Home Theater Hacks

Hack #72. Focus Your Front Projector

Focus on a front projection system is just as important as it is on an RPTV, but the steps to get there are completely different.

Focusing a front projection CRT is a daunting task because it involves two projection systems that operate in series: an optical and beam focus.

Problems with one type of focus make it difficult to see problems with the other. As a result, sometimes people are at a loss as to which system is the problem. Add to that the need to astigmate the electron beam and adjust lens flapping (scheimpfluge [Hack #70] ), and the novice CRT setup can fall far short of the projector's optimum.

Tip

New owners confuse the two, but mechanical aim isn't the same as scheimpfluge. Mechanical aim of the CRT/lens assembly is the same as taking a telescope and physically pointing it at something. Scheimpfluge is adjusting the mounting angle of the end lens without changing where the telescope is pointed.

A good pair of binoculars that can focus at short distances is very helpful, if not essential. Do yourself a favor and obtain a pair. Also, pick up a roll of 3M easy-release blue masking tape.

Mechanical Gun Aim

If you have a projector using lens tilt rings, set them to factory specs for your projection distance before doing any aiming. First you must mechanically aim the guns properly. One way to do this is to display a white-field pattern, using a calibration DVD [Hack #62] , and shift the pattern edges equally spaced relative to the phosphor ...