Projection device and automatic focusing method thereof

Abstract

The invention discloses a projection device and an automatic focusing method thereof. A projection distance between a projection lens of the projection device and a projection surface is detected to generate a distance detection signal. The control unit updates the extended lookup table according to the original lookup table, the distance detection signal, the optimal motor step number position and the adjustment completion time point, wherein the optimal motor step number position and the adjustment completion time point are obtained by the manual focusing operation. And executing an automatic focusing operation according to the distance detection signal and the updated extension lookup table. According to the projection device and the automatic focusing method thereof provided by the invention, the automatic focusing effect of the projection device can be effectively improved, and the use convenience of the projection device is improved.

Description

Technical Field

[0001] The invention relates to a display device, and in particular to a projection device and an automatic focusing method thereof. Background Art

[0002] Recently, the visibility of projectors using rangefinder autofocus technology in the market has become increasingly higher. Rangefinder autofocus technology generally refers to the use of distance-measuring components, such as laser rangefinder sensors, infrared rangefinder sensors, or ultrasonic rangefinder sensors, etc., to measure the projection distance between the projection screen and the projector lens. The projector automatically drives the motor connected to the lens to move to the corresponding position according to the projection distance to drive the lens to retract and retract, thereby obtaining a clear projection image.

[0003] Since the relationship between projection distance and motor position is not a perfect linear relationship, ideally, the more samples of the motor position corresponding to the projection distance are set in advance, the closer it can be to the theoretical design value of the relationship curve between projection distance and motor position, and the better the autofocus effect. However, considering the production time, it is impractical to establish a large number of samples. Therefore, interpolation is usually used to calculate the corresponding motor position for focusing, and the autofocus image at this time may not be the clearest. As a result, users often need to perform manual focus, which causes inconvenience in use.

[0004] In addition, the projector may also wear out its motor parts or reduce the performance of the distance sensor after long-term use, so that the originally set projection distance and motor position can no longer achieve the best focus effect.

[0005] The "background technology" section is only used to help understand the content of the present invention. Therefore, the content disclosed in the "background technology" section may contain some known technologies that are not known to those skilled in the art. The content disclosed in the "background technology" section does not represent the content or the problems to be solved by one or more embodiments of the present invention, nor does it mean that it has been known or recognized by those skilled in the art before the application of the present invention. Summary of the invention

[0006] The present invention provides a projection device and an automatic focusing method thereof, which can effectively improve the automatic focusing effect of the projection device and enhance the use convenience of the projection device.

[0007] Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

[0008] To achieve one or part or all of the above purposes or other purposes, the projection device of the present invention includes a projection lens, a distance detector, a motor, a driving circuit and a control unit, and the projection device is used to project an image beam to a projection surface. The projection lens is used to project an image beam. The distance detector detects the projection distance between the projection lens and the projection surface to generate a distance detection signal. The motor is coupled to the projection lens to control the movement of the projection lens. The driving circuit is coupled to the motor, and drives the motor to move the projection lens to perform an automatic focus operation. The control unit is coupled to the distance detector and the driving circuit, and stores an original lookup table and an extended lookup table, wherein the original lookup table records a plurality of preset projection distances and a plurality of preset motor step positions corresponding thereto. The control unit is configured to perform: receiving a distance detection signal from the distance detector, updating the extended lookup table according to the original lookup table, the distance detection signal, the optimal motor step position and the adjustment completion time point, and controlling the driving circuit to perform an automatic focus operation according to the distance detection signal and the updated extended lookup table, wherein the optimal motor step position and the adjustment completion time point are obtained by a manual focus operation.

[0009] The present invention also provides an automatic focusing method for a projection device, comprising the following steps. The projection distance between the projection lens of the projection device and the projection surface is detected to generate a distance detection signal. A control unit is provided to receive the distance detection signal, wherein the control unit stores an original lookup table and an extended lookup table, the original lookup table records a plurality of preset projection distances and a plurality of preset motor step positions corresponding thereto, and the control unit updates the extended lookup table according to the original lookup table, the distance detection signal, the optimal motor step position, and the adjustment completion time point, wherein the optimal motor step position and the adjustment completion time point are obtained by a manual focus operation. The automatic focusing operation is performed according to the distance detection signal and the updated extended lookup table.

