component of optical instrument

Component of Optical Instrument

Bivek TimalsinaLecturer, Nobel Collegebivektim@gmail.com

Component of Optical Instrument

monochromatorsample cell

detector

light source

slit

diff

ract

ion

grat

ing

optical system

Component of Optical Instrument

Component of Optical Instrument

Basic components

provides the light to be passed through the sample.

1. Light Sources

a source must generate a beam of radiation that is sufficiently powerful for easy detection and measurement.

- Hydrogen discharge: ultraviolet Light.

- Hollow Cathode Lamps (HCL) - tungsten Lamp: visible light .

its output power should be stable for reasonable periods.

Basic components

Used to select a given wavelength of the light from the light source

2. Wavelength selection (Monochromator)

Mono = single Choroma = colorThere exists many techniques• Prisms• Filter• Diffraction gratings • Stray light• Wavelength range• Double monochromator`

Basic components

Used to select a given wavelength of the light from the light source

2. Wavelength selection (Monochromator)

Mono = single Choroma = colorThere exists many techniques• Prisms• Filter• Diffraction gratings • Stray light• Wavelength range• Double monochromator`

Polychromatic Radiation

Narrow Band of Radiation

Glass Plate

Metallic Film

Dielectric Material

Basic components1. MonochromatorDiffraction gratings

To obtain a specific wavelength

1. entrance slit.2. concave mirror or lens.3. a prism or grating.4. focal plane.5. exit slit.

Exit SlitEntrance Slit

Grating

FocalPlane

Basic components

A container that contains a sample is usually called "cell“

has fixed length & volume. usually round or square cuvette. made of material that does not absorb light in the wavelength range.Two types are available:- - Glass – visible region. - Quartz – ultraviolet.

3. Sample cell

Basic components

to convert the radiant energy to a measurable signal; and to a readout device

“Detector” is a device that indicates the existence of some physical phenomenon.

The term transducer is used to indicate the device that converts quantities, such as light intensity, into such electrical signals that can be subsequently amplified, manipulated, and finally converted into numbers.

4. Transducer and Detector

Basic components

Ideal detector : high sensitivity. high signal/noise. fast response time. constant response for λs. responds to low levels of energy.

4. Transducer and Detector

General design

An Absorption Instrumental Setup

An Emission or fluorescence or Scattering Instrumental Setup

An Emission Instrumental SetupWith thermal energy as source

ANY QUESTIONS ?