Electronic ND filter based on liquid crystal dimming and control method thereof

Abstract

The application relates to the technical field of optical filters, and discloses an electronic ND filter based on liquid crystal dimming and a control method thereof. The filter comprises a shell, an electronic ND liquid crystal screen and a control circuit. The electronic ND liquid crystal screen is provided with a first liquid crystal dye layer containing dye-doped liquid crystal. The control method comprises the following steps: obtaining a target transmittance gear instruction and mapping a target driving voltage; the control circuit outputs an alternating square wave driving voltage with a positive and negative level maintenance time ratio of 1:1 to the first liquid crystal dye layer; the arrangement angle of liquid crystal molecules is changed to adjust the light transmittance; when the system is not powered, the initial arrangement direction of the liquid crystal molecules is orthogonal to the initial polarization direction of the polarizing film, and the lowest transmittance is output; the filter is provided with a 1 / 4 lambda wave plate clamped between the two liquid crystal dye layers, and the wave plate is used for absorbing internal interface reflected light by using the polarization state conversion effect of the wave plate. The application eliminates the stray reflection of the structural interface, prevents the polarization failure of the liquid crystal molecules, and provides power-off light shielding protection.

Description

Technical Field

[0001] This invention relates to the field of optical filter technology, specifically to an electronic ND filter based on liquid crystal dimming and its control method. Background Technology

[0002] Existing electronic neutral density filters typically adjust light transmittance by applying voltage to change the alignment angle of liquid crystal molecules. When the device power is interrupted or the drive circuit output is zero, the liquid crystal material often reverts to its initial transparent state, causing the system to lose its ability to block light. This exposes the photosensitive component at the back of the filter directly to strong external light, increasing the probability of physical damage from light radiation. To improve the dimming range, some devices employ a multilayer glass substrate and conductive coating stacked structure. When external light continuously penetrates the interface between media with different physical densities, interface reflection occurs. This interlayer reflected light is refracted along the optical path and mixed into the main optical path, causing stray light to be mixed into the output beam. Furthermore, in the continuous operation of existing filter dimming drive circuits, the duration of the positive and negative half-cycles of the output alternating electric field differs. The accumulated DC bias component in the electrical signal applied to both ends of the conductive coating can induce irreversible physical polarization of the liquid crystal molecules, reducing the accuracy of the liquid crystal molecule deflection angle response to the drive voltage and causing deviations in the set transmittance parameters. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an electronic ND filter based on liquid crystal dimming and its control method, which solves the problems of existing electronic ND filters losing physical light shielding protection when powered off, generating reflected stray light at the interface of multilayer structures, and causing liquid crystal molecule polarization failure due to asymmetric driving electric fields.

[0004] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides an electronic ND filter based on liquid crystal dimming, comprising: shell; An electronic ND liquid crystal display screen is disposed in the light-transmitting area of ​​the housing. The electronic ND liquid crystal display screen includes a liquid crystal dimming module, and the liquid crystal dimming module includes at least a first liquid crystal dye layer; the first liquid crystal dye layer contains dye-doped liquid crystal. A control circuit is disposed inside the housing and electrically connected to the liquid crystal dimming module. The control circuit outputs an AC square wave driving voltage to the liquid crystal dimming module to change the alignment direction of the dye-doped liquid crystal molecules.

[0005] Furthermore, the liquid crystal dimming module also includes a polarizing film, the initial polarization direction of which is orthogonal to the initial alignment direction of the dye-doped liquid crystal molecules in the first liquid crystal dye layer; along the incident light direction, the liquid crystal dimming module sequentially includes a first outer glass substrate, the polarizing film, a first inner glass substrate, a first ITO conductive coating, a first guiding film, the first liquid crystal dye layer, a second guiding film, a second ITO conductive coating, and a second outer glass substrate; a sealant is provided between the edges of the first inner glass substrate and the second outer glass substrate, and the first liquid crystal dye layer is sealed between the first inner glass substrate and the second outer glass substrate.

[0006] Furthermore, the liquid crystal dimming module also includes a second liquid crystal dye layer and a 1 / 4λ waveplate. The second liquid crystal dye layer contains dye-doped liquid crystal. The first and second liquid crystal dye layers are stacked along the light transmission direction, and the 1 / 4λ waveplate is disposed between the first and second liquid crystal dye layers. The angle between the polarization direction of the linearly polarized light emitted through the first liquid crystal dye layer and the optical axis of the 1 / 4λ waveplate is 45 degrees. The linearly polarized light that penetrates the first liquid crystal dye layer is converted into circularly polarized light by the 1 / 4λ waveplate. The circularly polarized light is reflected from the interface of the structure containing the second liquid crystal dye layer, its polarization state is reversed, and it is converted back into linearly polarized light by the 1 / 4λ waveplate. The polarization direction of the linearly polarized light after this second conversion is perpendicular to the polarization direction of the linearly polarized light emitted through the first liquid crystal dye layer. The linearly polarized light after this second conversion is absorbed by the dye-doped liquid crystal in the second liquid crystal dye layer. The above-mentioned polarization direction conversion and absorption mechanism realizes the internal filtering of reflected light from the optical path interface.

[0007] Furthermore, the control circuit includes a microcontroller and a 4MOS transistor full-bridge drive circuit electrically connected to the microcontroller; the microcontroller converts the DC power supply into an AC square wave drive voltage with a frequency between 32Hz and 64Hz and a positive-to-negative level time ratio of 1:1 through the 4MOS transistor full-bridge drive circuit, and outputs the AC square wave drive voltage to the liquid crystal dimming module.

[0008] Furthermore, a photosensitive element is provided on the side of the outer casing facing the incident end of external light; the photosensitive element is electrically connected to the control circuit, and the photosensitive element collects ambient light illuminance data and transmits it to the control circuit; the control circuit adjusts the amplitude of the AC square wave driving voltage output to the liquid crystal dimming module according to the ambient light illuminance data.

[0009] Furthermore, the housing has a front and a side; the front is provided with a status display screen; the side is provided with a toggle switch, an upshift button, and a downshift button, the upshift button and the downshift button being located on both sides of the toggle switch; the side is also provided with multiple gear indicator lights, the multiple gear indicator lights being arranged along the contour edge of the side; the side is also provided with a power switch, a power indicator light, and a TYPE-C charging port, arranged sequentially adjacent to each other along the side; the status display screen, the toggle switch, the upshift button, the downshift button, the gear indicator lights, the power switch, the power indicator light, and the TYPE-C charging port are all electrically connected to the control circuit.

