Image projection apparatus

Abstract

The image projection apparatus includes: a first light source for emitting first coherent light; the second light source is used for emitting second coherent light with the same wavelength as the first coherent light; a first optical system for adjusting a first distance between a first chief ray located at the center of the first coherent light and a second chief ray located at the center of the second coherent light; and the scanner is used for scanning the first coherent light and the second coherent light after the first optical system adjusts the first distance towards the retina of the user. The image projection apparatus is configured such that a > = b. A is the first distance before the first optical system is adjusted, and b is the first distance after the first optical system is adjusted. B is a first distance at a first imaging point, and the first imaging point is located between the scanner and a second imaging point on the retina.

Description

Technical Field

[0001] This application relates to image projection devices, and more particularly to an image projection device that projects images onto a user's retina. Background Technology

[0002] In recent years, head-mounted augmented reality (AR) glasses, as one of the image projection devices, have been under development.

[0003] In image projection devices such as AR glasses, light emitted from a light source is scanned by a scanning mirror. The scanned light then illuminates the user's retina, projecting an image onto the retina. By scanning the light, an image can be projected onto the retina, allowing the user to see a high-resolution image.

[0004] However, in traditional image projection devices, the resonant frequency of the scanning mirror is difficult to increase due to physical limitations. This difficulty in increasing the scanning mirror's resonant frequency further hinders the improvement of resolution in traditional image projection devices. Summary of the Invention

[0005] This application aims to solve at least one of the above-mentioned technical problems. Therefore, this application provides an image projection device.

[0006] According to this application, an image projection device includes: The first light source is used to emit the first coherent light; The second light source is used to emit second coherent light with the same wavelength as the first coherent light; A first optical system is used to adjust a first distance between a first principal ray located at the center of the first coherent light emitted by the first light source and a second principal ray located at the center of the second coherent light emitted by the second light source; A scanner for scanning the first coherent light and the second coherent light after the first optical system has adjusted the first distance; and A second optical system is used to project an image onto the user's retina by illuminating the first and second coherent light scanned by the scanner onto the user's retina; The image projection device is configured as follows: a ≥ b; a is the first distance before the first optical system is adjusted, b is the first distance after the first optical system is adjusted, b is the first distance at the first imaging point, and the first imaging point is located between the scanner and the second imaging point on the retina. Attached Figure Description

[0007] The various aspects and advantages of the embodiments of this application will become clear and easier to understand from the following description taken in conjunction with the accompanying drawings.

[0008] Figure 1 This is a schematic diagram of an image projection device provided in the first embodiment of this application.

[0009] Figure 2 This is a schematic diagram illustrating the operation of the image projection device provided in the first embodiment of this application.

[0010] Figure 3-1 This is a schematic diagram of linear modulation provided in the first embodiment of this application.

[0011] Figure 3-2 This is a schematic diagram of linear modulation combined with pulse width modulation provided in the first embodiment of this application.

[0012] Figure 3-3 This is a schematic diagram illustrating linear modulation combined with pulse width modulation provided in the first embodiment of this application.

[0013] Figure 3-4 This is another illustrative diagram illustrating the linear modulation combined with pulse width modulation provided in the first embodiment of this application.

[0014] Figure 3-5 This is another illustrative diagram illustrating the linear modulation combined with pulse width modulation provided in the first embodiment of this application.

[0015] Figure 3-6 This is a further illustrative diagram illustrating the linear modulation combined with pulse width modulation provided in the first embodiment of this application.

[0016] Figure 4 This is a schematic diagram of the optical swing angle provided in the first embodiment of this application.

[0017] Figure 5 A schematic diagram showing the relationship between resolution and resonant frequency provided for the first embodiment of this application.

[0018] Figure 6 This is a schematic diagram of multi-beam scanning provided in the first embodiment of this application.

[0019] Figure 7 This is a schematic diagram illustrating the relationship between resolution and viewing angle provided in the first embodiment of this application.

[0020] Figure 8 A schematic diagram of the vertical viewing angle required for projecting a 4K high-resolution image as provided in the first embodiment of this application.

[0021] Figure 9 A schematic diagram of the light spacing in the sub-scanning direction on the retina required for projecting a 4K high-resolution image as provided in the first embodiment of this application.

[0022] Figure 10 A schematic diagram of the main ray spacing required for projecting a 4K high-resolution image according to the first embodiment of this application.

[0023] Figure 11 This is a schematic diagram of the configuration of the first optical system provided in the first embodiment of this application.

[0024] Figure 12 A schematic diagram of a cylindrical lens for a first optical system provided in the second embodiment of this application.

[0025] Figure 13 This is a schematic diagram of the beam emission angle of the edge-emitting laser provided in the second embodiment of this application.

[0026] Figure 14 This is a schematic diagram of the threshold current of the edge-emitting laser provided in the second embodiment of this application.

[0027] Figure 15 This is a schematic diagram of the configuration of the first optical system provided in the third embodiment of this application.

[0028] Figure 16 A schematic diagram of the first optical system provided in the fourth embodiment of this application.

[0029] Figure 17 This is a schematic diagram of the configuration of the first optical system provided in the fourth embodiment of this application.

[0030] Figure 18 A schematic diagram of a beam deflector for a first optical system provided in the fifth embodiment of this application.

[0031] Figure 19 A schematic diagram of a beam deflector for a first optical system provided in the sixth embodiment of this application.

[0032] Figure 20 A schematic diagram of a beam deflector for a first optical system provided in the seventh embodiment of this application.

[0033] Figure 21 A schematic diagram of a beam deflector for a first optical system provided in the eighth embodiment of this application.

[0034] Figure 22 This is a schematic diagram of a vertical cavity surface-emitting laser (VCSEL) provided in the ninth embodiment of this application.

[0035] Figure 23 A schematic diagram of a first optical system provided as a first example of this application.

[0036] Figure 24 A schematic diagram of the main ray spacing provided for the first example of this application.

[0037] Figure 25 A schematic diagram of the first optical system provided as a second example of this application.

[0038] Figure 26 A schematic diagram of the main ray spacing provided for the second example of this application.

[0039] Figure 27 A schematic diagram of the first optical system provided for the third example of this application.

[0040] Figure 28 A schematic diagram of the main ray spacing provided for the third example of this application.

[0041] Figure 29 A schematic diagram of the first optical system provided for the fourth example of this application.

[0042] Figure 30 A schematic diagram of the main ray spacing provided for the fourth example of this application.

[0043] Figure 31 A schematic diagram of the first optical system provided for the fifth example of this application.

[0044] Figure 32 A schematic diagram of the main ray spacing provided for the fifth example of this application. Detailed Implementation

[0045] Embodiments of this application will be described in detail, and examples of embodiments will be illustrated in the accompanying drawings. Throughout the description, the same or similar elements, as well as elements having the same or similar functions, are denoted by the same reference numerals. The embodiments described herein with reference to the accompanying drawings are merely illustrative and are intended to explain this application, but should not be construed as limiting this application.

[0046] First Embodiment The following is a description of the image projection device provided in the first embodiment of this application. The image projection device provided in the first embodiment is an eye-tracking retinal projection head-mounted display, which can track the user's gaze direction and project images onto the user's retina (hereinafter the same). Figure 1 As shown, the image projection device 1 provided in the first embodiment includes a light source 11, a first optical system 12, a scanner 14, a second optical system 15, a line-of-sight detector 16, an optical system controller 17, a light source controller 18, and an angular velocity sensor 19.

[0047] exist Figure 1 In the text, the X direction is the direction along the sub-scanning direction of scanner 14 (the same applies below). Figure 1 This is a top view of the image projection device 1 as viewed from a direction perpendicular to the YZ plane. Figure 1Box F1 is an enlarged view of the light source 11 as viewed from a different direction than the top view.

[0048] like Figure 1 As shown in box F1, the light source 11 includes a plurality of laser elements (i.e., light sources) 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) that emit laser light (i.e. coherent light).

[0049] In some embodiments, the light source 11 includes a plurality of first laser elements 111a, 111b, and 111c that emit laser beams of the same wavelength. The first laser elements 111a, 111b, and 111c are spaced apart along the sub-scanning direction of the scanner 14, i.e., the X direction. In other words, the first laser elements 111a, 111b, and 111c are arranged adjacent to each other in the X direction. The first laser elements 111a, 111b, and 111c emit laser beams along the Z direction, which is perpendicular to the X direction. The first laser elements 111a, 111b, and 111c emit laser beams, such as those with a wavelength of 650 nm (i.e., red). "Same wavelength" can refer to exactly the same wavelength. "Same wavelength" is not limited to exactly the same wavelength; it can also refer to substantially the same wavelength that can be visually identified as the same color (the same applies below).

