Projection system and control method thereof

Abstract

A projection system and a control method thereof are provided. The projection system comprises a projection device and a projection screen. The projection equipment comprises a shell, a detection device, a plurality of loudspeakers and a mainboard. The mainboard is configured to obtain point cloud data obtained by detecting at least one target object in a detection area by the detection device; according to the point cloud data of the at least one target object, determining a target sub-region corresponding to the at least one target object in the plurality of sub-regions; and adjusting the audio playing effect of at least one loudspeaker in the plurality of loudspeakers by adopting the sound adjustment parameter corresponding to the target sub-region, the sound adjustment parameter comprises at least one of a sound pressure level of the at least one loudspeaker or a sound pressure level proportion of a plurality of sound channels included by the at least one loudspeaker.

Description

Projection system and control method thereof

[0001] This application claims priority to the Chinese patent application with application number 202211269218.8 filed on October 17, 2022; priority to the Chinese patent application with application number 202211269216.9 filed on October 17, 2022, the entire contents of which are incorporated by reference into this application.

[0002] The present disclosure relates to the field of projection display technology, and in particular to a projection system and a control method thereof.

[0003] With the development of projection display technology, projection equipment is becoming more and more popular. Projection equipment can display projection images in conjunction with a projection screen. In addition, the projection equipment can also play audio corresponding to the projection image to achieve the combination of video and audio.

[0004]

[0005] In one aspect, a projection system is provided. The projection system includes a projection device and a projection screen. The projection device is configured to provide a projection beam, and the projection screen is configured to receive the projection beam to form a projection image. The projection device includes a housing, a detection device, a plurality of speakers, and a mainboard. The detection device is configured to detect at least one target object in a detection area to obtain point cloud data. The detection area includes a plurality of sub-areas. At least one speaker among the plurality of speakers includes a plurality of channels, and the plurality of speakers are configured to play audio corresponding to the projection image. The mainboard is electrically connected to the detection device, and the mainboard is configured to: obtain point cloud data obtained by the detection device detecting at least one target object in the detection area; determine a target sub-area corresponding to the at least one target object in the plurality of sub-areas according to the point cloud data of the at least one target object; and use a sound adjustment parameter corresponding to the target sub-area to adjust the audio playback effect of at least one speaker among the plurality of speakers; the sound adjustment parameter includes at least one of the sound pressure level of the at least one speaker or the sound pressure level ratio of the plurality of channels included in the at least one speaker.

[0006] On the other hand, a control method for a projection system is provided. The projection system includes a projection device and a projection screen. The projection device is configured to provide a projection beam, and the projection screen is configured to receive the projection beam to form a projection image. The projection device includes a housing, a detection device, and a plurality of speakers. The detection device is configured to detect at least one target object in a detection area to obtain point cloud data. The detection area includes a plurality of sub-areas. At least one speaker among the plurality of speakers includes a plurality of channels, and the plurality of speakers are configured to play audio corresponding to the projection image. The method includes: acquiring point cloud data obtained by the detection device detecting at least one target object in the detection area; determining a target sub-area corresponding to the at least one target object in the plurality of sub-areas according to the point cloud data of the at least one target object; adjusting the audio playback effect of at least one speaker among the plurality of speakers using a sound adjustment parameter corresponding to the target sub-area; the sound adjustment parameter includes at least one of the sound pressure level of the at least one speaker or the sound pressure level ratio of the plurality of channels included in the at least one speaker.

[0007] In order to more clearly illustrate the technical solutions in the present disclosure, the following briefly introduces the drawings required for use in some embodiments of the present disclosure. However, the drawings described below are only drawings of some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams, and are not intended to limit the actual size of the product involved in the embodiments of the present disclosure, the actual process of the method, the actual timing of the signal, etc.

[0008] FIG1 is a structural diagram of a projection system according to some embodiments;

[0009] FIG2 is a structural diagram of a projection device according to some embodiments;

[0010] FIG3 is a structural diagram of a millimeter wave radar sensor according to some embodiments;

[0011] FIG4A is a graph showing the amplitude of a first detection signal changing over time according to some embodiments;

[0012] FIG4B is a schematic diagram showing how the frequency of a first detection signal varies with time according to some embodiments;

[0013] FIG5 is a schematic diagram of a first detection signal and a second detection signal according to some embodiments;

[0014] FIG6 is a spectrum diagram of two second detection signals according to some embodiments;

[0015] FIG7A is a schematic diagram of a target relative to a millimeter wave radar sensor according to some embodiments;

[0016] FIG7B is a schematic diagram of an angle change of a target object relative to a millimeter wave radar sensor according to some embodiments;

[0017] FIG8 is a flow chart of steps performed by a mainboard according to some embodiments;

[0018] FIG9A is a schematic diagram of a detection area of ​​a detection device according to some embodiments;

[0019] FIG9B is a schematic diagram of another detection area of ​​a detection device according to some embodiments;

[0020] FIG9C is a schematic diagram of another detection area of ​​a detection device according to some embodiments;

[0021] FIG10 is another flow chart of steps performed by a mainboard according to some embodiments;

[0022] FIG11 is another flow chart of the steps executed by the mainboard according to some embodiments;

[0023] FIG12 is another flow chart of the steps executed by the mainboard according to some embodiments;

[0024] FIG13 is another flow chart of the steps executed by the mainboard according to some embodiments;

[0025] FIG14 is a schematic diagram of a second motion trajectory of a target object within a detection area according to some embodiments;

[0026] FIG15 is another schematic diagram of a second motion trajectory of a target object within a detection area according to some embodiments;

[0027] FIG16 is another flow chart of the steps executed by the mainboard according to some embodiments;

[0028] FIG17A is another flow chart of steps executed by a mainboard according to some embodiments;

[0029] FIG17B is another flow chart of the steps performed by the mainboard according to some embodiments;

[0030] FIG18A is another flow chart of steps performed by a mainboard according to some embodiments;

[0031] FIG. 18B is another flow chart of the steps executed by the mainboard according to some embodiments.

[0032] Some embodiments of the present disclosure will be described clearly and completely below in conjunction with the accompanying drawings. However, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field are within the scope of protection of the present disclosure.

[0033] Unless the context requires otherwise, throughout the specification and claims, the term "comprise" and other forms thereof, such as the third person singular form "comprises" and the present participle form "comprising", are to be interpreted as open, inclusive, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples" and the like are intended to indicate that specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0034] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "plurality" means two or more.

[0035] When describing some embodiments, the expression "connection" and its derivatives may be used. The term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. The embodiments disclosed herein are not necessarily limited to the contents of this document.

[0036] “At least one of A, B, and C” has the same meaning as “at least one of A, B, or C” and both include the following combinations of A, B, and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B, and C.

[0037] As used herein, the term "if" is optionally interpreted to mean "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined that" or "if [a stated condition or event] is detected" are optionally interpreted to mean "upon determining that" or "in response to determining that" or "upon detecting [a stated condition or event]" or "in response to detecting [a stated condition or event]," depending on the context.

[0038] The use of "adapted to" or "configured to" herein is meant to be open and inclusive language that does not exclude devices adapted or configured to perform additional tasks or steps.

[0039] Additionally, the use of “based on” is meant to be open and inclusive, as a process, step, calculation, or other action “based on” one or more stated conditions or values ​​may, in practice, be based on additional conditions or values ​​beyond those stated.

[0040] As used herein, "about," "substantially," or "approximately" includes the stated value and an average value that is within an acceptable range of variation from the particular value as determined by one of ordinary skill in the art taking into account the measurements in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0041] As used herein, "parallel," "perpendicular," and "equal" include the stated conditions and conditions approximate to the stated conditions, the range of which is within an acceptable range of deviation as determined by a person of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system).

[0042] Usually, when the user does not actively adjust the direction of the sound and the playback volume (i.e., sound pressure level) of the speaker (such as a stereo) in the projection device, the direction of the sound emitted by the speaker and the sound pressure level of the speaker are fixed. When the user is located at different positions of the projection device, the direction and sound pressure level of the sound heard by the user are different. For example, the farther the distance between the user and the projection device, the smaller the sound pressure level of the sound heard by the user. Therefore, the audio playback effect of the projection device is poor. Here, the direction of the sound can be understood as the sound pressure level ratio of the multiple channels included in the speaker.

[0043] In order to solve the above problems, some embodiments of the present disclosure provide a projection system 1.

[0044] FIG1 is a structural diagram of a projection system according to some embodiments. As shown in FIG1 , the projection system 1 includes a projection device 10 and a projection screen 40 .

[0045] The projection screen 40 is located on one side of the projection device 10 (e.g., the light emitting side of the projection device 10), and the audience faces the projection screen 40. After the projection light beam emitted from the projection device 10 is incident on the projection screen 40, it is reflected by the projection screen 40 and enters the human eye, so that the audience can see the projected image.

[0046] In some embodiments, as shown in FIG. 1 , the projection device 10 includes a housing 60 , a detection device 20 , and a plurality of speakers 30 .

[0047] The detection device 20 and the plurality of speakers 30 are respectively installed in the housing 60. The detection device 20 faces the side of the housing 60 away from the projection screen 40 (such as the front side). The detection device 20 can be a millimeter wave radar sensor. The plurality of speakers 30 are installed at different positions of the housing 60 and are configured to play audio corresponding to the projected image. It should be noted that the detection device 20 and the plurality of speakers 30 can also be installed on the surface of the housing 60, and the present disclosure does not limit this.

[0048] In some embodiments, as shown in Fig. 1, the plurality of speakers 30 include a first speaker 31, a second speaker 32, and a third speaker 33. One speaker 30 may include a plurality of channels. For example, one speaker includes a left channel and a right channel.

[0049] As shown in FIG1 , the first speaker 31 includes a first left channel 31L and a first right channel 31R. The first left channel 31L and the first right channel 31R may be located at a first side of the housing 60, respectively, and the first speaker 31 may be referred to as a front speaker. The second speaker 32 includes a second left channel 32L and a second right channel 32R. The second left channel 32L may be located at a second side of the housing 60, the second right channel 32R may be located at a third side of the housing 60, and the second speaker 32 may also be referred to as a surround speaker. The third speaker 33 includes a third left channel 33L and a third right channel 33R. The third left channel 33L and the third right channel 33R may be located at a fourth side of the housing 60, respectively, and the third speaker 33 may also be referred to as a sky speaker.

[0050] Here, the first side may be a side (such as the front side) of the housing 60 that is parallel to the projection screen 40 and away from the projection screen 40. The second side and the third side may be two opposite sides (such as the right side and the left side) of the housing 60 that are perpendicular to the first side, and the fourth side may be a side (such as the upper side) of the housing 60 that is parallel to the placement plane of the projection device 10 and away from the placement plane. The second side and the third side may also be referred to as the side surfaces of the housing 60, and the fourth side may also be referred to as the top of the housing 60.

