Device for reducing laser speckles and projection system
By using semi-transparent half-mirror, half-wave plate, reflector and prism in the laser projection system, the laser speckle problem is solved, and the image quality of the projection system is significantly improved and resolution.
Patent Information
- Application Number
- CN202323617731.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-27
- Publication Date
- 2025-02-11
- Estimated Expiration
- 2033-12-27
AI Technical Summary
In projection equipment using tri-color laser light sources, laser speckle seriously affects the image display quality and resolution of the projection system.
By introducing semi-transparent half-mirror, half-wave plate, reflector and prism into the laser beam, the reflection, transmission and phase delay processing are performed respectively to form a beam of orthogonal polarization state, and totally reflect through the prism, and finally the beam is projected toward Projection screen.
This solution effectively reduces laser speckle and improves the image display quality and resolution of the projection system.
Smart Images
Figure CN222461813U_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the field of laser technology, and in particular to a device and a projection system for reducing laser speckle. Background Art
[0002] Because laser has the characteristics of good monochromaticity, strong directionality and high brightness, in the projection system using laser as the light source, the projected picture has the advantages of realistic colors, clear images and suitability for large-screen display.
[0003] However, when a projection device using a three-color laser light source is used over a large area, the projection screen of the laser light source will produce laser speckle due to the coherence of the laser, which seriously affects the image display quality and resolution of the projection system. Summary of the invention
[0004] In view of this, the embodiments of the present disclosure provide a device for reducing laser speckle and a projection system to solve the technical problem of laser speckle existing in laser projection images in the prior art.
[0005] To achieve the above objectives, the technical solution adopted by the present disclosure is:
[0006] One aspect of an embodiment of the present disclosure provides a device for reducing laser speckle, the device comprising: a laser for generating laser light; a semi-transparent and semi-reflective mirror for reflecting a portion of the laser light and transmitting another portion of the laser light; a half-wave plate for phase-delaying a light beam transmitted by the semi-transparent and semi-reflective mirror; a reflective mirror for reflecting the light beam emitted by the half-wave plate; and a prism for totally reflecting the light beam transmitted by the semi-transparent and semi-reflective mirror and the light beam reflected by the reflective mirror so as to project the light beam onto a projection screen.
[0007] In one embodiment, the device further comprises a condenser and a light diffuser which are sequentially arranged between the prism and the projection screen.
[0008] In one embodiment, the device further comprises a fly-eye lens disposed between the prism and the condenser lens.
[0009] In one embodiment, the transmittance and reflectance of the semi-transparent and semi-reflective mirror are both 50%.
[0010] In one embodiment, the condenser is a convex lens.
[0011] In one embodiment, the light homogenizer includes a scattering plate and a light homogenizing integrator rod which are sequentially arranged behind the condenser.
[0012] In one embodiment, the light diffuser is a light diffuser integrator rod.
[0013] In one embodiment, the prism is a right angle prism.
[0014] In one embodiment, the laser is a three-primary color laser.
[0015] One aspect of an embodiment of the present disclosure provides a projection system for reducing laser speckle, characterized in that it includes a projection device and a projection screen, wherein the projection device includes the device for reducing laser speckle in the above technical solution.
[0016] Compared with the prior art, the disclosed embodiment has the following beneficial effects: by reflecting a part of the laser and transmitting the other part and then reflecting it after phase delay, the two light beams obtained are in orthogonal polarization states, so that the two light beams are projected onto the projection screen after being totally reflected through a prism, thereby reducing laser speckle. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0018] Figure 1 is a schematic diagram of a device for reducing laser speckle provided by an embodiment of the present disclosure;
[0019] Figure 2 is a schematic diagram of another device for reducing laser speckle provided by an embodiment of the present disclosure;
[0020] Figure 3 It is a schematic diagram of a projection system for reducing laser speckle provided by an embodiment of the present disclosure. DETAILED DESCRIPTION
[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not used to limit the present disclosure.
[0022] The device for reducing laser speckle and the projection system according to the embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.
[0023] Figure 1 is a circuit diagram of a device for reducing laser speckle provided by an embodiment of the present disclosure; Figure 1 To describe the device for reducing laser speckle provided by an embodiment of the present disclosure.
[0024] like Figure 1As shown, an embodiment of the present disclosure provides a device for reducing laser speckle, which includes: a laser 101, used to generate laser; a semi-transparent and semi-reflective mirror 102, used to reflect a part of the laser and transmit another part of the laser; a half-wave plate 103, used to phase-delay a light beam transmitted by the semi-transparent and semi-reflective mirror; a reflector 104, used to reflect the light beam emitted by the half-wave plate; and a prism 105, used to totally reflect the light beam transmitted by the semi-transparent and semi-reflective mirror and the light beam reflected by the reflector, so as to project them onto a projection screen.
