Self-synchronizing secret photography prevention light source design method

Abstract

The invention provides a self-synchronizing secret photography prevention light source design method, and belongs to the technical field of visible light communication. According to the design method of the anti-candid photographing light source, a self-synchronizing anti-candid photographing light source is designed, the characteristic that image pixels captured by a rolling shutter camera are exposed line by line is utilized, and the flickering frequency and phase of the light source are adjusted when the camera is exposed line by line, so that black stripes appear on a photographed image, and the black stripes shield the photographed image; finally, the purpose of preventing candid photography is achieved. The anti-candid light source comprises a master lamp and a slave lamp, the master lamp is connected with a master lamp single-chip microcomputer, the slave lamp is connected with a slave lamp single-chip microcomputer, the master lamp and the slave lamp are driven by the corresponding single-chip microcomputers to synchronously flicker, and the flicker frequencies and phases of the master lamp and the slave lamp are completely consistent. According to the invention, the video recorded by the camera equipment has periodic stripes, so that illegal video recording is avoided; the light source is low in cost, high in reliability and capable of keeping light intensity output; synchronous flickering of the light source can be achieved, and the purpose of preventing candid shooting is achieved.

Description

Technical Field

[0001] This invention belongs to the field of visible light communication technology, specifically the design of light source emission signals, and relates to a self-synchronizing anti-spy camera light source design method. Background Technology

[0002] With the widespread use of photographic equipment, many technologies are dedicated to interfering with these devices through various means to prevent unauthorized recording or protect privacy. Most digital cameras on the market today use rolling shutters to achieve high frame rates; images captured by rolling shutter cameras are generated line by line of pixels. Several teams have exploited this characteristic by varying the light intensity as the camera scans line by line, causing the recorded video to display stripes.

[0003] Currently, methods to combat illegal recording primarily involve affecting the camera's optical sensor without being detected by the human eye, such as through high-frequency flickering. This reduces the camera's visual sensitivity, disrupts image quality, and makes facial and other image information unrecognizable or obscured during recording. However, with advancements in lighting and imaging technologies, traditional PWM dimming technology has inherent drawbacks, including high switching losses, low efficiency, and ripple in the output current. Furthermore, while current anti-spy camera devices on the market offer both illumination and camera interference capabilities, they still struggle to effectively manage both in complex indoor environments.

[0004] Compared with the original method, the present invention can not only meet the indoor lighting needs, but also achieve effective interference with camera equipment at low cost. Summary of the Invention

[0005] The technical problem to be solved by this invention is that in traditional anti-spy camera methods, lighting equipment designed using dimming technologies such as PWM has high power consumption and cannot meet more complex dimming requirements. Furthermore, it is difficult for a single device to simultaneously meet the dual requirements of effectively interfering with camera equipment and ensuring sufficient indoor lighting. This invention provides a self-synchronizing anti-spy camera light source design method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A self-synchronizing anti-spy camera light source design method is proposed. The method utilizes the characteristic of a rolling shutter camera to capture image pixels through line-by-line exposure. By adjusting the frequency and phase of the light source's flicker during line-by-line exposure, black stripes appear in the captured image. These black stripes obscure the captured image, ultimately achieving the purpose of preventing spy camera exposure.

[0008] The anti-spy camera light source includes a main light and slave lights. The main light is connected to a main light microcontroller, and the slave lights are connected to slave light microcontrollers. The main and slave lights flash synchronously under the drive of their respective microcontrollers, and their flashing frequencies and phases are completely identical. Specifically, the main light microcontroller generates a PWM signal through its timer function. By adjusting the frequency and duty cycle of this PWM signal, the flashing frequency of the main light is kept within the interference range of the camera's shutter speed, thus causing the image captured by the camera to display black stripes. A photodiode is installed on one side of the slave light. This photodiode senses the flashing light signal of the main light and generates a corresponding current. The current is converted into an electrical signal by a photoelectric conversion amplifier circuit and then transmitted to the slave light microcontroller for processing. After receiving the electrical signal, the slave light microcontroller accurately captures the rising and falling edges of the electrical signal (i.e., timestamps) through a timer input capture mode and directly stores the timestamps into memory via DMA (Direct Memory Access). Based on the stored timestamps, the frequency and duty cycle of the electrical signal are calculated. The microcontroller of the slave lamp precisely controls the PWM signal output to the slave lamp according to the calculation results, ensuring that the flashing of the master lamp and the slave lamp is synchronized. The self-synchronizing anti-spy camera light source design method provided by this invention includes the following steps:

[0009] Step 1: The main light uses LED lights. The main light microcontroller is configured to work in PWM mode through its internal timer module to generate a stable and accurate PWM signal. This PWM signal is used to control the flashing frequency and brightness of the main light.