[0010] A second aspect of the present invention provides a control method for an electronic ND filter based on liquid crystal dimming, applied to the electronic ND filter based on liquid crystal dimming described in the first aspect above, comprising the following steps: Obtain the transmittance setting of the target ND filter; Based on the transmittance-voltage mapping relationship, determine the target driving voltage value that matches the transmittance setting command of the target ND filter; The control circuit generates and outputs an AC square wave drive voltage with the target drive voltage value to the liquid crystal dimming module; The arrangement angle of dye-doped liquid crystal molecules in the first liquid crystal dye layer is changed according to the amplitude of the AC square wave driving voltage.

[0011] Furthermore, the step of determining the target driving voltage value that matches the transmittance level command of the target ND filter includes: establishing a mapping relationship between the transmittance parameter and the voltage amplitude; when the input voltage is zero or lower than the liquid crystal turn-on threshold voltage, the alignment direction of the dye-doped liquid crystal molecules in the first liquid crystal dye layer remains orthogonal to the initial absorption polarization direction of the liquid crystal dimming module, and the liquid crystal dimming module outputs the lowest light transmittance. This method constructs a photosensitive failure protection logic under power failure or low voltage conditions.

[0012] Furthermore, the step of obtaining the transmittance level instruction of the target ND filter includes automatic dimming mode or manual dimming mode: in automatic dimming mode, the ambient light illuminance value is obtained, the obtained ambient light illuminance value is compared with multiple consecutive illuminance threshold intervals, and the matching level corresponding to the illuminance threshold interval is used as the transmittance level instruction of the target ND filter according to the comparison result. In manual dimming mode, an external input gear adjustment signal is received, and the gear corresponding to the gear adjustment signal is used as the target ND filter transmittance gear instruction. In the step of determining the target driving voltage value that matches the target ND filter transmittance gear instruction, a fixed voltage value bound to the transmittance center value of the target ND filter transmittance gear instruction is extracted as the target driving voltage value.

[0013] Furthermore, in the step of generating and outputting an AC square wave drive voltage with the target drive voltage value to the liquid crystal dimming module, the control circuit outputs an AC square wave drive voltage with a frequency between 32Hz and 64Hz and a positive level duration to negative level duration ratio of 1:1 to the liquid crystal dimming module.

[0014] This invention provides an electronic ND filter based on liquid crystal dimming and its control method. It has the following beneficial effects: 1. The liquid crystal dimming module of the present invention sets the initial alignment direction of the dye-doped liquid crystal molecules in the first liquid crystal dye layer to be orthogonal to the initial polarization direction of the polarizing film. This ensures that when the system is powered off or the control voltage is lower than the threshold, the physical light transmission channel of the liquid crystal dimming module is in a state of maximum blocking. In the event that the device is not powered on or the power supply is unexpectedly interrupted, it can automatically output the lowest light transmittance, thereby providing normal physical light protection for the photosensitive element or imaging device located at the back of the filter, and preventing damage to the photosensitive device caused by direct exposure to strong external light.

[0015] 2. In this invention, a phase delay waveplate is sandwiched between the first liquid crystal dye layer and the second liquid crystal dye layer stacked along the light transmission direction. This converts the linearly polarized light emitted from the pre-stage liquid crystal into circularly polarized light. When the circularly polarized light undergoes physical reflection at the interface of the internal substrate and its polarization direction is reversed, it passes through the waveplate in the opposite direction and is converted into reflected linearly polarized light that is perpendicular to the original incident polarization direction. Since the molecular arrangement direction within the second liquid crystal dye layer can directly absorb this intersecting and perpendicular reflected linearly polarized light, this invention directly blocks the reflected light output from the interface between the multilayer glass and the conductive coating by relying on the internal polarization state conversion mechanism, thus eliminating stray reflections in the transmission light path.

[0016] 3. The control circuit of the present invention outputs an AC square wave drive signal to the liquid crystal dimming module through a full-bridge drive architecture, wherein the duration of the positive level and the duration of the negative level are strictly equal. This alternating electric field control method with absolute symmetry of positive and negative half-cycles makes the net component of the DC bias voltage applied to both ends of the liquid crystal conductive coating constant to zero, thereby blocking the condition for irreversible physical polarization of dye-doped liquid crystal molecules under the action of a continuous unidirectional electric field, maintaining the long-term consistency of the liquid crystal molecule alignment angle in response to the drive voltage, and preventing the decay of dimming accuracy. Attached Figure Description

[0017] Figure 1 This is a frontal perspective view of the present invention; Figure 2 This is a three-dimensional structural diagram of the back of the present invention; Figure 3 This is an exploded view of the layer structure of the single-layer liquid crystal dimming module in Embodiment 1 of the present invention; Figure 4 This is an exploded view of the hierarchical structure of the dual-layer anti-reflective liquid crystal dimming module in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the control circuit of the present invention; Figure 6 This is a schematic diagram of the charging circuit of the present invention; Figure 7 This is a schematic diagram of the driving circuit of the present invention; Figure 8 This is a schematic diagram of the display circuit of the present invention; Figure 9 Other circuit diagrams of the present invention are shown below.

[0018] Among them, 100 is the outer casing; 101 is the electronic ND LCD screen; 102 is the status display screen; 103 is the upshift button; 104 is the toggle switch; 105 is the downshift button; 106 is the photosensitive element; 107 is the gear indicator light; 108 is the power switch; 109 is the power indicator light; 110 is the TYPE-C charging port; 200 is the LCD dimming module; 201 is the first outer glass substrate; 202 is the polarizing film; 203 is the first inner glass substrate; 204 is the first ITO conductive coating; 205 is the first guide film; 206 is the first liquid crystal dye layer; 207 is the second guide film; 208 is the second ITO conductive coating; 209 is the second outer glass substrate; 210 is the second liquid crystal dye layer; and 211 is the 1 / 4λ wave plate. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see the appendix Figure 1-4This invention provides an electronic ND filter based on liquid crystal dimming and its control method, comprising: a housing 100; an electronic ND liquid crystal screen 101 disposed in the light-transmitting area of ​​the housing 100, the electronic ND liquid crystal screen 101 including a liquid crystal dimming module 200, the liquid crystal dimming module 200 including at least a first liquid crystal dye layer 206; the first liquid crystal dye layer 206 containing dye-doped liquid crystal; and a control circuit disposed within the housing 100 and electrically connected to the liquid crystal dimming module 200, the control circuit outputting an AC square wave driving voltage to the liquid crystal dimming module 200 for changing the alignment direction of the dye-doped liquid crystal molecules.