[0050] The light source 11 includes a plurality of second laser elements 112a, 112b, and 112c that emit laser beams of the same wavelength, but with a wavelength different from that emitted by the first lasers 111a, 111b, and 111c. The second laser elements 112a, 112b, and 112c are spaced apart in the X-direction. In other words, the second laser elements 112a, 112b, and 112c are adjacent to each other in the X-direction. The second laser elements 112a, 112b, and 112c are adjacent to the first laser elements 111a, 111b, and 111c in the Y-direction, which is perpendicular to both the X and Z directions. The second laser elements 112a, 112b, and 112c emit laser beams along the Z-direction. The second laser elements 112a, 112b, and 112c emit laser beams, for example, with a wavelength of 520 nm (i.e., green).

[0051] The light source 11 also includes a plurality of third laser elements 113a, 113b, and 113c that emit laser beams of the same wavelength, the wavelength of which is different from the wavelength of the laser beams emitted by the first laser elements 111a, 111b, and 111c and the wavelength of the laser beams emitted by the second laser elements 112a, 112b, and 112c. The third laser elements 113a, 113b, and 113c are arranged adjacent to each other in the X direction. The third laser elements 113a, 113b, and 113c are arranged adjacent to the second laser elements 112a, 112b, and 112c in the Y direction. The third laser elements 113a, 113b, and 113c emit laser beams along the Z direction. The third laser elements 113a, 113b, and 113c emit laser beams, for example, with a wavelength of 450 nm (i.e., blue).

[0052] In the first embodiment, laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) are edge-emitting lasers. An edge-emitting laser may include a p-type semiconductor layer, an n-type semiconductor layer, and an active layer formed between the p-type and n-type semiconductor layers.

[0053] Laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) are mounted on a driving circuit 110 with a semiconductor chip. When the current supplied by the driving circuit 110 exceeds the oscillation threshold Ith, the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) emit laser beams.

[0054] According to the above configuration, the light source 11 can simultaneously emit multiple beams of light with the same wavelength.

[0055] A first optical system 12 is positioned relative to the light source 11 on the emission side of the laser beam. The first optical system 12 guides the laser beam emitted by the light source 11 to the scanner 14. The first optical system 12 adjusts the distance between the central principal ray of a laser beam emitted from any one laser element (e.g., first laser element 111a) and the central principal ray of a laser beam of the same wavelength emitted from an adjacent laser element (e.g., first laser element 111b). In some embodiments, the first optical system 12 reduces the distance between adjacent principal rays of the same wavelength. By adjusting the distance between adjacent principal rays of the same wavelength, a high-resolution image can be projected onto the user's retina. The specific structure of the first optical system 12 will be described below.

[0056] Scanner 14 is positioned relative to the first optical system 12 on the laser beam emission side. The laser beam emitted (i.e., guided) from the first optical system 12 is incident on scanner 14. Scanner 14 rotates about a first rotation axis in the X direction to change the horizontal component of the incident angle of the laser beam. By changing the horizontal component of the incident angle, scanner 14 changes the horizontal component of the reflection angle of the laser beam reflected by scanner 14. By changing the horizontal component of the reflection angle, scanner 14 rotates along... Figure 1 The scanner 14 scans the laser beam in the main scanning direction along the YZ plane (i.e., the horizontal direction). The scanner 14 also rotates about a second rotation axis perpendicular to the first rotation axis to change the vertical component of the incident angle of the laser beam. By changing the vertical component of the incident angle, the scanner 14 changes the vertical component of the reflection angle of the laser beam. By changing the vertical component of the reflection angle, the scanner 14 scans the laser beam in the sub-scanning direction along the X direction (i.e., the vertical direction).

[0057] Scanner 14 may include a first scanning mirror having a first rotation axis for scanning in the main scanning direction and a second scanning mirror having a second rotation axis for scanning in the sub-scanning direction, in which case scanner 14 can scan the laser beam using a raster scanning method. Alternatively, scanner 14 may be a single scanning mirror having both a first and a second rotation axis, in which case scanner 14 can scan the laser beam using a Lissajous scanning method.

[0058] Scanner 14 can be a micro-electromechanical system (MEMS) mirror.

[0059] The second optical system 15 is positioned relative to the scanner 14 on the laser beam emission side. The laser beam emitted from the scanner 14 is incident on the second optical system 15. The second optical system 15 illuminates the user's retina with the laser beam incident from the scanner 14 to project an image onto the retina.

[0060] In some embodiments, the second optical system 15 includes a first lens 151, a second lens 152, a first reflector 153, a second reflector 154, and a third reflector 155.

[0061] In the second optical system 15, the first lens 151 is positioned closest to the scanner 14. The laser beam emitted from the scanner 14 is directly incident on the first lens 151. The first lens 151 diverges the incident laser beam and emits the diverged laser beam.

[0062] The second lens 152 is positioned relative to the first lens 151 on the emission side of the laser beam. The laser beam emitted from the first lens 151 is incident on the second lens 152. The second lens 152 is used to converge and emit the incident laser beam to convert the laser beam scanned by the scanner 14 into a collimated beam.

[0063] A first reflector 153 is positioned opposite the second lens 152 on the emission side of the laser beam. The laser beam emitted from the second lens 152 is incident on the first reflector 153. The first reflector 153 reflects the incident laser beam. The first reflector 153 may be a half-reflector.

[0064] The second reflector 154 is positioned relative to the first reflector 153 on the reflecting side of the laser beam. The laser beam reflected from the first reflector 153 is incident on the second reflector 154. The second reflector 154 reflects the incident laser beam. The second reflector 154 can rotate about a rotation axis in the X direction under the control of the optical system controller 17, thereby changing the reflection direction of the laser beam. The optical system controller 17 controls the rotation of the second reflector 154 based on at least one of the viewing direction detected by the viewing direction detector 16 and the angular velocity of the image projection device 1 detected by the angular velocity sensor 19. In some embodiments, the optical system controller 17 controls the rotation of the second reflector 154 such that the laser beam reflected by the second reflector 154 is projected onto the user's retina. The second reflector 154 can be a tilting reflector module. The tilting reflector module can include a tilting reflector, a reflector support mechanism, a magnetic drive mechanism, and a permanent magnet. The reflector support mechanism supports the tilting reflector so that it can rotate about a rotation axis. The magnetic drive mechanism is disposed on the tilting reflector and converts the electrical signal (e.g., an electrical signal of a drive current) provided by the optical system controller 17 into a magnetic drive force. A permanent magnet is disposed in the reflector support mechanism. A magnetic driving force (i.e., attractive or repulsive force) generated by the magnetic drive mechanism acts on the permanent magnet. The tilting reflector rotates about a rotation axis by the magnetic driving force acting on the permanent magnet. Thus, the optical system controller 17 can control the magnitude of the electrical signal supplied to the magnetic drive mechanism according to the viewing direction and / or angular velocity of the image projection device 1, thereby controlling the rotation of the second reflector 154.

[0065] The third reflecting mirror 155 is positioned relative to the second reflecting mirror 154 on the reflecting side of the laser beam. The laser beam reflected from the second reflecting mirror 154 is incident on the third reflecting mirror 155. The third reflecting mirror 155 reflects the incident laser beam to the user's retina. The third reflecting mirror 155 can be a freeform mirror. The third reflecting mirror 155 can be a microstructured diffractive optical element or a holographic optical element.

[0066] The gaze direction detector 16 includes an illuminator 16-1 and a gaze position detector 16-2. The illuminator 16-1 illuminates infrared light into the user's eyes. To reduce power consumption, the illuminator 16-1 includes an infrared laser element, such as a VCSEL or an infrared LED. The gaze position detector 16-2 receives the reflected light from the infrared light that has illuminated the user's eyes. Based on the intensity of the received reflected light, the gaze position detector 16-2 outputs a gaze direction detection signal to the optical system controller 17 and the light source controller 18. The gaze direction detector 16 can be an eye-tracking camera.

[0067] The optical system controller 17 controls the second optical system 15 based on the gaze direction detected by the gaze direction detector 16. In some embodiments, such as Figure 2 As shown, the optical system controller 17 rotates the second reflector 154 based on changes in the gaze direction detected by the gaze direction detector 16, so that the laser beam can be focused on the pupil, and the image can be continuously projected onto the retina regardless of changes in the gaze direction. In this way, the user can continue to see the image even after moving their eyes.

[0068] By projecting a laser beam onto the retina following the user's gaze, the eyebox can be enlarged. Furthermore, since the luminous flux of the laser beam is less than the observer's pupil diameter, no focusing is required. In addition, high-resolution images can be projected, the color gamut of the image can be expanded, and color irregularities in the image can be virtually eliminated.

