WO2023088329A1

WO2023088329A1 - Projection device and projection image correction method

Info

Publication number: WO2023088329A1
Application number: PCT/CN2022/132368
Authority: WO
Inventors: 王昊; 甄凌云; 王英俊; 卢平光; 何营昊; 岳国华
Original assignee: 海信视像科技股份有限公司
Priority date: 2021-11-16
Filing date: 2022-11-16
Publication date: 2023-05-25
Also published as: CN114885136A; CN114205570B; CN114727079B; CN114466173A; CN114827563B; CN118077192A; CN114205570A; CN118104231A; CN114401390A; CN114885138A; CN118104230A; CN114727079A; WO2023087950A1; CN114885137B; CN115022606B; CN114401390B; CN115174877B; CN115022606A; CN115174877A; CN114827563A

Abstract

The present application relates to a projection device and a projection image correction method, which may solve, to a certain extent, the problems of large device parameter errors caused by assembly errors of projector components, and low accuracy and poor effects of projection image correction results. The projection device comprises: an optical machine; a camera; and a controller, which is configured to control, after detecting that the projection device moves, the optical machine to project a calibration chart to a blank region of a calibration plate, so as to determine calibration parameters; determining a conversion matrix between a world coordinate system and an optical machine coordinate system on the basis of the calibration parameters and the coordinates of an image of the calibration plate obtained by the camera in a camera coordinate system; and according to the conversion matrix, converting first coordinates of a vertex of a preset projection region in the world coordinate system to the optical machine coordinate system to obtain second coordinates, and controlling the optical machine to project playback content to the second coordinates.

Description

Projection device and projection image correction method

Cross References to Related Applications

This application claims the priority of the Chinese patent application submitted on November 16, 2021, with application number 202111355866.0; and submitted on February 23, 2022, with application number 202210168263.8, the entire contents of which are incorporated in this application by reference.

technical field

The present application relates to the technical field of display devices, and in particular, to a projection device and a projection image correction method.

Background technique

The movement of projection equipment such as a projector causes deviations in projection angle and projection distance, which will cause the projection image to not be completely projected to the preset projection area, resulting in a deformed projection image; the projection image correction function configured by the projection equipment can be corrected The display position and display shape of the distorted projection image make the projection image completely and accurately displayed in the preset projection area.

In the realization of some projection image correction, it is usually necessary to call the optical-mechanical internal parameters that have been marked as equipment parameters when the projection device is manufactured, and the external parameters between the optical-mechanical camera, and then measure the angle between the optical-mechanical plane and the projection surface, and finally call The correction calculation model realizes projection image correction.

However, due to the inevitable processing and assembly errors in the actual production and assembly process of the projection equipment, the actual values of the above internal and external parameters are inconsistent with the theoretical values, resulting in a decrease in the accuracy of the projection equipment when correcting the projected image.

Contents of the invention

An embodiment of the present application provides a projection device, including: an optical machine for projecting playback content to a preset projection area on a projection surface; a camera for acquiring an image of a calibration board, the calibration board includes a calibration chart and a blank area, The calibration plate is set on the projection surface; the controller is configured to: after detecting the movement of the projection device, control the optical machine to project the calibration chart card to the blank area of the calibration plate to determine the calibration parameters; based on the Calibration parameters, and the coordinates of the calibration plate image acquired by the camera in the camera coordinate system, determine the conversion matrix between the world coordinate system and the optical-mechanical coordinate system; according to the above conversion matrix, the world coordinate system described below The first coordinates of the vertex of the preset projection area are transformed into the optical-mechanical coordinate system to obtain the second coordinates, and the optical-mechanical projection playback content is controlled to the second coordinates.

An embodiment of the present application provides a projection image correction method for a projection device. The method includes: after detecting that the projection device moves, project a calibration chart card to a blank area of the calibration board to determine calibration parameters. The calibration parameters include light The internal reference of the machine and the external reference between the optical machine and the camera, the calibration board includes a calibration chart and a blank area, and the calibration board is arranged on the projection surface; based on the calibration parameters, and the acquired calibration board image in the camera coordinate system coordinates, determine the transformation matrix between the world coordinate system and the optical-mechanical coordinate system, the origin of the world coordinate system is at the origin of the optical-mechanical coordinate system, and its XOY plane is parallel to the projection plane; the rectangle of the preset projection area The first coordinates of the vertex in the world coordinate system are converted to the second coordinates in the optical-mechanical coordinate system based on the above transformation matrix, and the playback content is projected to the second coordinates.

Description of drawings

FIG. 1A shows a schematic diagram of placement of projection equipment according to some embodiments of the present application;

FIG. 1B shows a schematic diagram of an optical path of a projection device according to some embodiments of the present application;

FIG. 2 shows a schematic diagram of a circuit architecture of a projection device according to some embodiments of the present application;

FIG. 3 shows a schematic structural diagram of a projection device according to some embodiments of the present application;

FIG. 4 shows a schematic structural diagram of a projection device according to another embodiment of the present application;

FIG. 5 shows a schematic diagram of a circuit structure of a projection device according to some embodiments of the present application;

FIG. 6 shows a schematic diagram of a system framework for realizing display control by a projection device according to some embodiments of the present application;

FIG. 7A shows a schematic diagram of a projected image deformed by a projection device according to another embodiment of the present application;

FIG. 7B shows a schematic diagram of the relative positions of the projection device and the calibration plate according to another embodiment of the present application;

FIG. 7C shows a schematic diagram of image correction based on optomechanical camera calibration according to another embodiment of the present application;

FIG. 7D shows a schematic diagram of image correction based on optomechanical camera calibration according to another embodiment of the present application;

FIG. 7E shows a schematic diagram of image correction based on optomechanical camera calibration according to another embodiment of the present application;

FIG. 7F shows a schematic diagram of image correction based on optomechanical camera calibration according to another embodiment of the present application;

FIG. 7G shows a schematic diagram of a calibration plate according to another embodiment of the present application;

Fig. 8A shows a schematic diagram of planar imaging of a digital micromirror device of a projection device according to another embodiment of the present application;

FIG. 8B shows a schematic diagram of expanding the imaging surface during the process of calibrating parameters of the projection device according to another embodiment of the present application;

FIG. 9A shows a schematic flowchart of determining a calibration parameter by a projection device according to another embodiment of the present application;

FIG. 9B shows a schematic diagram of a user interface of a projection device according to another embodiment of the present application;

Fig. 10 shows a schematic diagram of the signaling interaction sequence of the projecting device implementing the emissive eye function according to another embodiment of the present application;

FIG. 11 shows a schematic diagram of a signaling interaction sequence for a projection device to implement a display screen correction function according to another embodiment of the present application;

FIG. 12 shows a schematic flowchart of a projection device implementing an autofocus algorithm according to another embodiment of the present application;

FIG. 13 shows a schematic flowchart of a projection device implementing keystone correction and obstacle avoidance algorithms according to another embodiment of the present application;

FIG. 14 shows a schematic flowchart of a projection device implementing a screen entry algorithm according to another embodiment of the present application;

Fig. 15 shows a schematic flowchart of implementing an eye-prevention algorithm by a projection device according to another embodiment of the present application.

Detailed ways

In order to make the purpose and implementation of the application clearer, the following will clearly and completely describe the exemplary implementation of the application in conjunction with the accompanying drawings in the exemplary embodiment of the application. Obviously, the described exemplary embodiment is only the present application. Claim some of the examples, not all of them.

FIG. 1A is a schematic diagram of placement of a projection device according to some embodiments of the present application.

In some embodiments, a projection device provided by the present application includes a projection screen 1 and a device 2 for projection. The projection screen 1 is fixed on the first position, and the device 2 for projection is placed on the second position, so that the projected picture coincides with the projection screen 1. This step is performed by professional after-sales technicians, that is, the second position is The best placement of the projection device 2.

FIG. 1B is a schematic diagram of an optical path of a projection device according to some embodiments of the present application.

An embodiment of the present application provides a projection device, including a laser light source 100 , an optical machine 200 , a lens 300 , and a projection medium 400 . Wherein, the laser light source 100 provides illumination for the light machine 200, and the light machine 200 modulates the light beam, and outputs it to the lens 300 for imaging, and projects it to the projection medium 400 to form a projection image.

In some embodiments, the laser light source of the projection device includes a laser component and an optical lens component, and the light beam emitted by the laser component can pass through the optical lens component to provide illumination for the optical machine. Among them, for example, optical lens components require a higher level of environmental cleanliness and airtight level sealing; while the chamber where the laser component is installed can be sealed with a lower level of dustproof level to reduce sealing costs.

In some embodiments, the light engine 200 of the projection device may be implemented to include a blue light engine, a green light engine, and a red light engine, and may also include a heat dissipation system, a circuit control system, and the like. It should be noted that, in some embodiments, the light emitting component of the projection device may also be realized by an LED light source.

In some embodiments, the present application provides a projection device, including a three-color light engine and a controller; wherein, the three-color light engine is used to modulate and generate laser light containing pixels in a user interface, including a blue light engine, a green light engine, and a red light engine. Optical machine; the controller is configured to: obtain the average gray value of the user interface; when it is determined that the average gray value is greater than the first threshold and its duration is greater than the time threshold, control the operating current value of the red optical machine according to The preset gradient value is lowered to reduce the heating of the three-color light engine. It can be found that by reducing the operating current of the red light engine integrated in the three-color light engine, the overheating of the red light engine can be controlled, so as to control the overheating of the three-color light engine and the projection device.

The light machine 200 can be implemented as a three-color light machine, and the three-color light machine integrates a blue light machine, a green light machine, and a red light machine.

Hereinafter, the embodiment of the present application will be described by taking the light machine 200 of the projection device as an example including a blue light machine, a green light machine, and a red light machine.

