Laser projection device

Abstract

The present application discloses a laser projection device, comprising: a blue laser, a red laser, a green laser, a laser driving circuit corresponding to each color laser, a light modulation device, a display panel and a signal shaping circuit; the display panel is configured to generate a modulation driving signal for driving the light modulation device and generate a driving signal for driving each color laser to emit light, the driving signal including an initial image enable signal and an initial current control signal; the signal shaping circuit is connected to the display panel and is disposed in the path where both or any one of the initial image enable signal and the initial current control signal is transmitted to at least one color laser, and is configured to output a shaping signal; the shaping signal is superimposed on the above two signals or any one of them to form a target driving signal; the laser driving circuit is configured to receive the target driving signal and directly drive the corresponding color laser to emit light or go out, and the target driving signal is a high-frequency periodic driving signal. When the above laser projection device performs projection display, the speckle phenomenon can be weakened or suppressed.

Description

[0001] This application is a divisional application based on Chinese Invention Application No. 202010495287.5 (filed on June 3, 2020), with the invention title: Laser Projection Device and Laser Driver Control Method. Technical Field

[0002] This application relates to the field of projection display, and particularly to a laser projection device and a laser driver control method. Background Art

[0003] Currently, a projection device may include a light source. After the laser emitted by the light source is projected onto a projection screen, an image can be projected onto the projection screen.

[0004] However, due to the high coherence of the laser, the laser emitted by the projection device forms bright and dark spots, also known as speckles, on the projection screen, thus seriously affecting the display effect of the image. Summary of the Invention

[0005] Embodiments of this application provide a laser projection device that can weaken or suppress the speckle phenomenon in a laser projection display image. The technical solutions are as follows:

[0006] A laser projection device includes: a display control processing unit, a signal shaping circuit, a laser driver circuit, a laser, and a light modulation device; wherein, the display control processing unit is configured to output an image display drive signal to the light modulation device, and is further configured to output an initial image enable signal and an initial current control signal to the laser driver circuit to drive the laser to emit light or extinguish; the signal shaping circuit is disposed in the path where the initial image enable signal and the initial current control signal are transmitted to the laser, and is configured to output a shaping signal, and the shaping signal is superimposed on one or both of the above two signals to form a target drive signal; the laser is configured to emit light or extinguish under the drive of the target drive signal, and the target drive signal is a high-frequency periodic drive signal.

[0007] In the above technical solution, a signal shaping circuit is added to the path where the projection display control processing unit outputs a drive signal to the laser, and the drive signal to be received by the laser is shaped, so that the change period of the drive current finally acting on the laser is shortened and the frequency is increased. Moreover, within one period, the high-level value of the drive signal can turn on the laser, and the low-level value is not greater than the threshold current of the laser, forming a drive signal that can frequently control the on and off of the laser, affecting the normal steady-state light-emitting process of the laser, thereby reducing the coherence of the laser beam and being able to eliminate or suppress the speckle phenomenon during projection display.

[0008] In addition, a laser driving control method is provided. Moreover, a laser driving control method is provided and applied to a laser projection device. The method includes: the display control processing unit outputs an initial driving signal; the initial driving signal is shaped to obtain a target driving signal; and the target driving signal is transmitted to the corresponding laser.

[0009] In the above laser driving control method, similarly, by shaping the driving signal to be received by the laser, the change period of the driving current finally acting on the laser is shortened, the frequency is increased, and within one period, the high-level voltage of the driving signal can turn on the laser, and the low-level voltage is not greater than the threshold current of the laser, forming a driving signal capable of frequently controlling the on and off of the laser, thereby reducing the coherence of the laser beam and being able to eliminate or suppress the speckle phenomenon during projection display. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0011] Figure 1-1 is a schematic structural diagram of a laser projection device provided by an embodiment of the present application;

[0012] Figure 1-2 is a schematic diagram of the circuit system framework of a laser projection device provided by an embodiment of the present application;

[0013] Figure 2-1 is a schematic diagram of the circuit system framework of a three-color laser projection device provided by an embodiment of the present application;

[0014] Figure 2-2 is a schematic diagram of a partial circuit structure of another laser projection device provided by an embodiment of the present application;

[0015] Figure 2-3 is a schematic diagram of a partial circuit structure of yet another laser projection device provided by an embodiment of the present application;

[0016] Figure 3-1 is a schematic diagram of a shaping signal provided by an embodiment of the present application;

[0017] Figure 3-2 is a schematic diagram of another shaping signal provided by an embodiment of the present application;

[0018] Figure 3-3 is a schematic diagram of yet another shaping signal provided by an embodiment of the present application;

[0019] Figure 4-1 It is a schematic timing diagram corresponding to a signal provided by an embodiment of the present application;

[0020] Figure 4-2 It is a schematic timing diagram of primary color light in a laser projection device provided by an embodiment of the present application;

[0021] Figure 5 It is a schematic diagram of a partial circuit structure of a laser projection device provided by an embodiment of the present application;

[0022] Figure 6 It is a schematic diagram of a partial circuit structure of another laser projection device provided by an embodiment of the present application;

[0023] Figure 7 It is a schematic diagram of a partial circuit structure of yet another laser projection device provided by an embodiment of the present application;

[0024] Figure 8 It is a schematic diagram of another method for shaping an initial image enable signal to obtain a target enable signal provided by an embodiment of the present application;

[0025] Figure 9 It is a schematic diagram of another method for shaping an initial current control signal to obtain a target current control signal provided by an embodiment of the present application;

[0026] Figure 10 It is a schematic diagram of a partial circuit structure of yet another laser projection device provided by an embodiment of the present application;

[0027] Figure 11 It is a schematic diagram of another method for shaping an initial image enable signal to obtain a target enable signal provided by an embodiment of the present application;

[0028] Figure 12 It is a schematic diagram of a partial circuit structure of yet another laser projection device provided by an embodiment of the present application;

[0029] Figure 13 It is a schematic waveform diagram of the enable signal of a laser and the drive current of the laser provided by an embodiment of the present application;

[0030] Figure 14 It is a schematic diagram of the structure of a laser emission chip in the related art;

[0031] Figure 15 It is a flowchart of a laser drive control method provided by an embodiment of the present application. Detailed implementation manners

[0032] To make the objectives, technical solutions, and advantages of the present application clearer, the following will further describe the embodiments of the present application in detail with reference to the accompanying drawings.

[0033] Figure 1-1 This is a schematic diagram of a laser projection device provided by an embodiment of the present application. As Figure 1-1 shown, after disassembling the upper housing of the laser projection device, the internal structure can be divided according to optical functions, and can include a light source 100, an optical engine 200, and a lens 300. Among them, the light source 100 is used to provide a light source illumination beam, which is transmitted to the rear-end light modulation device and the projection lens. The light source 100 can include at least one color laser, such as a blue laser, or a dual-color laser, such as a blue laser and a red laser. Or, it can also be a three-color laser light source, including lasers of three colors: red, green, and blue, for providing a three-color laser illumination beam.