[0021] Specifically, the electronic ND LCD screen 101 is fixed to the through-hole structure of the outer shell 100 by a mechanical structure, forming an optical path channel. The control circuit is integrated on a printed circuit board, which is fixed to the non-transparent area inside the outer shell 100. The control circuit is connected to the conductive pins of the LCD dimming module 200 through a flexible printed circuit board. The AC square wave driving voltage output by the control circuit is applied to both ends of the LCD dimming module 200. The dye-doped liquid crystal molecules in the first liquid crystal dye layer 206 are deflected under the action of the electric field. The deflection angle of the liquid crystal molecules changes their absorption cross section for light, thereby adjusting the overall light transmittance of the electronic ND LCD screen 101. The transmittance is divided into 6 consecutive levels, namely ND2, ND4, ND8, ND16, ND32 and ND64. Among them, ND2 has the highest light transmittance and ND64 has the lowest light transmittance.

[0022] The liquid crystal dimming module 200 also includes a polarizing film 202, the initial polarization direction of which is orthogonal to the initial alignment direction of the dye-doped liquid crystal molecules in the first liquid crystal dye layer 206; along the incident light direction, the liquid crystal dimming module 200 sequentially includes a first outer glass substrate 201, a polarizing film 202, a first inner glass substrate 203, a first ITO conductive coating 204, a first guiding film 205, a first liquid crystal dye layer 206, a second guiding film 207, a second ITO conductive coating 208, and a second outer glass substrate 209. A sealant is provided between the edges of the first inner glass substrate 203 and the second outer glass substrate 209, and the first liquid crystal dye layer 206 is sealed between the first inner glass substrate 203 and the second outer glass substrate 209.

[0023] Specifically, ambient natural light enters the liquid crystal dimming module 200 along the incident direction, passes through the first outer glass substrate 201 and then through the polarizing film 202, and is converted into initial linearly polarized light. The first inner glass substrate 203 and the second outer glass substrate 209 provide physical support. The surfaces of the first guide film 205 and the second guide film 207 have directional friction textures, which are used to set the initial alignment direction of the first liquid crystal dye layer 206 in a zero-voltage state. The first ITO conductive coating 204 and the second ITO conductive coating 208 receive the AC square wave driving voltage output by the control circuit and form a driving electric field. The sealant is applied in a closed loop along the edge of the substrate to isolate the internal liquid crystal material from the external environment.

[0024] The liquid crystal dimming module 200 also includes a second liquid crystal dye layer 210 and a 1 / 4λ waveplate 211. The second liquid crystal dye layer 210 contains dye-doped liquid crystal. The first liquid crystal dye layer 206 and the second liquid crystal dye layer 210 are stacked along the light transmission direction, and the 1 / 4λ waveplate 211 is disposed between the first liquid crystal dye layer 206 and the second liquid crystal dye layer 210. The polarization direction of the linearly polarized light emitted through the first liquid crystal dye layer 206 is at an angle of 45 degrees with the optical axis of the 1 / 4λ waveplate 211. The linearly polarized light emitted through the first liquid crystal dye layer 206 is converted into circularly polarized light by the 1 / 4λ waveplate 211. The circularly polarized light is reflected by the interface of the structure containing the second liquid crystal dye layer 210, its polarization state is reversed, and it is converted into linearly polarized light again by the 1 / 4λ waveplate 211. The polarization direction of the linearly polarized light after the second conversion is perpendicular to the polarization direction of the linearly polarized light emitted through the first liquid crystal dye layer 206. The linearly polarized light after the second conversion is absorbed by the dye-doped liquid crystal in the second liquid crystal dye layer 210.

[0025] Specifically, the light passing through the first liquid crystal dye layer 206 is linearly polarized light with a specific polarization direction. This linearly polarized light enters the 1 / 4λ waveplate 211. Since the incident polarization direction makes an angle of 45 degrees with the optical axis, the output light is converted into circularly polarized light. When this circularly polarized light undergoes physical reflection at the subsequent ITO conductive layer interface or glass interface, its rotation direction is reversed. The reversed reflected circularly polarized light travels in the opposite direction and passes through the 1 / 4λ waveplate 211 again, transforming into a second linearly polarized light that intersects the polarization direction of the initial incident linearly polarized light at a 90-degree angle. The arrangement direction of the molecules in the second liquid crystal dye layer 210 remains parallel to the polarization direction of the second linearly polarized light, thereby absorbing the second linearly polarized light generated by the reflection and eliminating the reflected light from the internal interface.

[0026] The control circuit includes a microcontroller and a 4MOS transistor full-bridge drive circuit electrically connected to the microcontroller. The microcontroller converts the DC power supply into an AC square wave drive voltage with a frequency between 32Hz and 64Hz and a positive-to-negative level time ratio of 1:1 through the 4MOS transistor full-bridge drive circuit, and outputs the AC square wave drive voltage to the liquid crystal dimming module 200.

[0027] Specifically, the control circuit also includes a power supply module, which is powered by a lithium battery with a rated voltage of 4.7V. The microcontroller outputs a PWM control signal to the gate of the 4MOS full-bridge drive circuit. The 4MOS full-bridge drive circuit inverts and converts the 4.7V DC voltage to generate an AC square wave drive voltage. The voltage adjustment range of this AC square wave drive voltage is set to 1.5V to 10V, and the frequency is limited to 32Hz to 64Hz to avoid visible flickering. The ratio of the positive level maintenance time to the negative level maintenance time is strictly controlled to 1:1, so that the DC bias component at both ends of the liquid crystal dimming module 200 is zero, preventing the liquid crystal molecules from polarizing.

[0028] A photosensitive element 106 is provided on the side of the housing 100 facing the external light incident end; the photosensitive element 106 is electrically connected to the control circuit, and the photosensitive element 106 collects ambient light illuminance data and transmits it to the control circuit; the control circuit adjusts the amplitude of the AC square wave drive voltage output to the liquid crystal dimming module 200 according to the ambient light illuminance data.

[0029] Specifically, the photosensitive element 106 is a photosensitive sensor. The photosensitive element 106 collects the analog illuminance signal of the current external environment and converts it into digital ambient illuminance data through an internal analog-to-digital converter. The microcontroller receives the ambient illuminance data. When the ambient illuminance data increases, the microcontroller increases the amplitude of the AC square wave drive voltage output to the liquid crystal dimming module 200, so that the setting changes to a higher ND value to reduce the transmittance.

