Focusing mechanism, projection equipment and control method thereof

Abstract

The invention discloses a focusing mechanism, projection equipment and a control method thereof, and relates to the technical field of projection. Wherein the focusing mechanism comprises a focusing ring, a motor and a potentiometer; the focusing ring is used for being in transmission connection with the lens assembly. The focusing ring rotates to drive the lens assembly to move in the axial direction of the focusing ring. The motor is in drive connection with the focusing ring and used for driving the focusing ring to rotate; the potentiometer is in driving connection with the motor and is used for positioning the rotation position of the focusing ring. According to the technical scheme, the focusing duration of the projection equipment can be shortened, and the focusing efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of projection technology, and in particular to a focusing mechanism, a projection device and a control method thereof. Background Art

[0002] With the development of projection technology, projection equipment is becoming more and more popular, especially small and portable projection equipment. Portable and small projection equipment is often used in different occasions, so the distance between the projection equipment and the projection screen will often change. In order to meet this change, the lens of the projection equipment needs to be focused so that the projection image is clear at different distances.

[0003] The projection equipment in the related art adopts a manual focusing method for focusing, which has the problems of long focusing time and low focusing efficiency. Summary of the invention

[0004] The main purpose of the present invention is to provide a focusing mechanism, which aims to shorten the focusing time of a projection device and improve the focusing efficiency.

[0005] To achieve the above object, the focusing mechanism proposed in the present invention comprises:

[0006] A focus ring, used for transmission connection with the lens assembly, wherein the rotation of the focus ring can drive the lens assembly to move along the axial direction of the focus ring;

[0007] a motor, drivingly connected to the focus ring to drive the focus ring to rotate; and

[0008] A potentiometer is driven and connected to the motor to locate the rotation position of the focus ring.

[0009] In one embodiment of the present application, the motor has an output shaft, the output shaft is provided with a first gear, the outer periphery of the focus ring is provided with a second gear, and the second gear is meshed and connected with the first gear;

[0010] The potentiometer has a transmission shaft, and the transmission shaft is drivingly connected to the output shaft.

[0011] In one embodiment of the present application, an assembly hole is provided at the end of the transmission shaft, the output shaft is inserted into the assembly hole, and the central axis of the output shaft is colinear with the central axis of the transmission shaft.

[0012] In one embodiment of the present application, the assembly hole is a special-shaped hole; the shaft end of the output shaft is a special-shaped shaft, and the outer circumferential shape of the shaft end of the output shaft is matched with the hole circumferential shape of the assembly hole.

[0013] In one embodiment of the present application, the potentiometer includes a fixed resistor and a moving contact that can move along the fixed resistor, and the transmission shaft is connected to the moving contact to drive the moving contact to move along the fixed resistor to change the output voltage of the potentiometer;

[0014] The output shaft can drive the transmission shaft to rotate, so that the output voltage of the potentiometer is adjusted to a target output voltage.

[0015] In one embodiment of the present application, the potentiometer has an a pin and a c pin respectively connected to both ends of the fixed resistor, the c pin is grounded, and the a pin is connected to a preset reference voltage; the voltage at the moving contact is the output voltage of the potentiometer.

[0016] In an embodiment of the present application, at least one spiral guide groove is provided on the focus ring for slidingly cooperating with a guide rod on the lens assembly.

[0017] To achieve the above object, the present application also provides a projection device, including a control module, a lens assembly and the above focusing mechanism;

[0018] The lens assembly is transmission-mounted on the focus ring;

[0019] The motor and the potentiometer are both electrically connected to the control module.

[0020] In an embodiment of the present application, the projection device further includes a distance sensor electrically connected to the control module, and the distance sensor is used to detect the distance between the lens assembly and the projection screen.

[0021] To achieve the above object, the present application also provides a control method based on the above projection device, the method comprising:

[0022] determining a target position of the lens assembly;

[0023] determining a target output voltage of the potentiometer according to a target position of the lens assembly;

[0024] Obtaining the current output voltage of the potentiometer;

[0025] Determining the operation data of the motor according to the difference between the target output voltage and the current output voltage;

[0026] According to the operation data, the motor is controlled to drive the focus ring to rotate so that the lens assembly moves to a target position.