[0034] The laser beam provided by the light source 100 is incident on the illumination optical path part in the optical engine 200 after being combined and shaped. In the DLP projection architecture, the DMD chip is the core light modulation device. The DMD chip receives the drive control signal corresponding to the image signal, flips the thousands of tiny mirrors on its surface to positive or negative angles corresponding to the drive signal, and reflects the beam irradiating its surface into the lens 300.

[0035] The lens 300 can be an ultra-short throw projection lens, and the ultra-short throw projection lens 300 is used to project the image beam onto the projection screen, thereby realizing the projection image display. The laser projection device in the above example can be an ultra-short throw laser projection device.

[0036] Based on the above Figure 1-1 structure of the laser projection device in the example, Figure 1-2 a schematic diagram of the circuit architecture of a laser projection device in an embodiment is shown.

[0037] As Figure 1-2 shown, the laser projection device includes: a display board 001, a power board 002, and a TV board 003. Among them, the power board 02 is respectively connected to the display board 001 and the TV board 003, and can be used to supply power to each device or part module on the display board 001 and the TV board 003. At the same time, it can also supply power to other functional modules in the laser projection device, such as the human eye protection module, the fan, the WIFI module, etc., to ensure the normal power supply of each part of the laser projection device. In some specific implementations, a laser driver circuit can also be provided on the power board 002. Or, the laser driver circuit can also be provided independently of the power board 002.

[0038] The TV board 003 is mainly used for external audio-visual signals and decoding.

[0039] The TV board 003 is provided with a System on Chip (SoC), which can decode data in different data formats into a normalized format and transmit the data in the normalized format to the display board 001 through, for example, a connector.

[0040] Among them, the video image signal output by the TV board 003 is transmitted to the display board 001.

[0041] The display board 001 can be provided with a Field Programmable Gate Array (FPGA). The algorithm processing module FPGA is used to process the input video image signal, such as performing MEMC frequency doubling processing, or image correction, etc., to implement the image enhancement function. The projection display control processing unit 010 is connected to the algorithm processing module FPGA and is used to receive the processed video image processing signal data as the image data to be displayed. It should be noted that the FPGA usually exists as an enhancement function module. In some low-cost solutions, this module part can also be not set, but the projection display control processing unit 010 is used to receive the video image display signal output by the TV board 003.

[0042] The projection display control processing unit 010 mainly includes a Digital Light Processing (DLP) chip and may also include a driver chip.

[0043] In the DLP control architecture, the light source part needs to cooperate with the working timings of the DLP chip and the DMD chip. Specifically, the DLP chip outputs an image enable signal, which can also be called a primary color light enable signal, usually denoted as X_EN, where X is the abbreviation of different primary color lights, and at the same time, it also outputs a brightness adjustment signal, simply referred to as a PWM signal. Along with the sequential modulation process of different primary color image components by the DMD chip, the light source part needs to synchronously output the primary color light beams of the corresponding colors. That is, the DLP chip outputs the primary color light enable signal to notify the laser light source to enable the lighting of a certain color laser, and outputs the PWM signal to notify a certain laser in the laser light source to light up with what brightness.

[0044] Corresponding to Figure 1-2As shown, the projection display control processing unit 010 is used to generate a modulation drive signal for driving the light modulation device 011 based on the image signal to be displayed. On the other hand, due to the display of the projection image, the synchronization and cooperation of the light source beam and the light modulation device are required. The projection display control processing unit 010 also generates a drive signal for driving the light source to emit light. This drive signal can be called an initial drive signal and includes two specific drive signals: an image enable signal EN and a current PWM signal. Among them, the image enable signal EN is a timing control signal used to coordinate the timing of different color light outputs, and the current PWM signal is a square wave signal used to provide a current signal for the laser to light up.

[0045] And, Figure 1-2 In the schematic diagram of the laser projection device circuit architecture shown, there is also a laser driver circuit 030, which is used to receive the image enable signal EN and the current PWM signal output by the projection display control processing unit 010 and specifically control the lighting of the laser 040.

[0046] In the figure, the laser 040 can be a laser of one color or a laser of multiple colors. Generally, a corresponding laser driver circuit 030 is provided for each color laser.

[0047] And, in the schematic diagram of the hardware circuit framework of the laser projection device in this example, there is also a signal shaping current 020, which can be used to generate a periodic sub-signal to shape the image enable signal EN or the current PWM signal, affecting the signal waveform and period finally output to the laser 040.

[0048] It should be noted that in the figure, the signal shaping circuit 020 is connected to the display board 001, only to indicate that the signal shaping circuit 020 has an impact on the output signal of the display board 001. In actual applications, the signal shaping circuit 020 can be set on the display board 001 and can be specifically connected to the projection display control processing unit 010, acting on the image enable signal EN and the current PWM signal output from the projection display control processing unit 010, either both signals or any one of them. The signal shaping circuit 020 can also be set in the projection display control processing unit 010. At this time, the signal shaping circuit 020 can be used as a sub-circuit module of the projection display control processing unit 010.

[0049] Alternatively, the signal shaping circuit 020 can be disposed on the laser driver circuit 030. That is, the signal shaping circuit 020 serves as a sub-circuit module of the laser driver circuit 030. Or, when the laser driver circuit is disposed on the power supply board 002, the signal shaping circuit 020 can also be disposed on the power supply board 002. In this way, when the image enable signal EN and the current PWM signal are output to the laser driver circuit 030, the signal shaping circuit 020 shapes one or both of the above two signals, at least changing the waveform period of the original signal, thereby affecting the drive signal finally transmitted to the laser 040.

[0050] Alternatively, the signal shaping circuit 020 can also be disposed as an independent module between the circuits of the laser driver circuit 030 and the display board 001. The signal shaping circuit 020 can receive one or both of the image enable signal EN and the current PWM signal, reshape the waveform period, and then output it to the laser driver circuit 030. After some conversion and amplification processing of the laser driver circuit 030, it is finally output to the laser 040 to control the lighting of the laser device.

[0051] The signal shaping circuit 020 may include a high-frequency signal generator.

[0052] In one example, the laser projection device can be a three-color laser projection device, including lasers of three colors: red, green, and blue. Figure 2-1 Fig. shows a schematic circuit structure diagram of a three-color laser projection device. As Figure 2-1 shown, corresponding to Figure 1-2 the projection display control processing unit 010 in Figure 2-1 is shown as the DLP main control processing unit 010a and the DLP slave control processing unit 010b in

[0053] And, in Figure 2-1 the example shown, the DLP main control processing unit 010a outputs an image enable signal EN and a current PWM signal for driving the laser. And, in this example, the signal shaping circuit 020 is disposed in the signal path between the laser driver circuit 030 and the DLP main control processing unit 010a, and is specifically used to shape the image enable signal EN and output the shaped graphic enable signal EN to the laser driver circuit 030.

[0054] And, in Figure 2-1In the example, the laser 040 includes a blue laser 401, a red laser 402, and a green laser 403. The signal shaping circuit 020 can be used to shape only the image enable signal EN of one color laser, or can be used for the graphic enable signals EN of two or three color lasers.

[0055] Moreover, the power supply board 002 can provide a driving current of 2.9 amperes (A) for the red laser, a driving current of 2 A for the green laser, and a driving current of 3 A for the blue laser.

