Projector focusing method based on linear Hall effect measurement

Abstract

The present invention provides a projector focusing method based on linear Hall distance measurement, comprising the following steps: step 1, installing a linear Hall at the fixed end of the projector lens and installing a permanent magnet at the movable end of the projector lens; step 2, connecting the linear Hall to the motor control system signal; step 3, during the projector focusing process, when the permanent magnet approaches or moves away from the linear Hall, the voltage output of the linear Hall produces a linear voltage change as the distance changes; step 4, establishing an algorithm model, using the linear voltage change of the linear Hall within the magnetic field range to convert it into the distance between the current Hall element and the permanent magnet, that is, the specific position of the lens in the entire machine stroke. The present invention completes the focal length adjustment of the projector by combining the linear Hall and the permanent magnet, which is lower in cost than traditional switches and optocoupler limiters. The lateral movement distance is detected by the linear Hall output analog quantity, which is consistent with the lateral extension and contraction direction of the projection lens, and more realistic feedback of motion data.

Description

Technical Field

[0001] The invention relates to a focusing method, in particular to a projector focusing method based on linear Hall distance measurement, and belongs to the technical field of projector focusing. Background Art

[0002] A projector is a commonly used multimedia presentation device whose primary function is to project images or videos onto a screen or wall for the audience to see clearly. Widely used in education, business, entertainment, and other fields, projectors facilitate presentations, teaching, and conferences. Focusing is a crucial step in projector use. Its primary function is to adjust the focal length of the projector lens to maximize the projected image's clarity, making it sharper and more layered, thereby enhancing the viewing experience. By adjusting the focal length, the projected image can be made more consistent with the audience's visual habits, reducing visual fatigue and improving the viewing experience. Different projection distances and projection surface sizes require different focal length settings, and focusing allows the projector to adapt to different projection environments.

[0003] Currently, limit detection is required in projection lens motor control to provide signal indications when the lens reaches one end and the other end. It is generally designed with 1-2 switches and optocouplers.

[0004] For example, the prior art CN206348581U discloses an automatic focusing projector, which includes an optical machine, a telescopic lens and an automatic focusing structure. The telescopic lens includes a lever, and the automatic focusing structure includes a motor, a focusing ring and a bracket. The photoelectric sensor switch can only provide a digital output of on or off, resulting in the main control receiving a signal only when the last lens arrives. This misses the intermediate amount of movement, and the main control can only try to extend and retract multiple times to locate the position of the current lens in the entire stroke. For this reason, a projector focusing method based on linear Hall distance measurement is proposed. Summary of the Invention

[0005] In view of this, the present invention provides a projector focusing method based on linear Hall distance measurement to solve or alleviate one of the technical problems existing in the prior art. Under the premise of controlling costs, the digital quantity of position detection is converted into analog quantity, adding a judgment dimension to the main control lens motion control, improving the efficiency and experience of automatic focusing of projection, and at least providing a beneficial option.

[0006] The technical solution of the embodiment of the present invention is implemented as follows: A projector focusing method based on linear Hall distance measurement includes the following steps:

[0007] Step 1: Install a linear Hall at the fixed end of the projector lens and a permanent magnet at the movable end of the projector lens. The permanent magnet moves as the lens advances or contracts.

[0008] Step 2: Connect the linear Hall sensor to the motor control system signal, and the linear Hall sensor sends the signal to the motor control system;

[0009] Step 3: During the projector focusing process, when the permanent magnet approaches or moves away from the linear Hall element, the voltage output of the linear Hall element changes linearly with the distance. When the permanent magnet approaches the linear Hall element, the magnetic field strength B increases, causing the output level V to increase; when the permanent magnet moves away, the magnetic field strength B decreases, causing the output level V to decrease.

[0010] Step 4: Build an algorithm model, using the linear change of the voltage of the linear Hall element within the magnetic field range to convert it into the distance between the current Hall element and the permanent magnet, that is, the specific position of the lens in the entire travel range;

[0011] Step 5: Calibrate and confirm the ADC values ​​a and b of the permanent magnet at the closest and farthest points during the lens focusing process, record the parameters, and compare the voltage ADC values ​​collected during actual operation with the a and b values ​​during calibration to ensure that the lens is within the range between the closest and farthest points;

[0012] Step 6: The motor control system determines whether the lens should move forward or backward based on the current position and the system blur level captured by the camera.

