Light path system for eliminating stray light of projector

Abstract

A light path system for eliminating stray light of a projector is suitable for the technical field of projector application and solves the problem that in an existing projector light path, the distance between a reflective mirror and a field lens is too short, so that stray light generated by total reflection of the field lens is reflected by the reflective mirror and then ghosts are generated on a projection plane. The system comprises heat insulation glass, an LCD, a field lens, a reflective mirror and a projection lens. The LCD illumination collimation system, the heat insulation glass, the LCD and the field lens are coaxially arranged; after light rays emitted by the light source pass through the heat insulation glass, the LCD and the field lens by the LCD illumination collimation system, stray light rays totally reflected by the field lens are reflected by the reflective mirror and enter the projection lens, and the projection lens images a picture displayed by the LCD. By changing the angle of the reflector and the inclination angle of the illumination system, stray light totally reflected by the field lens is reflected to the mechanism at a characteristic angle to be absorbed and eliminated under the condition that the optical path is ensured to be constant.

Description

Technical Field

[0001] The utility model relates to an optical path system for eliminating stray light of a projector, and is suitable for the application field of the projector. Background Art

[0002] In the current market, single-chip LCD projectors must use short focal length lenses to achieve short throw ratios. Since the use of short focal length lenses will inevitably reduce the back working distance of the lens, in the horizontal structure of the projector's optical path, the inclination angle of the reflector in the optical path is 45°. Because the distance between the reflector and the field lens is too close, the stray light generated by the total reflection of the field lens will be reflected by the reflector and produce ghost images on the projection plane.

[0003] In view of the current technical shortcomings, the utility model adopts an optical path to eliminate stray light from the projector. By changing the angle of the reflector and the inclination angle of the lighting system, the stray light totally reflected by the field mirror is reflected to the mechanism at a characteristic angle for absorption and elimination while ensuring a constant optical path. Utility Model Content

[0004] The utility model provides an optical path system for eliminating stray light of a projector to solve the problem that in the optical path of an existing projector, the distance between the reflector and the field lens is too close, resulting in stray light generated by total reflection of the field lens generating ghost images on the projection plane after being reflected by the reflector.

[0005] An optical path system for eliminating stray light of a projector, the optical path system comprising an LCD lighting collimation system, heat-insulating glass, an LCD, a field lens, a reflector and a projection lens; the LCD lighting collimation system, the heat-insulating glass, the LCD and the field lens are coaxially arranged;

[0006] The LCD lighting collimation system passes the light emitted by the light source through the heat-insulating glass, LCD and field lens, and the stray light totally reflected by the field lens is reflected by the reflector into the projection lens, and the projection lens forms an image on the LCD display;

[0007] The difference θ between the tilt angle β of the reflector and the angle of the stray light reflected by the field mirror before and after the change satisfies the formula: β-45°=θ; the stray light after the change of β value is finally absorbed and eliminated by the projector shell.

[0008] Beneficial effects of the utility model:

[0009] The utility model adopts an optical path system for eliminating stray light of a projector, and by changing the angle of a reflector and the inclination angle of an illumination system, the stray light totally reflected by a field mirror is reflected to a mechanism at a characteristic angle under the condition of ensuring a constant optical path, so as to be absorbed and eliminated.

[0010] The optical path system of the utility model can eliminate stray light on the projection screen and improve the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of stray light that is totally reflected by the field mirror without adjusting the β value.

[0012] Figure 2 Schematic diagram of stray light reflected by the field mirror after adjusting the β value.

[0013] In the figure, 1. LCD lighting collimation system, 1-1. LED light source, 1-2. Light funnel, 1-3. Fresnel lens, 2. Heat-insulating glass, 3. LCD, 4. Field lens, 5. Reflector, 6. Projection lens, 7. Stray light totally reflected by the field lens, 8. Stray light after changing the β value. DETAILED DESCRIPTION

[0014] Combination Figure 1 and Figure 2 The present embodiment is described as an optical path system for eliminating stray light of a projector, the optical path system comprising an LCD lighting collimation system 1, a heat-insulating glass 2, an LCD 3, a field lens 4, a reflector 5 and a projection lens 6; the LCD lighting collimation system 1, the heat-insulating glass 2, the LCD 3 and the field lens 4 are coaxially arranged;

[0015] like Figure 1 As shown, in this embodiment, the LCD lighting collimation system 1 collimates the light emitted by the light source and makes it incident on the LCD 3. This system includes, but is not limited to, an LED light source 1-1, a light funnel 1-2, a Fresnel lens 1-3 or an LED, a condenser, and a Fresnel lens.

[0016] The heat-insulating glass 2 polarizes the circularly polarized light emitted by the collimating system, selects the light in the S or P direction to pass through, and has a certain distance from the LCD 3 to have heat dissipation space for it; the LCD 3 is the object plane of the projection screen; the field lens 4 is a Fresnel lens, which converges the collimated light and passes through the lens more effectively; the reflector 5 changes the propagation direction of the converged light of the field lens; the projection lens 6 is used to image the screen displayed by the LCD 3; the stray light 7 fully reflected by the field lens is fully reflected when the light enters the field lens 4, and then is reflected by the reflector 5 and enters the field lens for internal total reflection, and then is emitted into the projection screen to become a ghost image; by changing the reflection angle of the inclination angle β of the reflector 5, the stray light 7 fully reflected by the field lens is reflected by the reflector 5 and no longer enters the field lens 4 for total reflection before entering the projection lens 6.

