User`s manual

1 Introduction

Due to the advances in semiconductor technology, today’s display projectors

can incorporate fairly sophisticated digital processing algorithms for various

enhancements to the visual appearance. Moreover, there is an increasing preva-

lence of portable projectors that beneﬁt from fast, automated setup. One desired

functionality is keystone/tilt correction. In other words, even when the projec-

tor is tilted, the projector should be able to “pre-warp” the image so that its

output appears unskewed. Figure 1 shows what is meant by the keystone eﬀect

and what its desired correction should look like

Figure 1: Keystone Correction In Vertical Direction

In this project, we project the output of a camera, connect the camera’s

output to the FPGA (Field Programmable Gate Array) board, and the FPGA

board’s VGA output to the projector. We mount an accelerometer on the

projector and measure its signals to determine the projector’s tilt angle on two

axes. We then run a perspective transformation algorithm on the FPGA that

warps the camera output based on the tilt angles and produces the results at the

VGA output for the projector to display. We also provide a manual correction

mode so that any desired correction can be achieved. This manual correction

mode is exposed to the user via the arrow keys and switches on the FPGA kit.

This is of use in mainly two cases:

• The automatic correction obtained using the accelerometer readings is

unsatisfactory or inadequate.

• The user desires to correct for projector orientation in the third axis, or

in the case when the screen is non-vertical.

https://en.wikipedia.org/wiki/File:Vertical-keystone.jpg