RU2462741C2 - Optical projector system - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: optical system has an optical modulator, an optical inversion system which forms an intermediate image plane which is projected by the frontal optical system onto a mirror which reflects the image onto a screen. The optical modulator has red, green and blue colour components which can be shifted. The optical inversion system has more than two groups of lenses which can move along the optical axis in order to change the size of the image. The shape and arrangement of lenses of the frontal optical system are such that chromatic aberrations resulting therefrom are partially compensated for by shifting intermediate images along the optical axis, formed by each of the colour components of the optical modulator, and the shifting of intermediate images is compensated for by shifting optical modulators of the colour components. The distances between the intermediate image plane and the reflecting mirror, between the optical axis and the edge of the intermediate image plane, between the plane of the optical modulator and the reflecting mirror and between the optical axis and the edge of the plane of the optical modulator satisfy conditions given in the claim.

EFFECT: higher luminosity, angle of view, magnification range, image quality and shorter projection distance with compact sizes.

9 cl, 12 dwg, 5 tbl

Description

The present invention relates to optics, namely to projection optical systems with a wide focusing range and a variable image size, and can be used as an optical system in projection devices for forming large-sized images on a screen surface for business, home cinema, advertising, especially projection systems with short distances.

Currently, as optical modulators for projection devices, digital micro-mirror devices (DMDs) and liquid crystal displays (LCDs) are widely used.

Various projection devices with a zoom function that allows you to resize the image on the screen are well known. There are two types of commonly used projection devices. The first type is a lens with a variable focal length, in which resizing the image on the screen is achieved by moving the components at a fixed projection distance. The second type is a projection device in which resizing an image requires changing the projection distance.

A projection optical system is known in the art (see US Patent Application Laid-Open No. 20080192336 [1] of a combined type (a combination of reflective and refractive elements) containing a group of refractive lenses with axisymmetric surfaces and a decentralized mirror with a polynomial surface (the so-called "free-form" "). This system projects the light from the optical modulator onto the screen with different magnifications, which is achieved by changing the projection distance.

The disadvantage of the technical solution described above is: the large size of the optical elements, the insufficient range of the focal length, low aperture ratio, poor image quality, non-telecentric path of the rays and the complex profile of the mirror surface due to the large aspherical gradient.

U.S. Patent Laid-Open No. 20080100927 [2] describes a projection-type display device comprising a front lens group having several lenses, each of which has an axisymmetric surface shape, and a rear lens group located after the front lens group, containing refractive lenses with an axisymmetric surface shape , several lenses with a polynomial surface shape ("free-form") and a convex reflective mirror located after the rear group of lenses and having a polynomial shape of the reflecting surface.

The disadvantages of this technical solution are the large size of the lens, the insufficient range of the focal length, low aperture ratio and low image quality due to the large number of complex optical elements that make up the optical system.

The closest to the claimed invention is a projection optical system described in US Patent Application Laid-Open No.2010997582 [3], which has a relatively short overall length and can project a high-quality, large image. The projection optical system comprises a lens system and at least one curved mirror. The OAL distance and the Y distance satisfy the requirement 20 <OAL / Y <30, where OAL is the distance between the surface of the optical modulator and the surface of the curved mirror, and the distance Y is the distance between the common optical axis of the lens and the edge of the lens with the largest diameter. This projection optical system is selected as a prototype of the claimed invention.

The main disadvantages of the prototype should be noted the large size of the lens, the insufficient range of the focal length, low aperture ratio and poor image quality due to the large number of optical elements of complex shape that make up the optical system.

The objective of the invention is the creation of a projection optical system capable of, with compact dimensions, projecting light from an optical modulator onto a screen with different magnifications, and such a system should have a higher aperture ratio, a wider field of view, a smaller projection distance, a larger range of magnifications and more high quality projected image.

