CN113126067A - Laser safety circuit and laser safety equipment - Google Patents
Laser safety circuit and laser safety equipment Download PDFInfo
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- CN113126067A CN113126067A CN201911401696.8A CN201911401696A CN113126067A CN 113126067 A CN113126067 A CN 113126067A CN 201911401696 A CN201911401696 A CN 201911401696A CN 113126067 A CN113126067 A CN 113126067A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/497—Means for monitoring or calibrating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/44—Electric circuits
- G01J1/46—Electric circuits using a capacitor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J2001/4238—Pulsed light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J2001/4247—Photometry, e.g. photographic exposure meter using electric radiation detectors for testing lamps or other light sources
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/44—Electric circuits
- G01J2001/4446—Type of detector
- G01J2001/446—Photodiode
Abstract
The application provides a laser safety circuit, which comprises a photosensitive diode, a resistor, a first capacitor, a second capacitor and a photosensitive chip, wherein the photosensitive chip is provided with a reference voltage port and an analog-to-digital converter; the photosensitive diode is used for monitoring the intensity change of light rays in the emission cavity of the emission module and passing current signals with corresponding magnitude according to the intensity change of the light rays; the current signals with corresponding magnitude are converted into voltage signals with corresponding magnitude through the resistor; the second capacitor is used for being matched with the first capacitor to filter low-frequency signals and direct-current signals in the voltage signals; the reference voltage port is used for providing a reference voltage signal to the second capacitor; the analog-to-digital converter is used for detecting a reference voltage signal of the second capacitor and a filtered voltage signal. The utility model provides a laser safety circuit has solved little current that prior art's environment light shines the PD production and the dark current of PD during operation can be detected by the ADC to disturb the judgement to emission module abnormal state, easily cause the problem of hourglass detection and false detection.
Description
Technical Field
The application relates to the technical field of electronic circuits, in particular to a laser safety circuit and laser safety equipment.
Background
The 3D (three dimensional) imaging module comprises a transmitting module and a receiving module, modulated light is transmitted to the object to be detected through the transmitting module, and the receiving module receives the light reflected by the surface of the object to be detected, so that the electronic equipment applying the 3D imaging module can realize the function of acquiring and displaying the depth information of the object to be detected.
In the emission module, light emitted by the laser emitter can form a surface light source with high uniformity and good directivity after being diffused by the light diffusion element, and the surface light source is widely applied to a Time of flight (TOF) module to realize 3D depth measurement. However, due to the fact that the emitting angle of the laser emitter is small, when the emitting module is abnormal, if the light diffusion element above the laser emitter falls off, emitting energy is concentrated in a small angle, and potential safety hazards exist for eyes and skin of an object to be detected. Due to strict requirements on protection of an object to be measured and laser safety, a PD (Photo diode) is disposed at a position close to a laser transmitter, and the PD is often located in a laser safety circuit to determine whether an emitting module is abnormal according to energy sensed by the PD.
In the laser safety circuit, the PD receives partial light intensity from the laser transmitter and the external environment, and converts the partial light intensity into a current signal of a corresponding magnitude, and the current signal is detected by an ADC (Analog-to-Digital Converter) and used as a basis for determining whether the transmitting module is abnormal. In the existing laser safety circuit, micro current generated by the PD irradiated by ambient light and dark current generated by the PD during working can be detected by the ADC, the output voltage of the laser emitter detected by the PD is influenced, so that the output voltage of the laser emitter fluctuates under different scenes, the judgment of the abnormal state of the emission module is interfered, the conditions of detection leakage and misdetection exist, and potential safety hazards are easily caused.
Disclosure of Invention
As shown in fig. 5, in the conventional laser safety circuit, a PD (Photo diode) receives a part of the light intensity from the laser transmitter and the external environment, and converts the light intensity into a current of a corresponding magnitude. This electric current can be through the resistance conversion of ground connection to voltage, again because the little electric current that the light irradiation PD of environment produced and the dark current of PD during operation also can be through the resistance conversion of ground connection to voltage, thereby influence the output voltage of the laser emitter that the PD detected, lead to under different scenes, the output voltage of laser emitter produces undulant, influence the accuracy that ADC (Analog-to-Digital Converter) detected, and disturb the judgement of ADC to the transmission module abnormal state, there is the condition of hourglass detection and false detection, easily cause the potential safety hazard, lead to can be to if judging whether the transmitted power of laser emitter is unusual and diffusion piece and transmission module whether the precision such as sheltered from caused the influence, easily produce the erroneous judgement.
In view of this, the application provides a laser safety circuit and laser electronic equipment to solve among the laser safety circuit of prior art, little electric current that the environment light shines the PD and the dark current of PD during operation can be detected by the ADC, influences the output voltage of the laser emitter that the PD detected, leads to under different scenes, the output voltage of laser emitter produces undulant to disturb the judgement to the emission module abnormal state, there are the condition of hourglass detection and false detection, easily cause the problem of potential safety hazard.
In a first aspect, the present application provides a laser safety circuit, which includes a photodiode, a resistor, a first capacitor, a second capacitor, and a photosensitive chip, where the photosensitive chip is provided with a reference voltage port and an analog-to-digital converter;
the photosensitive diode is used for monitoring the intensity change of light rays in the emission cavity of the emission module and passing current signals with corresponding magnitude according to the intensity change of the light rays; the current signal with the corresponding magnitude is converted into a voltage signal with the corresponding magnitude through the resistor; the second capacitor is used for being matched with the first capacitor to filter low-frequency signals and direct-current signals in the voltage signals; the reference voltage port is used for providing a reference voltage signal to the second capacitor; the analog-to-digital converter is used for detecting the reference voltage signal of the second capacitor and the filtered voltage signal.
