Patent Description:
The present invention generally relates to an optical element and optical apparatus, in particular, to a lighting system and projection apparatus.

Projection apparatus is a display device configured to generate a large-sized picture, and has been continuously progressing with the evolution and innovation of technologies. The imaging principle of the projection apparatus is to convert an illuminating light beam generated by a lighting system into an image light beam via a light valve, and then project the image light beam through a projection lens to a projection target (such as a screen or a wall surface) to form a projection picture.

In addition, the lighting system has evolved to the current most advanced Laser Diode (LD) light source all the way from an ultra-high-performance (UHP) lamp and a light-emitting diode (LED) with the market requirements for the brightness, the color saturation, the service life, the nontoxicity, the environmental friendliness and the like of the projection apparatus. However, in the lighting system, the current economical method for producing red and green lights is to use a blue laser diode to emit an excitation light beam to a phosphor wheel, use the excitation light beam to excite fluorescent powder of the phosphor wheel to generate a yellow-green light, and use a filter element to filter the light to obtain a desired red or green light.

However, in the known lighting system structure, the polarization polarity of the excitation light beam is destroyed by an optical element inside the projection apparatus after the excitation light beam enters the projection apparatus, so that the polarization direction and intensity of the excitation light beam become disordered, thereby causing a problem of non-uniform brightness of a display picture. Therefore, if the projection apparatus generates a three-dimensional (3D) image display picture in a polarized 3D mode (a polarizer arranged on the outer side of a projection lens), an image projected from the projection lens and the polarizer is non-uniform in color or non-uniform in brightness.

The information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Further, the information disclosed in the Background section does not mean that one or more problems to be resolved by one or more embodiments of the invention was acknowledged by a person of ordinary skill in the art.

<CIT> presents an image projector that includes a spatial light modulator (SLM) with a two dimensional array of pixel elements controllable to modulate a property of light transmitted or reflected by the pixel elements. An illumination arrangement delivers illumination to the SLM. A collimating arrangement collimates illumination from the SLM to generate a collimated image directed to an exit stop. The illumination arrangement is configured to sequentially illuminate regions of the SLM, each corresponding to a multiple pixel elements. A controller synchronously controls the pixel elements and the illumination arrangement so as to project a collimated image with pixel intensities corresponding to a digital image.

<CIT> presents a depolarization device. The device has a prism assembly comprising four prisms that are arranged along a main optical axis. Each prism is formed by elementary prismatic blades, where optical axes of the blades are arranged orthogonal to each other. The light beam is passed through beam directions. Linear polarization bodies are arranged orthogonal to each other. Each prism forms an apex angle and a predetermined rotation angle with respect to an optical axis, where the apex angle of the prisms is selected to optimize performance of the device. The prisms are designed as Wollastone prism. The prismatic blades are made of contiguous birefringent material.

<CIT> provides a depolarization element capable of converting incident polarized light into non-polarized light without depending on the polarization direction of the incident polarized light. The depolarization element converts incident light having polarization degree into substantially non-polarized light. The depolarization element has two deflection prisms formed by birefringent crystalline material and arranged along an optical axis. The two deflection prisms have crystal optical axes set in different directions from each other viewed from the optical axis direction. The two deflection prisms have apex angle directions in different directions but not in the inverse directions viewed from the optical axis direction.

<CIT> presents a depolarizing system for polarized light formed of a birefringence crystal wedge which receives the beam of polarized light at a first surface and outputs spatially depolarized light from its output surface. The wedge includes small steps on one of the surfaces or special orientations to depolarize the light. The wedge is substantially triangular in shape so that the surface decreases from one side to the other.

The present invention provides a lighting system and projection apparatus, which make the color or brightness of a display picture uniform under a polarized three-dimensional (3D) mode to allow a user to observe a 3D display picture with relatively high uniformity.

Other objectives and advantages of the present invention are further understood in the technical features disclosed by the present invention.

In order to achieve one or part or all of the above objectives or other objectives, an embodiment of the present invention provides a projection apparatus, comprising a lighting system, at least one light valve and a projection lens. The lighting system is configured to provide an illuminating light beam, and comprises at least one light source, a depolarization element and a light homogenization element. The at least one light source is configured to provide at least one light beam. The depolarization element is disposed on a transmission path of the at least one light beam. The depolarization element comprises a first optical element, and the first optical element is provided with a first optical axis. The light homogenization element is configured to allow the at least one light beam to pass, so as to form the illuminating light beam. The at least one light valve is disposed on a transmission path of the illuminating light beam, and is configured to convert the illuminating light beam into an image light beam. The projection lens is disposed on a transmission path of the image light beam, and is configured to form the image light beam into a projection light beam.