The technical result is achieved by developing an improved design of a projection optical system comprising an optical modulator arranged in series with the light propagating around the optical system, the plane of the intermediate image, the front optical system and a reflecting mirror, the optical modulator containing red, green and blue color components made with the possibility of bias, the wrapping optical system contains several (more than two) groups of lenses, made with the possibility of their movement along the optical axis in order to change the increase in image size, while the inverting optical system is configured to form an intermediate image between the inverting optical system and the frontal optical system, which is configured to project the intermediate image on a reflective mirror, which is configured to image reflection on the screen, while all the optical elements of the projection optical system have a common optical axis, and the shape and arrangement of the lenses of the frontal optical system are selected so that the chromatic aberrations caused by them are partially compensated by the offset along the optical axis of the intermediate images formed by each of the color components of the optical modulator, and the offset of the intermediate images is compensated by the shift of the optical modulators of the color components, the optical elements of the projection optical system satisfy the conditions (1) and (2):

where OAL 'is the distance between the plane of the intermediate image and the reflecting mirror, Y' is the distance between the optical axis and the edge of the intermediate image plane;

where OAL is the distance between the plane of the optical modulator and the reflecting mirror, Y is the distance between the optical axis and the edge of the plane of the optical modulator.

The inventive optical system allows you to create compact, simple in design projectors with smaller, in comparison with the prototype, overall dimensions, which is achieved due to the high difference in the focal length provided by moving groups of lenses. Moreover, the design is characterized by the presence of a smaller, in comparison with the prototype, number of lenses, a minimum of aspherical surfaces, the absence of surfaces of complex shape (polynomial surfaces), which is ensured by the introduction of a wrapping optical system and a frontal optical system, while the wrapping optical system is configured to form an intermediate image, located between the reversing and frontal optical systems with a large difference in magnification, and the frontal optical system ma includes at least one mirror with curved surface directed toward the screen.

For a better understanding of the claimed invention the following is a detailed description with the corresponding drawings.

Figure 1. A diagram of a projection system according to the invention.

Figure 2. Scheme of a wrapping optical system according to the invention.

Figure 3. Scheme of the front optical system according to the invention.

Figure 4. Graph of the modulation transfer function (MTF) of the front optical system according to the invention.

Figure 5. Graphs of aberrations of the front optical system according to the invention.

6. MTF graph of a wrapping optical system according to the invention.

7. Graphs of aberrations of a wrapping optical system according to the invention.

Fig. 8. Scheme explaining the principle of compensation for chromatic aberrations according to the invention.

Items:

I is an optical modulator;

P - X-cube prism;

S - aperture diaphragm;

R is a wrapping optical system;

IP is the plane of the intermediate image;

F - frontal optical system;

M is a mirror;

R, G, B are the red, green, and blue color components of the optical modulator I, respectively.

Table 1. The design data of the front optical system according to the invention.

Table 2. Aspheric coefficients of a frontal optical system according to the invention.

Table 3. The design data of the wrapping optical system according to the invention.

Table 4. Aspheric coefficients in a wrapping system according to the invention.

Table 5. Variable data in a wrapping system according to the invention.

The claimed projection optical system operates as follows (Figure 1). The light from a light source, which can be a lamp or a system based on at least one light emitting diode or a laser source (for example, based on semiconductor laser diodes), after being divided into three color channels, illuminates the corresponding micromirror or liquid crystal panels of optical modulators I where modulation of the R, G, B bands occurs, respectively. Further, the light from the three panels of optical modulators I is collected using the X-prism P (see, for example, http://www.nitto-optical.co.jp/nitto-optical.com/products/basic_prism/) [4] and it enters the wrapping optical system Z, which forms an intermediate image on the IP plane of the intermediate image, then the light passes through the front optical system F, is reflected from the mirror M and forms an enlarged image on the screen.

