ILLUMINATION SYSTEM AND PROJECTION DEVICE

An illumination system includes a light source module, a first lens array, a condensing element, a second lens array, and a prism element. The light source module is configured to provide an illumination beam. The first lens array is disposed on the transmission path of the illumination beam. The condensing element is disposed on the transmission path of the illumination beam. The first lens array is located between the light source module and the condensing element. The second lens array is disposed on the transmission path of the illumination beam. The prism element is disposed on the transmission path of the illumination beam. The second lens array is located between the condensing element and the prism element, wherein the surface area of the second lens array is greater than the surface area of the first lens array.

BACKGROUND

Technology Field

The disclosure relates to an optical system and a display device, and particularly, to an illumination system and a projection device having the illumination system.

Description of Related Art

Projection devices are display devices for generating a large-area image and have been constantly improved along with the evolution and innovation of science and technology. The imaging principle of a projection device is to convert the illumination beam generated by the illumination system into an image beam through a light valve, and then the image beam is projected to a projection target (e.g., a screen or a wall) through a projection lens to form a projection image.

In pursuit of applying a compact projection device to a pico-projection device so as to be configured to a head-mounted display, the illumination system of the pico-projection device has gradually evolved from the early Red/Green/Blue LED light beams forming three pathways to the current Red and Blue/Green LED light beams forming two pathways, or to Red and Blue and Green LED light beams forming one pathway. All these three structures adopt a collimating lens to allow the light source provided by the light-emitting diode to be incident on the lens array in a parallel manner, and then the light beam on the lens array is focused on the imaging element of the light valve through the condensing lens. However, to implement the compact design with the smallest volume, the lowest number of light sources is adopted in design. Nonetheless, because some color light sources are single light sources and located at diagonally opposite positions, the projected image may have obvious color nonuniformity.

SUMMARY

The disclosure provides an illumination system and a projection device, capable of improving the uniformity of the illumination beam and the uniformity of different colors.

Other objectives and advantages of the disclosure can be further understood from the technical features disclosed in the disclosure.

To achieve one, part of, or all of the above purposes or other purposes, the disclosure provides an illumination system, which includes a light source module, a first lens array, a condensing element, a second lens array, and a prism element. The light source module is configured to provide an illumination beam. The first lens array is configured on a transmission path of the illumination beam. The condensing element is disposed on the transmission path of the illumination beam. The first lens array is located between the light source module and the condensing element. The second lens array is disposed on the transmission path of the illumination beam. The prism element is disposed on the transmission path of the illumination beam. The second lens array is located between the condensing element and the prism element. A surface area of the second lens array is greater than a surface area of the first lens array.

To achieve one, part of, or all of the above objectives or other objectives, the disclosure further provides a projection device including an illumination system, a light valve, and a projection lens. The illumination system is configured to provide an illumination beam. The illumination system includes a light source module, a first lens array, a condensing element, a second lens array, and a prism element. The light source module is configured to provide the illumination beam. The first lens array is disposed on a transmission path of the illumination beam. The condensing element is disposed on the transmission path of the illumination beam. The first lens array is located between the light source module and the condensing element. The second lens array is disposed on the transmission path of the illumination beam. The prism element is disposed on the transmission path of the illumination beam. The second lens array is located between the condensing element and the prism element. The light valve is disposed on the transmission path of the illumination beam for converting the illumination beam into an image beam. The projection lens is disposed on the transmission path of the image beam and configured for projecting the image beam out of the projection device. A surface area of the second lens array is greater than a surface area of the first lens array.

In summary, the embodiments of the disclosure have at least one of the following advantages or effects. In the illumination system and the projection device of the disclosure, the illumination system includes a light source module, a first lens array, a condensing element, a second lens array, and a prism element. The first lens array is disposed between the light source module and the condensing element and configured to control the magnitude (size) of the cross-sectional area of the illumination beam provided by the light source module to match the magnitude (size) of the surface area of the light valve receiving the illumination beam, the second lens array is disposed between the condensing element and the prism element and configured to change and uniform the light patterns of various colors in the illumination beam. Accordingly, the uniformity of the illumination beam and the uniformity of different colors can be improved, and the phenomenon of the nonuniformity of the color light emitted by the light emitting element can be improved.

