[Ultra-small Projectors Teardown] Fly-eye Lens Commands Attention [Part 2]

Dec 29, 2008
Nikkei Electronics Teardown Squad
Fig 1: The optical module (upper right) was removed from the heat dissipation copper sheet (lower right) to which the RGB LEDs were attached. The mainboard is seen on the lower left.
Fig 1: The optical module (upper right) was removed from the heat dissipation copper sheet (lower right) to which the RGB LEDs were attached. The mainboard is seen on the lower left.
[Click to enlarge image]
Fig 2: The LED light sources of the PK101 consist of red (R) green (g) and blue (B) LEDs arranged in this order from right. The flexible board on which the LEDs are mounted is printed with the "Young Optics" logo.
Fig 2: The LED light sources of the PK101 consist of red (R) green (g) and blue (B) LEDs arranged in this order from right. The flexible board on which the LEDs are mounted is printed with the "Young Optics" logo.
[Click to enlarge image]
Fig 3: The inner side of the upper metal chassis: The attached sheet is believed to be for heat dissipation.
Fig 3: The inner side of the upper metal chassis: The attached sheet is believed to be for heat dissipation.
[Click to enlarge image]
Fig 4: The inside of the optical module. It is equipped with the LED light sources (upper side), the DMD as display element (lower right) and the projection lens (lower left). The DMD, which was taken out together with the LEDs, is seen in the center.
Fig 4: The inside of the optical module. It is equipped with the LED light sources (upper side), the DMD as display element (lower right) and the projection lens (lower left). The DMD, which was taken out together with the LEDs, is seen in the center.
[Click to enlarge image]
Fig 5: The fly-eye lens has a processed surface and is composed of small lenses arranged in an array.
Fig 5: The fly-eye lens has a processed surface and is composed of small lenses arranged in an array.
[Click to enlarge image]

The Nikkei Electronics Teardown Squad opened the chassis of the PK101 and took out the optical module (See related article). Before breaking down the module, we removed the copper sheet attached to its periphery (Fig 1).

The red, green and blue (RGB) LED light sources bonded to the copper sheet came off together with the sheet. The flexible substrate on which the light sources were mounted was printed with the logo of Young Optics Inc of Taiwan (Fig 2). We could not identify the manufacturer of the LEDs, but they were assumed to have been "made by a Taiwanese manufacturer," according to a marketer of an LED manufacturer.

The copper sheet attached to the module dissipates heat generated from the back side of the LED light sources. It seemed that the projector was designed to diffuse heat by conducting it to the metal chassis on the upper side of the projector via the copper sheet. Because of this setup, the PK101 has no air cooling fins or air holes. It only has holes for a speaker.

Furthermore, a sheet, which was provided probably for heat dissipation, is attached to the inner side of the chassis in contact with the copper sheet (Fig 3). The sheet is likely to have been provided to improve the heat dissipation performance by effectively conducting heat to the chassis.

The LEDs are not the only heat source, however. The driver LSI for DMD serving as the display device and the image processing LSI are also "major heat sources," one engineer said. Thus, similar sheets are attached to the inner side of the metal chassis in a manner that they touch the DMD driver LSI and the image processing LSI.

Attention focused on fly-eye lens

We finally opened the optical module. The module "sticks to the basics" of optical design, said an engineer who is familiar with projectors. But its optical parts were quite distinctive. The engineer focused on the fly-eye lens, which has an array of small lenses on the surface (Fig 4 & 5).

It seemed that the lens was employed as an "integrator" to reduce variations in the brightness of images by equalizing the luminance of light incident to DMD display device. Projectors with DMD generally use a rod lens as an integrator, the engineers said.

Each lens in the fly-eye lens is shaped like a parallelogram. It was "designed probably to efficiently introduce light into each of the micron-order mirrors in the DMD," the engineer said. In addition to this lens, the mirror located near DMD was tilted in horizontal and vertical directions so that light effectively enters the DMD micromirrors.

This wrapped up the breakdown of the PK101. And we started to tear down the MPro110 of 3M.