Therefore, by arranging the first capacitor and the second capacitor, the problem that the micro current generated by the photosensitive diode irradiated by ambient light and the dark current generated when the photosensitive diode works are converted into voltage through the resistor to influence the output voltage of the laser transmitter caused by adopting a single-resistor type laser safety scheme in the prior art is greatly avoided, further the problem of judging whether the state of the transmitting module is abnormal or not is interfered, so that the output voltage of the photosensitive diode is not influenced by ambient light and dark current, the flexibility of the laser safety equipment applying the laser safety circuit to different scenes is greatly improved, and the safety threshold of the photosensitive diode is effectively tightened, so that the response precision and sensitivity of the photosensitive diode to the light change condition of the transmitting module can be improved, and the judgment precision of the analog-to-digital converter for judging the abnormal state of the transmitting module is further improved.
In a possible implementation manner, one end of the photodiode is connected to an operating voltage, the other end of the photodiode is connected to one end of the resistor, one end of the first capacitor and one end of the second capacitor, the other end of the resistor is grounded, the other end of the first capacitor is grounded, and the other end of the second capacitor is connected to the reference voltage port and the analog-to-digital converter.
It can be understood that the analog-to-digital converter collects the voltage signals filtered by the first capacitor and the second capacitor, that is, the voltage to ground of the filtered resistor is collected, so that whether the light in the emission cavity where the photosensitive element is located has an abnormal change can be judged according to the change situation of the voltage to ground of the filtered resistor. The voltage signal is filtered by arranging a first capacitor and a second capacitor, specifically, the first capacitor is matched with the second capacitor, so that low-frequency signals and direct-current signals which are useless for the signal-to-noise ratio are filtered, the purpose of eliminating interference is achieved, and the detection precision of the analog-to-digital converter is improved. Meanwhile, the signal with the removed direct current component only contains an effective alternating current signal, so that the integral input deviation semaphore is reduced, and the detection precision of the analog-to-digital converter is further improved.
In a possible embodiment, the first capacitor is a low-pass capacitor, and the low-pass capacitor is capable of allowing signals below a preset cut-off frequency to pass through and preventing signals above the preset cut-off frequency from passing through.
Therefore, the first capacitor is arranged and grounded, so that the low-frequency signal which is useless for the signal-to-noise ratio is grounded due to the low-pass characteristic of the first capacitor, and the influence of the oscillation of the low-frequency signal on the detection precision of the analog-to-digital converter is avoided. Meanwhile, the high-frequency signal after filtering can be smoothly detected by the analog-to-digital converter due to the characteristic of preventing the high-frequency signal from passing through, and the accuracy of the detected object is effectively ensured.
In a possible embodiment, the second capacitor is a high-pass capacitor, which is capable of allowing signals above a preset cut-off frequency to pass through, and preventing signals below the preset cut-off frequency from passing through.
And the second capacitor is connected with the analog-to-digital converter, so that the signal with lower frequency can be greatly attenuated through the high-pass characteristic of the second capacitor, the low-frequency signal and the direct-current signal which are not filtered by the first capacitor can be further filtered by the second capacitor, unnecessary low-frequency signal components are removed from the high-frequency signal detected by the analog-to-digital converter, that is, low-frequency interference is eliminated, the number of influencing factors is reduced, and the signal-to-noise ratio of the high-frequency signal is improved.
In a possible implementation, the capacitance value of the first capacitor ranges from 1pf to 20 pf.
Therefore, the first capacitor cannot pass through high-frequency signals, burrs and other signals can be filtered, false detection of the analog-to-digital converter is avoided, namely the analog-to-digital converter is prevented from directly detecting unfiltered high-frequency signals containing low-frequency signals and direct-current signals, and the detection accuracy and sensitivity of the analog-to-digital converter can be effectively improved.
In a possible implementation manner, the light sensing chip is further provided with a switch, the switch is electrically connected between the reference voltage port and the second capacitor, and when the switch is turned on, the reference voltage port provides the reference voltage signal for the second capacitor.
It can be understood that the switch is a built-in device of the photosensitive chip, when the analog-to-digital converter does not detect the second capacitor, the switch is turned on to provide a reference voltage signal for the second capacitor, and when the analog-to-digital converter detects the second capacitor, the switch is turned off, so that the problem that when the analog-to-digital converter detects the second capacitor, the second capacitor is influenced by the reference voltage port to cause inaccurate detection result is effectively avoided. So that the signal detected by the analog-to-digital converter is the reference voltage signal and the filtered voltage signal. I.e. the voltage detected by the analog-to-digital converter is the sum of the reference voltage and the voltage of the filtered resistor.
In a second aspect, the present application further provides a laser safety device, laser safety device include the circuit board and as above laser safety circuit, laser safety circuit with the circuit board electricity is connected, the circuit board is equipped with emission module, receiving module and electric capacity, emission module is used for the transmission to detect the light, receiving module is used for receiving by the object to be measured reflection after detect the light in order to acquire the depth information of the object to be measured, emission module includes photosensitive diode, receiving module includes photosensitive chip, electric capacity with photosensitive diode with photosensitive chip electricity is connected.
Therefore, the laser safety equipment acquires the depth information of the object to be measured through the cooperation of the transmitting module and the receiving module. The laser safety equipment is characterized in that the emitting module is controlled to emit modulated light to an object to be detected, namely detection light, the light is reflected by the surface of the object to be detected and then received by the receiving module, the light reflected by the surface of the object to be detected carries depth information of the object to be detected, and the laser safety equipment calculates the phase difference or time difference between the light and the emitting module and the receiving module to convert the phase difference or time difference into the distance between the light and the object to be detected, so that the depth information of the object to be detected is obtained.
In a possible implementation manner, the laser safety device further includes a driving portion, the driving portion is fixed to the circuit board, and the driving portion drives the emission module to start or close according to a start signal or a close signal transmitted by the photosensitive chip.
It can be understood that the driving part may be a Drive IC, so that the consistency between the driving current generated when the driving emitting module operates and the optical power of the detecting light emitted by the emitting module driven by the driving chip is better. Or, the driving part can also be a driving structure composed of a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) tube and a Buffer (Buffer), the driving structure composed of the MOS and the Buffer has high flexibility, different voltages and currents can be selected according to actual conditions, and meanwhile, the driving part is low in cost, can effectively reduce the production cost, and therefore improves the production efficiency. In the embodiment of the application, the structure of the driving part can be selected according to actual conditions, and the flexibility is strong.
