应用光学chapter 5

P” ( virtual image )
Exit pupil
In image space the aperture stop and lens is replaced by the exit pupil.
Entrance Pupil
conjugate The whole system
Exit Pupil
The chief ray passes through the center of the aperture stop, entrance pupil, exit pupil
Exit pupil Entrance pupil
Aperture stop
§5.2 The field stop( 视场光阑 )
2ymax
Angular field of view
Vignetting (渐晕 )
Aper.stop Field Stop A0
B
Clear aperture of Aper.stop
Common aperture of two stops
Clear aperture of Field.stop
Vignetting coefficient/factor ( 渐晕系数 ): linear vignetting coefficient
KD = Dω Daxial
Daxial Dω
Area vignetting coefficient
5.3 Selection of Imaging Rays in a Apparatus
reticule
Second focal plane
Image telecentric system:
P122
It is widely used in geodetic measurement. Its effect is to eliminate the measuring error caused by the position errors of the object plane.
2. Selection of Image Rays in Microscope and Telecentric System .
P121
Telecentric System
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Object telecentric system： The aperture stop is on the ： second focal plane; the entrance pupil is at infinity. Image telecentric system： The aperture stop is on ： the first focal plane; the exit pupil is at infinity.
2 ymax
Exit window (出射窗 简称出窗 ) 出射窗,
Exit window
Field stop
Angular field of view(视场角) : the angle which the entrance window subtends from the center of entrance pupil.
D0 C0 B0 A0 A B C D
Exit pupil Exit window
The vignetting will increase as the field angle of view increases. Effect of the vignetting: If a system has the vignetting, there will be a transition area in the image plane, changing from bright to dim, without a clear borderline. Reducing the vignetting: The field stop must coincide with or be near the real image plane of the system.
Ent.pup. Ex.pup. Eye-pup.
1. For a visual apparatus, the exit pupil should coincide with the eye pupil.
Example, telescope: eye pupil is a stop in system.
aperture stop
F’
a. Object telecentric system
F
b. Image telecentric system
P121
Object telecentric system: It is often used in the measuring microscope. Its effect is to eliminate the measuring error caused by the position errors of the image plane.
Depth of Field: the distance between the farthest and the nearest object planes which can still be formed clearly on the image plane. The size of the acceptable blur is a subjective concept.
field stop: It limits the imaging range. Entrance window (入射窗 简称“入窗”) 入射窗, 简称“入窗” Exit window (出射窗 简称出窗 ) 出射窗,
Object plane
Field stop and entrance window
First focal plane
§5.4 Field Lens
1)The function of a field lens
If the field lens is placed exactly at the internal image, it has no effect on the power of the telescope, but it bends the ray bundles (which would otherwise miss the eyepiece) back toward the axis so that they pass through the eyepiece. In this way the field of view may be increased without increasing the diameter of the eyepiece.
Chapter 5 Selection of Image Rays in Optical Systems
Stop: 光阑 field of view: 视场 vigetting: 渐晕 Telecentric system: 远心光路系统
lens
film
stop Lens: limits the amount of light which can pass through the system Film: limits the imaging range. Stop：an opening aperture whose center is at ： the optic axis. Aperture Stop
•Aperture Stop: the opening in an optical system that limits the amount of light through the system sent out from axial point on the object. •Entrance Pupil: the aperture stop’s image in object space. •Exit Pupil : the aperture stop’s image in image space.
2). The focal length of the field lens
Field lens Front group Rear group
1 1 1 ′ − = , l ′ = − l 2 , l = − l1 l′ l f′
1 1 1 = '− ' f l1 l2
§5-5 Depth of Field
Exam.1 locating the aperture stop and pupils.
Aperture stop
Aperture stop
P’ Entrance pupil ( virtual image )
The aperture stop can be replaced by a hole located at the entrance pupil.
Field stop Stops, Pupils, and Windows
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limit the imaging rays in system.
§5.1 Aperture Stop
1. Aperture Stop, Entrance Pupil, Exit Pupil
( 孔径光阑 入瞳 出瞳 ) 孔径光阑, 入瞳,
discussion: 1. Z’ , △
∆ = ∆1 + ∆ 2 =
2 Dl β z ' D 2 β 2 − z '2
2. For the photographic objective,
1 1 2z' 2z' − ≈ = ' l1 l2 Df D '2 f'f
D Relative aperture: f'