Methods and apparatus for fabricating refractive blazed holograms having high single image diffraction efficiencies. A reflective blazed hologram made with a single wavelength light source may be modified for high blazed efficiencies at any desired wavelength. A reflective blazed hologram surface is replicated onto the surface of a material of higher refractive index, with a shorter wavelength of light utilized fore reconstruction. A further embodiment is to replicate a reflective blazed hologram onto the surface of a material that can be made to undergo an isotropic dimension increase or decrease. When the desired dimension change has taken place, the blazed surface thereof would again be replicated onto the surface of a suitable transparent material of the proper refractive index. Thus, refractive blazed holograms blazed for any wavelength can be obtained.
A reflection suppression system for suppressing reflection from scanned infrared focal plane arrays using a system of two or more blazed diffraction gratings in the path of radiations to the array.
A camera having a holographic indicator in which a focused image hologram is held on an image plane of the view finder of the camera and a light source is arranged to illuminate the hologram in such a direction that the light transmitted through the hologram goes out of the path of the view finder. The hologram may be also a relief type blazed hologram which has a transmitting factor (zero-order diffraction factor) higher than 90% for the light from an object and which makes the light from the reconstructed image of the hologram pass through the path of the view finder. This hologram indicator never affects the object's image when the hologram is not illuminated.
A process is disclosed which consists of choosing the wavelength of a plane incident wave to lie in the range 2d/3.ltoreq..lambda..ltoreq.2d, where d is the pitch of the slits so that there exist only two diffracted orders for each of the two half-spaces which are situated on each side of the plane of the mask, and in adjusting the angle of incidence of the plane wave so that the reflected diffracted order which is not the specularly reflected order is propagated in the direction opposite that of the incident wave.
A process for preparing blazed holograms suitable for mass-production which includes fabricating a glass or metal plate having a surface of serrated cross section, disposing the glass or metal plate in an injection mold to allow the surface of serrated cross section to constitute an inner surface of the mold. Then injecting an acrylic resin in molten form into the mold under a specific molding pressure, and removing a molded acrylic resin from the glass plate or metal plate to obtain an acrylic blazed hologram.
A pick-up device which includes a light source and a condenser lens for effecting recording and reproduction of information by projecting a light beam as collected by the condenser lens onto a recording medium. A diffraction grating is provided between the light source and the condenser lens for dividing light returning from the recording medium by a diffraction grating so as to be directed to a photo-detector, to thereby obtain an optical detection signal.