[0013] Further preferably, in step 1, the linear Hall and the permanent magnet are arranged horizontally along the axis of the projector lens.

[0014] Further preferably: in step 2, the linear Hall sensor is used to output an analog signal, ie, a continuous voltage signal.

[0015] Further preferably, in step three, the output level of the linear Hall element is linearly related to the strength of the external magnetic field within a certain range, and the linearity will trigger a stroke according to the strength of the magnetic field, and the stroke is the linear magnetic field range.

[0016] Further preferably: in step 4, the algorithm model is based on the lens imaging formula and the linear relationship between the Hall element voltage and the object distance.

[0017] Further preferably: in step 4, according to the lens imaging formula:

[0018] 1 / u+1 / v=1 / f

[0019] Where u is the object distance, v is the image distance, and f is the focal length. After changing the formula, we can get:

[0020] u=fv / (v−f)

[0021] According to the linear relationship between object distance and Hall element voltage:

[0022] u=k1×V adc +k2

[0023] Where V adc is the Hall element voltage, combined with the lens imaging formula, we can get:

[0024] k1×V adc +k2=fv / (v−f)

[0025] After sorting out, we can know:

[0026] V adc =(fv-k2v+k2f) / (k1(v−f))).

[0027] Further preferably, in the projector scenario, the difference between the image distance v and the focal length f is smaller than the image distance v itself, that is, V−f≈V. The formula can be rearranged to obtain:

[0028] V adc =(fv-k2v+k2f) / (k1v)

[0029] V adc =(f-k2) / k1+(k2f) / (k1v)

[0030] From this we can get:

[0031] V adc =K1 / v+K2

[0032] According to the formula, the Hall element voltage V adc It is inversely proportional to the image distance v.

[0033] Further preferably: the Hall element voltage V adc Actual measurements are performed on the image distance v to obtain multiple sets of corresponding values, and the least squares method is used to solve K1 and K2.

[0034] Further preferred: when solving K1 and K2, the function is recorded as:

[0035] V adc = K1×(1 / v) + K2

[0036] Consider 1 / v as the independent variable, V adc With as the dependent variable, linear regression is used to solve K1 and K2.

[0037] Further preferably, in step six, the image at the current position is compared with the image at the previous position, and according to the change in clarity, the motor control system determines whether the next step is to continue moving forward or backward.

[0038] The embodiment of the present invention adopts the above technical solution, which has the following advantages:

[0039] 1. The present invention uses a linear Hall sensor and a permanent magnet to adjust the focus of the projector, which is lower in cost than traditional switches and optical coupler limiters.

[0040] Second, the present invention can increase process quantity for the motor control system, making the control system more accurate and direct.

[0041] 3. The present invention detects the lateral movement distance through the linear Hall output analog quantity, which is consistent with the lateral extension and contraction direction of the projection lens, and provides more realistic feedback of motion data.

[0042] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 is a flow chart of the present invention;

[0045] Figure 2 This is a linear relationship diagram between the output voltage and magnetic induction intensity of the present invention;

[0046] Figure 3 This is a structural diagram of a projector lens according to the present invention;

[0047] Figure 4 This is a system structure diagram of the present invention.

[0048] Reference numerals: 1, projection lens; 2, permanent magnet; 3, linear Hall sensor; 4, farthest end of the lens; 6, nearest end of the lens. DETAILED DESCRIPTION

[0049] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0050] It should be clear that the following embodiments of the present disclosure are described through specific concrete examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other in the absence of conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0051] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this disclosure, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0052] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present disclosure. The illustrations only show components related to the present disclosure and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0053] Additionally, in the following description, specific details are provided to provide a thorough understanding of the examples. However, one skilled in the art will appreciate that the aspects described can be practiced without these specific details.