[0069] The optical system controller 17 can control the rotation of the second reflector 154 based on the detection results of the angular velocity sensor 19 and the gaze position detector 16-2. In some embodiments, when the angular velocity sensor 19 detects the angular velocity (i.e., vibration) of the image projection device 1, the optical system controller 17 controls the rotation of the second reflector 154 to counteract the detected angular velocity. Thus, even if the image projection device 1 vibrates, it can continue to project images onto the retina according to the user's gaze direction.

[0070] The light source controller 18 controls the light source 11 to emit a laser beam. In some embodiments, the light source controller 18 obtains image data of an image to be projected onto the user's retina from a memory or host device. The light source controller 18 sequentially drives first laser elements 111a, 111b, and 111c, second laser elements 112a, 112b, and 112c, and third laser elements 113a, 113b, and 113c according to the pixel values ​​indicated by the image data. In this case, the light source controller 18 can drive laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) through linear modulation driving. Figure 3-1As shown, in linear modulation driving, the light source controller 18 inputs an analog input signal having a modulation input level corresponding to the pixel value of the image data to the driving circuit 110 of the light source 11. The driving circuit 110 inputs a driving current corresponding to the modulation input level of the input signal to the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c). In response to the input driving current, the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) emit laser beams having an output level corresponding to the modulation input level. By performing linear modulation driving, the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) can be driven at high speed.

[0071] The light source controller 18 can also drive laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) by combining pulse width modulation (PWM) with linear modulation. In pulse width modulation, such as... Figure 3-2 As shown, when rendering a Full HD image at a frame rate of 90Hz, if conventional linear modulation is used, the light source controller 18 can emit a laser beam with linearly modulated current values ​​over a 5-nanosecond (nsec) time period. For example, when the laser intensity equivalent to a 6-mW continuous wave (CW) beam needs to be output via PWM drive over 1 nsec, the PWM drive is divided into five 5-nsec segments. When a peak power of 30mW is output in one of the five segmented pulses (each 1 nsec), the average output power is 30 / 5 = 6mW, and the power consumption can be reduced to 38% of that of conventional linear drive.

[0072] In some embodiments, if using such Figure 3-3 and Figure 3-4 The laser output characteristics shown (such as 5V drive) of the laser are described, and will Figure 3-3 If the maximum pulse output is set to 30mW (the maximum value for 8-bit grayscale), then the power consumption is 5V x 86mA = 430mW (refer to...). Figure 3-6 However, in reality, when driven by a short pulse of 1 nsec, since only 1 nsec of light is emitted out of 5 nsec, the average output is 30mW x 20% = 6mW, resulting in a power consumption of 430 x 20% = 86mW (refer to...). Figure 3-6 During CW oscillation, if the output is 6mW with 5nsec modulation, the power consumption is 226mW (refer to...). Figure 3-5Therefore, as mentioned above, power consumption can be reduced by 38%. In the case of 6-bit grayscale, the pulse output may be 30 / 256*64=7.5mW. Therefore, using linear modulation drive combined with pulse width modulation can reduce power consumption.

[0073] The light source controller 18 can control the resolution of the image projected onto the user's retina based on the gaze direction detected by the gaze direction detector 16. For example, the light source controller 18 can control the resolution of the peripheral image projected onto the peripheral area of ​​the retina located outside the user's gaze direction, making it lower than the resolution of the central image projected onto the central area of ​​the retina located in the user's gaze direction. By reducing the resolution of the peripheral image, power consumption is reduced.

[0074] Reference Figures 4 to 10 The technical significance of the first optical system 12 will be explained. Figures 4 to 10 In this example, we will use scanner 14, which is a MEMS, as an example for explanation.

[0075] like Figure 4 As shown, when the diameter of the MEMS is D, the mechanical swing angle of the MEMS is θmech, the optical swing angle of the MEMS is θopt, and the wavelength of the laser beam is λ, the spatial resolution can be expressed by the following formula.

[0076] N=θopt*D / 1.1λ (1) Where θopt equals 2*θmech.

[0077] Figure 5 The relationship between various resolutions (such as HALF HD, HD, FHD, 2K, 4K) and the corresponding θopt*D and resonant frequency for each resolution is shown.

[0078] like Figure 5 As shown, the higher θopt*D is, the higher the image resolution (including horizontal and vertical resolution). Additionally, the higher the horizontal resonant frequency fH of the MEMS (i.e., the scanning speed), the higher the image resolution.

[0079] The horizontal resonant frequency fH of the MEMS is expressed by the following formula using the frame rate fV, vertical resolution V, and vertical scan effective time rate Kv (approximately 0.89).

[0080] fH=fV*V / (2*Kv) (2) from Figure 5 It can be seen that increasing the horizontal resonant frequency fH can improve image resolution. However, there is a limit to increasing the horizontal resonant frequency fH, assuming the MEMS reaches its physical limits and is damaged. Therefore, improving image resolution by increasing the horizontal resonant frequency fH is challenging.

[0081] Conversely, in the first embodiment, multi-beam scanning is performed using multiple laser elements of the same wavelength (e.g., first laser elements 111a, 111b, and 111c). Multi-beam scanning reduces the vertical spatial resolution of each laser beam. For example, as... Figure 6 As shown, when performing dual-beam scanning, the vertical spatial resolution of each laser beam is reduced by half. Since the vertical spatial resolution of each laser beam is reduced, the horizontal resonant frequency fH also decreases. Increasing θopt*D by reducing the horizontal resonant frequency fH does not push the MEMS to its physical limits. Instead, increasing θopt*D improves the image resolution.

[0082] Figure 7 The relationship between various resolutions and viewing angles (including vertical field of view (VFOV) and horizontal field of view (HFOV)) is shown. Figure 8 The vertical visual angle (VFOV) required to project a 4K high-resolution image is shown.

[0083] As mentioned above, using multiple laser elements of the same wavelength for multi-beam scanning is beneficial for improving image resolution.

[0084] When attempting to achieve 4K resolution through multi-beam scanning, a vertical field of view (VFOV) of 1 arcminute (min) is required, such as... Figure 7 and Figure 8 As shown.

[0085] To achieve a vertical field of view (VFOV) of 1 arcminute, the spacing between the rays of the multi-beam array on the retina along the vertical direction (i.e., the sub-scanning direction) must be 5 μm, such as... Figure 9 As shown in box F2. Figure 9 In the optical system shown, the laser beam emitted from the laser element 111a is directed to the retina through a collimating lens, a multiplexing prism, a lens, a MEMS, and a freeform mirror. Figure 9 The optical system shown is an example of a conventional optical system.

[0086] If a conventional optical system were used to achieve a vertical distance of 5 μm between light rays on the retina, the spacing between adjacent laser elements would need to be approximately 0.6 μm. However, achieving such a laser element spacing is extremely difficult. Therefore, it is very difficult to achieve a vertical distance of 5 μm using a conventional optical system.

[0087] Therefore, the image projection device 1 provided in the first embodiment is provided with a first optical system 12 so that the vertical distance between the light rays on the retina is small enough.

[0088] The first optical system 12 adjusts the distance (i.e., the first distance) between the principal ray (i.e., the first principal ray) located at the center of the laser beam (i.e., the first coherent beam) emitted from any first laser element 111a (i.e., the first light source) and the principal ray (i.e., the second principal ray) located at the center of the laser beam (i.e., the second coherent beam) emitted from an adjacent first laser element 111b (i.e., the second light source) of the same wavelength.

[0089] The first optical system 12 also adjusts the distance (i.e., the third distance) between the central principal ray (i.e., the fourth principal ray) of the laser beam (i.e., the fourth coherent beam) emitted from any one of the second laser elements 112a (i.e., the fourth light source) and the central principal ray (i.e., the fifth principal ray) of the laser beam (i.e., the fifth coherent beam) emitted from the adjacent second laser element 112b (i.e., the fifth light source) of the same wavelength.

[0090] The first optical system 12 also adjusts the distance (i.e., the fourth distance) between the central principal ray (i.e., the sixth principal ray) of a laser beam (i.e., the sixth coherent beam) emitted from any one of the third laser elements 113a (i.e., the sixth light source) and the central principal ray (i.e., the seventh principal ray) of a laser beam (i.e., the seventh coherent beam) emitted from an adjacent third laser element 113b (i.e., the seventh light source) of the same wavelength. In other words, the first optical system 12 adjusts the distance between adjacent principal rays of the same wavelength.

[0091] The first optical system 12 also adjusts the distance between the principal rays to satisfy the following formula.

[0092] a ≥ b (3) In formula (3), a represents the first distance between the principal rays of the first optical system 12 before adjustment, such as... Figure 10 As shown (the same applies below). In Figure 10 In the example shown, 'a' represents the center-to-center distance between adjacent first laser elements 111a and 111b. In formula (3), 'b' represents the distance between the main rays after adjustment by the first optical system 12, and also represents the distance between the first imaging points P1 located between the second imaging point P2 on the scanner (MEMS) and the retina, as shown in the figure. Figure 10 As shown (the same applies below).

