Eye peice

               DefinationA arrangement of two lenses which are placed at fixed distance and Aberration in the system will minimum the arrangement is called eyepeice.

There are two type of eye peice

1)Huggen's eyepeice

2)Ramsten's eyepeice

1)Huggen's eye peice

Construction

In this eye peice we use to Plano convex lens the ratio of focal length for both lens is 3:1. the plane surface of both lens is towards to eye.Both lenses separated by a distance 2f.the lens which near to eye is called eye lens  and focal length is f.The lens which is side of object is called field lens and focal length 3f.

[2]Minimum condition for chromatic aberration 
d=(f1+f2)/2d

d=(3f+f)/2d

d=2f

The image of this eyepeice is free to chromatic aberration

[3]Minimum condition for Spherical aberration

d=f1-f2

d=3f-f

d=2f
Eye peice satisfied Minimum condition of a Spherical aberration thatmeans it's free  from Spherical aberration.

[4]Equivalent focal length of eye peice

1/F=1/F1+1/F2-d/F1F2

1/F=1/3F+1/F-2F/3F.F

1/F=(1+3-2)/3F

1/F=2/3F

F=3F/2

 The equivalent focal length of eye peice is from right side of eye peice. 

[5]First principle point  

Alpha=FD/F2

Alpha=(3F/2.2F)/F

Alpha=3F

The first principle point is present right side of the field lens.

[6]Second principle. Point.

Beta=-Fd/F1.             

 Beta=-(3f/2.2f)/3f

Beta=-f

Second principle point is present left hand side of eye lens.
Above word expression

x=focal length of equivalent lens

D=distance between lenses

F1=focal length of eye lens

,F2=focal length of field lens