KR20130048524A

KR20130048524A - Projector with prism

Info

Publication number: KR20130048524A
Application number: KR1020110113410A
Authority: KR
Inventors: 이동희; 김용관; 박성하; 이중기
Original assignee: 삼성전자주식회사
Priority date: 2011-11-02
Filing date: 2011-11-02
Publication date: 2013-05-10

Abstract

According to an aspect of the present invention, a projector for projecting light, which forms an image on an external screen, to a display panel including a plurality of pixel elements and forming the image by controlling the pixel elements according to a driving signal. and; A first lens group including at least one lens for uniformly irradiating light onto the display panel, the first lens group having positive refractive power; It includes a second lens group having a positive refractive power, and changes the traveling path of the light reflected from the projector panel and transmitted through the first lens group, the second lens group includes a prism of a single material.

Description

Projector with Prism {PROJECTOR WITH PRISM}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projector, and more particularly, to a small projector (Pico / Micro-Projector) that is generated by a light source such as a light emitting diode (LED), a lamp, and then projects light transmitted through a projection optical system onto a screen using a mirror. It is about.

Recently, the development of technology for a small projector that is embedded in a display device such as a mobile phone, a computer, an MP3 player, a small digital camera, and displays stored data or a video as an image to the outside is being rapidly developed. Conventional small projectors have a small flat panel display panel such as a digital micro-mirror device (DMD) or a liquid crystal display (LCD) having a relatively small volume and weight.

Conventional projectors also include illumination optics and projection optics. The illumination optical system refers to the optical system aligned with the optical path from the light source to the display panel, and the projection optical system refers to the optical system aligned with the optical path from the display panel to the external screen.

On the other hand, a typical floor projection type projector has a DMD having a horizontal and vertical ratio of 4: 3 or 16: 9 and a mirror located at the screen side end of the optical path, and is projected on the screen (or the bottom surface). The image has distortion and aberration such as keystone, chromatic aberration, spherical aberration, and astigmatism.

Conventional floor projection type projectors use expensive optical elements such as color suppression elements to correct distortion and aberration while changing the optical path, which increases the overall manufacturing cost of the projector and reduces the assembly yield of the projector. Cause.

It is an object of certain embodiments of the present invention to at least partially solve, alleviate or eliminate at least one of the problems and / or disadvantages associated with the prior art.

One object of the present invention is to provide a projector having a configuration that is low in manufacturing cost, and can increase the assembly yield.

According to an aspect of the present invention, a projector for projecting light, which forms an image on an external screen, to a display panel including a plurality of pixel elements and forming the image by controlling the pixel elements according to a driving signal. and; A first lens group including at least one lens for uniformly irradiating light onto the display panel, the first lens group having positive refractive power; And a second lens group having a positive refractive power and changing a path of propagation of the light reflected from the projector panel and passing through the first lens group, wherein the second lens group includes a prism of a single material. do.

The present invention is advantageous in that manufacturing cost is low and assembly yield can be increased by changing the optical path and correcting distortion and aberration by using at least one lens aligned with a low-cost single material prism. .

1 is a view showing the basic configuration of a small projector according to a preferred embodiment of the present invention,
2 is a diagram showing a ray tracing simulation result;
3 shows the prism in detail;
4 shows a part of the projection optical system in detail;
5 shows an example of an illumination optical system.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, specific matters such as specific elements are shown, which are provided to help a more general understanding of the present invention. It is self-evident to those of ordinary knowledge in Esau. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

Hereinafter, in the embodiments of the present invention, ordinal numbers such as first and second are used, but only for distinguishing objects of the same name from each other, the order of which may be arbitrarily determined, and the preceding description of the objects of subordinate order. Can be applied mutatis mutandis.

1 is a view showing the basic configuration of a small projector according to a preferred embodiment of the present invention, Figure 2 is a view showing the results of the ray tracing simulation. The projector may include an illumination optical system 100 for illuminating a display panel, a display panel 300 for reflecting light from the illumination optical system 100 in units of pixels, and forming an image, and the light reflected from the display panel 300. And a projection optical system 400 for projecting light onto an external screen.

The illumination optical system 100 includes at least one light source and at least one lens for uniformly illuminating the display panel 300 by adjusting light incident from the light source.

The display panel 300 reflects the light incident from the illumination optical system 100 in pixel units to form an image.