[0010] Based on the above, the embodiment of the present invention can update the extended lookup table according to the original lookup table, the distance detection signal, the optimal motor step position and the adjustment completion time point, and control the driving circuit to perform the autofocus operation according to the distance detection signal and the updated extended lookup table, wherein the optimal motor step position and the adjustment completion time point are obtained by the manual focus operation. In this way, the extended lookup table is continuously updated by the manual focus operation, and the driving circuit is controlled to perform the autofocus operation according to the updated extended lookup table. The autofocus effect of the projection device can be improved without adding additional focus correction operations to the user, and the convenience of use of the projection device is improved. Even if the motor parts are worn out or the performance of the distance sensor is reduced, the autofocus effect is not affected.

[0011] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of a projection device according to an embodiment of the present invention.

[0013] Figure 2 is a schematic diagram of a projection device according to another embodiment of the present invention.

[0014] Figure 3 is a schematic diagram of an auto-focus function menu according to an embodiment of the present invention.

[0015] Figure 4 It is a schematic diagram of the relationship between the projection distance and the motor position according to an embodiment of the present invention.

[0016] Figure 5 It is a schematic diagram of restoring an auto-focus function menu according to an embodiment of the present invention.

[0017] Figure 6 The present invention is a flowchart of an automatic focusing method for a projection device according to an embodiment of the present invention.

[0018] Figure 7 is a flow chart of a method for updating an extended lookup table according to an embodiment of the present invention.

[0019] Figure 8 The invention is a flowchart of a method for restoring an extended lookup table according to an embodiment of the invention. DETAILED DESCRIPTION

[0020] The other technical contents, features and effects of the present invention mentioned above will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as: up, down, left, right, front or back, etc., are only reference directions in the accompanying drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention. In addition, the term "coupling" mentioned in the following embodiments may refer to any direct or indirect means of connection. In addition, the term "signal" may refer to at least one current, voltage, charge, temperature, data, electromagnetic wave or any other one or more signals.

[0021] Figure 1 is a schematic diagram of a projection device according to an embodiment of the present invention, please refer to Figure 1The projection device 100 includes a distance detector 102, a control unit 104, a driving circuit 106, a motor 108 and a projection lens 110. The control unit 104 is coupled to the distance detector 102 and the driving circuit 106, and the motor 108 is coupled to the driving circuit 106 and the projection lens 110. The image beam L1 generated by the projection device 100 can be projected onto a projection surface (such as a projection screen, but not limited thereto) through the projection lens 110. The distance detector 102 can detect the projection distance between the projection lens 110 and the projection surface to generate a distance detection signal, and can be implemented, for example, with a laser distance sensor (such as a ToF sensor), an infrared distance sensor or an ultrasonic distance sensor, but not limited thereto. The control unit 104 stores an original lookup table and an extended lookup table, wherein the original lookup table records a plurality of preset projection distances and a plurality of preset motor step positions corresponding thereto, respectively. The control unit 104 may receive a distance detection signal generated by the distance detector 102, and update the extended lookup table according to the original lookup table, the distance detection signal, the optimal motor step position, and the adjustment completion time point, wherein the optimal motor step position and the adjustment completion time point are obtained by a manual focus operation. The updated extended lookup table may include a plurality of preset projection distances and a plurality of preset motor step positions in the original lookup table, the projection distance corresponding to the distance detection signal, the time corresponding to the completion of the manual focus operation, and the motor step position (i.e., the adjustment completion time point and the optimal motor step position) when the manual focus operation is completed. The control unit 104 may control the driving circuit 106 to perform an auto focus operation according to the distance detection signal and the updated extended lookup table, that is, the control unit 104 controls the driving circuit 106 to drive the motor 108 to move the projection lens 110 to perform an auto focus operation.

