Due to the high dependence of our thermal emission characteristics on the wavelength of the thermal radiation that we have, only certain wavelengths are effective for thermal measurements. The following diagrams illustrate the ranges of thermal transmission of common window and thermal lenses for infrared thermometers. The blue-colored curve demonstrates the general rule applicable to all materials and shows the average value across a temperature interval of zero (black) to infinity (green) which is the cold-pressure limitation (CPL).
For lenses and windows The cold-pressure limit can be defined as the maximum measured value of the damping ratio of a material in relation to the thermal gradient. This ratio is calculated as a function the temperature difference across a viewing angle for a given viewing angle and the cte of a lens or window. The bending moment of a system is the variation in angle of incidence from spherical or linear. This causes the slope to be proportional to this curve. The focal length of an entire system is also a 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 temperature of the inside of the system will be within the prescribed curve for the given temperature and focal length of a window assembly or lens. This is also known as a “curved top”. The thermal conductance curve of a glass beads inside a glass vial may 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 given window. If the aperture is fixed for all shots, then the distance between the temperature of the inside surface of the system and the curve of variation for the particular window assembly must remain the same. If the aperture is variable, then the curve may be curved as a result of the fluctuation in the temperature of the glass used to make the bead, the temperature of the ambient air that is on the inside surface of the vial and the focal length as well as the duration of shooting. An example of a curved surface can be seen in the signature left by the photographer of a flower.
A window and lens must be mounted in a way that their focal points and lines of sight are properly aligned. If the surface temperature of the system is too cold for the lens, the outside temperature of the frame and its interior temperature will be too high. The frame won’t need to be adjusted to account for internal temperature variations or cooling effects. The internal temperature of the system will be appropriate for a particular focal length without the need for any other adjustments, provided no external source of temperature variations impacts the system. If the system is located in an area that has 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 made of plastic or other materials that could 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 comes with a drawback with the mechanical joints that connect the lens and frame might crack or indent. If this were to happen, happening, it would be necessary for the entire assembly to be replaced in a short time. This is the reason this system is being replaced with more robust designs.
Pinhole glasses lenses are typically constructed with a frame made of metal and a thin, glass or plastic lid. At the very least, these lense designs should be sealed with a hermetically-sealed lens construction. A hermetically sealed lens construction contains a sealed surface along the bottom and top of the lens assembly. The top surface may contain an elastomeric seal similar to the one described above. Additionally, it could contain some other substance, like an adhesive, lip, or a layer of plastic film.
A lens surface that contains the substrate and is attached to the base is another example of this type of lens and window assembly. This type of system is typically comprised of a casing for windows and several compartments for lenses. The windows could also include other kinds of devices, like light emitters, or thermometers. In certain instances, the device used to control the temperature within the room could be part of this kind of system. In that case, a series of compartments could house the temperature control as well as a range of other devices, such as an alarm clock or thermostat.
This is not a full list of all kinds of lens and window assemblies that are available. It is however a good indication of the important technologies associated with this invention. For more details, please see the complete disclosure. In particular, please read the portions relating to “details of the present invention” and “Description of the Method with Regard to the Identification of the Various classes of products Included in the Present Applica.”
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