[0093] For the second laser elements 112a, 112b and 112c and the third laser elements 113a, 113b and 113c, the same relationship as in formula (3) also holds.

[0094] In other words, when the distance between the principal rays of the second laser elements 112a, 112b, and 112c before adjustment by the first optical system 12 (i.e., the third distance) is a2, and the distance between the principal rays of the second laser elements 112a, 112b, and 112c at the first imaging point P1 after adjustment by the first optical system 12 is b2, the following formula holds true.

[0095] a2 ≥ b2 (4) Furthermore, when the distance between the principal rays of the third laser elements 113a, 113b, and 113c before adjustment by the first optical system 12 (i.e., the fourth distance) is a3, and the distance between the principal rays of the third laser elements 113a, 113b, and 113c at the first imaging point P1 after adjustment by the first optical system 12 is b3, the following formula holds true.

[0096] a3 ≥ b3 (5) In some embodiments, such as Figure 11 As shown, the first optical system 12 includes a first lens group 121, a second lens group 122, a third lens group 123, a beam combining prism 124 (i.e., a beam combining optical system), and a fourth lens group 125.

[0097] The first lens group 121 is a lens group disposed opposite to the first laser elements 111a, 111b, and 111c. The first lens group 121 includes at least one lens with positive refractive power. The first lens group 121 may also include at least one lens with negative refractive power. Figure 11 In the example shown, the first lens group 121 includes a first lens 1201, a second lens 1202, a third lens 1203, and a fourth lens 1204 arranged sequentially from the light source side. Laser beams emitted from the first laser elements 111a, 111b, and 111c are incident on the first lens group 121. The first lens group 121 adjusts the distance between the principal rays of the incident laser beams from the first laser elements 111a, 111b, and 111c according to formula (3), and emits a laser beam with the distance adjusted by the first lens group 121.

[0098] The second lens group 122 is a lens group disposed opposite to the second laser elements 112a, 112b, and 112c. The lens configuration of the second lens group 122 is the same as that of the first lens group 121. Laser beams emitted from the second laser elements 112a, 112b, and 112c are incident on the second lens group 122. The second lens group 122 adjusts the distance between the principal rays of the incident laser beams from the second laser elements 112a, 112b, and 112c according to formula (4), and emits a laser beam having the distance adjusted by the second lens group 122.

[0099] The third lens group 123 is a set of lenses arranged opposite to the third laser elements 113a, 113b, and 113c. The lens configuration of the third lens group 123 is the same as that of the first lens group 121. Laser beams emitted from the third laser elements 113a, 113b, and 113c are incident on the third lens group 123. The third lens group 123 adjusts the distance between the principal rays of the incident laser beams from the third laser elements 113a, 113b, and 113c according to formula (5), and emits a laser beam with the distance adjusted by the third lens group 123.

[0100] A beam combiner prism 124 is positioned on the emission side of the laser beam relative to the first lens group 121, the second lens group 122, and the third lens group 123. The beam combiner prism 124 receives the laser beams emitted from the first lens group 121, the second lens group 122, and the third lens group 123 respectively. The beam combiner prism 124 combines the incident laser beams from the lens groups 121, 122, and 123 and emits the combined laser beam.

[0101] The fourth lens group 125 is positioned relative to the beam combining prism 124 on the laser beam emission side. Figure 11 In the example shown, the fourth lens group 125 includes a fourth lens 1251, a fifth lens 1252, and a sixth lens 1253 arranged sequentially from the light source side. A laser beam emitted from the beam combiner prism 124 is incident on the fourth lens group 125. The fourth lens group 125 directs the incident laser beam toward the scanner 14.

[0102] A laser beam emitted from the fourth lens group 125 is incident on the scanner 14. The scanner 14 scans the incident laser beam. The laser beam scanned by the scanner 14 forms an image once at the first imaging point P1. The first imaging point P1 can be located at... Figure 1 The optical path between the second mirror 154 and the third mirror 155 is shown. The laser beam imaged at the first imaging point P1 diverges to the position of the third mirror 155, is reflected by the third mirror 155, and is imaged again at the second imaging point P2 on the retina.

[0103] In the first embodiment, the first lens group 121, the second lens group 122, and the third lens group 123 adjust the distance between the principal rays. In some embodiments, the distance b between the principal rays at the first imaging point P1 is set to be equal to or less than the distance a between the principal rays when the laser is first emitted.

[0104] Since the distance b between the principal rays at the first imaging point P1 is equal to or less than the distance a between the principal rays when the laser is first emitted, the distance between the principal rays at the second imaging point P2 is small enough to improve the image resolution.

[0105] In the first embodiment, the image resolution can be improved with a simple configuration by using a first optical system 12 that satisfies a ≥ b. Furthermore, the first optical system 12 that satisfies a ≥ b can be simply constructed from a lens with positive refractive power.

[0106] Second Embodiment The following is a description of the second embodiment of this application. Figure 12 As shown, in the second embodiment, the first lens 1201 of the first lens group 121 is a cylindrical lens (i.e., a beam shaping lens), with a convex surface relative to the vertical component of the laser beam, emitting at a maximum angle θv from the laser element 111a, and a planar surface relative to the horizontal component of the laser beam. The emission angle θv of the vertical component of the laser beam can be 27°. The emission angle θh of the horizontal component of the laser beam can be 12°. The second lens group 122 and the third lens group 123 have the same configuration as the first lens group 121.

[0107] like Figure 13 As shown, since laser element 111a is an edge-emitting laser, the emission angle of the laser beam is the maximum angle θv in the stacking direction (i.e., the vertical direction) of the p-type semiconductor layer 1101, active layer 1102, and n-type semiconductor layer 1103 constituting laser element 111a. On the other hand, in the direction perpendicular to the stacking direction (i.e., the horizontal direction), the emission angle of the laser beam is θh, which is smaller than the maximum emission angle θv. In other words, the shape of the laser beam emitted from the edge-emitting laser is approximately elliptical.

[0108] Elliptical laser beams need to be shaped into circles to avoid adversely affecting the image projection of other adjacent laser beams. If the ends of the elliptical laser beam along its major axis are cut off using a mask or similar method, the elliptical laser beam can be shaped into a circle. However, when a laser beam is partially cut in this way, the power used to emit the laser beam is wasted. Figure 14 As shown, a side-emitting laser requires a current greater than the oscillation threshold current Ith, and the magnitude of the oscillation threshold current Ith is greater than the magnitude of the oscillation threshold current of a vertical cavity surface-emitting laser (VCSEL).

[0109] Conversely, in the second embodiment, by using a cylindrical lens 1201, an elliptical laser beam can be shaped into a circular laser beam without being cut, thereby improving image resolution while saving power.

[0110] Third Embodiment The third embodiment of this application is described below. Figure 15 As shown, in the image projection device 1 of the third embodiment, laser elements 111a and 111b of the same wavelength are arranged in a non-parallel positional relationship, with the emission directions of laser beams of the same wavelength being non-parallel. Although Figure 15Only two first laser elements 111a and 111b are shown representatively, but Figure 15 The configuration can be applied to laser elements of other wavelengths.

[0111] The first optical system 12 in the third embodiment includes a collimating optical system 1200 disposed between laser elements 111a and 111b and a beam combiner prism 124 to collimate laser beams having the same wavelength but non-parallel emission directions. The first optical system 12 in the third embodiment includes a lens 1208 with positive refractive power, disposed opposite the beam combiner prism 124 on the emission side of the laser beam. That is, the collimating optical system 1200 is configured to be disposed opposite to laser elements 111a and 111b, which are located on the incident side of the lens 1208 with positive refractive power. The first optical system 12 in the third embodiment also includes a Gaussian beam filter 1209 disposed between the lens 1208 with positive refractive power and the scanner 14.

[0112] The collimating optical system 1200 includes a first collimating lens 1205 disposed opposite to the laser element 111a, a second collimating lens 1206 disposed opposite to the laser element 111b, and a half-reflecting mirror 1207. The optical axis of the second collimating lens 1206 is perpendicular to the optical axis of the first collimating lens 1205, and the half-reflecting mirror 1207 is disposed opposite to the first collimating lens 1205 and the second collimating lens 1206.

[0113] The first collimating lens 1205 collimates the laser beam emitted from laser element 111a and guides the collimated laser beam to the half-reflector 1207. The second collimating lens 1206 collimates the laser beam emitted from laser element 111b and guides the collimated laser beam to the half-reflector 1207. The half-reflector 1207 transmits the laser beam emitted from the first collimating lens 1205 to the beam combining prism 124. The half-reflector 1207 reflects the laser beam emitted from the second collimating lens 1206 to the beam combining prism 124. The laser beam from laser element 111a that passes through the half-reflector 1207 and the laser beam from laser element 111b that is reflected by the half-reflector 1207 are parallel to each other. Therefore, through the collimating optical system 1200, the laser beams from laser element 111a and laser element 111b (emitted in a non-parallel state) are collimated (i.e., parallelized).