[0056] As Figure 2-2 shown in the schematic diagram of the laser projection device circuit, the laser 040 can include: three groups of lasers of different colors, namely a blue laser 401 that emits blue laser, a red laser 402 that emits red laser, and a green laser 403 that emits green laser. Each of the above lasers can be a multi-packaged chip laser (Multi chiped Laser, MCL).

[0057] The above three-color lasers can be light-emitting units with independent packages, such as three groups of MCL type lasers, or multiple-color chips can be packaged in one light-emitting unit, such as a MCL type laser with multiple rows of light-emitting chips of different colors. The above different light-emitting units can all output three-color laser.

[0058] Exemplarily, in Figure 2-2 , the display control processing unit 010 can output a blue PWM signal B_PWM corresponding to the blue laser 401 based on the blue primary color component of the image to be displayed, output a red PWM signal R_PWM corresponding to the red laser 402 based on the red primary color component of the image to be displayed, and output a green PWM signal G_PWM corresponding to the green laser 403 based on the green primary color component of the image to be displayed.

[0059] The display control processing unit 010 can output an initial image enable signal B_EN0 corresponding to the blue laser 401 based on the lighting duration of the blue laser 401 within the driving cycle, output an initial image enable signal R_EN0 corresponding to the red laser 402 based on the lighting duration of the red laser 402 within the driving cycle, and output an initial image enable signal G_EN0 corresponding to the green laser 403 based on the lighting duration of the green laser 403 within the driving cycle.

[0060] The signal shaping circuit 020 is arranged between the laser driving circuit 030 corresponding to the red laser and the display control processing unit 010, and is used to shape the image enable signal EN corresponding to the red laser or the red primary color light enable signal R_EN0.

[0061] In Figure 2-2 the schematic diagram, it is shown that the display control processing unit 010 can transmit the initial image enable signal B_EN0 corresponding to the blue laser 401 to the corresponding laser driver circuit 030, transmit the initial image enable signal R_EN0 corresponding to the red laser 402 to the corresponding signal shaping circuit 020, and output the initial image enable signal G_EN0 corresponding to the green laser 403 to the corresponding laser driver circuit 030.

[0062] Moreover, the display control processing unit 010 can also transmit the blue PWM signal B_PWM to the laser driver circuit 030 corresponding to the blue laser 401, transmit the red PWM signal R_PWM to the laser driver circuit 030 corresponding to the red laser 402, and transmit the green PWM signal G_PWM to the laser driver circuit 030 corresponding to the green laser 403.

[0063] In Figure 2-2 the schematic diagram, the display control processing unit 010 transmits an initial image enable signal to the corresponding signal shaping circuit 020 and transmits an initial current control signal to the corresponding laser driver circuit 030. Also, as Figure 2-2 a variant of the schematic diagram, the display control processing unit 010 can also transmit two or three initial image enable signals to the signal shaping circuit 020 and transmit three sets of initial current control signals to the corresponding laser driver circuits 030.

[0064] Moreover, exemplarily, the signal shaping circuit 020 can also be arranged in the signal path of the current PWM signal. As Figure 2-3 shown, the signal shaping circuits 020 are respectively arranged in the PWM signal transmission paths corresponding to the blue laser 401, the red laser 402, and the green laser 403.

[0065] As Figure 2-3As shown, the display control processing unit 010 is respectively connected to each signal shaping circuit 020 and each laser driver circuit 030, and is used to output at least one initial image enable signal corresponding to each of the three primary colors of each frame of the multi-frame display image. Specifically, as shown in the figure, the blue primary color light enable signal B_EN, the red primary color light enable signal R_EN, and the green primary color light enable signal G_EN. In addition, it is also used to output three groups of initial current control signals corresponding to the three primary colors of each frame of the image. For example, the initial current control signal can be a pulse width modulation (PWM) signal. Specifically, it can be the blue PWM signal B_PWM0, the red PWM signal R_PWM0, and the green PWM signal G_PWM0 as shown in the figure. In addition, the display control processing unit 010 is further used to transmit the three-way initial current control signals to the corresponding signal shaping circuits 020 respectively, and transmit the three groups of initial image enable signals to the corresponding laser driver circuits 030 respectively.

[0066] The display control processing unit 010 can also output the initial image enable signal B_EN corresponding to the blue laser 401 based on the lighting duration of the blue laser 401 during the driving period, output the initial image enable signal R_EN corresponding to the red laser 402 based on the lighting duration of the red laser 402 during the driving period, and output the initial image enable signal G_EN corresponding to the green laser 403 based on the lighting duration of the green laser 403 during the driving period.

[0067] The display control processing unit 010 can transmit the initial image enable signal B_EN to the laser driver circuit 030 corresponding to the blue laser 401, transmit the initial image enable signal R_EN to the laser driver circuit 030 corresponding to the red laser 402, and output the initial image enable signal G_EN to the laser driver circuit 030 corresponding to the green laser 403. In addition, the display control processing unit 010 can also transmit the blue PWM signal B_PWM0 corresponding to the blue laser 401 to the corresponding signal shaping circuit 020, transmit the red PWM signal R_PWM0 corresponding to the red laser 402 to the corresponding signal shaping circuit 020, and transmit the green PWM signal G_PWM0 corresponding to the green laser 403 to the corresponding signal shaping circuit 020.

[0068] Each signal shaping circuit 020 is used to shape the received initial signal to obtain a target signal and transmit the target signal to the corresponding laser driver circuit 030.

[0069] Among them, the frequency of the target signal is greater than the frequency of the initial image enable signal, and within one period of the initial image enable signal, the total duration of the target signal at the valid level is less than the duration of the initial signal at the valid level.

[0070] If the initial signal received by the signal shaping circuit 020 is the initial image enable signal, it can thus achieve continuously controlling the laser driver circuit 030 to turn on or off within one period of the initial image enable signal, and further enabling the drive current provided by the laser driver circuit 030 to the laser to switch between the valid level and the invalid level at a relatively high frequency. Among them, the valid level can be the high level.

[0071] If the initial signal received by the signal shaping circuit 020 is the initial current control signal, it can thus achieve changing the change period of the drive current provided by the laser driver circuit 030 to the laser within one period of the initial image enable signal.

[0072] Each laser driver circuit 030 is used to transmit the drive current to the corresponding laser in response to the target signal and another initial signal. Each laser is used to emit light under the drive of this drive current.

[0073] Specifically, the signal shaping circuit 020 superimposes a high-frequency, periodic waveform on the initial signal to form the target signal.

[0074] Figure 3-1 , Figure 3-2 , Figure 3-3 Examples of different shaping signals S_f are respectively given.

[0075] Such as Figure 3-1 shown, the signal S_f can be a square wave pulse waveform. Figure 3-2 In the schematic diagram, the signal S_f can be a triangular pulse waveform. And, Figure 3-3 In the schematic diagram, the signal S_f can be a sawtooth pulse waveform.

[0076] Combined with Figure 2-2 the schematic diagram of the hardware circuit structure, Figure 4-1 shows the lighting working timing diagram of the red laser.