[0030] The housing 100 has a front and a side; a status display screen 102 is provided on the front; The side panel features a toggle switch 104, an upshift button 103, and a downshift button 105, with the upshift button 103 and downshift button 105 located on either side of the toggle switch 104. Multiple gear indicator lights 107 are also located on the side, arranged along the contour edge of the side panel. A power switch 108, a power indicator light 109, and a Type-C charging port 110 are also located on the side, arranged sequentially adjacent to each other. The status display screen 102, toggle switch 104, upshift button 103, downshift button 105, gear indicator lights 107, power switch 108, power indicator light 109, and Type-C charging port 110 are all electrically connected to the control circuit.

[0031] Specifically, the printed circuit board has reserved soldering positions for two sets of display components: a status display screen 102 and multiple gear indicator lights 107. The microcontroller contains an execution program compatible with both display modes. When the status display screen 102 is physically assembled, the liquid crystal display program is executed; when the gear indicator lights 107 are physically assembled, the indicator light display program is executed. There are six gear indicator lights 107, corresponding to the six gears from ND2 to ND64. The content output area of ​​the status display screen 102 includes: ND gear value, light brightness value, battery power icon, and Bluetooth connection status icon. The power switch 108 shares the system power switch and mode switching functions. The microcontroller's timing logic is as follows: When the system is powered off, it receives a signal that the power button 108 has been pressed for 3 seconds, and the system powers on; when the system is powered on, it receives a signal that the power button 108 has been pressed for 3 seconds, and the system powers off; when the system is powered on, it receives a short press signal from the power button 108, and the system switches between normal mode and automatic dimming mode; when the system is powered off, the microcontroller disables the short press signal from the power button 108, and the power indicator 109 is a red-green dual-color LED. The microcontroller's control logic is: when the TYPE-C charging port 110 is not connected and the system is powered off... When the power indicator light 109 is off, the green LED is constantly lit when the system is powered on and the battery voltage is higher than the threshold. When the battery voltage is lower than the threshold, the red LED is constantly lit. When charging via the TYPE-C charging port 110, the red LED flashes. After charging is complete, the green LED flashes. The filter system is also equipped with an independent external remote control. The external remote control has a built-in Bluetooth module, a remote control LCD screen, and four physical buttons. The four physical buttons are the mode switch button, the remote control up button, the remote control down button, and the remote control power button. The content displayed on the remote control LCD screen is synchronized with the content displayed on the status display screen 102.

[0032] This invention also provides a control method for an electronic ND filter based on liquid crystal dimming, comprising the following steps: Obtain the transmittance setting of the target ND filter; Based on the transmittance-voltage mapping relationship, determine the target driving voltage value that matches the transmittance setting command of the target ND filter; The control circuit generates and outputs an AC square wave drive voltage with a target drive voltage value to the liquid crystal dimming module 200. The arrangement angle of dye-doped liquid crystal molecules in the first liquid crystal dye layer 206 is changed according to the amplitude of the AC square wave driving voltage.

[0033] Specifically, a lookup table containing transmittance-voltage mapping relationships is written into the microcontroller's internal memory. The microcontroller obtains the current target ND filter transmittance setting instruction, retrieves the corresponding target drive voltage value from the lookup table, and the output range of the target drive voltage value is limited to between 1.5V and 10V. The microcontroller adjusts the duty cycle parameter of the PWM control signal to control the 4MOS transistor full-bridge drive circuit to output an AC square wave drive voltage of corresponding amplitude.

[0034] The step of determining the target driving voltage value that matches the transmittance level command of the target ND filter includes: establishing a mapping relationship between the transmittance parameter and the voltage amplitude; when the input voltage is zero or the input voltage is lower than the liquid crystal turn-on threshold voltage, the arrangement direction of the dye-doped liquid crystal molecules in the first liquid crystal dye layer 206 is orthogonal to the initial absorption polarization direction of the liquid crystal dimming module 200, and the liquid crystal dimming module 200 outputs the lowest light transmittance.

[0035] Specifically, the microcontroller defines the voltage range of 0 to 1.5V as the output range corresponding to the ND64 level. When the system is powered off and the power supply is disconnected, so that the voltage input to the LCD dimming module 200 is 0V, the transmittance of the LCD dimming module 200 is at the physical limit of the ND64 level, that is, the LCD screen is in the darkest state. When the voltage output reaches the maximum value of 10V, the transmittance of the LCD dimming module 200 is at the ND2 level, that is, the LCD screen is in the brightest state.

[0036] The steps for obtaining the transmittance level command of the target ND filter include automatic dimming mode or manual dimming mode: In automatic dimming mode, the ambient light illuminance value is acquired, and the acquired ambient light illuminance value is compared with multiple consecutive illuminance threshold intervals. Based on the comparison results, the matching level corresponding to the illuminance threshold interval is taken as the transmittance level command of the target ND filter; In manual dimming mode, an externally input level adjustment signal is received, and the level corresponding to the level adjustment signal is taken as the transmittance level command of the target ND filter. In the step of determining the target driving voltage value that matches the transmittance level command of the target ND filter, a fixed voltage value bound to the transmittance center value of the transmittance level command of the target ND filter is extracted as the target driving voltage value.

[0037] Specifically, the manual dimming mode is the system-defined normal mode. In this mode, the microcontroller receives the switching signal from the up-shift button 103 or the down-shift button 105, or the mechanical encoding signal from the toggle switch 104. The operation logic is as follows: rotating the toggle switch 104 upwards outputs an up-shift signal, and rotating it downwards outputs a down-shift signal. The shifting between ND2 and ND64 forms a closed loop. After obtaining the shift adjustment signal, the microcontroller outputs a single fixed voltage value corresponding to the center value of that shift. In the automatic dimming mode, the microcontroller obtains the ambient light illuminance value output by the photosensitive element 106 in real time. When the ambient light illuminance value rises above the upper limit of the current threshold range, the microcontroller updates the target ND filter transmittance shift command to a larger ND shift, such as from ND8 to ND16. When the ambient light illuminance value falls below the lower limit of the current threshold range, the microcontroller updates the target ND filter transmittance shift command to a smaller ND shift.

[0038] In the step of generating and outputting an AC square wave drive voltage with a target drive voltage value to the liquid crystal dimming module 200, the control circuit outputs an AC square wave drive voltage with a frequency between 32Hz and 64Hz and a positive level duration to negative level duration ratio of 1:1 to the liquid crystal dimming module 200.

