In general the resolusion of X-ray detector, such as a proportional counter, is very low, and it is very difficult to determine accurately the position of individual X-ray sources. Bamboo collimator (modulation collimator) is one of the wonderful methods to ascertain the direction of incident X-rays.

A bamboo collimator is such a device that two or so bamboo screens are attached in front of the window of the X-ray detector. X-ray sources appear and disappear through gaps of bamboo screens, and its pattern enable us to detemine the position of X-ray sources accurately. In 1963 Minoru Oda hit on and designed such a bamboo (modulation) collimater, which resembles a bamboo screen, a summer scenery in Japan, and is named a bamboo collimator. Using this bamboo collimator, the resolution of X-ray detector was remarkably improved (from about one degree upto one arc-minuite).

The positional accuracy and sensitivity can be greatly improved, if the X-rays are collected to its focus via a reflector, similar to an optical telescope. In addition, if we put a two dimensional digital detector such as a CCD detector, even X-ray images can be taken, and various X-ray observations become possible. X-ray telescope (X-ray reflector) is such a device that collects X-ray photons to its focus, using a special reflector.

Reflector in ASCA