[0077] First of all, for a better understanding of the multi-primary color periodic timing change, reference can be made to Figure 4-2 the timing working diagram of the three primary colors of light in the laser projection device shown. Such as Figure 4-2 shown, for the enable signals R_EN0, G_EN0, B_EN0 corresponding to the three primary colors of light, within one drive period T0, only one of the three enable signals is at the high-level valid period at a certain moment, and the other two signals are at the low-level invalid period.

[0078] Also, usually to increase the screen brightness, in a driving period T, the enable signals corresponding to the three colors can be set to be valid simultaneously, that is, the W period shown in the figure. This W period can also not be set, and only the three colors are alternately valid for timing control.

[0079] R, G, and B respectively refer to the duration when the red enable signal is at the valid potential, the duration when the green enable signal is at the valid potential, and the duration when the blue enable signal is at the valid potential during the timing output stage; W refers to the duration during the superimposed output stage.

[0080] Figure 4-2 Only the relationship of the enable signals of the three colors in one period is shown. In a specific implementation, the period T0 can be 1 / 240 s, that is, the period of the multi - primary - color enable signal EN can be 240 HZ.

[0081] See Figure 2-2 and Figure 4-1 As Figure 4-1 shown, in one period R_EN0 - T of the red initial image enable signal R - EN0, R_EN0 has a high - level valid period and a low - level invalid period. Here, only one period is taken as an example for illustration.

[0082] As Figure 2-2 and the foregoing description, the display control processing unit simultaneously outputs an image enable signal and a current PWM signal. Usually, the current PWM signal is a square wave with a frequency of 18.3 KHZ. Among them, within the enable signal period of one color, multiple periods of the PWM signal can be included. In Figure 4-1 , only by way of example, within one R_EN0 period, there are approximately 5 periods of the R_PWM0 signal.

[0083] Figure 2-2 In Figure 3-1 , the signal shaping circuit 020 can output a square - wave pulse signal S_f as shown in

[0084] The signal shaping circuit 020 is arranged in the transmission path of the red enable signal R_EN0 and shapes the red enable signal R_EN0. Thus, during the high-level valid period of R_EN0, after being shaped by the signal shaping circuit 020, a high-frequency pulse signal is superimposed on the red enable signal R_EN0. As a result, the red enable signal R_EN0 forms a pulse signal similar to the shaping signal S_f during the high-level valid period within one cycle, and thus the effective level period of R_EN0 is divided into multiple effective level periods, and the total effective level period becomes shorter. For the red current R_PWM0 signal, it always outputs periodically and is restricted by the red enable signal R_EN0, and the current signal can be output to the laser only during the effective level period of R_EN0.

[0085] And the red enable signal R_EN0 after signal shaping changes from the initial continuous high-level valid period to multiple shorter high-level valid periods and invalid periods, and repeats periodically. Thus, for the laser driver circuit and the laser, the driving current finally reaching the red laser 402 is as Figure 4-1 shown in the waveform of the RLD_D signal in, and the driving current of the laser is also divided into multiple waveforms with alternating short high and low levels.

[0086] And as Figure 3-1 shown, the shaping signal has a certain amplitude, with the maximum value being Imax and the minimum value being Imin. In the figure, Io corresponds to the threshold current amplitude for the laser to be lit. Since Imin is less than Io, the minimum value of the driving current waveform of the final laser will also be less than the threshold current Io for the laser to be lit, thus causing the laser to switch frequently between lighting and turning off. And the switching frequency is close to the frequency of the shaping signal.

[0087] In the example of this application, the laser used in the laser projection device is a semiconductor laser, which has a PN junction. As Figure 14 shown is a schematic diagram of the principle of a semiconductor laser light-emitting chip.

[0088] Among them, for the semiconductor laser chip, it works by injecting carriers. If it is to emit laser, three basic conditions must be met:

[0089] (1) For stimulated radiation, sufficient population inversion distribution should be generated, and the number of particles in the high-energy state should be sufficiently greater than the number of particles in the low-energy state;

[0090] (2) Resonant cavity, a suitable resonant cavity can play a feedback role to increase the stimulated radiation photons, thus generating laser oscillation;

[0091] (3) The gain is greater than the loss, and certain threshold conditions should be met to make the photon gain equal to or greater than the photon loss.

[0092] As Figure 14 shown, the semiconductor laser light-emitting chip includes a P region, an active region, and an N region. When a certain forward bias voltage is applied to the laser by energizing it, electrons are injected from the N region into the P region, and holes are injected from the P region into the N region. When enough photon energy is radiated out and meets the above stimulated conditions, a steady-state excitation is formed. The photon radiation propagates strictly within the PN junction plane, and light radiation with the same wavelength, phase, intensity, and relatively large intensity will be output from the active region of the front cavity surface, which is the monochromatic laser beam commonly used. The above process is the stimulated light radiation process of the semiconductor laser, and the laser light-emitting chip needs a process to reach a steady state before it can emit light stably.

[0093] For the PN junction, as long as a forward bias voltage is applied to the PN junction by energizing it, electrons are injected from the N region into the P region, and holes are injected from the P region into the N region. In the active region (also called the active layer, active zone), electrons and holes spontaneously recombine to form electron-hole pairs, and at the same time, the excess energy will be released in the form of photons. At this time, the emitted photons have different phases and directions, and the radiation at this time is called spontaneous radiation. This spontaneous radiation is the radiation mode of the light-emitting diode.

[0094] For a semiconductor laser, only when the drive current reaches the threshold current (the current to turn on the laser), the light emitted by the laser is laser light. If the laser is energized but the self-threshold current is not reached, the laser can also emit light at this time, but the light emitted at this time is fluorescence (called spontaneous radiation).

[0095] Therefore, when the laser is energized to reach above the threshold current, the laser light-emitting chip can perform stable stimulated light radiation and emit a laser beam. If the threshold current of the laser is not reached, the radiation of the laser is not a steady-state stimulated oscillation, but a random photon radiation state, emitting fluorescence, which is the basic working mode of the PN junction.

[0096] According to the above working principle, by periodically providing a drive current that frequently turns the laser on and off, and the current period reaches, for example, at least above 100 MHz. At this time, for the laser light-emitting chip, it is easily in a non-steady state or a state that has not reached a steady state. In this state, the laser operates in a multi-longitudinal mode oscillation mode. When selecting wavelengths, multiple wavelengths will be selected instead of the single wavelength emitted in the steady state. This makes the spectrum of the light emitted by the laser broaden, and compared with the case of a single wavelength, the coherence of the laser beam itself decreases.

[0097] In one embodiment, the signal shaping circuit can output, for example Figure 3-1 , Figure 3-2 , Figure 3-3The high-frequency signal waveform shown has a low value lower than the value corresponding to the laser turn-on threshold current. Specifically, it can be less than the threshold and greater than 0, or it can be 0. Also, the shaping signal frequency is greater than or equal to 100 MHz, for example, it can be 200 MHz. By providing a drive signal that frequently controls the turn-on and turn-off of the laser, such that Figure 14 the laser emission chip shown is, with a high probability, in a state of transitioning to a steady state under frequent current turn-on and turn-off. As a result, the wavelengths of the radiation selected by the front cavity surface activation region will include, in addition to the main wavelength, other wavelengths near the main wavelength. Although these other wavelengths are not as wide in range as the fluorescence spectrum, they have also migrated from the main wavelength and have a relatively high energy distribution ratio, causing the spectral broadening of the laser beam and reducing the coherence of the source itself.

