WO2021244399A1

WO2021244399A1 - Projection apparatus and automatic focusing method therefor

Info

Publication number: WO2021244399A1
Application number: PCT/CN2021/096460
Authority: WO
Inventors: 余新; 吴超; 许擎栋; 赵鹏
Original assignee: 深圳光峰科技股份有限公司
Priority date: 2020-06-02
Filing date: 2021-05-27
Publication date: 2021-12-09
Also published as: CN113766193A

Abstract

Disclosed in the present application are a projection apparatus and an automatic focusing method therefor. The method comprises: by performing spectrum analysis on a currently projected virtual focus picture image, acquiring spectrum information of a current virtual focal spot according to spectrum information of the current virtual focus picture image, the current virtual focal spot being a spot formed by any one pixel point of the current virtual focus picture image; afterwards, searching for spectrum information that matches the spectrum information of the current virtual focal spot from spectrum information of multiple prestored preset virtual focal spots, so as to obtain target spectrum information, then a defocus distance corresponding to the target spectrum information may be acquired, and then controlling a motor to drive a lens group to move a target defocus distance, so as to implement focusing. By the means of the foregoing, the present application can reduce the calculation performance requirements of a focusing process, increase the efficiency of automatic focusing and increase the response speed of automatic focusing.

Description

Projection device and its automatic focusing method

Technical field

This application relates to the field of projection technology, in particular to a projection device and an automatic focusing method thereof.

Background technique

During the use of the projector, the distance between the projector and the projection surface is also different due to the different use scenes. In order to obtain a clearer projection image, the focal length of the lens group is generally adjusted accordingly.

Existing focusing methods usually use contrast focusing to achieve auto focusing, that is, to intercept a small area of the virtual focus projected image. The small area contains the image area with high original contrast, such as the edge area of the color block. Because the virtual focus will reduce the contrast of the image, the contrast is calculated and the motor is driven to move the lens group to find the position of the lens group when the image contrast is the highest, so as to complete the autofocus.

However, in the above focusing method, it is necessary to continuously calculate the image contrast, and each time a calculation result is obtained, the motor must be driven until the maximum contrast of the image is found. This is not only a large amount of calculation, low efficiency, and prone to overshoot. Adjust the phenomenon, increase the response time of auto focus.

Summary of the invention

The main technical problem to be solved by this application is to provide a projection device and an auto-focusing method thereof, which can reduce the calculation performance requirements of the focusing process, and improve the efficiency of auto-focusing and the response speed of auto-focusing.

An embodiment of the present application provides an automatic focusing method of a projection device, including:

Obtain the projected picture image after the structured light pattern is projected onto the plane as the current virtual focus picture image;

Performing frequency spectrum analysis on the current virtual focus picture image to obtain first frequency spectrum information of the current virtual focus picture image;

Acquiring second spectrum information of a current virtual focus light spot according to the first spectrum information, where the current virtual focus light spot is a light spot formed by any pixel of the current virtual focus picture image;

Search for spectrum information matching the second spectrum information from the pre-stored spectrum information of a plurality of preset virtual focus spots to obtain target spectrum information, wherein the spectrum information of each preset virtual focus spot corresponds to a defocus Distance, and then obtain the defocus distance corresponding to the target spectrum information, and then obtain the target defocus distance;

The motor is controlled to drive the lens group to move the target defocus distance to achieve focusing.

An embodiment of the application also provides a projection device, including:

The first acquisition module is used to acquire the projected screen image after the structured light pattern is projected onto the plane as the current virtual focus screen image;

The analysis module is configured to perform a frequency spectrum analysis on the current virtual focus picture image to obtain the first frequency spectrum information of the current virtual focus picture image;

A second acquisition module, configured to acquire second spectrum information of a current virtual focus spot according to the first spectrum information, where the current virtual focus spot is a spot formed by any pixel of the current virtual focus picture image;

The third acquisition module is configured to search for spectrum information matching the second spectrum information from the pre-stored spectrum information of a plurality of preset virtual focus light spots to acquire target spectrum information, wherein each preset virtual focus light spot The frequency spectrum information corresponding to a defocus distance, and then the defocus distance corresponding to the target frequency spectrum information is obtained, and then the target defocus distance is obtained;

The control module is used to control the motor to drive the lens group to move the target defocus distance to achieve focusing.