The incidence direction where the at least one light beam is transmitted to the first optical element is not parallel to the first optical axis, and the depolarization element may be located between the at least one light source and the light homogenization element.

In one or more embodiments the depolarization element may comprise a light entering surface and a light exiting surface.

Preferably, the light entering surface may be parallel to the light exiting surface.

In one or more embodiments the first optical element comprises a first light entering surface and a first light exiting surface which are not parallel to each other, and the first light entering surface may be perpendicular to the incident direction.

In one or more embodiments the first optical element may comprise a first light entering surface and a first light exiting surface which are not parallel to each other, and the first light entering surface may be not perpendicular to the incident direction.

In one or more embodiments the depolarization element may also comprise a second optical element comprising a second optical axis, and the first optical axis may be not parallel to the second optical axis.

In one or more embodiments an included angle between the first optical axis and the second optical axis may be between <NUM> degrees and <NUM> degrees.

In one or more embodiments the first optical element comprises a first light entering surface and a first light exiting surface which are not parallel to each other, and the second optical element may comprise a second light entering surface and a second light exiting surface which are not parallel to each other; the first light exiting surface may be parallel to the second light entering surface; and the first light entering surface may be parallel to the second light exiting surface.

In one or more embodiments the shape of the first optical element and the shape of the second optical element may be in geometrical symmetry.

In one or more embodiments the surface shape of the first light exiting surface may be a geometrical shape with a symmetry axis.

In one or more embodiments the material of the second optical element may be different from the material of the first optical element.

In one or more embodiments a gap may be reserved between the first optical element and the second optical element.

In one or more embodiments the first light exiting surface and the second light entering surface may be respectively inclined to the first light entering surface by more than <NUM> degree.

In one or more embodiments the depolarization element may also comprise a connection piece, connected between the first optical element and the second optical element.

In one or more embodiments the first light exiting surface may be inclined to the first light entering surface by more than <NUM> degree.

In one or more embodiments the lighting system may also comprise a focusing element, disposed on the transmission path of the at least one light beam and located between the at least one light source and the depolarization element.

Based on the above, the embodiments of the present invention at least have one of the following advantages or effects. In the lighting system and projection apparatus of the present invention, the depolarization element comprises the first optical element provided with the first optical axis not parallel to the incident direction of light beam transmission, and the depolarization element is located between the light source and the light homogenization element. Therefore, the light beam penetrates through the depolarization element such that the light beam has different polarization states at different positions. In this way, the uniformity of the polarization states of the light beam is improved. Furthermore, if the present invention applied in the polarized 3D mode, an image with uniform color and brightness is generated on a screen, and then a user observes a 3D display picture with relatively high uniformity with polarized 3D glasses.

Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention.

In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as "top," "bottom," "front," "back," etc., is used with reference to the orientation of the Figure(s) being described. The components of the present invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. Unless limited otherwise, the terms "connected," "coupled," and "mounted" and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Similarly, the terms "facing," "faces" and variations thereof herein are used broadly and encompass direct and indirect facing, and "adjacent to" and variations thereof herein are used broadly and encompass directly and indirectly "adjacent to". Therefore, the description of "A" component facing "B" component herein may contain the situations that "A" component directly faces "B" component or one or more additional components are between "A" component and "B" component. Also, the description of "A" component "adjacent to" "B" component herein may contain the situations that "A" component is directly "adjacent to" "B" component or one or more additional components are between "A" component and "B" component. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.

<FIG> is a schematic diagram of projection apparatus <NUM> according to one embodiment of the present invention. Referring to <FIG>, in the present embodiment, the projection apparatus <NUM> is configured to provide a projection light beam LP. Specifically, the projection apparatus <NUM> includes a lighting system <NUM>, at least one light valve <NUM> and a projection lens <NUM>, and the lighting system <NUM> is configured to provide an illuminating light beam LB. The light valve <NUM> is disposed on a transmission path of the illuminating light beam LB, and is configured to convert the illuminating light beam LB into at least one image light beam LI. The so-called illuminating light beam LB is a light beam provided by the lighting system <NUM> to the at least one light valve <NUM>. The projection lens <NUM> is disposed on a transmission path of the image light beam LI, and is configured to form the image light beam LI into a projection light beam LP. The projection light beam LP is projected to a projection target (not shown), such as a screen or a wall surface.