[0027] In an embodiment of the present application, the step of determining the target position of the lens assembly includes:

[0028] The distance between the lens assembly and the projection screen is acquired, and the target position of the lens assembly is determined according to the distance.

[0029] In an embodiment of the present application, there is a preset linear correspondence between the position of the lens assembly and the output voltage of the potentiometer.

[0030] In the focusing mechanism of the technical solution of the present invention, the focusing ring is used for transmission connection with the lens assembly, and the lens assembly can be driven to move along the axial direction of the focusing ring by rotating the focusing ring driven by the motor. By connecting the potentiometer to the motor drive, the motor can simultaneously drive the focusing ring and the potentiometer to rotate, so that the resistance of the potentiometer changes in geometric proportion to the rotation angle of the focusing ring, so that the rotation position of the focusing ring can be positioned by the output voltage of the potentiometer, and then the position of the lens assembly can be positioned. Therefore, the motor can directly drive the lens assembly to move from the current position to the target position according to the output voltage of the potentiometer to realize the focusing function without returning to the starting point for adjustment, thereby shortening the focusing time and improving the focusing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0032] Figure 1 It is a structural schematic diagram of an embodiment of a focusing mechanism of the present invention;

[0033] Figure 2 It is a schematic diagram of the exploded structure of an embodiment of the focusing mechanism of the present invention;

[0034] Figure 3 Another perspective structural schematic diagram of the focusing mechanism embodiment of the present invention;

[0035] Figure 4 It is a schematic diagram of the resistance principle of the potentiometer in the present invention;

[0036] Figure 5 for Figure 4 Schematic diagram of voltage principle corresponding to the embodiment;

[0037] Figure 6 The figure is a flow chart of an embodiment of a method for controlling a projection device according to the present invention.

[0038] Description of Figure Numbers:

[0039]

[0040]

[0041] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0044] At the same time, the meaning of "and / or" or "and / or" appearing in the full text includes three options. Taking "A and / or B" as an example, it includes option A, or option B, or a option in which both A and B are satisfied.

[0045] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0046] With the development of projection technology, projection equipment is becoming more and more popular, especially small and portable projection equipment. Portable and small projection equipment is often used in different occasions, so the distance between the projection equipment and the projection screen will often change. In order to meet this change, the lens of the projection equipment needs to be focused so that the projection image is clear at different distances.

[0047] The projection equipment in the related art uses manual focusing to focus, which has the problem of long focusing time and low focusing efficiency. Some projection equipment using automatic focusing uses optical coupling to control the motor operation. This solution requires high assembly precision of the optical coupling and lens assembly, and each time the focus is adjusted, it needs to return to the starting point and continue to adjust, resulting in long focusing time and low focusing efficiency.

[0048] Based on this, the present invention proposes a focusing mechanism, which is applied to a projection device, and is intended to achieve focusing of a lens assembly by driving a potentiometer 300 with a motor 200, and utilizing the corresponding relationship between the output voltage of the potentiometer 300 and the rotation angle of the motor 200. Each time the focus is adjusted, there is no need to return to the starting point, which shortens the focusing time and improves the focusing efficiency. The structure of the focusing mechanism is described below by way of an embodiment.

[0049] like Figures 1 to 5 As shown, the focus mechanism includes a focus ring 100 , a motor 200 and a potentiometer 300 .

[0050] The focus ring 100 is used for transmission connection with the lens assembly. The rotation of the focus ring 100 can drive the lens assembly to move along the axial direction of the focus ring 100; the motor 200 is driven and connected to the focus ring 100 to drive the focus ring 100 to rotate; the potentiometer 300 is driven and connected to the motor 200 to locate the rotation position of the focus ring 100.

[0051] It can be understood that the focus ring 100 is a cylindrical structure, and the lens assembly can be installed on the inside or outside of the focus ring 100. The lens assembly is connected to the focus ring 100 in a transmission manner, so that the rotational movement of the focus ring 100 can be converted into the axial movement of the lens assembly. Optionally, the lens assembly and the focus ring 100 can adopt a matching structure of a spiral groove and a guide rod, for example, a spiral groove can be set on the focus ring 100, and a guide rod can be set on the lens assembly; or a guide rod can be set on the focus ring 100, and a spiral groove can be set on the lens assembly. The specific transmission structure of the lens assembly and the focus ring 100 is not limited here. The focus ring 100 is connected to the motor 200 in a driving manner. When focusing is required, the motor 200 can drive the focus ring 100 to rotate, driving the lens assembly to move along the axial direction of the focus ring 100.