In the auto-focusing method of the present application, spectrum analysis is performed on the currently projected defocused picture image, and then the spectrum information of the current defocused light spot is obtained according to the spectrum information of the current defocused picture image, and the current defocused light spot is the current defocused picture image For the spot formed by any one pixel point, the spectrum information of the multiple preset virtual focus spots stored in advance is searched for the spectrum information that matches the spectrum information of the current virtual focus spot to obtain the target spectrum information, which can then be obtained The defocus distance corresponding to the target spectrum information, and then control the motor to drive the lens group to move the target defocus distance to achieve focusing. Therefore, this solution directly obtains the defocus distance of the current virtual focus image by performing spectrum analysis on the current virtual focus image. , So that the motor controls the lens group to move to the target position in one step (that is, the position after moving the target defocus distance) to complete focusing, without the need for the motor to control the movement of the lens group step by step, which can greatly improve the focusing efficiency and help improve The response rate of auto focus, and it does not need to do the contrast calculation repeatedly, which can reduce the calculation performance requirements.

Description of the drawings

FIG. 1 is a schematic flowchart of an automatic focusing method of a projection device provided by an embodiment of the present application;

Fig. 2 is a schematic structural diagram of a projection device provided by an embodiment of the present application.

detailed description

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

Referring to FIG. 1, the automatic focusing method of the projection device of the embodiment of the present application includes the following steps:

S1. Obtain a projection screen image after the structured light pattern is projected onto a plane, and use it as a current virtual focus screen image.

When the projection device is turned on, the projection device projects structured light onto the plane, thereby projecting a picture of the structured light pattern on the plane, which is the projected picture image after the structured light pattern is projected onto the plane. In the embodiment of the present application, the projection device is provided with a photographing mechanism for photographing the projection screen to obtain the projection screen image, and the projection screen image obtained by the shooting is used as the current virtual focus screen image.

Among them, the structured light pattern may be, for example, a cosine structured light pattern, or may also be another structured light pattern with a simple frequency spectrum and controllable frequency components. Cosine structured light is a structured light with a cosine distribution of light intensity in the horizontal direction.

S2. Perform frequency spectrum analysis on the current virtual focus picture image to obtain first frequency spectrum information of the current virtual focus picture image.

The image is actually a two-dimensional matrix with spatial information. The frequency spectrum of the image is its two-dimensional discrete Fourier transform. The spectrum analysis of the image is the analysis of the amplitude of the image spectrum. Therefore, in this embodiment of the present application, the acquired first spectrum information includes the amplitude spectrum of the current virtual focus picture image.

S3. Acquire the second spectrum information of the current virtual focus spot according to the first spectrum information, where the current virtual focus spot is a spot formed by any pixel of the current virtual focus picture image.

The projection image produces a virtual focus, that is, the projection image is blurred, that is, each pixel in the virtual focus image forms a spot larger than the actual size of the pixel, and because the illuminance of the projection range is relatively uniform, each pixel is formed The expansion law of the light spot is basically the same, and it is distributed in the form of a Gaussian light spot. The virtual focus picture image can be considered as a clear picture image obtained by convolution of a certain size of convolution kernel, and the size of the convolution kernel is related to the degree of defocus of the virtual focus picture, and the distribution form of the convolution kernel is related to the intensity distribution of the beam. In general, it is a Gaussian kernel, that is to say, the defocused picture image is a clear picture image obtained by Gaussian kernel convolution, and the defocused light spot is a Gaussian light spot. Therefore, the virtual focus of the defocused picture image can be expressed in mathematical form as The convolution of the defocused light spot and the clear picture image, and further, the spatial convolution of the Gaussian light spot and the clear picture image.