In some embodiments, the optical system of the projection device is composed of a light source part and an optical machine part. The function of the light source part is to provide illumination for the light machine, and the function of the light machine part is to modulate the illumination beam provided by the light source, and finally form Projected screen.

In some embodiments, the light source part specifically includes a housing, a laser component, and an optical lens component. The light beam emitted by the laser component is shaped and combined by the optical lens component, so as to provide illumination for the optical machine. Among them, laser components include light-emitting chips, collimating lenses, wires and other devices, but they are usually packaged components. When used as components, compared with optical lenses, which are also precision components, the cleanliness of optical lenses to the environment The requirements will be higher, because if there is dust on the surface of the lens, on the one hand, it will affect the light processing effect of the lens, resulting in the attenuation of the emitted light brightness, and finally affect the effect of the projection device projecting the image through the lens; on the other hand, the dust will absorb high-energy light. The laser beam generates heat, which can easily damage the lens.

In some embodiments, the optical lens assembly includes at least a convex lens, wherein the convex lens is an integral part of the telescope system, and the telescope system is usually composed of a convex lens and a concave lens, which are used to reduce the beam of the laser beam with a larger area to form a smaller area. laser beam. The convex lens usually has a large surface and is usually installed near the light output of the laser. It can receive a large area of laser beams and also facilitate the transmission of beams as a large window to reduce light loss.

The optical lens assembly may also include a concave lens, a light combining mirror, a light homogenizing component, or a speckle dissipating component, etc., which are used to reshape and combine the laser beam to meet the requirements of the lighting system.

In some embodiments, the laser assembly includes a red laser module, a green laser module, and a blue laser module, and each laser module and the corresponding installation port are dust-proof through a sealing ring (either fluorine rubber or other sealing materials can be used). Sealed installation.

FIG. 2 is a schematic diagram of a circuit architecture of a projection device according to some embodiments of the present application.

In some embodiments, the projection device provided by the present disclosure includes multiple sets of lasers. By setting a brightness sensor in the light output path of the laser light source, the brightness sensor can detect the first brightness value of the laser light source and send the first brightness value to the display. Control circuit.

The display control circuit can obtain the second brightness value corresponding to the driving current of each laser, and when it is determined that the difference between the second brightness value of the laser and the first brightness value of the laser is greater than the difference threshold, determine that the laser has COD (Catastrophic optical damage) failure; then the display control circuit can adjust the current control signal of the corresponding laser driver component of the laser until the difference is less than or equal to the difference threshold, thereby eliminating the COD failure of the blue laser; the projection device The COD failure of the laser can be eliminated in time, the damage rate of the laser is reduced, and the image display effect of the projection device is ensured.

In some embodiments, the projection device may include a display control circuit 10, a laser light source 20, at least one laser driving component 30, and at least one brightness sensor 40, and the laser light source 20 may include a one-to-one corresponding At least one laser. Wherein, the at least one includes one or more, and a plurality refers to two or more.

In some embodiments, the projection device includes a laser driver assembly 30 and a brightness sensor 40. Correspondingly, the laser light source 20 includes three lasers that correspond one-to-one to the laser driver assembly 30, and the three lasers can be blue lasers respectively. 201 , red laser 202 and green laser 203 . Wherein, the blue laser 201 is used to emit blue laser, the red laser 202 is used to emit red laser, and the green laser 203 is used to emit green laser. In some embodiments, the laser driving component 30 may be implemented to include a plurality of sub-laser driving components corresponding to lasers of different colors.

The display control circuit 10 is used to output the primary color enable signal and the primary color current control signal to the laser drive assembly 30 to drive the laser to emit light. Specifically, as shown in FIG. 2 , the display control circuit 10 is connected to the laser drive assembly 30 for outputting At least one enable signal corresponding to the three primary colors of each frame image in the multi-frame display image, the at least one enable signal is respectively transmitted to the corresponding laser drive assembly 30, and the output and each frame image At least one current control signal corresponding to each of the three primary colors transmits the at least one current control signal to the corresponding laser driving component 30 respectively. For example, the display control circuit 10 may be a microcontroller unit (microcontroller unit, MCU), also known as a single-chip microcomputer. Wherein, the current control signal may be a pulse width modulation (pulse width modulation, PWM) signal.

In some embodiments, the display control circuit 10 can output the blue PWM signal B_PWM corresponding to the blue laser 201 based on the blue primary color component of the image to be displayed, and output the blue PWM signal B_PWM corresponding to the red laser 202 based on the red primary color component of the image to be displayed. The red PWM signal R_PWM outputs the green PWM signal G_PWM corresponding to the green laser 203 based on the green primary color component of the image to be displayed. The display control circuit can output the enable signal B_EN corresponding to the blue laser 201 based on the lighting duration of the blue laser 201 in the driving cycle, and output the enable signal B_EN corresponding to the red laser 202 based on the lighting duration of the red laser 202 in the driving cycle. The enable signal R_EN of the green laser 203 outputs an enable signal G_EN corresponding to the green laser 203 based on the lighting duration of the green laser 203 in the driving cycle.

The laser drive assembly 30 is connected to the corresponding laser, and is used to provide a corresponding drive current to the connected laser in response to the received enabling signal and current control signal, and each laser is used for the drive current provided by the laser drive assembly 30 Glow under the drive.

In some embodiments, the blue laser 201 , the red laser 202 and the green laser 203 are respectively connected to the laser driving assembly 30 . The laser driving component 30 can provide corresponding driving current to the blue laser 201 in response to the blue PWM signal B_PWM and the enable signal B_EN sent by the display control circuit 10 . The blue laser 201 is used to emit light under the driving current.

The brightness sensor is arranged in the light output path of the laser light source, usually on one side of the light output path, without blocking the light path. As shown in Figure 2, at least one brightness sensor 40 is arranged in the light path of the laser light source 20, and each brightness sensor is connected with the display control circuit 10 for detecting the first brightness value of a laser, and the first brightness value sent to the display control circuit 10.

In some embodiments, the display control circuit 10 is also used to obtain the second brightness value corresponding to the driving current of each laser, if it is detected that the difference between the second brightness value of the laser and the first brightness value of the laser is greater than The difference threshold indicates that the laser has a COD failure, and the display control circuit 10 can adjust the current control signal of the laser drive assembly 30 until the difference is less than or equal to the difference threshold, that is, the COD of the laser is eliminated by reducing the driving current of the laser. Fault. Specifically, both the first luminance value and the second luminance value are represented as light output power values, wherein the second luminance value may be pre-stored, or may be a luminance value sent back by a luminance sensor in a normal lighting state. If a COD failure occurs to the laser, usually its optical output power drops suddenly, the first brightness value returned by the brightness sensor will be less than half of the normal second brightness value. When the above failure is confirmed, the display control circuit will reduce the current control signal of the laser drive component corresponding to the laser, and continuously collect and compare the brightness signals returned by the brightness sensor.

In some embodiments, if the detected difference between the second brightness value of the laser and the first brightness value of the laser is less than or equal to the difference threshold, it indicates that the laser does not have a COD failure, and the display control circuit 10 does not need to adjust and The laser corresponds to the current control signal of the laser driving component 30 .

Wherein, the display control circuit 10 may store the corresponding relationship between the current and the brightness value. The luminance value corresponding to each current in the corresponding relationship is the initial luminance value that the laser can emit when the laser works normally under the driving of the current (that is, no COD failure occurs). For example, the brightness value may be the initial brightness when the laser is first turned on when it is driven by the current.

In some embodiments, the display control circuit 10 can obtain the second brightness value corresponding to the driving current of each laser from the corresponding relationship, the driving current is the current actual working current of the laser, and the second brightness value corresponding to the driving current is the brightness value that the laser can emit when it works normally under the driving current. The difference threshold may be a fixed value pre-stored in the display control circuit 10 .

In some embodiments, when the display control circuit 10 adjusts the current control signal of the laser drive component 30 corresponding to the laser, it can reduce the duty cycle of the current control signal of the laser drive component 30 corresponding to the laser, thereby reducing the driving force of the laser. current.

In some embodiments, the brightness sensor 40 can detect the first brightness value of the blue laser 201 and send the first brightness value to the display control circuit 10 . The display control circuit 10 can obtain the driving current of the blue laser 201, and obtain the second brightness value corresponding to the driving current from the corresponding relationship between the current and the brightness value. Then detect whether the difference between the second luminance value and the first luminance value is greater than the difference threshold, if the difference is greater than the difference threshold, it indicates that the blue laser 201 has a COD failure, and the display control circuit 10 can reduce the difference with the difference threshold. The current control signal of the laser driving component 30 corresponding to the blue laser 201 . Afterwards, the display control circuit 10 can acquire the first luminance value of the blue laser 201 and the second luminance value corresponding to the driving current of the blue laser 201 again, and the difference between the second luminance value and the first luminance value is greater than When the difference threshold is reached, the current control signal of the laser driving component 30 corresponding to the blue laser 201 is lowered again. This loops until the difference is less than or equal to the difference threshold. Therefore, by reducing the driving current of the blue laser 201 , the COD failure of the blue laser 201 is eliminated.

In some embodiments, the display control circuit 10 can monitor in real time whether each laser has COD failure. And when it is determined that any laser has a COD failure, the COD failure of the laser is eliminated in time, the duration of the COD failure of the laser is reduced, the damage of the laser is reduced, and the image display effect of the projection device is ensured.

Fig. 3 is a schematic structural diagram of a projection device according to some embodiments of the present application.