In one possible implementation, the emitting module further includes a base, a laser emitter and a light equalizing sheet, the base is provided with an emitting cavity, the laser emitter and the photodiode are all accommodated in the emitting cavity, the laser emitter is used for emitting the detection light, the photodiode is used for monitoring intensity change of the light in the emitting cavity, the received light is converted into a detection electric signal and transmitted to the photosensitive chip, and the light equalizing sheet is fixed on the base and covers the emitting cavity.
From this, set up the light equalizing piece through the top at laser emitter for after laser emitter launches light, the light equalizing piece can enlarge the visual field angle of the transmission visual field of light, with after light diffuses to the external environment through the light equalizing piece, forms the light of the required visual field angle of TOF imaging module, forms high degree of consistency, the good surface light source of directive property promptly. Meanwhile, the light equalizing sheet is arranged, so that the emission energy of the laser emitter can be effectively diffused, the situation that the emission energy is concentrated in a small angle to threaten the personal safety of an object to be detected is avoided, and the safety performance of the laser safety equipment is improved.
In a possible implementation manner, when the detection electrical signal is greater than a preset minimum threshold and less than a preset maximum threshold, the photosensitive chip sends the start signal to the driving portion, so that the driving portion drives the laser emitter to turn on to emit the detection light;
when the detection electric signal is smaller than a preset minimum threshold value or larger than a preset maximum threshold value, the photosensitive chip sends the closing signal to the driving part, so that the driving part drives the laser emitter to close and stop emitting the detection light.
It will be appreciated that the photodiode is capable of passing a correspondingly strong current, i.e. a correspondingly large current signal, depending on the intensity variation of the light within the emission chamber. When the light in the cavity of the emission cavity has no obvious change, the current signal flowing through the photosensitive diode does not change. When the light in the cavity of the emission cavity changes obviously, the current signal flowing through the photosensitive diode changes accordingly. The current signal through the photosensitive diode can be converted into the detection electric signal that can supply the sensitization chip to detect after follow-up change in order to monitor the light change of emission intracavity, thereby make the sensitization chip can be according to the size of detecting the electric signal with the change condition of the light of judging the emission intracavity, and then send corresponding signal and control emission module's operating condition to the drive division, be favorable to when light abnormal change appears, the sensitization chip can drive the drive division and in time close emission module, thereby guarantee the safety of the eyes and the skin of the object of awaiting measuring, be favorable to improving the reliability of laser safety.
The laser safety circuit of the application greatly avoids the situation that the micro current generated by the photosensitive diode irradiated by the ambient light and the dark current generated when the photosensitive diode works are converted into voltage through the resistor by adopting a single-resistor type laser safety scheme in the prior art through arranging the first capacitor and the second capacitor, thereby influencing the output voltage of the laser transmitter, further the problem of judging whether the state of the transmitting module is abnormal or not is interfered, so that the output voltage of the photosensitive diode is not influenced by ambient light and dark current, the flexibility of the laser safety equipment applying the laser safety circuit to different scenes is greatly improved, and the safety threshold of the photosensitive diode is effectively tightened, so that the response precision and sensitivity of the photosensitive diode to the light change condition of the transmitting module can be improved, and the judgment precision of the analog-to-digital converter for judging the abnormal state of the transmitting module is further improved.
Drawings
FIG. 1 is a schematic diagram of the structure of a laser safety device provided herein;
FIG. 2 is a schematic diagram of the TOF imaging module of FIG. 1;
FIG. 3 is a schematic diagram of a transmit module of the TOF imaging module of FIG. 1;
FIG. 4 is a schematic diagram of a receiving module of the TOF imaging module of FIG. 1;
FIG. 5 is a circuit diagram of a prior art laser safety circuit;
fig. 6 is a circuit diagram of a laser safety circuit provided in the present application.
Detailed Description
The following description of the embodiments of the present application will be made with reference to the accompanying drawings.
Referring to fig. 1, the present application provides a laser security device 200 and a laser security circuit 100, where the laser security device 200 related to the present application may be, but is not limited to, a device with a laser emission function, such as a mobile phone, a tablet computer, an electronic reader, a notebook computer, a vehicle-mounted device, or a wearable device. In the embodiment of the present application, the laser safety device 200 is described by taking a mobile phone as an example.
The laser safety device 200 includes a housing 210, a circuit board 220, and a laser safety circuit 100. The circuit board 220 and the laser safety circuit 100 are accommodated in the housing 210, and the circuit board 220 may be a rigid printed circuit board, or a rigid-flexible printed circuit board, or a motherboard of the laser safety device, or a part of the motherboard of the laser safety device. The laser safety circuit 100 is electrically connected to the circuit board 220 to implement a predetermined laser protection function through the circuit board 220, and the specific principle will be further described below.
Referring to fig. 1 and fig. 2, the circuit board 220 is provided with a TOF (time of flight) imaging module 230, and the TOF imaging module 230 is one of 3D (three dimensional) imaging modules, and has a small volume, a long detection distance, a strong adaptability, and less interference from ambient light, and is widely applicable to application scenarios such as face recognition, head portrait unlocking, gesture recognition, object modeling, 3D games, and smart homes.
In the embodiment of the present application, the TOF imaging module 230 includes a transmitting module 240 and a receiving module 250, where the transmitting module 240 is configured to transmit detection light, the receiving module 250 is configured to receive the detection light reflected by the object to be measured, and the laser safety device 200 is configured to obtain depth information of the object to be measured through cooperation of the transmitting module 240 and the receiving module 250. The modulated light, that is, the detection light, is emitted to the object to be detected by controlling the emitting module 240, the light is reflected by the surface of the object to be detected and then received by the receiving module 250, the light reflected by the surface of the object to be detected carries the depth information of the object to be detected, and the laser safety device 200 calculates the phase difference or the time difference between the light from the emitting module 240 and the receiving module 250 to convert the phase difference or the time difference into the distance from the object to be detected, so as to obtain the depth information of the object to be detected.
Referring to fig. 2, the TOF imaging module 230 further includes a driving portion 260, that is, the laser safety device 200 further includes a driving portion 260, and the driving portion 260 is fixed on the circuit board 220 and located between the transmitting module 240 and the receiving module 250, and is used for driving the transmitting module 240 to open or close.