The distance OAL 'and the distance Y' satisfy the relation 10 <OAL '/ Y' <20, where OAL 'is the distance between the IP plane of the intermediate image and the reflecting mirror M, and the distance Y' is the distance between the optical axis and the edge of the IP plane of the intermediate Images. In this case, the chromatic aberrations of the front optical system are partially compensated by the shift along the optical axis of the intermediate images “IP” for each of the R, G, B color components, which for the reversing optical system “Z” is chromatic aberration (position chromatism), which, in turn, , partially offset by the displacement along the optical axis of each of the modulators "I" - R, G, B color components. On Fig presents a diagram explaining the above principle of compensation for chromatic aberrations.

The OAL distance and the Y distance satisfy the relation 30 <OAL / Y <60, where OAL is the distance between the plane of the optical modulator I and the reflecting mirror M, and the distance Y is the distance between the optical axis and the edge of the surface of the optical modulator I.

The telecentricity condition for the projection system imposes restrictions on the rays that enter the optical system, namely, the angles of the main rays relative to the plane perpendicular to the optical axis must satisfy the relation 0 <α <2 °, where α is the angle of incidence of the main beam on the plane which is perpendicular optical axis of the projection system.

The reversing optical system R contains more than two groups of lenses, some of which have the ability to move to focus. Most optical elements are made of optical glass with a conventional (spherical) surface shape.

At least one surface in the wrapping optical system Z and the surface of the reflecting mirror M are aspherical and are described by the expression:

where r is the radius of the surface, c is the curvature of the surface, k is the conical constant, α4 ..., α ₁₀ are higher-order aspherical coefficients.

In addition, the wrapping optical system forms the planes of the intermediate IP image located between the wrapping optical system R and the front optical system F. The following conditions (1) - (4) are fulfilled:

- The ratio of the OAL 'and Y' distances satisfies the condition:

where OAL 'is the distance between the IP plane of the intermediate image and the reflecting mirror M;

Y 'is the distance between the optical axis and the edge of the IP plane of the intermediate image.

- The ratio of the OAL and Y distances satisfies the condition:

where OAL is the distance between the plane of the optical modulator I and the reflecting mirror M;

Y is the distance between the optical axis and the edge of the surface of the optical modulator "I".

The telecentricity condition for the projection system satisfies the relation:

where α is the angle of incidence of the main beam on a plane that is perpendicular to the optical axis of the projection system.

The shape of the aspherical surface is described by the ratio:

where r is the radius of the surface, c is the curvature of the surface, k is the conical constant, α4 ..., α ₁₀ are higher-order aspherical coefficients.

In addition, the aspherical surfaces of the correction lenses are able to reduce the total number of lenses of the reversing optical system Z and the front optical system F and to reduce the overall dimensions of the projection system.

Figure 2 shows the optical diagram of an embodiment of a reversing optical system, which contains a successive X-cube prism P, the first positive meniscus 1 facing the concave surface to the plane of objects, the second positive meniscus 2 facing the concave surface to the plane of objects, positive lens 3, negative lens 4, separated by an air gap with the third positive meniscus 5, convex surface facing the plane of objects, biconcave negative th lens 6, a negative meniscus 7 separated by an air gap to a fourth positive meniscus 8 facing the convex surface to the intermediate image plane, a positive bi-convex lens 9 and the fifth positive meniscus 10, a convex surface facing to the object plane.

Lenses 3, 4, 5, 6, 7, 8, and 9 comprise four movable lens groups, respectively.

Figure 3 shows the optical diagram of the frontal optical system, which contains a negative meniscus 11 sequentially located along the rays, separated by an air gap with the first biconvex positive lens 12, a biconcave lens 13, separated by an air gap with the second biconvex positive lens 14, a plano-convex positive lens 15 , the first biconcave negative lens 16, the third and fourth biconvex lenses 17 and 18, and the second biconcave negative lens.

In a preferred embodiment, the inventive projection optical system operates under the following conditions: the projection distance (from the mirror to the screen) is fixed, the image size varies from 60 inches to 120 inches due to the movement of four groups of lenses in a wrapping optical system.

The design data of the front optical system F are shown in tables 1, 2.

The design data of the wrapping optical system are shown in tables 3, 4, 5.

