Radiometry is the science of the measurement of electromagnetic (EM) radiation. The broader spectrum covered by the science of radiometry is based on physical constants.
The properties of concern to us here are radiated power and its spatial and angular distributions. The four basic concepts are:
- Radiant Flux
- Radiant Intensity
- Radiance
- Irradiance
Photometry is defined as the measurement of electromagnetic energy that is visible to the human eye.
In 1942 the Commission Internationale de l’Eclairage (CIE) convened to define the response of the average human eye. They defined the Standard Luminosity Function also known as the Photopic curve and the Scotopic curve.
Photometric quantities are derived from radiometric quantities by utilizing a filter which approximates the behavior of the average human eye as defined by the CIE.
A radiometer is a device that measures the intensity of radiant energy. A majority of radiometers utilize only a single sensor whether photocell, photo-multiplier tube (PMT), etc. An optical filter is normally used when measuring radiation emitted from a specific spectrum or to incorporate the radiometer within a certain spectral response.
Radiometers are commonly used to quantify light or energy outside the visible spectrum, i.e., ultraviolet and infrared. Depending on the specific application, different filters with specific spectral responses are used.
A photometer is defined as an instrument for the measurement of visible light. The most common types are the luminance and illuminance meters.
The basic difference between photometers and radiometers is that the photometer incorporates a filter which follows the CIE Standard Luminosity Function Vλ curve (shown below).
Konica Minolta Sensing Inc published a booklet - The Language of Light which helps make the complicated lighting terminology simple for applicators.
Write to me if you need a copy.
Posts
No comments:
Post a Comment