Abstract: A spectrometer in accordance with the present disclosure may provide multiple optical paths from the inputs to the camera, where the paths are as nearly identical as possible. For example, a spectrometer in accordance with the present disclosure may include multiple inputs, input optics, a diffraction grating, output optics, and a camera. The multiple inputs may be imaged onto different sections of the camera using the same input optics, the same diffraction grating, and the same output optics.

Abstract: A system includes a light source and a grating cube. The grating cube includes a transmission volume holographic grating positioned between two prisms. The transmission volume holographic grating diffracts part of a light source emission toward a reflective surface, producing diffracted light. At least some of the diffracted light is reflected off of the reflective surface, producing feedback light. The feedback light is fed back to the light source, thereby causing the light source emission to have the same wavelength as the feedback light.

Abstract: A multi-element diffraction grating is disclosed. The multi-element diffraction grating may be configured to diffract incident radiation with high dispersion using at least two holographic optical elements. The multi-element diffraction grating may include a first volume phase grating that is one of the holographic optical elements. The multi-element diffraction grating may also include at least one additional volume phase grating that is the second holographic optical element. The first volume phase grating and each of the additional volume phase gratings may be positioned relative to each other such that the radiation propagates through and is diffracted by the first volume phase grating and each of the additional volume phase gratings.

Abstract: A fingerprint reader is described. The fingerprint reader includes an illumination source that produces light and a camera. An optical window is also part of the reader. The window is positioned so that light from the illumination source passes through the optical window and then is reflected to the camera for imaging a person's fingerprint. A filter may be positioned on or proximate to the optical window. The filter prevents ambient light from reaching the camera. In some situations, the filter will be a dielectric mirror, a dielectric filter, a holographic mirror, a holographic filter, a dichroic mirror or a dichroic filter.

Abstract: An eyepiece assembly for use in a rifle scope may include an eyepiece that is made of a material that is transparent to light. A holographic reticle may be positioned within the eyepiece. The eyepiece assembly may also include a chrome reticle. The chrome reticle may be positioned so that the chrome reticle is aligned with the holographic reticle. A cover portion may be attached to the eyepiece.

Abstract: A diffraction grating having multiple holographic optical elements (HOEs), including a Dickson grating and at least one other volume phase grating (VPG). In typical embodiments, the multi-HOE grating is implemented to provide high dispersion, at least substantially uniform diffraction efficiency and at least substantially equal diffraction efficiencies for all polarizations across a wide range of wavelengths. The refractive index modulations of the Dickson grating's volume phase medium preferably have significantly greater spatial frequency than those of each other VPG of the multi-HOE grating. Typical embodiments of the multi-HOE grating can be manufactured at low cost with sufficiently small size and high dispersion (for both S-polarized and P-polarized radiation) to be useful in Dense Wavelength Division Multiplexing (DWDM) applications and other applications requiring high dispersion. The multi-HOE grating can be implemented as a transmissive or reflective grating.

Abstract: A fingerprint reader is described. The fingerprint reader includes an illumination source that produces light and a camera. An optical window is also part of the reader. The window is positioned so that light from the illumination source passes through the optical window and then is reflected to the camera for imaging a person's fingerprint. A filter may be positioned on or proximate to the optical window. The filter prevents ambient light from reaching the camera. In some situations, the filter will be a dielectric mirror, a dielectric filter, a holographic mirror, a holographic filter, a dichroic mirror or a dichroic filter.

Abstract: A multi-element diffraction grating is disclosed. The multi-element diffraction grating may be configured to diffract incident radiation with high dispersion using at least two holographic optical elements. The multi-element diffraction grating may include a first volume phase grating that is one of the holographic optical elements. The multi-element diffraction grating may also include at least one additional volume phase grating that is the second holographic optical element. The first volume phase grating and each of the additional volume phase gratings may be positioned relative to each other such that the radiation propagates through and is diffracted by the first volume phase grating and each of the additional volume phase gratings.