F #: 3.75

OAL ': 255 mm Y' = 23.5 mm

OAL: 528 mm Y = 9.4 mm

For waves: 640, 520, 455 nm

Table 1 No. Surface type Radius Thickness n _d ν _d Diameter AN OBJECT PLANE Infinity 2124.3 one PLANE Infinity -530 162.9 2 * ASPHERICA -73.39 160 MIRROR 33.2 3 SPHERE 104.4 8 1.709 29.6 28.4 four SPHERE -25.22 1.60 28.4 5 SPHERE -38.33 6.15 1.753 29.9 28.2 6 SPHERE 65.4 14.49 17.3 7 SPHERE -26.41 3.86 1.601 61.3 16.8 8 SPHERE 45.13 2.62 15.6 APERT. PLANE Infinity 6.92 10.8 10* ASPHERICA 21.86 2 1.682 31.2 14.4 eleven SPHERE -36.96 1.39 17.4 12 SPHERE -1413.7 4.13 1.717 47.1 18.4 13 SPHERE 25.42 0.1 20.4 fourteen SPHERE -40.52 8.65 1.620 60.3 25.0 fifteen SPHERE 20.39 0.37 25.6 16 SPHERE 20.31 5.6 1.640 34.4 25.4 17 SPHERE -38.51 8.78 29.6 eighteen SPHERE -157.4 13.22 1.755 27.5 40.6 19 SPHERE 28.88 0.1 42.3 twenty SPHERE 28.84 2 1.598 61.5 42.3 21 SPHERE 38.65 5.1 45.6 IMAGE. PLANE Infinity 46.0

table 2 No. K A ₄ A ₆ A ₈ ν _d 2 * -0.669753 1.8836433e-007 -1.4666261e-011 1.3811477e-015 -6.267741569e-020 10* 0.3093505 3.3093631e-006 1.2417344e-007 -2.1120007e-009 2.3423584257e-011

Table 3

Numerical Aperture: 0.33

Wavelength: 640, 520, 455 nm

No. Surface type Radius Thickness n _d ν _d Diameter AN OBJECT PLANE infinity 18.8 one PLANE infinity 3.0 E-c3 18.8 2 PLANE infinity 1.0 20.2 3 PLANE infinity 30.0 Bsc7 21.0 four PLANE infinity 5.16 35.5 5 SPHERE -30.73 12 1.744 44.8 35.2 6 SPHERE -30.26 0.5 43.7 7 SPHERE 1769.5 5.47 1.620 60.3 47.5 8 SPHERE -79.47 change. 47.9 9 SPHERE 41.54 7.7 1.620 60.3 47.6 10 SPHERE 261.5 change. 46.9 eleven SPHERE 38.63 3 1.755 27.5 31.8 12 SPHERE 19.69 0.5 27.5 13 SPHERE 20.34 10 1.620 60.3 27.5 fourteen SPHERE -475.4 change. 24.3 APER. PLANE infinity change. 20.5 16 SPHERE -58.33 2 1.755 27.5 20.9 17 * ASPHERICA 33.67 change. 22.0 eighteen SPHERE -16.388 2 1.699 30.2 23.4 19 SPHERE -172.6 0.68 30.9 twenty SPHERE -93.37 10.0 1.744 44.8 31.2 21 SPHERE -25.59 0.5 36.3 22 SPHERE 180.5 eleven 1.700 48.7 47.7 23 SPHERE -57.42 change. 49.6 24 SPHERE 68.56 8 1.755 27.6 64.6 25 SPHERE 142.8 60 63.4 IMAGE. PLANE infinity 47.8

Table 4 No. K A ₄ A ₆ A ₈ 17 * 0.23442 -1.2138949e-006 -2.5353082e-008 8.6938718e-011

Table 5 PARAMETER -2.5x -1.67x -1.25x d ₈ 0.5 30.38 61.03 d ₁₀ 17.36 18.35 13.57 d ₁₄ 2.66 0.53 0.12 d ₁₅ 5.61 5.33 7.55 d ₁₇ 6.14 12.51 17.68 d ₂₃ 68.19 33.37 0.5

Ultra-short projection distance is a distinctive feature of the claimed optical system, which makes it possible to arrange the device directly near the screen. The super-wide field of view of such an optical system allows it to be classified as a wall-mounted ("WMD" -Wall Mounted Device) projector and provides wide functionality for the consumer. In particular, it can be used as an optical system in projection devices to form large-sized images on the screen surface for business, home cinema and advertising.