In some embodiments, the laser light source in the projection device may include a blue laser 201-20, a red laser 202-20, and a green laser 203-20, and the projection device may also be called a three-color projection device. The color lasers 201-20, the red lasers 202-20 and the green lasers 203-20 are all MCL-type packaged lasers, which are small in size and facilitate the compact arrangement of optical paths. In other embodiments, the laser light source can also be a monochromatic laser or a dual-color laser.

In some embodiments, referring to FIG. 3, the at least one brightness sensor may include a first brightness sensor 401-40, a second brightness sensor 402-40, and a third brightness sensor 403-40, wherein the first brightness sensor 401-40 is a blue light brightness sensor or a white light brightness sensor, the second brightness sensor 402-40 is a red light brightness sensor or a white light brightness sensor, and the third brightness sensor 403-40 is a green light brightness sensor or a white light brightness sensor.

Wherein, the first brightness sensor 401-40 is set in the light output path of the blue laser 201-20, specifically, it can be set on the side of the light output path of the collimated beam of the blue laser 201-20. Similarly, the second The brightness sensor 402-40 is arranged in the light-emitting path of the red laser 202-20, specifically arranged on one side of the light-emitting path of the collimated beam of the red laser 201-20, and the third brightness sensor 403-40 is arranged in the green laser 203-20 In the light output path of the green laser 203-20, specifically, it is arranged on the side of the light output path of the collimated beam of the green laser 203-20. Since the laser light emitted by the laser does not attenuate in its light path, the brightness sensor is arranged in the light path of the laser, which improves the accuracy of the brightness sensor for detecting the first brightness value of the laser.

The display control circuit is also used to read the brightness value detected by the first brightness sensor 401-40 when controlling the blue laser 201-20 to emit blue laser light. And when the blue laser 201-20 is controlled to be turned off, stop reading the brightness value detected by the first brightness sensor 401-40.

The display control circuit is also used to read the brightness value detected by the second brightness sensor 402-40 when controlling the red laser 202-20 to emit red laser light, and stop reading the second brightness value when controlling the red laser 202-20 to turn off. The brightness value detected by the brightness sensor 402-40.

The display control circuit is also used to read the luminance value detected by the third luminance sensor 403-40 when controlling the green laser 203-20 to emit green laser light, and stop reading the luminance value detected by the third luminance sensor 403-40 when controlling the green laser 203-20 to be turned off. The brightness values detected by the three brightness sensors 403-40.

It should be noted that there may also be one brightness sensor, which is arranged in the combined light path of the three-color lasers.

FIG. 4 is a schematic structural diagram of a projection device according to another embodiment of the present application.

In some embodiments, the projection device may further include a light pipe 110, which is used as a light-collecting optical component for receiving and homogenizing the output three-color laser light in a combined light state.

In some embodiments, the brightness sensor may include a fourth brightness sensor 404, which may be a white light brightness sensor. Wherein, the fourth brightness sensor 404 is disposed in the light exit path of the light pipe 110 , for example, on the light exit side of the light pipe, close to its light exit surface. And, the above-mentioned fourth brightness sensor is a white light brightness sensor.

The display control circuit is also used to read the luminance value detected by the fourth luminance sensor 404 when controlling the blue laser 201-20, the red laser 202-20 and the green laser 203-20 to turn on time-sharing, so as to ensure that the fourth The brightness sensor 404 can detect the first brightness value of the blue laser 201-20, the first brightness value of the red laser 202-20 and the first brightness value of the green laser 203-20. And when the blue laser 201-20, the red laser 202-20 and the green laser 203-20 are all turned off, stop reading the brightness value detected by the fourth brightness sensor 404.

In some embodiments, the fourth brightness sensor 404 is always on when the projection device is projecting images.

In some embodiments, referring to FIG. 3 or FIG. 4, the projection device may further include a fourth dichroic film 604, a fifth dichroic film 605, a fifth reflector 904, a second lens assembly, a diffusion wheel 150, TIR lens 120, DMD 130 and projection lens 140. Wherein, the second lens assembly includes a first lens 901-90, a second lens 902-90 and a third lens 903-90. The fourth dichroic film 604 can transmit blue laser light and reflect green laser light. The fifth dichroic film 605 can transmit red laser light and reflect green laser light and blue laser light.

The blue laser light emitted by the blue laser 201-20 passes through the fourth dichroic film 604, and then is reflected by the fifth dichroic film 605 and enters the first lens 901-90 for condensing. The red laser light emitted by the red laser 202-20 passes through the fifth dichroic film 605 and directly enters the first lens 901-90 for focusing. The green laser light emitted by the green laser 203-20 is reflected by the fifth reflector 904, reflected by the fourth dichroic film 604 and the fifth dichroic film 605 in turn, and then enters the first lens 901-90 for focusing. After being concentrated by the first lens 901-90, the blue laser, red laser and green laser pass through the rotating diffusion wheel 150 in time-sharing to dissipate the speckle, and project to the light guide 110 for uniform light, and then pass through the second lens 902-90 After shaping with the third lens 903-90, it enters the TIR lens 120 for total reflection, and after being reflected by the DMD 130, passes through the TIR lens 120, and finally is projected onto the display screen through the projection lens 140 to form an image to be displayed.

FIG. 5 is a schematic diagram of a circuit structure of a projection device according to some embodiments of the present application.

In some embodiments, the laser driving component may include a driving circuit 301 , a switching circuit 302 and an amplifying circuit 303 . The driving circuit 301 may be a driving chip. The switch circuit 302 may be a metal-oxide-semiconductor (MOS) transistor.

Wherein, the driving circuit 301 is respectively connected with the switch circuit 302, the amplification circuit 303 and the corresponding laser included in the laser light source. The driving circuit 301 is used to output the driving current to the corresponding laser in the laser light source through the VOUT terminal based on the current control signal sent by the display control circuit 10 , and transmit the received enable signal to the switch circuit 302 through the ENOUT terminal. Wherein, the laser may include n sub-lasers connected in series, which are respectively sub-lasers LD1 to LDn. n is a positive integer greater than 0.

The switch circuit 302 is connected in series in the current path of the laser, and is used to control the conduction of the current path when the received enable signal is at an effective potential.

The amplifying circuit 303 is respectively connected to the detection node E in the current path of the laser light source 20 and the display control circuit 10, and is used to convert the detected driving current of the laser component into a driving voltage, amplify the driving voltage, and convert the amplified driving current The voltage is transmitted to the display control circuit 10 .

The display control circuit 10 is further configured to determine the amplified driving voltage as the driving current of the laser, and obtain a second brightness value corresponding to the driving current.

In some embodiments, the amplifying circuit 303 may include: a first operational amplifier A1, a first resistor (also known as a sampling power resistor) R1, a second resistor R2, a third resistor R3 and a fourth resistor R4.

The non-inverting input terminal (also known as the positive terminal) of the first operational amplifier A1 is connected to one end of the second resistor R2, and the inverting input terminal (also known as the negative terminal) of the first operational amplifier A1 is respectively connected to one terminal of the third resistor R3 and the second resistor R3. One end of the four resistors R4 is connected, and the output end of the first operational amplifier A1 is respectively connected to the other end of the fourth resistor R4 and the processing sub-circuit 3022 . One end of the first resistor R1 is connected to the detection node E, and the other end of the first resistor R1 is connected to the reference power supply end. The other end of the second resistor R2 is connected to the detection node E, and the other end of the third resistor R3 is connected to the reference power supply end. The reference power terminal is a ground terminal.

In some embodiments, the first operational amplifier A1 may further include two power supply terminals, one of which is connected to the power supply terminal VCC, and the other power supply terminal may be connected to the reference power supply terminal.

The large driving current of the laser included in the laser light source passes through the first resistor R1 to generate a voltage drop, and the voltage Vi at one end of the first resistor R1 (that is, the detection node E) is transmitted to the first operational amplifier A1 through the second resistor R2 The non-inverting input terminal is amplified N times by the first operational amplifier A1 and then output. The N is the amplification factor of the first operational amplifier A1, and N is a positive number. The magnification ratio N can make the value of the voltage Vfb output by the first operational amplifier A1 be an integer multiple of the value of the driving current of the laser. For example, the value of the voltage Vfb can be equal to the value of the driving current, so that the display control circuit 10 can determine the amplified driving voltage as the driving current of the laser.

In some embodiments, the display control circuit 10, the drive circuit 301, the switch circuit 302, and the amplifier circuit 303 form a closed loop to realize the feedback adjustment of the driving current of the laser, so that the display control circuit 10 can pass the laser second The difference between the luminance value and the first luminance value adjusts the driving current of the laser in time, that is, adjusts the actual luminance of the laser in time, avoids long-term COD failure of the laser, and improves the accuracy of laser luminescence control.

It should be noted that referring to FIG. 3 and FIG. 4 , if the laser light source includes a blue laser, a red laser and a green laser. The blue laser 201 can be set at the L1 position, the red laser 202 can be set at the L2 position, and the green laser 203 can be set at the L3 position.

Referring to FIG. 3 and FIG. 4 , the laser light at position L1 is transmitted once through the fourth dichroic film 604 , reflected once through the fifth dichroic film 605 , and enters the first lens 901 . The light efficiency P1=Pt×Pf at the L1 position. Wherein, Pt represents the transmittance of the dichroic plate, and Pf represents the reflectance of the dichroic plate or the fifth reflectance.

In some embodiments, among the three positions L1, L2 and L3, the light efficiency of the laser light at the position L3 is the highest, and the light efficiency of the laser light at the position L1 is the lowest. Since the maximum optical power Pb output by the blue laser 201 is 4.5 watts (W), the maximum optical power Pr output by the red laser 202 is 2.5W, and the maximum optical power Pg output by the green laser 203 is 1.5W. That is, the maximum optical power output by the blue laser 201 is the largest, followed by the maximum optical power output by the red laser 202 , and the maximum optical power output by the green laser 203 is the smallest. The green laser 203 is therefore placed at the L3 position, the red laser 202 is placed at the L2 position, and the blue laser 201 is placed at the L1 position. That is, the green laser 203 is arranged in the optical path with the highest light efficiency, so as to ensure that the projection device can obtain the highest light efficiency.