In one possible embodiment, the driving unit 260 is a Drive IC, so that the driving current generated when the driving and emitting module 240 operates and the optical power of the detecting light emitted by the emitting module 240 driven by the driving chip are consistent. In another possible embodiment, the driving portion 260 is a driving structure formed by a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) and a Buffer (Buffer), the driving structure formed by the MOS and the Buffer has high flexibility, different voltages and currents can be selected according to actual conditions, and meanwhile, the driving portion is low in cost, and can effectively reduce production cost, so that production efficiency is improved. In the embodiment of the present application, the configuration of the driving portion 260 may be selected according to actual conditions, and is not particularly limited herein.
Referring to fig. 3, the emission module 240 includes a base 241, a laser emitter 242, a light equalizing sheet 243(diffuser) and a photodiode 10, the base 241 has an emission cavity 244, the laser emitter 242 and the photodiode 10 are accommodated in the emission cavity 244, a positioning groove 245 is formed in an opening at the top of the emission cavity 244, and the light equalizing sheet 243 is fixed to the base 241 by being embedded in the positioning groove 245 and covers the emission cavity 244 to encapsulate the emission cavity 244.
In the embodiment of the present application, the detection light emitted by the emitting module 240 is realized by the emitting function of the laser emitter 242, in other words, the laser emitter 242 is used for emitting the detection light, which can provide a reliable light source requirement for obtaining the depth information, and has a low cost and large-scale mass production. In one possible embodiment, the laser emitter 242 is a Vertical Cavity Surface Emitting Laser (VCSEL) emitting infrared light, and the VCSEL is a small-sized semiconductor laser emitter 242 capable of forming an array distribution with high output power for creating an efficient light source, so that the laser safety device 200 can be adapted to the requirement of miniaturization with a smaller size while meeting the optical power of the light source. In another possible embodiment, the laser emitter 242 is an Edge Emitting Laser (EEL) emitting infrared light, and the EEL is a single-point light emitting structure with high energy, which does not need to design an array structure, is simple to manufacture, and requires a low cost for the light source. When the light source adopts the edge-emitting laser, the method is particularly suitable for the requirement of the light source for human eye safety in the vehicle-mounted laser application scene.
In a specific implementation scenario, the field angle of the emission field of view of the laser emitter 242 is relatively fixed, if the light emitted by the laser emitter 242 is directly projected without diffusion, because the field angle is relatively small and relatively fixed, so that the field angle required by the TOF imaging module 230 is difficult to satisfy, thereby greatly increasing the possibility of insufficient or even failure of obtaining depth information, and because the field angle of the emission field of view of the laser emitter 242 is small, thereby concentrating the emission energy in a small angle, and having potential safety hazard to the eyes and skin of the object to be measured.
From this, set up even light piece 243 through the top at laser emitter 242 for after laser emitter 242 launches light, even light piece 243 can enlarge the visual field angle of the transmission visual field of light, with after light diffuses to the external environment through even light piece 243, form the light of the required visual field angle of TOF imaging module 230, form high degree of consistency, the good surface light source of directive property promptly. Meanwhile, the light homogenizing sheet 243 is arranged, so that the emission energy of the laser emitter 242 can be effectively diffused, the situation that the emission energy is concentrated in a small angle to threaten the personal safety of the object to be detected is avoided, and the safety performance of the laser safety device 200 is improved.
Due to strict requirements on protection of an object to be measured and laser safety, the photodiode 10 is disposed in the emission cavity 244 near the laser emitter 242, and the photodiode 10 is a detection device for laser safety, and can monitor intensity change of light in the emission cavity 244 and convert intensity of the received light into a corresponding current signal for transmission to the receiving module 250, where a magnitude of the current signal is proportional to intensity of the light emitted by the laser emitter 242, in other words, the photodiode 10 can monitor output optical power of the laser emitter 242 to monitor laser safety.
In the embodiment of the present application, the photodiode 10 can determine whether the emission module 240 is abnormal according to the sensed energy, that is, by sensing the change of the light in the emission cavity 244, so as to prepare for subsequent determination and resolution of the abnormal condition of the emission module 240. The abnormal condition of the transmitting module 240 is specifically: the light homogenizing sheet 243 is lost or broken, the emitting power of the laser emitter 242 is too strong or too weak, the external object shields the light emitting side of the light homogenizing sheet 243, so that the emitting window is shielded, and the like. In other words, when the emitting module 240 generates the above-mentioned situation, the light received by the photodiode 10 changes, so that the current signal flowing through the photodiode 10 increases or decreases accordingly, and the photodiode 10 sends the current signal to the receiving module 250 in time, so as to protect the safety of the human eyes and skin of the subject to be tested by controlling the emitting situation of the laser emitter 242 in the following. However, the above-described case is merely an exemplary description for explaining the abnormal case, but the actual abnormal case is not limited to the above-described case.
Referring to fig. 4, in a possible embodiment, the receiving module 250 is a camera module, which includes a lens 251 and a photosensitive chip 20, light reflected by a surface of an object to be measured enters the receiving module 250 through the lens 251 and exits to the photosensitive chip 20, and the photosensitive chip 20 is configured to obtain image information to form a corresponding image signal, which can sense the light passing through the lens 251 to obtain an optical signal and convert the optical signal into a detection electrical signal to implement a photoelectric conversion function. The light sensing chip 20 may be a TOF sensor chip supporting TOF technology, which is capable of transmitting an activation signal or a deactivation signal to the driving part 260, so that the driving part 260 drives the emission module 240 to be activated or deactivated according to the activation signal or the deactivation signal transmitted by the light sensing chip 20.
In the embodiment of the present application, the photodiode 10 can convert the received light into the detection electrical signal and transmit the detection electrical signal to the photosensitive chip 20, and the standard for the photosensitive chip 20 to transmit the start signal or the close signal to the driving portion 260 is the size of the received detection electrical signal. In other words, the photosensitive chip 20 is used for determining the change of the light in the emission cavity 244 according to the magnitude of the detected electrical signal, and further driving the driving portion 260 to control the emission condition of the laser emitter 242 according to the change of the light in the emission cavity 244.
