I'm guessing it's a light bulb shining through a liquid crystal display.

Does yours not have the focus wheel?

Ah! Good point.

Yes, it does have a focus wheel.

But, there may be more to it than that. The projection lens is about 10mm in diameter, but the projected image is about 20 times that size, and the image itself is razor-sharp. I can't imagine LEDs being bright enough to go 20x magnification and still be visible on the opposite wall 15-20 feet away. The image itself is laser-red in color, and if the beam crosses my line of sight it is absolutely blinding, but only momentarily -- no after-images or spots or anything like that.

OK, Wikipedia to the rescue:

Low-brightness projection clocks

Most modern projection clocks use a red LED-based projector, and also an ordinary LED or LCD display.

I'd still like some mechanical details on how they work. Do the LEDs themselves project through the lens, or is there some sort of mask back-lit by the LEDs? Is it one LED for the whole display, or a separate LED for each digit, or a separate LED for each segment of each digit? If it is a back-lit mask, what mechanism changes the mask as the digits change?

Patrick, where are you in my hour of need?

tanstaafl.

?

You can get really bright LEDs now that are more than sufficient to make the clock work. Chances are that they're using some medium brightness but cheap LEDs and therefore have several of them inside the clock. You could use a single ultra bright one but they're $$$.

The LEDs provide the illumination and shine through the LCD and then the lens. Thats pretty much it. The electronics portion is a near enough a standard LCD clock but wired to light up the LEDs when you press a button.

HAHAHAHAA!!! Thanks! I needed that!

lol @ l0ser