[0098] In Figure 2-2 , the display control processing unit 010 transmits the initial image enable signal to the corresponding signal shaping circuit 020 and transmits the initial current control signal to the corresponding laser driver circuit 030. Then, the initial signal output by the display control processing unit 010 is the initial image enable signal, and the target signal obtained by the signal shaping circuit 020 shaping the initial image enable signal can also be referred to as the target enable signal.

[0099] Optionally, for the scenario where the display control processing unit 010 transmits the initial image enable signal to the corresponding signal shaping circuit 020, each laser driver circuit 030 is used to, when the level of the target enable signal jumps from an invalid level to a valid level, in response to the current control signal, transmit a drive current that can turn on the corresponding laser and keep the drive current unchanged. Then, when the level of the target enable signal jumps from a valid level to an invalid level, in response to the current control signal, the drive current transmitted to the corresponding laser is reduced to a fixed drive current, and this fixed drive current cannot turn on the laser.

[0100] By periodically changing the drive current provided to the laser, the emission brightness of the laser changes periodically, and the spectral width of the emission broadens. Each laser generates lasers of multiple different wavelengths under the drive of the periodically changing drive current, and the coherence between the laser beams of different wavelengths is lower than that of a single-wavelength beam, reducing the coherence of itself.

[0101] See Figure 2-2, after receiving the initial image enable signal R_EN0 corresponding to the red laser 402 transmitted by the display control processing unit 010, the signal shaping circuit 020 can shape the initial image enable signal R_EN0 to obtain the target enable signal R_EN1. The laser driver circuit 030 corresponding to the red laser 402 can respond to the red PWM signal R_PWM transmitted by the display control processing unit 010 and the target enable signal R_EN1 transmitted by the signal shaping circuit 020, and the R_PWM signal is modulated by the target enable signal R_EN1 again, so that the change period of the drive current provided to the red laser 402 is greater than the period of the R_PWM signal and is close to or equal to the change period of the target enable signal R_EN1. In this way, the red laser 402 is used to emit red lasers of at least two different wavelengths under the drive of the periodically changing drive current.

[0102] In the above Figure 2-2 , only the red enable signal R_EN0 is taken as an example. It can be understood that the signal shaping circuit 020 can also be provided in the transmission paths of the blue enable signal B_EN0 and the green enable signal G_EN0 respectively. Thus, the laser driver circuits corresponding to the blue laser and the green laser can respond to the blue PWM signal B_PWM and the green PWM signal G_PWM transmitted by the display control processing unit 010, and the target enable signals B_EN1 and G_EN1 transmitted by the signal shaping circuit 020 respectively, and provide PWM signals with a new change period modulated by the target enable signal to the blue laser 401 and the green laser 403 respectively. The new change period is much lower than the change period of the original PWM signal, so that during the validity period of one cycle of the initial image enable signal, the laser is also in a frequently on-off change state.

[0103] Moreover, in another embodiment, as Figure 2-3 shown, the display control processing unit transmits the initial current control signal to the corresponding signal shaping circuit and transmits the initial image enable signal to the corresponding laser driver circuit. Then, the initial signal output by the display control processing unit is the initial current control signal, and the target signal obtained by shaping the initial current control signal by the signal shaping circuit can also be called the target current control signal.

[0104] Optionally, for the scenario where the display control processing unit 010 transmits an initial current control signal to the corresponding signal shaping circuit 020, each laser driver circuit 030, when the level of the initial image enable signal jumps from an invalid level to a valid level, in response to the target current control signal, will transmit a driving current shaped by the signal shaping circuit 020 to the corresponding laser. Subsequently, when the level of the initial image enable signal jumps from a valid level to an invalid level, the invalid level of the initial image enable signal is ANDed with the driving current signal, rendering the driving current signal invalid, and thus no driving current is transmitted to the laser.

[0105] Reference Figure 2-3 , after receiving the initial current control signal B_PWM0 transmitted by the display control processing unit 010, the signal shaping circuit 020 can shape the initial current control signal B_PWM0 to obtain a target current control signal B_PWM1, and transmit the target current control signal B_PWM1 to the laser driver circuit 030 corresponding to the blue laser 401. The laser driver circuit 030 corresponding to the blue laser 401 can respond to the initial image enable signal B_EN transmitted by the display control processing unit 010 and the target current control signal B_PWM1 transmitted by the signal shaping circuit 020. The above initial image enable signal B_EN and target current control signal B_PWM1 are logically ANDed, and then, a corresponding driving current is provided to the blue laser 401. The blue laser 401 is used to emit laser light under the drive of this driving current.

[0106] Similarly, after receiving the initial current control signal R_PWM0 transmitted by the display control processing unit 010, the signal shaping circuit 020 can shape the initial current control signal R_PWM0 to obtain a target current control signal R_PWM1. The laser driver circuit 030 corresponding to the red laser 402 can respond to the initial image enable signal R_EN transmitted by the display control processing unit 010 and the target current control signal R_PWM1 transmitted by the signal shaping circuit 020, and provide a corresponding driving current to the red laser 402. The red laser 402 is used to emit laser light under the drive of this driving current.

[0107] Further, after receiving the initial current control signal G_PWM0 transmitted by the display control processing unit 010, the signal shaping circuit 020 can shape the initial current control signal G_PWM0 to obtain a target current control signal G_PWM1. The laser driver circuit 030 corresponding to the green laser 403 can respond to the initial image enable signal G_EN transmitted by the display control processing unit 010 and the target current control signal G_PWM1 transmitted by the signal shaping circuit 020, and provide a corresponding drive current to the green laser 403. The green laser 403 is used to emit laser light under the drive of the drive current.

[0108] Next, various embodiments of the present application will be further described in conjunction with specific circuit structures.

[0109] Figure 5 It is a schematic diagram of a part of the hardware circuit of a laser projection device provided by an embodiment of the present application. As Figure 5 shown, the signal shaping circuit 020 in the laser projection device may include a signal generation sub-circuit 021 and a shaping sub-circuit 022. The signal generation sub-circuit 021 is connected to the shaping sub-circuit 022 and is used to transmit a high-frequency signal S_f to the shaping sub-circuit 022. As an example, the high-frequency signal S_f may specifically be a square wave signal. For simplicity, the following description will be based on the high-frequency signal being a square wave signal.

[0110] The shaping sub-circuit 022 is also respectively connected to the display control processing unit 010 and the corresponding laser driver circuit 030. The shaping sub-circuit 022 is used to shape the received initial signal according to the high-frequency signal S_f and output a target signal. As Figure 5 shown, the received initial signal is the initial image enable signal EN0, and the target signal is the target enable signal EN1.