[0010] Specifically, by configuring the parameters of the prescaler and auto-reload register of the timer module, the counting period of the timer is precisely controlled, thereby determining the period of the PWM signal and achieving precise setting of the main light flashing frequency; by adjusting the parameters of the comparison register in the timer module, the duration of the high level of the PWM signal is controlled, thereby achieving precise adjustment of the PWM signal duty cycle.

[0011] Considering that the shooting frame rate of a conventional camera is usually 30FPS, the flashing frequency of the main LED light is selected to be an integer multiple of 30Hz, and this flashing frequency is higher than the frequency threshold that the human eye can perceive.

[0012] Step 2: The slave lamp uses the same LED as the main lamp, and a photodiode is used as the light signal receiving element of the slave lamp to receive the flashing light signal emitted by the main lamp and convert the light signal into a weak current signal that is proportional to the light intensity.

[0013] Step 3: The weak current signal output from Step 2 is processed by the amplifier circuit module. First, it is converted into a voltage signal, and then the voltage signal is amplified by the amplifier circuit composed of cascaded operational amplifiers, so that the voltage signal amplitude is increased to a range suitable for the acquisition of the microcontroller's ADC or digital input.

[0014] Furthermore, the amplifier circuit module includes a three-stage amplifier circuit: the first-stage amplifier circuit uses a T-type feedback network to adjust the signal gain; the second-stage amplifier circuit is an inverting amplifier circuit, which can significantly expand the detectable range of the signal; the third-stage amplifier circuit uses a high-performance operational amplifier to construct a subtractor circuit in the differential structure, which is used to perform zero-point adjustment and bias voltage correction on the voltage signal after the first two stages of amplification, so as to adapt to the input requirements of the subsequent signal acquisition module.

[0015] Furthermore, the operational amplifier includes types such as transimpedance amplifiers.

[0016] Step 4: The voltage signal amplified in Step 3 is acquired and processed using a microcontroller. The specific process is as follows:

[0017] Step 4.1: Configure the microcontroller's single timer input channel to simultaneously capture the rising and falling edges of a signal (i.e., timestamps); continuously receive alternating rising and falling edge timestamps via DMA, and distinguish the high and low levels of the voltage signal based on the parity of the captured timestamps. Odd-numbered timestamps correspond to rising edges, and even-numbered timestamps correspond to falling edges.

[0018] Step 4.2: Select three consecutively captured timestamps, with the first timestamp being an odd-numbered sequence. Let these three consecutive timestamps be t1 (odd-numbered rising edge), t2 (even-numbered falling edge), and t3 (odd-numbered rising edge). Then, the high-level width of the voltage signal can be calculated. and cycle Then the duty cycle of the voltage signal can be calculated. and frequency ;

[0019] Step 4.3: When the next rising edge of the voltage signal arrives, control the output of a PWM signal with the same frequency and duty cycle as the above calculation result from another pin of the microcontroller of the lamp, so as to ensure that the flashing frequency and phase of the main lamp and the slave lamp remain synchronized.

[0020] Step 5:

[0021] A reed relay is used as the switching element of the master-slave lamp system. Through the on and off action of the reed relay, the switching control of the slave lamp's on and off state is fully controllable during the operation of the master lamp's flashing signal output, ensuring that the slave lamp can accurately respond to the master lamp's flashing signal and complete the corresponding on and off action.

