Patent ID: 7826143

Claim:
An optical system with a wavelength selecting device comprising, in order from an object along an optical axis of the optical system: an objective optical system composed of first optical elements having refractive power and an aperture stop; a no-power optical group composed of second optical elements having no refractive power; and an imaging device; one of the second optical elements integrally including a light transmittance portion, an absorption portion, and a reflective portion; the light transmittance portion substantially transmitting light over a predetermined wavelength range; the absorption portion being substantially non-transparent with respect to light of longer wavelength above λ R10 by use of an absorption filter; and the reflective portion being substantially non- transparent with respect to light of shorter wavelength below λ V50 by use of an interference film, wherein the following conditional expressions are satisfied: 410≦λ V50 <430 650<λ R10 <750 where λ V50 denotes a wavelength in nm of shorter wavelength light for which transmittance of the one second optical element is 50% and λ R10 denotes a wavelength in nm of longer wavelength light for which transmittance of the one second optical element is 10%, wherein the one second optical element has a function of cutting off a higher spatial frequency than a resolution limit of the imaging device, and wherein the following conditional expressions are satisfied: D L /Y<0.2 D L >0.5 where D L denotes a thickness in mm along the optical axis of the one second optical element having the function of cutting off a higher spatial frequency than the resolution limit of the imaging device, and Y denotes a diagonal length in mm of the imaging device.