It will be appreciated that the photodiode 10 is capable of passing a correspondingly strong current, i.e. a correspondingly large current signal, depending on the intensity variation of the light within the emission chamber. The current signal through the photodiode 10 does not change when there is no significant change in the light within the cavity of the emission cavity 244. When the light within the cavity of emission chamber 244 changes significantly, the current signal through photodiode 10 changes accordingly.
The current signal passing through the photodiode 10 can be converted into the detection electric signal for the detection of the photosensitive chip 20 after the subsequent change so as to monitor the light change in the emission cavity 244, thereby the photosensitive chip 20 can judge the change condition of the light in the emission cavity 244 according to the size of the detection electric signal, and then the driving part 260 is sent out corresponding signals to control the working state of the emission module 240, which is beneficial to driving the driving part 260 to timely close the emission module 240 when the light is abnormally changed, thereby the safety of eyes and skin of the object to be detected is ensured, and the reliability of laser safety is improved.
In one possible embodiment, in the usage environment of the photodiode 10, the normal range of the detection electrical signal is defined as being between the preset minimum threshold and the preset maximum threshold, and when the detection electrical signal is greater than the preset minimum threshold and less than the preset maximum threshold, the light sensing chip 20 sends an activation signal to the driving portion 260, so that the driving portion 260 drives the laser emitter 242 to turn on to emit the detection light. When the detection electrical signal is smaller than the preset minimum threshold or larger than the preset maximum threshold, the photosensitive chip 20 sends a shutdown signal to the driving part 260, so that the driving part 260 drives the laser emitter 242 to shutdown to stop emitting the detection light. It should be noted that the preset minimum threshold and the preset maximum threshold may be set according to actual situations, and this is not specifically limited in this application.
It can be understood that, when the light equalizing sheet 243 is perfectly embedded in the positioning groove 245, the emitting power of the laser emitter 242 is suitable, and no external object blocks the light emitting side of the light equalizing sheet 243, the light in the emitting cavity 244 does not change significantly, and the current flowing through the photodiode 10 does not change, for this situation, the detection electrical signal detected by the photosensitive chip 20 is also in the normal range of the detection electrical signal, and the photosensitive chip 20 determines that there is no abnormal light change, so that the emission module 240 can be kept turned on, that is, the driving part 260 is continuously sent an on signal, so that the driving part 260 drives the emission module 240 to be continuously turned on, that is, the laser emitter 242 is kept turned on, and can continuously emit detection light. When the light equalizing sheet 243 is damaged or lost, the emitting power of the laser emitter 242 is too strong or too weak, and an external object blocks the light emitting side of the light equalizing sheet 243 to cause the emitting window to be blocked, the light in the emitting cavity 244 changes to cause the light received by the photodiode 10 to change, and once the light received by the photodiode 10 changes, the current flowing through the photodiode 10 also changes to cause the detection electrical signal detected by the photosensitive chip 20 not to be within the normal range of the detection electrical signal, for this situation, the photosensitive chip 20 determines that an abnormal light change occurs, the emitting module 240 needs to be turned off, that is, a turn-off signal is sent to the driving part 260, so that the driving part 260 drives the emitting module 240 to be turned off, that is, the emitting state of the laser emitter 242 is cut off, and the emitting module is in a turn-off state.
In a possible embodiment, the laser safety device 200 further includes a controller (not shown), the controller is housed inside the housing 210 of the laser safety device 200 and electrically connected to the TOF imaging module 230, and the controller is configured to process an image signal of the TOF imaging module 230, where the image signal is a corresponding image signal formed by the photosensitive chip 20 acquiring the image information. The controller may be a master chip on the motherboard of the laser security device 200.
In the embodiment of the present application, the controller includes a processing chip and a memory chip, and the TOF imaging module 230 has a plurality of operating modes (modes). Each working mode is provided with a laser working state, namely the working state of the detection optical signal. The state of the detection optical signal includes the frequency of the pulse wave such as 20mHz (Mega Hertz), 50mHz or 100mHz, the integration time of the pulse wave, the duty cycle of the pulse wave and the corresponding frame rate. For example, when the environment light sensor of the laser safety device 200 determines that the device is in an indoor dim light scene, the transmitting module 240 and the receiving module 250 only need extremely low exposure time and low-precision modulation frequency, so that the distance of the object to be measured can be obtained. In outdoor bright light scenes, the exposure time and the modulation frequency with high precision of the transmitting module 240 and the receiving module 250 need to be increased to improve the signal-to-noise ratio. These different operating modes are aggregated into a corresponding software configuration, which is stored in the form of instructions in the memory chip.
It will be understood that a plurality of instructions capable of being executed by the processing chip are stored in the memory chip. The instructions correspond to a plurality of operating modes of the TOF imaging module 230, respectively. When the processing chip receives a start signal for starting the TOF imaging module 230 of the upper application, the processing chip calls a corresponding instruction in the storage chip according to the start signal and writes the instruction into a register of the photosensitive chip 20, the photosensitive chip 20 sends a corresponding emission signal to the corresponding driving portion 260 according to the instruction, and the driving portion 260 drives the emission module 240 to emit a corresponding detection optical signal according to the emission signal, that is, drives the laser emitter 242 to emit a corresponding detection optical signal. Because different detection optical signals correspond to different working modes, and the working frequencies and the exposure times of the different working modes are different, the laser pulse energy of the detection optical signals is different, and further the average optical power of the detection optical signals is different.
It should be noted that the operating state of the detection optical signal corresponds to the on signal. In a specific implementation scenario, the start signal corresponds to an indoor dim light photographing effect, the corresponding instruction is a first instruction, the processing chip calls the first instruction and writes the first instruction into the register of the photosensitive chip 20, the register switch is turned on and then sends a corresponding emission signal to the driving portion 260, the driving portion 260 drives the emission module 240 to emit a detection optical signal corresponding to the indoor dim light photographing effect according to the emission signal, that is, the driving portion 260 drives the laser emitter 242 to emit a detection optical signal corresponding to the indoor dim light photographing effect.
