Difference between filter and monochrmator in instumentation
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Monochromators

Figure 1. Block diagram of monochromator
Monochromators (Figure 1) include two slits - an entrance slit and an exit slit - via which light enters and exits the device with a dispersing unit, either grating and mirrors or a prism to manipulate the light as it enters and leaves the grating prism.
The spectral quality of light produced by a monochromator is a property of the dispersive capability and the width of the slits of the grating or prism. A double grating is utilized for applications that demand the highest levels of performance, whereby the light from the first grating is passed via a second grating. This reduces scatter and gives greater resolution.
However, when the incident light impinges on each optical unit it leads to a loss of energy. Hence, there is a trade-off between the intensity of the emitted light and the wavelength resolution.
Interference Filters
Interference filters contain several optical layers deposited on a glass substrate or transparent quartz. The specific performance characteristics of the filter are determined by the thickness of the optical layers.
Interference filters are relatively lighter and smaller than monochromators, and also provide technological advantages - when an interference filter is properly designed, it can collect several hundred or several thousand times the quantity of light collected by a monochromator of the same bandwidth.
Interference filters can be custom-designed to meet the specific needs of spectroscopists. For instance, Linear Variable Filters, in which the wavelength of light reflected and transmitted from the optical layers changes linearly as it passes along the filter’s length. This is often called scanning, and is accomplished by depositing the optical layers as a wedge

Figure 1. Block diagram of monochromator
Monochromators (Figure 1) include two slits - an entrance slit and an exit slit - via which light enters and exits the device with a dispersing unit, either grating and mirrors or a prism to manipulate the light as it enters and leaves the grating prism.
The spectral quality of light produced by a monochromator is a property of the dispersive capability and the width of the slits of the grating or prism. A double grating is utilized for applications that demand the highest levels of performance, whereby the light from the first grating is passed via a second grating. This reduces scatter and gives greater resolution.
However, when the incident light impinges on each optical unit it leads to a loss of energy. Hence, there is a trade-off between the intensity of the emitted light and the wavelength resolution.
Interference Filters
Interference filters contain several optical layers deposited on a glass substrate or transparent quartz. The specific performance characteristics of the filter are determined by the thickness of the optical layers.
Interference filters are relatively lighter and smaller than monochromators, and also provide technological advantages - when an interference filter is properly designed, it can collect several hundred or several thousand times the quantity of light collected by a monochromator of the same bandwidth.
Interference filters can be custom-designed to meet the specific needs of spectroscopists. For instance, Linear Variable Filters, in which the wavelength of light reflected and transmitted from the optical layers changes linearly as it passes along the filter’s length. This is often called scanning, and is accomplished by depositing the optical layers as a wedge
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