[0052] In this embodiment, the potentiometer 300 is connected to the motor 200 so that the motor 200 can simultaneously drive the focus ring 100 and the potentiometer 300 to rotate, so that the resistance of the potentiometer 300 changes in geometric proportion to the rotation angle of the focus ring 100, that is, the output voltage of the potentiometer 300 corresponds to the position of the lens assembly, so that the position of the lens assembly can be determined by the output voltage of the potentiometer 300, and then, the lens assembly can be driven to move to the target position (the target position can be understood as the optimal clarity position of the projected image) according to the output voltage of the potentiometer 300.

[0053] Specifically, when focusing is required, the target position of the lens assembly can be calculated based on the distance between the lens assembly and the projection screen, and the target output voltage of the potentiometer 300 corresponding to the target position can be obtained; then, based on the difference between the current output voltage of the potentiometer 300 and the target output voltage, the target direction and amount of movement of the motor 200 can be obtained, and then the motor 200 drives the potentiometer 300 and the focus ring 100 to move until the output voltage of the potentiometer 300 is the target output voltage, and the lens assembly also moves to the target position. In this way, the focusing function is realized.

[0054] It can be understood that the position of the lens assembly of the present embodiment corresponds to the output voltage of the potentiometer 300. Therefore, regardless of whether the current position of the lens assembly is the starting point or not, the target direction and amount of movement of the motor 200 can be obtained by the difference between the current output voltage of the potentiometer 300 and the target output voltage. The lens assembly can be directly driven from the current position to the target position without returning to the starting point for adjustment, thereby shortening the focusing time and improving the focusing efficiency.

[0055] The corresponding relationship between the output voltage of the potentiometer 300 of this embodiment and the position of the lens assembly is described below.

[0056] like Figure 4 The potentiometer 300 has a fixed resistor ac and a contact b that can move on the fixed resistor ac. The motor 200 is connected to the contact b. When the motor 200 rotates, it can drive the contact b to move between the fixed resistors ac, so that the resistance between ab and bc changes linearly.

[0057] like Figure 5For example, the potentiometer 300 pin a is connected to a stable reference voltage Vref, and the c pin is connected to the GND with a voltage of 0. At this time, the voltage Vout at point b is Vout = Vref * Rbc / Rac, where Rab is the resistance between ab and Rac is the resistance between ac. That is, the output voltage Vout of the potentiometer 300 changes with the movement of point b, and the change in the output voltage Vout of the potentiometer 300 is linearly related to the change in the position of the lens assembly.

[0058] In actual application, if the voltage corresponding to one extreme position L1 of the lens assembly (for example, the innermost / outermost position) is Vout1, and the voltage corresponding to the other extreme position L2 (for example, the outermost / innermost position) is Vout2, then: L2-L1=k*(Vout2-Vout1), where k is the proportional coefficient between the movement of the lens assembly and the change in the output voltage, which can be obtained by calibration of the extreme positions.

[0059] Then, for any position Lx of the lens assembly, the potentiometer 300 will have an output voltage Voutx in the relationship: Lx-L1=k*(Voutx-Vout1).

[0060] It can be seen from this that the target output voltage of the potentiometer 300 can be determined by the target position of the lens assembly, so that the moving contact b of the potentiometer 300 only needs to be driven by the motor 200 to move to the position corresponding to the target output voltage, and the focusing ring 100 can be synchronously driven to rotate so that the lens assembly moves to the target position, thereby realizing the focusing action of the lens assembly.

[0061] It should be noted that the potentiometer 300 of the present embodiment is directly connected to the motor 200, and the motor 200 is connected to the focus ring 100. Therefore, when the output shaft 210 of the motor 200 rotates, the focus ring 100 and the potentiometer 300 are synchronously driven to rotate. Compared with the method in which the potentiometer 300 is not connected to the motor 200 in the related art, the present embodiment can further improve the focusing accuracy and greatly improve the focusing success rate.