Referring to fig. 1, fig. 3 and fig. 4, in an embodiment of the present application, a resistor 30, a first capacitor 40 and a second capacitor 50 are further disposed on the circuit board 220. The resistor 30, the first capacitor 40 and the second capacitor 50 are electrically connected with the photodiode 10 and the photosensitive chip 20, so as to form the laser safety circuit 100 of the laser safety device 200, so as to ensure the laser safety of the laser safety device 200, and to be beneficial to ensuring the personal safety of the object to be detected.
As shown in fig. 5, in the conventional laser safety circuit, a PD (Photo diode, 10) receives a part of the light intensity from the laser transmitter and the external environment, and converts the light intensity into a current of a corresponding magnitude. The current can be converted into voltage through the grounded resistor 30R1, and the micro current generated by the PD irradiated by ambient light and the dark current generated by the PD during operation can be converted into voltage through the grounded resistor 30R1, thereby affecting the output voltage of the laser emitter detected by the PD, causing the output voltage of the laser emitter to fluctuate under different scenes, affecting the accuracy of detection of an ADC (Analog-to-Digital Converter 22), interfering the determination of the ADC on the abnormal state of the emission module, and having the conditions of missing detection and false detection, easily causing potential safety hazards, causing the conditions of determining whether the emission power of the laser emitter is abnormal, and determining whether the diffusion sheet and the emission module are shielded, and easily causing false determination.
For example, when the laser safety device is in an outdoor strong light environment, ambient light passes through the PD to generate a large direct current detection electrical signal, and the direct current detection electrical signal is collected by the ADC, so that part of modules biased to the upper limit exceeds an upper threshold of the PD safety threshold, and further causes erroneous judgment.
In view of this, the laser safety circuit 100 provided in the present application can solve the problem that in the existing laser safety circuit 100, the micro-current generated by the PD irradiated by the ambient light and the dark current generated when the PD operates are detected by the ADC, thereby interfering with the judgment of the abnormal state of the emission module, and causing potential safety hazards easily due to the conditions of missing detection and false detection, thereby effectively ensuring the laser safety, and further being beneficial to protecting the safety of eyes and skin of the object to be detected, and the circuit structure and principle of the laser safety circuit 100 will be further described below.
Referring to fig. 6, the laser safety circuit 100 includes a photodiode 10, a resistor 30, a first capacitor 40, a second capacitor 50, and a photo sensor chip 20, wherein the photo sensor chip 20 has a reference voltage port 21 and an analog-to-digital converter 22.
The photodiode 10 is used for monitoring the intensity change of the light in the emission cavity 244 of the emission module and passing a current signal with corresponding magnitude according to the intensity change of the light; the current signal with corresponding magnitude is converted into a voltage signal with corresponding magnitude through the resistor 30; the second capacitor 50 is used for cooperating with the first capacitor 40 to filter low-frequency signals and direct-current signals in the voltage signals; the reference voltage port 21 is used for providing a reference voltage signal to the second capacitor 50; the analog-to-digital converter 22 is used to detect the reference voltage signal and the filtered voltage signal of the second capacitor 50.
It can be understood that the reference voltage port 21 can provide a reference voltage signal for the second capacitor 50, and the current signal of the photodiode 10 is converted into a voltage signal of a corresponding magnitude through the resistor 30, since the micro-current generated by the ambient light illuminating the photodiode 10 is a low-frequency signal, and the dark current when the photodiode 10 operates is a dc signal, these two interference signals will be filtered and will not be detected by the analog-to-digital converter 22 when passing through the first capacitor 40 and the second capacitor 50, and thus the voltage signal received by the second capacitor 50 is actually the sum of the filtered voltage signal and the reference voltage signal. That is, the above-mentioned detection electrical signal is the sum of the reference voltage signal of the second capacitor 50 detected by the analog-to-digital converter 22 and the filtered voltage signal, so as to control the emission of the laser transmitter according to the detection value.
By arranging the first capacitor 40 and the second capacitor 50, the problem that the micro current generated by the photodiode 10 when the ambient light irradiates and the dark current generated when the photodiode 10 works are both converted into voltage through the resistor 30 to affect the output voltage of the laser emitter 242 due to the single-resistor type laser safety scheme adopted in the prior art is greatly avoided, further, the problem of determining whether the state of the transmitting module 240 is abnormal is disturbed, so that the output voltage of the photodiode 10 is not affected by ambient light and dark current, the flexibility of the laser safety device 200 applying the laser safety circuit 100 to different scenes is greatly increased, and the safety threshold of the photodiode 10 is effectively tightened, the response accuracy and sensitivity of the photodiode 10 to the light change condition of the emission module 240 can be improved, thereby improving the accuracy of the adc 22 in determining the abnormal state of the transmitting module 240.
In one possible embodiment, one end of the photodiode 10 is connected to the operating Voltage (VDD), the other end of the photodiode 10 is connected to one end of the resistor 30, one end of the first capacitor 40 and one end of the second capacitor 50, the other end of the resistor 30 is connected to ground, the other end of the first capacitor 40 is connected to ground, and the other end of the second capacitor 50 is connected to the reference voltage port 21 and the analog-to-digital converter 22.
It can be understood that, since the other end of the resistor 30 is grounded, after the photodiode 10 is connected to the operating voltage, the resistor 30 has a voltage to ground, and the voltage to ground is actually a potential difference between the resistor 30 and the ground, i.e. the voltage signal described above. While the photodiode 10 is a photosensitive device, it can be seen from the photosensitive characteristic of the photodiode 10 that when the intensity of the light in the emission cavity 244 is not changed, the current signal flowing through the photodiode 10 is not changed, and thus the voltage to ground of the resistor 30 is not changed, in other words, the voltage signal is not changed. When the intensity of light in the emission cavity 244 changes, the current signal flowing through the photodiode 10 changes, and the voltage to ground of the resistor 30 changes, i.e., the voltage signal changes. For example, when the intensity of light increases, the current signal flowing through the photodiode 10 increases, and thus the converted voltage signal increases, whereas when the intensity of light decreases, the current signal decreases, and thus the converted voltage signal decreases. In the design process of the laser safety circuit 100, the resistance of the resistor 30 can be designed with reference to the detection range of the analog-to-digital converter 22 and the voltage value of the working voltage, and the range of the output voltage of the photodiode 10 can be conveniently and flexibly enlarged and reduced to match the measuring range of the analog-to-digital converter 22 by adjusting the resistance of the resistor 30. For example, when the voltage of the working voltage is 3.3V, the sampling range of the analog-to-digital converter 22 can be increased by 1 time by replacing the resistor with a resistance of 1k Ω (ohm) with the resistor with a resistance of 2k Ω (ohm), so as to flexibly match the measuring range of the analog-to-digital converter 22.