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

DESCRIPTION OF THE EMBODIMENTS

FIG.1is a schematic view of a projection device according to an embodiment of the disclosure. Referring toFIG.1, in one embodiment, a projection device10may be applied to a head-mounted display. The embodiment provides the projection device10including an illumination system100, a light valve60, and a projection lens70. The illumination system100is configured for providing an illumination beam LB. The light valve60is disposed on the transmission path of the illumination beam LB and configured for converting the illumination beam LB into an image beam LI. The projection lens70is disposed on the transmission path of the image beam LI and configured to project the image beam LI out of the projection device10to a projection target (not shown), such as a screen, a wall or a waveguide element of a head-mounted device.

In the embodiment, the light valve60is a reflective light modulator, such as a liquid crystal on silicon panel (LCoS panel), a digital micro-mirror device (DMD), and the like. The disclosure does not limit the type and mode of the light valve60. The detailed steps and the implementation method for the light valve60to convert the illumination beam LB from the illumination system100into the image beam LI can be taught, suggested and implemented from ordinary knowledge in the technical field, which may not be repeated herein. In the embodiment, the number of the light valve60is one, for example, the projection device10using a single digital micro-mirror device. The light valve60can also adopt a liquid crystal silicon-on-chip panel. In the embodiment, the projection device10further includes a protective cover80(refer toFIG.2), which is configured to prevent the light valve60from being in contact with dust and affecting the optical effect. The material of the protective cover80is glass or plastic, for example.

The projection lens70includes, for example, one optical lens or a combination of multiple optical lenses having dioptric power, such as various combinations of non-planar lenses such as biconcave lenses, biconvex lenses, meniscus lenses, convex-concave lenses, plano-convex lenses, and plano-concave lenses. In one embodiment, the projection lens70may further include a flat optical lens, which projects the image beam LI from the light valve60to the projection target in a reflective manner. The disclosure does not limit the type and mode of the projection lens70.

FIG.2is a schematic view of an illumination system according to an embodiment of the disclosure.FIG.3is a schematic view of a light source module according to an embodiment of the disclosure. Referring toFIG.2andFIG.3, the illumination system100of the embodiment can be applied to at least the projection device10shown inFIG.1, which is illustrated as an example in the subsequent paragraphs. In the embodiment, the illumination system100includes a light source module110, a first lens array120, a condensing element130, a second lens array140, and a prism element150. The light source module110is configured to provide the illumination beam LB. In the embodiment, the light source module110includes a light emitting element112and a collimating lens group114. The light emitting element112is, for example, an integrated light-emitting diode module and provides red light, green light, and blue light. Specifically, the light emitting element112is formed by an arrangement of red, green, green, and blue light-emitting diodes, the red and blue light-emitting diodes are located at diagonal positions, and the two green light-emitting diodes are located at diagonal positions, as shown inFIG.3. Therefore, it is possible to implement the compact design with the smallest volume, but the disclosure is not limited thereto. In the embodiment, the collimating lens group114includes at least one optical lens, and the collimating lens group114is configured to provide the parallel illumination beam LB to the first lens array120, but the disclosure is not limited thereto.

The first lens array120is disposed on the transmission path of the illumination beam LB and configured to control the magnitude of the cross-sectional area of the illumination beam LB provided by the light source module110to match the magnitude of the surface area of the light valve60receiving the illumination beam LB. For example, the magnitude (size) of the cross-sectional area of the illumination beam LB passing through the first lens array120is equal to or approximates to the magnitude (size) of the surface area of the light valve60receiving the illumination beam LB.

The first lens array120includes multiple microlenses, which may be located on one side of the first lens array120or on two opposite sides of the first lens array120, and the disclosure is not limited thereto.

The condensing element130is disposed on the transmission path of the illumination beam LB, and the first lens array120is located between the light source module110and the condensing element130. In the embodiment, the condensing element130has a reflective surface132, e.g. coated with a reflective film, for reflecting the illumination beam LB to be transmitted to the second lens array140.

The second lens array140is disposed on the transmission path of the illumination beam LB and configured to change and uniform the light patterns of each color (red, green, and blue) in the illumination beam LB, thereby improving the uniformity of the illumination beam LB and the uniformity of different colors, so that the phenomenon of the nonuniformity of the color light emitted by the light emitting element112can be prevented. The second lens array140includes multiple microlenses located on opposite sides of the second lens array140. In the embodiment, physically, the surface area of the second lens array140is greater than the surface area of the first lens array120. In addition, the area of the illumination beam LB received by the light incident surface of the second lens array140is also greater than the area of the illumination beam LB received by the light incident surface of the first lens array120.

