Do all optical instruments use lenses?

No, not all optical instruments use lenses. There are a variety of optical instruments that use other optical elements such as mirrors, prisms, and gratings.

For example, telescopes use mirrors to focus light from distant objects. Binoculars use prisms to create two images of an object, one for each eye. Spectrometers use gratings to spread out light into a spectrum.

While lenses are used in many optical instruments, they are not the only optical element that can be used. Different optical elements have different properties and advantages, and the choice of optical element depends on the specific application.