AKASH SINGH EC 4 th YEAR LENS A lens may be defined as a piece of - - PowerPoint PPT Presentation

AKASH SINGH EC 4th YEAR

LENS

A lens may be defined as a piece of glass,

plastic or any other transparent material which is curved on one or both sides and which makes a beam of light passing through it –bend, spread out, become narrower or change direction.

ZOOMING AND FOCUSING

Zooming is a phenomenon exhibited by a

photographic lens by virtue of which a lens can move in from a distant to a close view while keeping what is being photographed in focus .

It is a method of adjusting the focal length

i.e. the distance between the middle of the lens and the focus such that the image becomes more clear.

THE SIMPLEST DEFINITION OF A LIQUID LENS

We've all been drinking a cold soda when the

condensation on the side drips off. You may notice that whatever is under the water drop is magnified. That's a simple version of a liquid lens.

LIQUID LENS THAT IS USED IN VARIOUS ELECTRONIC DEVICES

A liquid lens is a lens that uses the

properties of two different liquids within a small space to provide magnification.

Water and oil do not mix, and are both

safe and inexpensive, so they are perfect for use in a liquid lens.

The mixture of water and oil is sandwiched

between two pieces of clear glass or

• plastic. In this way, a light, cheap liquid

lens is created.

CONTD…

Because water adheres to glass or plastic,

it naturally forms a bubble shape

This bubble shape within the liquid lens

creates magnification and variable focus.

The oil component of the liquid lens fills in

the rest of the space to keep the water from sloshing around.

ELECTROWETTING

• Water is a polar liquid. Thus its molecules can

be attracted by an electric field. It is thus possible to change the shape of the liquid drop.

• To carry out this process of electrowetting a

water drop is deposited on a substrate made

• f metal, covered by a thin insulating layer.

The voltage applied to the substrate modifies the contact angle of the liquid drop. The liquid lens uses two isodensity liquids, one is an insulator while the other is a conductor. The variation of voltage leads to a change of curvature of the liquid-liquid interface, which in turn leads to a change of the focal length of the lens.

DETAILED DESCRIPTION (CONSTRUCTIONAL Detail)

To start with we take a glass tube which is

coated with INDIUM TIN OXIDE (ITO). This is 50nm thin and acts as an electrode.

Then we apply another coating of

PARYLENE_NITROGEN which acts as an insulator between the electrode and water and this is 3µm thick.

To force the water volume into a convex

shape, we apply a top coat of a water- repelling FLUOROPOLYMER.

CONTD…

We fill the tube with an insulator—a

mixture of PHENYL METHYL SILOXANES that has the same density as water in

• rder to make the curvature of the

interface between the liquids perfectly spherical .

When a voltage is applied between the

water and the wall electrode, the polar water molecules are attracted toward the

• wall. The volume of the liquids is constant,

so the curvature of their interface will

• change. If the liquids have different

refractive indices, their interface acts as a variable-focus lens .

Why water?

Water reduces the cost of manufacturing

drastically.

Water cannot be scratched and thus gives us

a flawless lens.

Water is more transparent to light than any

• ther transparent material.

Water is a polar solvent and hence it is

subjected to electrowetting.

CONTD…

A drop of water has a high

surface tension and has a natural curvature similar to that of a conventional lens.

Hence the lens obtained is a

defect free lens.

Applications

It has got an extensive use in cellular

phones these days. It actually gives rise to a small system which can easily be embedded in a small device like that of a cellular phone.

It is used in various electronics sets which

integrate optics with them. For e.g. displays,cameras,computers.

CONTD…

It is used in endoscope (in the

field of medicines) which is developed on a number of optical functions.

These days it is also used in

tumor detection.

ADVANTAGES

 A liquid lens has got a large focal length

range.

One of its most important properties is its

ruggedness i.e. it has got no moving parts.

There is no problem of wear and tear as

the lens does not have to change position.

The time taken by it to respond is very

• less. It has got a speedy response of

2/100th of a second.

It has got a very good transparency in

visible range.

CONTD…

It has got a wide operating temperature

range i.e. -50°c to 180°c .

The cost of manufacturing is very less. It is very compact in size i.e. 10µm to 10mm. The curvature and the focal length of the

liquid lens can be switched from concave to convex.

CONTD…

Zoom lens can be created by combining two

liquid lenses.

Greatly reduces space taken up by

conventional focus / zoom lens systems.

Minimal power usage . The energy to drive

the liquid lens is generated by charging the capacitor formed by the wall electrode and the water. Charging this approximately 100-pF capacitor requires less than a micro joule .

Physical Dimensions

Diameter of lens: 10µm-

10mm

 Thickness of lens or

enclosure: less than 1mm to 2mm.

Electrical Specifications

Operating voltage

(autofocus): 1.5V

 Power not required in

manual focusing mode.

Optical Specifications

Magnification: 10x  Focusing latency: 2 mm

– infinity

DISADVANTAGES

The only disadvantage of

the liquid lens is the fact that it should not be subjected to temperature beyond the specified range

• r else water will freeze

inside it and this may damage our system.

Proposed remedies

The freezing point of the

liquid can be improved by adding large quantities of salt (e.g., lithium chloride)

• r antifreeze (e.g.,

ethylene glycol).