The display panel 300 displays an image in pixel units, and the display panel 300 includes pixel elements 320 corresponding to a predetermined resolution, and drives the pixel elements 320 on and off. Display the image through. In this example, as the display panel 300, a small flat panel display panel such as a digital micro-mirror device (DMD) including micromirrors arranged in an MxN (eg, 1280x720, 854x480, etc.) matrix structure is used. . Each of the micromirrors rotates to a position corresponding to an on state and a position corresponding to an off state according to a driving signal, and when the micro mirror is in the on state, the light incident at an angle that can be displayed on a screen (for example, a bottom surface) is displayed. And reflects the incident light at an angle not displayed on the screen when it is in the off state. That is, the light reflected from the off-state micro mirror is not emitted to the outside through the projection optical system 400, and the light reflected from the on-state micro mirror is emitted to the outside through the projection optical system 400. . The display panel 300 may include a circuit board 310 that provides a driving signal to the pixel devices 320, pixel devices 320 mounted on the circuit board 310, and the pixel devices 320. ) Is covered with a cover glass 330 for protecting from the external environment, and a sealing layer 340 for protecting the exposed upper surface of the circuit board 310 from the external environment.

The projection optical system 400 has an optical axis 405, and includes first to third lens groups G1, G2, and G3, and a shear mirror 500. Generally, an optical axis refers to a shaft having no optical fluctuation even if the optical element is rotated around the optical axis. Being aligned on the optical axis means that the center of curvature of the optical element is located on the optical axis, or the symmetry point (i.e., the center of symmetry) or center of the optical element is located on the optical axis. Hereinafter, terms such as a rear end and a front end follow a direction from the display panel 300 to the front end mirror 500. The front end mirror 500 is located at the front end (or front) of the projector.

The term lens group is also used to refer to a set of at least one optical element having the ability to refract light as well as the lens.

In the present invention, the first lens group G1 including the display panel 300, the first lens 410, and the second to sixth lenses 420 to 428 constituting the second lens group G2 are provided. The seventh lens 440 aligned with the optical axis 405 and constituting the second lens group G2, the third lens group G3 including the eighth lens 450, and the shear mirror 500. ) Is stockpiled. In this case, non-axis alignment means that the optical axis 405 or its extension line passes through the optical element, but the central axis of the optical element does not coincide with the optical axis 405. In the case of the prism 430, the optical axis 405 is located at a point corresponding to half of the overall height, and the axis of symmetry of the prism 430 is perpendicular to the optical axis 405.

Table 1 shows numerical data of optical elements constituting the projection optical system 400. Table 1 below shows C, the radius of curvature of the i-th optical surface Si, the thickness or the air gap of the i-th optical surface (or the distance from the i-th optical surface to the (i + 1) optical surface). T, N which is the refractive index in the d line (587.5618 nm) of the i-th optical surface, and V which is the Abbe's number of the i-th optical surface, are shown. In addition, the unit of curvature radius and thickness is mm. The number i of the optical surface is sequentially attached from the display panel 300 side to the front mirror 500 side.

In Table 1, the first, fifth, seventh and eighth lenses 410, 426, 440, and 450 are double-sided aspherical lenses, and when the optical plane is a plane, the radius of curvature is infinite, and the refractive index of air is 1 to be. The radius of curvature for the aspherical surface represents the value measured at the center of the aspheric surface.

The aspherical definition is represented by Equation 1 below.

In Equation 1, z is a distance along the optical axis 405 from the center (or vertex) of the optical surface, h is a distance in a direction perpendicular to the optical axis 405, c is the curvature at the center of the optical surface (Inverse of the radius of curvature), k denotes the conic coefficient, A, B, C, D, E, F and G represent aspherical coefficients, G = 0.

Table 2 below illustrates aspherical surface coefficients for each aspherical surface of Table 1 above.

Hereinafter, the description of the shape of the optical surface is based on the <Table 1>, the optical surface of each optical element constituting the projection optical system 400 may be spherical or aspheric.

The first lens group G1 includes a first lens 410 and has a positive power. The first lens 410 receives light from the illumination optical system 100 and allows the light to enter the display panel 300 at a uniform angle. In this case, the first lens 410 allows the light to be matched to the display panel 300 in consideration of an overfill. That is, the first lens 410 allows the reflected light to enter the area equal to or larger than the area occupied by the pixel elements 320 of the display panel 300. In addition, the first lens 410 receives the light reflected from the display panel 300 and reduces and outputs the beam area of the light. Since the light reflected from the display panel 300 has a large beam spot size, light loss due to light that is not transmitted to the second lens 420 may be large. The first lens 410 focuses the light reflected from the display panel 300 and reduces the beam area so that the maximum amount of light is transmitted to the second lens 420.

