CN206905716U - Laser grating striped projection system based on multifacet rotating prism - Google Patents

Abstract

The utility model relates to a laser grating fringe projection system based on a multi-faceted rotating prism, which comprises a housing, a semiconductor laser installed in the housing, a reference laser, a multi-faceted rotating prism, a photodiode and a system control circuit board. The system control circuit board passes through a single-chip microcomputer Realize sine modulation and square wave modulation of the laser, over-voltage protection, power-down protection of modulated signal data, drive of multi-faceted rotating prism, measurement and control of multi-faceted rotating prism speed, and real-time communication with PC. The control part of the system uses a multi-faceted rotating prism as a reflective mirror, a laser as an actuator for signal modulation, and an STM32F103 as a control chip to project grating stripes with different characteristics. A photodiode is used as a detection element for the prism's rotational speed. Serial communication, real-time display of detection data and control of the frequency and DC bias of the modulation signal to realize the control of laser modulation.

Description

Laser grating fringe projection system based on polygonal rotating prism

Technical field:

The utility model belongs to the field of optical measurement and relates to a laser grating fringe projection system, in particular to a laser grating fringe projection system based on a multi-faceted rotating prism.

technical background:

The three-dimensional measurement technology of objects has been gradually developed in the direction of high precision, high speed and complex environment. As the main measurement technology, structured light depth vision sensing technology has the advantages of non-contact, high precision and fast speed. The digital projection system based on digital light processing technology (DLP) is often used to generate grating fringes, and the phase calculation method can be used to quickly obtain three-dimensional (3D) data that can reach video frame rate, pixel level, and full field of view at one time. However, the grating fringe projection method based on white light source and projection optical system is difficult to obtain high spatial resolution, high precision, and continuous sinusoidal grating fringes, which limits its application in the precise measurement of tiny devices. Precision, greatly affected by the industrial site environment and the surface reflectivity of the measured object, the structured light scanning system based on the line laser light source is often used in these occasions, but the feature extraction can only be performed on a single laser line during measurement, and the measurement rate is limited . In order to solve the contradiction between measurement speed, precision and measurement adaptability in 3D online measurement of objects. This system adopts a laser grating fringe projection system designed with a multi-faceted rotating prism.

Utility model content:

The purpose of this utility model is to solve the contradiction between the accuracy, measurement speed and measurement adaptability of the three-dimensional shape measurement technology. The control part of the system takes the STM32F103C8T6 single-chip microcomputer as the core to realize the modulation of the sinusoidal signal of the laser and the modulation of the square wave signal, Laser overvoltage protection, multi-faceted rotating prism drive, multi-faceted rotating prism rotation speed detection and control synchronization signal, data power-down protection and serial communication with PC.

Realize the technical scheme of the utility model purpose:

A laser grating fringe projection system based on a multi-faceted rotating prism, including a housing and a semiconductor laser installed in the housing, a reference laser, a multi-faceted rotating prism, a photodiode and a system control circuit board. The system control circuit board implements the laser through a single-chip computer Sine modulation and square wave modulation, over-voltage protection, power-down protection of modulated signal data, driving of multi-faceted rotating prism, measurement and control of rotating speed of multi-faceted rotating prism, real-time communication with PC.

The single-chip microcomputer adopts ST's STM32F103 single-chip microcomputer;

For the sinusoidal modulation of the laser, the digital-to-analog converter outputs the sinusoidal signal and DC bias, and the summation operator outputs the sinusoidal modulation signal to realize the modulation of the laser.

The square wave modulation of the laser uses PWM (pulse width modulation demodulation) to generate a square wave signal. The corresponding circuit is integrated inside the controller STM32F103, which can generate a square wave signal through its PWM mode, and the square wave signal can modulate the laser after passing through the buffer (74HC125).

For the overvoltage protection of the laser, the sinusoidal modulation signal enters the sampling circuit (op amp chip UA741) to sample the peak voltage of the sinusoidal signal through the voltage follower, and then is sampled by the analog-to-digital converter of the microcontroller after being divided by a precision resistor monitor.

The power-down protection of the data adopts the EEPROM storage chip AT24C02 of the serial IIC protocol interface to realize the preservation of the modulated signal data.

The driving of the multi-faceted rotating prism is realized by the motor driver, and the STM32F103 outputs a trigger signal to control the motor driver to drive the multi-faceted rotating prism.

For the measurement of the rotation speed of the multi-faceted rotating prism, the optical signal is converted into an electrical signal by the photodiode, the signal is amplified by the amplifier, and the pulse signal (digital signal) is generated by the voltage comparator.

