Because of the dependence of our thermal emission behaviour on the wavelength of the thermal, only a few wavelengths are suitable for thermal measurements. The following graphs show the thermal transmission range of common thermal lenses and window substances for infrared thermometers. The blue-colored curve demonstrates the general rule for all materials and represents the average value for a temperature interval of zero (black) to infinity (green) which is the cold-pressure limit (CPL).
The cold-pressure limit, which is used to determine the thickness of windows and lenses, is the maximum measured value of a material’s damping rate against the thermal gradient. This ratio is plotted as a function the temperature variation in relation to the viewing angle for a given viewing angle and cte for the window or lens. The slope of the curve is proportional to the bending angle of an entire system, which is the result when the angle of incidence shifts from linear to spherical. The focal length of the system is also an element in the slope. It can be considered as a function of the focal length divided the period of the curve (i.e. the interval between shots).
The inside temperature of the system will always remain within the prescribed curve for the given temperature and focal length of a window assembly or lens. This is also referred to as a “curved top”. The thermal conductance curve of a glass bead inside a glass vial could be plotted as a function the focal length, 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 area between the temperature of the inside surface of the system and the curve of variation for the particular window assembly must remain constant. If the aperture is variable this means that the curve could be curving as a result of the variations in the temperature of the glass used to make the bead, the temperature of the ambient atmospheric air on the inside surface of the vial and the focal length and time of shooting. A signature left by an artist on a flower is an example of a curving surface.
A window and lens should be mounted so that their focal points and lines of sight are properly aligned. If the temperature of the inside of the system is too cool for the lens, then the outside surface temperature of the frame will be cooler and the inside of the lens will be too hot. The frame will not need to be adjusted to account for internal temperature fluctuations or cooling effects. If there aren’t any temperature differences from outside, then the system’s internal temperature will be the same for a particular focal length. If the system is located in an area that has restricted or blocked views of the surrounding buildings or scenery, it may be necessary to regulate the internal temperature.
The first mechanical interlocking systems that were used to secure lenses onto cameras were constructed of plastic or other materials that could change shape or bend according to changes in mounting pressure. This design was later used to create pinhole glasses. This type of lens assembly is not without a problem: the mechanical joints between the frame and the lens could crack or indent. If this happens the result is necessary to replace the entire unit within a short amount of time. Due to this the type of system has been replaced by more robust designs.
Pinhole glasses lenses are typically made with a metal frame and a thin, plastic or glass lid. These lense designs must at a minimum have a hermetically-sealed construction. A hermetically sealed lens construction contains a sealed surface along the bottom and top of the lens assembly. The top layer could be a part of an electronic seal similar to the one described above. It could also be a source of lip, adhesive, or layer of plastic film.
A lens surface that has an adhesive and is bonded to the base is a different example of this type of window and lens assembly. This kind of system typically consists of a window casing as well as several compartments for the lens. Other types of devices could be integrated into the windows, such as thermometers and light emitters. This kind of system could also include a thermostat or light emitter that regulates the temperature of the room. In that case there are a number of compartments that could house the temperature controller along with a number of other devices, including an alarm clock or thermostat.
This is not an exhaustive list of all types of window and lens assemblies. It is however a good indication of the important technologies that are related to this invention. For more information, read the complete disclosure. Please refer to the sections on “details about the invention” and “Description Of the Process With Respect To the Identification of the various types of products That Are Involved In the Present Application.”
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