In some embodiments, the display control circuit 10 is further configured to recover the current control signal of the laser driving component corresponding to the laser when the difference between the second brightness value of the laser and the first brightness value of the laser is less than or equal to the difference threshold To the initial value, the initial value is the magnitude of the PWM current control signal to the laser in the normal state. Therefore, when a COD failure occurs in the laser, it can be quickly identified, and measures to reduce the driving current can be taken in time to reduce the continuous damage of the laser itself and help it recover itself. The whole process does not require dismantling and human intervention, which improves the laser light source. The reliability of use ensures the projection display quality of laser projection equipment.

In some embodiments, the controller includes a central processing unit (Central Processing Unit, CPU), a video processor, an audio processor, a graphics processing unit (Graphics Processing Unit, GPU), RAM (Random Access Memory, RAM), ROM (Read -Only Memory, ROM), at least one of the first interface to the nth interface for input/output, a communication bus (Bus), and the like.

In some embodiments, after the projection device is started, it can directly enter the display interface of the signal source selected last time, or the signal source selection interface, wherein the signal source can be a preset video-on-demand program, or an HDMI interface, a live TV interface After the user selects different signal sources, the projector can display the content obtained from different signal sources.

The embodiments of the present application may be applied to various types of projection devices. The projection equipment and the projection image correction method based on optomechanical camera calibration are described below.

In some embodiments, the camera configured by the projection device can be implemented as a 3D camera, or a binocular camera; when the camera is implemented as a binocular camera, it specifically includes a left camera and a right camera; the binocular camera can obtain the corresponding The curtain is the image and playback content presented on the projection surface. The image or playback content is projected by the built-in optical machine of the projection device.

When the projection device moves, its projection angle and the distance to the projection surface change, which will cause the projection image to be deformed, and the projection image will be displayed as a trapezoidal image or other deformed images; the projection device controller can be based on the deep learning neural network, through The correct display of the angle between the projection surface of the coupling optical machine and the projection image realizes automatic trapezoidal correction; however, this correction method is slow in correction speed and requires a large amount of scene data for model training to achieve a certain accuracy, so it is not suitable for user equipment. instant and fast correction of the scene.

In some embodiments, for projected image correction, the relationship between the distance, horizontal angle, and offset angle can be created in advance; then the projection device controller obtains the current distance from the light machine to the projection surface, and combines the associated relationship Determine the angle between the optical machine and the projection surface at this moment, and realize the projection image correction. The included angle is specifically implemented as the included angle between the central axis of the optical machine and the projection surface. In some complex environments, it may happen that the association relationship created in advance cannot adapt to all complex environments, resulting in the failure of projected image correction or the decline in correction progress. .

In some embodiments, the projection device can maximize the advantages of the two dimming methods and weaken the impact caused by their disadvantages by combining their working modes and dynamically switching dimming in the working scene. The projection device can monitor the movement of the device in real time through its configuration components, and immediately feed back the monitoring results to the projection device controller, so that after the projection device moves, the controller immediately starts the image correction function to realize the automatic correction of the projected image in the first time.

For example, through the gyroscope or TOF (Time of Flight) sensor configured by the projection device, the controller receives monitoring data from the gyroscope and TOF sensor to determine whether the projection device moves; after determining that the projection device moves , the controller will start the projection screen automatic correction process and/or obstacle avoidance process, so as to realize functions such as trapezoidal projection area correction and projected obstacle avoidance.

Among them, the time-of-flight sensor realizes distance measurement and position movement monitoring by adjusting the frequency of the transmitted pulse. Its measurement accuracy will not decrease with the increase of the measurement distance, and it has strong anti-interference ability. The laser light emitted by the projection equipment is reflected by the nano-scale lens of the DMD (Digital Micromirror Device: Digital Micromirror Device) chip. The optical lens is also a precision component. When the image plane and the object plane are not parallel, the image projected on the screen will occur. Geometry distortion.

Fig. 6 shows a schematic diagram of a system framework for implementing display control by a projection device according to some embodiments of the present application.

In some embodiments, the projection device has the characteristics of telephoto micro-projection, and its controller can display and control the projected light image through a preset algorithm, so as to realize automatic keystone correction, automatic screen entry, automatic obstacle avoidance, automatic focus, And anti-shooting eyes and other functions.

Through the display control method based on geometric correction, the projection device can realize the flexible position movement in the telephoto micro-projection scene; during each movement of the device, the possible distortion of the projection screen, foreign objects on the projection surface, and abnormality of the projection screen from the screen and other problems, the controller can control the projection device to realize the automatic display correction function, so that it can automatically return to normal display.

In some embodiments, the geometric correction-based display control system includes an application program service layer (APK Service: Android application package Service), a service layer, and an underlying algorithm library.

The application service layer is used to realize the interaction between the projection device and the user; based on the display of the user interface, the user can configure various parameters of the projection device and the display screen, and the controller coordinates and calls the algorithm services corresponding to various functions , which can realize the function of automatically correcting the display screen of the projection device when the display is abnormal.

The service layer can include correction services, camera services, time-of-flight (TOF) services, etc., and the services correspond to the application program service layer (APK Service) to realize the corresponding specific functions of different configuration services of the projection device; the service layer is connected downwards Algorithm libraries, cameras, time-of-flight sensors and other data acquisition services realize the functions of encapsulating the underlying complex logic and transmitting business data to the corresponding service layer.

The underlying algorithm library provides correction services and control algorithms for projection equipment to achieve various functions. The algorithm library can complete various mathematical operations based on OpenCV (based on licensed open source) to provide basic computing capabilities for correction services; OpenCV is a cross- Platform computer vision, machine learning software library, can run in a variety of existing operating system environments.

In some embodiments, the projection device is configured with a gyroscope sensor; during the movement of the device, the gyroscope sensor can sense the position movement and actively collect movement data; then the collected data is sent to the application service layer through the system framework layer, It supports user interface interaction and application data required in the process of application program interaction, and the collected data can also be used for data calls by the controller in the implementation of algorithm services.

In some embodiments, the projection device is configured with a time-of-flight (TOF) sensor. After the time-of-flight sensor collects corresponding data, the data will be sent to the time-of-flight service corresponding to the service layer; after the above-mentioned time-of-flight service obtains the data, The collected data is sent to the application program service layer through the process communication framework, and the data will be used for interactive use of the controller's data call, user interface, program application, etc.

In some embodiments, the projection device is configured with a camera for collecting images, and the camera can be implemented as a binocular camera, or a depth camera, or a 3D camera, etc.; the data collected by the camera will be sent to the camera service, and then the camera service will collect The image data is sent to the process communication framework and/or the projection device correction service; the projection device correction service can receive the camera acquisition data sent by the camera service, and the controller can call the corresponding control in the algorithm library for different functions to be realized algorithm.

In some embodiments, data interaction is performed with the application service through the process communication framework, and then the calculation result is fed back to the correction service through the process communication framework; the correction service sends the obtained calculation result to the operating system of the projection device to generate a control signal command, and send the control signal to the optical-mechanical control driver to control the optical-mechanical working conditions and realize the automatic correction of the displayed image.

In some embodiments, the projection device can project a picture of a target size, and the target size is related to factors such as the optical machine and the location of the projection device;

For example, the projection equipment can project a screen of 75-100 inches; after the user purchases the projection equipment, after the projection installation and debugging, the projection equipment in position A can obtain a suitable projection area, which is rectangular and usually can be completely , accurately cover the corresponding rectangular screen, as shown on the left side of Figure 7A; when the projection device moves from position A to position B, it often generates a deformed projection image, as shown on the right side of Figure 7A; due to cleaning, moving, etc. The reason is that the position of the projection equipment changes, and when the projection screen is fixed, the position and shape of the projected image will change, resulting in the problem that the projected image does not match the rectangular screen.

Therefore, when the position of the projection device changes, the user needs to adjust the projection device in time to return it to its original position, so as to adjust the relative position of the projected image and the rectangular screen, so that the projected image matches the rectangular screen; For ordinary users with device function settings, usually after adjusting the position, the projected image still appears deformed and cannot enter the screen;

Through the projection device provided by this application and the projection image correction method based on optical-mechanical camera calibration, software-based correction can be realized without the need for the user to manually adjust the position of the projection device, as shown in Figure 7F. The correction of the deformed projection image will be explained below .

FIG. 7B shows a schematic diagram of the relative positions of the projection device and the calibration plate according to another embodiment of the present application.

After the projection image correction service is started, the user interface of the projection device will prompt the user to obtain the calibration parameters, which include the internal parameters of the optical machine and the external parameters between the optical machine and the camera; the user needs to place the calibration plate on the surface of the rectangular screen, and pass the on-site calibration The method can solve the problem of excessive error between the actual value of the above parameters and the theoretical value. Among them, the theoretical value of the calibration parameter refers to the equipment parameter that has been marked on the equipment shell or the manual when the projection equipment is manufactured. The theoretical value is usually determined based on the function, assembly, manufacture, and parts of the projection equipment, and is applicable to the same model All projection equipment products; the actual value of the calibration parameters is the actual value measured and obtained on-site through the calibration scheme provided by the embodiment of the application. For different projection equipment products of the same model, the actual value may have slight differences.

In some embodiments, the projection device can be used in cooperation with the calibration plate to realize the determination of the calibration parameters. The calibration plate can be arranged in the center of the rectangular screen, and the calibration plate includes two parts, namely the calibration card on the right and the blank area on the left, as shown in FIG. 7B .