[0114] like Figure 15 As shown, in the third embodiment, the first distance a between the principal rays of the first optical system 12 before adjustment as shown in formula (3) is the distance between the principal rays #1 of the laser beam from laser element 111a and the principal rays #2 of the laser beam from laser element 111b on the laser beam emission side of the semi-reflective mirror 1207.

[0115] The beam combining prism 124 combines the laser beams of laser elements 111a and 111b emitted from the semi-reflecting mirror 1207 and directs them toward the lens 1208 which has positive refractive power.

[0116] The lens 1208 with positive refractive power adjusts the distance between the main rays #1 and #2 of the laser beam emitted from the beam combining prism 124 according to formula (3), and emits the laser beam after the distance is adjusted by the lens 1208 to the Gaussian beam filter 1209.

[0117] The Gaussian beam filter 1209 shapes the laser beam emitted from the lens 1208 into a Gaussian beam and then emits the Gaussian-shaped laser beam to the scanner 14.

[0118] According to the third embodiment, even if laser beams of the same wavelength are not emitted collinearly, the first optical system 12 that satisfies formula (3) can be achieved. Therefore, according to the third embodiment, the resolution of the image is improved while the degree of design freedom is also increased.

[0119] Fourth embodiment The fourth embodiment of this application will now be described. Up to this point, an example of a first optical system 12 using at least one lens with positive refractive power to adjust the distance between principal rays has been described. Conversely, as... Figure 16 As shown, the first optical system 12 of the fourth embodiment employs a beam deflector 1210 to adjust the distance between the principal rays. The beam deflector 1210 is an optical element that adjusts the distance between the principal rays by deflecting at least one of adjacent principal rays of the same wavelength.

[0120] For ease of understanding, Figure 16 In the diagram, laser beams of the same wavelength adjacent to each other along the sub-scanning direction (i.e., the X direction) are shown as offset along the horizontal direction (i.e., the Y direction).

[0121] exist Figure 17 In the example shown, beam deflector 1210 is positioned opposite to adjacent laser elements 111a and 111b. Beam deflector 1210 refracts the laser beam emitted from laser element 111a and deflects the principal ray #1 of the laser beam from laser element 111a to the side of the principal ray #2 of the laser beam from laser element 111b.

[0122] exist Figure 17 In the example shown, beam deflector 1210 refracts the laser beam emitted from laser element 111b to deflect the principal ray #2 of the laser beam from laser element 111b to the side of the principal ray #1 of the laser beam from laser element 111a.

[0123] In some embodiments, Figure 17The beam deflector 1210 shown includes a common lens disposed on laser elements 111a and 111b. The common lens includes a plate-shaped first portion 1211 and a plate-shaped second portion 1212 connected to one end of the first portion 1211. The first portion 1211 is disposed opposite to laser element 111a and tilted relative to the laser emission direction of laser element 111a, such that the end of the first portion 1211 connected to the second portion 1212 is closer to laser element 111a than the other end of the first portion 1211. The second portion 1212 is disposed opposite to laser element 111b and tilted relative to the laser emission direction of laser element 111b, such that the end of the second portion 1212 connected to the first portion 1211 is closer to laser element 111b than the other end of the second portion 1212.

[0124] Figure 17 The beam deflector 1210 shown can be made of, for example, glass, resin, etc.

[0125] according to Figure 17 The beam deflector 1210 shown can effectively reduce the distance between two adjacent principal rays by deflecting two adjacent principal rays of the same wavelength to bring them closer together.

[0126] Thus, the first optical system 12 can reasonably satisfy formula (3) and effectively improve the resolution of the image.

[0127] Fifth embodiment The fifth embodiment of this application is described below. Figure 17 The example described is a beam deflector 1210 facing adjacent laser elements 111a and 111b, which refracts the laser beams of laser elements 111a and 111b to adjust the distance between the principal rays. Conversely, as... Figure 18 As shown, the beam deflector 1210 of the fifth embodiment is disposed opposite to one of the adjacent laser elements 111a and 111b. The beam deflector 1210 of the fifth embodiment is also disposed opposite to one of the adjacent laser elements 111b and 111c. Figure 18 In the example shown, beam deflector 1210 adjusts the distance between the principal rays by deflecting one of the adjacent principal rays of the same wavelength. If beam deflector 1210 is not positioned opposite laser element 111b, the laser beam from laser element 111b does not refract and passes between the two beam deflectors 1210.

[0128] The beam deflector 1210 of the fifth embodiment is made of a biaxial crystal, such as lithium niobate. Lithium niobate has a refractive index of 2.31475 for normal light and a refractive index of 2.22702 for abnormal light.

[0129] For example, if the thickness of the beam deflector 1210 is 0.518 mm, when the interval between adjacent laser elements 111a and 111b is 30 μm, the distance between the main rays just emitted from the beam deflector 1210 is reduced to 10 μm.

[0130] According to the fifth embodiment, the optical design of the beam deflector 1210 is simplified by not deflecting one of the adjacent principal rays, compared to the case where both adjacent principal rays are deflected.

[0131] Sixth Embodiment The sixth embodiment of this application is described below. In the sixth embodiment, the plurality of beam deflectors 1210 are the same as in the fifth embodiment, and are made of biaxial crystals. Each wavelength beam deflector 1210 is respectively positioned opposite to laser elements 111a, 112a, and 113a of that wavelength, and is connected to an actuator (such as a motor, not shown in the figures) for rotating the beam deflector 1210. Figure 19 As shown, a lens 1220 with positive refractive power is disposed between laser elements 111a, 112a, and 113a and beam deflector 1210. An actuator, under the control of the light source controller 18, rotates beam deflector 1210. By rotating beam deflector 1210, the tilt angle of beam deflector 1210 can be adjusted. By adjusting the tilt angle of beam deflector 1210, the parallel offset of the laser beam emitted from beam deflector 1210 can be adjusted. Figure 19 Box F4 shows an enlarged view of the beam deflector 1210.

[0132] Furthermore, such as Figure 19 As shown, the reflector 1240 is positioned relative to the beam deflector 1210 on the emission side of the laser beam. The reflector 1240 reflects the laser beam emitted from the beam deflector 1210.

[0133] Furthermore, such as Figure 19 As shown, lens 1220 and half-wave plates (λ / 2 plates) 1230 are positioned relative to laser elements 111b, 112b, and 113b on the laser beam emission side, and are not positioned opposite to beam deflector 1210. Half-wave plates 1230 change the polarization direction of the laser beam emitted from laser elements 111b, 112b, and 113b by 90°, and emit the laser beam with the changed polarization direction.

[0134] Furthermore, such as Figure 19As shown, a semi-reflecting mirror 1250 is positioned relative to a reflecting mirror 1240 on the reflecting side of the laser beam. The semi-reflecting mirror 1250 is positioned relative to a half-wave plate 1230 on the emitting side of the laser beam. The laser beam reflected from the reflecting mirror 1240 and the laser beam emitted from the half-wave plate 1230 are incident on the semi-reflecting mirror 1250. The semi-reflecting mirror 1250 reflects and emits the laser beam incident from the reflecting mirror 1240. The semi-reflecting mirror 1250 transmits and emits the laser beam incident from the half-wave plate 1230. Therefore, with the beam deflector 1210 adjusting the distance between adjacent principal rays of laser elements 111a and 111b, the laser beams from adjacent laser elements 111a and 111b are emitted in the same direction.

[0135] Furthermore, such as Figure 19 As shown, the reflector 1260 is positioned on the laser beam emission side relative to the semi-reflector 1250. The laser beam emitted from the semi-reflector 1250 is incident on the reflector 1260. The reflector 1260 reflects the incident laser beam to the scanner 14.

[0136] According to the sixth embodiment, since a rotatable beam deflector 1210 is used to adjust the parallel offset of the principal rays, the degree of freedom in adjusting the distance between the principal rays can be increased.

[0137] Seventh Embodiment The seventh embodiment of this application is described below. Figure 20 As shown, in the seventh embodiment, a plurality of beam deflectors 1210 are arranged opposite to each laser element 111a, 111b, 111c, 111d, 111e, and 111f of the same wavelength. The beam deflector 1210 can be a beam splitter. Figure 20 In the example shown, the relative positions of laser elements 111a, 111b, 111c, 111d, 111e, and 111f relative to the optical path connecting multiple beam deflectors 1210 are alternately switched along the optical path direction. The tilt angle of each beam deflector 1210 relative to the optical path is also alternately switched along the optical path direction.