Among them, according to the Fourier analysis principle, the frequency spectrum of the result of spatial convolution is equivalent to the product of the two spectrums of the convolution. Therefore, the frequency spectrum of the imaginary image image is equal to the product of the Gaussian spot spectrum and the frequency spectrum of the clear image image. . Therefore, after determining the frequency spectrum information of the virtual focus picture image and the frequency spectrum information of the clear picture image, the spectrum information of the Gaussian spot can be obtained in reverse.

Therefore, in step S1, acquiring the second spectrum information of the current virtual focus spot according to the first spectrum information may specifically include the following sub-steps:

(11) Acquire the third frequency spectrum information of the predetermined clear picture image.

In the embodiment of the present application, the predetermined clear picture image is a clear cosine structured light pattern picture image. Among them, the spectrum information of a clear picture image can be pre-stored as the third spectrum information, so that the pre-stored third spectrum information of the clear picture image can be directly obtained; or a clear picture image can be preset to be used during the focusing process. Obtain the clear picture image and perform spectrum analysis on it to obtain the spectrum information of the clear picture image as the third spectrum information.

(12) Acquire the first extreme value of the spectrum of the current virtual-focus image according to the first frequency spectrum information, and acquire the second extreme value of the frequency spectrum of the predetermined clear image according to the third frequency spectrum information.

Wherein, the first extreme value and the second extreme value may be the maximum value of the amplitude spectrum.

(13) According to the ratio of the second extreme value to the first extreme value, obtain the second frequency spectrum information of the current virtual focus spot.

Thus, by using the ratio of the first extreme value and the second extreme value, the spectrum information of the virtual focus spot, that is, the second spectrum information, can be inferred backward.

S4. Search for spectrum information matching the second spectrum information from the pre-stored spectrum information of a plurality of preset virtual focus spots to obtain target spectrum information, wherein the spectrum information of each preset virtual focus spot corresponds to a defocus Distance, and then obtain the defocus distance corresponding to the target spectrum information, and then obtain the target defocus distance.

Wherein, before step S4, the following steps are further included:

(21) In a dark environment, project a number of preset virtual focus spots on the plane in sequence.

Among them, the projection device can be controlled to perform pixel point projection, and the position of the lens group can be changed by moving the motor, so that different virtual focus spots can be obtained.

(22) Obtain the picture image of each preset virtual focus spot.

Among them, each time a preset defocused light spot is projected, a picture image of the preset defocused light spot is acquired by the shooting mechanism.

(23) Perform frequency spectrum analysis on the picture image of each preset virtual focus light spot to obtain the frequency spectrum information of each preset virtual focus light spot.

(24) Calculate the defocus distance corresponding to each preset virtual focus spot according to the spectral information of each preset virtual focus spot, and establish the spectral information of each preset virtual focus spot and the separation distance corresponding to each preset virtual focus spot. Correspondence between focal distances.

Specifically, the pixels on the projection plane can be considered to be formed by the convergence of a small light cone, and the virtual focus spot is the light spot formed after the pixel points are blurred. Therefore, the virtual focus light spot is also formed by the convergence of the light cone. The spreading law of the light spot is related to the opening angle of the light cone. According to the principle of conservation of optical expansion, the opening angle of the light cone on the virtual focus spot is determined by the size of the spatial light modulator, the opening angle of the light cone on the spatial light modulator, and the size of the projection screen where the preset virtual focus spot is obtained. Therefore, first obtain the light cone opening angle on the spatial light modulator, the size of the spatial light modulator, and the size of the projection screen where the preset virtual focus spot is obtained, and then according to the formula Ω _Screen ·S _Screen =Ω _SLM ·S _SLM , Calculate the light cone aperture angle on the preset virtual focus spot, where Ω _Screen represents the light cone aperture angle of the _{preset virtual focus light spot, S Screen} represents the size of the projection screen where the preset virtual focus light spot is located, and Ω _SLM represents spatial light modulation The opening angle of the light cone on the sensor, S _SLM represents the size of the spatial light modulator.