The blank area on the left is mainly used to display the projection image generated by the optical-mechanical projection calibration chart, so that the calibration parameters can be determined by using the coplanar characteristics of the projection image and the inherent calibration chart on the right side of the calibration plate to obtain accurate optical-mechanical internal parameters, The extrinsic parameters between the opto-mechanical camera and the optical-mechanical camera will be described in detail below to determine the calibration parameters.

In the process of determining the calibration parameters, firstly, the calibration board is set in the center of the rectangular curtain, and the inherent calibration chart on the right side of the calibration board can be implemented as a black and white checkerboard;

Then control the optical machine to project the same checkerboard image to the blank area on the left side of the calibration board, and control the camera to obtain the calibration board image at this moment. It can be found that the calibration board image can display the checkerboard projection image of the blank area and the right side An inherent checkerboard image, as shown in Figure 7C;

It should be noted that, in some embodiments, the calibration chart of the optical machine projection and the calibration chart inherent in the calibration plate can also be implemented as a circular pattern, as shown in Figure 7G; the feature points included in the checkerboard calibration chart are The corner points of the rectangle and the feature points contained in the ring calibration chart are the corresponding solid points on each ring. It should be noted that, in addition to the left and right arrangement shown in the accompanying drawings, the layout of the blank area and the calibration chart card in the calibration board can also be arranged such as up and down, diagonal arrangement, etc., so The layout sequence of the blank area and the calibration chart in the calibration board can be exchanged; in some embodiments, the calibration chart can also be implemented as a combination of the above two types of patterns, or the calibration chart can also be implemented as other features that can Identify the pattern of feature points.

In some embodiments, for a calibration card implemented as a checkerboard grid, the controller extracts the corner point of the inherent checkerboard grid on the right side of the calibration board image, and obtains the pixel coordinates of the corner point in the camera coordinate system; then creates a world coordinate system, The world coordinate system takes the plane of the calibration board as the XOY plane, and sets the corner point of the first rectangle of the right inherent checkerboard as the origin, and the Z axis of the world coordinate system is perpendicular to the plane of the calibration board.

Control the camera to shoot the image of the calibration plate, and extract the corresponding relationship between the checkerboard corners in the projected image and the inherent checkerboard corners in the world coordinate system under the camera coordinate system, and obtain the camera internal parameter A and the external parameter between the optical machine and the camera. , the external parameters include a rotation matrix R[i] and a translation matrix t[i], and the feature points in the calibration plate image are shown in FIG. 7D .

It should be noted that the feature points are marked in the drawings; however, when the projection device actually projects the calibration chart card to the calibration board, the calibration board may not actually display the feature points.

In some embodiments, in order to improve the accuracy of the determined calibration parameters, the controller may control the camera to capture a preset number of calibration plate images, and identify and extract feature points in the calibration plate images based on each image.

For example, the calibration board implemented as a checkerboard calibration chart is rotated counterclockwise to obtain different photographing poses, as shown in Figure 7E; then, in the acquired calibration board image, the corner coordinates of the projected image under the camera coordinate system are identified, That is, based on multiple calibration plate images acquired by the camera, the corner coordinates of the checkerboard projection image in the blank area under the camera coordinate system are respectively identified. Wherein, when the preset number is 25, the camera is set to take 25 images of the calibration plate in total, 5 pictures are taken continuously when the calibration plate is at the starting position, and 5 pictures are continuously taken after every counterclockwise rotation of 15 degrees , until the camera acquires 25 pictures.

Since the projected image projected by the optical machine is on the projection surface, and the calibration plate is also arranged on the projection surface, the projected image is coplanar with the inherent checkerboard of the calibration plate, so the corner points of the checkerboard projected by the optical machine are in the same plane as the inherent checkerboard of the calibration plate. Each corner point is in the same world coordinate system, so the conversion relationship from the world coordinate system to the camera coordinate system is the same, that is, the internal parameter A and external parameters R[i] and t[i] of the camera are the same under different postures of the calibration board. By creating a world coordinate system, the calibration parameters can be determined based on the corresponding relationship between the corner points in the projected image and the corner points in the inherent calibration chart of the calibration plate in the world coordinate system.

For example, the controller extracts the camera to obtain the corner points of the checkerboard projection image in the calibration plate image, and the corner points are feature points; then use the corner points of each image's inherent checkerboard to solve the camera internal parameters and external parameters; The corner points of the checkerboard in are converted from the camera coordinate system to the world coordinate system, so that the world coordinates of all feature points on the projection surface are obtained.

Assume that in the calibration plate image acquired by the camera, the corners of the checkerboard projection image are expressed as m′(u, v) in the camera coordinate system, according to the camera internal parameter A obtained in the above steps, and the external parameter rotation matrix R[i] and The coordinates of the checkerboard projection image in the world coordinate system can be obtained by translating the matrix t[i], expressed as M′(X,Y,Z);

Through the following formula, the world coordinate M' of the checkerboard projection image corner point in the projection plane can be obtained under each attitude of the calibration board, and the formula (1) is expressed as follows:

s·m′＝A·[R|t]·M′ (1)

Or expressed as formula (2):

Among them, the matrix

Indicates the internal reference A, the matrix

Indicates the external parameter [R|t];

In some embodiments, the optomechanical DMD (digital micromirror device plane) plane can be regarded as the camera imaging plane, and at this moment, the world coordinates of the calibration map feature points in the projection plane under each calibration plate posture can be obtained through the above steps, The above-mentioned camera calibration algorithm can be used to calibrate the internal parameters of the optical machine; it can be found that the optical machine projection process can be understood as the reverse process of image acquisition by the camera, so the optical machine can be calibrated according to the camera calibration method.

In some embodiments, in order to project obliquely upward when the projection device is placed on the table, or obliquely downward when the projection device is hoisted on the ceiling, the optical machine DMD plane will move down or up. At this time, the center of the DMD plane will be far away from the axis of the lens. In order to keep the center of the DMD plane on the axis of the lens, the DMD imaging plane can be virtualized during the calibration process.

For example, the size of the original DMD plane is 1920*1080 pixels. In order to increase the optical-mechanical projection angle, it is necessary to control the DMD plane to move down the first distance. Assuming that the DMD plane is moved down by 1080 pixels, the moving diagram of the DMD plane and the imaging plane is shown in the figure 8A.

In order to keep the center of the DMD imaging surface at the lens axis, the first distance is correspondingly extended above the imaging surface, such as filling 1920*1080 solid color pixels, the filled part can actually be supplemented with black or white, and the original DMD at this moment The imaging surface will be changed to the DMD imaging surface of 1920*2160.

Therefore, when calibrating the optical machine, the DMD imaging surface will be calibrated according to the 1920*2160 pixel area. At this time, the pixel coordinates of the calibration chart feature points on the DMD imaging surface will change, and the ordinate of the feature points will increase by 1080 pixels from the original value, as shown in Figure 8B As shown; in the original calibrated imaging surface, the width of the imaging surface is 1920 pixels, and the height is 1080 pixels; after expansion, the width value remains unchanged, and the high value is extended to 2160 pixels, that is, the size of the expanded imaging surface is changed to 1920*2160 pixel area.

In some embodiments, the projection device is suspended on the ceiling, and when the optical machine needs to project obliquely downward, the DMD plane will translate upward. For example, the DMD plane is a 1920*1080 pixel area. After the DMD plane is shifted upward by 1080 pixels, it can be considered that the 1080 rows of pixels below the DMD imaging surface are all pure colors. During calibration, the size of the DMD imaging surface is considered to be 1920*2160. The coordinate values of the projected calibration chart feature points on the DMD imaging plane remain unchanged.

In the same way, based on the above steps, the optical-mechanical calibration of the DMD plane translation when the projection optical machine is projected to the left and right can be realized; based on the above-mentioned optical-mechanical calibration method, the optical-mechanical internal reference of any DMD plane can be translated to any direction in any direction, and Calibration of extrinsic parameters between optomechanical cameras.

For example, when the center of the DMD plane of the optical machine is on the lens axis, if the optical machine is placed on the ground, it will not be possible to obtain a complete projected image when projected onto the wall. Move up to avoid the problem that the projection device cannot obtain a complete projection image on the wall when the projection device is placed on the level ground, desktop and other scenes; The principle of imaging is to reversely calibrate the imaging surface of the optical machine and expand the corresponding first distance, so that when the plane of the digital micromirror device is translated by any distance in any direction, the projection device can still accurately obtain the calibration parameters to ensure the accuracy of image correction.

Based on the pixel coordinates of the feature points of the DMD imaging surface in the camera coordinate system, the coordinates of the feature points of the projection surface in the world coordinate system, and the coordinates of the feature points of the camera imaging surface, a binocular system is formed, which can realize the calibration of external parameters between optical machines and cameras. For example, after the display image correction service of the projection device is started, in the step of determining the calibration parameters, control the optical machine to project the calibration chart to the rectangular screen, and the calibration service will notify the algorithm service to start the optical machine camera calibration process;

The algorithm service calls the camera to take pictures, obtains a preset number of calibration plate photos and stores them; when it is determined that the stored photos have reached the preset number, it will return the correction service to take pictures successfully; if it is determined that the stored photos do not reach the preset number When the quantity is exceeded, it prompts to take another photo;

The calibration map card is implemented as a checkerboard. After the camera successfully obtains the calibration board image, the controller will call the optical-mechanical camera calibration algorithm to determine the calibration parameters; first, identify and extract the inherent checkerboard corners in the preset number of calibration board images; if not Identify and extract the inherent checkerboard corners of the calibration board image in the calibration board image, return the corner point extraction failure information and prompt to re-shoot; Checkerboard projection image corner recognition and extraction steps; if the corner points of the projected image in the calibration plate image cannot be identified and extracted, the corner point extraction failure re-shooting information will be returned; if all the projection image corner points in the calibration plate image are successfully extracted, enter the light The calculation steps of the extrinsic parameters between the optomechanical camera and the intra-machine, as shown in Figure 9A, include:

Step 901, start the calibration service;

Step 902, controlling the optical-mechanical projection calibration chart;

Step 903, adjusting the camera to take a preset number of pictures;

Step 904, judging whether the picture reaches the preset number, if not, go to step 905, otherwise go to step 906;

Step 905, prompting that the shooting failed, and re-shooting;

The feature points of the calibration plate image include the feature points of the projected image in the blank area of the calibration plate, and the feature points of the calibration card itself set by the calibration plate; In case of failure, the projection device re-executes the step of determining the calibration parameters.