In a technology applied to three-dimensional (3D) displaying, the projection apparatus <NUM> of the present embodiment is used as a polarized 3D image projector. Specifically, when two pieces of projection apparatus <NUM> are in the polarized 3D mode (that is, a polarizer is disposed outside the projection lens <NUM> or polarizers are disposed inside the two pieces of projection apparatus <NUM>), projection light beams LP provided by the two pieces of projection apparatus <NUM> respectively pass through the polarizers to generate images in different polarization states, thereby allowing a user to observe a 3D display picture through polarized 3D glasses. For example, the 3D glasses worn by the user are respectively provided with two polarization elements for left and right glasses lenses, and the two polarization elements correspond to the images, generated by the polarizers of the two pieces of projection apparatus <NUM>, in the polarization states, so as to allow the left and right eyes of the user to respectively receive the images projected by the projector, thereby achieving a 3D display effect.

Specifically, in the present embodiment, the light valve <NUM> is, for example, a reflective light modulator such as a Liquid Crystal on Silicon (LCoS) panel or a Digital Micro-mirror Device (DMD). In some embodiments, the light valve <NUM> is also a penetrating light modulator such as a transparent liquid crystal panel, an electro-optical modulator, a maganeto-optic modulator and an Acousto-Optic Modulator (AOM). The present invention does not limit the number, shape and type of the light valve <NUM>. Detailed steps and implementations of a method for converting the illuminating light beam LB into the image light beam LI by the light valve <NUM> are adequately taught, suggested and implemented by the general knowledge in the art, and descriptions thereof are omitted thereof. In the present embodiment, there is one light value <NUM>. For example, <NUM>-DMD projection apparatus <NUM> is used, but in other embodiments, there is a plurality of light valves, and the present invention is not limited thereto.

The projection lens <NUM> includes, for example, a combination of one or more optical lenses with a diopter, such as various combinations of non-planar lenses including a biconcave lens, a biconvex lens, a concavo-convex lens, a convex-concave lens, a plano-convex lens and a plano-concave lens. In one embodiment, the projection lens <NUM> also includes a planar optical lens that forms the image light beam LI from the light valve <NUM> into the projection light beam LP in a reflecting or penetrating manner and then projects the projection light beam LP to the projection target. The present invention does not limit the shape and type of the projection lens <NUM>.

Moreover, in some embodiments, the projection apparatus <NUM> also optionally includes an optical element with a condensation, refraction or reflection function and is configured to guide the illuminating light beam LB emitted by the lighting system <NUM> to the light valve <NUM> and guide the image light beam LI emitted by the light valve <NUM> to the projection lens <NUM> to generate the projection light beam LP, but the present invention is not limited thereto.

The lighting system <NUM> includes at least one light source <NUM>, a depolarization element <NUM> and a light homogenization element <NUM>. Specifically, the lighting system <NUM> further includes a wavelength conversion element <NUM>, at least one light splitting element <NUM>, at least one reflecting element <NUM> and a filter device <NUM>. In different embodiments, the varieties and quantities of the wavelength conversion element <NUM>, the at least one light splitting element <NUM>, the at least one reflecting element <NUM> and the filter device <NUM> may vary according to different types of lighting systems <NUM>, and the present invention is not limited thereto.

The light source <NUM> is configured to provide at least one light beam L. Specifically, the light source <NUM> includes an excitation light source <NUM> and an auxiliary light source <NUM>. The excitation light source <NUM> provides an excitation light beam L1, and the auxiliary light source <NUM> provides an auxiliary light beam L2. In the present embodiment, the excitation light source <NUM> is a Laser Diode (LD) capable of emitting a blue excitation light beam, and the auxiliary light source <NUM> is a LD capable of emitting a red excitation light beam or a Light Emitting Diode (LED) capable of emitting a red light beam. In other words, in the present embodiment, the light sources <NUM> are all laser light emitting devices.