[0022] By continuously updating the extended lookup table using the manual focus operation, the relationship between the projection distance and the motor step position in the extended lookup table can be improved and optimized without requiring additional focus correction operations by the user. When the drive circuit is controlled to perform an autofocus operation based on the updated extended lookup table, the projection device can achieve the best autofocus effect, thereby improving the ease of use of the projection device. Even if the motor parts are worn out or the performance of the ranging sensor is reduced, the autofocus effect is not affected.

[0023] Furthermore, the projection device 100 further includes an input unit 206. The control unit 104 of the projection device 100 may be configured as follows: Figure 2As shown, the present invention comprises a processing unit 202 and a storage unit 204, wherein the processing unit 202 is coupled to the distance detector 102, the driving circuit 106, the storage unit 204 and the input unit 206. The processing unit 202 may be implemented by a processor, such as (but not limited to) a central processing unit (CPU), or other programmable general-purpose or special-purpose microcontroller unit (MCU), microprocessor, the storage unit 204 may include a non-volatile memory (such as ROM or flash memory) and a volatile memory (such as RAM), and the input unit 206 may be a touch display panel or a physical button, but is not limited thereto. The original lookup table and the extended lookup table can be stored in the non-volatile memory of the storage unit 204. When the processing unit 202 performs an autofocus operation, the extended lookup table can be stored in the volatile memory for use. After the extended lookup table is updated, the updated extended lookup table is stored back in the non-volatile memory to synchronously update the extended lookup table stored in the volatile memory.

[0024] In addition, the input unit 206 is used to accept user operations to set various functions of the projection device 100. For example, the projection device 100 projects an on-screen menu adjustment interface (OSD) to display the following Figure 3 The projection device 100 can respond to the user's operation display as shown in the auto focus function menu. Figure 3 The auto-focus function menu shown in the figure presents an item "Enable auto-focus learning function" in the menu, and the auto-focus learning function is enabled or disabled according to the user's operation. When the auto-focus learning function is enabled, the processing unit 202 can perform the operation of updating the extended lookup table as described above, and when the auto-focus learning function is disabled, the processing unit 202 only performs the auto-focus operation according to the original lookup table.

[0025] Specifically, when updating the extended lookup table, the processing unit 202 can determine whether the projection distance corresponding to the distance detection signal from the distance detector 102 is equal to one of the multiple preset projection distances. If the projection distance is equal to one of the multiple preset projection distances, the projection distance, the optimal motor step position, and the adjustment completion time point are updated to the extended lookup table to replace the corresponding original preset projection distance and the preset motor step position. If the projection distance is different from any of the multiple preset projection distances, the projection distance corresponding to the distance detection signal, the corresponding optimal motor step position, and the adjustment completion time point are added to the extended lookup table.

[0026] In some embodiments, the processing unit 202 may also determine whether the optimal motor step position is within a reasonable range when the manual focus operation is completed. If the optimal motor step position is within a reasonable range, the projection distance, the optimal motor step position, and the adjustment completion time point corresponding to the distance detection signal may be directly updated to the extended lookup table. The reasonable range of the optimal motor step position may be, for example Figure 4 As shown, defined by curves A1 and A2, the original lookup table records a plurality of preset projection distances and a plurality of preset motor step positions, and the curve A0 formed falls between the curves A1 and A2. In the present embodiment, the curve A0 is a curve defined based on the preset sampling points P1 to P5 stored in the original lookup table, and the curves A1 and A2 can be defined, for example, based on the allowable error range (e.g., the allowable upper limit and the allowable lower limit of the error of the motor step position) corresponding to the motor step position of each preset sampling point P1 to P5 on the curve A0.