Afterwards, the defocus distance corresponding to each preset virtual focus spot is calculated according to the frequency spectrum information of each preset virtual focus spot and the light cone opening angle on the corresponding preset virtual focus spot. Specifically, the Gaussian function representing each preset virtual focus spot is determined according to the frequency spectrum information of each preset virtual focus spot, and then according to the formula Ω _Screen ·d=9πσ ² , the corresponding value of each preset virtual focus spot is calculated Defocus distance, where d represents the defocus distance corresponding to the preset virtual focus spot, and σ represents the standard deviation of the Gaussian function corresponding to the preset virtual focus spot.

(25) Store the frequency spectrum information of each preset virtual focus spot and the corresponding defocus distance.

Through the above method, the defocus distance corresponding to a series of preset virtual focus spots can be calculated, and then the spectral information and the corresponding defocus distance of each preset virtual focus spot are stored, and the corresponding relationship between the two is established .

Therefore, in step S4, when the second spectrum information of the current virtual focus spot is determined, the second spectrum information is matched with the spectrum information of a plurality of preset virtual focus spots stored in advance, when the second spectrum information is When the spectrum information of one of the preset virtual focus spots is matched, the defocus distance corresponding to the matched spectrum information is taken as the target defocus distance.

S5. Control the motor to drive the lens group to move the target defocus distance to achieve focusing.

Therefore, in the embodiment of the present application, by performing spectrum analysis on the current virtual focus picture image, the defocus distance of the current virtual focus picture image can be directly obtained, so that the motor control lens group can move to the target position in one step (that is, the moving target distance The position after the focal distance) to complete the focusing without the need for the motor to control the movement of the lens group step by step. This can greatly improve the focusing efficiency and help improve the response rate of autofocus. There is no need to repeat the contrast calculation, which can reduce the calculation. Performance requirements.

Referring to FIG. 2, an embodiment of the present application also provides a projection device, which includes a first acquisition module 201, an analysis module 202, a second acquisition module 203, a third acquisition module 204, and a control module 205.

Wherein, the first acquisition module 201 may be, for example, a photographing mechanism, such as a camera, for acquiring a projection screen image after the structured light pattern is projected onto a plane, as the current virtual focus screen image.

When the projection device is turned on, the projection device projects structured light onto the plane, thereby projecting a picture of the structured light pattern on the plane, which is the projected picture image after the structured light pattern is projected onto the plane. The first acquisition module 201 acquires the projection screen image by shooting the projection screen, and the projection screen image obtained by shooting is used as the current virtual focus screen image.

The analysis module 202 is configured to perform a frequency spectrum analysis on the current virtual focus picture image to obtain the first frequency spectrum information of the current virtual focus picture image.

The second acquisition module 203 is configured to acquire the second spectrum information of the current virtual focus light spot according to the first spectrum information, and the current virtual focus light spot is a light spot formed by any pixel of the current virtual focus picture image.

The defocused picture image is obtained by Gaussian kernel convolution of the clear picture image, and the defocused light spot is Gaussian light spot. Therefore, the virtual focus of the defocused picture image can be expressed as the convolution of the defocused light spot and the clear picture image in mathematical form. , Further speaking, perform spatial convolution for the Gaussian spot and the clear picture image. Among them, according to the Fourier analysis principle, the frequency spectrum of the result of spatial convolution is equivalent to the product of the two spectrums of the convolution. Therefore, the frequency spectrum of the imaginary image image is equal to the product of the Gaussian spot spectrum and the frequency spectrum of the clear image image. . Therefore, after determining the frequency spectrum information of the virtual focus picture image and the frequency spectrum information of the clear picture image, the spectrum information of the Gaussian spot can be obtained in reverse.