[0062] In summary, in the focusing mechanism of the technical solution of the present invention, the focus ring 100 is used for transmission connection with the lens assembly, and the focus ring 100 is driven to rotate by the motor 200 to drive the lens assembly to move along the axial direction of the focus ring 100. By driving the potentiometer 300 to the motor 200, the motor 200 can simultaneously drive the focus ring 100 and the potentiometer 300 to rotate, so that the resistance of the potentiometer 300 and the rotation angle of the focus ring 100 change in geometric proportion, so that the rotation position of the focus ring 100 can be positioned by the output voltage of the potentiometer 300, and then the position of the lens assembly can be positioned. Therefore, the motor 200 can directly drive the lens assembly to move from the current position to the target position according to the output voltage of the potentiometer 300, and realize the focusing function without returning to the starting point for adjustment, thereby shortening the focusing time and improving the focusing efficiency.

[0063] In one embodiment of the present application, Figure 2 and Figure 3 The motor 200 has an output shaft 210, the output shaft 210 is provided with a first gear 211, the outer periphery of the focus ring 100 is provided with a second gear 110, and the second gear 110 is meshed and connected with the first gear 211; the potentiometer 300 has a transmission shaft 310, and the transmission shaft 310 is drivingly connected with the output shaft 210 to determine the rotation angle of the output shaft 210.

[0064] This embodiment illustrates the connection structure of the motor 200, the focus ring 100 and the potentiometer 300. The output shaft 210 of the motor 200 is connected to the focus ring 100 and the transmission shaft 310 of the potentiometer 300 at the same time, so that when the output shaft 210 of the motor 200 rotates, it can simultaneously drive the focus ring 100 and the transmission shaft 310 of the potentiometer 300 to rotate. Then, the rotation direction and rotation angle of the output shaft 210 of the motor 200 are consistent with the rotation direction and angle of the transmission shaft 310 of the potentiometer 300, that is, the output shaft 210 of the motor 200 directly drives the movement of the contact b without transmitting power through an intermediate transmission mechanism, further improving the adjustment accuracy.

[0065] In addition, the drive mode in which the output shaft 210 and the focus ring 100 are meshed through the first gear 211 and the second gear 110 reduces energy loss and improves overall transmission efficiency, so that the motor 200 can output a greater torque under the same input power, thereby improving the movement speed and responsiveness of the focus ring 100. Optionally, the first gear 211 is a gear ring structure surrounding the outer periphery of the output shaft 210; the second gear 110 can be a gear ring structure surrounding the outer periphery of the focus ring 100 or can be an arc-shaped rack structure along the circumference of the focus ring 100, etc.

[0066] In actual application, the transmission shaft 310 of the potentiometer 300 is connected to the moving contact b, and when the transmission shaft 310 rotates, it can drive the moving contact b to move along the fixed resistor ac to change the output voltage Vout of the potentiometer 300. It can be understood that, taking the example of the a pin of the fixed resistor being grounded and the c pin being connected to the preset reference voltage, the voltage at the moving contact b is the output voltage of the potentiometer 300. When focusing is required, the output shaft 210 of the motor 200 drives the transmission shaft 310 to rotate to change the position of the moving contact b until the moving contact b moves to a position where the target voltage can be output, so that the lens assembly is simultaneously driven to the target position by the motor 200 to complete the focusing action.

[0067] Furthermore, if Figure 2 and Figure 3 An assembly hole 311 is provided at the end of the transmission shaft 310 , and the output shaft 210 is inserted into the assembly hole 311 . The central axis of the output shaft 210 is collinear with the central axis of the transmission shaft 310 .

[0068] The transmission connection between the transmission shaft 310 and the output shaft 210 is realized by the shaft hole matching mode of the output shaft 210 and the assembly hole 311, thereby simplifying the connection structure. In addition, by aligning the central axis of the output shaft 210 with the central axis of the transmission shaft 310, the rotation of the transmission shaft 310 and the output shaft 210 is synchronized, thereby improving the transmission efficiency, making the corresponding relationship between the output voltage of the potentiometer 300 and the position of the lens assembly more matched, and improving the focusing accuracy.