As a further improvement of the utility model, the laser sinusoidal modulation process is as follows:

(1) The modulation amplitude voltage of the laser is 3-5V. The single-chip microcomputer controls the digital-to-analog converters DAC7811 and TLV5636 to output a sinusoidal signal with a peak voltage of 3V and a DC bias signal of 0-2V.

(2) The sinusoidal signal and the DC bias signal are reversed and summed through the inverting summation operator (the main operational amplifier is TLC2272), so that the signal amplitude varies between -3v and -5v.

(3) The negative modulation signal output by the summation operator passes through the inverse proportional amplifier (magnification factor is 1) to realize the inversion of the signal from negative to positive.

(4) Send the modulation signal output in (3) to the laser to realize the change of the projected stripes of the laser.

As a further improvement of the utility model, the rotation speed measurement process of the multi-faceted rotating prism is as follows:

(1) The laser light emitted by the reference laser is reflected by the prism to the photodiode, and the optical signal is converted into a weak electrical signal.

(2) The electrical signal output in (1) is amplified by the same-phase proportional amplifier (AD8001), and the signal is buffered and isolated by the voltage follower (ADOP07).

(3) Digitize the amplified signal through a voltage comparator (LM393) to obtain an LVTTL level signal.

(4) The level signal is sent to the single-chip microcomputer after passing through the buffer (74HC125), and the rotational speed of the prism is obtained through the single-chip microcomputer processing.

As a further improvement of the utility model, the PC sends different identification codes to the single-chip microcomputer through the serial port to realize the control of the frequency of the sinusoidal signal, the square wave frequency and the DC offset amount, and the single-chip computer sends the frequency and DC offset of the current signal to the PC through the serial port. The offset value and timing send the prism speed value to the PC.

The utility model provides a laser tube grating stripe projection system. The appearance structure of the system adopts a combination of multiple parts and components. The intelligent control part takes the STM32F103 single-chip microcomputer as the core to realize the sinusoidal modulation and square wave modulation of the laser. The laser overvoltage protection, The power-down protection of the modulated signal data, the measurement and control of the rotation speed of the multi-faceted rotating prism, and the real-time communication of the PC have a good application prospect in the industrial three-dimensional shape measurement market.

The beneficial effects of the utility model are:

(1) The intelligent control part of the system uses a multi-faceted rotating prism as a reflecting mirror, a laser as an actuator for signal modulation, and an STM32F103 as a control chip to project grating stripes with different characteristics, and a photodiode as a detection element for the prism speed. Serial communication with PC, real-time display of detection data and control of modulation signal frequency and DC offset. Realize intelligent control of laser modulation.

(2) This system can change the frequency, pulse width and phase of the laser grating stripes to obtain different patterns of stripes, and can also use the characteristics of semiconductor lasers to facilitate the modulation of light intensity.

(3) In addition to being applied to the measurement of small-sized devices, the system can also be conveniently applied to rapid and large-scale three-dimensional shape measurement by modifying the optical parameters. Relying on the convenience of the projection of this system, the change of the grating fringe projection mode can be conveniently realized directly by changing the circuit modulation signal.

(4) The mounting seat of the multi-faceted rotating prism adopts a semi-enclosed design, which wraps the lower half of the prism and only leaves the prism surface exposed, making the prism rotation stable.

(5) The semiconductor laser can be directly fixed on the mounting base, and the position of the mounting base can be adjusted freely left and right to achieve the best projection angle of the semiconductor laser.

(6) The appearance mechanism of the system adopts a combination of multiple parts, which is convenient for disassembly and debugging. There are mounting holes for the circuit board on specific parts, and it is nice to package the various parts (circuit board, photodiode, reference laser, etc.) together. Small size, high reliability, convenient and flexible application, can meet different measurement environments.

Description of drawings

Figure 1 is the appearance of the system;

Figure 2 is an exploded view of the system structure;

Among them, 1-housing; 1-1~1-6 are the panels of the housing; 1-7, 1-8 are the frames of the housing; 2-display installation holes; 3-multi-faceted rotating prism fixing seat; 4- Reference laser; 5-reference laser fixing seat; 6-photodiode; 7-polygonal rotating prism; 8-semiconductor laser fixing seat; 9-semiconductor laser; 10-guiding groove. 11-notch

Fig. 3 is the circuit block diagram of the control circuit board of this system;

Fig. 4 is the flow chart of the realization of power-down data recovery and overvoltage protection function of the system;

Fig. 5 is the flow chart of realizing the sinusoidal modulation signal frequency, DC bias setting and data protection function of the system;

Figure 6 is a flow chart for the implementation of the system's multi-faceted rotating prism speed measurement function.

detailed description

The utility model will be further described in detail below in conjunction with the accompanying drawings and through specific embodiments. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the utility model.