[0051] In some embodiments of the present disclosure, after entering the power-on state, the projection device 10 projects a projection beam to the projection screen 40, so that the projection screen 40 displays a projection image. In addition, the projection device 10 can control the multiple speakers 30 to play audio while the projection screen 40 displays the projection image.

[0052] FIG. 2 is a structural diagram of a projection device according to some embodiments.

[0053] In some embodiments, as shown in Figure 2, the projection device 10 also includes a power supply circuit 110, a multimedia processing circuit 120, a display control circuit 130, a light source driving circuit 140, a light source component 150, an optical modulation component 160, a projection lens 170 and an infrared signal processing circuit 180.

[0054] The power circuit 110 is electrically connected to the multimedia processing circuit 120, the display control circuit 130 and the light source driving circuit 140. The power circuit 110 is configured to provide voltage to the multimedia processing circuit 120, the display control circuit 130 and the light source driving circuit 140 to drive the multimedia processing circuit 120, the display control circuit 130 and the light source driving circuit 140 to work.

[0055] The multimedia processing circuit 120 is electrically connected to the display control circuit 130 and the detection device 20, respectively. The multimedia processing circuit 120 is configured to receive a video signal, process the video signal, and transmit the processed video signal to the display control circuit 130. In addition, the multimedia processing circuit 120 is also configured to provide a working voltage to the detection device 20 to drive the detection device 20 to work. Accordingly, the detection device 20 can send the point cloud data collected during the working process to the multimedia processing circuit 120, and the multimedia processing circuit 120 can control the working state of the speaker 30 according to the point cloud data, thereby adjusting the audio playback effect of the projection system 1.

[0056] Here, the multimedia processing circuit 120 may also be referred to as the main board 100 or the TV board. The working state of the speaker 30 includes the sound pressure level of the speaker 30 and the ratio of the sound pressure levels of the multiple channels of the speaker 30. In addition, it should be noted that the above point cloud refers to a data set of feature points on the product appearance surface obtained by the detection device 20.

[0057] The display control circuit 130 is configured to process the video signal received from the multimedia processing circuit 120, and output the processed video signal to the optical modulation component 160. In addition, the display control circuit 130 is also configured to output a light source driving signal to the light source driving circuit 140 according to the video signal. Here, the display control circuit 130 may also be referred to as a display panel.

[0058] For example, the multimedia processing circuit 120 and the display control circuit 130 are respectively a central processing unit (CPU), a microprocessor (MPU), a chip, a microchip, an integrated circuit (IC), etc. It should be noted that since the multimedia processing circuit 120 and the display control circuit 130 have different functions, the composition structures of the two may be different.

[0059] The light source driving circuit 140 is electrically connected to the display control circuit 130 and is configured to receive a light source driving signal and output a driving current to the light source assembly 150 according to the light source driving signal to drive the light source 1500 in the light source assembly 150 to emit light.

[0060] The light source assembly 150 includes a plurality of light sources 1500 , which may be laser light sources, light-emitting diodes (LEDs) or other types of light sources. The light source assembly 150 is configured to emit an illumination beam under the drive of the light source driving circuit 140 .

[0061] The optical modulation component 160 is located at the light-emitting side of the light source component 150, and is configured to modulate the illumination beam emitted by the light source component 150 according to the video signal processed by the display control circuit 130 to obtain a projection beam. For example, the optical modulation component 160 includes a digital micromirror device (DMD) and a DMD driving circuit. The DMD driving circuit is configured to drive the DMD to work according to the video signal. The DMD is configured to modulate the illumination beam emitted by the light source component 150 under the control of the DMD driving circuit to obtain a projection beam.

[0062] The projection lens 170 is located at the light-emitting side of the optical modulation component 160 , and is configured to amplify the projection light beam and project the projection light beam onto the projection screen 40 to form an image.

[0063] The infrared signal processing circuit 180 is connected to the multimedia processing circuit 120 and the detection device 20 respectively. The infrared signal processing circuit 180 is configured to receive the control instruction sent by the detection device 20, and send an infrared coded signal to the multimedia processing circuit 120 based on the control instruction. The multimedia processing circuit 120 can control the working state of multiple components in the projection device 10 in response to the infrared coded signal. For example, the multimedia processing circuit 120 controls the display control circuit 130, the light source driving circuit 140 and the optical modulation component 160 to work in response to the infrared coded signal.

[0064] In some examples, as shown in FIG2 , the infrared signal processing circuit 180 includes a first subcircuit 181 and a second subcircuit 182. The first subcircuit 181 (e.g., an infrared receiver) is communicatively connected to a remote control device 50 (e.g., a remote controller) in the projection system 1, and is configured to receive an infrared control signal sent by the remote control device 50, and send the infrared control signal to the second subcircuit 182. The second subcircuit 182 can be communicatively connected to the detection device 20, and is configured to send an infrared coded signal to the multimedia processing circuit 120 based on the infrared control signal sent by the first subcircuit 181 or the control instruction sent by the detection device 20, so as to control the working state of multiple components in the projection device 10.

[0065] In some embodiments, the detection device 20 and the remote control device 50 can communicate with the infrared signal processing circuit 180 through an infrared communication protocol respectively, and the infrared signal processing circuit 180 can also communicate with the multimedia processing circuit 120 through the infrared communication protocol.

[0066] The following description will be made by taking the detection device 20 as a millimeter wave radar sensor as an example.

[0067] FIG3 is a structural diagram of a millimeter wave radar sensor according to some embodiments. As shown in FIG3, the detection device 20 includes: a driving circuit 21, a signal synthesizer 22, one or more transmitting antennas 23, and a plurality of receiving antennas 24 arranged in an array. The signal transmission direction of the plurality of transmitting antennas 23 is a direction away from the projection screen 40.

[0068] The driving circuit 21 is electrically connected to the multimedia processing circuit 120. The multimedia processing circuit 120 provides a voltage to the driving circuit 21. Based on the voltage, the driving circuit 21 can provide a driving voltage to the signal synthesizer 22 to drive the signal synthesizer 22 to generate a first detection signal. Afterwards, the signal synthesizer 22 can transmit the first detection signal to at least one transmitting antenna 23 to transmit the first detection signal. The first detection signal emitted by the transmitting antenna 23 can be received by multiple receiving antennas 24 after being reflected by the target object. Here, the target object can be a moving object such as a person located within the detection range of the detection device 20. In addition, for ease of explanation, the first detection signal reflected by the target object can be referred to as the second detection signal.

[0069] For example, FIG. 4A is a graph showing how the amplitude of a first detection signal varies with time according to some embodiments. FIG. 4B is a schematic diagram showing how the frequency of a first detection signal varies with time according to some embodiments. The frequency Fs in FIG. 4B is the starting frequency of the first detection signal, and the frequency Fe in FIG. 4B is the ending frequency. The bandwidth B of the first detection signal within the duration Tc is equal to the difference between the ending frequency Fe and the starting frequency Fs (e.g., B=Fe-Fs). The slope S in FIG. 4B is the rate of change of the frequency of the first detection signal within the duration Tc. As shown in FIGS. 4A and 4B, the frequency F of the first detection signal increases linearly with time t, and therefore, the first detection signal can also be referred to as a linear frequency modulation pulse signal. It should be noted that the duration Tc can be used as the target duration when calculating the moving speed of the target object.

[0070] FIG5 is a schematic diagram of a first detection signal and a second detection signal according to some embodiments. FIG5 shows the change in the frequency of the first detection signal and the second detection signal over time. As shown in FIG5, the time interval between the first detection signal (i.e., the output (Transmit, TX) signal) transmitted by the detection device 20 through the transmitting antenna 23 and the second detection signal (i.e., the receiving (Receive, RX) signal) received by the receiving antenna 24 is the duration τ. In other words, the transmission time of the first detection signal transmitted by the transmitting antenna 23 between the projection device 10 and the target object is the duration τ. The duration τ can also be referred to as the delay time, and the frequency difference f0 between the first detection signal and the second detection signal is equal to the product of the slope S and the duration τ (e.g., f0=S×τ).

[0071] 3, the detection device 20 further includes a mixer 25. The mixer 25 is configured to perform mixing processing on the first detection signal generated by the signal synthesizer 22 and the second detection signal received by the plurality of receiving antennas 24 to obtain an intermediate frequency signal corresponding to each receiving antenna 24. Here, the frequency of the intermediate frequency signal corresponding to the receiving antenna 24 is the frequency difference f0 between the first detection signal transmitted by the transmitting antenna 23 and the second detection signal received by the receiving antenna 24.

[0072] Referring to FIG3 , the detection device 20 further includes a filter 26, a digital-to-analog converter 27, a preprocessing circuit 28, and a main control circuit 29. The filter 26 is configured to filter the intermediate frequency signal of each receiving antenna 24 to filter out the clutter in the intermediate frequency signal. The digital-to-analog converter 27 is configured to perform digital-to-analog conversion on the filtered intermediate frequency signal to convert the intermediate frequency signal corresponding to the receiving antenna 24 into an analog signal. The preprocessing circuit 28 is configured to preprocess the converted analog signal and transmit the preprocessed analog signal to the main control circuit 29.

[0073] The main control circuit 29 is configured to sample and perform analog-to-digital conversion (i.e., quantization) on the analog signal corresponding to the receiving antenna 24. Afterwards, the main control circuit 29 can perform Fourier transform on the analog signal corresponding to the receiving antenna 24 in the range dimension and the Doppler dimension (also called the velocity dimension) to obtain a range-doppler matrix (RDM). The range-doppler matrix can also be referred to as a two-dimensional grid data table of the range dimension and the Doppler dimension. The main control circuit 29 can determine the distance between the target object and the projection system 1 based on the peak value in the two-dimensional grid data table. For example, if the peak value in the two-dimensional grid data table is 2 meters, the main control circuit 29 can determine that the distance between the target object and the projection system 1 is 2 meters.

[0074] In the range-Doppler matrix, the main control circuit 29 can perform cell average constant false alarm rate (CA-CFAR) along the Doppler dimension, and perform cell average constant false alarm rate (CA-CFAR) along the range dimension, thereby obtaining a two-dimensional grid data table of the range dimension and the Doppler dimension, and a two-dimensional grid data table of the azimuth dimension and the Doppler dimension. A cell in a two-dimensional data table (such as each two-dimensional data table) is a point in the point cloud. After obtaining three two-dimensional grid data tables (such as two-dimensional grid data tables of the range dimension, the Doppler dimension, and the azimuth dimension), the main control circuit 29 can perform incoherent accumulation of the data (i.e., signals) indicated by the three two-dimensional grid data tables, thereby obtaining three-dimensional point cloud data of the range dimension-azimuth dimension-Doppler dimension, where each point in the three-dimensional point cloud data has characteristic information such as distance, angle, and speed.