Therefore, the second obtaining module 203 is specifically configured to obtain the third spectrum information of the predetermined clear image; then obtain the first extreme value of the current virtual focus image spectrum according to the first spectrum information, and obtain the predetermined clear image spectrum according to the third spectrum information According to the ratio of the second extreme value and the first extreme value, the second spectrum information of the current virtual focus spot is obtained.

The third acquiring module 204 is configured to search for spectrum information matching the second spectrum information from the pre-stored spectrum information of a plurality of preset virtual focus light spots, so as to acquire target spectrum information, wherein the frequency spectrum of each preset virtual focus light spot The information corresponds to a defocus distance, and then the defocus distance corresponding to the target spectrum information is obtained, and then the target defocus distance is obtained.

Further, the projection device further includes a calculation module 206 and a storage module 207. Wherein, before the third acquiring module 204 acquires the target spectrum information, the first acquiring module 201 is also used to acquire a plurality of preset virtual focus spot picture images, and the multiple preset virtual focus spot pictures are the projection device in a dark environment, A picture formed by sequentially projecting a plurality of preset virtual focus light spots onto the plane. The analysis module 202 is further configured to perform a spectrum analysis on the picture image of each preset virtual focus light spot, so as to obtain the frequency spectrum information of each preset virtual focus light spot.

The calculation module 206 is configured to calculate the defocus distance corresponding to each preset virtual focus light spot according to the frequency spectrum information of each preset virtual focus light spot, and establish that the frequency spectrum information of each preset virtual focus light spot corresponds to each preset virtual focus light spot Correspondence between the defocus distances.

Specifically, the pixel points on the projection plane can be considered to be formed by the convergence of a small light cone, and the virtual focus spot is the light spot formed after the pixel points are blurred. Therefore, the virtual focus light spot is also formed by the convergence of the light cone. The spreading law of the light spot is related to the opening angle of the light cone. According to the principle of conservation of optical expansion, the opening angle of the light cone on the virtual focus spot is determined by the size of the spatial light modulator, the opening angle of the light cone on the spatial light modulator, and the size of the projection screen where the preset virtual focus spot is obtained. Therefore, the calculation module 206 is specifically configured to obtain the aperture angle of the light cone on the spatial light modulator, the size of the spatial light modulator, and the size of the projection screen where the preset virtual focus spot is located, and then according to the formula Ω _Screen ·S _Screen = Ω _SLM · S _SLM , calculate the light cone opening angle on the preset virtual focus spot, where Ω _Screen represents the light cone opening angle of the _{preset virtual focus light spot, S Screen} represents the size of the projection screen where the preset virtual focus light spot is located, Ω _SLM represents the opening angle of the light cone on the spatial light modulator, and S _SLM represents the size of the spatial light modulator.

After that, the calculation module 206 calculates the defocus distance corresponding to each preset virtual focus light spot according to the frequency spectrum information of each preset virtual focus light spot and the light cone opening angle on the corresponding preset virtual focus light spot. Specifically, the Gaussian function representing each preset virtual focus spot is determined according to the frequency spectrum information of each preset virtual focus spot, and then according to the formula Ω _Screen ·d=9πσ ² , the corresponding value of each preset virtual focus spot is calculated Defocus distance, where d represents the defocus distance corresponding to the preset virtual focus spot, and σ represents the standard deviation of the Gaussian function corresponding to the preset virtual focus spot.

The storage module 207 is configured to store the frequency spectrum information of each preset virtual focus spot and the corresponding defocus distance.

Thus, the third acquisition module 203 can search for spectrum information matching the second spectrum information from the spectrum information of a plurality of pre-stored preset virtual focus spots, so as to acquire the target spectrum information, and obtain the spectrum information corresponding to the target spectrum information. Focus distance to get the target defocus distance.

The control module 205 is used to control the motor-driven lens group to move the target defocus distance to achieve focusing.