A laser grating fringe projection system based on a multi-faceted rotating prism, including a housing 1 and a semiconductor laser 9 installed in the housing, a reference laser 4, a multi-faceted rotating prism 7, and a photodiode 6, on the left inner wall 1 of the housing -2 fixed mount multi-faceted rotating prism holders 3, multi-faceted rotating prisms are installed on the multi-faceted rotating prism holders, and two inclined guide grooves 10 are formed in parallel at intervals on the left side inner wall below the multi-faceted rotating prism holders. The semiconductor laser holder 8 is slidably installed in the guide groove, and the semiconductor laser is installed on the semiconductor laser holder. The semiconductor laser finds the best projection position by moving, so that the performance of the projection system is optimized. The reference laser fixing seat 5 and the photodiode are fixed on the inner wall 1-3 of the top surface of the housing, and the reference laser is installed on the reference laser fixing seat.

The system control circuit board is installed on the right inner wall 1-5 of the housing; the multi-faceted rotating prism drive board is installed on the rear inner wall 1-4 of the housing; the display screen is installed on the outer side of the top surface 1-3 of the housing, and the power supply The module is fixed on the inner side of the top surface of the housing, and a display screen installation hole 2 is formed on the top surface of the housing, and a gap 11 is formed on the front panels 1-1, 1-6 of the housing, and the laser grating stripes are projected from this gap. There is also an interface for serial communication with the PC on the shell. The structure design is scientific and reasonable, small and flexible, and can be applied to different measurement occasions.

The mounts of the semiconductor laser and the multi-faceted rotating prism are fixed on the shell surface, which increases the thickness of the shell surface and makes the multi-faceted rotating prism more stable during the rotation process. The design of the system mechanism optimizes the overall volume of the system. In addition, the structure of the system is made of iron materials except for the multi-faceted rotating prism fixing seat and the semiconductor laser fixing seat that play a stable and fixed role, and other structural components are made of aluminum materials, making the whole system light.

The system control circuit board includes a single-chip microcomputer and a power module connected to the single-chip microcomputer, a memory, a voltage comparator, two D/A converters, and a resistor divider circuit unit. The single-chip microcomputer is also connected to a display screen, a PC and a reference laser. The voltage comparator is connected with the proportional amplifier, and the proportional amplifier is connected with the photodiode. The two D/A converters are connected to the operation adder, the operation adder is respectively connected to the semiconductor laser and the sample and hold circuit unit, the sample and hold circuit unit is connected to the resistance voltage divider circuit unit, and the resistance voltage divider circuit unit is connected to the single chip microcomputer.

Figure 3 is a block diagram of the system control circuit board. The single-chip microcomputer controls two D/A converters to output sinusoidal signals and DC offsets. The arithmetic adder superimposes the two signals and sends them to the semiconductor laser for modulation. At the same time, the sample-and-hold circuit samples the sinusoidal modulation signals in real time and processes them through voltage division. Then send it to the A/D converter of the single chip microcomputer. The photodiode receives the reflected laser and converts it into an electrical signal. The electrical signal is amplified by the amplifier and output to the voltage comparator for comparison with the reference voltage, and then the output TTL level signal is sent to the microcontroller. The data memory is used to store the information of the modulated signal. The PWM circuit integrated in the single chip microcomputer generates a square wave signal to modulate the semiconductor laser. The PC communicates with the single-chip microcomputer to set the parameters of each modulation signal, and echoes them on the PC at the same time. The parameter information of each modulation signal, the rotation speed of the multi-faceted rotating prism and the peak voltage of the signal are displayed on the display screen.

The working voltage of STM32F103 single-chip microcomputer is 2.0-3.6V, and the designed power supply circuit supplies power for each chip such as single-chip microcomputer. Part of the op amp chips in this system are powered by dual power supplies. The negative voltage entering the system directly supplies power to each op amp. In addition to powering chips such as op amps, the positive voltage outputs 3.3V to the microcontroller and 3.3V voltage through the LM1117 voltage regulator. The working module is powered.

The control system takes the single-chip microcomputer as the core, cooperates with various chips and related circuits to realize the projection of laser grating stripes. Using ST's STM32F103C8T6 single-chip microcomputer, low power consumption, high performance, low-cost 32-bit single-chip microcomputer, the highest operating frequency can reach 72MHz and rich peripherals can meet the different needs of designers.