[0054] Example 1

[0055] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a projector focusing method based on linear Hall distance measurement, comprising the following steps:

[0056] Step 1: Install a linear Hall at the fixed end of the projector lens and a permanent magnet at the movable end of the projector lens. The linear Hall and the permanent magnet are arranged horizontally along the axis of the projector lens. The permanent magnet moves with the extension or contraction of the lens.

[0057] Step 2: Connect the linear Hall sensor to the motor control system signal. The linear Hall sensor is used to output an analog signal, that is, a continuous voltage signal. The linear Hall sensor sends the signal to the motor control system. The camera also sends the signal to the motor control system. The motor control system sends the control signal to the motor to control the movement of the lens.

[0058] Step 3: During the projector focusing process, when the permanent magnet approaches or moves away from the linear Hall element, the output level of the linear Hall element is linearly related to the strength of the external magnetic field within a certain range, such as Figure 2 As shown in the figure, when the permanent magnet approaches the linear Hall element, the magnetic field strength B increases, causing the output level V to increase; when the permanent magnet moves away, the magnetic field strength B decreases, causing the output level V to decrease. The linearity will trigger the stroke according to the strength of the magnetic field. This stroke is the linear magnetic field range.

[0059] Step 4: Establish an algorithm model. Use the linear change of the voltage of the linear Hall element within the magnetic field range to convert it into the distance between the current Hall element and the permanent magnet, that is, the specific position of the lens in the entire travel range. The algorithm model is based on the lens imaging formula and the linear relationship between the Hall element voltage and the object distance. According to the lens imaging formula:

[0060] 1 / u+1 / v=1 / f

[0061] Where u is the object distance, v is the image distance, and f is the focal length. After changing the formula, we can get:

[0062] u=fv / (v−f)

[0063] According to the linear relationship between object distance and Hall element voltage:

[0064] u=k1×V adc +k2

[0065] Where V adc is the Hall element voltage, combined with the lens imaging formula, we can get:

[0066] k1×V adc +k2=fv / (v−f)

[0067] After sorting out, we can know:

[0068] V adc =(fv-k2v+k2f) / (k1(v−f)))

[0069] In the projector scenario, the difference between the image distance v and the focal length f is small relative to the image distance v itself, that is, V−f≈V. Rearranging the formula yields:

[0070] V adc =(fv-k2v+k2f) / (k1v)

[0071] V adc =(f-k2) / k1+(k2f) / (k1v)

[0072] From this we can get:

[0073] V adc =K1 / v+K2

[0074] According to the formula, the Hall element voltage V adc It is inversely proportional to the image distance v.

[0075] The voltage V of the Hall element adc The image distance v is measured to obtain multiple sets of corresponding values, and the least squares method is used to solve K1 and K2. When solving K1 and K2, the equations are written as:

[0076] V adc = K1×(1 / v) + K2

[0077] Consider 1 / v as the independent variable, V adc With as the dependent variable, linear regression is used to solve K1 and K2.

[0078] Step 5: Calibrate and confirm the ADC values ​​a and b of the permanent magnet at the closest and farthest points during lens focusing. Record the parameters and compare the voltage ADC values ​​collected during actual operation with the a and b values ​​during calibration to ensure that the lens is adjusted within the range between the closest and farthest points.

[0079] Step 6: The motor control system compares the image at the current position with the image at the previous position based on the current position and the blur level of the image captured by the camera. Based on the change in clarity, the motor control system determines whether to continue forward or backward in the next step.

[0080] Example 2

[0081] like Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a projector focusing method based on linear Hall distance measurement, comprising the following steps:

[0082] Step 1. Install a linear Hall sensor at the fixed end of the projector lens and a permanent magnet at the movable end of the projector lens. The linear Hall sensor and the permanent magnet are horizontally arranged along the axis of the projector lens. The linear Hall sensor is installed at the fixed end of the projector lens to ensure that it can stably detect the magnetic field changes of the permanent magnet during the movement of the lens. The permanent magnet is installed at the movable end of the projector lens, and its magnetic pole direction should be aligned with the sensitive axis direction of the linear Hall sensor to achieve maximum magnetic field change detection. The linear Hall sensor and the permanent magnet should be horizontally arranged along the axis of the projector lens to ensure that the relative position change between the two can accurately reflect the displacement of the lens when the lens moves.

