensor 150 (the light emission intensity of the light emitting diode 124 is not substantially affected by the temperature).
With the laser diode 122, in the case where the driving current is constant, the light emission intensity thereof decreases with an increase in temperature, which will adversely affect the ranging accuracy. As a compensation measure, the controller 100 may increase the duty cycle of the first pulse signal, i.e. extend the on-time of the laser diode 122, so that the light emission intensity thereof remains as unchanged as possible, and counteract the effect of the temperature increase. It will be appreciated that since the led 124 and the laser diode 122 are driven by the same signal, if the duty cycle of the first pulse signal is increased, the light emission intensity of the led 124 will be increased, but the change is independent of temperature and does not affect the ranging result. If the temperature measured by the temperature sensor 150 drops, the controller 100 can adjust the duty cycle of the first pulse signal to reduce the duty cycle, which will not be described in detail.
For some laser receiving devices 140, such as avalanche photodiodes, the gain may be unstable due to temperature effects, and may be kept stable by varying their bias voltages. For example, when the temperature of the avalanche photodiode increases, the gain of the avalanche photodiode decreases, and the bias voltage is increased, so that the decrease in gain can be prevented from affecting the ranging accuracy.
As an alternative to adjusting the bias voltage, a voltage bias adjustment circuit 160 may be provided in the laser rangefinder 10, where the voltage bias adjustment circuit 160 is connected to a second pulse width modulation pin (DAC/PWM 2 in fig. 1, where DAC means that the pin may also have a digital-to-analog conversion function) of the controller 100, a second analog-to-digital conversion pin (ADC 2 in fig. 1), and the laser receiving device 140, respectively. The controller 100 may adjust the duty cycle of the second pwm signal output by the second pwm pin according to the temperature information collected by the temperature sensor 150, and control the voltage bias adjustment circuit 160 to provide the bias voltage to the laser receiving device 140, for example, by increasing the duty cycle to increase the bias voltage. The second analog-to-digital conversion pin is used for collecting the voltage in the voltage bias adjustment circuit 160 and feeding back the adjustment effect of the bias voltage.
Fig. 3 shows one possible circuit configuration of the voltage bias adjustment circuit 160 described above. Wherein D2 is an avalanche photodiode (laser receiving device 140), the rest of the elements form a voltage bias adjustment circuit 160, and the adjustment of bias voltage is mainly realized by the on and off of a field effect transistor Q1, where L0 represents a local oscillation signal input into D2, and S3/S4 represents a first mixing signal and a second mixing signal output from D2.
With continued reference to fig. 1, in some implementations of the embodiment of the present application, the laser rangefinder 10 further includes a filter amplification circuit 170, where the filter amplification circuit 170 is respectively connected to the laser receiving device 140 and the first analog-to-digital conversion pin, and the mixing signal (including the first mixing signal and the second mixing signal) output by the laser receiving device 140 is low-pass filtered and amplified by the filter amplification circuit 170, and then output to the controller 100.
Mixing the two signals can generate a sum frequency signal (the signal frequency is the sum of the frequencies of the two signals before mixing) and a difference frequency signal (the signal frequency is the difference between the frequencies of the two signals before mixing), and when laser ranging is performed, the local oscillator signal and the internal and external optical path signals are usually high-frequency signals (such as MHz level signals), so that the difference frequency signal generated after mixing can be an intermediate-frequency signal (such as KHz level signals), which carries phase information for calculating the distance.
In some implementations of embodiments of the present application, the laser rangefinder 10 further includes a transmit collimator 126 disposed at the laser diode 122 and a receive collimator 142 disposed at the laser receiving device 140. The transmit collimator 126 and the receive collimator 142 may be optical lenses, such as plano-convex lenses. The emission collimating mirror 126 focuses the external light path signal emitted by the laser diode 122 and emits the focused external light path signal to the object to be measured, so as to avoid the overlarge divergence angle of the laser signal and reduce the signal intensity. The receiving collimator 142 focuses the external light path signal reflected by the measured object and then makes the external light path signal incident on the laser receiving device 140, so that the intensity of the received signal is improved, and the ranging accuracy is improved. Reference may also be made to fig. 4 for specific placement of the transmit collimator 126 and the receive collimator 142, the propagation direction of the optical signal being shown by the arrowed lines in fig. 1, 4.