[0027] If the processing unit 202 determines that the optimal motor step position is not within a reasonable range when the manual focus operation is completed, the processing unit 202 can control the projection device 100 to project a confirmation menu, and determine whether to update the projection distance, the optimal motor step position, and the adjustment completion time point to the extended lookup table based on the confirmation information generated by the user operating the input unit 206. Figure 4 In the embodiment, when the manual focus operation is completed, the distance detector 102 measures the projection distance as 2200 mm, for example, and the motor step position after manual adjustment is 970, for example. The processing unit 202 determines that the point PE1 corresponding to the projection distance and the motor step position falls outside the range defined by the curves A1 and A2, and when the user's confirmation information indicates that the projection distance, the optimal motor step position, and the adjustment completion time point are not updated to the extended lookup table, the processing unit 202 does not update the extended lookup table to exclude inappropriate sampling points. By continuously updating the extended lookup table in this way, the curve A0 can be closer and closer to the ideal curve. When the processing unit 202 performs the automatic focus operation, if the projection distance corresponding to the distance detection signal is not recorded in the extended lookup table, the processing unit 202 can also use the interpolation method to calculate the sampling points recorded in the extended lookup table to obtain the accurate motor step position. In some embodiments, if the user's confirmation information is not received, for example, when the user does not operate the input unit 206, the processing unit 202 may cancel the confirmation menu after a preset period of time has passed in the projection confirmation menu, and does not update the extended lookup table. In other embodiments, if the point PE1 falls outside the range defined by the curves A1 and A2, the user instructs to update the projection distance, the optimal motor step position, and the adjustment completion time point to the extended lookup table (that is, the user replies that the image is clear but the image is actually not clear), the user may restore the settings of the projection device 100 (at the time of the projection device 100) if the user feels that the image is not clear in the future. Figure 5 detailed description when available).

[0028] On the contrary, if the manual focus operation is completed, the processing unit 202 determines the point corresponding to the projection distance and the motor step position (eg Figure 4 The point PN1 shown in FIG. 1 falls within the range defined by the curves A1 and A2. The processing unit 202 may record the projection distance, the final motor step position, and the adjustment completion time point as a sampling point, and update it to the extended lookup table in the volatile memory and the non-volatile memory of the storage unit 204 in a replacement or addition manner. After updating the extended lookup table in the storage unit 204 (volatile memory), the processing unit 202 may reorder the sampling points in the extended lookup table, for example, reorder the sorted sampling points according to the projection distance, so as to speed up the calculation of the motor step position using the interpolation method.

[0029] In addition, the adjustment completion time recorded in the extended lookup table can be used to restore the settings of the projection device 100, for example, to restore the extended lookup table to the state corresponding to the adjustment completion time. For example, when the user performs a restore operation through the input unit 206, the processing unit 202 can control the projection device 100 to display the projection screen menu adjustment interface (On-Screen Display, OSD) such as Figure 5 The Reset Auto Focus function menu is shown. The Reset Auto Focus function menu is used to select the time point to be restored, such as Figure 5 In the embodiment, the extended lookup table can be restored to a state one day ago, one week ago, or to a factory setting, but it is not limited thereto. The number of selectable restoration time points is related to the adjustment completion time points stored in the extended lookup table. The processing unit 202 can generate an instruction to restore the extended lookup table to a specific time point or an instruction to restore to the original setting according to the user's selection of the time point to be restored, and restore the extended lookup table to the corresponding time point. In detail, the sampling points of the adjustment completion time point later than the specific time point in the extended lookup table of the non-volatile memory can be removed, and the extended lookup table in the non-volatile memory that has completed the removal operation is loaded into the volatile memory, and the sampling points of the extended lookup table are reordered according to the projection distance. Similarly, if the user chooses to restore the extended lookup table to the factory setting, the processing unit 202 can restore the extended lookup table to a state having only a plurality of preset projection distances and their corresponding plurality of preset motor step positions in the original lookup table according to the instruction to restore to the original setting. In detail, according to the instruction to restore to the original settings, the extended lookup table in the non-volatile memory can be replaced with the record content of the original lookup table, so that the extended lookup table in the non-volatile memory is restored to only have multiple preset projection distances of the original lookup table and their corresponding multiple preset motor step positions, and then the sampling points of the extended lookup table are reordered.