[0083] Step 2: Connect the linear Hall sensor to the motor control system signal. The linear Hall sensor is used to output an analog signal, that is, a continuous voltage signal. When connecting, use an appropriate cable or connecting wire to connect the output signal line of the linear Hall sensor to the analog signal input interface of the motor control system;

[0084] Step 3. During the projector focusing process, when the permanent magnet approaches or moves away from the linear Hall, the output level of the linear Hall element is linearly related to the external magnetic field strength within a certain range. The linearity will trigger the stroke according to the strength of the magnetic field. This stroke is the linear magnetic field range. When the permanent magnet approaches the linear Hall element, the magnetic field strength B increases, causing the output level V to increase; when the permanent magnet moves away, the magnetic field strength B decreases, causing the output level V to decrease. This change process is the stroke, which represents the magnetic field strength range that the linear Hall element can respond to, that is, the linear magnetic field range.

[0085] Step 4: Establish an algorithm model. Use the linear change of the voltage of the linear Hall element within the magnetic field range to convert it into the distance between the current Hall element and the permanent magnet, that is, the specific position of the lens in the entire travel range. The algorithm model is based on the lens imaging formula and the linear relationship between the Hall element voltage and the object distance. According to the lens imaging formula:

[0086] 1 / u+1 / v=1 / f

[0087] Where u is the object distance, v is the image distance, and f is the focal length. After changing the formula, we can get:

[0088] u=fv / (v−f)

[0089] According to the linear relationship between object distance and Hall element voltage:

[0090] u=k1×V adc +k2

[0091] Where V adc is the Hall element voltage, combined with the lens imaging formula, we can get:

[0092] k1×V adc+k2=fv / (v−f)

[0093] After sorting out, we can know:

[0094] V adc =(fv-k2v+k2f) / (k1(v−f)))

[0095] In the projector scenario, the difference between the image distance v and the focal length f is small relative to the image distance v itself, that is, V−f≈V. Rearranging the formula yields:

[0096] V adc =(fv-k2v+k2f) / (k1v)

[0097] V adc =(f-k2) / k1+(k2f) / (k1v)

[0098] From this we can get:

[0099] V adc =K1 / v+K2

[0100] According to the formula, the Hall element voltage V adc It is inversely proportional to the image distance v.

[0101] The voltage V of the Hall element adc The image distance v is measured to obtain multiple sets of corresponding values, and the least squares method is used to solve K1 and K2. When solving K1 and K2, the equations are written as:

[0102] V adc = K1×(1 / v) + K2

[0103] Consider 1 / v as the independent variable, V adc With as the dependent variable, linear regression is used to solve K1 and K2.

[0104] The following is a simple C++ program example (for reference only) that uses the least squares method to solve K1 and K2:

[0105] / / Assume there are 10 sets of measurement data

[0106] double Vadc

[10] = { / * the value of Vadc* / };

[0107] double v

[10] = { / * value of v* / };

[0108] void calculate_coefficients(double *K1, double *K2) {

[0109] double sum_inv_v = 0.0;

[0110] double sum_Vadc = 0.0;

[0111] double sum_inv_v_times_Vadc = 0.0;

[0112] double sum_inv_v_sq = 0.0;

[0113] / / Calculate the necessary sums

[0114] for (int i = 0; i < n; i++) {

[0115] double inv_v = 1.0 / v[i];

[0116] sum_inv_v += inv_v;

[0117] sum_Vadc += Vadc[i];

[0118] sum_inv_v_times_Vadc += inv_v * Vadc[i];

[0119] sum_inv_v_sq += inv_v * inv_v;

[0120] }<()

[0121] double denominator = n * sum_inv_v_sq - sum_inv_v * sum_inv_v;

[0122] *K1 = (n * sum_inv_v_times_Vadc - sum_inv_v * sum_Vadc) / denominator;

[0123] *K2 = (sum_inv_v_sq * sum_Vadc - sum_inv_v * sum_inv_v_times_Vadc) / denominator;

