Recent content by Gleb1964

Planck’s radiation law applies to an ideal Black Body, where electromagnetic waves are absorbed and re-emitted multiple times within the material. This requires that the mean free path of the radiation is much shorter than the size of the volume, ensuring thermal equilibrium. If this condition...

There are standard optical components used for generating lines from laser beams, known as Powell lenses. These lenses are manufactured with various divergence angles. A typical laser beam has a Gaussian intensity profile. The principle behind a Powell lens is that it splits the laser beam...

It’s not the volume itself that matters, but the relationship between the volume size and the photon’s mean free path. That’s what I’m referring to. If radiation passes through a small volume with low absorption, the emissivity of that volume will be proportionally low.

What do you think the emissivity coefficient would be if the mean free path of photons (e.g., gamma photons) is much greater than the size of the volume? The emissivity would be about zero. For a black body, the mean free path of photons needs to be much smaller than the volume size, as in the...

The absolute values of irradiance on your graph is applicable only to a enough large volume of plasma which absorb as a Black Body. Small volume would be transparent and have much much less emissivity.

For example, FLIR: Infrared Camera Accuracy and Uncertainty in Plain Language Infrared cameras are typically calibrated using multiple blackbody sources at different temperatures. The camera is mounted on a rotating platform and sequentially pointed at these reference sources.

It's quite simple: if the source's angular size is below the resolution limit, it becomes diluted into the point spread function. If the object's angular size is unknown, its temperature cannot be determined.

It is impossible to use Stefan's law for unresolved source.

In Köhler-type illumination Stop and Field apertures are exchanging between each other between two options, when taking light source or film as an object. The image also different for those two cases. Non-sequential mode is free of that "stop" and "field" conditions, but sequential mode is more...

Lens magnification depends on the distance to your eye, viewing though the lens. If lens (thin lens) coincide with eye, its angular magnification is 1x. If you increase distance between lens and eye, the angular magnification would increase until infinity when eye coincide with the point of...

May be this picture helps. Think about Lens 2 as a microscope looking at DMD pixels. Its resolution would be defined by the numerical aperture of Lens 2 in the object space (at DMD object), meaning how width angle of diffracted from DMD object would be accepted by lens 2 and consecutive optics...

Not correct. Diffraction limitation of the illumination beam is not connected to the DMD pixel size and it resolution. The size of illumination beam is only defining the size of illuminated area at DMD. The resolution of the DMD projection is defined by the size of field aperture located at...

Apart from cloud reflectance, there is a significant path within the atmosphere where water vapor efficiently absorbs signals at 940 nm.

Isn't 940nm close to the water absorption peak?

Only one point (or line) of detector would fulfil null, but not the other area of extended detector.