[0138] Multiple beam deflectors 1210 reflect laser beams incident from laser elements 111a, 111b, 111c, 111d, 111e, and 111f, which are disposed opposite to each beam deflector 1210. In the plurality of beam deflectors 1210, any beam deflector 1210 disposed on the laser beam reflecting side relative to the other beam deflectors 1210 transmits laser beams reflected from the other beam deflectors 1210.

[0139] Depending on the thickness, refractive index, and incident position of the beam deflector 1210, the distance between the principal rays is formed between the principal rays of the laser beam reflected by the beam deflector 1210 and the principal rays of the laser beam transmitted through the same beam deflector 1210. Therefore, the distance between the principal rays of laser elements 111a, 111b, 111c, 111d, 111e, and 111f of the same wavelength can be adjusted.

[0140] like Figure 20 As shown, the coupling lens 1270 and the optical fiber 1280 are positioned relative to the beam deflector 1210 on the exit side of the laser beam. The laser beam, with the distance between the main rays adjusted by the beam deflector 1210, is incident on the coupling lens 1270. The coupling lens 1270 couples the incident laser beam to the incident surface of the optical fiber 1280. The optical fiber 1280 guides the incident laser beam from the coupling lens 1270 to the scanner 14.

[0141] According to the seventh embodiment, since the beam deflector 1210 adjusts the distance between the main rays in a manner different from that in the fourth to sixth embodiments, the flexibility of the design can be improved.

[0142] Eighth embodiment The eighth embodiment of this application is described below. Figure 21 As shown, the beam deflector 1210 of the eighth embodiment includes a lens with positive refractive power mounted on the drive circuit 110 (i.e., on the semiconductor chip).

[0143] According to the eighth embodiment, since the distance between the main rays can be adjusted by a simple configuration, the number of components and cost can be reduced.

[0144] Ninth Embodiment The ninth embodiment of this application will now be described. So far, examples have been described where laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) are end-emitting lasers. In contrast, in the ninth embodiment, laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) are VCSELs.

[0145] Each laser element 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) in the ninth embodiment has a semiconductor substrate, an active layer, and a reflector formed on the semiconductor substrate. The positional relationship between the semiconductor substrate, the active layer, and the reflector is not specifically limited. For example, the active layer and the semiconductor substrate may be sandwiched between two reflectors. Alternatively, the semiconductor substrate may be located outside the reflector.

[0146] The active layers of the laser elements 111a, 111b and 111c with a wavelength of 650nm (i.e., red) may contain aluminum gallium indium phosphide (AlGaInP).

[0147] The active layers of laser elements 112a, 112b and 112c with a wavelength of 520nm (i.e., green) and the active layers of laser elements 113a, 113b and 113c with a wavelength of 450nm (i.e., blue) may contain indium gallium nitride (InGaN).

[0148] The reflector can be a highly reflective distributed Bragg reflector (DBR). Because VCSELs with highly reflective distributed Bragg reflectors can select the desired wavelength and the wavelength variation is small, the color gamut can be effectively extended.

[0149] In the ninth embodiment, laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) emit laser beams perpendicular to the surface of the semiconductor chip. Unlike edge-emitting lasers that emit elliptical laser beams, laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) in the ninth embodiment emit circular laser beams.

[0150] Because the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) of the ninth embodiment have a lower oscillation threshold current compared to a side-emitting laser, power consumption can be reduced. Furthermore, similar to the first embodiment, the ninth embodiment also employs retinal projection to project the image onto the user's retina, allowing the user to see a clear image without requiring excessive light output. Therefore, the oscillation threshold current can be further reduced. For example, the oscillation threshold current can be maintained in the range of 0.4 mA to 3 mA, thereby reducing power consumption to 10 mW or even lower.

[0151] Furthermore, since the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) of the ninth embodiment have a smaller temperature variation range compared to the edge-emitting laser, they can emit laser beams stably. In addition, since the ninth embodiment employs a retinal projection method to reduce the oscillation threshold current, thermal interference between adjacent laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) can be effectively reduced, enabling more stable laser beam emission.

[0152] Furthermore, since the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) of the ninth embodiment are more suitable for two-dimensional arrays than side-emitting lasers, the distance between adjacent laser elements (i.e., the distance between the main beams) is easily adjustable. In some embodiments, such as Figure 22 As shown, the laser elements 111a, 111b and 111c of the ninth embodiment are not limited to being arranged along the sub-scanning direction (as shown in A), but can be arranged along a direction inclined to the sub-scanning direction (as shown in B), or can be arranged alternately (as shown in C and D).

[0153] Furthermore, since the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) of the ninth embodiment have a faster response speed than the side-emitting laser, high grayscale images can be projected. For example, the light source controller 18 can control the number of linear modulations of the laser elements 111 (a, b, c), 112 (a, b, c), and 113 (a, b, c) so that the grayscale of the image projected onto the user's retina is greater than or equal to 14 bits and less than or equal to 16 bits.

[0154] According to the ninth embodiment, by using a VCSEL, power consumption can be reduced and image resolution can be further improved. Furthermore, in embodiment nine, if a VCSEL is used... Figure 3-2 The linear modulation combined with pulse width modulation shown can further reduce power consumption.

[0155] Configuration example of the first optical system 12 The following describes specific examples of the application of this application. In the following examples, "Si" represents the ordinal number of the i-th surface increasing sequentially from the light source (laser element) side to the imaging point P1 side. The designation "first surface" or "1ST surface" indicates the surface on the light source side of the optical element (such as a lens), and the designation "second surface" or "2ND surface" indicates the surface on the imaging point side of the optical element. "Ri" represents the value of the central radius of curvature of the surface (mm). "Di" represents the distance (mm) between the i-th surface and the (i+1)-th surface on the optical axis. "Ndi" represents the refractive index value of the material of the optical element on the i-th surface at the d-line (wavelength of 587.6 nm). "νdi" represents the Abbe value of the material of the optical element on the i-th surface at the d-line. In the following examples, the Z direction is the optical axis direction of the first optical system 12.

[0156] The first optical system 12 in the following example includes an aspherical lens. The aspherical shape of the lens is defined by the following formula (6).

[0157] Z = C × h 2 / {1 + [1 - (1 + K) ×･C2 × h 2 ] 1 / 2} + ΣAn × h n (6) Where n is an integer greater than or equal to 3.

[0158] In formula (6), Z is the depth of the aspherical surface, C is the paraxial curvature, which is equal to 1 / R, h is the distance from the optical axis to the lens surface, K is the conic constant (second-order aspherical coefficient), and An is the nth-order aspherical coefficient.

[0159] First Example The following applies specific values ​​to Figure 23 A first example of the first optical system 12 shown will be described. Figure 23 A first optical system 12 is shown as a first example. Figure 23 The first optical system 12 shown is Figure 11 The first optical system 12 shown corresponds to this.

[0160] In the first example, the first optical system 12 corresponding to the optical paths of the first laser elements 111a, 111b, and 111c sequentially includes, starting from the light source side: a first lens L1 with positive refractive power in the paraxial region, its convex surface facing the light source side and the imaging point side, respectively; a second lens L2 with positive refractive power in the paraxial region, its convex surface facing the light source side and the imaging point side, respectively; a third lens L3 with negative refractive power in the paraxial region, its concave surface facing the light source side; a fourth lens L4 with negative refractive power in the paraxial region, its concave surface facing the light source side; a fifth lens L5 with positive refractive power in the paraxial region, its convex surface facing the light source side and the imaging point side, respectively; a sixth lens L6 with positive refractive power in the paraxial region; and a seventh lens L7 with positive refractive power in the paraxial region.

[0161] In the first example, the first laser elements 111a, 111b and 111c are edge-emitting lasers.

[0162] Table 1 shows the lens data for the first example. "INF" in Table 1 indicates infinity (the same applies below). Table 2 shows the aspherical coefficients of the first optical system 12.

[0163] Table 1

[0164] Table 2

[0165] The distance between the principal rays in the first example above is as follows: Figure 24 As shown. Figure 24As shown, according to the first example, the distance b between the principal rays at the first imaging point P1 is less than the distance a between the principal rays before the adjustment of the first optical system 12. Figure 24 As shown, according to the first example, the distance between the principal rays at the second imaging point P2 (i.e., the retina) is 5 μm, so that the vertical field of view (VFOV) reaches 1 arcminute (e.g., ...). Figure 8 As shown in the figure, this allows 4K high-resolution images to be projected onto the retina.

[0166] Second example The following applies specific values ​​to Figure 25 A second example of the first optical system 12 shown will be described.

[0167] The lens parameters corresponding to the first example are shown in Tables 3 and 4.