The wavelength conversion element <NUM> is disposed on a transmission path of the excitation light beam L1 and located between the excitation light source <NUM> and the light homogenization element <NUM>. In the present embodiment, the wavelength conversion element <NUM> is provided with a first region and a second region. The first region has a wavelength conversion material to convert the excitation light beam L1 into an excited light beam L3, and the second region of the wavelength conversion element <NUM> is, for example, a light transmittance plate or an opening configured to allow the excitation light beam L1 to penetrate. In the present embodiment, the wavelength conversion material of the first region is used for converting the blue excitation light beam into a green light beam or a yellow light beam or a yellow-green light beam. In different embodiments, the configuration of the wavelength conversion material of the wavelength conversion element <NUM> varies according to different types of lighting systems <NUM>. The present invention does not limit the configuration and variety of the wavelength conversion element <NUM>.

At least one light splitting element <NUM> is disposed on the transmission path of the excitation light beam L1 or the auxiliary light beam L2, and at least one reflecting element <NUM> is configured to reflect or conduct the excitation light beam LI. For example, in the present embodiment, the at least one light splitting element <NUM> includes a first light splitting element and a second light splitting element. The first light splitting element is located between the excitation light source <NUM> and the wavelength conversion element <NUM> in the transmission path of the excitation light beam LI. The first light splitting element is, for example, a Dichroic Mirror with Green and Orange reflection (DMGO) for allowing the blue excitation light beam L1 and the auxiliary light beam L2 to penetrate and allowing the excited light beam L3 to be reflected. The second light splitting element is located between the auxiliary light source <NUM> and the first light splitting element in the transmission path of the auxiliary light beam L2, and the second light splitting element is, for example, a Dichroic Mirror with Blue reflection (DMB) for allowing the blue excitation light beam L1 to be reflected and allowing the auxiliary light beam L2 to penetrate. Therefore, all the light beams are collected and transmitted to the depolarization element <NUM> via the filter device <NUM>.

The filter device <NUM> is disposed between the light splitting element <NUM> and the depolarization element <NUM>, and is provided with a plurality of different filters for filtering undesired wavelength ranges in the excitation light beam LI, the auxiliary light beam L2 and the excited light beam L3 and a light beam passing through a blue light wave range, a light beam passing through a red light wave range and a light beam passing through a green light wave range. Specifically, in the present embodiment, the filter device <NUM> is a rotatable color wheel device configured to generate a filter effect on the excitation light beam LI, the auxiliary light beam L2 or the excited light beam L3 according to the time sequence, so as to increase the color purity of a light beam passing through the filter device <NUM>. In different embodiments, the configuration of filters of different colors in the filter device <NUM> varies according to different types of lighting systems <NUM>. The present invention does not limit the configuration and variety of the filter device <NUM>.

The light homogenization element <NUM> is configured to allow at least one light beam from the depolarization element <NUM> to pass, so as to form an illuminating light beam LB. Specifically, the light homogenization element <NUM> is configured to adjust the spot shape of the light beam, so that the spot shape of the illuminating light beam LB emitted from the light homogenization element <NUM> is matched with the shape (such as a rectangular shape) of a working region of the light valve <NUM>, and each portion of a light spot has consistent or similar light intensity. In the present embodiment, the light homogenization element <NUM> is, for example, a light integrated rod, but in other embodiments, the light homogenization element <NUM> is also other optical elements of other shapes, such as a lens array. The present invention is not limited thereto.