Step 906, prompting that the photo is taken successfully, and extracting the checkerboard corner points of the calibration board in the preset number of pictures;

Step 907, judging whether the checkerboard corner points are extracted, if not, go to step 908, otherwise go to step 909;

Step 908, prompting that the extraction of checkerboard corner points failed, and taking a new photo;

Step 909, prompting that the corner points of the checkerboard are extracted successfully, and extracting the projected image feature points in the preset number of pictures;

Step 910, whether the projected image feature points are extracted, if not, execute step 911, otherwise execute step 912;

Step 911, prompting that the feature point extraction of the projected image failed, please take a photo again;

Step 912, prompting that the feature points of the projected image are successfully extracted, and calculating the optical-mechanical internal parameters and optical-mechanical external parameters;

Step 913, whether the difference between the calibration parameter and the theoretical value is within the threshold range, if so, the calibration is successful, otherwise, go to step 914;

Step 914, please check whether the quality of the photo and its structure are abnormal.

In some embodiments, in order to reduce the error of the calibration parameter, when the difference between the acquired calibration parameter and the preset theoretical value is less than or equal to the preset threshold, it can be determined that the calibration parameter has been successfully acquired; otherwise, re-execute the calibration parameter determination step, such as Figure 9A shows a schematic diagram of calibration parameters.

For example, verify the optical-mechanical internal parameters and optical-mechanical-camera external parameters obtained in the above-mentioned steps; If it is within the threshold range, it will return the calibration service calibration success information; if the difference exceeds the threshold range, it will prompt to check the quality of the photo, and prompt whether the projection device structure is damaged, and return the calibration service calibration failure information. Its user interface is shown in Figure 9B. .

In some embodiments, when the controller detects that the projection device moves, or detects a deformed projected image, the controller will start the projected image correction service.

First, control the optical machine to project the calibration chart to the rectangular screen, and then control the binocular camera to shoot the projection image of the calibration chart; based on the binocular camera, the coordinates of the calibration chart feature points in the projected image in the camera coordinate system can be obtained, indicating is P(x, y, z); then use the calibration parameters obtained in the above steps to calculate the coordinates of the feature points in the optical-mechanical coordinate system;

Calibration parameters can be expressed as formula (3), formula (4), and formula (5) in some specific embodiments:

Among them, mr is the internal reference matrix of the optical machine (3*3), RRR is the rotation matrix between the optical machine and the camera, and TTT is the translation matrix between the optical machine and the camera;

Based on the calibration parameters obtained in the above embodiments and the coordinates of the calibration plate image obtained by the control camera in the camera coordinate system, the conversion matrix between the world coordinate system and the optical-mechanical coordinate system can be determined.

The coordinates of the feature points on the projection surface in the optical-mechanical coordinate system can be expressed as formula (6):

P′(x′,y′,z′)=RRR*P+TTT (6)

According to the calibration parameters, the controller can convert the feature points of the calibration board image from the camera coordinate system to the optical-mechanical coordinate system.

Based on the coplanar characteristics of the projection surface and the calibration plate, all the feature points of the calibration plate image in the optical-mechanical coordinate system are fitted to obtain the unit normal vector of the projection surface in the optical-mechanical coordinate system;

First, according to the coordinates of all feature points on the projection surface in the optical-machine coordinate system, the projection surface equation in the optical-machine coordinate system can be fitted, expressed as formula (7):

z=ax+by+c (7);

or formula (8)

Then, the unit normal vector of the projected surface in the optical machine coordinate system can be expressed as formula (9):

The origin of the created world coordinate system is at the origin of the optical machine coordinate system, the XOY plane is parallel to the projection surface, and the Z axis is perpendicular to the projection surface. Therefore, in the world coordinate system, the unit normal vector of the projection surface can be expressed as formula (10 ):

m=(0,0,1)*T (10);

According to the representation of the unit normal vector of the projection surface in different coordinate systems, the rotation matrix R1 between the optical machine coordinate system and the world coordinate system can be obtained, and the relationship between them is expressed as formula (11):

m=R1*n (11);

In some embodiments, the controller converts the first coordinates of the rectangular vertices of the preset projection area in the world coordinate system to the second coordinates in the optical-mechanical coordinate system based on the conversion matrix obtained above, so as to realize the correction The actual position coordinate value required by the optomechanical projection can also be understood as the correction of the deformed projected image after the optomechanical projection plays the content to the second coordinate.

For example, in the world coordinate system, the four vertices of the rectangular curtain are shown in Figure 7A, which are expressed as:

A(x ₁ ,y ₁ ,z), B(x ₂ ,y ₂ ,z), C(x ₃ ,y ₃ ,z), D(x ₄ ,y ₄ ,z);

Based on the rotation matrix between the optical-mechanical coordinate system and the world coordinate system, the four vertices of the above-mentioned rectangular curtain can be transformed into the optical-mechanical coordinate system, where the optical-mechanical system can be regarded as the inverse system of the camera system, and the optical-mechanical required The coordinates of the vertices of the projected rectangular area, such as the coordinate A′ of point A in the optical-mechanical coordinate system, can be expressed as formula (12):

(A') ^T = mr*R ₁ *A ^T (12);

Similarly, according to the above method, the corresponding coordinates B′, C′, D′ of the other three vertices B, C, and D of the rectangular curtain can be obtained when they are transformed into the optical-mechanical coordinate system. After the projection device projects the deformed image, it can display the image The correction function again controls the optical machine to project the playback content to the preset projection area of the projection surface to complete the projection image correction, as shown in FIG. 7F .

Based on the above introduction of the projected image correction scheme based on optical-mechanical camera calibration by projection equipment and the introduction of related drawings, this application also provides a projection image correction method based on optical-mechanical camera calibration. The projection image correction scheme for machine camera calibration has been elaborated in detail, and will not be repeated here.

The beneficial effect of the embodiment of the present application is that by projecting the calibration chart to the calibration plate, the actual value of the calibration parameters can be obtained; further by constructing the conversion matrix, the preset projection area in the world coordinate system can be converted to the optical-mechanical coordinate system ; Further, by projecting the playback content to the second coordinate, the position correction of the projected image can be realized, the accuracy of the calibration parameters can be improved, and the correction effect of the projected image can be enhanced.

FIG. 10 is a schematic diagram of a signaling interaction sequence for realizing the anti-eye function of a projection device according to another embodiment of the present application.

In some embodiments, the projection device can implement the anti-eye function to prevent the risk of visual impairment caused by the user accidentally entering the range of the laser trajectory emitted by the projection device. When the user enters the preset specific non-safety area where the projection device is located, the controller The user interface can be controlled to display corresponding prompt information to remind the user to leave the current area, and the controller can also control the user interface to reduce the display brightness to prevent the laser from causing damage to the user's eyesight.

As shown in Figure 10, it includes step 1001, triggering policy control: when the projection device is configured as a children's viewing mode, the controller will automatically turn on the anti-eye switch; when receiving the position movement data sent by the gyroscope sensor, or receiving other sensor After the foreign object intrusion data is collected, the controller will control the projection device to turn on the anti-eye switch; when the data collected by the time-of-flight (TOF) sensor and camera trigger any preset threshold condition, the controller will control the user interface to reduce the display brightness , Display prompt information, reduce optical machine transmission power, brightness, intensity.

Step 1002, the calibration service sends signaling to the time-of-flight sensor to inquire about the current state of the projection device, and the controller will receive data feedback from the time-of-flight sensor;

Step 1003, the correction service sends a notification algorithm service to the process communication framework to start the anti-eye shot process signaling;

Step 1004, the process communication framework will call the service capability from the algorithm library to call the corresponding algorithm service, and the algorithm may include a camera detection algorithm, a screenshot algorithm, and a foreign object detection algorithm, etc.;

Step 1005, the process communication framework can return the foreign object detection result to the correction service based on the above algorithm service;

Step 1006, if the returned result reaches the preset threshold condition, the controller will control the user interface to display prompt information and reduce the display brightness.

In some embodiments, when the anti-radiation eye is in the open state, when the user enters a preset specific area, the projection device will automatically reduce the intensity of the laser emitted by the optical machine, reduce the display brightness of the user interface, and display safety prompt information; The control of eye function can be realized by the following methods, as shown in Figure 15:

Based on the projection image acquired by the camera, an edge detection algorithm is used to identify the projection area of the projection device; when the projection area is displayed as a rectangle or a rectangle, the controller obtains the coordinate values of the four vertices of the above-mentioned rectangular projection area through a preset algorithm;

When realizing the detection of foreign objects in the projection area, the perspective transformation method can be used to correct the projection area to a rectangle, and the difference between the rectangle and the projection screenshot can be calculated to realize whether there is a foreign object in the display area; if the judgment result is that there is a foreign object, the projection The device automatically activates anti-eye.

When realizing foreign object detection in a certain area outside the projection range, the camera content of the current frame and the camera content of the previous frame can be compared to determine whether there is a foreign object entering the area outside the projection range; if it is judged that a foreign object has entered, the Trigger the activation of the anti-eye function.

