Due to the extreme dependence of our thermal emission characteristics on the wavelength of the heat source that we have, only certain wavelengths are suitable for thermal measurements. The following diagrams illustrate the range of thermal transmission of standard thermal lenses and window materials for infrared thermometers. The blue-colored curve reflects the general rule that applies to all materials. It is the average of the temperature range from zero (black) to infinity (green) and that is the cold pressure limit (CPL).
The cold-pressure limit, which is used for windows and lenses is the highest recorded value of a material’s damping coefficient against the thermal gradient. This ratio is plotted as a function the temperature variation across the angle of view for a specific viewing angle and the cte of the lens or window. The slope of the curve is proportional to the bending force of an entire system, which is the result when the angle of incidence shifts 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 the period of the curve (i.e. the duration between shots).
For a particular 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 the perfect order called a “curved surface.” For instance the curve for the thermal conductivity of a glass beads inside a glass vial having a hole in it can be plotted in relation to the focal length, the temperature difference inside the vial between the bottom of the bead and the vial’s surface, 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 will remain the same. Variable apertures can cause the curve to be curvilinear due to changes in the temperature of the glass used for creating the bead, ambient air temperature, focal length, and time of photography. A signature left by photographer on flowers is an example of a curly surface.
A lens and window must be mounted so that their focal points and lines of sight are properly aligned. If the surface temperature of a system is too cold for the lens, the exterior temperature of the frame as well as the interior temperature will be too high. When the outside temperature of the lens and the frame are the same and the frame does not require any adjustment to counteract the heating or cooling effects of internal temperature variations. If there are no temperature variations from outside, the frame’s inside temperature will be the same for the given focal length. If the system is situated in an area that has restricted or unobstructed views of the surrounding scenery or buildings it could be necessary to control internal temperatures.
The first mechanical interlocking system used to attach lenses to cameras were made of plastic. This design was later adapted for use with pinhole glasses. This type of lens assembly comes with a drawback that the mechanical joints between the frame and lens could crack or indent. If this were to happen the result will be necessary to replace the entire assembly within a short amount of time. This is why this system has been replaced with more durable designs.
Pinhole glasses lenses are generally constructed using a frame of metal and a thin, plastic or glass lid. These lense designs should at a minimum, have a hermetically sealed construction. A hermetically sealed lens has a sealed surface on the bottom and at the top. The top surface could have a similar seal to the one described above. It could also be a source of lip, adhesive, or layer of plastic film.
A lens surface that contains the substrate and is attached to the base is an additional example of this type of lens and window assembly. This type of system is typically comprised of a casing for windows and a series of lens compartments. The windows could also include other types of devices, like light emitters, or thermometers. In some cases, the device that controls the temperature in the room could also be part of this type of system. In this case, a series of compartments could house the temperature control together with a variety of other devices, including an alarm thermostat or clock.
This is not an exhaustive list of all kinds of window and lens assemblies. It’s an indication of the significant technologies that are connected to this invention. For more information, please see the entire disclosure. Please refer to the sections relating to “details regarding the present invention” and “Description Of the Process With Respect To the Identification of the various classes of products That Are Involved In the Present Application.”
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