[0075] The following is an explanation of the distance measurement, speed measurement, and azimuth measurement functions of the millimeter wave radar sensor.

[0076] According to the ranging principle of the millimeter wave radar sensor, for the frequency f0 (f0=S×τ) of the intermediate frequency signal of the receiving antenna 24, the delay time τ satisfies the following formula:

[0077] Here, d is the distance between the millimeter wave radar sensor and the target object. In other words, d is the distance between the target object and the projection system 1. C is the speed of light. It should be noted that, since the detection area of ​​the millimeter wave radar sensor is fan-shaped, the distance d between the millimeter wave radar sensor and the target object is the radial distance between the millimeter wave radar sensor and the target object.

[0078] In this case, the distance d of the target object relative to the projection system 1 satisfies the following formula:

[0079] Here, S is the rate of change of the frequency of the first detection signal within the duration Tc, and the rate of change S is determined by the difference between the end frequency Fe and the start frequency Fs of the first detection signal (i.e., the bandwidth B). The speed of light C is a fixed value. Therefore, by measuring the frequency f0 of the intermediate frequency signal, the distance between the target and the projection system 1 can be determined.

[0080] Based on the Doppler frequency shift principle, when the target moves in a certain direction at a constant speed, the phase and frequency of the intermediate frequency signal synthesized by the mixer 25 in the millimeter wave radar sensor change due to the difference in the propagation distance of the wave. In other words, the distance change caused by the movement of the target can cause the phase change of the intermediate frequency signal. Therefore, by measuring the phase change of the intermediate frequency signal synthesized by the mixer 25, the speed of the target within the target time length Tc can be determined.

[0081] For example, the initial phase φ0 of the intermediate frequency signal at the first moment T0 satisfies formula (3), and the speed of light C satisfies formula (4): φ0=2π×f0×τ; (3) C=λ×f0; (4)

[0082] According to formulas (1), (3) and (4), we can get the following formula (5):

[0083] Here, λ is the wavelength of the first detection signal emitted by the millimeter wave radar sensor.

[0084] Therefore, according to formula (5), the displacement Δd1 of the target from the first moment T0 to the second moment T1 and the change Δφ1 of the phase of the intermediate frequency signal received by the millimeter wave radar sensor within the target time length Tc (that is, Tc = T1-T0) satisfy formula (6):

[0085] Here, the target duration Tc is the moving duration of the target object.

[0086] In this case, since the displacement Δd1 of the target object from the first moment T0 to the second moment T1 is equal to the product of the moving speed V of the target object and the target duration Tc (i.e., Δd1=V×Tc), it can be determined according to formula (6) that the moving speed V of the target object satisfies formula (7):

[0087] It is understandable that the millimeter wave radar sensor can transmit the first detection signal through at least one transmitting antenna 23 every target duration Tc. That is, the duration of each first detection signal is the target duration Tc. If the millimeter wave radar sensor transmits the first detection signals TX1 and TX2 through at least one transmitting antenna 23 every target duration Tc, the first detection signals TX1 and TX2 can be reflected by the target object to obtain the second detection signals RX1 and RX2. If the target object is in a stationary state, the second detection signals RX1 and RX2 have the same frequency and the same phase (that is, the phase difference is 0).

[0088] FIG. 6 is a spectrum diagram of two second detection signals according to some embodiments. FIG. 6 shows the frequency, amplitude, and phase of the second detection signals RX1 and RX2. When the target object is in motion (i.e., the moving speed V is not 0), as shown in FIG. 6, the phases of the second detection signals RX1 and RX2 are different (i.e., the phase difference is not 0). Therefore, the millimeter wave radar sensor can determine whether the target object is in motion based on the phase difference of the second detection signals RX1 and RX2.

[0089] For the angle measurement principle of the millimeter wave radar sensor, when the distance between the target and the projection system 1 changes slightly, the phase of the intermediate frequency signal corresponding to the second detection signal reflected by the target may change significantly. Based on this, the millimeter wave radar sensor can estimate the angle of arrival (AOA) of the second detection signal based on the phase change caused by the distance difference between the target and any two receiving antennas 24 in the millimeter wave radar sensor. Here, the angle of arrival can be understood as the azimuth of the target.

[0090] FIG7A is a schematic diagram of a target relative to a millimeter-wave radar sensor according to some embodiments. FIG7B is a schematic diagram of an angle change of a target relative to a millimeter-wave radar sensor according to some embodiments. Referring to FIG7A , a transmitting antenna transmits a first detection signal to a target, and a second detection signal generated after the first detection signal is reflected by the target is received by a first receiving antenna 11 and a second receiving antenna 12 in the millimeter-wave radar sensor, respectively. The distance between the first receiving antenna 11 and the second receiving antenna 12 is L, the distance between the target and the first receiving antenna 11 is D1, and the distance between the target and the second receiving antenna 12 is D2. The distance difference Δd between the target and the two receiving antennas (i.e., Δd=D2-D1) satisfies formula (8): Δd=L×sin(θ); (8)

[0091] 7B , θ is the angle change of the target object relative to the millimeter wave radar sensor within the target time length Tc, and the distance difference Δd between the two receiving antennas is approximately the moving distance of the target object within the target time length Tc.

[0092] Since the phase difference Δφ of the intermediate frequency signal corresponding to the first receiving antenna 11 and the second receiving antenna 12 satisfies formula (9):

[0093] Therefore, it can be determined that the angle change θ of the target object relative to the millimeter wave radar sensor within the target time length Tc satisfies formula (10):

[0094] In this way, the millimeter wave radar sensor can determine the azimuth angle of the target object relative to the projection system 1 based on the phase difference of at least two intermediate frequency signals corresponding to at least two receiving antennas 24 among the multiple receiving antennas 24 and the difference in distance between the target object and the at least two receiving antennas 24.

[0095] Fig. 8 is a flow chart of the steps executed by the mainboard according to some embodiments. In some embodiments, as shown in Fig. 8 , the mainboard 100 (ie, the multimedia processing circuit 120 ) is configured to execute steps 101 to 103 .

[0096] In step 101 , point cloud data obtained by the detection device 20 detecting at least one target object in a detection area is obtained.

[0097] The detection device 20 (such as a millimeter wave radar sensor) can detect the detection area of ​​the detection device 20 in real time. When at least one target object enters the detection area, the detection device 20 can detect the target object to obtain point cloud data of the at least one target object. Afterwards, the multimedia processing circuit 120 in the projection device 10 can obtain the point cloud data of the at least one target object detected by the detection device 20.

[0098] Here, the point cloud data of the target object includes the distance between the target object and the projection system 1, the moving speed of the target object, and the azimuth of the target object relative to the projection system 1. It should be noted that the relative position (such as distance and azimuth) and relative speed (moving speed) between the target object and the projection system 1 refer to the relative position and relative speed between the target object and the detection device 20. In addition, the detection area of ​​the detection device 20 may include multiple sub-areas.

[0099] In some embodiments, the detection area of ​​the detection device 20 can be determined based on the propagation range of the first detection signal emitted by the transmitting antenna 23 in the detection device 20, and the signal receiving range of the receiving antenna 24. For example, the detection area is fan-shaped, and multiple sub-areas can be arranged along at least one of the radial or circumferential directions of the fan. Here, the detection area is fan-shaped, which can mean that the detection area is fan-shaped in a placement plane parallel to the projection device 10, and the vertex of the fan can be the position where the detection device 20 is located. The radial direction of the fan can be the propagation direction of the first detection signal emitted by the transmitting antenna 23 in the detection device 20, and the circumferential direction of the fan is perpendicular to the radial direction of the fan.

[0100] Fig. 9A is a schematic diagram of a detection region of a detection device according to some embodiments. Fig. 9B is a schematic diagram of another detection region of a detection device according to some embodiments. Fig. 9C is a schematic diagram of yet another detection region of a detection device according to some embodiments.

[0101] For example, referring to FIG9A , a plurality of sub-regions are arranged in the radial direction and circumferential direction of the sector, respectively. Alternatively, referring to FIG9B , a plurality of sub-regions are arranged in the radial direction of the sector, and the widths of the plurality of sub-regions in the radial direction are the same. Alternatively, referring to FIG9C , a plurality of sub-regions are arranged in the circumferential direction of the sector (i.e., each sub-region is a sector), and the plurality of sub-regions share a vertex, and the central angles of the plurality of sub-regions are equal.

[0102] In step 102, a target sub-region corresponding to the at least one target object in a plurality of sub-regions is determined according to point cloud data of the at least one target object.

[0103] The multimedia processing circuit 120 in the projection device 10 can determine the position of the at least one target object in the detection area according to the point cloud data of the at least one target object, and further determine the sub-area in which each of the at least one target object is located in the detection area. In this case, the multimedia processing circuit 120 can determine the target sub-area corresponding to the at least one target object in the multiple sub-areas.

[0104] In step 103, the audio playing effect of at least one speaker 30 among the multiple speakers 30 is adjusted using the sound adjustment parameter corresponding to the target sub-area.

[0105] The projection device 10 pre-stores a correspondence between a plurality of sub-areas and sound adjustment parameters. For example, the projection device 10 further includes a memory, which is connected to the mainboard 100 and stores a correspondence between a plurality of sub-areas and sound adjustment parameters. After determining the target sub-area corresponding to at least one target object, the multimedia processing circuit 120 can determine the sound adjustment parameter corresponding to the target sub-area based on the correspondence between the target sub-area and the sound adjustment parameter. Afterwards, the multimedia processing circuit 120 can use the sound adjustment parameter corresponding to the target sub-area to adjust the audio playback effect of at least one speaker 30 among the plurality of speakers 30.

[0106] Here, the sound adjustment parameter includes at least one of the sound pressure level of the speaker 30 or the ratio of the sound pressure levels of the multiple channels included in the speaker 30. The sound pressure level of the speaker 30 can reflect the playback volume of the speaker 30. The ratio of the sound pressure levels of the multiple channels included in the speaker 30 can reflect the sound emission direction of the speaker 30 (e.g., the propagation direction of the audio).

[0107] In addition, the memory may be a random access memory (RAM), a flash memory, a read only memory (ROM), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM), a register, a hard disk, a mobile hard disk, a CD-ROM or any other form of storage medium known in the art. The memory may exist independently and be connected to the mainboard 100, or the memory may be integrated with components in the mainboard 100.