<FIG> is a schematic diagram of a partial lighting system according to one embodiment of the present invention, and <FIG> is a schematic diagram of a depolarization element of <FIG>. For convenience of description, the light source <NUM> shown in <FIG> and <FIG> and the light beam L provided are only schematically shown, but the partial lighting system <NUM> shown in <FIG> is applied at least to the projection apparatus <NUM> shown in <FIG>, and the present invention is not limited thereto. Therefore, the lighting system <NUM> applied to the projection apparatus <NUM> will be described below. The depolarization element <NUM> is disposed on the transmission path of the light beam L, and is located between the light source <NUM> and the light homogenization element <NUM>. In this way, the light beam L is caused to enter the depolarization element <NUM> before entering the light homogenization element <NUM>, so that the uniformity of the polarization states of the light beam L is improved at first, and then the uniformity of the light beam L is improved, so as to present an image with relatively good color and uniform brightness. In the present embodiment, the depolarization element <NUM> is provided with a light entering surface S1 and a light exiting surface S2. The light entering surface S1 is parallel to the light exiting surface S2, but the present invention is not limited thereto. In addition, in the present embodiment, at least one portion of the depolarization element <NUM> has a birefringence characteristic, and the direction of the optical axis of the portion having the birefringence characteristic is not parallel to the incident direction where the light beam L is transmitted to the depolarization element <NUM>. Specifically, the depolarization element <NUM> includes a first optical element <NUM> and a second optical element <NUM>. The first optical element <NUM> is provided with a first optical axis, and the second optical element <NUM> is provided with a second optical axis. The first optical axis is not parallel to the second optical axis. For example, an included angle between the first optical axis and the second optical axis is between <NUM> degrees and <NUM> degrees, but the present invention is not limited thereto. In other words, in the present embodiment, the incident direction where the light beam L is transmitted to the first optical element <NUM> is not parallel to the first optical axis. Therefore, the light beam L is caused to generate different polarization states at different incident positions after passing through the first optical element <NUM>. In this way, when the projection apparatus <NUM> is in the polarized 3D mode, the color or brightness of a display picture is made uniform, and the user observes a 3D display picture with relatively high uniformity.

The material of the first optical element <NUM> is different from the material of the second optical element <NUM>. In the present embodiment, the first optical element <NUM> is made of a material having the birefringence characteristic, such as crystalline quartz. The second optical element <NUM> is then made of a material having a similar refractive index to the first optical element <NUM>, such as fused quartz. The direction of the first optical axis of the first optical element <NUM> is also the direction of the optical axis of crystal of the crystalline quartz. Since the fused quartz is not provided with optical axis of crystal, the second optical element <NUM> is not provided with a second optical axis. In other embodiments, the second optical element <NUM> is also made of other materials, and the direction of the second optical axis of the second optical element <NUM> is the direction of the optical axis of crystal of the material of the second optical element <NUM>.

In the present embodiment, the lighting system <NUM> further includes a focusing element <NUM>, disposed on the transmission path of the light beam L and located between the light source <NUM> and the depolarization element <NUM>. The focusing element <NUM> is, for example, a focusing lens for focusing the light beam L to allow the light beam L to pass through the depolarization element <NUM> to be received by the light homogenization element <NUM>.

For a geometrical shape of the structure, in the present embodiment, the first optical element <NUM> is provided with a first light entering surface S11 (i.e., the light entering surface S1 of the depolarization element <NUM>) and a first light exiting surface S12 which are not parallel to each other, and the second optical element <NUM> is provided with a second light entering surface S21 and a second light exiting surface S22 (i.e., the light exiting surface S2 of the depolarization element <NUM>) which are not parallel to each other. The first light exiting surface S12 is parallel to the second light entering surface S21, and the first light entering surface S11 is parallel to the second light exiting surface S22. The first light entering surface S11 is perpendicular to the incident direction of the light beam L. Specifically, the light path direction of a main light beam of the light beam L is the incident direction of the light beam L. Therefore, the shape of the first optical element <NUM> is geometrically symmetrical with the shape of the second optical element <NUM>, as viewed from a side view, and the geometrical shapes of the first optical element <NUM> and the second optical element <NUM> are, for example, like a trapezoidal cylinder, as shown in <FIG>.

In addition, in the present embodiment, a gap G is reserved between the first optical element <NUM> and the second optical element <NUM>. The first light exiting surface S12 and the second light entering surface S21 respectively form an included angle with more than <NUM> degree with the first light entering surface S11, but the present invention is not limited thereto. Specifically, the depolarization element <NUM> further includes a connection piece <NUM> connected between the first optical element <NUM> and the second optical element <NUM>. In the present embodiment, the connection piece <NUM> is, for example, of a solid ringlike structure, disposed between the first optical element <NUM> and the second optical element <NUM> to reserve the gap G between the first optical element <NUM> and the second optical element <NUM>. In other embodiments, the connection piece <NUM> is, for example, light transmittance glue which connects the first optical element <NUM> to the second optical element <NUM> in an adhering manner. The thickness of the light transmittance glue is equal to the gap G between the first optical element <NUM> and the second optical element <NUM>, but the present invention is not limited thereto. In other embodiments, the connection piece <NUM> is a clip for clamping the first optical element <NUM> and the second optical element <NUM>, or the connection piece <NUM> is omitted as needed to directly connect the first optical element <NUM> to the second optical element <NUM>. The first light exiting surface S12 is inclined to the first light entering surface S11 by more than <NUM> degree.