[0030] Figure 6 It is a flow chart of an automatic focusing method of a projection device according to an embodiment of the present invention. It can be seen from the above embodiments that the automatic focusing method of the projection device may at least include the following steps. First, the projection distance between the projection lens of the projection device and the projection surface is detected to generate a distance detection signal (step S602). Next, a control unit is provided to receive the distance detection signal, wherein the control unit stores an original lookup table and an extended lookup table, wherein the original lookup table and the extended lookup table record a plurality of preset projection distances and their corresponding plurality of preset motor step positions, and the control unit updates the extended lookup table according to the original lookup table, the distance detection signal, the optimal motor step position and the adjustment completion time point (step S604), wherein the optimal motor step position and the adjustment completion time point are obtained by manual focus operation. Finally, an automatic focus operation is performed according to the distance detection signal and the updated extended lookup table (step S606).

[0031] Specifically, the method for updating the extended lookup table can be as follows: Figure 7 As shown, first, at the beginning (step S702), that is, the user starts to operate the projection device 100, such as manual focus operation. The projection device 100 has already preset the mode of the auto focus function, such as mode 1, when it leaves the factory. When the user completes the manual focus operation for the first time, the projection device 100 will automatically project the on-screen menu adjustment interface (OSD) to display the menu of whether to turn on the auto focus learning function (such as Figure 3 ), or for example, mode 2, allowing the user to actively operate the input unit 206 to display the following through the on-screen menu adjustment interface (OSD) Figure 3The autofocus function menu shown is not limited to this. Taking mode 1 as an example, when the user starts to operate the projection device 100 and completes the manual focus operation, the projection device 100 will automatically project a menu for whether to turn on the autofocus function, asking whether to turn on the autofocus learning function (step S704). If the autofocus learning function is turned on, determine whether the optimal motor step position is within a reasonable range (step S706). If the optimal motor step position is within a reasonable range, record the projection distance, the final motor step position, and the adjustment completion time point as a sampling point (step S708), and then determine whether this sampling point already exists in the extended lookup table in the volatile memory (step S710), for example, determine whether the projection distance corresponding to the distance detection signal is equal to one of multiple preset projection distances. If the sampling point already exists in the extended lookup table in the volatile memory, the sampling point is updated to the extended lookup table in the volatile memory and the non-volatile memory (step S712). For example, when the projection distance is equal to one of the multiple preset projection distances, the projection distance, the optimal motor step position and the adjustment completion time point are updated to the extended lookup table in the volatile memory and the non-volatile memory. On the contrary, if the sampling point does not exist in the extended lookup table, that is, the projection distance is different from any of the multiple preset projection distances, a new sampling point is added to the extended lookup table in the non-volatile memory (step S718), that is, the projection distance, the optimal motor step position and the adjustment completion time point are added, and the sampling point is added to the extended lookup table in the volatile memory according to the order of the projection distance (step S720). In this way, when the motor step position is calculated using the interpolation method, the speed of calculating the motor step position can be accelerated.

[0032] In addition, in step S706, if it is determined that the optimal motor step position is not within a reasonable range, a confirmation menu may be provided to ask the user whether the image projected by the projection device is clear (step S714) to confirm whether to update the optimal motor step position to the extended lookup table. If the user replies that the image is clear in the confirmation menu in step S716, the process proceeds to step S708 to perform a series of subsequent actions to update the extended lookup table. If the user replies that the image is not clear in the confirmation menu in step S716, the method flow for updating the extended lookup table ends, and the extended lookup table is not updated.

