APAS: Automatic Projector Adjustment System

• Weichen Xu
• Xi He
• Chuchen Guo
• Donghao Fang

Portable digital projectors have become increasingly popular because of their low cost, convenience and adaptability. However, as a result of portability, a significant disadvantage compared to fixed projectors is that users must adjust a portable projector’s settings before each use at a new location. The process of manually adjusting a digital projector can be complicated and time-consuming for inexperienced users. In order to make the setup process simple and easy, we have designed an “Automatic Projector Adjustment System” (APAS) for our senior design project. Typically, portable digital projectors have manual adjustment knobs to adjust image focus and shape (keystone correction). Our system automatically adjusts these control knobs, and also changes the projector’s angle relative to the screen, to achieve best results according to digital signal processing analysis of the projected image. APAS is a closed-loop control system consisting of a high-resolution camera to detect the projected image, a small computer programmed to process the detected image to determine its shape and focus parameters, motor control circuitry, and several electric motors to move the projector’s control knobs and the projector stand. To keep system cost low, we chose a Raspberry Pi computer to do the image processing and motor control tasks. Focus is adjusted by maximizing the amount of high-frequency energy in the projected image. Vertical and horizontal image borders are made parallel by adjusting the optical keystone control knob, and by turning the projector’s base, respectively. If desired, both focus and image border shape adjustments may be done while a presentation is taking place without noticeable interference. APAS is designed to operate with a specific type of digital projector, but it can easily be interfaced with a variety of portable projectors to also give them auto-adjust capability.