Pinhole optics.
The pinhole camera may often be overlooked because of its apparent simplicity. However, it is a useful and practical device which offers freedom from distortion and virtually infinite depth of field. Its astigmatism can be corrected by proper choice of aperture, and its angular field can be made to exceed 90 degrees . With modern light sources, films, and detectors, even the pinhole's low aperture need not be an important limitation.
Young
M
M