[0108] It should be noted that, since the multiple sub-areas are located at different positions relative to the projection device 10, the sound adjustment parameters corresponding to the multiple sub-areas are not the same. The projection device 10 uses the sound adjustment parameters corresponding to the target sub-area where at least one target object is located to adjust the audio playback effect of at least one speaker 30 among the multiple speakers 30, so that the playback effect of the speaker 30 heard by at least one target object in at least one sub-area in the detection area is roughly the same. In other words, when at least one target object is located in different sub-areas of the detection area, at least one of the playback volume of the audio or the propagation direction of the audio heard by the at least one target object is roughly the same. In this way, the audio playback effect of the projection system 1 can be flexibly adjusted to improve the audio playback effect of the projection system 1.

[0109] For example, as shown in Fig. 9A, the detection area of ​​the detection device 20 includes 10 sub-areas. The sound adjustment parameters corresponding to the 10 sub-areas may be as shown in Table 1. Here, the unit of the sound pressure level is decibel (dB).

[0110] Table 1

[0111] The sound pressure level of one speaker 30 may be an average of the sound pressure levels of the multiple channels included in the speaker 30. The sound pressure levels of the multiple channels in one speaker 30 may be determined based on the sound pressure level of the speaker 30 and the ratio of the sound pressure levels of the multiple channels in the speaker 30.

[0112] In some examples, the sound pressure level ratio of the speaker 30 shown in Table 1 may be the sound pressure level ratio of the left channel in the speaker 30. For example, in the sound adjustment parameters corresponding to sub-area A, the sound pressure level of each speaker 30 is 30 dB, and the sound pressure level ratio of the left channel in each speaker 30 is 50%, then the sound pressure levels of the left channel and the right channel in each speaker 30 may be 30 dB, respectively. In the sound adjustment parameters corresponding to sub-area B, the sound pressure level of each speaker 30 is 40 dB, and the sound pressure level ratio of the left channel in each speaker 30 is 25%, then the sound pressure level of the left channel in each speaker 30 is 20 dB, and the sound pressure level of the right channel is 60 dB.

[0113] Fig. 10 is another flow chart of the mainboard execution steps according to some embodiments. In some embodiments, as shown in Fig. 10 , step 101 includes step 1011 and step 1012 .

[0114] In step 1011 , a data transmission request sent by the detection device 20 is received.

[0115] In step 1012, according to the data transmission request, point cloud data obtained by the detection device 20 detecting at least one target object in the detection area is obtained.

[0116] After the detection device 20 detects at least one target object and obtains the point cloud data of the at least one target object, the detection device 20 can send a data transmission request to the multimedia processing circuit 120, and the multimedia processing circuit 120 can actively acquire the point cloud data in response to the data transmission request.

[0117] The multimedia processing circuit 120 can communicate with the detection device 20 through the Inter-integrated Circuit (IIC) protocol. Since the detection device 20 is a slave and the multimedia processing circuit 120 is a host in the IIC protocol, the detection device 20 cannot actively send point cloud data to the multimedia processing circuit 120. In this case, after obtaining the point cloud data of at least one target object, the detection device 20 can send a data transmission request to the multimedia processing circuit 120 to instruct the multimedia processing circuit 120 to actively obtain the point cloud data. After receiving the data transmission request from the detection device 20, the multimedia processing circuit 120 can actively obtain the point cloud data detected by the detection device 20 through the IIC protocol.

[0118] It should be noted that data transmission is controlled by the host. The host refers to the device that starts and stops data transmission. The slave is the device that is accessed by the host.

[0119] Fig. 11 is another flow chart of the mainboard execution steps according to some embodiments. In some embodiments, as shown in Fig. 11 , step 102 includes steps 1021 to 1025 .

[0120] In step 1021 , based on the point cloud data of at least one target object, it is determined whether at least one target object is in a stationary state. If so, step 1022 is executed; if not, step 1025 is executed.

[0121] The multimedia processing circuit 120 can determine whether each of the at least one target object is currently in a stationary state or a moving state based on the point cloud data of the at least one target object. If each target object is in a stationary state, step 1022 can be executed. If any of the at least one target object is in a moving state, step 1025 can be executed.

[0122] The point cloud of the target object may include multiple feature points of the target object, and the data of each feature point may include: the distance between the feature point and the projection system 1, the moving speed of the feature point, and the azimuth of the feature point relative to the projection system 1. In this way, the multimedia processing circuit 120 can determine whether the target object is currently in a stationary state or a moving state according to the moving speed of the multiple feature points of each target object.

[0123] In step 1022, it is determined whether at least one target object is located in the same sub-area of ​​the detection area. If so, step 1023 is executed; if not, step 1024 is executed.

[0124] In the case where the detection area of ​​the detection device 20 includes multiple sub-areas, after determining that at least one target object is in a stationary state, the multimedia processing circuit 120 can determine the position of each target object relative to the projection device 10 based on the point cloud data of each target object, thereby determining the sub-area where each target object is located. For example, the multimedia processing circuit 120 determines the distance between the target object and the projection device 10 and the azimuth angle of the target object relative to the projection device 10 based on the point cloud data of the target object, thereby determining the position of the target object relative to the projection device 10.

[0125] After determining the sub-region where each target object is located, the multimedia processing circuit 120 can determine whether the at least one target object is located in the same sub-region within the detection region. If the at least one target object is located in the same sub-region within the detection region, step 1023 can be executed; if the at least one target object is located in different sub-regions within the detection region (i.e., there are multiple targets within the detection region, and the multiple targets are located in different sub-regions), step 1024 can be executed.

[0126] In step 1023, the sub-region where the at least one target object is located is determined as the target sub-region.

[0127] If it is determined that at least one target object is located in the same sub-region, the multimedia processing circuit 120 may directly determine the sub-region as the target sub-region corresponding to the at least one target object.

[0128] For example, referring to FIG. 9A , if it is determined that at least one target object in the detection area is located in sub-area B, the multimedia processing circuit 120 directly determines the sub-area B as the target sub-area.

[0129] In step 1024 , a target sub-region is determined from the at least two sub-regions where the multiple targets are located.

[0130] If it is determined that there are multiple targets in the detection area, and the multiple targets are located in at least two sub-areas in the detection area, the multimedia processing circuit 120 may determine a target sub-area from the at least two sub-areas where the multiple targets are located. Here, the target sub-area may satisfy at least one of the following conditions:

[0131] First condition: the target sub-region is a sub-region that is closer to the projection system 1 and closer to the central axis of the detection region relative to the other sub-regions in the at least two sub-regions. In other words, the target sub-region is the sub-region that is closest to the projection system 1 and the central axis of the detection region in the at least two sub-regions where the multiple targets are located. The central axis of the detection region (such as the dot-dash line P in FIG. 9A ) can be an axis that is perpendicular to the projection screen 40 and parallel to the placement plane of the projection device 10.

[0132] Second condition: the target sub-region contains more target objects than other sub-regions in at least two sub-regions. In other words, the target sub-region is the sub-region containing the largest number of target objects among at least two sub-regions where multiple target objects are located.

[0133] Third condition: the target sub-region is a sub-region where the center point between at least two sub-regions is located. In other words, the target sub-region is a sub-region where the center point of at least two sub-regions where multiple targets are located is located.

[0134] According to the first condition, the multimedia processing circuit 120 may determine the sub-region where the target object closer to the projection system 1 is located as the target sub-region. According to the second condition, the multimedia processing circuit 120 may determine the sub-region containing the largest number of target objects as the target sub-region. According to the third condition, the multimedia processing circuit 120 may determine the sub-region where the center point between the multiple sub-regions where the target object is located is located as the target sub-region. It should be noted that the priorities among the three conditions can be flexibly combined according to actual needs, and the present disclosure does not limit this.

[0135] In some examples, the multimedia processing circuit 120 may first filter out a first candidate sub-region that satisfies the first condition from a plurality of sub-regions, and if the number of the first candidate sub-regions is greater than 1, a target sub-region that satisfies the second condition may be filtered out from the plurality of first candidate sub-regions. Alternatively, the multimedia processing circuit 120 may first filter out a second candidate sub-region that satisfies the second condition from a plurality of sub-regions, and if the number of the second candidate sub-regions is greater than 1, a target sub-region that satisfies the first condition may be filtered out from the plurality of second candidate sub-regions. In addition, if the number of the first candidate sub-regions or the second candidate sub-regions determined by the multimedia processing circuit 120 is greater than 1, a target sub-region that satisfies the third condition may be filtered out from the first candidate sub-regions or the second candidate sub-regions. In other words, the multimedia processing circuit 120 may determine the sub-region where the center point between at least two first candidate sub-regions or at least two second candidate sub-regions is located as the target sub-region.

[0136] For example, referring to FIG9A , if it is determined that there are two targets in the detection area, and the two targets are located in sub-area D and sub-area E, respectively, then according to the first condition, the projection device 10 can determine sub-area E as the target sub-area. Alternatively, if it is determined that there are three targets in the detection area, and two of the three targets are located in sub-area D, and the other target is located in sub-area E, then according to the second condition, the projection device 10 can determine sub-area D as the target sub-area. Alternatively, if it is determined that there are three targets in the detection area, and the three targets are located in sub-area G, sub-area H, and sub-area I, respectively, then according to the third condition, the projection device 10 can determine sub-area H as the target sub-area.

[0137] It can be understood that, in addition to the above manner, the projection device 10 can also randomly select a sub-region from at least two sub-regions as the target sub-region.

[0138] In some embodiments, when at least one target object is located at the junction of two sub-areas, the main board 100 is further configured as follows: if the junction coincides with the central axis of the detection area, the sound adjustment parameters corresponding to the junction are determined according to the distance between the junction and the projection device 10 and the sound adjustment parameters of the reference sub-area, and the audio playback effect of at least one speaker 30 among the multiple speakers 30 is adjusted using the sound adjustment parameters corresponding to the junction.

[0139] The reference sub-region is the sub-region with the shortest distance from the projection device 10 among the multiple sub-regions. The ratio of the sound pressure levels of the multiple speakers 30 in the sound adjustment parameters corresponding to the junction is equal to the ratio of the sound pressure levels of the multiple speakers 30 in the sound adjustment parameters of the reference sub-region, and the sound pressure levels of the multiple speakers 30 in the sound adjustment parameters corresponding to the junction are proportional to the distance between the junction and the projection device 30.

