Due to the high dependence of our thermal emission characteristics on the thermal wavelength that we have, only certain wavelengths are suitable for thermal measurements. The following graphs show the range of thermal transmission of the most common thermal lenses as well as window substances for infrared thermometers. The blue-colored curve reflects the general rule that applies to all materials. It is the average value across the temperature range of zero (black), infinity (green) and is the cold-pressure limit (CPL).
For lenses and windows, the cold-pressure limit is defined as the highest value of the damping ratio of a material against the thermal gradient. This ratio is plotted as a function the temperature variation across the viewing angle for a given viewing angle and the cte of the window or lens. The slope of this curve is proportional to the bending force of a system, which occurs when the angle of incidence changes from spherical to linear. The focal length of a system is also an important factor in the slope. This can be considered as a function the focal length divided by the period of the curve (i.e. the interval between shots).
The inside surface temperature of the system will be within the prescribed curve for a 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 bead inside a glass vial could be plotted as a function the focal length as well as 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 inside surface temperature of the system and the curve of variation for that particular window assembly must remain constant. Variable apertures can cause the curve to be curvilinear due to variations in the temperature of the glass used for creating the bead as well as the ambient air temperature, length of the lens, and time of photography. An example of a curved surface can be seen in the signature of the photographer of flowers.
A lens and window must be mounted in a manner that their focal points and lines of sight are correctly aligned. If the inside surface temperature of the system is too cool for the lens, then the outside surface temperature of the frame will be lower and the inside of the lens will be too warm. The frame will not need to be adjusted in order to compensate for internal temperature variations or cooling effects. If there aren’t any temperature differences from outside, the system’s inside temperature will be the same for the given focal length. If the system is situated in an area with restricted or unobstructed views of the surrounding scenery or buildings, it may be necessary to control the internal temperature.
The first mechanical interlocking system used to mount lenses to cameras were constructed of plastic or other materials that would change shape or bend in response to changes in mounting pressure. This design was later used to create pinhole glasses. This kind of lens assembly is not without a problem that the mechanical joints between the frame and lens could break or become indented. If this were to happen, happening, it would be essential for the entire system to be replaced within a short time. This is the reason why this system has been replaced with more durable models.
Pinhole glasses lenses are generally constructed with a frame made of metal and a thin, glass or plastic lid. These lense designs should at a minimum have a hermetically sealed construction. A hermetically sealed lens has a sealed surface at the bottom and top. The top surface may contain a mechanical seal similar to that described above. It could also include an adhesive, lip, or layer of plastic film.
Another embodiment of this type of lens and window assembly is a lens surface that contains an adhesive that adheres to the base of the window assembly. This kind of system usually consists of a window casing and a series of compartments for lenses. The windows may also contain different kinds of devices such as light emitters or thermometers. This type of system could also include a thermostat or light emitter that controls the temperature in the room. In that case the system would comprise of compartments that could house the temperature control together with a variety of other devices, including an alarm thermostat or clock.
This isn’t a complete listing of all the types of lens and window assemblies that are available. It’s an indication of the significant technologies that are connected to this invention. Please refer to the entire disclosure for more information. Particularly, you should take a look at the sections relating to “details of the present invention” and “Description of the Process With Respect to the Identification of the Various classes of products involved in the Present Application.”
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