Because of the dependence of our thermal emission characteristics on the wavelength of the thermal due to the dependence of our thermal emission behavior on the wavelength, only a few wavelengths are suitable for thermal measurements. The following diagrams illustrate the range of thermal transmission of common thermal lenses and window materials for infrared thermometers. The blue-colored curve reflects the general rule that applies to all materials. It is the average of the temperature range from zero (black) to infinity (green) and that is the cold-pressure limit (CPL).
The cold-pressure limit, which is used for lenses and windows is the highest recorded value of a material’s damping rate against the thermal gradient. This ratio is calculated as a function of the temperature difference in relation to the viewing angle for a given viewing angle and the cte of the window or lens. The bending moment of a system is the variation in angle of incidence from linear or spherical. This causes the slope to be proportional to this curve. The slope of this curve is also proportional to the focal length of the system, which can be considered as an expression of the focal length divided by the length of the curve (i.e. the interval between shots).
For a particular set of temperatures and a given focal length of a window or lens assembly, the internal surface temperature of the system will always fall within the prescribed curve in the perfect order called a “curved surface.” The thermal conductance curve of a glass bead inside a glass vial could be plotted as a function the focal length and the temperature difference between the bottom of the vial and its surface and the angle of incidence of a specific window. If the aperture is fixed for all shots, then the space between the inside surface temperature of the system and the curve of variation for that particular window assembly should always remain the same. If the aperture is variable, then the curve may be curved as a result of the variation in the temperature of the glass used in the making of the bead as well as the temperature of the ambient atmospheric air on the inside of the vial’s surface, and the focal length and time of shooting. A signature left by photographer on a flower is an example of a curving surface.
A lens and window must be mounted in a manner that their focal points and lines of sight are properly aligned. If the interior surface temperature of an object is too cold for the lens, the outside temperature of the frame as well as the interior temperature will be too high. If the temperature outside of the lens and the frame are equally, then the frame will not require any adjustment to compensate for the heating or cooling effects of internal temperature variations. If there aren’t any temperature variations from outside, the system’s internal temperature will be the same for the given focal length. However, if the camera is mounted at a location where it has an obstructed or restricted view of the nearby building or scenery the internal temperature may need to be controlled.
The first mechanical interlocking system used to secure lenses onto cameras were made of plastic or other materials that would bend or mold in response to changes in mounting pressure. This technology was later adopted for use with pinhole glasses. This kind of lens assembly has a problem with the mechanical joints that connect the frame and lens could break or be indented. If this were to happen then it is required to replace the entire unit in a relatively short period of time. Because of this issue the system has been replaced by more robust designs.
Pinhole glasses lenses are generally made with a metal frame and a thin, glass or plastic lid. These lense designs must at a minimum have a hermetically sealed construction. A lens that is hermetically sealed has an enclosed surface at the bottom and at the top. The top layer could be a part of an elastomeric seal similar to that previously mentioned. It could also contain an lip, adhesive, or layer of plastic film.
Another variant of lens and window assembly includes a lens surface that contains a substratethat is attached to the base of the window assembly. This type of system typically comprises glass casings and series of lens compartments. Other types of devices could be used in the windows, like thermometers and light emitters. This type of system could also include a thermostat or light emitter that controls the temperature in the room. A number of compartments could be used to house the temperature controller and a variety of other devices, such as an alarm clock, thermostat, or other devices.
This is not an exhaustive list of all the types of lens and window assemblies. It’s a good indication of the important technologies related to this invention. For more information, see the entire disclosure. Please refer to the sections that pertain to “details about the present invention” and “Description Of the Process With Respect To the Identification of the Different Classes of Products which are involved in the Present Application.”
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