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The Basics of Camera Technology

The Basics of Camera Technology

Marketing Communication Group Product Information Department Business Planning Division B&P Company Sony Corporation

Preface With the development of technologies and endeavors to reduce production costs,

originally available only on high-end video cameras,

have been introduced to a wider range of professional video cameras,

designed to target larger markets with their versatility

it has become imperative for those involved in the marketing and sales activities of such video cameras to understand these functions,

as well as become familiar with the meanings of the related terminology

Having considered this background,

we have created “The Basics of Camera Technology” a useful document that provides comprehensive explanations of all the camera terminologies we consider to be significant

These terms have been carefully selected and placed into five categories: Optical System,

CCD Mechanism,

Camera Functions,

This allows readers to quickly find relevant information according to the terminology in question

We hope this document will be helpful in your business

Marketing Communication Group Product Information Department Business Planning Division B&P Company Sony Corporation

Table of Contents Optical System Angle of View

Chromatic Aberration

Light and Color

Color Conversion Filters

MTF (Modulation Transfer Function)

Color Temperature

Neutral Density (ND) Filters

Depth of Field

Optical Low Pass Filter

Flange-Back/Back Focal Length

White Shading

F-number

Focal Length

CCD Mechanism EVS/Super EVS

Readout Mechanism

Field Integration and Frame Integration Mode

RPN (Residual Point Noise)

HAD SensorTM

Spatial Offset Technology

IT/FIT CCD

Variable Speed Electronic Shutter

On Chip Lens

Vertical Smear

Picture Element

Camera Functions Adaptive Highlight Control

ATW (Auto Tracing White Balance)

AWB (Auto White Balance)

Genlock

Black Balance

H/V Ratio

Black Clip

Intercom (Intercommunication) System

Black Gamma

Knee Aperture

Black Shading

Knee Correction

Center Marker

Lens File

Clear Scan/Extended Clear Scan (ECS)

Level Dependence

Color Bars

Limiter

Crispening

Linear Matrix Circuit

Cross Color Suppression

Low Key Saturation

Detail Level

Mix Ratio

Multi Matrix

Dynamic Contrast Control (Automatic Knee Control)

Pedestal/Master Black

Electric Soft Focus

Preset White

File System

Reference File

DynaLatitude

Optical System

Scene File

TruEyeTM (Knee Saturation Function) Processing

Skin Tone Detail Correction

Turbo Gain

Sub-carrier Phase Control/Horizontal Phase Control

V Modulation

White Balance

Tele-Prompter

White Clip

TLCS (Total Level Control System)

ClipLinkTM/Index Picture/Automatic Logging Function

SetupLogTM

EZ Focus

SetupNaviTM

Camera Functions

CCD Mechanism

Return Video

EZ Mode

51 VTRs

Others SDI

Camera Control System

Sensitivity

Camera Control Unit (CCU)

Synchronization Signal (Sync Signal)

Master Setup Unit (MSU)

VBS/BS Signal

Remote Control Panel (RCP)

Vertical Resolution

Camera Command Network Unit (CNU)

Segmented Frames)

60 RS-170A

The Basics of Camera Technology 2

Additive Mixing

C 2003 Sony Corporation

All rights reserved

Reproduction in whole or in part without written permission is prohibited

BETACAM,

DynaLatitude,

HAD sensor,

Memory Stick,

Trinitron and TruEye are trademarks of Sony

Some of images in this document are simulated

All other trademarks are the properties of their respective owners

Optical System

Optical System

CCD Mechanism

The Basics of Camera Technology

Camera Functions

VTRs Others

Optical System

Angle of View When shooting a landscape with a camera,

Angle of view becomes narrow when a telephoto lens is

there is a certain range that will be displayed on a picture

On the other hand,

angle of view becomes wider with a

Angle of view indicates the displayable range of the

wide-angle (that is why it is called "wide-angle")

image (plane) measured by the angle from the center of the

Consequently,

the wider the angle of view is,

lens to the width of the image in the horizontal,

These are called,

The angle of view depends on image size,

intended for 2/3-inch and 1/2-inch CCD cameras have differ-

Monitor

Horizontal Angle of view

Video Camera

Figure A Angle of view can be derived from the following equation

w = 2tan-1 y/2f w: Angle of view y: Image size (width of the image in horizontal,

Focal length

Angle of view

Image size

Figure B

able in lenses with longer focal lengths,

The amount of refraction depends on

oration of the edges of the image

Recent technology has made it possible to effectively reduce

This also holds true for lenses used in a video camera lens

chromatic aberration of a video camera lens

This is

The difference in refraction from color to color directly results

achieved by combining a series of converging and diverging

in each color light (in a color camera RGB) forming focus on

lenses with different refraction characteristics to compensate

For example,

The use of crystalline substances such as

the other colors will be slightly out of

fluorite has been practiced to offset the aberration and

This phenomenon is more notice-

accordingly the locus of the image reproduced

CCD Mechanism

When light passes through glass,

Optical System

Chromatic Aberration

Camera Functions

Red light's focal point Green light's focal point

Blue light's focal point

Color Conversion Filters be possible to balance the camera for all color temperatures