Step 1501, turn on anti-shooting eyes;

The projection device can also use a time-of-flight (ToF) camera or a time-of-flight sensor to detect real-time depth changes in a specific area; if the depth value changes beyond a preset threshold, the projection device will automatically trigger the anti-eye function.

In some embodiments, the projection device judges whether to enable the anti-eye function based on the collected time-of-flight data, screenshot data, and camera data analysis.

For example, in step 1502, the collected time-of-flight data is obtained; in step 1503, the controller performs depth difference analysis; in step 1504, if the depth difference is greater than the preset threshold X, and the preset threshold X is implemented as 0, then it can be determined There is a foreign object in a specific area of the projection device; step 1505, the screen becomes dark, and a prompt pops up;

If the user is located in a specific area and his vision is at risk of being damaged by the laser, the projection device will automatically activate the anti-eye function to reduce the intensity of the laser light emitted by the light machine, reduce the brightness of the user interface display, and display safety reminders.

For another example, step 1506, collect screenshot data; step 1507, analyze the difference of the color additive mode (RGB); the step judges whether it is greater than the threshold value Y; when the difference value is greater than the preset threshold value Y, it can be determined that there is a foreign object in the specific area; step 1505, the screen is darkened, and a prompt pops up; if there is a user in the specific area, whose vision is at risk of being damaged by the laser, the projection device will automatically activate the anti-eye function.

For another example, step 1509, collect camera data; step 1510, obtain projection coordinates; step 1511, determine the target projection area of the projection device; step 1507, perform difference analysis of additive color mode (RGB) in the projection area; step 1508, If the color addition mode difference is greater than the preset threshold Y, it can be determined that there is a foreign object in a specific area of the projection device; step 1505, the screen becomes dark, and a prompt pops up; if there is a user in the specific area, his vision is detected by the laser If there is a risk of damage, the projection device will automatically activate the anti-eye function, reduce the intensity of the emitted laser light, reduce the brightness of the user interface display, and display the corresponding safety prompt information.

Step 1512, the acquired projection coordinates are in the extended area; Step 1513, the controller can still perform the difference analysis of the additive color mode (RGB) in the extended area; Step 1514, judge whether it is greater than the threshold Y, if the difference is greater than the preset Threshold Y, it can be determined that there is a foreign object in a specific area of the projection device; step 1505, the screen becomes dark, and a prompt pops up; the projection device will automatically activate the anti-eye function, as shown in Figure 15 .

Fig. 11 shows a schematic diagram of the signaling interaction sequence of the projection device in another embodiment of the present application to realize the display screen correction function, mainly including:

Step 1101, the projection device monitors the movement of the device through the gyroscope. The calibration service sends a signaling to the gyroscope to query the status of the device, and receives the signaling fed back by the gyroscope to determine whether the device is moving.

The display correction strategy can be configured as follows: when the gyroscope and the time-of-flight sensor change at the same time, the projection device will trigger the keystone correction first; when the keystone correction is in progress, the controller will not respond to the commands sent by the remote control buttons to cooperate with the keystone correction. The projection device will display a pure white image card.

Among them, the trapezoidal correction algorithm can construct the conversion matrix between the projection surface in the world coordinate system and the optical-mechanical coordinate system based on the binocular camera, and combine the optical-mechanical internal parameters to calculate the homography relationship between the projected image and the playing card, and the homography relationship It is also called a mapping relationship, and the homography relationship is used to realize arbitrary shape conversion between the projected image and the playing card, as shown in Figure 11.

Step 1102, the correction service sends a signaling for notifying the algorithm service to start the trapezoidal correction process to the process communication framework, and the process communication framework further sends a service capability call signaling to the algorithm service to obtain the algorithm corresponding to the capability;

Step 1103, the algorithm service obtains and executes the photo taking and picture algorithm processing service, and the obstacle avoidance algorithm service, and sends them to the process communication framework through signaling;

Step 1104, the process communication framework executes the above algorithm, and feeds back the execution result to the calibration service. The execution result may include feedback information such as successful photographing and successful obstacle avoidance.

Step 1105, if an error occurs during the projection device executing the above algorithm or data transmission, the correction service will control the user interface to display an error and return a prompt;

Step 1106, control the user interface to perform keystone correction and auto-focus image card again. Through the automatic obstacle avoidance algorithm, the projection device can identify the screen; and use the projection change to correct the projection image to be displayed inside the screen, so as to achieve the effect of aligning with the edge of the screen. Through the automatic focus algorithm, the projection device can use the time-of-flight (ToF) sensor to obtain Based on the distance between the optical machine and the projection surface, the optimal image distance is found in the preset mapping table, and the image algorithm is used to evaluate the clarity of the projection screen, and the image distance can be fine-tuned based on this.

Step 1107, the automatic keystone correction signaling sent by the correction service to the process communication framework may include other function configuration instructions, such as whether to implement synchronous obstacle avoidance, whether to enter the curtain and other control instructions.

Step 1108, the process communication framework sends the service capability call signaling to the algorithm service;

Step 1109, the algorithm service acquires and executes the auto-focus algorithm to adjust the viewing distance between the device and the screen;

Step 1110, after applying the auto-focus algorithm to implement the function, the algorithm service can also obtain and execute the automatic screen entry algorithm, which may include the keystone correction algorithm.

Step 1111, the projection device performs automatic screen entry;

Step 1112, the algorithm service sets the 8 position coordinates between the projection device and the screen;

In step 1113, adjust the viewing distance between the projection device and the screen through the auto-focus algorithm again;

Step 1114, feedback the correction result to the correction service;

Step 1115, control the user interface to display the calibration result, as shown in FIG. 11 .

In some embodiments, the projection device uses an autofocus algorithm to obtain the current object distance by using its configured laser ranging to calculate the initial focal length and search range; then the projection device drives the camera (Camera) to take pictures, and uses the corresponding algorithm Perform clarity evaluation.

Within the above search range, the projection device searches for the best possible focal length based on the search algorithm, then repeats the above steps of photographing and sharpness evaluation, and finally finds the optimal focal length through sharpness comparison to complete autofocus.

For example, as shown in Figure 12, in step 1201, the projection device starts; in step 1202, the user moves the device, and the projection device automatically completes calibration and refocuses; in step 1203, the controller will detect whether the auto focus function is enabled; when the auto focus function is not enabled , the controller will end the auto-focus service; step 1204, when the auto-focus function is turned on, the projection device will obtain the detection distance of the time-of-flight (TOF) sensor through the middleware for calculation;

Step 1205, the controller queries the preset mapping table according to the obtained distance to obtain the approximate focal length of the projection device; step 1206, the middleware sets the obtained focal length to the optical engine of the projection device;

Step 1207, after the optical machine emits laser light with the above focal length, the camera will execute the photographing instruction; Step 1208, the controller judges whether the projection device is focused according to the obtained photographing result and evaluation function; if the judgment result meets the preset completion conditions, then The process of controlling the autofocus ends; step 1209, if the determination result does not meet the preset completion conditions, the middleware will fine-tune the focal length parameters of the projection device optical machine, for example, the preset step length can be used to gradually fine-tune the focal length, and the adjusted focal length parameters can be set again to Optics and mechanics; so as to realize the steps of repeated photographing and sharpness evaluation, and finally find the optimal focal length through sharpness comparison to complete autofocus.

In some embodiments, the projection device provided by the present application can implement a display correction function through a keystone correction algorithm.

First, based on the calibration algorithm, two sets of external parameters between the two cameras and between the camera and the optical machine can be obtained, that is, the rotation and translation matrices; then the specific checkerboard chart is played through the optical machine of the projection device, and the projected checkerboard angle is calculated Point depth value, for example, solve the xyz coordinate value through the translation relationship between binocular cameras and the principle of similar triangles; then fit the projection surface based on the xyz, and obtain the rotation relationship and translation relationship with the camera coordinate system , which can specifically include pitch relationship (Pitch) and yaw relationship (Yaw).

The Roll parameter value can be obtained through the gyroscope configured by the projection device to combine the complete rotation matrix, and finally calculate the external parameters from the projection plane to the optical-mechanical coordinate system in the world coordinate system.

Combining the R and T values of the camera and optical machine calculated in the above steps, the conversion relationship between the world coordinate system of the projection surface and the optical machine coordinate system can be obtained; combined with the internal parameters of the optical machine, the points on the projection surface can be formed to the optical machine chart. The homography matrix for the points.

Finally, select a rectangle on the projection surface, and use the coordinates corresponding to the homography reflective optical machine chart, which are the correction coordinates, and set them to the optical machine to achieve trapezoidal correction.

For example, the process is shown in Figure 13:

Step 1301, the projection device controller obtains the depth value of the point corresponding to the pixel point of the photo, or the coordinates of the projection point in the camera coordinate system;

Step 1302, through the depth value, the middleware obtains the relationship between the optical machine coordinate system and the camera coordinate system;

Then step 1303, the controller calculates the coordinate value of the projection point in the optical-mechanical coordinate system; step 1304, obtains the angle between the projection surface and the optical-mechanical plane based on the coordinate value fitting plane;

Then step 1305, obtain the corresponding coordinates of the projection point in the world coordinate system of the projection surface according to the angle relationship;

Step 1306, according to the coordinates of the map card in the optical-mechanical coordinate system and the coordinates of the corresponding points on the projection surface of the projection plane, a homography matrix can be calculated.