[0039] Specifically, the timer inside the microcontroller calculates the cycle length based on the set frequency parameters of 32Hz to 64Hz, and uses the half-cycle length as the timer toggling threshold. At the end of each half-cycle, the conduction direction of the 4MOS transistor full-bridge drive circuit is toggled, so that the positive level cycle and the negative level cycle length are absolutely equal, and a square wave signal with a 1:1 duty cycle is output to the LCD dimming module 200.

[0040] Examples 1-4: Example 1: Electronic ND Filter Based on Single-Layer Liquid Crystal and Polarizing Film This embodiment discloses the hardware composition and physical connection relationship of an electronic ND filter based on a single-layer liquid crystal matching polarizing film structure.

[0041] The electronic ND filter includes a housing 100, an electronic ND LCD screen 101, and a control circuit. The electronic ND LCD screen 101 is fixed in a through-hole in the middle of the housing 100, forming a path for natural light to pass through. The control circuit is located on a printed circuit board inside the housing 100.

[0042] Along the direction of incident light, the physical layers inside the electronic ND liquid crystal screen 101 are as follows: a first outer glass substrate 201, a polarizing film 202, a first inner glass substrate 203, a first ITO conductive coating 204, a first guiding film 205, a first liquid crystal dye layer 206, a second guiding film 207, a second ITO conductive coating 208, and a second outer glass substrate 209. The first liquid crystal dye layer 206 is sealed by a sealant applied in a closed loop around the edges of the first inner glass substrate 203 and the second outer glass substrate 209.

[0043] The first liquid crystal dye layer 206 is filled with dye-doped liquid crystal material. The first guiding film 205 and the second guiding film 207 are textured to constrain the initial alignment direction of the dye-doped liquid crystal molecules. The transmission polarization direction of the polarizing film 202 is orthogonal to the initial alignment direction of the dye-doped liquid crystal molecules at a 90-degree angle. When the input voltage between the first ITO conductive coating 204 and the second ITO conductive coating 208 is zero or lower than the liquid crystal on-threshold, the dye-doped liquid crystal molecules maintain their orthogonal alignment, and the electronic ND liquid crystal screen 101 outputs the lowest light transmittance, corresponding to the ND64 level.

[0044] The control circuit's printed circuit board integrates a microcontroller and a 4-MOSFET full-bridge drive circuit. The system uses a 4.7V lithium battery for DC power. The microcontroller outputs a pulse-width modulation signal to control the 4-MOSFET full-bridge drive circuit, inverting the DC power into an AC square wave drive voltage, which is output to the first ITO conductive coating 204 and the second ITO conductive coating 208. The parameters of this AC square wave drive voltage are limited as follows: the frequency is set in the range of 32Hz to 64Hz, the ratio of the positive level maintenance time to the negative level maintenance time is constant at 1:1, and the voltage amplitude adjustment range is set from 1.5V to 10V. The 0 to 1.5V range corresponds to the ND64 level, and 10V corresponds to the ND2 level, which has the highest transmittance.

[0045] The front of the housing 100 features a status display screen 102, employing an LCD device to simultaneously display the current ND level, ambient light level, battery level, and Bluetooth connection status. A toggle switch 104 is located on the side of the housing 100, with an up-shift button 103 and a down-shift button 105 positioned on the top and bottom edges of the toggle switch 104, respectively. Along the lower edge of the side are a power switch 108, a red / green dual-color power indicator light 109, and a Type-C charging port 110. All of these physical interaction devices are electrically connected to the input / output pins of the microcontroller.

[0046] Example 2: Anti-reflective electronic ND filter based on dual-layer liquid crystal and 1 / 4λ wave plate This embodiment discloses an electronic ND filter that employs a double-layer liquid crystal stacked structure to eliminate reflections at internal interfaces. This structure primarily addresses the optical reflection problem caused by the interface of multilayer glass or ITO substrates.

[0047] The difference between this embodiment and Embodiment 1 lies in the optical layer structure and hardware display method of the electronic ND liquid crystal screen 101. Along the light transmission direction, the electronic ND liquid crystal screen 101 of this embodiment sequentially includes: a first substrate group, a first ITO conductive coating 204, a first guide film 205, a first liquid crystal dye layer 206, a second guide film 207, a second ITO conductive coating 208, an intermediate glass substrate, a 1 / 4λ waveplate 211, an intermediate glass substrate, a third ITO conductive coating, a third guide film, a second liquid crystal dye layer 210, a fourth guide film, a fourth ITO conductive coating, and a second substrate group. The first liquid crystal dye layer 206 and the second liquid crystal dye layer 210 are superimposed along the optical path, and the 1 / 4λ waveplate 211 is sandwiched between the two liquid crystal layers.

[0048] The physical process for eliminating internally reflected light is as follows: When ambient natural light penetrates the first liquid crystal dye layer 206, the emitted light is transformed into linearly polarized light with a single polarization direction.

[0049] The linearly polarized light is incident on a 1 / 4λ waveplate 211, and the angle between its polarization direction and the optical axis of the 1 / 4λ waveplate 211 is mechanically set to 45 degrees. Through the phase delay effect of the birefringent crystal, the two orthogonal components of the linearly polarized light produce a phase difference of π / 2, and the outgoing light is transformed into circularly polarized light.

[0050] When the circularly polarized light is physically reflected at the interface of the next stage, its polarization direction is reversed.

[0051] The inverted reflected circularly polarized light travels in the opposite direction and passes through the 1 / 4λ waveplate 211 again, transforming into second linearly polarized light. At this point, the polarization direction of the second linearly polarized light is 90 degrees orthogonal to the polarization direction of the original linearly polarized light emitted after penetrating the first liquid crystal dye layer 206.

[0052] The arrangement direction of the dye-doped liquid crystal molecules in the second liquid crystal dye layer 210 is parallel to the polarization direction of the second linearly polarized light, thereby absorbing the second linearly polarized light generated by the reflection and blocking the reflected light from passing through to the outside.

[0053] In the hardware display section, this embodiment does not use a status display screen 102. Instead, under the control of a compatible program of the microcontroller, six independent gear indicator lights 107 are set in the array positions reserved on the side of the housing 100. These six gear indicator lights 107 are LEDs and are connected to the control circuit respectively to indicate the ND2, ND4, ND8, ND16, ND32 and ND64 gears by their illumination status.

