Due to the dependence of our thermal emission behavior upon the thermal wavelength, only a few wavelength ranges are suitable for measurements of thermal. The following diagrams illustrate the thermal transmission range of the most common thermal lenses as well as window materials for infrared thermometers. The blue-colored curve demonstrates the general rule for all materials, and represents the average value across an interval of temperature from zero (black) to infinity (green) which is the cold-pressure limit (CPL).
For windows and lenses, the cold-pressure limit is defined as the highest value of the damping ratio of a substance against the thermal gradient. This ratio is calculated as a function of the temperature difference along the angle of view for given viewing angles and cte of a window or lens. The slope of the curve is proportional to the bending angle of a system, which occurs when the angle of incidence shifts from spherical to linear. The slope of this curve is also proportional to the focal length of the system, which is considered as a function of the focal length divided by the duration of the curve (i.e. the interval between shots).
The temperature of the inside of the system will be within the prescribed curve for the given temperature and the focal length of a window assembly or lens. This is also referred to as a “curved top”. The thermal conductance curve of a glass beads within a glass vial can be plotted in relation to the focal length, the temperature difference between the bottom and the surface of the vial and the angle of incidence of a specific window. If the aperture is fixed for all shots then the area between the system’s surface temperature and the curve of variation will remain constant. Variable apertures can cause the curve to be curvilinear due to changes in the temperature of glass used to create the bead, ambient air temperature, the focal length, and the time of photography. A signature left by photographer on flowers is an example of a curved surface.
A window and lens must be mounted in a way that their focal points and lines of sight are correctly aligned. If the internal temperature of the system is too cold for the lens, then the outside surface temperature of the frame will be lower and the inside of the lens will be too warm. If the outside temperature of the lens and the frame are the same and the frame does not require any adjustments to compensate for the effects of heating or cooling of internal temperature variations. If there are no temperature variations from outside, the system’s internal temperature will be the same for a particular focal length. If the system is located in an area with limited or obstructed views of surrounding structures or landscape, it may be necessary to regulate the internal temperature.
The first mechanical interlocking system used to secure lenses onto cameras were made of plastic or other materials that could bend or mold according to changes in mounting pressure. This design was later adapted for use with pinhole glasses. This type of lens assembly has a problem that the mechanical joints between the frame and lens could break or become indented. If this happened then it will be necessary to replace the entire system in a relatively short period of time. Because of this issue, this type of system has been replaced with more robust designs.
Pinhole glasses lenses are typically made with a metal frame and a thin, glass or plastic lid. At the very least the lense designs must include a hermetically sealed lens construction. A hermetically sealed lens has a sealed surface at the bottom and the top. The top surface may contain a mechanical seal that is similar to that previously mentioned. It could also be a source of adhesive, lip or a layer of plastic film.
Another variation of lens and window assembly includes a lens surface that contains an adhesive that adheres to the base of the window assembly. The system typically consists of a glass casing and a series of lens compartments. Other kinds of devices can be used in the windows, for example, thermometers and light emitters. In some instances, the device used to control the temperature of the room might also be part of this type of system. A number of compartments could be used to house the temperature control and a variety of other devices like an alarm clock, thermostat, or other devices.
This is not a full list of all the kinds of window assemblies and lenses that are available. It’s a good indication of the most important technologies that are related to this invention. For more details, please read the entire disclosure. Please refer to the sections that pertain to “details about the invention” and “Description of the Method with Respect To the Identification of the Different Classes of Products that are involved in the Present Application.”
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