[0069] Optionally, the assembly hole 311 is a special-shaped hole; the shaft end of the output shaft 210 is a special-shaped shaft, and the outer peripheral shape of the shaft end of the output shaft 210 is adapted to the hole peripheral shape of the assembly hole 311. Such a setting can prevent the transmission shaft 310 and the output shaft 210 from slipping, so as to ensure better transmission efficiency.

[0070] In one embodiment of the present application, Figures 1 to 3 , at least one spiral guide groove 101 is provided on the focus ring 100 for slidingly cooperating with the guide rod on the lens assembly. Such a design can simplify the structure of the lens assembly and improve production efficiency. The number of the guide grooves 101 can be determined according to actual conditions, for example, it can be 1, 2, 3 or more. In this embodiment, considering the movement reliability, two guide grooves 101 are provided on the focus ring 100, and the two guide grooves 101 are respectively arranged on the radially opposite sides of the focus ring 100. Correspondingly, guide rods cooperating with the guide grooves 101 can be respectively provided on both sides of the lens assembly, so that the limiting effect on the opposite sides of the lens assembly is balanced, so that it is more stable during movement.

[0071] The present invention also provides a projection device, which includes a control module, a lens assembly and a focusing mechanism. The specific structure of the focusing mechanism refers to the above embodiment. Since the present projection device adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here. Among them, the lens assembly is driven and installed on the focusing ring 100; the motor 200 and the potentiometer 300 are both electrically connected to the control module.

[0072] Furthermore, the projection device further comprises a distance sensor electrically connected to the control module, and the distance sensor is used to detect the distance between the lens assembly and the projection screen. Optionally, the distance sensor can be an ultrasonic sensor, an infrared sensor or other types of distance detection devices.

[0073] When focusing is required, the distance sensor detects the distance between the lens assembly and the projection screen, and the control module calculates the target position of the lens assembly based on the distance, and then determines the target output voltage of the potentiometer 300 based on the target position; then the current output voltage of the potentiometer 300 is compared with the target output voltage to obtain a difference, and then the rotation direction and rotation angle of the output shaft 210 of the motor 200 are determined based on the difference; finally, the motor 200 is controlled to operate in the rotation direction and rotation angle, so that the potentiometer 300 and the focus ring 100 rotate together until the output voltage of the potentiometer 300 is the target output voltage, at which time the focus ring 100 also drives the lens assembly to move to the target position to complete the focusing action.

[0074] The present invention also provides a control method for a projection device, such as Figure 6 The specific structure of the projection device refers to the above embodiment. Since the projection device adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here. The control method of the projection device includes:

[0075] determining a target position of the lens assembly;

[0076] determining a target output voltage of the potentiometer according to a target position of the lens assembly;

[0077] Get the current output voltage of the potentiometer 300;

[0078] Determine the operation data of the motor 200 according to the difference between the target output voltage and the current output voltage;

[0079] According to the operation data, the motor 200 is controlled to drive the focus ring 100 to rotate so as to move the lens assembly to a target position.

[0080] The specific structure of the projection device in this embodiment refers to the above-mentioned embodiment. The position of the lens assembly has a corresponding relationship with the output voltage of the potentiometer 300. Optionally, the relationship between any position Lx of the lens assembly and the output voltage Voutx corresponding to the potentiometer 300 can be understood as: Lx-L1=k*(Voutx-Vout1). Thus, the current position of the lens assembly can be determined by the output voltage of the potentiometer 300, and the target output voltage of the potentiometer 300 can also be determined according to the target position of the lens assembly.

[0081] Specifically, the target position of the lens assembly can be calculated by the distance between the lens assembly and the projection screen. It is understandable that the best clarity position of the projected image can be determined according to the focal length of the lens assembly and the size of the projection screen, and this best clarity position can be the target position of the lens assembly.

[0082] In this embodiment, the operation data of the motor 200 can be understood as the target direction and rotation angle that the output shaft 210 of the motor 200 needs to rotate.