[0017] In this embodiment, a polarizing film with an off-axis effect is attached to the surface of the heat-insulating glass 2, and the distance between the heat-insulating glass 2 and the Fresnel lenses 1-3 is 1-20 mm. A heat dissipation space with a distance of 1-25 mm is provided between the LCD 3 and the heat-insulating glass 2.

[0018] In this embodiment, the tilt angle β of the reflector 5 and the change θ corresponding to the incident angle of the stray light incident on the reflector after the angle of the reflector 5 is changed satisfy the formula: β-45°=θ; the tilt angle β and α satisfy the formula: 2*(β-45°)=α; the stray light 8 after the change of β value is finally absorbed and eliminated by the projector shell. α is the rotation angle of the normal of the LCD illumination collimation system 1, LCD 3 and field lens 4.

[0019] The difference θ before and after the angle of the stray light 7 totally reflected by the field mirror entering the reflector is changed (the change in the incident angle of the stray light ray entering the reflector corresponding to the change in the angle of the stray light ray entering the reflector after the angle of the reflector is changed) is: θ=θ2-θ1=β-45°; θ1 is the angle at which the stray light ray 7 totally reflected by the field mirror enters the reflector 5 before the change, and θ2 is the incident angle of the stray light ray 8 entering the reflector 5 after the change.

[0020] The optical path system described in this embodiment adjusts the reflector angles β and α to increase the value of θ, so that the field mirror totally reflects the stray light 7 onto the projector housing to absorb it.

[0021] The optical path system described in this embodiment is applied to a specific example of eliminating stray light from a projector, and the design parameters are as follows:

[0022] The LCD lighting collimation system 1 is composed of an LED light source 1-1, a light funnel 1-2, and a Fresnel lens 1-3. The rotation angle α is 10°. Furthermore, the light emitting size of the LED light source 1-1 is 10*12mm. 2 The light funnel 1-2 has a small opening size of 11*13mm 2 , the maximum opening size is

[0023] 44*78mm 2 , height is 43mm, the focal length of the Fresnel lens 1-3 is f=60mm, and the size is 45*80mm 2 The surface of the insulating glass 2 is affixed with a polarizing film with an off-axis effect, the size of which is 45*80mm 2 , the distance from the Fresnel lenses 1-3 is 5 mm; the size of the LCD 3 is 43*77 mm 2 , the distance from the insulating glass 2 is 10mm; the field lens 4 is a Fresnel lens, with a focal length of f = 90mm and a size of 45*80mm 2The inclination angle β of the reflector 5 is 50° and the size is 54*89mm 2 ; The projection lens 6 has a focal length of 110 mm.

[0024] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0025] The above-mentioned embodiments only express several implementation methods of the utility model, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. An optical path system for eliminating stray light of a projector, the optical path system comprising an LCD lighting collimation system (1), a heat-insulating glass (2), an LCD (3), a field lens (4), a reflector (5) and a projection lens (6); wherein: The LCD lighting collimation system (1), the heat-insulating glass (2), the LCD (3) and the field lens (4) are coaxially arranged; The LCD lighting collimation system (1) passes the light emitted by the light source through the heat-insulating glass (2), the LCD (3) and the field lens (4), and the stray light (7) totally reflected by the field lens is reflected by the reflector (5) and enters the projection lens (6), and the projection lens (6) forms an image of the picture displayed by the LCD (3); The difference θ between the tilt angle β of the reflector (5) and the angle of the stray light (7) totally reflected by the field mirror before and after the incident on the reflector (5) satisfies the formula: β-45°=θ; the stray light after the β value is changed is finally absorbed and eliminated by the projector shell.

2. The optical path system for eliminating stray light of a projector according to claim 1, characterized in that: The inclination angles β and α of the reflector (5) satisfy the formula: 2*(β-45°)=α; The α is the rotation angle of the normal line of the LCD illumination collimation system (1), LCD (3) or field lens (4).

3. The optical path system for eliminating stray light of a projector according to claim 1, characterized in that: The LCD lighting collimation system (1) is composed of an LED light source (1-1), a light funnel (1-2) and a Fresnel lens (1-3) or is composed of an LED light source, a condenser and a Fresnel lens.

4. The optical path system for eliminating stray light of a projector according to claim 3, characterized in that: A polarizing film with an off-axis effect is attached to the surface of the heat-insulating glass (2), and the distance between the heat-insulating glass (2) and the Fresnel lenses (1-3) is 1-20 mm.

5. The optical path system for eliminating stray light of a projector according to claim 4, characterized in that: The distance between the heat-insulating glass (2) and the Fresnel lenses (1-3) is 5 mm.

6. The optical path system for eliminating stray light of a projector according to claim 1, characterized in that: A heat dissipation space with a distance of 1-25 mm is provided between the LCD (3) and the heat-insulating glass (2).

7. The optical path system for eliminating stray light of a projector according to claim 6, characterized in that: A heat dissipation space with a distance of 10 mm is provided between the LCD (3) and the heat-insulating glass (2).

8. The optical path system for eliminating stray light of a projector according to claim 1, characterized in that: The field lens (4) is a Fresnel lens.

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