Due to the extreme dependence of our thermal emission characteristics on the wavelength of the heat source, only certain wavelength ranges are suitable for thermal measurements. The following figures show the range of thermal transmission for common windows and thermal lenses for infrared thermometers. The blue-colored curve represents 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 lenses and windows 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 plotted as a function the temperature variation along the angle of view for a specific viewing angle and the cte of the lens or window. The bending moment of a system is the change in angle of incidence from linear or spherical. This makes the slope proportional to the curve. The slope of this curve is also proportional to the focal length of the system, which is described as a function of the focal length divided by the period of the curve (i.e., the time between shots).
The inside surface temperature of the system will always remain within the prescribed curve for a given 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 beads inside a glass vial could be plotted as a function of the focal length, the temperature difference between the bottom and the vial’s surface and the angle of incidence of a particular window. If the aperture is fixed for all shots, then the area between the temperature of the inside surface of the system and the curve of variation for the particular window assembly should always remain constant. Variable apertures can cause the curve to be curvilinear due to changes in the glass’s temperature used for creating the bead as well as the ambient air temperature, focal length, and time of photography. A typical example of a curly surface can be seen in the signature of the photographer of the flower.
A window and lens must be mounted so that their focal points and lines of sight are correctly aligned. If the temperature of the inside of the system is too hot for the lens, then the outside surface temperature of the frame will be cooler and the inside temperature of the lens will be too warm. When the outside temperature of the lens and the frame are the same and the frame does not require any adjustment to compensate for the heating or cooling effects of internal temperature differences. The inside temperature of the frame will be in line for a specific focal length without the need for any other adjustments, provided that there is no external source of temperature fluctuations affects the system. However, if the camera is mounted at a location with an obstruction or restricted view of the surrounding building or scenery and the surrounding area, then internal temperatures might require adjusting.
The first mechanical interlocking system used to attach lenses to cameras were made of plastic or other materials that could bend or mold in response to changes in mounting pressure. This innovation was later adapted for use with pinhole glasses. This kind of lens assembly comes with a drawback: the mechanical joints between the lens and frame might crack or indent. If this were to happen the result will be necessary to replace the entire unit in a relatively short period of time. Because of this issue the system has been replaced by more robust designs.
Lenses that are designed to work with pinhole glasses typically come with frames made of metallic and a thin glass or plastic lid. These lense designs should at a minimum have a hermetically sealed construction. A hermetically sealed lens construction includes a sealed surface at the bottom and top of the lens assembly. The top surface may be sealed with a similar seal as the one mentioned earlier. It could also include an lip, adhesive, or layer of plastic film.
A lens surface that is the substrate and is attached to the base is another embodiment of this type window and lens assembly. This kind of system usually consists of a window casing as well as several compartments for the lens. Other kinds of devices can be used in the windows, such as light emitters and thermometers. In certain instances, the device that controls the temperature within the room might also be part of this kind of system. A series of compartments could be used to house the temperature control and a variety of other devices, such as an alarm clock, thermostat, or other devices.
This is not a full list of all the kinds of lens and window assemblies that are available. It is however a good indication of the important technologies that are related to this invention. Please read the entire disclosure for more details. In particular, you should look over the sections that pertain to “details of the present invention” and “Description of the Process with Respect to the Identification of the Different Classes of Products That Are involved in the Present Application.”
know more about Sapphire cowling here.