An aperture stop assembly for use in an electromagnetic radiation system may include an aperture stop made of a material at least partly transparent to an applied electromagnetic radiation. At least a portion of the aperture stop may be formed at an edge of an aperture to deflect electromagnetic radiation into the at least partially transparent material.

Holographic optical elements are utilized for discriminating between monochromatic, coherent radiation and broadband, noncoherent radiation in passive coherent radiation detection systems such as aircraft warning systems and submarine laser communication systems. Coherent laser light can possess an extremely high energy density, directivity, (i.e., collimation), and a very narrow wavelength band when compared to natural or man-made, broadband white light sources. The concentration of laser light energy by a holographic optical element at the detector stage is a consequence of its special characteristics. Moreover, equally important, the diffracted light distribution in the neighborhood of the detector possesses a unique, bright geometric pattern not readily obtained with noncoherent sources. This geometric pattern is used as a laser wavelength detector for determination of the incident angular direction of the laser beam, as well as a coherent/noncoherent light discriminator. Since it is a passive component, a holographic optical element detects pulsed as well as continuous wave illumination, and some designs are basically independent of wavelength.

A device for radiation detection over a broad field, especially for laser radiation detection. The device comprises a photodetector associated with an optical receiver formed by two diaphragms which delimit the field, and an optical diffusing element. In a preferred embodiment, a diffusing paint is deposited on a flat surface of a mechanical part, and a mirror for reflecting the diffused radiation makes it possible to mount at the rear end of the device either the photodetector or an optical fiber terminal to which the photodetector is remotely coupled.

A voltage detector comprises a light modulator which employs an electro-optic material whose refractive index changes according to the voltage developing in an object to be measured. A transparent anti-reflection film having a refractive index and thickness which are predetermined on the bases of a refractive index of the electro-optic material and a wavelength of incident light is formed on both light entrance and exit surfaces of the electro-optic material.

A reflected radiance sensor is held in a spaced-apart relationship with a surface so the field of view of the sensor intersects the surface so that the radiation reflected off the surface can be detected and measured. The sensor is configured to detect only reflected radiation so that the reflected radiation is accurately measured without any direct incident component. A support structure is utilized to hold the detector of the sensor in place. The support structure is preferably made of material that is substantially invisible (i.e., transparent) to the radiation wavelength band of interest. The design of a support structure in accordance with the present invention is not limited to any one design, but may be designed for optimum performance in a particular application.