[0022] The anti-spy camera light source adopts a master-slave light system design. The master LED generates a PWM signal through a microcontroller to interfere with the camera equipment's shooting. The photodiode receives the light signal from the master LED and converts the light signal into a voltage signal through the slave LED's microcontroller, so that the slave LED and the master LED flash synchronously. Ultimately, the anti-spy camera effect is achieved while meeting the lighting requirements.

[0023] The beneficial effects of this invention are as follows:

[0024] (1) The present invention can adjust the emission frequency and phase of the designed light source so that the video recorded by the camera device has periodic stripes, thereby avoiding illegal recording. At the same time, the light source is low in cost, highly reliable, and can maintain light intensity output without affecting the normal lighting needs of the room. In addition, the flicker frequency is precisely designed to ensure that the human eye cannot detect the flicker of the light source, achieving a concealed anti-spy camera effect.

[0025] (2) The design method of this invention can obtain a self-synchronizing anti-spy camera light source. By precisely controlling the frequency and duty cycle of the output signal through a master-slave control system, the light source can be synchronously flickered, effectively interfering with the camera equipment and causing the captured image or video to show interference stripes, thereby achieving the purpose of anti-spy camera. At the same time, it meets the indoor lighting requirements and ensures that the flickering of the light source is not perceptible to the human eye. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the interference stripe effect achieved by the self-synchronized anti-spy camera light source of the present invention.

[0027] Figure 2 This is a general block diagram of the slave lamp part of the self-synchronizing anti-spy camera light source of the present invention.

[0028] In the diagram: 1. The frame of the photo taken by the hidden camera; 2. The object being photographed; 3. Interference stripes captured under the illumination of the anti-hidden camera light source; 4. Photodiode; 5. Amplifier circuit; 6. Acquisition module from the lamp microcontroller; 7. PWM signal output module from the lamp microcontroller; 8. Light source. Detailed Implementation

[0029] The self-synchronizing anti-spy camera light source design method provided by this invention includes the following steps:

[0030] Step 1: The main light uses an HW-269 LED light, and the main light microcontroller is an STM32F103C8T6 microcontroller. The PWM working mode is configured through its internal timer module to generate a stable and accurate PWM signal. This PWM signal is used to control the flashing frequency and brightness of the main light.

[0031] By configuring the parameters of the prescaler and auto-reload register of the timer module, the counting period of the timer is precisely controlled, thereby determining the period of the PWM signal and achieving precise setting of the main light flashing frequency; by adjusting the parameters of the comparison register in the timer module, the duration of the high level of the PWM signal is controlled, thereby achieving precise adjustment of the PWM signal duty cycle. In the experiment, the duty cycle of the PWM signal was determined to be 20%.

[0032] Considering that the shooting frame rate of a conventional camera is usually 30FPS, the flashing frequency of the main LED light is selected to be an integer multiple of 30Hz, and this flashing frequency is higher than the frequency threshold that the human eye can perceive. In the experiment, the flashing frequency was determined to be 60Hz.

[0033] Step 2: The light source 8 uses the same LED as the main light, and the 2CU8300 silicon photodiode 4 is used as the light signal receiving element of the slave light to receive the flashing light signal emitted by the main light and convert the light signal into a weak current signal that is proportional to the light intensity.

[0034] Step 3: The weak current signal output from Step 2 is processed by amplifier circuit module 5. First, it is converted into a voltage signal using a JFET-type AD825 chip. Then, the voltage signal is amplified by an amplifier circuit composed of cascaded operational amplifiers, increasing the voltage signal amplitude to a range suitable for microcontroller ADC acquisition or digital input, i.e., 2V~5V. The amplifier circuit selected is an IV conversion circuit with a T-type feedback network, model YK-IV120K100.

[0035] In this embodiment, the amplification circuit module includes a three-stage amplification circuit: the first-stage amplification circuit uses a T-type feedback network to adjust the signal gain; the second-stage amplification circuit is an inverting amplification circuit, which can significantly expand the detectable range of the signal; the third-stage amplification circuit uses a high-performance operational amplifier to construct a subtractor circuit in the differential structure, which is used to perform zero-point adjustment and bias voltage correction on the voltage signal after the first two stages of amplification, so as to adapt to the input requirements of the subsequent signal acquisition module.

[0036] In this embodiment, the operational amplifier includes types such as transimpedance amplifiers.