FIG.4AtoFIG.4Care schematic views of part of lens arrays according to different embodiments, respectively. Referring toFIG.2andFIG.4AtoFIG.4C, in different embodiments, microlenses M of the first lens array120and the second lens array140may have different arrangement designs according to different situations. For example, as shown inFIG.4A, the microlenses M of the first lens array120and the second lens array140may be disposed in a hexagonal arrangement (or in a circular arrangement). Alternatively, as shown inFIG.4B, the microlenses M1of the first lens array120and the second lens array140may be disposed in a rectangular arrangement. Alternatively, as shown inFIG.4C, the microlenses M2of the first lens array120and the second lens array140may be disposed in a spiral arrangement (only the arrangement positions are illustrated inFIG.4Cfor easy illustration), but the disclosure is not limited thereto.

FIG.5is a schematic view of part of the enlarged illumination system ofFIG.2. Referring toFIG.2andFIG.5, the prism element150is disposed on the transmission path of the illumination beam LB, and the second lens array140is located between the condensing element130and the prism element150. The prism element150is, for example, a total internal reflection prism (TIR prism) and configured to guide the illumination beam LB to be transmitted to the light valve60and guide the image beam LI to the projection lens70(as shown inFIG.1). In detail, the prism element150has a first surface and a light exit surface, the first surface of the prism element150faces the second lens array140, and the light exit surface of the prism element150faces the light valve60. The first surface of the prism element150is configured to receive the illumination beam LB, and the illumination beam LB enters the prism element150and is transmitted to the light valve60. When the light valve60converts the illumination beam LB into the image beam LI, the image beam LI enters the prism element150again, and the image beam LI is reflected by the first surface of the prism element150, leaves the prism element150, and is transmitted to the projection lens70.

In addition, in the embodiment, an included angle A is formed by the extending direction (this extending direction is perpendicular to the normal direction of the surface of the second lens array140) of the second lens array140and the extending direction (this extending direction is perpendicular to the normal direction of the surface of the light valve60) of the light exit surface of the prism element150. The light exit surface of the prism element is parallel to the surface of the light valve60. Specifically, the illumination system100may further include a spacing element160, and there is a distance between the spacing element160and the second lens array140.

The spacing element160is disposed between the second lens array140and the prism element150so that the optical path difference of the illumination beam LB in the air layer, resulting in the degraded quality of the projection image is prevented. Note that in the embodiment, the size (i.e., the optical area) of the second lens array140can be determined according to the magnitude (size) of the surface of the light valve60and the light-receiving angle thereof. Accordingly, the use efficiency of light can be improved, as shown inFIG.5, and the uniformity of the illumination beam LB can be further improved.

FIG.6is a schematic view of an illumination system according to another embodiment of the disclosure. Referring toFIG.6, an illumination system100A of the embodiment is similar to the illumination system100shown inFIG.2. What differs is that in the embodiment, a collimating lens group114A of the light source module110A includes a compound parabolic concentrator (CPC) configured to transform the light of different angles emitted by the light emitting element112into parallel light through the curved surface of the compound parabolic concentrator. Furthermore, the first lens array120A is directly connected to the compound parabolic concentrator. Therefore, the volume of the illumination system100A can be further downsized with favorable optical effects as well. In another embodiment, the first lens array120A can also be directly configured and connected to the light incident surface of the condensing element130. Accordingly, the uniformity of the illumination beam and the uniformity of different colors can be improved, and the phenomenon of the nonuniformity of the color light emitted by the light emitting element112can be prevented.

In summary, in the illumination system and the projection device of the disclosure, the illumination system includes a light source module, a first lens array, a condensing element, a second lens array, and a prism element. The first lens array is disposed between the light source module and the condensing element and configured to control the magnitude of the cross-sectional area of the illumination beam provided by the light source module to match the magnitude of the surface area of the light valve receiving the illumination beam, the second lens array is disposed between the condensing element and the prism element and configured to change and uniform the light patterns of various colors in the illumination beam, and the surface area of the second lens array is greater than the surface area of the first lens array. Accordingly, the uniformity of the illumination beam and the uniformity of different colors can be improved, and the phenomenon of the nonuniformity of the color light emitted by the light emitting element can be prevented.