[0111] Among them, the frequency of the high-frequency signal S_f is greater than the frequency of the received initial signal, and within one period of the received initial signal, the total duration of the high-frequency signal S_f at the effective level is less than the duration of the initial signal at the effective level.

[0112] When the initial signal is at the invalid level, the level of the target signal output by the shaping sub-circuit 022 is the invalid level. When the initial signal is at the effective level, the level of the target signal output by the shaping sub-circuit 022 is determined by the level of the high-frequency signal S_f. Therefore, the frequency of the target signal output by the shaping sub-circuit 022 is equal to the frequency of the high-frequency signal S_f, and the duty cycle of the target signal is equal to the duty cycle of the high-frequency signal S_f.

[0113] Optionally, when the level of the initial signal is a valid level, if the level of the high-frequency signal S_f is a valid level, the level of the target signal output by the shaping sub-circuit is a valid level. If the level of the high-frequency signal S_f is an invalid level, the level of the target signal output by the shaping sub-circuit is an invalid level.

[0114] In an optional implementation manner of the embodiment of the present application, Figure 6 is another schematic diagram of the partial hardware circuit structure of the laser projection device provided by the embodiment of the present application. As Figure 6 shown, the shaping sub-circuit 022 in the laser projection device may include a tri-state buffer U2. The input end of the tri-state buffer U2 is connected to the display control processing unit 010 for receiving an initial signal. The control end of the tri-state buffer U2 is connected to the signal generation sub-circuit 021 for receiving the high-frequency signal S_f. The output end of the tri-state buffer U2 is connected to the laser driver circuit 030 for outputting a target signal. The tri-state buffer U2 is also connected to the power supply terminal VCC. The initial signal is an initial image enable signal EN0, and the target signal is a target enable signal EN1. As Figure 7 shown, the received initial signal is an initial current control signal PWM0, and the target signal is a target current control signal PWM1.

[0115] Optionally, the tri-state buffer U2 may conduct when the level of the high-frequency signal S_f received at its control end is an invalid level. Or the tri-state buffer U2 may conduct when the level of the high-frequency signal S_f received at its control end is a valid level. When the tri-state buffer U2 conducts, it can output the signal received at its input end to its output end.

[0116] Refer to Figure 6 and Figure 7 , the shaping sub-circuit 022 may further include an inverter U1. The inverter U1 is connected in series between the signal generation sub-circuit 021 and the control end of the tri-state buffer U2, and is used to invert the high-frequency signal S_f output by the signal generation sub-circuit 021 to obtain an inverted high-frequency signal S_f1. The tri-state buffer U2 may conduct when the inverted high-frequency signal S_f1 received at its control end is a valid level. Or it may also conduct when the inverted high-frequency signal S_f1 received is an invalid level.

[0117] Assume that the tri-state buffer U2 conducts when the inverted high-frequency signal S_f1 received at its control end is an invalid level. Figure 8 is another schematic diagram of shaping the initial image enable signal to obtain the target enable signal provided by the embodiment of the present application. Taking Figure 6 the signal shaping circuit 020 in the laser projection device shown as an example, the process of obtaining the target enable signal from the initial image enable signal will be described.

[0118] Reference Figure 6 and Figure 8 When the initial image enable signal EN0 is at a high level, during the period from t1 to t2, the level of the high-frequency signal S_f is high. After the high-frequency signal S_f passes through the inverter U1, the level of the inverted high-frequency signal S_f1 is low. At this time, after receiving the high-frequency signal S_f1 with a low level at its control terminal, the tri-state buffer U2 conducts, and then the initial image enable signal EN0 received at the input terminal of the tri-state buffer U2 is output from the output terminal of the tri-state buffer U2, that is, the tri-state buffer U2 outputs a target enable signal EN1 at a high level.

[0119] During the period from t2 to t3, the level of the high-frequency signal S_f is low. After the high-frequency signal S_f passes through the inverter U1, the level of the inverted high-frequency signal S_f1 is high. At this time, the tri-state buffer U2 is turned off, and then the output level of the output terminal of the tri-state buffer U2 is low, that is, the tri-state buffer U2 outputs a target enable signal EN1 at a low level. Then, during the period from t3 to t4 and during the period from t5 to t6, the process during the period from t1 to t2 can be repeated, and during the period from t4 to t5, the process during the period from t2 to t3 can be repeated.

[0120] It is assumed that the tri-state buffer U2 conducts when the inverted high-frequency signal S_f1 received at its control terminal is at an invalid level. Figure 9 It is a schematic diagram of another method provided by an embodiment of the present application for shaping an initial current control signal to obtain a target current control signal. Taking Figure 7 the signal shaping circuit 020 in the laser projection device shown as an example, the process of obtaining a target current control signal according to an initial current control signal will be described.

[0121] Reference Figure 7 and Figure 9 When the initial current control signal PWM0 is at a high level, during the period from t1 to t2, the level of the high-frequency signal S_f is high. After the high-frequency signal S_f passes through the inverter U1, the level of the inverted high-frequency signal S_f1 is low. At this time, after receiving the high-frequency signal S_f1 with a low level at its control terminal, the tri-state buffer U2 conducts, and then the initial current control signal PWM0 received at the input terminal of the tri-state buffer U2 is output from the output terminal of the tri-state buffer U2, that is, the tri-state buffer U2 outputs a target current control signal PWM1 at a high level.

[0122] During the time period from t2 to t3, the level of the high-frequency signal S_f is low. After passing through the inverter U1, the level of the inverted high-frequency signal S_f1 obtained is high. At this time, the tri-state buffer U2 is turned off, and the output level of the output terminal of the tri-state buffer U2 is low, that is, the tri-state buffer U2 outputs the target current control signal PWM1 at a low level. After that, the process in the time period from t1 to t2 can be repeated in the time period from t3 to t4.

[0123] In another alternative implementation manner of the embodiment of the present application, Figure 10 is a schematic diagram of a partial hardware circuit structure of another laser projection device provided by the embodiment of the present application.

[0124] Reference Figure 10 , the shaping sub-circuit 022 in the laser projection device may include a tri-state buffer U3. The input terminal of the tri-state buffer U3 is connected to the signal generation sub-circuit 021 for receiving the high-frequency signal S_f. The control terminal of the tri-state buffer U3 is connected to the display control processing unit 010 for receiving the initial signal. The output terminal of the tri-state buffer U3 is connected to the laser driver circuit 030 for outputting the target signal. That is, the conduction and cut-off of the tri-state buffer U3 are controlled by the initial signal.

[0125] Optionally, the tri-state buffer U3 conducts when the level of the initial signal received at its control terminal is a valid level. When the tri-state buffer U3 conducts, it can output the signal received at its input terminal to its output terminal. The initial signal is the initial image enable signal EN0, and the target signal is the target enable signal EN1.

[0126] Assume that the tri-state buffer U3 conducts when the level of the initial signal received at its control terminal is a valid level, and the initial signal is the initial image enable signal EN0. Figure 11 is a timing diagram of another embodiment of the present application for shaping the initial image enable signal to obtain the target enable signal. Taking ​ the signal shaping circuit 020 in the shown laser projection device as an example, the process of obtaining the target enable signal according to the initial image enable signal will be described.

