Disclosed is a novel assembly and method that enables a user to collimate a focused Cassegrain telescope. The assembly, having a secondary mirror and support baffle, comprising an axle, a bearing, and hub, enables a user to precisely rotate or freely spin a Cassegrain telescope's secondary mirror about its optical axis. Incident to freely spinning the telescope's secondary mirror, the user may peer into the telescope's eyepiece and observe a focused image that may wobble, or remain stable, dependent upon how well the telescope's mirrors are aligned. Further, the assembly's eyepiece, comprising a reticle design, enables the observer to measure the magnitude and direction of image shift incident to the secondary mirror spinning. Lastly, the assembly, comprising a radially marked collimating faceplate, and radially marked collimating knob screws, enables a user to make specific adjustments to the telescope's secondary mirror, compensating for the observed image shift, precisely collimating the telescope.

A portrait lens configuration for meeting handheld device form factor constraints. First and second meniscus lenses each have a reflective surface to provide internal reflections for transmitting light toward a focal plane. A third lens is positioned between the meniscus lenses and the focal plane. The first lens includes an anterior concave surface having a reflective material extending over a portion thereof. Light received by the first meniscus lens can be transmitted therethrough. The reflective material is positioned along the anterior concave surface to receive light transmitted therethrough and reflected back from the second lens. In an associated method the first meniscus lens is positioned to receive light through a first of two opposing refractive surfaces. After each lens provides an internal reflection, reflected light is transmitted through the second of the two opposing surfaces and then through a bore positioned within the second lens to the third lens.

A spectrometer with an unobstructed, Schmidt reflector is described. The spectrometer may include a Schmidt corrector and a dispersive element as separate components. Alternatively, the Schmidt corrector and dispersive element may be combined into a single optical component. The spectrometer may further include a field-flattener lens.

A multi-band/multi-polarization reflective or catadioptric optical system yields differing effective focal lengths (EFLs) per band/polarization. This approach could be used to create an imaging system, for example. In such case, a sensor (imager, spectrometer, diode, etc.) is located at the one or more focal planes. On the other hand, it could also be used to create a projecting system or hybrid projecting and imaging system by locating an emitter such as an LED, laser, etc.) at the image or focal plane. The system employs polarizers and/or dichroic coatings nano patterns to create different focal lengths and/or fields of view using the same mirrors and/or lenses by, for example, including at least one dichroic coating optically in front of at least one additional mirror to separately reflect the different bands or polarizations.

A portrait lens configuration for meeting handheld device form factor constraints. First and second meniscus lenses each have a reflective surface to provide internal reflections for transmitting light toward a focal plane. A third lens is positioned between the meniscus lenses and the focal plane. The first lens includes an anterior concave surface having a reflective material extending over a portion thereof. Light received by the first meniscus lens can be transmitted therethrough. The reflective material is positioned along the anterior concave surface to receive light transmitted therethrough and reflected back from the second lens. In an associated method the first meniscus lens is positioned to receive light through a first of two opposing refractive surfaces. After each lens provides an internal reflection, reflected light is transmitted through the second of the two opposing surfaces and then through a bore positioned within the second lens to the third lens.

A finder includes, in order from an object side to an eye point side, an objective optical system that forms an intermediate image, and an ocular optical system that is provided for observation of the intermediate image. The intermediate image is positioned on the optical path between the objective optical system and the ocular optical system. The finder includes a plurality of reflecting surfaces for forming an erect image, and each of the objective optical system and the ocular optical system has at least one of the plurality of reflecting surfaces. The finder satisfies a conditional expression: 2<fo/fe<8 regarding a focal length fo of the objective optical system and a focal length fe of the ocular optical system.

A folded telescope system providing a light path to an image plane can include a first double-sided corrector plate having two powered sides, with at least one side being aspheric. In addition, the system includes a second double-sided corrector plate having two powered sides and a lens assembly positioned between the first and second double-sided corrector plates to define an image plane also positioned between the first and second double-sided corrector plates. In some embodiments a sensor is positioned at the image plane, with the folded telescope being positioned within or attachable to a display.

A Compact and Athermal VNIR/SWIR Spectrometer utilizes a slit, a Mangin lens, a pupil lens adjacent to the diffraction grating, corrector lenses, a beam splitter, field lenses and SWIR and VNIR FPAs. In examples, two corrector lenses are used. Some examples do not utilize field lenses and beam splitter, some examples utilize only the SWIR radiation spectrum. By balancing the powers of the optical elements and Abbe numbers of glasses as well as usage of aspheric surfaces combinations, a monochromatic and polychromatic aberrational correction is achieved; by balancing optical elements refractive indices change with temperature an athermalization is achieved. The overall length of the spectrometer does not exceed 4 inches, and in some examples it is 2.5 inches. A wide field of view and a low F number are obtained with an operating wavelength range from approximately 400 to 2350 nm. The spectrometer is particularly suited to airborne applications.

A Compact and Athermal VNIR/SWIR Spectrometer utilizes a slit, a Mangin lens, a pupil lens adjacent to the diffraction grating, corrector lenses, a beam splitter, field lenses and SWIR and VNIR FPAs. In examples, two corrector lenses are used. Some examples do not utilize field lenses and beam splitter, some examples utilize only the SWIR radiation spectrum. By balancing the powers of the optical elements and Abbe numbers of glasses as well as usage of aspheric surfaces combinations, a monochromatic and polychromatic aberrational correction is achieved; by balancing optical elements refractive indices change with temperature an athermalization is achieved. The overall length of the spectrometer does not exceed 4 inches, and in some examples it is 2.5 inches. A wide field of view and a low F number are obtained with an operating wavelength range from approximately 400 to 2350 nm. The spectrometer is particularly suited to airborne applications.

A multi-band/multi-polarization reflective or catadioptric optical system yields differing effective focal lengths (EFLs) per band/polarization. This approach could be used to create an imaging system, for example. In such case, a sensor (imager, spectrometer, diode, etc.) is located at the one or more focal planes. On the other hand, it could also be used to create a projecting system or hybrid projecting and imaging system by locating an emitter such as an LED, laser, etc.) at the image or focal plane. The system employs polarizers and/or dichroic coatings nano patterns to create different focal lengths and/or fields of view using the same mirrors and/or lenses by, for example, including at least one dichroic coating optically in front of at least one additional mirror to separately reflect the different bands or polarizations.