troubleshooting, designing & installing digital & analog closed circuit tv systems
DESCRIPTION
The objective of this workshop is to give you practical know-how in designing, installing, commissioning, maintaining and troubleshooting analog and digital CCTV systems. The poor quality of CCTV images often seen doesn't inspire much confidence in the technology. However the purpose of this workshop is to ensure you apply best practice in all your work with CCTV systems. With the past terrorist outrages in London and other cities, CCTV systems have been essential as a key tool in fighting crime. And have perhaps shifted from being part of "Big Brother" to a useful tool. CCTV systems have undergone a remarkable technology transformation in the past decade from analog to digital and in operating on a wireless or cabled network, with a host of additional features. This has made the design and maintenance considerably more complex. This workshop thus provides you with useful expertise in building and maintaining a high quality CCTV system. The workshop commences with a detailed review of the fundamentals; progressing to optics and TV systems. Modern CCTV cameras and monitors are then examined followed by a review of video processing equipment and analog video recording. The vital changes from the analog to digital world are then examined in considerable depth. The essentials of networking as applied to CCTV systems are then discussed with practical examples. The workshop is concluded with best practice in CCTV system design and commissioning and maintenance. http://www.idc-online.com/content/troubleshooting-designing-and-installing-digital-and-analog-closed-circuit-tv-systems-25TRANSCRIPT
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Troubleshooting, Designing and Installing Digital and Analogue Closed Circuit TV
Systems
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Topics Introduction Human eye and Light Sources of light Eye persistence – motion pictures Comparison between eye and camera Optical elements Basics of a lenses Types of lenses Lenses as applied in CCTV Back-focus Adjustment Neutral Density filter (ND filter)
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Introduction
Objects are classified into two types Luminous bodies
• These are the ones which can generate light
• Example: The sun, stars, comets and other such bodies
Non-luminous bodies
• Objects that cannot produce light by themselves, but reflect the light that falls on them, are called non-luminous bodies
• Example: the Moon, planets, humans, bricks, plastic, metals etc
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Human Eye and Light
Spectrum distribution of light, with associated wavelengths
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Human Eye and Light
Response of eye at different wavelengths
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Human Eye and Light
Additive and Subtractive Mixing
Principle of additive mixing and subtractive mixing
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Human Eye and Light
Cross section of the eye
Human eye
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Human Eye and Light
Focusing of the eye is necessary to see objects at different distances
If focusing of the eye is affected then the eye may be considered as defective
Major defects found in the eye due to lack of correct focusing are Hypermetropia (farsightedness) Myopia (nearsightedness)
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Sources of Light
Colour Temperature of different light sources
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Sources of Light
Artificial lighting is illuminating a scene with a high level of evenly distributed light so that Each and every object, place or person available at that
point is clearly visible
Spectral output range for common sources of artificial light
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Sources of Light
Typical levels of illumination in indoor Typical levels of illumination at outdoor
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Sources of LightConditions Illumination Comments
Foot-Candles (FtCd)
(lux)
Direct sunlight 10,000 107,500 Daylight range
Full daylight 1000 10,750
Overcast day 100 1,075
Very dark day 10 107.5
Twilight 1 10.75
Deep twilight 0.1 1.075
Full moon 0.01 0.1075 Low light level range
Quarter moon 0.001 0.01075
Starlight 0.0001 0.001075
Overcast light 0.00001 0.0001075
Light levels under daytime and night time conditions
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Comparison Between Eye and Camera
Eye and camera similarities
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Optical Elements
Lens as optical elements The basic lenses used in optics are concave and convex
lens Important properties of lenses
• Optical plane
• Optical axis
• Focus
• Focal length
• Diopter
Properties of lens
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Optical Elements
The wavelength of the light changes as it penetrates from one medium to another
When a white light passes through a prism, its wavelength changes and appears as a spectrum of seven colours called as rainbow colours
White light refraction through prism
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Basics of Lens
Contrast Transfer Function (CTF) and Modulation Transfer Function (MTF) CTF is used to evaluate and compare the performances of
different microscopes CTF is the function which modulates the amplitudes and
phases of the electron diffraction pattern formed in the back focal plane of the objective lens
In TV lenses, the characteristic of a lens is similar to a continuous variation because the optical signal is converted in to an electrical signal. • This characteristic is known as Modulation Transfer Function
(MTF).
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Basic of Lens
CTF is given by the following equation
MTF is similar to CTF except that MTF uses sine wave spatial frequencies and CTF uses square wave
243
2sin kfkCkT S
Where Cs - The quality of objective lens defined by spherical aberration coefficientl - Wave-length defined by accelerating voltageΔf - The defocus valuek - Spatial frequency
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Basics of Lens
CTF plot for an imaginary 200 keV plot microscope(a) When envelope functions are not applied(b) When envelope functions are applied
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Basics of Lens
Spatial frequency• It is the characteristic of any structure that is periodic in space
• Spatial frequency is never constant, it varies up and down from point to point
• Modulation ‘M’ for a given spatial frequency ‘ν’ is given as
(v) M
(v) M (v) MTF
object
image
MTF is given as
I I
) I - (I M(v)
minmax
minmax
Where
I max – maximum intensitiesI min – minimum intensities
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Basic of Lens
Depth of field with different F-stops
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Basic of Lens
Near and Far focus Limits of Depth of field
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Lens as Applied in CCTV
Image and Lens Formats in CCTV A camera images the angular extent of a given screen and
is referred as ‘Angle of vision’
This vision is equal in all directions when an object is viewed through a lens and is in conical shape
The image projected by the lens is spherical in shape and the camera sensor is rectangular in shape, irrespective of the imaging circle.
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Back-focus Adjustment When a lens’ back-flange is adjusted in relation to the
CCD image plane, it is referred to as back-focusing
Back focus is the distance from the last glass surface of a lens to the focused image on the sensor
Zoom lens focusing at different distance objects
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Neutral Density filter (ND filter)
A neutral density filter is a light filter which is used to reduce the intensity of light passing through the lens
It is also referred to as gray filter or ND filter
ND4 and ND8 filters
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ND filter
When a slower shutter speed is used, moving objects may appear blurred creating a sense of motion
Image when slower shutter speed is used with both ND4 and ND8 filters
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ND filter
ND filters are used to open up the aperture while maintaining constant shutter speed
Image with larger aperture(a) With no ND filter(b) With ND4 Filter(c) With ND8 filter
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