With further reference to fig. 4, in some implementations of the embodiments of the present application, the laser rangefinder 10 further includes a filter 143 disposed on an optical path between the receiving collimator 142 and the laser receiving device 140, where a center wavelength of the filter 143 may be an emission wavelength of an external optical path signal, and interference signals (such as light of an external environment) of other wavelengths are filtered out or at least substantially attenuated by the filter 143, so as to facilitate improvement of measurement accuracy. Such a filter 143 may be, but is not limited to, a narrowband filter.
With continued reference to fig. 1, in some implementations of the embodiments of the present application, the laser rangefinder 10 further includes a display module 180 connected to the controller 100, and after the control module calculates the ranging result, the ranging result may be sent to the display module 180 for display, so that the user can learn the ranging result in real time, thereby improving the practicality of the rangefinder. It will be appreciated that the display module 180 may also display other information such as measurement status information of the rangefinder, device status information, etc. The display module 180 may employ, but is not limited to, a liquid crystal display, an organic light emitting diode display, etc.
In some implementations of the embodiments of the present application, the laser rangefinder 10 further includes a key module 190 connected to the controller 100, where the key module 190 may be one or more physical buttons disposed on a surface of the laser rangefinder 10, and directly or indirectly connected to the controller 100, and a user may implement manipulation of the laser rangefinder 10 by pressing the corresponding buttons, so as to improve practicality of the rangefinder. It will be appreciated that in some alternatives, the display module 180 and the key module 190 may be combined with each other, for example, by directly using a touch screen to implement the functions of both modules.
In some implementations of embodiments of the present application, the laser rangefinder 10 further includes a power module 200 for powering components of the laser rangefinder 10, the connection relationship with the components not being shown in detail in fig. 1. The power module 200 may use an internal power source, such as a storage battery, or an external power source, such as an ac mains, where the power module 200 may convert a current or voltage signal from the external power source into a form suitable for use by the laser rangefinder 10.
Second embodiment
Fig. 5 shows a schematic general structure of a second laser rangefinder 20 according to an embodiment of the application. Referring to fig. 5, the laser rangefinder 20 includes a controller 100, a phase lock circuit 110, a transmit drive circuit 120, a first light emitting diode 123 (i.e., a first transmitting tube), a second light emitting diode 125 (i.e., a second transmitting tube), a local oscillator processing circuit 130, and a laser receiving device 140.
The phase lock circuit 110 is respectively connected to the clock pin of the controller 100, the transmission driving circuit 120 and the local oscillation processing circuit 130, and is configured to output a synchronous clock signal to the controller 100, output a driving clock signal to the transmission driving circuit 120, and output a local oscillation clock signal to the local oscillation processing circuit 130;
the emission driving circuit 120 is further connected to the first light emitting diode 123 and the second light emitting diode 125, and is configured to drive the first light emitting diode 123 to emit an external light path signal, and drive the second light emitting diode 125 to emit an internal light path signal;
the local oscillation processing circuit 130 is further connected to the laser receiving device 140, and is configured to output a local oscillation signal to the laser receiving device 140;
the laser receiving device 140 is further connected to the first analog-to-digital conversion pin of the controller 100, and is configured to mix the received internal optical path signal with the local oscillation signal and output the mixed internal optical path signal to the controller 100, and mix the received external optical path signal reflected by the measured object with the local oscillation signal and output the mixed external optical path signal to the controller 100;
the controller 100 is configured to calculate a distance from the laser rangefinder 20 to the measured object according to the analog-to-digital converted mixed signal.
It will be readily appreciated that the second embodiment is similar in construction and function to the laser rangefinder 20 provided in the first embodiment, and only the main differences will be described below, the remainder of which may be referred to the description in the first embodiment.
In the laser rangefinder 20 provided in the second embodiment, the laser diode 122 is replaced by the first light emitting diode 123, and it has been mentioned that the light emitting diode is not suitable for long-distance transmission of optical signals, so the laser rangefinder 20 provided in the second embodiment is mainly used for measuring objects to be measured which are closer in distance, and in such a scenario, since the light emitting intensities of the two light emitting diodes are not affected by temperature, a higher ranging accuracy can still be obtained.
With respect to some optional components of the laser rangefinder 20 provided in the second embodiment, not mentioned above, reference may be made to fig. 5. It should be noted that, since the internal and external optical path signals are both emitted by the light emitting diodes, the controller 100 does not need to perform temperature compensation on the two light emitting diodes according to the temperature measured by the temperature sensor 150, and the temperature sensor 150 will be mainly used to adjust the bias voltage to the laser receiving device 140. In addition, the first pulse width modulation signal has no effect except temperature compensation, and can still control the luminous intensity of the inner and outer light path signals through the duty ratio of the first pulse width modulation signal, so that the response speed of the light emitting diode is improved.