[0037] Step 4: The voltage signal amplified in Step 3 is acquired and processed using an STM32F103C8T6 microcontroller. The specific process is as follows:

[0038] Step 4.1: Configure the microcontroller's single timer input channel to simultaneously capture the rising and falling edges of a signal (i.e., timestamps); continuously receive alternating rising and falling edge timestamps via DMA (here, 6 timestamps), and distinguish the high and low levels of the voltage signal based on the parity of the captured timestamps. Odd-numbered timestamps correspond to rising edges, and even-numbered timestamps correspond to falling edges.

[0039] Step 4.2: Select three consecutively captured timestamps, with the first timestamp being an odd-numbered sequence. Let these three consecutive timestamps be t1 (odd-numbered rising edge), t2 (even-numbered falling edge), and t3 (odd-numbered rising edge). Then, the high-level width of the voltage signal can be calculated. and cycle Then the duty cycle of the voltage signal can be calculated. and frequency ;

[0040] Step 4.3: When the next rising edge of the voltage signal arrives, the other pin of the microcontroller controlling the lamp outputs a PWM signal with the same frequency and duty cycle as calculated above, which is 7 in this case, to ensure that the flashing frequency and phase of the main lamp and the slave lamp remain synchronized.

[0041] Step 5:

[0042] The SIP-1A05 reed relay is used as the switching element of the master-slave lamp system. Through the on and off action of the reed relay, the switching control of the slave lamp's on and off state is fully controllable during the operation of the master lamp's flashing signal output, ensuring that the slave lamp can accurately respond to the master lamp's flashing signal and complete the corresponding on and off action.

[0043] The anti-spy camera light source adopts a master-slave light system design. The master LED generates a PWM signal through a microcontroller to interfere with the camera equipment's shooting. The photodiode receives the light signal from the master LED and converts the light signal into a voltage signal through the slave LED's microcontroller, so that the slave LED and the master LED flash synchronously. Finally, under the condition of meeting the lighting requirements, the anti-spy camera effect is achieved. Periodic black stripes 3 appear in the camera video 1, and the object being photographed 2 is successfully blocked.

[0044] The above embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A self-synchronized anti-spy light source design method, characterized in that, The anti-stealing light source design method is to design a self-synchronous anti-stealing light source, utilize the feature that the image pixels are exposed line by line by a rolling shutter camera, adjust the frequency and phase of the light source flicker when the camera exposes line by line, make the captured image appear black stripes, the black stripes block the shooting picture, and finally achieve the purpose of anti-stealing; The anti-stealing light source comprises a main light and a slave light, wherein the main light is connected with a main light single-chip microcomputer, the slave light is connected with a slave light single-chip microcomputer, the main light and the slave light realize synchronous flicker under the driving of the corresponding single-chip microcomputers, and the flicker frequency and phase of the two are completely consistent.

2. A self-synchronized anti-spy light source design method according to claim 1, characterized in that, The synchronous flicker mode of the main light and the slave light is as follows: The main light single-chip microcomputer generates a PWM signal through its timer function, adjusts the frequency and duty cycle of the PWM signal, makes the flicker frequency of the main light in the interference range of the shutter speed of the camera equipment, and further makes the image captured by the camera equipment present black stripes; The slave light side is provided with a photodiode for sensing the flicker light signal of the main light and generating a corresponding current, and the current is converted into an electrical signal and transmitted to the slave light single-chip microcomputer for processing after conversion; After receiving the electrical signal, the slave light single-chip microcomputer accurately captures the occurrence time of the rising edge and the falling edge of the electrical signal through the timer input capture mode, that is, the time stamp, and directly stores the time stamp into the memory through direct memory access (DMA); Based on the stored time stamp, the frequency and duty cycle of the electrical signal are calculated, and the slave light single-chip microcomputer accurately controls the PWM signal output to the slave light according to the calculation result, to ensure the synchronous flicker of the main light and the slave light.