[0140] For example, referring to Table 1 and FIG. 9A, it is assumed that the target object is located at the junction of sub-area B and sub-area C, and the junction coincides with the central axis P of the detection area. In this case, the reference sub-area is sub-area A, and the sound adjustment parameter corresponding to the junction can be a sound pressure level of 40dB and a sound pressure level ratio of 50%. If the target object is located at the junction of sub-area H and sub-area I, and the junction of sub-area H and sub-area I also coincides with the central axis P of the detection area, then the reference sub-area is sub-area A, and the sound adjustment parameter corresponding to the junction can be a sound pressure level of 80dB and a sound pressure level ratio of 50%.

[0141] In the case where at least one target object is located at the junction of two sub-areas, the main board 100 is further configured as follows: if the junction does not coincide with the central axis of the detection area (i.e., the junction is separated from the central axis of the detection area), the sound adjustment parameters of the sub-area of ​​the two sub-areas that is closer to the projection device 10 and closer to the central axis of the detection area relative to other sub-areas are determined as the sound adjustment parameters corresponding to the junction, and the audio playback effect of at least one speaker 30 among the multiple speakers 30 is adjusted using the sound adjustment parameters corresponding to the junction.

[0142] For example, referring to Table 1 and FIG. 9A , the sound adjustment parameters corresponding to the junction of sub-region D and sub-region E, and the sound adjustment parameters corresponding to the junction of sub-region E and sub-region F may be respectively the same as the sound adjustment parameters of sub-region E. The sound adjustment parameters corresponding to the junction of sub-region G and sub-region H are the same as the sound adjustment parameters of sub-region H. The sound adjustment parameters corresponding to the junction of sub-region I and sub-region J are the same as the sound adjustment parameters of sub-region I.

[0143] It should be noted that, in some embodiments of the present disclosure, if at least one target object is respectively located in two sub-areas, and the two sub-areas are symmetrical with respect to the central axis of the detection area, the multimedia processing circuit 120 maintains the audio playback effect of at least one speaker 30 among the current multiple speakers 30. In other words, the multimedia processing circuit 120 does not adjust the current audio playback effect of at least one speaker 30 among the multiple speakers 30.

[0144] In step 1025 , the audio playing effect of at least one speaker 30 among the plurality of speakers 30 is controlled to remain unchanged. In other words, the multimedia processing circuit 120 does not adjust the audio playing effect of at least one speaker 30 among the plurality of speakers 30 .

[0145] When executing step 1021, if it is determined that any of the at least one target object is in motion, the multimedia processing circuit 120 may not adjust the audio playback effect of at least one of the multiple speakers 30. In other words, the multimedia processing circuit 120 may adjust the audio playback effect of at least one of the multiple speakers 30 only when the targets existing in the detection area of ​​the millimeter wave radar sensor are respectively in a stationary state.

[0146] It is understandable that if any target in the detection area is in motion, the position of the target changes in real time. If the audio playback effect of the speaker 30 is adjusted based on the real-time changing position, the frequency of adjusting the audio playback effect of the speaker 30 may be too high.

[0147] It should be noted that after step 1025 , if it is detected that any of the at least one target object is in a stationary state, the multimedia processing circuit 120 may execute steps 1022 to 103 .

[0148] Fig. 12 is another flow chart of the mainboard execution steps according to some embodiments. In some embodiments, as shown in Fig. 12, step 102 further includes step 1026.

[0149] In step 1026, it is determined whether the currently determined target sub-region is the same as the target sub-region determined last time. If so, step 1025 is executed; if not, step 103 is executed.

[0150] If the multimedia processing circuit 120 determines that the currently determined target sub-region is different from the target sub-region determined last time, step 103 may be executed; if the multimedia processing circuit 120 determines that the currently determined target sub-region is the same as the target sub-region determined last time, step 1025 may be executed. In this way, the projection device 10 can avoid repeatedly adjusting the audio playback effect of at least one speaker 30 among the multiple speakers 30.

[0151] In the projection system 1 provided in some embodiments of the present disclosure, the projection device 10 can determine the corresponding target sub-area from multiple sub-areas of the detection area according to the point cloud data of the at least one target object when the at least one target object is in a stationary state. In addition, the projection device 10 can adjust the audio playback effect of at least one speaker 30 among the multiple speakers 30 according to the sound adjustment parameter corresponding to the target sub-area, so that the playback effect of the speaker 30 heard by the at least one target object is roughly the same. In this way, the audio playback effect of the speaker 30 in the projection system 1 can be improved, and the flexible adjustment of the audio playback effect of the projection system 1 can be achieved.

[0152] The above mainly describes the example of not adjusting the audio playback effect of at least one speaker 30 among the multiple speakers 30 when any one of the at least one target object is in motion. Of course, in some embodiments, when any one of the at least one target object is in motion, the mainboard 100 may also adjust the audio playback effect of at least one speaker 30 among the multiple speakers 30.

[0153] Fig. 13 is another flow chart of the mainboard execution steps according to some embodiments. As shown in Fig. 13, step 102 includes steps 1121 to 1129.

[0154] In step 1121, based on the point cloud data of at least one target object, it is determined whether any target object among the at least one target object is in motion. If not, step 1122 is executed; if yes, step 1123 is executed.

[0155] Here, step 1121 of determining whether at least one target object is in motion is similar to the previous step 1021 and will not be repeated here.

[0156] In step 1122, a target sub-region corresponding to at least one target object in a plurality of sub-regions in the detection area is determined based on the point cloud data of the target object in a stationary state.

[0157] If the multimedia processing circuit 120 determines that the at least one target object is in a stationary state based on the point cloud data of the at least one target object, the target sub-region corresponding to the at least one target object can be directly determined based on the point cloud data of the target object in the stationary state.

[0158] Here, the specific content of how to determine the target sub-region in step 1122 is the same as the specific content of steps 1022 to 1024 above, and will not be repeated here.

[0159] In step 1123, a first motion trajectory of at least one target object in motion within a preset time period is determined based on the point cloud data.

[0160] If the multimedia processing circuit 120 determines that any of the at least one target object is in motion, the first motion trajectory of the target object within a preset time period can be determined based on the acquired point cloud data of each target object in motion. Here, the preset time period may include multiple detection moments. The first motion trajectory of the target object within the preset time period may include: a motion trajectory point at each detection moment among the multiple detection moments, and the motion trajectory point at each detection moment is used to indicate the position of the target object in the detection area at the detection moment.

[0161] The preset duration may be a fixed duration after the projection device 10 detects that any target object is in motion. The fixed duration may be pre-configured in the projection device 10 and may be flexibly adjusted according to application scenarios and requirements.

[0162] It should be noted that, since the point cloud of the target object includes multiple feature points of the target object (for example, head, hands and legs, etc.), in the first motion trajectory of each target object, the motion trajectory points at each detection moment may include multiple trajectory points corresponding to the multiple feature points of the target object. In addition, since at any detection moment within the preset time, the position of the target object in the detection area indicated by the multiple trajectory points and the moving speed of the target object are approximately the same, the multiple trajectory points can be approximated as one trajectory point as the motion trajectory point of the target object.

[0163] In step 1124, the first motion trajectory is smoothed to obtain a second motion trajectory of at least one target object within a preset time length.

[0164] After obtaining the first motion trajectory of at least one target object, the multimedia processing circuit 120 may use a trajectory smoothing algorithm to smooth the first motion trajectory, thereby obtaining a second motion trajectory of the at least one target object within a preset time length.

[0165] The point cloud data of the target object collected by the millimeter-wave radar sensor is mixed with point cloud data and noise data of non-target objects (such as movable household appliances), and the point cloud data and noise data of the non-target objects can also be called redundant data. Correspondingly, the first motion trajectory obtained according to the point cloud data of the target object contains the trajectory corresponding to the redundant data. The trajectory corresponding to the redundant data will interfere with the true motion trajectory of the target object, thereby affecting the accuracy of the judgment of the projection device 10. Therefore, the projection device 10 can filter out the trajectory points and trajectories corresponding to the redundant data in the first motion trajectory by smoothing the first motion trajectory, thereby obtaining the true motion trajectory of the target object (i.e., the second motion trajectory).

[0166] For example, the real motion trajectory of the target object during the motion process is relatively smooth, and the smoothness coefficient of the real motion trajectory is relatively high, while the trajectory corresponding to the redundant data is relatively messy (i.e., not smooth), and the smoothness coefficient corresponding to the trajectory is relatively low. Therefore, the projection device 10 can calculate the smoothness coefficients of all trajectories in the first motion trajectory, and determine the trajectory with a smoothness coefficient greater than a smoothness coefficient threshold as the real motion trajectory of the target object. Here, the smoothness coefficient threshold can be a preset fixed value, and the smoothness coefficient threshold can be greater than 0 and less than 1.

[0167] Of course, the mainboard 100 may also skip step 1124 to execute the following steps 1125 to 1129 using the first motion trajectory of the target object.

[0168] In step 1125 , it is determined whether the number of moving objects in the detection area is greater than 1. If not, step 1126 is executed; if yes, step 1127 is executed.

[0169] After determining that there is a moving target object and the corresponding motion trajectory of the target object in the detection area, if the multimedia processing circuit 120 determines that the number of moving targets in the detection area is 1, step 1126 can be executed; if it is determined that the number of moving targets in the detection area is greater than 1, there are multiple moving targets in the detection area, and the mainboard 100 can execute step 1127.

[0170] In step 1126 , a target sub-region is determined according to the second motion trajectory of the target object.

[0171] If it is determined that the number of moving targets in the detection area is 1, the multimedia processing circuit 120 can directly determine the target sub-area based on the second motion trajectory of the target. Here, the overlapping area between the target sub-area and the second motion trajectory of the target is greater than the overlapping area between the other sub-areas other than the target sub-area in the plurality of sub-areas and the second motion trajectory. In other words, the multimedia processing circuit 120 can determine the sub-area in the detection area where the target object appears more frequently during the motion process as the target sub-area corresponding to the second motion trajectory of the target.

[0172] FIG14 is a schematic diagram of a second motion trajectory of a target object in a detection area according to some embodiments. For example, referring to FIG14 (A), if there is a first target object in the detection area, and the second motion trajectory of the first target object passes through sub-area D and sub-area E. In this case, since the overlapping area between sub-area D and the second motion trajectory of the first target object is the largest, sub-area D can be determined as the target sub-area corresponding to the second motion trajectory of the first target object.

[0173] It should be noted that the size of the overlapping area between a sub-region and the second motion trajectory in the detection area is positively correlated with the frequency of the target appearing in the sub-region. The overlapping area between a sub-region and the second motion trajectory of any target can be represented by the length of the portion of the second motion trajectory of the target that is located in the sub-region.