It is to be understood that the above examples of the present application are provided for clarity of illustration only and are not limiting of the embodiments of the present application. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are desired to be protected by the following claims.
Claims (9)
1. The laser range finder is characterized by comprising a controller, a phase-locked circuit, a transmitting driving circuit, a first transmitting tube, a second transmitting tube, a local oscillation processing circuit and a laser receiving device, wherein the first transmitting tube is a laser diode or a light emitting diode, and the second transmitting tube is a light emitting diode;
the phase-locked circuit is respectively connected with the clock pin of the controller, the emission driving circuit and the local oscillation processing circuit and is used for outputting a synchronous clock signal to the controller, outputting a driving clock signal to the emission driving circuit and outputting a local oscillation clock signal to the local oscillation processing circuit;
the emission driving circuit is also connected with the first emission tube and the second emission tube respectively and is used for driving the first emission tube to emit an external light path signal and driving the second emission tube to emit an internal light path signal;
the local oscillation processing circuit is also connected with the laser receiving device and is used for outputting local oscillation signals to the laser receiving device;
the laser receiving device is also connected with a first analog-to-digital conversion pin of the controller and is used for mixing the received internal optical path signal with the local oscillation signal and outputting the mixed internal optical path signal to the controller, and mixing the received external optical path signal reflected by the measured object with the local oscillation signal and outputting the mixed external optical path signal to the controller;
the controller is used for calculating the distance from the laser range finder to the measured object according to the mixed frequency signal after analog-to-digital conversion;
the laser rangefinder further includes: the temperature sensor is connected with the controller and is arranged among the first transmitting tube, the second transmitting tube and the laser receiving device;
the laser rangefinder further includes: the voltage bias adjusting circuit is respectively connected with the second pulse width modulation pin, the second analog-to-digital conversion pin and the laser receiving device of the controller;
the controller is further used for adjusting the duty ratio of a second pulse width modulation signal output by the second pulse width modulation pin according to the temperature acquired by the temperature sensor so as to control the bias voltage provided by the voltage bias adjusting circuit for the laser receiving device, and the second analog-to-digital conversion pin is used for acquiring the voltage in the voltage bias adjusting circuit.
2. The laser rangefinder of claim 1 wherein the first pwm pin of the controller is coupled to the emission drive circuit for outputting a first pwm signal to the emission drive circuit to control the emission intensity of the first and second emission tubes.
3. The laser range finder according to claim 2, wherein the input/output pin of the controller is connected to the emission driving circuit, and is configured to output a time-sharing control signal to the emission driving circuit, so as to control the first emission tube and the second emission tube to emit light in different periods.
4. The laser rangefinder of claim 2 wherein the laser beam is directed to the laser beam,
when the first emitting tube is a laser diode, the controller is further configured to adjust a duty cycle of the first pulse width modulation signal according to the temperature acquired by the temperature sensor, so as to control the luminous intensities of the first emitting tube and the second emitting tube.
5. The laser range finder according to claim 1, further comprising a filtering and amplifying circuit, wherein the filtering and amplifying circuit is respectively connected to the laser receiving device and the first analog-to-digital conversion pin, and is configured to low-pass filter and amplify the mixed signal output by the laser receiving device and output the amplified mixed signal to the controller.
6. The laser rangefinder of claim 1 further comprising: the laser receiving device comprises a transmitting collimating mirror and a receiving collimating mirror, wherein the transmitting collimating mirror is arranged at a first transmitting tube and the receiving collimating mirror is arranged at a laser receiving device, the transmitting collimating mirror is used for focusing the external light path signal transmitted by the first transmitting tube and then emitting the external light path signal to the object to be measured, and the receiving collimating mirror is used for focusing the external light path signal reflected by the object to be measured and then emitting the external light path signal to the laser receiving device.
7. The laser rangefinder of claim 6 further comprising: and the optical filter is arranged on the optical path between the receiving collimating mirror and the laser receiving device and is used for filtering out signals with other wavelengths except the emission wavelength of the signals of the external optical path.
8. The laser rangefinder of any of claims 1-7 further comprising: and the display module is connected with the controller and is used for displaying the distance measurement result calculated by the controller.
9. The laser rangefinder of any of claims 1-7 further comprising: and the key module is connected with the controller and is used for supporting the operation of a user on the laser range finder.
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