[0054] Example 3: Control method for electronic ND filters This embodiment discloses a control flow executed by a microcontroller, applicable to the hardware structure described in Embodiment 1 or Embodiment 2. The control method includes the following sequential steps: The microcontroller detects the voltage level of the power switch 108. In the off state, when the microcontroller receives a trigger signal lasting 3 seconds or longer, it connects the main power supply to the system; in the on state, when the microcontroller receives a trigger signal lasting 3 seconds or longer, it disconnects the main power supply to the system. The microcontroller outputs status signals to the power indicator 109: when the system is powered on and the battery voltage is higher than a preset threshold, it outputs a solid green light; when the battery voltage is lower than the preset threshold, it outputs a solid red light; when it detects that the TYPE-C charging port 110 is connected to an external power source, it outputs a flashing red light; when the internal charging circuit determines that the battery is fully charged, it outputs a flashing green light.

[0055] The microcontroller detects the short press signal of the power switch 108 to switch the dimming mode.

[0056] In manual dimming mode: The microcontroller reads the mechanical rotation encoding signal from the toggle switch 104, or the closed signals from the up / down buttons 103 and 105. Each time a valid up / down signal is received, the microcontroller cycles through the six ND2, ND4, ND8, ND16, ND32, and ND64 levels, generating a target ND filter transmittance level command. In automatic dimming mode: The microcontroller reads the ambient light illuminance analog signal collected by the photosensitive element 106 through an external hardware interface, converting it into a digital illuminance value via an analog-to-digital converter. The microcontroller compares the current digital illuminance value with a preset continuous illuminance threshold range in its memory. When the illuminance is ≥30000 lux, the matching instruction is ND64 level; When 13000 lux ≤ illuminance < 22000 lux, the matching instruction is ND32. When 8000 lux ≤ illuminance < 12000 lux, the matching instruction is ND16 level; When 4000 lux ≤ illuminance < 6000 lux, the matching command is ND8. When 1500 lux ≤ illuminance < 2500 lux, the matching instruction is ND4 level; When the illuminance is ≤1000 lux, the matching command is the preset low-level value. The microcontroller will update the matched level to the target ND filter transmittance level command after comparison and confirmation.

[0057] To prevent the liquid crystal molecules in the liquid crystal dimming module 200 from polarization failure due to prolonged unidirectional bias electric field, the microcontroller uses one of the following two control methods to generate and output a symmetrical AC square wave with positive and negative half-cycles: The first drive control method involves DC voltage regulation combined with constant-width commutation control. The microcontroller calls its internally stored transmittance voltage mapping table to extract the target DC voltage amplitude corresponding to the current target ND filter transmittance setting. The extractable range is limited to 1.5V to 10V. The microcontroller outputs an adjustment signal to the control terminal of the boost chip, controlling the boost chip to output a DC supply voltage equal to the target DC voltage amplitude, which is then connected to the power input terminal of the 4MOS transistor full-bridge drive circuit. Simultaneously, the microcontroller outputs a commutation control sequence to the control terminal of the 4MOS transistor full-bridge drive circuit, with a frequency constant between 32Hz and 64Hz and a positive and negative pulse width duty cycle constant at 50%. The 4MOS transistor full-bridge drive circuit reverses the polarity of the input DC supply voltage, outputting an AC square wave with a constant positive-to-negative level maintenance time ratio of 1:1 and a voltage amplitude equal to the target DC voltage amplitude.

[0058] The second drive control method involves using a constant-voltage DC power supply combined with symmetrical chopper pulse width modulation (PWM) to control the boost chip to output a fixed-amplitude DC power supply voltage, which is then connected to the power input of the 4-MOSFET full-bridge drive circuit. The microcontroller queries its internally stored transmittance duty cycle mapping relationship to obtain the target PWM duty cycle parameter that matches the current target ND filter transmittance setting. Within a low-frequency alternating cycle of 32Hz to 64Hz, the microcontroller controls the 4-MOSFET full-bridge drive circuit to perform forward chopping conduction according to the target PWM duty cycle parameter in the first half of the cycle, and reverse chopping conduction according to the same high-frequency duty cycle parameter in the second half of the cycle. The full-bridge drive circuit converts the fixed DC power supply voltage into an AC square wave whose effective voltage varies with the target PWM duty cycle parameter. During this process, the microcontroller maintains a constant ratio of 1:1 between the cumulative conduction time of the forward chopping and the cumulative conduction time of the reverse chopping.

[0059] The AC square waves generated by the above two methods are applied to both ends of the liquid crystal dimming module 200, driving the liquid crystal molecules in the first liquid crystal dye layer 206 or the second liquid crystal dye layer 210 to generate a fixed deflection angle corresponding to the target command, thereby executing the set light transmittance.

[0060] Example 4: Hardware Circuit System of Electronic ND Filter This embodiment discloses the physical structure and electrical connection relationships of internal components on a printed circuit board used in electronic ND filters. Based on circuit function, the circuit system specifically includes a control circuit, a charging circuit, a driving circuit, a display circuit, and other peripheral circuits.

[0061] See attached document Figure 5The core physical entity of the control circuit is the microcontroller (U1). The microcontroller (U1) uses an MCU chip with built-in Bluetooth functionality or a regular MCU chip combined with a separate Bluetooth module. The microcontroller (U1) is externally connected to a crystal oscillator circuit and an antenna circuit. The crystal oscillator circuit includes a crystal oscillator (Y2) and matching capacitors (C7, C8). The two ends of the crystal oscillator (Y2) are electrically connected to the oscillator input pin (BT_OSCI) and the oscillator output pin (BT_OSCO) of the microcontroller (U1), respectively. The antenna circuit includes an impedance matching network composed of inductors (L1, L2) and capacitor (C23). One end of this network is connected to the RF pin (BT_RF) of the microcontroller (U1), and the other end is connected to the physical antenna (ANT1).

[0062] See attached document Figure 6 The charging circuit includes a charging management IC (IC4), a boost converter (U3), and a voltage regulator (U4). The power input (VCC) of the charging management IC (IC4) receives a 5V DC power supply, and its battery connection (BAT) is connected to the positive terminal of the lithium battery. The charging status pin (CHRG) and standby status pin (STDBY) of the charging management IC (IC4) are connected to the cathodes of the first LED (D1) and the second LED (D2), respectively, to indicate the power supply status. The inputs (IN) of the boost converter (U3) and the voltage regulator (U4) are electrically connected to the positive terminal (VBAT) of the lithium battery. The output (OUT) of the boost converter (U3) outputs an adjustable DC supply voltage (VR) to the drive circuit. The output (OUT) of the voltage regulator (U4) outputs a constant 3.3V DC supply voltage, electrically connected to the microcontroller (U1) and other peripheral nodes requiring 3.3V power.