[0033] In addition, the method of restoring the extended lookup table can be as follows Figure 8As shown, first, the projection device is controlled to project an on-screen menu adjustment interface (OSD) to display a restore autofocus function menu for the user to select a desired restore time point (step S802), wherein the adjustment completion time point is related to the desired restore time point. Next, based on the user's selection of the desired restore time point, a restore to a specific time point instruction or a restore to original setting instruction is generated (step S804). In the case of generating a restore to a specific time point instruction, the extended lookup table is restored according to the restore to a specific time point instruction. Specifically, the extended lookup table in the non-volatile memory that is later than the specific time point (e.g. Figure 5 The sampling points of the adjustment completion time points (one day before, one week before) are removed (step S806), that is, the adjustment completion time points, projection distances and optimal motor step positions that are later than the specific time points are removed, and the extended lookup table in the non-volatile memory that has completed the removal operation is loaded into the volatile memory, and the sampling points of the extended lookup table are reordered according to the projection distance (step S808) to speed up the speed of obtaining the motor step position using the interpolation method. In addition, if the restore to original settings is selected in step S804, the extended lookup table in the non-volatile memory is replaced with the record content of the original lookup table according to the instruction to restore to the original settings (step S810), so that the extended lookup table in the non-volatile memory is restored to only have multiple preset projection distances and their corresponding multiple preset motor step positions of the original lookup table, and then enter step S808 again to reorder the sampling points of the extended lookup table.

[0034] In summary, the embodiments of the present invention can update the extended lookup table according to the original lookup table, the distance detection signal, the optimal motor step position and the adjustment completion time point, and control the driving circuit to perform the autofocus operation according to the distance detection signal and the updated extended lookup table, wherein the optimal motor step position and the adjustment completion time point are obtained by the manual focus operation. In this way, the extended lookup table is continuously updated by the manual focus operation, and the driving circuit is controlled to perform the autofocus operation according to the updated extended lookup table. This can improve the autofocus effect of the projection device without adding additional focus correction operations to the user, improve the convenience of use of the projection device, and even if the motor parts are worn out or the performance of the ranging sensor is reduced, it will not affect the autofocus effect. In some embodiments, the extended lookup table can also be restored according to the adjustment completion time point to further improve the convenience of use of the projection device.

[0035] However, the above is only a preferred embodiment of the present invention, and it should not be used to limit the scope of the implementation of the present invention. That is, all simple equivalent changes and modifications made according to the claims and the content of the invention are still within the scope of the patent of the present invention. In addition, any embodiment or claim of the present invention does not need to achieve all the purposes, advantages or features disclosed by the present invention. In addition, the abstract and title (invention name) are only used to assist in the retrieval of patent documents, and are not used to limit the scope of rights of the present invention. Furthermore, the first, second, etc. mentioned in the specification are only used to indicate the names of the components, and are not used to limit the upper or lower limits on the number of components.

Claims

1. A projection device for projecting an image beam onto a projection surface, characterized in that: The projection device includes a projection lens, a distance detector, a motor, a driving circuit and a control unit, wherein: The projection lens is used to project the image light beam; The distance detector detects the projection distance between the projection lens and the projection surface to generate a distance detection signal; The motor is coupled to the projection lens to control the movement of the projection lens; The driving circuit is coupled to the motor, driving the motor to move the projection lens to perform an auto-focus operation; and The control unit is coupled to the distance detector and the driving circuit, and stores an original lookup table and an extended lookup table, wherein the original lookup table records a plurality of preset projection distances and a plurality of preset motor step positions corresponding thereto, and the control unit is configured to execute: receiving the distance detection signal from the distance detector; updating the extended lookup table according to the original lookup table, the distance detection signal, the optimal motor step position and the adjustment completion time point, wherein the optimal motor step position and the adjustment completion time point are obtained by a manual focus operation; and The driving circuit is controlled to perform the auto-focus operation according to the distance detection signal and the updated extended lookup table.

2. The projection device according to claim 1, characterized in that: The extended lookup table includes the plurality of preset projection distances and the plurality of preset motor step positions, and the control unit is configured to execute: determining whether the projection distance corresponding to the distance detection signal is equal to one of the plurality of preset projection distances, If the projection distance is equal to one of the plurality of preset projection distances, updating the projection distance, the optimal motor step position and the adjustment completion time point into the extended lookup table; as well as If the projection distance is different from any one of the plurality of preset projection distances, the projection distance, the optimal motor step position and the adjustment completion time point are added to the extended lookup table.

3. The projection device according to claim 1, characterized in that: The control unit is configured to perform: The projection device is controlled to project a restore autofocus function menu, wherein the restore autofocus function menu is used to select a desired restore time point, wherein the adjustment completion time point is related to the desired restore time point, and based on the user's selection of the desired restore time point, a restore to a specific time point instruction or a restore to original setting instruction is generated.