[0174] In step 1127 , it is determined whether the second motion trajectories of the multiple targets have overlapping trajectories. If yes, step 1128 is executed; if no, step 1129 is executed.

[0175] After determining that there are multiple moving objects in the detection area, the multimedia processing circuit 120 can determine whether the second motion trajectories of the multiple objects have overlapping trajectories. If it is determined that the second motion trajectories of the multiple objects have overlapping trajectories, step 1128 can be executed; if it is determined that the second motion trajectories of the multiple objects do not have overlapping trajectories, step 1129 can be executed.

[0176] For example, for the second motion trajectories of any two targets among the multiple targets, if it is determined that the second motion trajectories of the any two targets have the same (i.e., overlapping) trajectory points, the multimedia processing circuit 120 can determine that the second motion trajectories of the any two targets have overlapping trajectories.

[0177] In step 1128 , a target sub-region is determined based on the overlapping tracks.

[0178] If it is determined that the second motion trajectories of the multiple targets have overlapping trajectories, the multimedia processing circuit 120 can determine the target sub-region corresponding to the second motion trajectories of the multiple targets from the multiple sub-regions of the detection area according to the overlapping trajectories. Here, the overlapping area between the target sub-region and the overlapping trajectory is greater than the overlapping area between the other sub-regions except the target sub-region among the multiple sub-regions and the overlapping trajectory.

[0179] It should be noted that the size of the overlapping area between a certain sub-region in the detection area and the overlapping trajectory is positively correlated with the frequency of the target object in the overlapping trajectory appearing in the sub-region. Therefore, the projection device 10 can determine the sub-region with the largest overlapping area with the overlapping trajectory in the detection area as the target sub-region. In other words, the target sub-region is the sub-region with the highest frequency of occurrence of the target objects corresponding to the overlapping trajectories in the multiple sub-regions. Here, the target sub-region can also be referred to as the active area of ​​the multiple targets. In addition, the overlapping area between a certain sub-region and the overlapping trajectory can also be characterized by the length of the portion of the overlapping trajectory located in the sub-region.

[0180] For example, referring to the diagram (B) in FIG. 14 , if there are a first target object and a second target object in the detection area, and the second motion trajectories of the first target object and the second target object pass through sub-area A, sub-area B, and sub-area C respectively. In this case, since the overlapping area of ​​sub-area A and the overlapping trajectory of the second motion trajectories of the two targets is greater than the overlapping area of ​​sub-area B and sub-area C with the overlapping trajectory, the projection device 10 can determine sub-area A as the target sub-area.

[0181] It should be noted that if the second motion trajectories of multiple targets have multiple overlapping trajectories, the multimedia processing circuit 120 can determine the target sub-region according to the fourth condition, the fifth condition and the sixth condition described below, which will not be repeated here.

[0182] In step 1129 , target sub-regions are determined according to the second motion trajectories of the multiple targets.

[0183] If it is determined that the second motion trajectories of the multiple targets do not have overlapping trajectories (i.e., the second motion trajectories of the multiple targets are separated from each other), a target sub-region may be determined based on the second motion trajectories of the multiple targets. Here, the target sub-region may satisfy at least one of the following conditions:

[0184] Fourth condition: the sum of the overlapping areas of the target sub-region and the second motion trajectories of the multiple targets is greater than the sum of the overlapping areas of the other sub-regions except the target sub-region among the multiple sub-regions and the second motion trajectories of the multiple targets. In other words, the sum of the overlapping areas of the target sub-region and the second motion trajectories of the multiple targets is the largest.

[0185] Fifth condition: the target sub-region is the sub-region including the largest number of second motion tracks of multiple targets among the multiple sub-regions.

[0186] Sixth condition: the sum of the distances between the target sub-region and the second motion trajectories of multiple targets is the smallest. Here, the distance between a sub-region and the second motion trajectory of any target may be the average of the distances between the center point of the sub-region and the multiple motion trajectory points included in the second motion trajectory.

[0187] According to the fourth condition, the projection device 10 can determine the overlapping areas of the multiple sub-regions in the detection area and the second motion trajectories of the multiple targets according to the sub-regions through which the second motion trajectories of the multiple targets pass. Afterwards, the projection device 10 can determine the sub-region with the largest sum of overlapping areas with the second motion trajectories of the multiple targets as the target sub-region.

[0188] According to the fifth condition, the projection device 10 can determine the number of second motion trajectories passed through each sub-area in the detection area according to the sub-areas passed by the second motion trajectories of the multiple targets. Afterwards, the projection device 10 can determine the sub-area with the largest number of second motion trajectories in the multiple sub-areas as the target sub-area.

[0189] According to the sixth condition, the projection device 10 may first determine the sum of the distances between each sub-region in the detection area and the second motion trajectories of the multiple targets. Afterwards, the projection device 10 may determine the sub-region with the smallest sum of the distances between the sub-regions and the second motion trajectories of the multiple targets as the target sub-region.

[0190] It is understandable that the projection device 10 may first select a third candidate sub-region that satisfies the fourth condition from multiple sub-regions, and if the number of the third candidate sub-regions is greater than 1, a target sub-region that satisfies at least one of the fifth condition or the sixth condition may be selected from the third candidate sub-region. Alternatively, the projection device 10 may first select a fourth candidate sub-region that satisfies the fifth condition from multiple sub-regions, and if the number of the fourth candidate sub-regions is greater than 1, a target sub-region that satisfies at least one of the fourth condition or the sixth condition may be selected from the fourth candidate sub-region. Alternatively, the projection device 10 may first select a fifth candidate sub-region that satisfies the sixth condition from multiple sub-regions, and if the number of the fifth candidate sub-regions is greater than 1, a target sub-region that satisfies at least one of the fourth condition or the fifth condition may be selected from the fifth candidate sub-region.

[0191] Of course, in addition to the above manner, the projection device 10 may also randomly select a sub-region from the sub-regions where the second motion trajectories of the multiple targets are located as the target sub-region.

[0192] FIG15 is another schematic diagram of the second motion trajectory of the target object in the detection area according to some embodiments. For example, referring to FIG15 (A), if the second motion trajectory of the first target object and the second target object passes through sub-area G and sub-area H respectively, and the sum of the overlapping areas of sub-area H and the second motion trajectory of the two targets is greater than the sum of the overlapping areas of sub-area G and the second motion trajectory of the two targets. Therefore, according to the fourth condition, the projection device 10 can determine sub-area H as the target sub-area.

[0193] Alternatively, referring to the diagram (B) in FIG15 , the second motion trajectory of the first target passes through sub-region H and sub-region I, and the second motion trajectory of the second target passes through sub-region I and sub-region J. Since sub-region I has the largest number of second motion trajectories of two targets, according to the fifth condition, the projection device 10 may determine sub-region I as the target sub-region.

[0194] Alternatively, referring to the diagram (C) in FIG15 , the second motion track of the first target passes through sub-area B and sub-area D, and the second motion track of the second target passes through sub-area E and sub-area F. Since the sum of the distances between sub-area E and the second motion tracks of the two targets is the smallest, according to the sixth condition, the projection device 10 can determine sub-area E as the target sub-area.

[0195] It should be noted that when at least one target object in motion is at the junction of two sub-areas in the detection area, the method for selecting the sound adjustment parameters corresponding to the junction can refer to the method for selecting the sound adjustment parameters corresponding to the junction when the target object in a stationary state is at the junction of two sub-areas, and will not be repeated here.

[0196] FIG16 is another flow chart of the mainboard execution steps according to some embodiments. In some embodiments, as shown in FIG16 , step 102 further includes step 1130 .

[0197] In step 1130 , it is determined whether the currently determined target sub-region is the same as the target sub-region determined last time. If so, step 1011 is executed; if not, step 103 is executed.

[0198] After determining the target sub-region corresponding to at least one target object, if the multimedia processing circuit 120 determines that the currently determined target sub-region is different from the target sub-region determined last time, step 103 may be executed; if the multimedia processing circuit 120 determines that the currently determined target sub-region is the same as the target sub-region determined last time, step 1011 may be returned to be executed. In this way, the projection device 10 can avoid repeatedly adjusting the audio playback effect of at least one speaker 30 among the multiple speakers 30.

[0199] In the projection system 1 provided in some embodiments of the present disclosure, when any one of the at least one target object is in motion, the projection device 10 can determine a target sub-area corresponding to the motion trajectory from multiple sub-areas of the detection area according to the motion trajectory of the at least one target object within a preset time length. In addition, the projection device 10 can adjust the audio playback effect of at least one speaker 30 among the multiple speakers 30 according to the sound adjustment parameters corresponding to the target sub-area, so that the playback effect of the speaker heard by the at least one target object during the motion process is roughly the same. In this way, the audio playback effect of the multiple speakers 30 in the projection system 1 can be improved, and the flexible adjustment of the audio playback effect of the projection system 1 can be achieved.

[0200] FIG. 17A is another flow chart of the motherboard execution steps according to some embodiments. FIG. 17B is another flow chart of the motherboard execution steps according to some embodiments. In some embodiments, as shown in FIG. 17A and FIG. 17B , the motherboard 100 is further configured to execute steps 104 to 107.

[0201] In step 104, it is determined whether the time duration during which the detection device 20 fails to detect the target object is greater than or equal to the first time duration. If yes, step 105 is executed; if no, the process returns to step 1011 for execution.

[0202] In step 105 , the projection device 10 is controlled to project prompt information onto the projection screen 40 .

[0203] When the detection device 20 does not send a data transmission request to the projection device 10 within the first time length, the multimedia processing circuit 120 can determine that the detection device 20 has not detected the target object within the first time length. In other words, the multimedia processing circuit 120 can determine that there is no target object in the detection area of ​​the detection device 20 within the first time length. In this case, the mainboard 100 can control the projection device 10 to project prompt information to the projection screen 40. The prompt information can indicate that the projection system 1 will turn off the light source 1500 (i.e., not display the projected image) after the second time length.

[0204] Of course, the mainboard 100 can also control at least one speaker 30 among the multiple speakers 30 to play the prompt information to ensure that the user can receive the prompt information in time.

[0205] In some embodiments, the first duration is smaller than the second duration. For example, the first duration is 3 seconds (s), and the second duration is 30s.

[0206] In step 106, it is determined whether the detection device 20 detects the target object in the detection area during the second time period when the projection screen 40 displays the prompt information. If yes, step 1011 is executed; if not, step 107 is executed.