Figure 4, Figure 5 and Figure 6 are the flow charts of system function realization. The main task of the single-chip microcomputer in this system is to complete the generation of the modulation signal, the multi-faceted prism speed measurement, the peak voltage detection, the data power-down protection, the communication with the PC and the parameter display. The single-chip microcomputer reads the modulation signal information from the memory and writes it into the corresponding module; it also needs to detect whether the peak voltage exceeds the threshold and make corresponding operations; finally, the parameters are displayed. After setting the timing value in the timer, the sinusoidal signal waveform can be generated in the timing interrupt. The input capture interrupt of the microcontroller can solve the rotational speed of the prism in real time. When the single-chip microcomputer receives the data, it judges which parameter setting identifier is set, and the corresponding flag is set to 1 according to the identifier, and the signal parameter is set and echoed on the PC side through the flag.

What is described above is only the preferred embodiment of the present utility model, and it should be pointed out that for those of ordinary skill in the art, without departing from the premise of the utility model concept, some deformations and improvements can also be made, and these all belong to the present invention. Protection scope of utility model.

Claims (6)

1. A laser grating fringe projection system based on a multi-faceted rotating prism, characterized in that: comprise a housing and a semiconductor laser installed in the housing, a reference laser, a multi-faceted rotating prism, a photodiode and a system control circuit board, the system The control circuit board includes a single-chip microcomputer and a power module connected to the single-chip microcomputer, a memory, a voltage comparator, two D/A converters, and a resistor divider circuit unit. Proportional amplifier, the proportional amplifier is connected to the photodiode, the two D/A converters are connected to the operation adder, the operation adder is respectively connected to the semiconductor laser and the sample and hold circuit unit, the sample and hold circuit unit is connected to the resistance voltage divider circuit unit, and the resistance voltage divider circuit The unit is connected to the single-chip microcomputer, and the system control circuit board realizes the sine modulation and square wave modulation of the laser through the single-chip microcomputer, overvoltage protection, power-down protection of the modulation signal data, driving of the multi-faceted rotating prism, measurement and control of the speed of the multi-faceted rotating prism, and real-time monitoring with the PC. communication. 2. The laser grating fringe projection system based on a multi-faceted rotating prism according to claim 1, wherein a multi-faceted rotating prism holder is fixed on the left side inner wall of the housing, and a multi-faceted rotating prism is installed on the multi-faceted rotating prism holder And its driving motor, two inclined guide grooves are parallelly formed on the left inner wall below the multi-faceted rotating prism fixing seat, slide and install the semiconductor laser fixing seat in the two guiding grooves, and install the semiconductor laser on the semiconductor laser fixing seat , the reference laser holder and photodiode are installed on the top inner wall of the housing, the reference laser is installed on the reference laser holder, the system control circuit board is installed on the right inner wall of the housing; the multi-faceted rotating prism drive board is installed on the housing The display screen is installed on the outside of the top surface of the housing, the power module is fixed on the inside of the top surface of the housing, the display screen is embedded on the top surface of the housing, and a gap is made on the front panel of the housing. The grating stripes are projected from this gap, and an interface for serial communication with the PC is also formed on the casing. 3. The laser grating fringe projection system based on a multi-faceted rotating prism according to claim 1, wherein the sinusoidal modulation is output by a digital-to-analog converter sinusoidal signal and DC bias, and the sinusoidal modulation is output by a summing operator signal to realize the modulation of the laser. 4. The laser grating fringe projection system based on the multi-faceted rotating prism according to claim 1, characterized in that: the square wave modulation is to generate a square wave signal through the PWM mode of the single-chip microcomputer, and the square wave signal is modulated after passing through the buffer laser. 5. The laser grating fringe projection system based on a multi-faceted rotating prism according to claim 1, characterized in that: the overvoltage protection is that the sinusoidal modulation signal of the laser enters the sampling circuit after passing through the voltage follower, and the peak voltage of the sinusoidal signal Sampling is performed, and then the analog-to-digital converter of the microcontroller performs sampling and monitoring after being divided by a precision resistor. 6. The laser grating fringe projection system based on a multi-faceted rotating prism according to claim 1, wherein the measurement and control of the rotational speed of the prism is to convert the optical signal sent by the reference laser into an electrical signal by a photodiode, which is amplified by an amplifier Signal, use the voltage comparator to generate the pulse digital signal, after the single-chip microcomputer collects, carry out the corresponding processing to get the rotational speed.