Step 1307, the controller determines whether an obstacle exists based on the above acquired data;

Step 1308, when obstacles exist, randomly select rectangular coordinates on the projection surface in the world coordinate system, and calculate the area to be projected by the optical machine according to the homography relationship;

Step 1309, when the obstacle does not exist, the controller can obtain the feature points of the two-dimensional code, for example;

Step 1310, obtaining the coordinates of the two-dimensional code on the prefabricated map card;

Step 1311, obtaining the homography relationship between the camera photo and the drawing card;

Step 1312, transforming the acquired coordinates of the obstacle into the chart, so as to obtain the coordinates of the chart that is blocked by the obstacle.

Step 1313, according to the coordinates of the occlusion area of the obstacle map in the optical-mechanical coordinate system, the coordinates of the occlusion area of the projection surface are obtained through homography matrix transformation;

Step 1314, randomly select rectangular coordinates on the projection surface in the world coordinate system, avoid obstacles at the same time, and calculate the area to be projected by the optical machine according to the homography relationship.

It can be understood that the obstacle avoidance algorithm uses the algorithm (OpenCV) library to complete the contour extraction of foreign objects when selecting the rectangle step in the trapezoidal correction algorithm process, and avoids the obstacle when selecting the rectangle to realize the projection obstacle avoidance function.

In some embodiments, as shown in Figure 14:

Step 1401, the middleware obtains the QR code image card captured by the camera;

And step 1402, identify the feature points of the two-dimensional code, and obtain the coordinates under the camera coordinate system;

Step 1403, the controller further acquires the coordinates of the preset image card in the optical-mechanical coordinate system;

Step 1404, solving the homography relationship between the camera plane and the optical-mechanical plane;

Step 1405, the controller identifies the coordinates of the four vertices of the curtain captured by the camera based on the above homography;

Step 1406, according to the homography matrix, obtain the range of the chart to be projected to the screen light machine.

It can be understood that, in some embodiments, the screen entry algorithm is based on the algorithm library (OpenCV), which can identify and extract the largest black closed rectangle outline, and judge whether it is a 16:9 size; project a specific picture card and use a camera to take photos, and extract more details in the photos. The corner points are used to calculate the homography between the projection surface (curtain) and the optical-mechanical display card, and the four vertices of the screen are converted to the optical-mechanical pixel coordinate system through homography, and the optical-mechanical graphic card is converted to the four vertices of the screen. Complete calculation comparison.

The telephoto micro-projection TV has the characteristics of flexible movement, and the projection screen may be distorted after each displacement. In addition, if there is a foreign object on the projection surface, or the projection screen is abnormal from the screen, the projection equipment provided by this application and the geometric correction-based The display control method can automatically complete the correction for the above problems, including the realization of functions such as automatic keystone correction, automatic screen entry, automatic obstacle avoidance, automatic focus, and anti-eye.

For convenience of explanation, the above description has been made in conjunction with specific implementation manners. However, the above discussion of some embodiments is not intended to be exhaustive or to limit implementations to the specific forms disclosed above. Many modifications and variations are possible in light of the above teachings. The selection and description of the above embodiments are for better explaining the content of the present disclosure, so that those skilled in the art can use the embodiments better.

Claims

A projection device comprising:

Optical machine, used to project the playback content to the preset projection area of the projection surface;

The camera is used to acquire the image of the calibration board, the calibration board includes a calibration card and a blank area, and the calibration board is set on the projection screen;

Controller, configured as:

After detecting the movement of the projection device, control the optical machine to project the calibration chart card to the blank area of the calibration plate to determine the calibration parameters;

Based on the calibration parameters and the coordinates of the calibration plate image acquired by the camera in the camera coordinate system, determine a transformation matrix between the world coordinate system and the optical-mechanical coordinate system;

According to the above conversion matrix, the first coordinate of the vertex of the preset projection area in the world coordinate system is converted to the optical machine coordinate system to obtain the second coordinate, and the optical machine is controlled to project and play content to the second coordinate system. coordinate.
The projection device according to claim 1, wherein the controller is further configured to, in the step of determining the calibration parameters when projecting the calibration chart card to the blank area of the calibration board:

Control the camera to take a preset number of calibration plate images, and identify and extract the feature points in the calibration plate images, the feature points include the feature points of the projected image in the blank area, and the calibration chart set by the calibration plate itself Feature points;

When the difference between the obtained calibration parameter and the preset theoretical value is less than or equal to the preset threshold, it is determined that the calibration parameter has been successfully obtained; otherwise, the step of determining the calibration parameter is re-executed;

Wherein, when it is determined that the number of acquired images of the calibration plate is less than the preset number, or the identification and extraction of the feature points fails, the step of determining the calibration parameters is re-executed.
The projection device according to claim 1, wherein the controller is further configured to, in the step of determining the calibration parameters when projecting the calibration chart card to the blank area of the calibration board:

When the plane where the digital micromirror device of the optical machine is located is offset by the first distance from the central axis of the lens, the first distance is reversely expanded during the calibration process of the optical mechanical imaging surface, so that the plane of the digital micromirror device faces any direction The controller accurately acquires the calibration parameters when translating any distance.
The projection device according to claim 2, wherein the controller is further configured to, in the step of taking a preset number of calibration plate images by the camera and identifying and extracting feature points in the calibration plate images to determine the calibration parameters:

Rotate the calibration board in different postures, and identify the coordinates of the feature points in the projection image under the camera coordinate system;

A world coordinate system is created, and the calibration parameters are determined based on the correspondence between the feature points and the feature points in the calibration chart of the calibration plate in the world coordinate system.
The projection device according to claim 1, the controller is further configured to, in the step of determining the transformation matrix between the world coordinate system and the optical-mechanical coordinate system:

According to the calibration parameters, the feature points of the calibration plate image are converted from the camera coordinate system to the optical machine coordinate system;

Based on the coplanar characteristics of the projection surface and the calibration plate, all feature points of the calibration plate image in the optical-mechanical coordinate system are fitted to obtain the unit normal vector of the projection surface in the optical-mechanical coordinate system;

The rotation matrix is determined according to different representations of the unit normal vector of the projected surface in the optical-mechanical coordinate system and the world coordinate system.
The projection device according to claim 1, wherein the calibration parameters include optomechanical intrinsic parameters and optomechanical and camera extrinsic parameters.
The projection device according to claim 1, wherein the origin of the world coordinate system is set at the origin of the optical-mechanical coordinate system, and its XOY plane is parallel to the projection plane.
The projection device according to claim 1, when the preset projection area is a rectangular area, the apex is a rectangular apex of the rectangular area.
The projection device according to claim 1, the first controller is further configured to:

Based on the projection image acquired by the camera, an edge detection algorithm is used to identify the projection area of the projection device; when the projection area is displayed as a rectangle or similar to a rectangle, the controller obtains the coordinate values of the four vertices of the above-mentioned rectangular projection area through a preset algorithm.
The projection device according to claim 9, the first controller is further configured to:

Use the perspective transformation method to correct the projection area to be a rectangle, and calculate the difference between the rectangle and the projection screenshot to realize whether there are foreign objects in the display area.
The projection device according to claim 9, the first controller is further configured to:

When realizing foreign object detection in a certain area outside the projection range, the camera content of the current frame and the camera content of the previous frame can be compared to determine whether there is foreign matter entering the area outside the projection area; if it is judged that there is foreign matter entering, The projection device automatically triggers the anti-eye function.
The projection device according to claim 1, the first controller is further configured to:

Use time-of-flight cameras or time-of-flight sensors to detect real-time depth changes in specific areas; if the depth value changes beyond a preset threshold, the projection device will automatically trigger the anti-eye function.
The projection device according to claim 9, wherein the first controller is further configured to: determine whether to enable the anti-eye function based on the collected time-of-flight data, screenshot data, and camera data analysis.
The projection device according to claim 9, the first controller is further configured to:

If the user is located in a specific area and his vision is at risk of being damaged by the laser, the anti-eye function will be automatically activated to reduce the intensity of the laser emitted by the optical machine, reduce the brightness of the user interface display, and display a safety reminder message.
The projection device according to claim 9, the first controller is further configured to:

Monitor the movement of the device through a gyroscope or a gyroscope sensor; send signaling to the gyroscope to query the status of the device, and receive signaling from the gyroscope to determine whether the device is moving.
The projection device according to claim 9, the first controller is further configured to:

After the gyroscope data is stable for a preset length of time, the control starts to trigger the keystone correction, and does not respond to the commands issued by the buttons of the remote control when the keystone correction is in progress.
The projection device according to claim 9, the first controller is further configured to:

The screen is recognized by the automatic obstacle avoidance algorithm, and the projected image is corrected to be displayed inside the screen by using the projection change, so as to achieve the effect of aligning with the edge of the screen.
A projection image correction method, the method comprising:

After detecting the movement of the projection device, project the calibration chart to the blank area of the calibration board to determine the calibration parameters;

Based on the calibration parameters and the acquired coordinates of the calibration plate image in the camera coordinate system, determine a transformation matrix between the world coordinate system and the optical-mechanical coordinate system;

According to the above conversion matrix, the first coordinates of the vertices of the preset projection area in the world coordinate system are converted to the optical machine coordinate system to obtain second coordinates, and the playback content is projected to the second coordinates.
The projected image correction method according to claim 18, in the step of determining the calibration parameters by projecting the calibration chart card to the blank area of the calibration board, the method further comprises:

Taking a preset number of calibration plate images, and identifying and extracting the feature points in the calibration plate images, the feature points include the feature points of the projected image in the blank area, and the feature points of the calibration chart set on the calibration plate itself ;

When the difference between the obtained calibration parameter and the preset theoretical value is less than or equal to the preset threshold, it is determined that the calibration parameter has been successfully obtained; otherwise, the step of determining the calibration parameter is re-executed;

Wherein, when it is determined that the number of acquired images of the calibration plate is less than the preset number, or the identification and extraction of the feature points fails, the step of determining the calibration parameters is re-executed.