4. The projection device according to claim 3, characterized in that: The control unit is configured to perform: The extended lookup table is restored according to the restore to specific time point instruction.

5. The projection device according to claim 3, characterized in that: The control unit is configured to perform: According to the instruction to restore to the original setting, the extended lookup table is restored to only have the plurality of preset projection distances and the plurality of preset motor step positions corresponding thereto.

6. The projection device according to claim 1, characterized in that: The control unit is configured to perform: When the manual focus operation is completed, it is determined that the optimal motor step position is within a reasonable range, so that the projection distance, the optimal motor step position and the adjustment completion time point are updated to the extended lookup table.

7. The projection device according to claim 1, characterized in that: The control unit is configured to perform: When the manual focus operation is completed, determining that the optimal motor step position is not within a reasonable range; A confirmation message from a user is received to determine whether to update the projection distance, the optimal motor step position, and the adjustment completion time point to the extended lookup table.

8. The projection device according to claim 1, characterized in that: The control unit is configured to perform: The projection device is controlled to project an auto-focus function menu, wherein the auto-focus function menu is used to set whether to start the auto-focus learning function.

9. An automatic focusing method for a projection device, characterized in that: include: Detecting the projection distance between the projection lens of the projection device and the projection surface to generate a distance detection signal; Providing a control unit to receive the distance detection signal, wherein the control unit stores an original lookup table and an extended lookup table, the original lookup table records a plurality of preset projection distances and a plurality of preset motor step positions corresponding thereto, and the control unit updates the extended lookup table according to the original lookup table, the distance detection signal, an optimal motor step position, and an adjustment completion time point, wherein the optimal motor step position and the adjustment completion time point are obtained by a manual focus operation; and An auto-focus operation is performed according to the distance detection signal and the updated extended lookup table.

10. The automatic focusing method of a projection device according to claim 9, characterized in that: The extended lookup table includes the plurality of preset projection distances and the plurality of preset motor step positions, and the automatic focusing method of the projection device includes: Determining whether the projection distance corresponding to the distance detection signal is equal to one of the plurality of preset projection distances; If the projection distance is equal to one of the plurality of preset projection distances, updating the projection distance, the optimal motor step position and the adjustment completion time point into the extended lookup table; and If the projection distance is different from any one of the plurality of preset projection distances, the projection distance, the optimal motor step position and the adjustment completion time point are added to the extended lookup table.

11. The automatic focusing method of a projection device according to claim 9, characterized in that: include: The projection device is controlled to project a restore autofocus function menu, wherein the restore autofocus function menu is used to select a desired restore time point, wherein the adjustment completion time point is related to the desired restore time point, and based on the user's selection of the desired restore time point, a restore to a specific time point instruction or a restore to original setting instruction is generated.

12. The automatic focusing method of a projection device according to claim 11, characterized in that: include: The extended lookup table is restored according to the restore to specific time point instruction.

13. The automatic focusing method of a projection device according to claim 11, characterized in that: include: According to the instruction to restore to the original setting, the extended lookup table is restored to only have the plurality of preset projection distances and the plurality of preset motor step positions corresponding thereto.

14. The automatic focusing method of a projection device according to claim 9, characterized in that: include: When the manual focus operation is completed, it is determined that the optimal motor step position is within a reasonable range, and the projection distance, the final motor step position, and the adjustment completion time point are updated to the extended lookup table.

15. The automatic focusing method of a projection device according to claim 9, characterized in that: include: When the manual focus operation is completed, it is determined that the final motor step position is not within a reasonable range, and whether to update the projection distance, the final motor step position and the adjustment completion time point to the extended lookup table is determined based on the user's confirmation information.

16. The automatic focusing method of a projection device according to claim 9, characterized in that: include: The projection device is controlled to project an auto-focus function menu, wherein the auto-focus function menu is used to set whether to start the auto-focus learning function.

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