[0168] Table 3

[0169] Table 4

[0170] The distance between the principal rays in the second example above is as follows: Figure 26 As shown. In Figure 26 In this context, 'a' represents the distance between the principal rays of the first optical system 12 before adjustment. These principal rays correspond to two adjacent central laser elements, and the optical axis of the first optical system 12 is located between the two central laser elements. 'a1-1' represents the distance (i.e., the second distance) between the principal ray of a laser beam emitted from one of the two central laser elements and the principal ray of a laser beam emitted from a laser element adjacent to one of the two central laser elements and far from the optical axis (i.e., the third coherent light source). 'a1-1' represents the distance before adjustment of the first optical system 12 (see [reference]). Figure 25 a1-2 is the distance (i.e., the second distance) between the principal ray of the laser beam emitted from the other of the two central laser elements and the principal ray of the laser beam emitted from the laser element adjacent to the other of the two central laser elements and far from the optical axis (i.e., the third coherent light source). a1-2 is the distance before adjustment of the first optical system 12. Figure 26 As shown, distance a is less than distance a1-1 and distance a1-2.

[0171] Figure 26In the diagram, b represents the distance between the principal rays at the first imaging point P1 corresponding to the two central laser elements. b1-1 represents the distance between one of the two central laser elements and the principal ray at the first imaging point P1 corresponding to the laser element adjacent to that laser element. b1-2 represents the distance between the other of the two central laser elements and the principal ray at the first imaging point P1 corresponding to the laser element adjacent to that laser element.

[0172] like Figure 26 As shown, according to the second example, by making the distances a, a1-1, and a1-2 before adjustment by the first optical system 12 different, the distances b, b1-1, and b1-2 after adjustment by the first optical system 12 can be made equal to each other. In other words, according to the second example, the following relationships exist: a ≥ b, a1-1 ≥ b1-1, a1-2 ≥ b1-2, a ≠ a1-1 = a1-2, and b = b1-1 = b1-2. Therefore, the distance between the principal rays at the second imaging point P2 can be 5 μm.

[0173] According to the second example, by changing the lens parameters and the arrangement of the laser elements relative to the first example, the design freedom of the image projection device 1 is increased while achieving the same effect as the first example.

[0174] Third Example The following applies specific values ​​to Figure 27 A third example of the first optical system 12 shown is described. Figure 27 In the example, the beam deflector located on the light source side of the reflecting prism RP is not shown. In the third example, the optical path length of the beam deflector is set to 25 mm.

[0175] The lens parameters corresponding to the first example are shown in Tables 5 and 6.

[0176] Table 5

[0177] Table 6

[0178] In the third example, the distance between the principal rays is as follows: Figure 28 As shown. In Figure 28 In the diagram, 'a' represents the distance between the principal rays before adjustment by the first optical system 12; the beam deflector shifts the principal rays by 500 μm. For example... Figure 28 As shown, the third example also satisfies a ≥ b, making the distance between the principal rays at the second imaging point P2 5μm.

[0179] According to the third example, by making the lens parameters and optical elements different from those in the first example, the design freedom of the image projection device 1 is increased while achieving the same effect as the first example.

[0180] Fourth example The following applies specific values ​​to Figure 29 A fourth example of the first optical system 12 shown will be described. Figure 29 The first optical system 12 shown is Figure 15 The first optical system 12 shown corresponds to this. Figure 29 The collimating optical system 1200, which is set on the light source side of the reflecting prism RP, is not shown.

[0181] The lens parameters corresponding to the first example are shown in Table 7. In Table 7, RP represents the reflecting prism, and GF represents the Gaussian beam filter. Since the lens in the fourth example is a spherical lens, the aspherical coefficient is not shown.

[0182] Table 7

[0183] The distance between the principal rays in the fourth example is as follows: Figure 30 As shown. In Figure 30 In this context, 'a' represents the distance between the principal rays before adjustment by the first optical system 12, after the principal rays have been collimated by the collimating optical system. For example... Figure 30 As shown, in the fourth example, a ≥ b is satisfied, and the distance between the principal rays at the second imaging point P2 is 5 μm.

[0184] According to the fourth example, by making the lens parameters and optical elements different from those in the first example, the design freedom of the image projection device 1 is increased while achieving the same effect as the first example.

[0185] Fifth example The following applies specific values ​​to Figure 31 A fifth example of the first optical system 12 shown will be described. In this fifth example, the laser element is a VCSEL.

[0186] The lens parameters corresponding to the first example are shown in Tables 8 and 9.

[0187] Table 8

[0188] Table 9

[0189] The distance between the principal rays in the fifth example is as follows: Figure 32 As shown. Figure 32As shown, in the fifth embodiment, a ≥ b is satisfied, such that the distance between the principal rays at the second imaging point P2 is 5 μm.

[0190] According to the fifth example, by making the lens parameters and optical elements different from those in the first example, the design freedom of the image projection device 1 is increased while achieving the same effect as the first example.

[0191] In the description of the embodiments of this application, it is understood that terms such as “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” and “counterclockwise” should be interpreted as directions or positions as shown or illustrated in the accompanying drawings. These relative terms are used only to simplify the description of this application and do not indicate or imply that the mentioned devices or elements must have a specific orientation, or be constructed or operated in a specific orientation. Therefore, these terms should not be construed as limiting the scope of this application.

[0192] Furthermore, the terms "first," "second," etc., used herein are for descriptive purposes only and are not intended to indicate or imply relative importance or significance, nor to imply the number of technical features indicated. Therefore, a feature defined as "first" and "second" may include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise stated.

[0193] In the description of the embodiments of this application, unless otherwise stated or limited, the terms "installation", "connection", "coupling", etc. can be used extensively, and can be, for example, a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection or an electrical connection; it can also be a direct connection or an indirect connection through an intermediate structure; it can also be an internal connection between two components, which can be understood by those skilled in the art according to the specific circumstances.

[0194] In the embodiments of this application, unless otherwise stated or limited, a structure in which the first feature is located "above" or "below" the second feature can include embodiments in which the first feature and the second feature are in direct contact, or embodiments in which the first feature and the second feature are in contact not directly, but through an additional feature formed therebetween. Furthermore, "above," "on top of," or "on the second feature" can include embodiments in which the first feature is vertically or obliquely positioned above, above, or "on top of" the second feature, or simply means that the height of the first feature is greater than the height of the second feature; while "below," "below," or "at the bottom of" the second feature can include embodiments in which the first feature is vertically or obliquely positioned below, below, or "at the bottom of" the second feature, or simply means that the height of the first feature is less than the height of the second feature.

[0195] The foregoing description provides various embodiments and examples to implement different structures of this application. To simplify this application, certain elements and arrangements have been described above. However, these elements and arrangements are merely examples and are not intended to limit this application. Furthermore, reference numerals and / or reference letters may be repeated in different examples of this application. Such repetition is for simplification and clarity and does not relate to any relationship between different embodiments and / or arrangements. Moreover, this application provides examples of different processes and materials. However, those skilled in the art will understand that other processes and / or materials can also be applied.

[0196] The terms "an embodiment," "some embodiments," "exemplary embodiments," "example," "specific example," or "some examples" used in this specification mean that a particular feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. Therefore, the above phrases appearing in this specification do not necessarily refer to the same embodiment or example of this application. Furthermore, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0197] Any process or method described in a flowchart or otherwise herein can be understood to include one or more modules, code segments or portions of executable instructions for implementing specific logical functions or steps within that process. The scope of protection of the preferred embodiments of this application covers other implementations, wherein those skilled in the art will understand that the order of implementation of functions may differ from the order shown or discussed, including implementation in substantially the same order or in the reverse order.

[0198] The logic and / or steps described or illustrated in other ways herein, such as a specific list of executable instructions for implementing logical functions, may be implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, device, or apparatus (such as a computer-based system, a processor-included system, or other system capable of fetching and executing instructions from and to an instruction execution system, device, or apparatus). For the purposes of this specification, "computer-readable medium" can be any device suitable for including, storing, communicating, propagating, or transmitting programs for use by or in conjunction with an instruction execution system, device, or apparatus. More specific examples of computer-readable media include, but are not limited to: electronic connections (electronic devices) having one or more wires, portable computer casings (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), fiber optic devices, and compact disk read-only memory (CDROM). Furthermore, a computer-readable medium can even be paper or other suitable media on which programs can be printed. For example, paper or other suitable media can be optically scanned and then processed, if necessary, by editing, decryption or other suitable methods to obtain the program electronically, which can then be stored in computer memory.

[0199] It should be understood that the various parts of this application can be implemented by hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, similarly in another embodiment, the steps or methods can be implemented by one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing data signal logic functions, application-specific integrated circuits (ASICs) having appropriately combined logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0200] Those skilled in the art will understand that all or part of the steps in the exemplary methods described above can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium. When run on a computer, the program includes one or a combination of steps from the method embodiments of this application.

[0201] Furthermore, the functional units in the embodiments of this application can be integrated into one processing module, or they can exist physically separately, or two or more units can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. When the integrated module is implemented as a software functional module and sold or used as an independent product, the integrated module can be stored in a computer-readable storage medium.