The first lens 410 has concave-convex fourth and fifth optical surfaces S4 and S5 based on a direction from the display panel 300 toward the front end mirror 500, and the fourth and fifth lenses. Each of the optical surfaces S4 and S5 is an aspherical surface. Hereinafter, the shape of the aspherical lens is based on the curvature (or radius of curvature) of the center thereof.

The second lens group G2 includes second to seventh lenses 420 to 428 and 440 and a prism 430 and has a positive refractive power. The second lens group G2 changes the optical path using the prism 430 and includes an aperture surface to control the total amount of light. In this case, the change of the optical path means that the main ray traveling along the optical axis (to coincide with the optical axis) proceeds at a predetermined angle (ie, inclination or tilt) with the optical axis. This change in light path (i.e. change in the propagation path of the chief ray) is typically caused by a prism or mirror. For example, since the light incident at 45 degrees to the planar mirror is reflected at 45 degrees, the light path is changed by 90 degrees. Although not shown, an aperture having an opening area that matches the area of the rear optical surface of the fifth lens 426 is positioned between the fourth lens 424 and the fifth lens 426.

The second lens 420 has concave-convex sixth and seventh optical surfaces S6 and S7, and each of the sixth and seventh optical surfaces S6 and S7 is spherical.

The third lens 422 has the two-sided convex eighth and ninth optical surfaces S8 and S9, and each of the eighth and ninth optical surfaces S8 and S9 is a spherical surface. In this case, since the third and fourth lenses 422 and 424 form two bonded lenses, and the bonded optical surfaces of the third and fourth lenses 422 and 424 have the same curvature, Table 1 The data of the rear optical surface of the third lens 422 is omitted.

The fourth lens 424 has ninth and tenth optical surfaces S9 and S10 that are concave on both sides, and each of the ninth and tenth optical surfaces S9 and S10 is a spherical surface.

The fifth lens 426 has the double-sided concave eleventh and twelfth optical surfaces S11 and S12, and each of the eleventh and twelfth optical surfaces S11 and S12 is an aspherical surface.

The sixth lens 428 has concave-convex thirteenth and fourteenth optical surfaces S13 and S14, and each of the thirteenth and fourteenth optical surfaces S13 and S14 is a spherical surface.

3 illustrates the prism 430 in detail.

The prism 430 generally has a trapezoidal shape, and the prism 430 may be formed by joining the second half 432 and the first half 434 symmetrically formed of the same material. Alternatively, the prism 430 may be integrally formed without requiring a subsequent bonding process through an injection process or the like. The rear hypotenuse side 430a and the front side hypotenuse 430b which are not parallel to each other of the prism 430 form the same angle as the optical axis 405. Considering the direction in which the angle is measured from the optical axis (for example, counterclockwise + and clockwise −), the front hypotenuse 430a and the posterior hypotenuse 430b are opposite in sign and have the same angle. I can speak. For example, the rear hypotenuse 430a may have an inclination angle of +78.6 degrees, and the front hypotenuse 430b may have an inclination angle of −78.6 degrees. In Table 1, the trailing hypotenuse 430a and the symmetry plane 430e correspond to the fifteenth and sixteenth optical surfaces S15 and S16, respectively.

In this example, the prism 430 has a shape of an equilateral trapezoid, and at each of the upper sides 430c and the bottom sides 430d of the prism 430, the sizes of the two cabinets at the vertices of both ends are the same (that is, θ2 = θ3, θ4 = θ5). In addition, the sum of the inner angle of the upper side 430c and the inner angle of the lower side 430d forms 180 degrees (that is, θ2 + θ4 = 180 ° and θ3 + θ5 = 180 °). The prism 430 is made of a single material. For example, the angles of the upper side 430c of the prism 430 may be 101.4 degrees, respectively. In this case, the inner angles of the upper side 430c of the prism 430 may range from 98 degrees to 105 degrees, and the refractive index of the prism 430 may range from 1.69 to 1.48. Similarly, angles formed between the rear hypotenuse side 430a, the front side hypotenuse side 430b, and the optical axis 405 of the prism 430 that are not parallel to each other may range from 82 degrees to 75 degrees. For example, when the inner angle of the upper side 430c of the prism 430 is 99 degrees, the refractive index of the prism 430 is 1.69, and the rear hypotenuse 430a and the front end of the prism 430 are not parallel to each other. An angle formed by each of the hypotenuse sides 430b and the optical axis 405 may be 81 degrees.