[0025] Semi-transparent and semi-reflective mirror is also called beam splitter, beam splitter, semi-reflective half lens. Semi-transparent and semi-reflective mirror can be formed by coating a semi-reflective film on optical glass. Coating a film layer on optical glass can change the original transmission and reflection ratio of the incident light beam. For example, by coating a film layer, the transmittance can be increased to increase the light intensity, and the reflection can be increased to reduce the light intensity. According to specific needs, the required reflectivity can be selected for the film layer, which can be relatively low or relatively high.
[0026] In the disclosed embodiment, the film layer on the semi-transparent and semi-reflective mirror makes the transmittance and reflectance of the semi-transparent and semi-reflective mirror both 50%. When the light beam passes through the film layer on the semi-transparent and semi-reflective mirror, the intensity of the light transmitted and the intensity of the light reflected back each account for 50%. The lens of the semi-transparent and semi-reflective mirror in the disclosed embodiment has the characteristic of low absorption.
[0027] A prism is a polyhedron made of a transparent material. The transparent material may be glass or crystal, but is not limited thereto. Prisms are widely used in optical instruments. In periscopes, binoculars and other instruments, prisms can be used to change the direction of light, thereby adjusting the imaging position of the instrument. In the embodiment of the present disclosure, the function of the prism is to change the direction of light and to perform total reflection on the incident light beam. The prism of the embodiment of the present disclosure can use a right-angle prism as a total reflection prism.
[0028] A half-wave plate is a birefringent crystal with a certain thickness. When normally incident light passes through the half-wave plate, the phase difference between ordinary light (o light) and extraordinary light (e light) is equal to π or an odd multiple of π. After passing through the half-wave plate, the light beam can change its original phase, and its phase change value is π or an odd multiple of π.
[0029] In the related art, semiconductor lasers have polarization characteristics, common red light is P light, and blue-green light is S light. In the technical solution of the embodiment of the present disclosure, after the three primary color lasers pass through the semi-transparent and semi-reflective mirror, part of the light is reflected to the prism, and the other part of the light passes through the semi-transparent and semi-reflective mirror, passes through the half-wave plate to generate phase delay, and then passes through the reflector to the prism. Since the light beam reflected by the semi-transparent and semi-reflective mirror and the light beam reflected by the reflector are in orthogonal polarization states, speckle can be reduced.
[0030] In one embodiment, the device further comprises a condenser 106 and a light diffuser 108 which are sequentially arranged between the prism and the projection screen.
[0031] Specifically, the condenser can be a convex lens, which is used to superimpose the light beams. The superimposed light beams are homogenized by a homogenizer and then emitted to the projection screen.
[0032] like Figure 2 As shown, in one embodiment of the present disclosure, the device further includes a fly-eye lens 109 disposed between the prism and the condenser. The fly-eye lens can improve the uniformity of the light beam and increase the phase randomness.
[0033] The compound eye lens is composed of a series of sub-lenses to form a spatial microlens array. In the embodiment of the present disclosure, the compound eye lens includes two microlens arrays, wherein the second microlens array is located on the focal plane of the first microlens array. Figure 2 As shown, the light beam is projected onto the first microlens array in parallel, and is imaged onto the second microlens array through each small lens of the first microlens array, forming multiple light source images on the second microlens array. The condenser superimposes the multiple image beams to obtain a uniform light beam. In this process, the incident light is divided into light emitted by multiple sub-wave sources, and the uniformity of the light emitted by each sub-wave source is necessarily better than the uniformity of the original incident light. Because of the mutual superposition of sub-wave sources in symmetrical positions, the slight unevenness can be further compensated.
[0034] In one embodiment of the present disclosure, the light homogenizer may be a light homogenizing integrator rod. After the parallel light beam is focused by a condenser lens at the center of the incident end face of the light homogenizing integrator rod, it undergoes multiple total reflections in the integrator rod. The light beams after different reflection times will form many secondary light sources at different positions of the incident end face. These secondary light sources are superimposed on the exit end face of the integrator rod to form a light spot with good uniformity.
[0035] In one embodiment of the present disclosure, the light homogenizer includes a scattering plate and a light homogenizing integrator rod which are sequentially arranged after the condenser. The scattering plate is a binary optical element based on Fourier optics, designed with the aid of computational imaging, and processed by nano-scale photolithography technology. It has the advantages of designable beam shape, small size and light weight, unique dispersion performance, wide bandwidth, and large field of view. The scattering plate is arranged before the light homogenizing integrator rod, so that the laser spot emitted from the light homogenizing integrator rod can be more uniform, thereby making the laser spot on the projection screen more uniform.
[0036] In one embodiment, the laser is a three-primary color laser. The three primary color lasers of red, green and blue emitted by the laser can be processed by the device for reducing laser speckle in the embodiment of the present disclosure and then projected onto the projection screen.
