Due to the high dependence of our thermal emission behavior on the wavelength of the heat source due to the extreme dependence of our thermal emission behavior on the wavelength, only certain wavelengths are effective for thermal measurements. The following diagrams illustrate the thermal transmission range of the most common thermal lenses as well as window substances for infrared thermometers. The blue-colored curve is the general rule for all materials. It is the average value across the temperature range of zero (black) to infinity (green) and that is the cold pressure limit (CPL).
For windows and lenses The cold-pressure limit can be defined as the maximum measured 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 angle and the cte of a lens or window. 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 the focal length divided by the period of the curve (i.e. the duration between shots).
The inside surface temperature of the system will be within the prescribed curve for a particular temperature and the focal length of the window assembly or lens. This is also known as a “curved top”. The thermal conductance curve of a glass bead inside a glass vial may be plotted as a function the focal length and 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 must remain constant. If the aperture is adjustable this means that the curve could be curved as a result of the variation in the temperature of the glass used to make the bead and the temperature of the ambient air that is circulating on the inner surface of the vial, and the focal length and duration of shooting. An example of a curved surface can be seen in the signature left by the photographer of flowers.
The mounting of a window and lens must be done to ensure that their focal points, and lines of sight, are in the correct direction. If the surface temperature of a system is too cold for the lens, then the outside temperature of the frame and the interior temperature will be too high. The frame will not have to be adjusted to account for internal temperature fluctuations or cooling effects. If there aren’t any temperature variations from outside, the frame’s internal temperature will be the same for a given focal length. However, if the system is located in a place where it has an obstructed or limited view of any surrounding building or scenery the internal temperature may need to be controlled.
The first mechanical interlocking system that was used to mount lenses to camera were made of plastic. This design was later used for pinhole glasses. One issue with this type of lens assembly is that the mechanical joints between the frame and lens might indent or even fracture. If this happens the result will be necessary to replace the entire system in a relatively short period of time. This is the reason why this system has been replaced with more robust designs.
Lenses designed to work with pinhole glasses typically come with frames made of metallic and a thin glass or plastic lid. These lense designs must at a minimum, have a hermetically sealed construction. A hermetically sealed lens construction has a sealed surface on the bottom and top of the lens assembly. The top surface may be sealed with a similar seal to the one mentioned earlier. It could also contain an lip, adhesive or a layer of plastic film.
A lens surface that is an adhesive and is bonded to the base is a different example of this type of window and lens assembly. This type of system is typically comprised of a casing for windows and a series of lens compartments. Other types of devices could be used in the windows, like thermometers and light emitters. In some cases, the device used to control the temperature within the room might also be part of this kind of system. In this case there are a number of compartments that could house the temperature control as well as a range of other devices, including an alarm clock or thermostat.
This isn’t a complete list of all the kinds of window assemblies and lenses that are available. It is indicative of the most important technologies that are related to this invention. Please read the entire disclosure for more details. In particular, you should read the portions relating to “details of the Present Invention” and “Description of the Process with Respect to the Identification of the Different types of products involved in the Present Application.”
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