Unlike the present example, the cabinets of the upper side 430c of the prism 430 may be different from each other, for example, 102.5 degrees and 100.7 degrees.

The prism 430 changes the optical path, and the aberration and distortion caused by the prism 430 may be removed by the seventh and eighth lenses 440 and 450.

4 is a detailed view of a part of the projection optical system.

The seventh lens 440 has planar-convex seventeenth and eighteenth optical surfaces S17 and S18, and each of the seventeenth and eighteenth optical surfaces S17 and S18 is an aspherical surface. The central axis 442 of the seventh lens 440 forms a predetermined angle θ1 with the optical axis 405 in a state spaced apart from the optical axis 405 by a predetermined distance. Unlike the present example, the central axis 442 of the seventh lens 440 may be eccentric with respect to the optical axis 405 but not tilted. The seventh lens 440 refracts the light transmitted through the prism 430 to proceed at a predetermined angle with the optical axis 405. That is, the seventh lens 440 functions to change the optical path, and in other words, the main light beam traveling along the optical axis 405 (to coincide with the optical axis) forms a predetermined angle with the optical axis.

The third lens group G3 includes an eighth lens 450 and has a negative refractive power. The eighth lens 450 has planar-convex nineteenth and twentieth optical surfaces S19 and S20, and each of the nineteenth and twentieth optical surfaces S19 and S20 is an aspherical surface. The eighth lens 450 increases the angle between the chief ray passing through the seventh lens 440 and the optical axis 405. That is, like the seventh lens 440, the eighth lens 450 serves to change the optical path and further increase the inclination angle of the chief rays. In addition, the central axis 452 of the eighth lens 450 is spaced apart from the optical axis 405 by a predetermined distance. The central axis 452 of the eighth lens 450 is eccentric with respect to the optical axis 405 but is not tilted.

The shear mirror 500 has a convex reflective surface, and the reflective surface is spherical. The front end mirror 500 projects the light transmitted through the eighth lens to the screen (or the bottom surface). In Table 1, the reflective surface corresponds to the twenty-first optical surface (S21).

Each lens group of the projection optical system 400 may move to adjust the focus.

For example, the shear mirror 500 is fixed and each lens group is moved simultaneously, or each lens group is fixed and the shear mirror 500 is moved, or the first lens group G1 and the shear mirror 500 are moved. The second lens group G2 and the third lens group G2 and G3 may be simultaneously moved in opposite directions.

5 is a diagram illustrating an example of the illumination optical system 100.

The illumination optical system 100 has a first auxiliary optical axis 105 and a second auxiliary optical axis 107, first and second light sources 110 and 140, first to fourth collimating lenses, 120, 130, 150, 160, a filter 170, an equalization lens 180, a condensing lens 190, and an intermediate mirror 200. The second light source 140 and the third and fourth collimating lenses 150 and 160 are aligned on the second auxiliary optical axis 107, and the remaining optical elements of the illumination optical system 100 are connected to the first auxiliary light. Aligned on the optical axis 105. In the present example, the output light is mixed to use a plurality of light sources that can produce white light, but one light source (for example, a wavelength variable light source) that outputs light of various colors may be used. Alternatively, three light sources according to the three primary colors may be used, or a white light source may be used together with the color filter.

The first light source 110 outputs first primary color light traveling along the first auxiliary optical axis 105. For example, the first light source 110 may be an LED that outputs green light. In this example, the first light source 110 outputs a first primary color light emitted at a predetermined angle about the first auxiliary optical axis 105. Alternatively, a collimation lens may be integrated in the first light source 110, and in this case, the first collimation lens may be removed.

The first and second collimating lenses 120 and 130 receive the divergent first primary color light output from the first light source 110, and collimate (ie, parallelize) the first primary color light. Output In this case, collimation refers to reducing the divergence angle of light, and ideally, makes the light proceed in parallel without converging or diverging. The first primary color light output from the first light source 110 may diverge in one direction, and in this case, at least one surface may be an aspheric lens as the collimating lenses. In this example, progressive collimation of the first primary color light output from the first light source 110 (ie, the first and second collimating lenses 120 and 130 gradually parallelize the first primary light), or Split collimation in two directions perpendicular to each other (ie, the first collimation lens 110 collimates the first primary color light in the first direction (eg, Y-axis direction), and the second collimation lens). First and second collimating lenses 120 and 130, which pair 130 for collimating the first primary color light in a second direction (eg, Z-axis direction) perpendicular to the first direction. ), But one collimation lens may be used. In FIG. 5, the Z axis coincides with the optical axis 405 of the projection optical system 400.