[0063] See attached document Figure 7The driving circuit comprises a full-bridge driving circuit consisting of four MOSFETs (Q1, Q2, Q3, and Q4). The input terminals of the first MOSFET (Q1) and the third MOSFET (Q3) are connected in parallel and electrically connected to the DC power supply voltage (VR) node output by the boost converter chip (U3). The ground terminals of the second MOSFET (Q2) and the fourth MOSFET (Q4) are connected in parallel and electrically connected to the system common ground (GND). The series common node between the first MOSFET (Q1) and the second MOSFET (Q2) forms the first output terminal of the full-bridge driving circuit, and the series common node between the third MOSFET (Q3) and the fourth MOSFET (Q4) forms the second output terminal of the full-bridge driving circuit. The first and second output terminals are connected together to the output interface (P3) for driving the electronic ND LCD screen. The gates of the four MOSFETs are respectively connected to network nodes (NetLabel1, NetLabel2, NetLabel3, and NetLabel4), and are electrically connected to the corresponding control pins of the microcontroller (U1) through the network nodes. The control signal converts the DC voltage into an AC square wave drive level through the full-bridge drive circuit.

[0064] See attached document Figure 8 The display circuit includes an LCD screen display circuit and an LED indicator display circuit, with pre-reserved mounting positions for both components on the printed circuit board. The LCD screen display circuit includes an LCD screen interface, with multiple pins (including LCD_COM and LCD_SEG series pins) electrically connected to the corresponding LCD driver pins of the microcontroller (U1). The LED indicator display circuit includes an array of multiple light-emitting diodes (D3, D4, D5, D6, D7, D8). The anode of each light-emitting diode is connected in series with current-limiting resistors (R113 to R118), and then electrically connected to the corresponding control pin of the microcontroller (U1) through a network node.

[0065] See attached document Figure 9 Other circuitry includes a charging interface, a power switch, and a button detection network. The charging interface uses a Type-C charging port (JP1), with its power pin outputting a DC 5V voltage to the input of the charging management IC (IC4). One end of the power switch (S1) is connected to an external signal (P-POWER), and the other end is grounded. The button detection network consists of a resistor divider topology composed of resistors (R100, R110) and multiple physical buttons. The output signal (AD_KEY) of the divider node is electrically connected to the analog-to-digital converter pin of the microcontroller (U1). The microcontroller (U1) determines the closed state of different buttons by detecting the analog voltage value of this pin. The system also includes connection nodes (P4, P5) for connecting external toggle switch signals or Hall effect sensor signals.

[0066] Working principle: The system is powered by a rated 4.7V DC power supply. The microcontroller in the control circuit enters the working state after detecting the low-level signal that the switch 108 is continuously triggered. When the system is not powered on or the input voltage is zero, the dye-doped liquid crystal molecules in the first liquid crystal dye layer 206 are physically constrained by the first guide film 205 and the second guide film 207. Their initial alignment direction is orthogonal to the initial transmission polarization direction of the front polarizing film 202, so that the liquid crystal dimming module 200 blocks most of the light and outputs the lowest light transmittance ND64 level, which constitutes the photosensitive failure protection mechanism in the power-off state.

[0067] During operation, the microcontroller obtains the target ND filter transmittance level instruction according to the set logic path: if in automatic dimming mode, the photosensitive element 106 collects ambient light illuminance data in real time and transmits it to the control circuit. The microcontroller compares the ambient light illuminance data with the preset continuous illuminance threshold range and extracts the level that matches the threshold range as the target ND filter transmittance level instruction; if in manual dimming mode, the microcontroller analyzes the mechanical rotation signal of the toggle switch 104 or the pulse signal of the up-gear button 103 and the down-gear button 105, switches between the 6 consecutive levels from ND2 to ND64 and generates the target ND filter transmittance level instruction.

[0068] After receiving the instruction, the microcontroller queries the internally stored transmittance voltage mapping relationship and extracts a fixed target driving voltage value bound to the center value of the transmittance of the current instruction. This voltage value extraction range is limited to 1.5V to 10V. Subsequently, the microcontroller inverts the DC power supply through a 4-MOS transistor full-bridge driving circuit inside the control circuit to generate an AC square wave driving voltage with a fixed frequency between 32Hz and 64Hz and a positive level duration to negative level duration ratio of 1:1. This AC square wave driving voltage is applied across the first ITO conductive coating 204 and the second ITO conductive coating 208 to form an alternating electric field, changing the arrangement angle of the dye-doped liquid crystal molecules in the first liquid crystal dye layer 206. By adjusting the absorption cross-section of the molecules to light, the transmittance of the electronic ND liquid crystal screen 101 is quantitatively adjusted.

[0069] During light transmission, to eliminate reflected light generated at the internal structural interface, the linearly polarized light emitted through the first liquid crystal dye layer 206 is incident on the 1 / 4λ waveplate 211 with its polarization direction at a 45-degree angle to the optical axis. After phase delay, it is converted into circularly polarized light. When this circularly polarized light undergoes physical reflection at the interface of the structure containing the second liquid crystal dye layer 210, its polarization state is reversed. The reversed circularly polarized light passes through the 1 / 4λ waveplate 211 again and is converted into linearly polarized light with a polarization direction perpendicular to the original linearly polarized light emitted through the first liquid crystal dye layer 206. Since the polarization direction of this re-transformed linearly polarized light is absorbed by the dye-doped liquid crystal in the second liquid crystal dye layer 210, the reflected light output from the internal interface is blocked. At the same time, the microcontroller converts the currently executed ND gear and environmental parameters into electrical signals and outputs them to the status display screen 102 on the front of the housing 100, or to the gear indicator light 107 and power indicator light 109 on the side of the housing 100, thus completing the physical display of the system operating parameters.

Claims

1. An electronic ND filter based on liquid crystal dimming, characterized in that, include: Outer shell (100); An electronic ND liquid crystal display (101) is disposed in the light-transmitting area of ​​the housing (100). The electronic ND liquid crystal display (101) includes a liquid crystal dimming module (200), and the liquid crystal dimming module (200) includes at least a first liquid crystal dye layer (206). The first liquid crystal dye layer (206) contains dye-doped liquid crystal; A control circuit is disposed inside the housing (100) and electrically connected to the liquid crystal dimming module (200). The control circuit outputs an AC square wave driving voltage to the liquid crystal dimming module (200) to change the arrangement direction of the dye-doped liquid crystal molecules.