[0083] When focusing is required, the distance between the lens assembly and the projection screen is first detected by the distance sensor, and the target position of the lens assembly is calculated according to the distance and the size of the projection screen; then, based on the corresponding relationship between the position of the lens assembly and the output voltage of the potentiometer 300, the target output voltage of the potentiometer 300 corresponding to the target position is determined; then, the current output voltage of the potentiometer 300 obtained is compared with the target output voltage to obtain a difference, and the target direction and rotation angle of the output shaft 210 of the motor 200 required to rotate are determined according to the difference; finally, the motor 200 is controlled to operate according to the target direction and rotation angle, so that the potentiometer 300 and the focus ring 100 rotate together until the output voltage of the potentiometer 300 is the target output voltage, at which time the focus ring 100 also drives the lens assembly to move to the target position to complete the focusing action.

[0084] It should be noted that the step of obtaining the current output voltage of the potentiometer 300 may be performed before or after determining the target position of the lens assembly, or may be performed simultaneously.

[0085] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A focusing mechanism, characterized in that: Applied to a projection device, the projection device includes a lens assembly; the focusing mechanism includes: A focus ring, used for transmission connection with the lens assembly, wherein the rotation of the focus ring can drive the lens assembly to move along the axial direction of the focus ring; a motor, drivingly connected to the focus ring to drive the focus ring to rotate; and A potentiometer is driven and connected to the motor to locate the rotation position of the focus ring.

2. The focusing mechanism according to claim 1, characterized in that: The motor has an output shaft, the output shaft is provided with a first gear, the outer periphery of the focus ring is provided with a second gear, and the second gear is meshed and connected with the first gear; The potentiometer has a transmission shaft, and the transmission shaft is drivingly connected to the output shaft.

3. The focusing mechanism according to claim 2, characterized in that: An assembly hole is provided at the end of the transmission shaft, the output shaft is inserted into the assembly hole, and the central axis of the output shaft is colinear with the central axis of the transmission shaft.

4. The focusing mechanism according to claim 3, characterized in that: The assembly hole is a special-shaped hole; the shaft end of the output shaft is a special-shaped shaft, and the outer peripheral shape of the shaft end of the output shaft is matched with the hole peripheral shape of the assembly hole.

5. The focusing mechanism according to any one of claims 2 to 4, characterized in that: The potentiometer comprises a fixed resistor and a moving contact that can move along the fixed resistor, and the transmission shaft is connected to the moving contact and is used to drive the moving contact to move along the fixed resistor to change the output voltage of the potentiometer; The output shaft can drive the transmission shaft to rotate, so that the output voltage of the potentiometer is adjusted to a target output voltage.

6. The focusing mechanism according to claim 5, characterized in that: The potentiometer has an a pin and a c pin respectively connected to the two ends of the fixed resistor, the c pin is grounded, and the a pin is connected to a preset reference voltage; the voltage at the moving contact is the output voltage of the potentiometer.

7. The focusing mechanism according to any one of claims 1 to 4, characterized in that: The focus ring is provided with at least one spiral guide groove for slidingly cooperating with the guide rod on the lens assembly.

8. A projection device, characterized in that: It comprises a control module, a lens assembly and a focusing mechanism as claimed in any one of claims 1 to 7; The lens assembly is transmission-mounted on the focus ring; The motor and the potentiometer are both electrically connected to the control module.

9. The projection device according to claim 8, characterized in that: A distance sensor electrically connected to the control module is also included, and the distance sensor is used to detect the distance between the lens assembly and the projection screen.

10. A control method for the projection device according to claim 8 or 9, characterized in that: The method comprises: determining a target position of the lens assembly; determining a target output voltage of the potentiometer according to a target position of the lens assembly; Obtaining the current output voltage of the potentiometer; Determining the operation data of the motor according to the difference between the target output voltage and the current output voltage; According to the operation data, the motor is controlled to drive the focus ring to rotate so that the lens assembly moves to a target position.

11. The method according to claim 10, characterized in that The step of determining the target position of the lens assembly comprises: The distance between the lens assembly and the projection screen is acquired, and the target position of the lens assembly is determined according to the distance.

12. The method according to claim 10, characterized in that There is a preset linear correspondence between the position of the lens assembly and the output voltage of the potentiometer.

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