Vivotek NR7401 User Manual download pdf (Page 18)

Chap.2 Lens and Image Sensor Technology

Megapixel

A megapixel network camera features a resolution at least three times larger than that of an analog CCTV camera.

Amegapixelcameraismainlyappliedinoccasionswhenaccurateidenticationisneededsuchasvehiclelicense

plate recognition or facial recognition for it can provide images with exceptional details. Because of its high number

of pixels, a megapixel camera is also used in spacious areas such as parking lots or airports to provide images with

a wide view.

The megapixel sensor has contributed to a new breed of non-mechanical PTZ cameras, known as digital PTZ

cameras.The cameracapturesamegapixel imageanddeliversonly auser-denedthumbnailtothemonitorso

that users can view different images by selecting on the monitor instead of physically moving the camera.

2.2.3 Sensor Scan Modes

Image sensor scan modes include interlaced and progressive scan.

Interlaced Scan

Interlaced scan split a scene into even and odd fields that contain even and odd lines, respectively. When

renderingtheentirescene,theeveneldisdisplayedrst,followedbytheoddeld.Thetimeintervalbetweenthe

appearanceofthetwoeldswillleadtojaggededges,especiallyforamovingobject.

InterlacedscanismainlyusedinTVmonitorswithalowerrefreshrate,whichcausesthescreentoickereasily.

Interlacedscancanreduceickersbecausetheeld refreshrateoftheinterlacedscanseemstwotimes faster

than the original frame rate.

Somemonitorssolvejaggededgesbydroppingoddeldandreplicatetheeveneldastheoddeld.However,the

vertical resolution will be cut by half.

Progressive Scan

Progressive scan renders the entire scene by displaying the even and odd lines of the frame sequentially instead of

byeld.Sincethereisnotimeintervalbetweeneachdisplay,theproblemofjaggededgeswhendisplayingmoving

objects is eliminated.

Progressive ScanInterlaced Scan

Progressive Scan

Interlaced Scan

Capture Display

Odd Field Even Field 1 Frame

1 Frame

Figure 2.12 Progressive scan eliminates jagged edge artifacts of interlaced scan

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 73 74

No comments

Vivotek NR7401 User Manual Page 18