When the light beam L is incident to the depolarization element <NUM>, the light beam L is transmitted from the first light entering surface S11 of the first optical element <NUM> into the first optical element <NUM>, and is transmitted and emitted by the second light exiting surface S22 of the second optical element <NUM>. After being transmitted through the first optical element <NUM>, the polarization state of the light beam L is changed due to the birefringence characteristic of the first optical element <NUM>, and the change in the polarization state is based on a travel of the light beam L in the first optical element <NUM>. After being transmitted through the second optical element <NUM>, the light beam L compensates for a deflection angle caused by refraction as the light beam L passes through the first optical element <NUM>, due to the geometrical symmetry of the second optical element <NUM>. In other words, since the first optical element <NUM> is provided with the first light entering surface S11 and the first light exiting surface S12 which are not parallel to each other, the light beam L transmitted at different positions generates polarization state changes corresponding to light paths. As shown in <FIG>, when the linearly polarized light beam L is transmitted through the depolarization element <NUM> at different positions, the light beam L will be changed into light beams linearly polarized in different directions, elliptically polarized in different directions and circularly polarized in different directions. In this way, the uniformity of the polarization states of the light beam L is improved. Under the polarized 3D mode, an image with uniform color and brightness is generated on a screen, and then the user observes a 3D display picture with relatively high uniformity with polarized 3D glasses.

<FIG> is a schematic diagram of a partial lighting system 100A according to another embodiment of the present invention. Referring to <FIG>, the lighting system 100A of the present embodiment is similar to the lighting system <NUM> shown in <FIG>. The difference therebetween is that in the present embodiment, a light homogenization element 140A in the lighting system 100A is a lens array. In this way, the focusing element <NUM> shown in <FIG> is omitted from the lighting system 100A.

<FIG> is a schematic diagram of a partial lighting system 100B according to a further embodiment of the present invention. Referring to <FIG>, the lighting system 100B of the present embodiment is similar to the lighting system <NUM> shown in <FIG>. The difference therebetwen is that in the present embodiment, a depolarization element 130A in the lighting system 100B is only composed of the first optical element <NUM>, and a relative position between the light homogenization element <NUM> and the depolarization element 130A is finely adjusted to cause the light beam L to be converged and transmitted into the light homogenization element <NUM>. In this way, the lighting system 100B further reduces the cost of use of the second optical element <NUM>.

<FIG> is a schematic diagram of a partial lighting system 100B according to a further more embodiment of the present invention. Referring to <FIG>, the lighting system 100C of the present embodiment is similar to the lighting system 100A shown in <FIG>. The difference therebetwen is that in the present embodiment, the depolarization element 130A in the lighting system 100C is only composed of the first optical element <NUM>, and a placement angle of the light homogenization element 140A is finely adjusted to cause the light beam L to be transmitted into the light homogenization element 140A. In this way, the lighting system 100C further saves the material of the second optical element <NUM> and reduces the cost of the depolarization element 130A.

<FIG> is a schematic diagram of a partial lighting system 100D according to a further more embodiment of the present invention. Referring to <FIG>, the lighting system 100D of the present embodiment is similar to the lighting system 100B shown in <FIG>. The difference therebetween is that in the present embodiment, the first light entering surface S11 of the first optical element <NUM> in the lighting system 100D is not perpendicular to the incident direction of the light beam L. In the present embodiment, the first optical element <NUM> is adjusted to a specific angle by use of, for example, the refractive deflection characteristic, so as to cause the light beam L to still keep moving forwards along the same optical axis after the light beam is emitted from the first light exiting surface S12. In this way, the lighting system 100D does not need to further adjust the placement position of the light homogenization element <NUM>.

<FIG> is a schematic diagram of a partial lighting system 100E according to a further more embodiment of the present invention. Referring to <FIG>, the lighting system 100E of the present embodiment is similar to the lighting system <NUM> shown in <FIG>. The difference therebetween is that in the present embodiment, the first optical element <NUM> and the second optical element <NUM> of a depolarization element 130B in the lighting system 100E are inversely placed in the front and back direction when compared with the optical elements in <FIG>. Therefore, the light beam L generates uniform polarization states via the first optical element <NUM> and compensates for a deflection caused by the refraction via the second optical element <NUM>.