[0207] During the process of the projection device 10 projecting the prompt information onto the projection screen 40, the multimedia processing circuit 120 can detect in real time whether there is a data transmission request from the detection device 20, so as to determine whether the detection device 20 detects a target object in the detection area. If it is determined that the detection device 20 detects at least one target object in the detection area during the second duration of the projection screen 40 displaying the prompt information, step 1011 can be executed and the display of the prompt information can be canceled; if it is determined that the duration of the projection screen 40 displaying the prompt information reaches the second duration, and it is determined that the detection device 20 does not detect a target object in the detection area during the second duration, step 107 can be executed.

[0208] In step 107, the light source 1500 is turned off.

[0209] If it is determined that the duration of the projection screen 40 displaying the prompt information reaches a second duration, and it is determined that the detection device 20 has not detected the target object in the detection area within the second duration, the light source 1500 in the light source assembly 150 can be turned off. In this way, the projection screen 40 can stop displaying the projected image, and the projection device 10 can enter the screen-off state to reduce the power consumption of the projection system 1 and save energy. When the projection device 10 is in the screen-off state, the light source assembly 150 stops working, while the detection device 20 is still in the working state. When the detection device 20 detects the presence of a target object in the detection area again, a data transmission request can be sent to the projection device 10 to instruct the projection device 10 to obtain the point cloud data of the target object and enter the working state from the screen-off state. Here, when the projection device 10 is in the screen-off state, the multiple speakers 30 also stop working.

[0210] It should be noted that, in some embodiments, the mainboard 100 may also skip step 105 and step 106 in Figures 17A and 17B. In other words, if the mainboard 100 determines that the time duration during which the detection device 20 does not detect the target object is greater than or equal to the first time duration, the mainboard 100 directly turns off the light source 1500.

[0211] FIG. 18A is another flow chart of the motherboard execution steps according to some embodiments. FIG. 18B is another flow chart of the motherboard execution steps according to some embodiments. In some embodiments, as shown in FIG. 18A and FIG. 18B, the motherboard 100 is further configured to execute steps 108 to 111.

[0212] In step 108, it is determined whether the duration for which the projection device 10 turns off the light source 1500 is greater than or equal to a third duration. If yes, step 109 is executed; if no, step 107 is continued.

[0213] In step 109 , the projection device 10 is controlled to enter a standby state.

[0214] When it is determined that the duration of the projection device 10 being in the screen-off state reaches a third duration, the multimedia processing circuit 120 can control the projection device 10 to enter the standby state. When the projection device 10 is in the standby state, the display control circuit 130, the light source driving circuit 140 and the optical modulation component 160 stop working respectively. In this way, the power consumption of the projection system 1 can be further reduced. For example, the third duration is 4 hours.

[0215] In step 110 , it is determined whether the detection device 20 detects a target object in the detection area. If yes, step 111 is executed; if no, step 109 is continued.

[0216] In step 111 , the projection device 10 is controlled to enter a power-on state.

[0217] When the projection device 10 is in the standby state, when the detection device 20 detects the existence of a target object in the detection area again, the infrared communication protocol can be used to send a power-on command to the infrared signal processing circuit 180. In response to the power-on command, the infrared signal processing circuit 180 sends an infrared coded signal to the multimedia processing circuit 120, and the multimedia processing circuit 120 controls the display control circuit 130, the light source driving circuit 140 and the optical modulation component 160 in response to the infrared coded signal to be in the working state, so that the projection device 10 can enter the power-on state from the standby state. After the projection device 10 is turned on, the projection device 10 can perform step 101. When the projection device 10 is in the power-on state, the various components in the projection device 10 work so that the projection light beam provided by the projection device 10 is sent to the projection screen 40 to display the projection image, and play the audio corresponding to the projection image.

[0218] It should be noted that some embodiments of the present disclosure are not limited to the order of steps described above, and those skilled in the art may change the order of steps described above according to actual needs, or may omit one or more of the steps described above, or may add one or more steps to the steps described above. For example, at least one of step 1021, step 1022, or step 1025 may be deleted as appropriate. Alternatively, at least one of step 1121 or step 1122 may be deleted as appropriate. Alternatively, step 1124 may be deleted as appropriate. Alternatively, steps 104 to 111 may be deleted as appropriate. Alternatively, steps 104 to 111 may be performed before step 103. Any method of variation that can be easily thought of by any technician familiar with the technical field disclosed in the present disclosure should be covered within the scope of protection of the present disclosure.

[0219] Some embodiments of the present disclosure also provide a control method for a projection system, which is applied to the projection system. For example, the method is applied to the above-mentioned projection system 1. Referring to FIG1 , the projection system 1 includes a projection device 10 and a projection screen 40. The projection device 10 includes a detection device 20 and a plurality of speakers 30, and each speaker 30 includes a plurality of channels.

[0220] The method includes: obtaining point cloud data obtained by the detection device 20 detecting at least one target object in the detection area; determining a target sub-area corresponding to the at least one target object in multiple sub-areas based on the point cloud data of the at least one target object; and adjusting the audio playback effect of at least one speaker 30 among the multiple speakers 30 using the sound adjustment parameters corresponding to the target sub-area.

[0221] In some embodiments, obtaining point cloud data obtained by the detection device 20 when detecting at least one target object in the detection area includes: receiving a data transmission request sent by the detection device 20; and obtaining point cloud data obtained by the detection device 20 when detecting at least one target object in the detection area according to the data transmission request.

[0222] In some embodiments, based on the point cloud data of at least one target object, a target sub-region corresponding to at least one target object in multiple sub-regions is determined, including: if it is determined based on the point cloud data of at least one target object that at least one target object is in a stationary state, and at least one target object is located in the same sub-region within the detection area, the sub-region where the at least one target object is located is determined as the target sub-region; if it is determined based on the point cloud data of at least one target object that at least one target object is in a stationary state, and there are multiple targets in the detection area located in at least two sub-regions within the detection area, the target sub-region is determined from the at least two sub-regions where the multiple targets are located; if it is determined based on the point cloud data of at least one target object that any one of the at least one target object is in motion, the audio playback effect of at least one speaker 30 among the multiple speakers 30 is controlled to remain unchanged.

[0223] In other embodiments, a target sub-region corresponding to at least one target object in multiple sub-regions is determined based on the point cloud data of at least one target object, including: if it is determined based on the point cloud data of at least one target object that at least one target object is in a stationary state, determining the target sub-region corresponding to the at least one target object in multiple sub-regions in the detection area based on the point cloud data of the stationary target object; if it is determined based on the point cloud data of at least one target object that any one of the at least one target object is in motion, determining the motion trajectory of at least one target object in motion within a preset time length based on the point cloud data; if the number of targets in motion in the detection area is equal to 1, determining the target sub-region based on the motion trajectory of the target; if the number of targets in motion in the detection area is greater than 1, and the motion trajectories of the multiple targets have overlapping trajectories, determining the target sub-region based on the overlapping trajectories; if the number of targets in motion in the detection area is greater than 1, and the motion trajectories of the multiple targets are separated from each other, determining the target sub-region based on the motion trajectories of the multiple targets.

[0224] In some embodiments, determining the motion trajectory of at least one target object in motion within a preset time length based on point cloud data includes: determining a first motion trajectory of at least one target object in motion within a preset time length based on the point cloud data; smoothing the first motion trajectory to obtain a second motion trajectory of the at least one target object within a preset time length.

[0225] In some embodiments, the method also includes: if the currently determined target sub-area is the same as the target sub-area determined last time, controlling the audio playback effect of at least one speaker 30 among the multiple speakers 30 to remain unchanged; if the currently determined target sub-area is different from the target sub-area determined last time, using the sound adjustment parameters corresponding to the target sub-area to adjust the audio playback effect of at least one speaker 30 among the multiple speakers 30.

[0226] In other embodiments, the method also includes: if the currently determined target sub-area is the same as the target sub-area determined last time, re-acquiring the point cloud data obtained by the detection device 20 detecting at least one target object in the detection area; if the currently determined target sub-area is different from the target sub-area determined last time, using the sound adjustment parameters corresponding to the target sub-area to adjust the audio playback effect of at least one speaker 30 among the multiple speakers 30.

[0227] In some embodiments, the projection device 10 further includes a light source assembly 150, and the light source assembly 150 includes a light source 1500. The method further includes: if the detection device 20 does not detect the target object for a time period greater than or equal to the first time period, turning off the light source 1500.

[0228] In some embodiments, the projection device 10 further includes a light source assembly 150, and the light source assembly 150 includes a light source 1500. The method further includes: if the detection device 20 does not detect the target object for a time period greater than or equal to the first time period, controlling the projection device 10 to project prompt information onto the projection screen 40; if the detection device 20 does not detect the target object in the detection area within the second time period when the projection screen 40 displays the prompt information, turning off the light source 1500.

[0229] In some embodiments, the method further includes: if the duration for which the projection device 10 turns off the light source 1500 is greater than or equal to a third duration, controlling the projection device 10 to enter a standby state; if the detection device 20 detects a target object in the detection area when the projection device 10 is in the standby state, controlling the projection device 10 to enter a power-on state.

[0230] It should be noted that the steps in the control method of the projection system and the steps executed by the mainboard 100 in the projection system 1 belong to the same concept. The specific contents of the multiple steps in the method can be found in the description of the relevant steps executed by the mainboard 100 above, which will not be repeated here.

[0231] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0232] Those skilled in the art will appreciate that the scope of the present disclosure is not limited to the above specific embodiments, and that certain elements of the embodiments may be modified and replaced without departing from the spirit of the present disclosure. The scope of the present disclosure is limited by the appended claims.