[0037] like Figure 3As shown, an embodiment of the present disclosure provides a projection system for reducing laser speckle, including a projection device and a projection screen 302, wherein the projection device includes the device for reducing laser speckle in the above technical solution and a lens 301.
[0038] like Figure 3 As shown, in the projection system for reducing laser speckle provided by the embodiment of the present disclosure, the laser 101 generates laser light; the semi-transparent and semi-reflective mirror 102 reflects a part of the laser light and transmits another part of the laser light; the half-wave plate 103 phase-retards the light beam transmitted by the semi-transparent and semi-reflective mirror; the reflector reflects the light beam emitted by the half-wave plate; the prism 105 totally reflects the light beam transmitted by the semi-transparent and semi-reflective mirror and the light beam reflected by the reflector. The condenser 106 superimposes the light beams obtained after the total reflection of the prism, and the superimposed light beams are homogenized by the scattering plate 107 and the integral homogenizing rod 109, and then emitted to the projection screen 302 through the lens 301.
[0039] In another projection system for reducing laser speckle provided by an embodiment of the present disclosure, a laser 101 generates laser light; a semi-transparent and semi-reflective mirror 102 reflects a portion of the laser light and transmits another portion of the laser light; a half-wave plate 103 phase-retards the light beam transmitted by the semi-transparent and semi-reflective mirror; a reflector reflects the light beam emitted by the half-wave plate; and a prism 105 totally reflects the light beam transmitted by the semi-transparent and semi-reflective mirror and the light beam reflected by the reflector. A fly-eye lens 109 homogenizes the light beam totally reflected by the prism and increases the phase uniformity, and a condenser 106 superimposes the light beams emitted by the fly-eye lenses, and the superimposed light beam is homogenized by a scattering plate 107 and an integral homogenizing rod 109, and then emitted to a projection screen 302 through a lens 301.
[0040] In another projection system for reducing laser speckle provided by an embodiment of the present disclosure, a laser 101 generates laser light; a semi-transparent and semi-reflective mirror 102 reflects a portion of the laser light and transmits another portion of the laser light; a half-wave plate 103 phase-retards the light beam transmitted by the semi-transparent and semi-reflective mirror; a reflector reflects the light beam emitted by the half-wave plate; and a prism 105 totally reflects the light beam transmitted by the semi-transparent and semi-reflective mirror and the light beam reflected by the reflector. A fly-eye lens 109 homogenizes the light beam totally reflected by the prism and increases the phase uniformity, and a condenser 106 superimposes the light beams obtained after the total reflection of the prism, and the superimposed light beams are homogenized by an integral homogenizing rod and then emitted to a projection screen 302 through a lens 301.
[0041] According to the device and projection system for reducing laser speckle provided by the embodiments of the present disclosure, laser speckle can be reduced by reflecting a portion of the laser and transmitting the other portion, then reflecting it after phase delay, so that the two light beams obtained are in orthogonal polarization states. The two light beams are then totally reflected through a prism and projected onto a projection screen.
[0042] The above are only preferred embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.
Claims
1. A device for reducing laser speckle, characterized in that: The device comprises: Laser, used to generate laser light; A semi-transparent and semi-reflective mirror, used for reflecting a part of the laser light and transmitting another part of the laser light; A half-wave plate, used for phase-delaying the light beam transmitted by the semi-transparent and semi-reflective mirror; A reflector, used for reflecting the light beam emitted by the half-wave plate; The prism is used to totally reflect the light beam transmitted by the semi-transparent and semi-reflective mirrors and the light beam reflected by the reflective mirror, so as to project them onto a projection screen.
2. The device for reducing laser speckle according to claim 1, characterized in that: The device also includes a condenser and a light homogenizer which are sequentially arranged between the prism and the projection screen.
3. The device for reducing laser speckle according to claim 2, characterized in that: The device also includes a fly-eye lens disposed between the prism and the condenser.
4. The device for reducing laser speckle according to claim 2, characterized in that: The transmittance and reflectance of the semi-transparent and semi-reflective mirror are both 50%.
5. The device for reducing laser speckle according to claim 2, characterized in that: The condenser is a convex lens.
6. The device for reducing laser speckle according to claim 2, characterized in that: The light homogenizer comprises a scattering plate and a light homogenizing integrator rod which are sequentially arranged behind the condenser.
7. The device for reducing laser speckle according to claim 2, characterized in that: The light homogenizer is a light homogenizing integrator rod.
8. The device for reducing laser speckle according to claim 1, characterized in that: The prism is a right-angle prism.
9. The device for reducing laser speckle according to claim 1, characterized in that: The laser is a three-primary color laser.
10. A projection system for reducing laser speckle, characterized in that: The invention comprises a projection device and a projection screen, wherein the projection device comprises the device for reducing laser speckle according to any one of claims 1 to 9.