Optics Lenses

7/29/2019 Optics Lenses

1/26

. . . M A K E S Y O U R N E T W O R K S M A R T E R

Lenses & Filters


2/26

Compression CPU

Flash

memory

DRAM

Ethernet

Interface

Camera

functions

Lens Optical filter Image sensor

Lens and optical filter in a camera


3/26

Filters - IR filter

Filters the Infrared light invisible for thehuman eye but visible for cameras

Transmission curve (Example)

20

0

40

60

80

100

300 400 500 600 700 800 900 1000 1100

I/RVisible light

IR Radar TV Sound Radio

Radio WavesY

Rays

X

Rays UV

300 400 500 600 700 800 900

Wavelength

Wavelength in nanonmetres


4/26

Filters - Optical low pass filter

Splits the incominglight

Improves color

representation


5/26

Filters Example: Without optical low pass filter


6/26

Filters Example: With optical low pass filter


7/26

The Lens

Tele(photoangleofvi

ew)Wid

eangle(ofvie

w)Focal length

IrisMountLens

element


8/26

Angle of view

Same as Field of view

What the camera with a given lens can see

Horizontal, vertical or diagonal

Horizontal Angle of

View (HOV)Vertical Angle of View

(VOV)


9/26

Lenses - Focal length

A small focal length gives wide angle view.A large focal length gives tele view.

Focal point

Focal length


10/26

Lenses Calculating the focal length

Which focal length is needed for theapplication?

Calculating the focal length (f): f = D*I/ W

W

D f

I


11/26

Lenses Depth of field

The regions in front of and behind the focuspointwhere the image remains in focus

Depthoffield

Focus point


12/26

Lenses - Aperture

F

numberf1.0 f1.2 f1.4 f1.7 f2.8 f4.0 f5.6

% of light

passed20% 14.14% 10% 7.07 2.5% 1.25% 0.625%

F2

F5.6

F16

0

0

5'

1.5m

10'

3m

15'

4.5m

20'

6m

25'

7.5m 88


13/26

Lenses Lens Iris

Opening in the lens that controls the amount of

incoming light that reaches the image sensor

A wire between the camera and the lensis needed with an automatic iris lens.


14/26

Lenses - Lens elements

A lens containsseveral lens elements

Aspherical elements

reduces distortion

Spherical lens element

Image plane

Aspherical lens element

Image plane


15/26

Lenses- Mount standards

C-mount Lens

17.526 mm

CS-mount Lens

12.5 mm

5 mm spacer

CS-mount

12.5mm from camera edge to sensor

C-mount 17.5mm from camera edge to sensor

Conversion C to CS is possible


16/26

Lenses Sensor dependency

Horizontal

Vertical

Image Size

Image Circle

Image Size The lens must make animage circle large enough tocover the sensor

Larger sensor = more

expensive lens The size (e.g. 1/3) can not be

measured anywhere.corresponds to old TVcamera tubes

Low end lenses produces

unsharp corners


17/26

Lenses - Resolution

A typical CCTV lens has a resolution of 100 lines/mm.

1611864.5

1"

1/4" 1/3"1/2"

2/3"

1"1/4" 1/3" 1/2" 2/3"


18/26

Lenses Types: Wide angle

Focal point

Short focal length

Large angle of view

Good in low light

Good depth of field

Barrel distortion

Not for longdistances


19/26

Lenses Types: Wide angle image example

Example of barrel distortion & missing opticallow pass filter


20/26

Lenses Types: Telephoto

Focal point

Long focal length

Good on longdistance

No barrel distortion

Shallow (small )depth of field

Bad in low light


21/26

Lenses Types: Vari-focal

The focal length can be adjusted

Needs refocusing after focal length adjustment

Less precision needed in focal length calculation


22/26

Lenses Types: Zoom

Zoomthe focal length can be adjustedwith maintained focus

Often motorised.

S


23/26

Special Lenses Fish eye

Extremely wide angle (~180 deg) lenses arecalled Fish eye lenses

L E l Fi h i


24/26

Lenses Example: Fisheye image

A fish eye lens on a high resolution cameracan work as a pan/tilt/zoom camera

S i l L Pi h l


25/26

Exit pupil is 1-3mm.

Can be either low end $1 lenses or high end>$500 lenses.

Special Lenses Pin hole

Q ti & A


26/26

Questions & Answers

ZYX KH

D

O

U

395

2

3YZ

XYZ15

POP

PQ

10.000

OPQ

YZ KHD

Optics Lenses

Documents

Transcript of Optics Lenses