北京理工大学应用光学课件.ppt

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 画双目望远镜展开图。 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 在黑板上推算 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * the luminance of the image of a telescope L L =τIL the diameter of the incident light beam entering the eyes D 2. Luminous surface (1) D a: The exit pupil diameter of the instrument is smaller than the pupil diameter of the eye the subjective brightness: Compare formulae with that by the naked eye, we have: (2) D?≥ a: The exit pupil diameter of the instrument is larger than or equal to the pupil diameter of the eye Divide it by ,we have: Discussion D=a: D a The diameter of the incident rays D＝D=a; the area enhances Γ2 times； The image on the retina enhances also Γ times，and the area enhancesΓ2 times； So the illuminace will be unchanged, and since there will be losses of reflection and absorption the finally illuminace will be smaller. Da D a The diameter of the incident rays D＝Da; the area enhanced smaller than Γ2 times； The image on the retina enhances also Γ times，and the area enhancesΓ2 times； So the illuminace decreases, and since there will be losses of reflection and absorption the finally illuminace will be much smaller. D′a a The subjective brightness is reduced a little bit. 6.12 Calculation of light energy loss in optical systems 1.The loss of light energy (1)Reflection of light beam on the surface of optical components (2)The absorption of light in the medium Result: Reduce the imaging luminance Reduce the contrast of the image Form ghost image Φ Φ1” Φ1” Φ2’ Φ2” The reflection coefficient :The ratio of the reflected luminous flux and the incident luminous flux on the interface. 2. Calculation the loss by reflection If the incident luminous flux is , the