Therefore, in this embodiment, by performing spectrum analysis on the current virtual focus image, the defocus distance of the current virtual focus image can be directly obtained, so that the motor-controlled lens group can move to the target position in one step (that is, the moving target is out of focus). The position after the distance) to complete the focusing without the need for the motor to control the movement of the lens group step by step, which can greatly improve the focusing efficiency and help improve the response rate of autofocus, and does not require repeated contrast calculations, which can reduce the calculation performance Require.

The above are only implementations of this application, and do not limit the scope of this application. Any equivalent structure or equivalent process transformation made using the content of the description and drawings of this application, or directly or indirectly applied to other related technical fields, The same reasoning is included in the scope of patent protection of this application.

Claims

An automatic focusing method of a projection device, characterized in that it comprises:

Obtain the projected picture image after the structured light pattern is projected onto the plane as the current virtual focus picture image;

Performing frequency spectrum analysis on the current virtual focus picture image to obtain first frequency spectrum information of the current virtual focus picture image;

Acquiring second spectrum information of a current virtual focus light spot according to the first spectrum information, where the current virtual focus light spot is a light spot formed by any pixel of the current virtual focus picture image;

Search for spectrum information matching the second spectrum information from the pre-stored spectrum information of a plurality of preset virtual focus spots to obtain target spectrum information, wherein the spectrum information of each preset virtual focus spot corresponds to a defocus Distance, and then obtain the defocus distance corresponding to the target spectrum information, and then obtain the target defocus distance;

The motor is controlled to drive the lens group to move the target defocus distance to achieve focusing.
The method according to claim 1, wherein the acquiring the second spectrum information of the current virtual focus spot according to the first spectrum information comprises:

Acquiring third frequency spectrum information of a predetermined clear picture image;

Acquiring a first extreme value of a current virtual focus image frequency spectrum according to the first frequency spectrum information, and acquiring a second extreme value of a predetermined clear image image frequency spectrum according to the third frequency spectrum information;

According to the ratio of the second extremum to the first extremum, the second spectrum information of the current virtual focus spot is acquired.
The method according to claim 1, characterized in that, before acquiring the projection screen image after the structured light pattern is projected onto the plane, the method further comprises:

In a dark environment, project multiple preset virtual focus spots to the plane in sequence;

Obtain the picture image of each preset virtual focus spot;

Perform spectrum analysis on the picture image of each preset virtual focus spot to obtain the spectrum information of each preset virtual focus spot;

Calculate the defocus distance corresponding to each preset virtual focus spot according to the spectral information of each preset virtual focus spot, and establish the difference between the spectral information of each preset virtual focus spot and the defocus distance corresponding to each preset virtual focus spot Correspondence between;

Store the frequency spectrum information of each preset virtual focus spot and the corresponding defocus distance.
The method according to claim 3, wherein the calculating the defocus distance corresponding to each preset virtual focus spot according to the frequency spectrum information of each preset virtual focus spot comprises:

Acquiring the light cone opening angle on the spatial light modulator, the size of the spatial light modulator, and acquiring the size of the projection screen where the preset virtual focus spot is located;

According to the formula Ω Screen ·S Screen =Ω SLM ·S SLM , calculate the light cone aperture angle on the preset virtual focus spot, where Ω Screen represents the light cone aperture angle of the preset virtual focus light spot, and S Screen represents the preset virtual focus light spot The size of the projection screen where Ω SLM represents the opening angle of the light cone on the spatial light modulator, and S SLM represents the size of the spatial light modulator;

According to the frequency spectrum information of each preset virtual focus spot and the light cone opening angle on the corresponding preset virtual focus spot, the defocus distance corresponding to each preset virtual focus spot is calculated.
The method according to claim 4, characterized in that, according to the spectral information of each preset virtual focus spot and the light cone opening angle corresponding to the preset virtual focus spot, the distance corresponding to each preset virtual focus spot is calculated Focus distance, including:

