Vivotek IP Surveillance, Обзор

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Chap.2 Lens and Image Sensor Technology
15
2.3.2 View Angle
View angle is determined by the focal length of the lens and the sensor size. The shorter the focal length (Figure 2.15)
and the larger the sensor size (Table 2.2), the wider the view angle.
f= 8
f=4
Focal length
Horizontal view angle
Vertical view angle
Diagonal view angle
4 mm 6 mm 8 mm 12 mm
61
∘
48
∘
73
∘
43
∘
33
∘
53
∘
33
∘
25
∘
41
∘
22
∘
17
∘
28
∘
Focal length
Vertical view angle
Horizontal view angle
Diagonal view angle
4 mm 6 mm 8 mm 12 mm
48
∘
37
∘
58
∘
33
∘
25
∘
41
∘
25
∘
19
∘
31
∘
17
∘
12
∘
21
∘
(a)
(b)
Figure 2.15 View angle for different focal length with same sensor size
Table 2.2 View angle for different focal length with (a) 1/4” and (b) 1/3” sensors
2.3.3 Day and Night
Infrared light has a different wavelength from visible light, leading to jagged and blurred images. The day and night
functionality can reduce the influence of infrared light on image quality and can be achieved by using an IR-cut filter
removable and IR-corrected lens. During the daytime with sufficient illumination, infrared light is blocked to avoid
color shift. During the night, infrared light can be utilized to enhance cameras’ night vision so as to maintain good
image quality.