Micro lens array unit having at least one of first and second micro lens arrays movable for changing the effective focal length of the micro lens array unit and liquid crystal display projection device using same

An exemplary MLA unit for use in a projection device is disclosed. The projection device includes an LCD panel. The LCD panel includes a number of pixels each having an opening. The MLA unit includes a first MLA, and a second MLA. The first MLA includes a number of first micro lenses each configured for focusing incident light into the opening of a respective pixel of the LCD panel. The second MLA includes a number of second micro lenses each aligned with a respective first micro lens of the first MLA so as to form a micro lens system. The second MLA is movable so as to change the effective focal length of the lens systems.

BACKGROUND

1. Technical Field

The invention relates to projection technology and, in particular, relates to a micro lens array (MLA) unit used in a liquid crystal display (LCD) projection device, and an LCD projection device.

2. Description of the Related Art

LCD projectors, especially 3LCD projectors, are capable of reproducing bright, natural images that are easy on eyes, and therefore pleasant to watch. These LCD projectors typically employ an LCD panel (three in 3LCD type) for image generation, and the brightness of the reproduced images is mainly determined by the aperture ratio of the LCD panel (the greater the aperture ratio, the higher the brightness). A MLA unit is normally used to increase the brightness. The MLA includes a number of micro lenses, each of which is dedicated to focus incident light into the opening of respective pixels of the LCD panel, thereby increasing the aperture ratio of the LCD panel. However, as the incident light is concentrated by the MLA, peripheral aberrations such as distortion may become greater. In other words, the MLA may decrease the contrast of the reproduced images. It has been challenging to achieve both satisfactory brightness and desirable contrast.

Therefore, it is desirable to provide a MLA unit, and an LCD projection device, which can overcome the above mentioned problems.

SUMMARY

In an exemplary embodiment, a MLA unit used in a projection device is disclosed. The projection device includes an LCD panel. The LCD panel includes a number of pixels each having an opening. The MLA unit includes a first MLA, and a second MLA. The first MLA includes a number of first micro lenses each configured for focusing incident light into the opening of a respective pixel of the LCD panel. The second MLA includes a number of second micro lenses each aligned with a respective first micro lens of the first MLA so as to form a micro lens system. The second MLA is movable so as to change the effective focal length of the lens systems.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present MLA unit and LCD projection device will now be described in detail with reference to the drawings.

Referring toFIG. 1, a 3LCD projection device10, according to an exemplary embodiment, includes an illumination unit110, a color splitting system120, three MLA units130, three LCD panels140, a prism150, and a projection lens160. The illumination unit110is configured to provide illumination. The color splitting system120is placed in the path of the light from the illumination unit110to separate the light into three beams of color light, e.g., red (R), green (G), and blue (B), and is configured to direct each beam of color light along a respective color channel/path. The three MLA units130and the three LCD panels140are set in the paths of the three beams of color light, respectively, in the color splitting system120. The MLA units130are configured to increase the aperture ratio of the three LCD panels140respectively. The LCD panels140are configured to modulate the three beams of color light into three color components, e.g., R, G, and B, of visual images, based on input signals. The prism150such as an X-cube is configured to combine the three modulated color components from the three LCD panels140into the visual images. The projection lens160is configured to project the combined visual images from the prism150onto a screen or the like.

The illumination unit110includes a short arc lamp112, two lens arrays114, a polarization converter116, and a condensing lens118. The short arc lamp112, such as a high pressure mercury lamp, a metal halide lamp, or a xenon lamp, is configured to generate light. The two lens arrays114, the polarization converter116, and the condensing lens118are set in the path of the light generated by the short arc lamp112. The two lens arrays114, also known as “fly's eye lens arrays”, are configured to homogenize the generated light form the short arc lamp112. The polarization converter116typically includes a polarization beam splitter (PBS) array1162, and a number of half-wave plates1164. The PBS array1162is configured for splitting the homogenized light from the lens arrays114into p-polarized light. The half-wave plates1164are attached at predetermined points on the PBS array1162so that p-polarized light through the PBS array1162is converted into s-polarized light. The condensing lens118is configured to condense the s-polarized light from the polarization converter116to form s-light illumination. The illumination unit110may further includes a reflective mirror110a, interposed between the two lens arrays114, for example, configured to reduce the size of the illumination unit110.

The color splitting system120includes a series of color splitting members122such as dichroic mirrors or dichroic prisms, and light steering members124such as reflective mirrors or prisms. The color splitting members122and the light steering members124are arranged so as to have the capability of color splitting and light steering. More specifically, the color splitting system120can further include two relay lenses126for light relay.

Referring toFIG. 2, the LCD panel140is a thin film transistor (TFT) LCD panel, and typically includes a TFT substrate142(ITO glass), a liquid crystal layer144, and an opposite substrate146. The TFT substrate142and the opposite substrate146seal the liquid crystal layer144. This LCD panel140is divided into a number of pixels148, each of which has a TFT14a, formed on the TFT substrate142and acting as a switch of the corresponding pixel148. In addition, a black matrix14b(nontransparent portion) is patterned on the opposite substrate146so as to protect the TFTs14afrom light, but leaving an opening14c(transparent portion) in each pixel148.

The MLA unit130includes a first MLA132, a second MLA134, an actuator136, and a controller138. The first MLA132includes a number of first micro lenses13a, each of which is configured to focus incident light into the opening14aof a respective pixel148of the LCD penal140. The second MLA134also includes a number of second micro lenses13b, each of which is aligned with a respective first micro lens13aso as to form a micro lens system13c. The controller138is configured for controlling the actuator136to force the second MLA134to move, along the optical axis thereof, thereby changing the effective focal length of the micro lens systems13c.

In this embodiment, the first and second MLA132,134are made of quartz crystal. The first MLA132is attached to the opposite substrate146using adhesive agent13d, and the second MLA134are movably set at the light incident side of the LCD panel140. The actuator136and the controller138are provided by a micro-electro-mechanical system (MEMS).

Alternatively, both the first MLA132and the second MLA134can be movably set too; or only the first MLA132is movably set. The second MLA134can be placed at the light emitting side of the LCD panel140(seeFIG. 3). In addiction, this MLA unit130can be applied to a single-panel LCD projector (typically including an illumination unit, a MLA unit, an LCD panel, and a projection lens) too.

When the quotient of the effective focal length divided by the bore of a lens employed in the LCD projection device, a.k.a. the F value, becomes smaller, the brightness of reproduced images increases, but the contrast thereof decreases. Conversely, if the F value increases, the brightness suffers, but the contrast improves. In the above-mentioned embodiments, the lens systems13cof the MLA unit130are configured to adjust the F value thereof so as to obtain a desirable brightness and contrast.

It will be understood that the above particular embodiments and methods are shown and described by way of illustration only. The principles and the features of the present invention may be employed in various and numerous embodiments thereof without departing from the scope of the invention as claimed. The above-described embodiments illustrate the scope of the invention but do not restrict the scope of the invention.