Determine the Gaussian function representing each preset virtual focus spot according to the frequency spectrum information of each preset virtual focus spot,

According to the formula Ω Screen ·d=9πσ 2 , calculate the defocus distance corresponding to each preset virtual focus spot, where d represents the defocus distance corresponding to the preset virtual focus spot, and σ represents the Gaussian function of the preset virtual focus spot. Standard deviation.
A projection device, characterized in that it comprises:

The first acquisition module is used to acquire the projected screen image after the structured light pattern is projected onto the plane as the current virtual focus screen image;

The analysis module is configured to perform a frequency spectrum analysis on the current virtual focus picture image to obtain the first frequency spectrum information of the current virtual focus picture image;

A second acquisition module, configured to acquire second spectrum information of a current virtual focus spot according to the first spectrum information, where the current virtual focus spot is a spot formed by any pixel of the current virtual focus picture image;

The third acquisition module is configured to search for spectrum information matching the second spectrum information from the pre-stored spectrum information of a plurality of preset virtual focus light spots to acquire target spectrum information, wherein each preset virtual focus light spot The frequency spectrum information corresponding to a defocus distance, and then the defocus distance corresponding to the target frequency spectrum information is obtained, and then the target defocus distance is obtained;

The control module is used to control the motor to drive the lens group to move the target defocus distance to achieve focusing.
The projection device according to claim 6, wherein the second acquisition module is specifically configured to:

Acquiring third frequency spectrum information of a predetermined clear image;

Acquiring a first extreme value of a current virtual focus image frequency spectrum according to the first frequency spectrum information, and acquiring a second extreme value of a predetermined clear image frequency spectrum according to the third frequency spectrum information;

According to the ratio of the second extremum to the first extremum, the second spectrum information of the current virtual focus spot is acquired.
The projection device according to claim 6, further comprising a calculation module and a storage module;

The first acquisition module is also used to acquire a plurality of preset virtual focus spot screen images, the plurality of preset virtual focus spot images are generated by the projection device sequentially projecting a plurality of preset virtual focus spots onto a plane in a dark environment The picture formed;

The analysis module is also used to perform spectrum analysis on the picture image of each preset virtual focus spot to obtain the frequency spectrum information of each preset virtual focus spot;

The calculation module is used to calculate the defocus distance corresponding to each preset virtual focus light spot according to the frequency spectrum information of each preset virtual focus light spot, and establish the frequency spectrum information of each preset virtual focus light spot and each preset virtual focus light spot Correspondence between the corresponding defocus distances;

The storage module stores the frequency spectrum information of each preset virtual focus spot and the corresponding defocus distance.
The projection device according to claim 8, wherein the calculation module is specifically configured to:

Obtain the size and light cone opening angle of the spatial light modulator, and obtain the size of the projection screen image where the preset virtual focus spot is located;

According to the formula Ω Screen ·S Screen =Ω SLM ·S SLM , calculate the light cone opening angle of the preset virtual focus spot, where Ω Screen represents the light cone opening angle of the preset virtual focus light spot, and S Screen represents the preset virtual focus light spot. The size of the projected screen image, Ω SLM represents the light cone opening angle of the spatial light modulator, and S SLM represents the size of the spatial light modulator;

According to the frequency spectrum information of each preset virtual focus spot and the light cone opening angle corresponding to the preset virtual focus spot, the defocus distance corresponding to each preset virtual focus spot is calculated.
The projection device according to claim 9, wherein the calculation module is specifically configured to:

Determine the Gaussian function representing each preset virtual focus spot according to the frequency spectrum information of each preset virtual focus spot,

According to the formula Ω Screen ·d=9πσ 2 , calculate the defocus distance corresponding to each preset virtual focus spot, where d represents the defocus distance corresponding to the preset virtual focus spot, and σ represents the Gaussian function of the preset virtual focus spot. Standard deviation.