[0124] }

[0125] / / Calculate the function of the image distance v

[0126] double calculate_image_distance(double voltage) {

[0127] return K1 / (voltage – K2);

[0128] }

[0129] / / Function to calculate voltage V

[0130] double calculate_ voltage (double image_distance) {

[0131] return K1 / image_distance + K2;

[0132] }

[0133] Through the above procedure, K1 and K2 can be solved;

[0134] Step 5. Calibrate and confirm the ADC values ​​a and b of the nearest and farthest points of the permanent magnet during lens focusing, record the parameters, and compare the voltage ADC values ​​collected during actual operation with a and b during calibration to ensure that the lens is focused within the range between the nearest and farthest points. During the nearest point calibration, move the permanent magnet to the nearest point of lens focusing, read the voltage ADC value output by the linear Hall element at this position through the circuit, and record it as a. During the farthest point calibration, move the permanent magnet to the farthest point of lens focusing, and read the voltage ADC value output by the linear Hall element at this position through the circuit again, and record it as b. Record the two ADC values ​​of a and b collected. Next, as calibration parameters, these parameters will be used for comparison and judgment in the subsequent lens focusing process. During the actual operation of the projector, the voltage ADC value output by the linear Hall element is read in real time through the circuit, and the real-time collected ADC value is compared with a and b during calibration. According to the comparison result of the real-time ADC value with a and b, the current position of the permanent magnet (i.e., the lens) is judged. If the real-time ADC value is between a and b, it means that the lens is within the range between the nearest point and the farthest point, and the focusing operation can continue. If the real-time ADC value is less than a or greater than b, it means that the lens has reached the limit position of focusing, and the focusing operation should be stopped or reversed.

[0135] Step 6. The motor control system compares the image at the current position with the image at the previous position based on the current position and the degree of blur of the image captured by the camera. Based on the change in clarity, the motor control system determines whether to continue forward or backward. If the clarity improves (i.e., the image becomes clearer), it is determined that the current direction is correct and should continue forward. If the clarity decreases (i.e., the image becomes blurrier), it is determined that the current direction is wrong and should retreat to the previous position or make fine adjustments. Based on the judgment result, the motor control system sends instructions to the motor driver to control the motor to move forward, backward or stop. The above steps are repeated to form a closed-loop control system to continuously adjust the motor position until the optimal image clarity position is found.

[0136] Example 3

[0137] like Figure 3 As shown, an embodiment of the present invention provides a projector lens structure, including a projection lens 1, a permanent magnet 2 and a linear Hall sensor 3, wherein the projection lens 1 includes a movable end and a fixed end, and the movable end of the projection lens 1 moves within a length range between the farthest end 4 and the closest end 6 of the lens. The permanent magnet 2 and the linear Hall sensor 3 are respectively mounted on the movable end and the fixed end of the projection lens 1, and the permanent magnet 2 and the linear Hall sensor 3 are on the same horizontal plane as the central axis of the lens. At the same time, the permanent magnet 2 and the linear Hall sensor 3 are arranged along the direction of the central axis of the lens. At this time, the current distance from the permanent magnet to the Hall can be calculated by the linear change of the voltage of the linear Hall sensor 3 within the magnetic field range.

[0138] Example 4

[0139] like Figure 4 As described above, an embodiment of the present invention provides a projector focusing system, which includes a motor control system, a camera, a motor, a Hall sensor and a permanent magnet. The camera, the Hall sensor and the motor control system are signal-connected. The linear Hall sends a signal to the motor control system. The camera also sends an image signal to the motor control system. The motor is electrically connected to the motor control system. The motor control system sends a control signal to the motor to control the movement of the lens and complete the focusing process.

[0140] The following are schematic diagrams of the voltage reading circuit, motor driving circuit and camera driving circuit of the present invention, which are all prior arts. As long as those skilled in the art can search for them, the present invention will not elaborate on them.

[0141] The present invention achieves focus adjustment of the projector by cooperating with a linear Hall and a permanent magnet, and has lower cost than traditional switches and optical coupler limiters.

[0142] The present invention can increase process quantity for the motor control system and make the control system more accurate and direct.