Claims

A projection system, comprising: a projection device configured to provide a projection beam; and a projection screen, configured to receive the projection light beam to form a projection image; wherein the projection device comprises: a shell; a detection device, configured to detect at least one target object in a detection area to obtain point cloud data; the detection area includes multiple sub-areas; multiple speakers, at least one of the multiple speakers includes multiple channels, and the multiple speakers are configured to play audio corresponding to the projection image; and a mainboard, electrically connected to the detection device, the mainboard is configured to: obtain point cloud data obtained by the detection device detecting at least one target object in the detection area; determine a target sub-area corresponding to the at least one target object in the multiple sub-areas according to the point cloud data of the at least one target object; and use a sound adjustment parameter corresponding to the target sub-area to adjust the audio playback effect of at least one of the multiple speakers; the sound adjustment parameter includes at least one of the sound pressure level of the at least one speaker or the sound pressure level ratio of the multiple channels included in the at least one speaker. The projection system according to claim 1, wherein: The main board is configured to: if it is determined according to the point cloud data of the at least one target object that the at least one target object is respectively in a stationary state, and the at least one target object is located in the same sub-area within the detection area, determine the sub-area where the at least one target object is located as the target sub-area; and if it is determined according to the point cloud data of the at least one target object that the at least one target object is respectively in a stationary state, and there are multiple targets in the detection area located in at least two sub-areas within the detection area, determine the target sub-area from the at least two sub-areas where the multiple targets are located; wherein the target sub-area satisfies at least one of the following: the target sub-area is a sub-area close to the projection system and close to the central axis of the detection area among the at least two sub-areas where the multiple targets are located; or the target sub-area is a sub-area containing the largest number of the targets among the at least two sub-areas where the multiple targets are located; or the target sub-area is a sub-area where the center points of the at least two sub-areas where the multiple targets are located are located. The projection system according to claim 1 or 2, wherein: The mainboard is configured to: if it is determined according to the point cloud data of the at least one target object that any target object among the at least one target object is in motion, control the audio playback effect of at least one speaker among the multiple speakers to remain unchanged. The projection system according to any one of claims 1 to 3, wherein: The main board is further configured to: if the currently determined target sub-area is the same as the last determined target sub-area, control the audio playback effect of at least one of the plurality of speakers to remain unchanged; If the currently determined target sub-region is different from the last determined target sub-region, the sound adjustment parameter corresponding to the target sub-region is used to adjust the audio playback effect of at least one of the multiple speakers. The projection system according to claim 1 or 2, wherein: The main board is configured to: if it is determined according to the point cloud data of the at least one target object that any target object among the at least one target object is in motion, determine the motion trajectory of the at least one target object within a preset time period according to the point cloud data; And determining a target sub-region corresponding to the motion trajectory from the multiple sub-regions. The projection system according to claim 5, wherein: The main board is configured as follows: if the number of targets in motion within the detection area is equal to 1, the target sub-area is determined according to the motion trajectory of the target; the overlapping area between the target sub-area and the motion trajectory of the target is greater than the overlapping area between the other sub-areas other than the target sub-area among the multiple sub-areas and the motion trajectory; if the number of targets in motion within the detection area is greater than 1, and the motion trajectories of the multiple targets have overlapping trajectories, the target sub-area is determined according to the overlapping trajectories; the overlapping area between the target sub-area and the overlapping trajectory is greater than the overlapping area between the other sub-areas other than the target sub-area among the multiple sub-areas and the overlapping trajectory; if the number of targets in motion within the detection area is greater than 1, and the motion trajectories of the multiple targets are separated from each other, the target sub-area is determined according to the motion trajectories of the multiple targets; the target sub-area satisfies at least one of the following: the sum of the overlapping areas between the target sub-area and the motion trajectories of the multiple targets is the largest; or the target sub-area is the sub-area that includes the largest number of motion trajectories of the multiple targets among the multiple sub-areas; or the sum of the distances between the target sub-area and the motion trajectories of the multiple targets is the smallest. The projection system according to claim 5 or 6, wherein: The main board is configured to: determine a first motion trajectory of the at least one target object in motion within the preset time length according to the point cloud data; and smooth the first motion trajectory to obtain a second motion trajectory of the at least one target object within the preset time length. The projection system according to any one of claims 1, 2, 5, 6, or 7, wherein: The main board is further configured to: if the currently determined target sub-region is the same as the last determined target sub-region, re-acquire point cloud data obtained by the detection device detecting the at least one target object in the detection region; If the currently determined target sub-region is different from the last determined target sub-region, the sound adjustment parameter corresponding to the target sub-region is used to adjust the audio playback effect of at least one of the multiple speakers. The projection system according to any one of claims 1 to 8, wherein: The projection device further includes a light source, and the main board is further configured to: turn off the light source if it is determined that the detection device has not detected the target object in the detection area within a first time period. The projection system according to any one of claims 1 to 8, wherein: The projection device further includes a light source, and the main board is further configured to: if the detection device fails to detect the target object for a period greater than or equal to a first period, control the projection device to project prompt information onto the projection screen; And if the detection device does not detect the target object in the detection area within the second time period during which the prompt information is displayed on the projection screen, the light source is turned off. The projection system according to claim 9 or 10, wherein: The mainboard includes a multimedia processing circuit, which is electrically connected to the detection device and configured to receive a video signal and process the video signal; The projection device further includes: a display control circuit electrically connected to the multimedia processing circuit, the display control circuit being configured to send a light source driving signal according to the video signal, process the video signal received from the multimedia processing circuit, and output the processed video signal; a light source driving circuit electrically connected to the display control circuit, the light source driving circuit being configured to receive the light source driving signal and output a driving current according to the light source driving signal; a light source assembly including the light source, the light source assembly being configured to send an illumination beam under the drive of the light source driving circuit; and an optical modulation assembly being configured to modulate the illumination beam sent by the light source assembly according to the video signal processed by the display control circuit to obtain the projection beam; the main board is further configured to: control the projection device to enter a standby state if the duration of the light source being turned off by the projection device is greater than or equal to a third duration; in the standby state, the display control circuit, the light source driving circuit and the optical modulation assembly stop working; and control the projection device to enter a power-on state if the detection device detects the target object in the detection area when the projection device is in the standby state. The projection system according to any one of claims 1 to 11, wherein: The main board is further configured to: when the at least one target object is respectively located at the junction of the two sub-areas, if the junction does not coincide with the central axis of the detection area, determine the sound adjustment parameter of the sub-area of ​​the two sub-areas close to the projection device and close to the central axis of the detection area as the sound adjustment parameter corresponding to the junction, and adjust the audio playback effect of at least one speaker of the multiple speakers with the sound adjustment parameter corresponding to the junction; If the junction coincides with the central axis of the detection area, the sound adjustment parameters corresponding to the junction are determined according to the distance between the junction and the projection device and the sound adjustment parameters of the reference sub-area, and the audio playback effect of at least one of the multiple speakers is adjusted using the sound adjustment parameters corresponding to the junction; wherein the reference sub-area is the sub-area with the shortest distance from the projection device among the multiple sub-areas, the ratio of the sound pressure levels of the multiple speakers in the sound adjustment parameters corresponding to the junction is equal to the ratio of the sound pressure levels of the multiple speakers in the sound adjustment parameters of the reference sub-area, and the sound pressure levels of the multiple speakers in the sound adjustment parameters corresponding to the junction are proportional to the distance between the junction and the projection device. The projection system according to any one of claims 1 to 12, wherein: The mainboard is configured to: receive a data transmission request sent by the detection device; and obtain point cloud data obtained by the detection device detecting at least one target object in the detection area according to the data transmission request. The projection system according to any one of claims 1 to 13, wherein: The detection area is fan-shaped, and the multiple sub-areas are arranged along at least one of the radial direction or the circumferential direction of the fan. A control method for a projection system, wherein: The projection system comprises: a projection device configured to provide a projection beam; and a projection screen configured to receive the projection beam to form a projection image; wherein the projection device comprises: a housing; a detection device configured to detect at least one target object in a detection area to obtain point cloud data; the detection area comprises a plurality of sub-areas; and a plurality of speakers, at least one of the plurality of speakers comprises a plurality of channels, and the plurality of speakers are configured to play audio corresponding to the projection image; the method comprises: acquiring point cloud data obtained by the detection device detecting at least one target object in the detection area; determining a target sub-area corresponding to the at least one target object in the plurality of sub-areas according to the point cloud data of the at least one target object; and adjusting the audio playback effect of at least one of the plurality of speakers by using a sound adjustment parameter corresponding to the target sub-area; the sound adjustment parameter comprises at least one of the sound pressure level of the at least one speaker or the sound pressure level ratio of the plurality of channels included in the at least one speaker. The method according to claim 15, wherein The determining, according to the point cloud data of the at least one target, a target sub-region corresponding to the at least one target in the multiple sub-regions includes: if it is determined according to the point cloud data of the at least one target that the at least one target is in a stationary state, and the at least one target is located in the same sub-region in the detection region, determining the sub-region where the at least one target is located as the target sub-region; and if it is determined according to the point cloud data of the at least one target that the at least one target is in a stationary state, and there are multiple targets in the detection region located in at least two sub-regions in the detection region, determining the target sub-region from the at least two sub-regions where the multiple targets are located; wherein the target sub-region satisfies at least one of the following: the target sub-region is a sub-region that is closest to the projection system and closest to the central axis of the detection region among the at least two sub-regions where the multiple targets are located; or the target sub-region is a sub-region that contains the largest number of the targets among the at least two sub-regions where the multiple targets are located; or the target sub-region is a sub-region where the center points of the at least two sub-regions where the multiple targets are located are located. The method according to claim 15 or 16, wherein The method of determining a target sub-region corresponding to the at least one target object among the multiple sub-regions based on the point cloud data of the at least one target object includes: if it is determined based on the point cloud data of the at least one target object that any one of the at least one target object is in motion, determining a motion trajectory of the at least one target object within a preset time length based on the point cloud data; and determining a target sub-region corresponding to the motion trajectory from the multiple sub-regions. The method according to claim 17, wherein The determining of the target sub-region corresponding to the motion trajectory from the multiple sub-regions includes: if the number of the moving objects in the detection area is equal to 1, determining the target sub-region according to the motion trajectory of the object; the overlapping area between the target sub-region and the motion trajectory of the object is greater than the overlapping area between the other sub-regions other than the target sub-region and the motion trajectory of the multiple sub-regions; if the number of the moving objects in the detection area is greater than 1, and the motion trajectories of the multiple objects have overlapping trajectories, determining the target sub-region according to the overlapping trajectories; the overlapping area between the target sub-region and the overlapping trajectory is greater than the overlapping area between the other sub-regions other than the target sub-region and the overlapping trajectory of the multiple sub-regions; if the number of the moving objects in the detection area is greater than 1, and the motion trajectories of the multiple objects are separated from each other, determining the target sub-region according to the motion trajectories of the multiple objects; the target sub-region satisfies at least one of the following: the sum of the overlapping areas between the target sub-region and the motion trajectories of the multiple objects is the largest; or the target sub-region is the sub-region including the largest number of motion trajectories of the multiple objects; or the sum of the distances between the target sub-region and the motion trajectories of the multiple objects is the smallest. The method according to claim 17 or 18, wherein The method of determining the motion trajectory of the at least one target object within the preset time length according to the point cloud data includes: if it is determined according to the point cloud data of the at least one target object that any one of the at least one target object is in motion, determining a first motion trajectory of the at least one target object in motion within the preset time length according to the point cloud data; and smoothing the first motion trajectory to obtain a second motion trajectory of the at least one target object within the preset time length. The method according to any one of claims 15 to 19, wherein The step of acquiring point cloud data obtained by the detection device through detecting at least one target object within the detection area comprises: receiving a data transmission request sent by the detection device; and acquiring point cloud data obtained by the detection device through detecting at least one target object within the detection area according to the data transmission request.

Images