In the embodiment of the present application, the analog-to-digital converter 22 collects the voltage signals filtered by the first capacitor 40 and the second capacitor 50, that is, collects the voltage to ground of the filtered resistor 30, so as to determine whether there is an abnormal change in the light in the emission cavity 244 where the photosensitive element is located according to the change of the voltage to ground of the filtered resistor 30. The voltage signal is filtered by arranging the first capacitor 40 and the second capacitor 50, specifically, the first capacitor 40 and the second capacitor 50 are matched, so that low-frequency signals and direct-current signals which are useless for signal to noise ratio are filtered, the purpose of eliminating interference is achieved, and the detection precision of the analog-to-digital converter 22 is improved. Meanwhile, the signal from which the dc component is removed only contains an effective ac signal, so that the amount of the overall input offset signal is reduced, which is beneficial to further improving the detection accuracy of the analog-to-digital converter 22.
In addition, the reference voltage port 21 is added to provide an offset for the detection of the analog-to-digital converter 22 by the reference voltage port 21. The problem that the range of the analog-to-digital converter 22 is limited, so that the flexible adaptation to various conditions cannot be realized is effectively solved. In addition, during mass production, the size of the reference voltage port 21 can be finely adjusted in the calibration process to counteract the problems of different module assemblies, individual differences of laser emitters and the like.
It can be understood that, for the analog-to-digital converters 22 with different measurement ranges, the reference voltage ports 21 with different voltage values can be adopted to supply the second capacitor 50, so that the voltage value of the reference voltage port 21 is flexibly adjusted to adapt to the appropriate voltage interval of the analog-to-digital converter 22, the detection range of the analog-to-digital converter 22 can be effectively matched, the sampling detection precision of the analog-to-digital converter 22 is optimized, the detection stability is improved, the subsequent detection of the analog-to-digital converter 22 is facilitated, and the flexibility of different laser safety devices and different scenes applying the laser safety circuit is greatly increased. For example, the detection accuracy of the analog-to-digital converter 22 is the best sensitivity in the middle of the detection range, so the setting of the reference voltage port 21 enables the analog-to-digital converter 22 to adjust to a suitable measurement area, so that the measured signal is in the best range of the analog-to-digital converter 22, thereby ensuring the sensitivity and accuracy of the test.
In the embodiment of the present application, the first capacitor 40 is a low-pass capacitor, and the low-pass capacitor can allow signals below the preset cutoff frequency to pass through, and prevent signals above the preset cutoff frequency from passing through. By providing the first capacitor 40 and grounding it, the low frequency signal which is not beneficial to the signal-to-noise ratio is grounded due to its low pass characteristic, thereby preventing the low frequency signal from oscillating and affecting the detection accuracy of the analog-to-digital converter 22. Meanwhile, the characteristic of preventing the high-frequency signal from passing through enables the filtered high-frequency signal to be successfully detected by the analog-to-digital converter 22, and the accuracy of the detected object is effectively guaranteed.
The capacitance value of the first capacitor 40 ranges from 1pf to 20 pf. The high-frequency signal cannot pass through the analog-to-digital converter 22, and the signals such as the glitch can be filtered, so that the false detection of the analog-to-digital converter 22 is avoided, that is, the high-frequency signal which is not filtered and contains the low-frequency signal and the direct-current signal is avoided being directly detected by the analog-to-digital converter 22, and the detection precision and the sensitivity of the analog-to-digital converter 22 can be effectively improved. In one possible embodiment, the capacitance of the first capacitor 40 is 10 pf.
The second capacitor 50 is a high-pass capacitor capable of allowing signals above a predetermined cutoff frequency to pass therethrough and preventing signals below the predetermined cutoff frequency from passing therethrough. The second capacitor 50 is connected to the analog-to-digital converter 22, so that the high-pass characteristic of the second capacitor 50 can greatly attenuate signals with lower frequencies, low-frequency signals and direct-current signals which are not filtered by the first capacitor 40 can be further filtered by the second capacitor 50, unnecessary low-frequency signal components are removed from the high-frequency signals detected by the analog-to-digital converter 22, that is, low-frequency interference is eliminated, the number of influencing factors is reduced, and the signal-to-noise ratio of the high-frequency signals is improved.
The existence of the first capacitor 40 and the second capacitor 50 enables low-frequency signals and direct-current signals such as ambient light, dark current, noise and the like to be filtered, at the moment, the deviation signal quantity input by the photodiode 10 integrally is reduced, and because the influence of the ambient light, the noise and the like is not needed to be considered, the safety threshold range of the current flowing through the photodiode 10 is not needed to be further amplified and is reserved with allowance to avoid error touch, namely, the safety threshold range can be reduced, so that the safety threshold range of the receiving module 250 is reduced, the sensitivity of the intensity change of the light in the transmitting cavity 244 detected by the photodiode 10 is increased, and the consistency of the laser safety equipment 200 applying the laser safety circuit 100 is ensured. Meanwhile, if the light in the emitting cavity 244 changes, the photosensitive chip 20 can respond in time to turn off the emission of the laser emitter.