[0143] The present invention detects the distance of lateral movement through a linear Hall output analog quantity, which is consistent with the lateral extension and contraction direction of the projection lens, and provides more realistic feedback of motion data.

[0144] The basic principles of the present disclosure have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this disclosure are merely illustrative and not restrictive, and should not be construed as necessarily possessed by each embodiment of the present disclosure. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, rather than as limitations. These details do not limit the present disclosure to necessarily being implemented using these specific details.

[0145] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.

[0146] In the present disclosure, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. The block diagrams of the devices, devices, equipment, and systems involved in the present disclosure are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "including," "comprising," "having," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0147] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various modifications and substitutions within the technical scope disclosed in the present invention, and such modifications and substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A projector focusing method based on linear Hall distance measurement, characterized in that: The following steps are involved: Step 1: Install a linear Hall sensor at the fixed end of the projector lens and a permanent magnet at the movable end of the projector lens. Step 2: Connect the linear Hall sensor to the motor control system signal; Step 3: During the projector focusing process, when the permanent magnet approaches or moves away from the linear Hall sensor, the voltage output of the linear Hall sensor changes linearly with the distance. Step 4: Establish an algorithm model. Use the linear change of the voltage of the linear Hall element within the magnetic field range to convert it into the distance between the current Hall element and the permanent magnet, that is, the specific position of the lens in the entire travel range. According to the lens imaging formula: 1 / u+1 / v=1 / f; Where u is the object distance, v is the image distance, and f is the focal length. After changing the formula, we can get: u=fv / (vf); According to the linear relationship between object distance and Hall element voltage: u=k1×V adc +k2; Where V adc is the Hall element voltage, combined with the lens imaging formula, we can get: k1×V adc +k2=fv / (v-f); After sorting out, we can know: V adc =(fv-k2v+k2f) / (k1(vf)))); In the projector scenario, the difference between the image distance v and the focal length f is small relative to the image distance v. The formula can be rearranged to obtain: V adc =(fv-k2v+k2f) / (k1v); V adc =(f-k2) / k1+(k2f) / (k1v); From this we can get: In adc =K1 / v+K2; According to the formula, the Hall element voltage V adc It is inversely proportional to the image distance v; the voltage V adc Actual measurements are performed on the image distance v to obtain multiple sets of corresponding values, and the least squares method is used to solve K1 and K2; Step 5: Calibrate and confirm the ADC values ​​a and b of the permanent magnet at the closest and farthest points during lens focusing. Record the parameters and compare the voltage ADC values ​​collected during actual operation with the a and b values ​​during calibration. Focus the lens within the range between the closest and farthest points. Step 6: The motor control system determines whether the lens should move forward or backward based on the current position and the blur level of the image captured by the camera.

2. The projector focusing method based on linear Hall distance measurement according to claim 1, characterized in that: In step 1, the linear Hall and the permanent magnet are horizontally arranged along the axis of the projector lens.

3. The projector focusing method based on linear Hall distance measurement according to claim 1, characterized in that: In step 2, the linear Hall sensor is used to output an analog signal, ie, a continuous voltage signal.

4. The projector focusing method based on linear Hall distance measurement according to claim 1, characterized in that: In step three, the linear Hall output level is linearly related to the strength of the external magnetic field, and the linearity will trigger a stroke according to the strength of the magnetic field, and the stroke is the linear magnetic field range.

5. The projector focusing method based on linear Hall distance measurement according to claim 1, characterized in that: In step 4, the algorithm model is based on the lens imaging formula and the linear relationship between the Hall element voltage and the object distance.

6. The projector focusing method based on linear Hall distance measurement according to claim 1, characterized in that: When solving for K1 and K2, write the equation as: V adc = K1×(1 / v) + K2; Consider 1 / v as the independent variable, V adc As the dependent variable, linear regression is used to solve K1 and K2 to obtain the algorithm model.

7. The projector focusing method based on linear Hall distance measurement according to claim 1, characterized in that: In step six, the image at the current position is compared with the image at the previous position, and based on the change in clarity, the motor control system determines whether the next step is forward or backward.

Images