<FIG> is a schematic diagram of a partial lighting system 100F according to a further more embodiment of the present invention. Referring to <FIG>, the lighting system 100F of the present embodiment is similar to the lighting system <NUM> shown in <FIG>. The difference therebetween is that in the present embodiment, a first optical element 132A and a second optical element 134A of a depolarization element 130C in the lighting system 100F are in non-geometrical symmetry. For example, in the present embodiment, the first optical element 132A is a composite light transmittance sheet with a thicker central portion and a thinner peripheral portion, and the second optical element 134A is a composite light transmittance sheet with a thinner central portion and a thicker peripheral portion. Therefore, in the present embodiment, the light beam L still generates uniform polarization states via the first optical element 132A, and compensates for a deflection caused by the refraction via the second optical element 134A. In this way, the uniformity of the polarization states of the light beam L is improved. Under the polarized 3D mode, an image with uniform color and brightness is generated on a screen, and then the user observes a 3D display picture with relatively high uniformity with polarized 3D glasses.

<FIG> is a schematic diagram of a partial lighting system <NUM> according to a further more embodiment of the present invention. Referring to <FIG>, the lighting system <NUM> of the present embodiment is similar to the lighting system 100F shown in <FIG>. The difference therebetween is that in the present embodiment, a depolarization element 130D in the lighting system <NUM> is not provided with the second optical element 134A when compared to the depolarization element 130C shown in <FIG>. In other words, in the present embodiment, the depolarization element 130D is composed of the first optical element 132A with a thicker central portion and a thinner peripheral portion. Therefore, in the present embodiment, the light beam L still generates uniform polarization states via the first optical element 132A, and the depolarization element 130D avoids a deflection of the light beam L caused by the refraction since the surface shape of the first light exiting surface S12 of the first optical element 132A is a geometrical shape presented by taking the incident direction of the light beam L as asymmetry axis. In this way, the uniformity of the polarization states of the light beam L is improved. Furthermore, if the present invention applied in the polarized 3D mode, an image with uniform color and brightness is generated on a screen, and then the user observes a 3D display picture with relatively high uniformity with polarized 3D glasses.

Based on the above, the embodiments of the present invention at least have one of the following advantages or effects. In the lighting system and projection apparatus of the present invention, the depolarization element includes the first optical element provided with the first optical axis not parallel to the incident direction where the light beam is transmitted, and the depolarization element is located between the light source and the light homogenization element. Therefore, the light beam penetrates through the depolarization element such that the light beam has different polarization states at different positions. In this way, the uniformity of the polarization states of the light beam is improved. Furthermore, if the present invention applied in the polarized 3D mode, the image with uniform color and brightness is generated on the screen, and then the user observes the 3D display picture with relatively high uniformity with the polarized 3D glasses.

Claim 1:
Projection apparatus, comprising a lighting system (<NUM>), at least one light valve (<NUM>) and a projection lens (<NUM>);
wherein the lighting system (<NUM>) is configured to provide an illuminating light beam (LB), the lighting system comprising:
at least one light source (<NUM>) configured to provide at least one light beam (L);
a depolarization element (<NUM>) disposed on a transmission path of the at least one light beam (L); and
a light homogenization element (<NUM>), wherein the depolarization element (<NUM>) is located between the at least one light source (<NUM>) and the light homogenization element (<NUM>), and wherein light homogenization element (<NUM>) is configured to allow the at least one light beam (L) to pass so as to form the illuminating light beam (LB);
wherein the depolarization element (<NUM>) comprises a first optical element (<NUM>), and the first optical element (<NUM>) comprises a first optical axis; and
wherein the first optical element (<NUM>) is made of a material having birefringence characteristic and a direction of the first optical axis is a direction of the optical axis of crystal of the material having birefringence characteristic, and the incidence direction where the at least one light beam (L) is transmitted to the first optical element (<NUM>) is not parallel to the first optical axis; and
wherein the at least one light valve (<NUM>) is disposed on a transmission path of the illuminating light beam (LB) and configured to convert the illuminating light beam (LB) into an image light beam (LI); and
the projection lens (<NUM>) is disposed on a transmission path of the image light beam (LI) and configured to form the image light beam (LI) into a projection light beam (LP).