In one possible embodiment, the light sensing chip 20 is further provided with a switch, the switch is electrically connected between the reference voltage port 21 and the second capacitor 50, and when the switch is turned on, the reference voltage port 21 provides a reference voltage signal for the second capacitor 50. It can be understood that the switch is a built-in device of the light sensing chip 20, when the analog-to-digital converter 22 does not detect the second capacitor 50, the switch is turned on to provide the reference voltage signal for the second capacitor 50, and when the analog-to-digital converter 22 detects the second capacitor 50, the switch is turned off, so as to effectively avoid the problem that the detection result is inaccurate due to the influence of the reference voltage port 21 on the second capacitor 50 when the analog-to-digital converter 22 detects the second capacitor 50. So that the signal detected by the analog-to-digital converter 22 is the reference voltage signal and the filtered voltage signal. I.e. the voltage detected by the analog-to-digital converter 22 is the sum of the reference voltage and the filtered voltage of the resistor 30.
In the embodiment of the application, different detection optical signals correspond to different working modes, and the working frequencies and the exposure times of the different working modes are different, so that the laser pulse energy of the detection optical signals is different, and further the average optical power of the detection optical signals is different. The photodiode 10 detects the light variation in the emission cavity 244 to convert the optical signal of the light into an electrical detection signal for the analog-to-digital converter 22 to detect, the light variation including the average optical power of the detection light. Since the analog-to-digital converter 22 adopts the integral detection principle to detect, the threshold ranges of the voltages output by the photodiodes 10 are different for the detection optical signals of different working modes, so that the method can be applied to different scenes, and the flexibility and the universality of the application are greatly improved.
The laser safety circuit 100 of the present application is provided with the first capacitor 40 and the second capacitor 50, thereby greatly avoiding the single-resistor type laser safety scheme adopted in the prior art, the micro current generated by the light irradiating the photodiode 10 under the caused ambient light and the dark current generated when the photodiode 10 works can be converted into voltage through the resistor 30, thereby affecting the output voltage of the laser emitter 242, and further interfering with the problem of judging whether the state of the emitting module 240 is abnormal, so that the output voltage of the photodiode 10 can not be affected by the ambient light and the dark current, thereby greatly increasing the flexibility of the laser safety device 200 applying the laser safety circuit 100 to different scenes, and effectively tightening the safety threshold of the photodiode 10, thereby improving the response precision and the sensitivity of the photodiode 10 to the light change condition of the emitting module 240, and further improving the flexibility of the analog-to-digital converter 22 to judge the abnormal state of the emitting module 240 according to the current change condition of the photodiode 10 And judging the state.
The foregoing detailed description of the embodiments of the present application has been presented to illustrate the principles and implementations of the present application, and the above description of the embodiments is only provided to help understand the method and the core concept of the present application; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (10)
1. A laser safety circuit is characterized by comprising a photosensitive diode, a resistor, a first capacitor, a second capacitor and a photosensitive chip, wherein the photosensitive chip is provided with a reference voltage port and an analog-to-digital converter;
the photosensitive diode is used for monitoring the intensity change of light rays in the emission cavity of the emission module and passing current signals with corresponding magnitude according to the intensity change of the light rays; the current signal with the corresponding magnitude is converted into a voltage signal with the corresponding magnitude through the resistor; the second capacitor is used for being matched with the first capacitor to filter low-frequency signals and direct-current signals in the voltage signals; the reference voltage port is used for providing a reference voltage signal to the second capacitor; the analog-to-digital converter is used for detecting the reference voltage signal of the second capacitor and the filtered voltage signal.
2. The laser safety circuit as claimed in claim 1, wherein one end of the photodiode is connected to an operating voltage, the other end of the photodiode is connected to one end of the resistor, one end of the first capacitor and one end of the second capacitor, the other end of the resistor is connected to ground, the other end of the first capacitor is connected to ground, and the other end of the second capacitor is connected to the reference voltage port and the analog-to-digital converter.
3. The laser safety circuit as claimed in claim 2, wherein the first capacitor is a low-pass capacitor capable of allowing signals below a predetermined cut-off frequency to pass therethrough and preventing signals above the predetermined cut-off frequency from passing therethrough.
4. The laser safety circuit of claim 2, wherein the second capacitor is a high-pass capacitor capable of allowing signals above a predetermined cutoff frequency to pass therethrough and preventing signals below the predetermined cutoff frequency from passing therethrough.
5. The laser safety circuit of claim 3, wherein the first capacitor has a capacitance in the range of 1pf to 20 pf.
6. The laser safety circuit as claimed in claim 2, wherein said photo-sensing chip is further provided with a switch electrically connected between said reference voltage port and said second capacitor, said reference voltage port providing said reference voltage signal to said second capacitor when said switch is turned on.
7. A laser safety device, characterized in that, the laser safety device includes a circuit board and the laser safety circuit of any one of claims 1-5, the laser safety circuit is electrically connected with the circuit board, the circuit board is provided with a transmitting module, a receiving module, the resistor, the first capacitor and the second capacitor, the transmitting module is used for transmitting detection light, the receiving module is used for receiving the detection light reflected by an object to be detected so as to obtain depth information of the object to be detected, the transmitting module includes the photosensitive diode, the receiving module includes the photosensitive chip, and the resistor, the first capacitor and the second capacitor are electrically connected with the photosensitive diode and the photosensitive chip.
8. The laser safety device as claimed in claim 7, further comprising a driving part fixed to the circuit board, wherein the driving part drives the emission module to start or stop according to a start signal or a stop signal transmitted by the photosensitive chip.
9. The laser safety device of claim 8, wherein the emitting module further comprises a base, a laser emitter and a light equalizing sheet, the base is provided with an emitting cavity, the laser emitter and the photodiode are both accommodated in the emitting cavity, the laser emitter is configured to emit the detection light, the photodiode is configured to monitor intensity change of light in the emitting cavity and convert the received light into a detection electrical signal to be transmitted to the photosensitive chip, and the light equalizing sheet is fixed to the base and covers the emitting cavity.
10. The laser safety device according to claim 9, wherein when the detection electrical signal is greater than a preset minimum threshold value and less than a preset maximum threshold value, the photosensitive chip sends the activation signal to the driving portion, so that the driving portion drives the laser emitter to turn on to emit the detection light;
when the detection electric signal is smaller than a preset minimum threshold value or larger than a preset maximum threshold value, the photosensitive chip sends the closing signal to the driving part, so that the driving part drives the laser emitter to close and stop emitting the detection light.
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