Although the above embodiment of the invention has been set forth to illustrate the present invention, it is clear to those skilled in the art that various modifications, additions and substitutions are possible without departing from the scope and meaning of the present invention disclosed in the attached claims.

Claims (9)

1. A projection optical system comprising:
optical modulator
optical wrapping system
intermediate image plane
frontal optical system and
reflective mirror
moreover, the optical modulator contains red, green and blue color components made with the possibility of displacement, the wrapping optical system contains more than two groups of lenses made with the ability to change the size of the projected image by moving along the optical axis, while the wrapping optical system is configured to form an intermediate images between the wrapping optical system and the frontal optical system, which is configured to project of the weft image onto a reflecting mirror, which is capable of reflecting the image on the screen, while all the optical elements of the projection optical system have a common optical axis, and the shape and arrangement of the lenses of the frontal optical system are selected so that the chromatic aberrations caused by them are partially compensated by the offset along the optical the axis of the intermediate images formed by each of the color components of the optical modulator, and the offset of the intermediate images is compensated Rowan offset optical modulators color component, wherein the optical elements of the projection optical systems satisfy the conditions (1) and (2):

where OAL 'is the distance between the plane of the intermediate image and the reflecting mirror;
Y 'is the distance between the optical axis and the edge of the intermediate image plane;

where OAL is the distance between the plane of the optical modulator and the reflecting mirror;
Y is the distance between the optical axis and the edge of the plane of the optical modulator. 2. The projection optical system according to claim 1, characterized in that the telecentricity condition for it satisfies the ratio:
0 <α <2 °,
where α is the angle of incidence of the main beam on a plane that is perpendicular to the optical axis of the projection optical system. 3. The projection optical system according to claim 1, characterized in that when moving the lens groups, the projection distance is kept constant. 4. The projection optical system according to claim 1, characterized in that the frontal optical system contains at least one reflective mirror having an aspherical surface with a common axis of symmetry. 5. The projection optical system according to claim 4, characterized in that the shape of the aspherical reflective and refractive optical surfaces of the reflective mirror is described by the ratio:

where r is the surface radius;
c is the curvature of the surface;
k is the conical constant;
α ₄ , ..., α ₁₀ are aspherical coefficients of higher order. 6. The projection optical system according to claim 1, characterized in that the spatial optical light modulator is made on the basis of DMD or LCD technology. 7. The projection optical system according to claim 1, characterized in that the lens group of the wrapping optical system has a common axis of symmetry with the lens group of the front optical system. 8. The projection optical system according to claim 1, characterized in that the reversing optical system comprises an X-cube prism arranged in series with the light, the first positive meniscus facing the concave surface to the plane of objects, the second positive meniscus facing the concave surface to the plane of objects , a positive lens, a negative lens, divided by a small air gap with a third positive meniscus, convex surface facing the plane of objects, double utuyu negative lens, a negative meniscus separated by an air gap to a fourth positive meniscus convex surface facing to the intermediate image plane, a positive biconvex lens and a fifth positive meniscus facing a convex surface toward the object plane. 9. The projection optical system according to claim 1, characterized in that the frontal optical system comprises a negative meniscus arranged sequentially in the direction of light propagation separated by an air gap with a first biconvex positive lens, a biconcave lens divided by an air gap with a second biconvex positive lens, and a convex positive a lens, a first biconcave negative lens, a third and fourth biconvex lens, and a second biconcave negative lens.

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