Due to the extreme dependence of our thermal emission characteristics on the thermal wavelength that we have, only certain wavelengths are suitable for measurements of thermal. The following figures reveal the range of thermal transmission of the most common thermal lenses as well as window substances for infrared thermometers. The blue-colored curve shows the general rule for all materials and shows the average value across a temperature interval of 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 measured value of the damping ratio of a material against the thermal gradient. This ratio is calculated as a function the temperature difference across a viewing angle for a given viewing angle and cte of a lens or window. The slope of this curve is proportional to the bending force of an entire system, which is the result when the angle of incidence changes from spherical to linear. The focal length of an entire system is also a factor in the slope. It can be thought of as a function of the focal length divided by the period of the curve (i.e. the interval between shots).
For a given set of temperatures and a certain focal length of a lens or window assembly, the inside surface temperature of the system will always be within the prescribed curve , in a perfect regularity known as a “curved surface.” For instance the curve of thermal conductivity of a glass beads inside a glass vial with a hole in it can be plotted in relation to the focal length and the temperature difference inside the vial between the bottom of the bead and the surface of the vial, and the angle of incidence for a specific window assembly. If the aperture is fixed for all shots, then the area between the system’s surface temperature and the curve of variation should remain constant. Variable apertures can cause the curve to become curvilinear due to changes in the temperature of glass used for creating the bead, ambient air temperature, the focal length, and the time of photography. A signature left by photographer on the petals of a flower is an example of a curly surface.
The process of mounting a lens and window should be done in a way that their focal points, and lines of sight, are in the correct direction. If the interior surface temperature of the system is too cold for the lens, then the outside temperature of the frame as well as the interior temperature will be too high. The frame will not have to be adjusted to compensate for internal temperature fluctuations or cooling effects. The inside temperature of the system will be appropriate for a given focus length without the need for any other adjustments, as long as there is no external source of temperature fluctuations affects the system. If the system is situated in an area with limited or obstructed views of the surrounding scenery or buildings it might be necessary to control the internal temperature.
The first mechanical interlocking systems used to mount lenses to cameras were constructed 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 comes with a drawback: the mechanical joints between the frame and the lens could crack or indent. If this happened, then it is required to replace the entire system within a short amount of time. This is why this system is being replaced with more durable designs.
Pinhole glasses lenses are usually constructed using a frame of metal and a thin, glass or plastic lid. At the very least the lense designs must be sealed with a hermetically-sealed lens construction. A hermetically sealed lens has an enclosed surface at the bottom and the top. The top surface may contain a mechanical seal similar to the one previously mentioned. Alternatively, it could also contain some other substance, for instance, an adhesive, a lip or a layer of plastic film.
Another variation of lens and window assembly includes the lens surface, which is a substrate, which adheres to the base of the window assembly. This type of system typically consists of a window casing as well as several compartments for lenses. Other kinds of devices can be integrated into the windows, for example, light emitters and thermometers. In certain instances, the device that controls the temperature of the room could also be part of this type of system. In that case there are a number of compartments that could house the temperature controller together with a variety of other devices, like an alarm thermostat or clock.
This is not a full list of all kinds of window and lens assemblies that are available. It’s a good indication of the most important technologies that are related to this invention. Please refer to the complete disclosure for more details. Refer to the sections relating to “details about the invention” and “Description of the process with Regard to the Identification of the various classes of products which are involved in the Present Application.”
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