[0127] Reference ​ and ​ , during the time period from t1 to t2, the level of the initial image enable signal EN0 is high. After receiving the initial image enable signal EN0 with a high level at its control terminal, the tri-state buffer U3 conducts. Then, the tri-state buffer U3 receives the high-frequency signal S_f at its input terminal and outputs it from the output terminal of the tri-state buffer U3, that is, the tri-state buffer U3 outputs the target enable signal EN1 at a high level.

[0128] During the time period from t2 to t3, the level of the initial image enable signal EN0 is high. After receiving the initial image enable signal EN0 with a high level at its control terminal, the tri-state buffer U3 conducts. Then, the input terminal of the tri-state buffer U3 receives the high-frequency signal S_f and outputs it from the output terminal of the tri-state buffer U3, that is, the tri-state buffer U3 outputs the target enable signal EN1 with a low level. After that, the process during the time period from t1 to t2 can be repeated during the time periods from t3 to t4 and from t5 to t6, and the process during the time period from t2 to t3 can be repeated during the time period from t4 to t5.

[0129] In another alternative implementation manner of the present application, ​ a schematic diagram of a partial hardware circuit structure of another laser projection device is provided. Refer to ​ , the shaping sub-circuit 022 may include a logic AND device U4. The first input terminal of the logic AND device U4 is connected to the display control processing unit 010 for receiving an initial signal. The second input terminal of the logic AND device U4 is connected to the signal generation sub-circuit 021 for receiving the high-frequency signal S_f. The output terminal of the logic AND device U4 is connected to the laser driver circuit 030 for outputting a target signal. The target signal = the initial signal square wave signal. The supply voltage of the logic AND device U4 is the same as the voltage of the laser driver circuit. The initial signal is the initial image enable signal EN0, and the target signal is the target enable signal EN1.

[0130] Refer to ​ and ​ , during the time period from t1 to t2, the level of the initial image enable signal EN0 output by the display control processing unit 010 is high, and the level of the high-frequency signal S_f output by the signal generation sub-circuit 021 is high. Then, after the initial image enable signal EN0 and the high-frequency signal S_f pass through the logic AND device U4, the logic AND device U4 outputs the target enable signal EN1 with a high level. During the time period from t2 to t3, the level of the initial image enable signal EN0 output by the display control processing unit 010 is high, and the level of the high-frequency signal S_f output by the signal generation sub-circuit 021 is low. Then, after the initial image enable signal EN0 and the high-frequency signal S_f pass through the logic AND device U4, the logic AND device U4 outputs the target enable signal EN1 with a low level. After that, the process during the time period from t1 to t2 can be repeated during the time periods from t3 to t4 and from t5 to t6, and the process during the time period from t2 to t3 can be repeated during the time period from t4 to t5.

[0131] When the level of the initial image enable signal EN0 output by the display control processing unit 010 is low, if the level of the high-frequency signal S_f output by the signal generation sub-circuit 021 is low, after the initial image enable signal EN0 and the high-frequency signal S_f pass through the logic AND device U4, the logic AND device U4 outputs a target enable signal EN1 with a low level. When the level of the initial image enable signal EN0 output by the display control processing unit 010 is low, if the level of the high-frequency signal S_f output by the signal generation sub-circuit 021 is high, after the initial image enable signal EN0 and the high-frequency signal S_f pass through the logic AND device U4, the logic AND device U4 outputs a target enable signal EN1 with a low level.

[0132] Optionally, referring to ​ 、 ​ 、 ​ 、 ​ and ​ , the signal shaping circuit 020 may further include a resistor R. One end of the resistor R is respectively connected to the shaping sub-circuit 022 and the laser driver circuit 030, and the other end of the resistor R is connected to the reference power supply terminal vr. The reference power supply terminal vr may be a ground terminal (ground, GND).

[0133] In the embodiment of the present application, the frequency f of the high-frequency signal S_f is greater than or equal to 10 megahertz (MHz), that is, f ≥ 100 MHz. The frequency of the target signal is equal to or close to the frequency of the high-frequency signal S_f. Thereby, it can effectively avoid the inductance and capacitance around the laser driver circuit from generating audible noise when the frequency of the target signal is lower than 200 kilohertz (KHz).

[0134] During the process of projecting an image, due to the voltage ripple of the display control processing unit, the driving current provided by the laser driver circuit to the laser will fluctuate, thereby generating ​ the current ripple C as shown. The maximum value of the current of the current ripple C needs to be within the fluctuation range m, and the m is [-10% × I0, 10% × I0]. And the frequency of the current ripple C needs to be greater than 250 KHz, thereby ensuring the consistent reset of the DMD group and further ensuring the display effect of the projected image.

[0135] The hardware system of the laser projection device has clear specification requirements for the current waveform of the driving current of the laser. When the current waveform satisfies: 0 A ≤ 19 us, 0 B ≤ 19 us and the maximum value of the current of the current ripple C is within the fluctuation range m, the laser projection device can operate normally.

[0136] Therefore, in order to achieve speckle dissipation, while ensuring 0 A 19 us, 0 B When the maximum current of 19 us and the current ripple C are within the fluctuation range m, it is necessary to ensure that the brightness loss of the laser is small and the drive current of the laser decreases.

[0137] In the embodiment of the present application, referring to ​ , ​ , ​ or ​ , the laser projection device may further include a signal conversion circuit 050, which is respectively connected to the display control processing unit 010 and the laser driver circuit 030. The signal conversion circuit 050 is configured to convert the PWM signal transmitted by the display control processing unit 010 into an analog signal and send the analog signal to the laser driver circuit 030.

[0138] Due to the high coherence of the laser, the laser emitted by the laser projection device forms light and dark spots on the projection screen, also known as speckles. The light source of the laser projection device is mainly a laser, and the laser can be a semiconductor laser, and the semiconductor is a compound semiconductor. According to the light-emitting principle of the laser, when the drive current of the laser is changed at a high frequency, causing the laser to undergo high-frequency on and off changes, it can affect the formation of the laser light-emitting steady state, thereby selecting adjacent multiple wavelength laser beams with a high probability, expanding the spectral width of the laser, and thus greatly reducing the coherence of the laser beam itself, thereby weakening or suppressing the speckle phenomenon presented in the projection screen from the source.

[0139] The laser projection device provided by the present application shapes the drive signal of the laser, so that the change period of the drive current finally acting on the laser is shortened and the frequency is increased. Moreover, within one period, the high-level voltage of the drive signal can turn on the laser, and the low-level voltage is not greater than the threshold current of the laser, forming a drive signal that can frequently control the on and off of the laser, affecting the normal laser steady-state light-emitting process, and greatly reducing the speckle phenomenon.

[0140] Compared with the related art in which a diffusion sheet and other speckle dissipation components are provided in the laser projection device, and the speckle dissipation principle and method of increasing the spatial phase of the laser are used, the laser projection device provided by the present application can achieve speckle dissipation from the source.