For example,

Sony professional video cameras

using the R/G/B amplifier gains,

are designed to be color balanced at 3200 K (white balance:

signal-to-noise ratio point of view,

refer to “White Balance” )

This is the color temperature for

up (refer to “Gain” ) is required

The color conversion filters

indoor shooting when using common halogen lamps

reduce the gain adjustments required to achieve correct

the camera must also provide the ability to shoot under

color temperatures other than 3200 K

For this reason,

a number of selectable color conversion filters are placed

Relative energy

before the prism (refer to “Prism” ) system

These filters optically convert the spectrum distribution of the ambient color 3200 K

temperature (illuminant) to that of 3200 K,

the camera's operating temperature

For example,

when shooting under an illuminant of 5600 K,

a 5600 K color conversion filter is used to Converted area

convert the incoming light's spectrum distribution to that of approximately 3200 K

Your question now may be,

"why do we need color conversion filters if we can correct the change of color temperature electrically (white balance)

The answer is quite simple

White balance (refer to “White Balance” ) electrically adjusts the amplitudes of the red (R) and blue (B) signals to be equally balanced to the green (G) by use of video amplifiers

We must keep in mind that using electrical amplification will result in degradation of signal-to-noise ratio

Although it may

The Basics of Camera Technology 3

All color cameras are designed to operate at a certain color

Optical System

Color Temperature The color reproduced by a camera largely depends on the

cameras cannot adapt automatically to the color tem-

color of the light source (or the illuminant) under which the

it is essential to select the appro-

This is sometimes difficult to understand

priate color conversion filter (refer to “Color Conversion

because the human eye is adaptive to changes in the light

Filters” ) for the shooting environment in order to obtain accu-

source's color and the color of an object will always look the

The combination of electronic White

same under any light source: sunlight,

Balance (refer to “White Balance” ) with appropriate color

conversion filter selection will create more accurate color reproduction

The color of light source is defined by using heated carbon (black body absorbing all radiation without transmission and reflection) as a reference

When heating a piece of carbon,

it will start glowing and emitting light when it reaches a certain absolute temperature (expressed in Kelvin or (K))

The spectral distribution of the light emitted from the light source is determined by its corresponding absolute temperature,

Light Source Skylight Noon Sunlight Sunrise and Sunset 12 V/100 W Halogen Lamp Candlelight

Color Temperature (approx

Depth of Field When focusing a lens on an object,

there is a certain distance range in front of and behind the object that also comes into focus

Depth of field indicates the distance between the closest and furthest object that are in focus

When this distance is long,

the depth of field is "deep" and when short,

Needless to say,

any object outside the depth of field (range) will be out of focus and look blurred

Thus depth of field can be controlled by changing these fac-

Depth of field is governed by the three following factors:

allowing the camera operator creative shooting techniques

Deep depth of field

Shallow depth of field

Flange-Back/Back Focal Length Flange-back is one of the most important matters to consider

In a 3-

Flange-back describes the distance

CCD camera,

the flange-back additionally includes the dis-

from the camera's lens-mount reference plane (ring surface

tance that the light travels through its prism (the distance the

or flange) to the image plane (such as CCDs) as shown in the

light travels in the glass material,

It is necessary to select a lens with the appro-

plus the rest of the distance between the lens

priate flange-back for the given camera

Flange-back is mea-

sured differently depending on whether the camera uses

In today's camera systems,

flange-back is determined by the

glass materials in its light path (like a prism: refer to “Prism” )

lens-mount system that the camera uses

ing light into their three primary color components,

use either the C-mount or CS-mount system

The flange-

then captured by each associated CCD

Single CCD cam-

back of the C-mount and CS-mount systems are standard-

Similar to flange-back is back focal length,

three flange-back standards for the bayonet mount system,

the distance from the very end of the lens (the end of the cyl-

inder that fits into the camera mount opening) to the image plane

The back focal length of the camera is slightly shorter

Optical System

There are

Back focal lenght

CCD Mechanism

Flange-back

numerous diffused reflections of the incoming light inside the

In order to minimize the effects of flare,

This results in the black level of each red,

cameras are provided with a flare adjustment function,

and/or inaccurate color balance

optimizes the pedestal level and corrects the balance

On a video monitor,

between the three channels electronically

causes the picture to appear as a misty image,

light passes through the camera lens

Flare is caused by

Camera Functions

Flare Flare is a phenomenon that is likely to occur when strong

F-number The maximum aperture of a lens indicates the amount of light

diaphragm within the lens (refer to “Iris” )