3. A self-synchronized anti-spying light source design method according to claim 2, characterized in that, The self-synchronous anti-stealing light source design method comprises the following steps: Step one: the main light adopts an LED lamp, and the main light single-chip microcomputer configures a PWM working mode through its internal timer module to generate a stable and accurate PWM signal for controlling the flicker frequency and brightness of the main light; Step two: the slave light adopts the same LED lamp as the main light, and a photodiode is used as the light signal receiving element of the slave light for receiving the flicker light signal emitted by the main light and converting the light signal into a weak current signal proportional to the light intensity; Step three: the weak current signal output in step two is processed through an amplification circuit module, which first converts it into a voltage signal, and then amplifies the voltage signal through an amplification circuit composed of an operational amplifier in cascade to raise the voltage signal amplitude to the range suitable for single-chip microcomputer ADC acquisition or digital input; Step four: the voltage signal amplified in step three is collected and processed by the single-chip microcomputer, specifically as follows: Step 4.1: configure the single timer input channel of the single-chip microcomputer to make it have the function of simultaneously capturing the occurrence time of the rising edge and the falling edge, and define the occurrence time as a time stamp; continuously receive the alternately appearing rising edge time stamp and falling edge time stamp through DMA, and distinguish the time of high and low voltage signal according to the odd and even serial numbers of the captured time stamps; wherein the odd position time stamp corresponds to the rising edge time, and the even position time stamp corresponds to the falling edge time. Step 4.2: Select three consecutive timestamps, the first timestamp is odd number, and the three consecutive timestamps are t1, t2, t3 in turn, wherein t1 is an odd number rising edge, t2 is an even number falling edge, and t3 is an odd number rising edge; the high level width of the voltage signal is calculated and period , and then the duty cycle and frequency of the voltage signal are calculated; Step 4.3: when the next rising edge of the voltage signal comes, the control outputs a PWM signal with the same frequency and duty cycle as the calculation result from the slave light single-chip microcomputer, ensuring that the flicker frequency and phase of the master light and the slave light are synchronized; Step five: The dry reed relay is used as the switching element of the master-slave light system, and through the on-off action of the dry reed relay, the slave light can be completely controlled to switch between on and off states during the working process of the master light outputting the flicker signal, ensuring that the slave light can accurately respond to the master light flicker signal and complete the corresponding on-off action. The anti-stealing light source adopts the design of a master-slave light system, the master light LED generates a PWM signal through a single-chip microcomputer to interfere with the shooting of a camera device, a photodiode receives the light signal of the master light, and the light signal is converted into a voltage signal through a slave light single-chip microcomputer to realize the synchronous flicker of the slave light and the master light, finally achieving the anti-stealing effect under the condition of meeting the lighting requirements.

4. A self-synchronized anti-spying light source design method according to claim 3, characterized in that, In step one, the counting period of the timer is accurately controlled by configuring the parameters of the pre-divider and the automatic reload register of the timer module, and then the period of the PWM signal is determined to realize the accurate setting of the flicker frequency of the master light; by adjusting the parameters of the comparison register in the timer module, the duration of the high level of the PWM signal is controlled to realize the accurate adjustment of the duty cycle of the PWM signal.

5. A self-synchronized anti-spying light source design method according to claim 3, characterized in that, In step one, the flicker frequency of the master light LED is selected as an integer multiple of 30Hz, and the flicker frequency is higher than the frequency threshold value that can be perceived by the human eye.

6. A self-synchronized anti-spying light source design method according to claim 3, characterized in that, In step three, the amplification circuit module includes three-stage amplification circuits: the first-stage amplification circuit adopts a T-type feedback network for adjusting the signal gain; the second-stage amplification circuit is an inverting amplification circuit that can significantly expand the detectable range of the signal; and the third-stage amplification circuit adopts a high-performance operational amplifier to build a subtractor circuit in a differential structure for zero-point adjustment and bias voltage correction of the voltage signal after the amplification of the previous two stages, to adapt to the input requirements of the subsequent signal acquisition module.

7. A self-synchronized anti-spying light source design method according to claim 3, characterized in that, In step three, the operational amplifier is a transimpedance amplifier.

8. The method of claim 3, wherein the method further comprises: In step 4.2, the high level width of the voltage signal is calculated to be , the period is , the duty cycle of the voltage signal is , and the frequency is .

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