[0141] If the laser projection device is a three-color laser projection device, the formation of speckles is a kind of diffraction, and the longer the wavelength, the more obvious the diffraction effect. Therefore, the speckles of the red laser are more serious, followed by the green laser, and the speckles of the blue laser are smaller. By changing the driving current of the laser at high frequency and periodically, the spectral width of the laser beam can be expanded, the coherence of the laser itself can be changed from the source, and further the influence of the speckle phenomenon on the projection image can be weakened, and the image quality display effect of the three-color laser projection device can be improved.

[0142] And, ​ is a flowchart of a laser driver control method provided by an embodiment of the present application. This method can be applied to ​ , ​ , ​ , ​ or ​ , ​ , ​ , ​ , ​ or ​ any one of the signal shaping circuits 020 in at least one signal shaping circuit 020 of the laser projection device shown. The laser projection device may further include a display control processing unit 010, a laser 040, and at least one laser driver circuit 030. The laser 040 includes at least one group of lasers corresponding one-to-one to the at least one laser driver circuit 030. As ​ shown, this method may include:

[0143] Step 1501, the display control processing unit outputs an initial driving signal.

[0144] Specifically, as described in the foregoing embodiment, when the display control processing unit outputs an image driving signal to the light modulation component, it also outputs an initial driving signal to the light source part: an image enable signal or a primary color light enable signal EN, and a brightness adjustment signal, also called a current PWM signal. The result of the logical AND of these two initial driving signals acts on the laser.

[0145] If it is applied to a three-color laser projection device, the initial driving signal is one of at least one initial image enable signal and at least one initial current control signal. The at least one initial image enable signal is at least one enable signal corresponding one-to-one to the three primary colors of each frame of the multi-frame display image output by the display control processing unit, and the at least one initial current control signal is at least one current control signal corresponding one-to-one to the three primary colors of each frame of the multi-frame display image output by the display control processing unit.

[0146] Step 1602, shape the initial driving signal to obtain a target driving signal.

[0147] Specifically, before the initial drive signal of the display control processing unit reaches the laser, it will be output to the laser drive circuit first, and finally transmitted to the laser by the laser drive circuit.

[0148] In the path where the initial drive signal output by the display control processing unit is finally transmitted to the laser, there is also a signal shaping circuit that shapes the initial drive signal to obtain a target drive signal.

[0149] Either one or both of the above two initial drive signals can be signal-shaped. Among them, signal shaping can modulate the initial drive signal with a periodic high-frequency signal whose frequency is much higher than the frequency of any one of the signals in the initial drive signal, or superimpose it on the initial drive signal to shape the initial drive signal into a drive signal equal to or close to the high-frequency signal. The change period of this drive signal is much larger than the change period of any one of the signals in the initial drive signal.

[0150] Step 1503: Transmit the target drive signal to the corresponding laser.

[0151] In the above steps, the shaped initial drive signal becomes the target drive signal, and finally acts on the laser to change the change period of the laser's lighting and extinguishing.

[0152] Among them, the frequency of the target drive signal is much higher than the frequencies of the initial image enable signal and the current PWM signal. Also, within one cycle of the initial image enable signal, the total duration of the target drive signal at the effective level is less than the duration of the initial image enable signal at the effective level or less than the duration of the effective level of the initial PWM current signal. And the value of the low-level value of the target drive signal is less than the threshold current of the laser and greater than or equal to 0.

[0153] The laser finally receives the target drive signal and undergoes frequent on-off changes under the action of the high-frequency drive signal, thereby affecting the emission period and wavelength of the laser. By affecting the formation of the steady-state emission state of the laser, the spectral width of the laser emitted is broadened, and the coherence of the laser beam itself is reduced, providing a low-coherence laser beam from the source. When performing the projection display of the laser projection screen, the speckle phenomenon is also alleviated.

[0154] As described above, a laser driving control method provided by an embodiment of the present application can shape an initial driving signal output by a display control processing unit (which is a driving signal to be received by a laser) to obtain a target driving signal, and transmit the target driving signal to a corresponding laser driving circuit to drive the corresponding laser to emit light. Eventually, the change period of the driving current acting on the laser is shortened and the frequency is increased. Moreover, within the period of one target driving signal, the high-level value of the driving signal can turn on the laser, and the low-level value is not greater than the threshold current of the laser, forming a driving signal that can frequently control the on and off of the laser, affecting the normal laser steady-state light-emitting process, broadening the width of the laser emission spectrum, greatly reducing the coherence of the laser beam, and being able to eliminate or suppress the speckle phenomenon when applied to a laser projection device for projection display.

[0155] The foregoing are only optional embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A laser projection device, characterized in that, Comprising: A blue laser, a red laser, a green laser, a laser driving circuit corresponding to each color laser, an optical modulation device, a display panel, and a signal shaping circuit; The display panel is used to generate a modulation driving signal for driving the optical modulation device, and is also used to generate a driving signal for driving each color laser to emit light, and the driving signal includes an initial image enable signal and an initial current control signal; The signal shaping circuit is connected to the display panel and is arranged in the path where the initial image enable signal and the initial current control signal are transmitted to at least one color laser, and is used to output a shaping signal, and the shaping signal is superimposed on the initial image enable signal and the initial current control signal or either of them to form a target driving signal; The laser driving circuit is used to receive the target driving signal and directly drive the corresponding color laser to emit light or go out, and the target driving signal is a high-frequency periodic driving signal; The low value level of the target driving signal is less than the lighting threshold current of each corresponding laser and is greater than or equal to 0.

2. The laser projection device according to claim 1, wherein The low value level of the shaping signal is equal to 0.

3. The laser projection device according to claim 1, characterized in that The laser driving circuit is arranged on the power supply board or is arranged independently of the power supply board.

4. The laser projection device according to claim 1, characterized in that, The signal shaping circuit is arranged on the display panel; or, the signal shaping circuit is arranged in the circuit between the laser driving circuit and the display panel; or, the signal shaping circuit is arranged in the laser driving circuit.

5. The laser projection device according to any one of claims 1-4, characterized in that, The shaping signal is a high-frequency periodic signal; the waveform is a square wave signal, or a triangular wave signal; or a sawtooth wave signal.

6. The laser projection device according to claim 5, characterized in that, The signal shaping circuit includes a signal generation sub-circuit and a shaping sub-circuit, and the signal generation sub-circuit is connected to the shaping sub-circuit and is used to transmit a high-frequency signal to the shaping sub-circuit; The shaping sub-circuit is used to shape the received initial signal according to the high-frequency signal and output the target driving signal.

7. The laser projection device according to claim 5, characterized in that, It further includes a signal conversion circuit, the display panel includes a display control processing unit, and the signal conversion circuit is used to convert the PWM current signal transmitted by the display control processing unit into an analog signal; the PWM current signal is the initial current control signal.

8. The laser projection device according to claim 5, wherein, Among the enable signals corresponding to the three primary colors output by the red laser, the blue laser, and the green laser in one driving cycle, only one of the three enable signals is in the high-level valid period at a certain moment, and the other two signals are in the low-level invalid period.

9. The laser projection device according to claim 1, wherein The red laser, the blue laser, and the green laser are independently packaged light-emitting units, or are multi-color chips packaged in one light-emitting unit.

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