2. The electronic ND filter based on liquid crystal dimming according to claim 1, characterized in that, The liquid crystal dimming module (200) also includes a polarizing film (202), the initial polarization direction of which is orthogonal to the initial alignment direction of the dye-doped liquid crystal molecules in the first liquid crystal dye layer (206). Along the incident light direction, the liquid crystal dimming module (200) sequentially includes a first outer glass substrate (201), the polarizing film (202), a first inner glass substrate (203), a first ITO conductive coating (204), a first guide film (205), a first liquid crystal dye layer (206), a second guide film (207), a second ITO conductive coating (208), and a second outer glass substrate (209). A sealant is provided between the edges of the first inner glass substrate (203) and the second outer glass substrate (209), and the first liquid crystal dye layer (206) is sealed between the first inner glass substrate (203) and the second outer glass substrate (209).

3. The electronic ND filter based on liquid crystal dimming according to claim 1, characterized in that, The liquid crystal dimming module (200) further includes a second liquid crystal dye layer (210) and a 1 / 4λ wave plate (211), wherein the second liquid crystal dye layer (210) contains dye-doped liquid crystal; The first liquid crystal dye layer (206) and the second liquid crystal dye layer (210) are stacked along the light transmission direction, and the 1 / 4λ wave plate (211) is disposed between the first liquid crystal dye layer (206) and the second liquid crystal dye layer (210); The polarization direction of the linearly polarized light emitted through the first liquid crystal dye layer (206) is 45 degrees with the optical axis of the 1 / 4λ waveplate (211); Linearly polarized light penetrating the first liquid crystal dye layer (206) is converted into circularly polarized light by the 1 / 4λ waveplate (211). The circularly polarized light is reflected by the interface of the structure where the second liquid crystal dye layer (210) is located, its polarization state is reversed, and it is converted into linearly polarized light again by the 1 / 4λ waveplate (211). The polarization direction of the linearly polarized light after the second conversion is perpendicular to the polarization direction of the linearly polarized light emitted from the first liquid crystal dye layer (206). The linearly polarized light after the second conversion is absorbed by the dye-doped liquid crystal in the second liquid crystal dye layer (210).

4. The electronic ND filter based on liquid crystal dimming according to claim 1, characterized in that, The control circuit includes a microcontroller and a 4MOS transistor full-bridge drive circuit electrically connected to the microcontroller; The microcontroller converts the DC power supply into an AC square wave driving voltage with a frequency between 32Hz and 64Hz and a positive-to-negative level time ratio of 1:1 through the 4MOS full-bridge driving circuit, and outputs the AC square wave driving voltage to the liquid crystal dimming module (200).

5. The electronic ND filter based on liquid crystal dimming according to claim 1, characterized in that, A photosensitive element (106) is provided on the side of the outer casing (100) facing the external light incident end. The photosensitive element (106) is electrically connected to the control circuit, and the photosensitive element (106) collects ambient light illuminance data and transmits it to the control circuit; The control circuit adjusts the amplitude of the AC square wave drive voltage output to the liquid crystal dimming module (200) according to the ambient light illuminance data.

6. The electronic ND filter based on liquid crystal dimming according to claim 1, characterized in that, The outer casing (100) has a front and sides; The front is provided with a status display screen (102); The side is provided with a toggle switch (104), an upshift button (103), and a downshift button (105), with the upshift button (103) and the downshift button (105) located on both sides of the toggle switch (104); The side is also provided with a plurality of gear indicator lights (107), which are arranged along the contour edge of the side. The side is also provided with a power switch (108), a power indicator light (109) and a TYPE-C charging port (110), which are arranged adjacent to each other along the side. The status display screen (102), the gear selector switch (104), the upshift button (103), the downshift button (105), the gear indicator light (107), the power switch (108), the power indicator light (109), and the TYPE-C charging port (110) are all electrically connected to the control circuit.

7. A control method for an electronic ND filter based on liquid crystal dimming, applied to an electronic ND filter based on liquid crystal dimming as described in any one of claims 1-6, characterized in that, Includes the following steps: Obtain the transmittance setting of the target ND filter; Based on the transmittance-voltage mapping relationship, determine the target driving voltage value that matches the transmittance setting command of the target ND filter; The control circuit generates and outputs an AC square wave drive voltage with the target drive voltage value to the liquid crystal dimming module (200); The arrangement angle of dye-doped liquid crystal molecules in the first liquid crystal dye layer (206) is changed according to the amplitude of the AC square wave driving voltage.

8. The control method for an electronic ND filter based on liquid crystal dimming according to claim 7, characterized in that, The step of determining the target drive voltage value that matches the transmittance setting command of the target ND filter includes: Establish a mapping relationship between transmittance parameters and voltage amplitude; When the input voltage is zero or lower than the liquid crystal turn-on threshold voltage, the arrangement direction of the dye-doped liquid crystal molecules in the first liquid crystal dye layer (206) is orthogonal to the initial absorption polarization direction of the liquid crystal dimming module (200), and the liquid crystal dimming module (200) outputs the lowest light transmittance.

9. The control method for an electronic ND filter based on liquid crystal dimming according to claim 7, characterized in that, The steps to obtain the transmittance setting of the target ND filter include automatic dimming mode or manual dimming mode: In automatic dimming mode, the ambient light illuminance value is acquired, and the acquired ambient light illuminance value is compared with multiple consecutive illuminance threshold intervals. Based on the comparison results, the matching level of the corresponding illuminance threshold interval is used as the transmission level instruction of the target ND filter. In manual dimming mode, an external input gear adjustment signal is received, and the gear corresponding to the gear adjustment signal is used as the target ND filter transmittance gear instruction. In the step of determining the target driving voltage value that matches the target ND filter transmittance gear instruction, a fixed voltage value bound to the transmittance center value of the target ND filter transmittance gear instruction is extracted as the target driving voltage value.

10. The control method for an electronic ND filter based on liquid crystal dimming according to claim 7, characterized in that, In the step of generating and outputting an AC square wave drive voltage with the target drive voltage value to the liquid crystal dimming module (200), the control circuit outputs an AC square wave drive voltage with a frequency between 32Hz and 64Hz and a positive level duration to negative level duration ratio of 1:1 to the liquid crystal dimming module (200).

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