[0202] The aforementioned storage media can be read-only memory, disk, optical disk, etc.

[0203] Although embodiments of this application have been shown and described, those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of this application. Changes, modifications, substitutions, and variations can be made to these embodiments without departing from the scope of this application.

Claims

1. An image projection device, characterized in that, include: The first light source is used to emit the first coherent light; The second light source is used to emit second coherent light with the same wavelength as the first coherent light; A first optical system is used to adjust a first distance between a first principal ray located at the center of the first coherent light emitted by the first light source and a second principal ray located at the center of the second coherent light emitted by the second light source; A scanner for scanning the first coherent light and the second coherent light after the first optical system has adjusted the first distance; as well as A second optical system is used to project an image onto the user's retina by illuminating the first and second coherent light scanned by the scanner onto the user's retina; The image projection device is configured as follows: a ≥ b; a is the first distance before the first optical system is adjusted, b is the first distance after the first optical system is adjusted, b is the first distance at the first imaging point, and the first imaging point is located between the scanner and the second imaging point on the retina.

2. The image projection device according to claim 1, characterized in that, The first optical system includes at least one lens with positive refractive power.

3. The image projection device according to claim 2, characterized in that, The first optical system also includes at least one lens with negative refractive power.

4. The image projection device according to claim 1, characterized in that, The first light source and the second light source are arranged adjacent to each other, and 'a' represents the first distance between the first light source and the second light source.

5. The image projection device according to claim 2, characterized in that, The first light source and the second light source are configured such that the emission direction of the first coherent light from the first light source is not parallel to the emission direction of the second coherent light from the second light source; The first optical system further includes a collimating optical system, which is configured to be opposite to the first light source and the second light source, which are located on the incident side of the lens with positive refractive power. The collimating optical system is used to collimate the non-parallel first coherent light and the second coherent light. as well as a is the first distance between the first principal ray and the second principal ray after the first coherent light and the second coherent light are collimated by the collimating optical system.

6. The image projection device according to claim 5, characterized in that, The first optical system further includes a Gaussian beam filter disposed between the lens with positive refractive power and the scanner to shape the first coherent light and the second coherent light into a Gaussian beam.

7. The image projection device according to any one of claims 1-3, characterized in that, The first optical system includes a beam deflector for deflecting at least one of the first principal ray and the second principal ray.

8. The image projection device according to claim 7, characterized in that, The first light source and the second light source are arranged adjacent to each other; and The beam deflector is positioned opposite the first light source and refracts the first coherent light to deflect the first principal ray toward the second principal ray.

9. The image projection device according to claim 8, characterized in that, The beam deflector is positioned opposite the second light source and refracts the second coherent light to deflect the second principal ray toward the first principal ray.

10. The image projection device according to claim 7, characterized in that, The beam deflector is made of a biaxial crystal.

11. The image projection device according to claim 7, characterized in that, The beam deflector includes a common lens disposed on the first light source and the second light source.

12. The image projection device according to claim 7, characterized in that, The beam deflector includes a beam splitter.

13. The image projection device according to claim 1, characterized in that, The first light source and the second light source are arranged adjacent to each other; The image projection device further includes a third light source, which is arranged adjacent to the second light source. The distance between the third light source and the optical axis of the first optical system is greater than the distance between the first light source and the second light source and the optical axis of the first optical system. The third light source is used to emit third coherent light with the same wavelength as the first coherent light and the second coherent light. The first optical system is also used to adjust a second distance between the second principal ray and the third principal ray located at the center of the third coherent light emitted by the third light source; The scanner is also used to scan a third coherent light having the second distance after the first optical system has been adjusted; The second optical system is further configured to illuminate the retina with the third coherent light scanned by the scanner; and The image projection device is also configured to: a1 ≥ b1, a1 ≠ a, b1 = b; Where a1 is the second distance before the first optical system is adjusted, b1 is the second distance after the first optical system is adjusted, and b1 is the second distance at the first imaging point.

14. The image projection device according to claim 1, characterized in that, The image projection device also includes: A fourth light source is used to emit fourth coherent light with a wavelength different from that of the first coherent light and the second coherent light; The fifth light source is used to emit fifth coherent light with the same wavelength as the fourth coherent light; A sixth light source is configured to emit a sixth coherent light with wavelengths different from the first coherent light, the second coherent light, the fourth coherent light, and the fifth coherent light; and The seventh light source is used to emit seventh coherent light with the same wavelength as the sixth coherent light; The first optical system includes a beam combining optical system, which is used to combine the fourth coherent light emitted from the fourth light source, the fifth coherent light emitted from the fifth light source, the sixth coherent light emitted from the sixth light source, and the seventh coherent light emitted from the seventh light source with the first coherent light and the second coherent light. The first optical system is also used to adjust a third distance between the fourth principal ray located at the center of the fourth coherent light and the fifth principal ray located at the center of the fifth coherent light; The first optical system is also used to adjust a fourth distance between the sixth principal ray located at the center of the sixth coherent light and the seventh principal ray located at the center of the seventh coherent light. The scanner is also used to scan the fourth and fifth coherent lights, which are adjusted by the first optical system to have the third distance, and the sixth and seventh coherent lights, which are adjusted by the first optical system to have the fourth distance. The second optical system is further configured to illuminate the retina with the fourth, fifth, sixth, and seventh coherent light scanned by the scanner; and The image projection device is also configured to: a2 ≥ b2, a3 ≥ b3; Wherein, a2 is the third distance before the adjustment of the first optical system, b2 is the third distance after the adjustment of the first optical system, and b2 is the third distance at the first imaging point; a3 is the fourth distance before the adjustment of the first optical system, b3 is the fourth distance after the adjustment of the first optical system, and b3 is the fourth distance at the first imaging point.

15. The image projection device according to claim 14, characterized in that, The first optical system further includes: At least one lens with positive refractive power is configured to be positioned opposite to the first light source and the second light source, which are located on the incident side of the beam combining optical system. At least one lens with positive refractive power is configured to be positioned opposite the fourth and fifth light sources, which are located on the incident side of the beam combining optical system; and At least one lens with positive refractive power is configured to be positioned opposite the sixth light source and the seventh light source, which are located on the incident side of the beam combining optical system.

16. The image projection device according to claim 15, characterized in that, The first optical system further includes: At least one lens with negative refractive power is configured to be positioned opposite to the first light source and the second light source, which are located on the incident side of the beam combining optical system. At least one lens with negative refractive power is configured to be positioned opposite the fourth and fifth light sources, which are located on the incident side of the beam combining optical system; and At least one lens with negative refractive power is configured to be positioned opposite the sixth light source and the seventh light source, which are located on the incident side of the beam combining optical system.

17. The image projection apparatus according to any one of claims 14-16, characterized in that, The first optical system further includes at least one lens with positive refractive power, disposed between the beam combining optical system and the scanner.

18. The image projection device according to claim 17, characterized in that, The first optical system further includes at least one lens with negative refractive power, disposed between the beam combining optical system and the scanner.

19. The image projection device according to claim 1, characterized in that, Both the first light source and the second light source are edge-emitting lasers.

20. The image projection device according to claim 2, characterized in that, Both the first and second light sources are edge-emitting lasers, and The at least one lens with positive refractive power includes a beam shaping lens for shaping the first coherent light emitted from the first light source and the second coherent light emitted from the second light source into circles, respectively.

21. The image projection device according to claim 20, characterized in that, The beam-shaping lens is a cylindrical lens.

22. The image projection device according to claim 1, characterized in that, Both the first light source and the second light source are vertical cavity surface-emitting lasers.

23. The image projection device according to claim 22, characterized in that, The first light source and the second light source are arranged adjacent to each other in a direction that is inclined relative to the sub-scanning direction of the scanner.

24. The image projection device according to claim 1, characterized in that, The scanner scans the first coherent light and the second coherent light using the Lissajous scanning method.

25. The image projection device according to claim 1, characterized in that, Also includes: A gaze direction detector is used to detect the direction of the user's gaze as the image is projected. as well as An optical system controller is used to control the second optical system based on the line-of-sight direction detected by the line-of-sight direction detector.

26. The image projection device according to claim 25, characterized in that, It also includes a light source controller for controlling the first light source to emit the first coherent light and the second light source to emit the second coherent light.

27. The image projection device according to claim 26, characterized in that, The light source controller is also used to control the linear modulation grayscale number of the first light source and the linear modulation grayscale number of the second light source, so that the grayscale of the image projected onto the retina is greater than or equal to 14 bits and less than or equal to 16 bits.

28. The image projection device according to claim 26 or 27, characterized in that, The light source controller controls the first light source to emit the first coherent light and the second light source to emit the second coherent light by a combination of linear modulation and pulse width modulation.

Images