The second light source 140 outputs second and third primary colors of light traveling along the auxiliary optical axis 107. For example, the second light source 140 may use one or two LEDs that output red light and blue light.

The third and fourth collimating lenses 150 and 160 receive divergent second and third primary colors of light output from the second light source 140, and collimate the second and third primary colors of light. Output

Unlike the present example, the second and third primary light sources may be present separately, in which case each collimating lens may be present in front of each primary light source. For example, the second primary color light source is transmitted to the third primary color light source placed on the second auxiliary optical axis 107 and is substantially parallel to the first auxiliary light axis 105 substantially perpendicular to the second auxiliary optical axis 107. Another reflecting filter is located in front of the filter 170 placed on the first auxiliary optical axis 105 (ie, located between the third primary light source and the filter 170 on the second auxiliary optical axis 107). can do.

The filter 170 reflects the second and third primary color light input from the fourth collimation lens 160 to travel along the first auxiliary optical axis 105, and the second collimation lens 130. Transmits the first primary color light inputted from The filter 170 may be disposed to form an angle of 45 degrees with the first auxiliary optical axis 105, and may reflect the second and third primary colors at an angle of 90 degrees. However, it should be noted that the filter 170 is not always disposed at an angle of 45 degrees with the first optical axis 105, which is just one example. Preferably, a wavelength selective filter (or a dichroic filter) or a prism that selectively performs transmission or reflection according to the wavelength as the filter 170, or a beam splitter ) And a wavelength independent filter such as a half mirror. For example, such wavelength selective filter can be implemented by depositing a plurality of thin films on a glass substrate. By the filter 170, the first to third primary colors of light travel along the same first auxiliary optical axis 105.

The equalizing lens 180 equalizes and outputs the light input from the filter 170. That is, the equalization lens 180 uniforms the intensity distribution of the light on the Y-Z plane. As the equalizing lens 180, a conventional fly eye lens may be used. The aspect ratio of the light is matched with that of the display panel 300 by the equalization lens 180, and color uniformity is improved.

The condenser lens 190 makes the light input from the equalizing lens 180 focus on the surface of the display panel 300.

The intermediate mirror 200 receives the focused light from the condenser lens 190 and reflects the light toward the display panel 300. The intermediate mirror 200 may have a structure in which a dielectric layer or a metal layer having high reflectivity is deposited on a substrate. As indicated by a dotted line in FIG. 5, at least one edge of the intermediate mirror 200 may be cut at an angle other than a right angle to be sloped.

It will be apparent to those skilled in the art that the projector according to the present invention is not limited to the bottom projection type projector, and thus can be used with the shear mirror removed, and some components such as the omission of the third lens group can be omitted.

100: illumination optical system, 300: display panel, 400: projection optical system, 500: shear mirror

Claims

A projector for projecting light to form an image on an external screen to the outside,
A display panel having a plurality of pixel elements, the display panel forming an image by controlling the pixel elements in accordance with a driving signal;
A first lens group including at least one lens for uniformly irradiating light onto the display panel, the first lens group having positive refractive power;
A second lens group having a positive refractive power and changing a traveling path of the light reflected from the projector panel and transmitted through the first lens group;
And the second lens group includes a prism of a single material.

The method of claim 1,
And the prism has a shape of an equilateral trapezoid.

The method of claim 1,
The prism has a trapezoidal shape and has a structure in which the first half and the second half symmetrical to each other are bonded to each other.

The method of claim 1,
And the second lens group includes a lens whose central axis is spaced apart from the optical axis of the first lens group and is inclined with the optical axis.

The method of claim 1,
And a third lens group having a negative refractive power and changing a propagation path of light passing through the second lens group.

The method of claim 5,
And the third lens group includes a lens whose central axis is spaced apart from the optical axis of the first lens group.

The method of claim 5,
And a shear mirror that reflects the light transmitted through the third lens group to the screen.

The method of claim 5,
And controlling the focus of the light projected on the screen while simultaneously moving each of the first to third lens groups.

The method of claim 5,
And adjusting the focus of light projected on the screen while simultaneously moving the second and third lens groups in opposite directions.

The method of claim 7, wherein
And fixing the focus of the light projected on the screen while moving the shear mirror while the first to third lens groups are fixed.

The method of claim 1,
And an angle formed between the optical surfaces of the prism and the optical axis of the first lens group is in a range of 98 degrees to 105 degrees.

The method of claim 11,
And the refractive index of the prism is in the range of 1.48 to 1.69.