The lens iris ring is

that can be gathered by the lens and directed to the camera

These calibrations increase by a

A larger physical diameter lens will receive light over

so lenses normally carry calibrations of 1

Since the amount of incoming

expressed as an F-number (or F-stop),

light is proportional to the cross-sectional area,

value of the F-number (F) is mathematically calculated by

ness of an image is in inverse proportion to the second power

dividing the focal length (refer to “Focal Length” ) (f) by the

Simply put,

effective aperture of the lens (D),

the brightness will decrease to one

F = f/D

This reciprocal relationship means that the smaller the Fnumber,

and the higher the sensitivity it

It is important to know that the F-number or F-stop is a key

The maximum aperture F-number

factor that affects the depth of field of the scene shot by the

is labeled on the front of the lens,

camera (refer to “Depth of Field” )

The smaller the F-number

guishing factor when comparing lenses

In lenses used with

the shallower the depth of field will

TV cameras,

a mechanism is required to reduce the sensitiv-

and this is achieved by a variable f: Focal length

Lens D: Effective aperture

Incoming light

The Basics of Camera Technology 5

and therefore is more efficient

The aperture is

Optical System

Focal Length Focal length describes the distance between the lens and the

Video camera lenses usually consist of a series of individual

point where the light that passes through it converges on the

lenses for zooming and aberration-compensation purposes

This point is where the lens is in focus and is

(refer to “Chromatic Aberration” ),

To capture a focused image on a CCD

focal point called the principal point

the focal point must coincide with the CCD imager plane by controlling the focus of the lens

Focal length

Focal point

Iris The amount of light taken into a camera and directed to its

imager is adjusted by a combination of diaphragms inte-

(also called aperture) changes,

thus controlling the amount of

This mechanism is called the lens iris and

The amount of the iris opening is

functions just like the pupil of the human eye

By opening

expressed by its F-number (refer to “F-number” )

This can be explained with a prism

retina of the human eye reacts to light when we view objects

in which the light that passes through it is

Technically,

light consists of various electromagnetic waves

separated into its individual light components

each with a different wavelength

The human eye is only

sensitive to electromagnetic waves whose wavelengths fall

Coming back to our main subject,

between approximately 380 and 760 nanometers

object with a different color is because each object has differ-

range of electromagnetic waves is called the visible spec-

ent light-reflection/absorption characteristics

For example,

and indicates the range of light that the human eye can

piece of white paper reflects almost all light colors and thus

To the human eye,

each wavelength is viewed as a dif-

Similarly,

a pure blue object only reflects the

blue light (spectrum) and absorbs all other light colors

Light emitted from a typical light source (sunlight,

light colors that each object reflects are governed by the

cence/halogen lamps) is a combination of a variety of differ-

characteristics of the surface of the objects

CCD Mechanism

The human eye is sensitive to light

Or in other words,

Optical System

Light and Color

although the light source may seem to look Camera Functions VTRs

It's Green

Only a green spectrum is reflected on the leaves

Other colors are absorbed

The Basics of Camera Technology 7

Optical System

MTF (Modulation Transfer Function) Modulation Transfer Function (MTF) is an important index

When choosing a television lens,

that indicates a lens's capability of reproducing the contrast

to inspect the characteristic of the MTF at the low to mid fre-

MTF is measured as the lens's contrast

quencies in addition to the lens's final resolving power

which is the capability of resolving the fine

is because the low to mid frequency areas of a lens usually

black and white vertical lines on a resolution chart

represent the main frequency areas used in the NTSC or PAL

lenses are typically less sensitive to higher spatial frequen-

video signal (refer to “NTSC/PAL” )

It is essential to have a

cies (narrower black and white lines),

high response (close to 100%) in this area,

ibility attenuates as the frequency increases

The MTF curve

video picture will not be reproduced with sharp contrast

shown below as a graph with the spa-

Lens B is capable of resolv-

tial frequency on the horizontal axis and contrast reproduc-

ing the image at higher spatial frequencies (detailed areas of

Note that the MTF value changes

the image) and may often be misevaluated to having more

until it reaches a point where the lines can no longer be

However,

This point indicates the final resolving power of the

has the higher resolving power,

or the narrowest black and white lines that can be

tance in most camera applications

Needless to say,

the higher the value of contrast

When choosing a lens,

both its MTF curve and final resolving

the more faithfully contrast is reproduced at

power must be considered with care depending on the appli-

This means that lenses with

higher MTF values at each frequency reproduce contrast bet-

MTF Lens A can produce higher image quality

Higher Contrast Reproducibility

Lens B Point X Lens B can produce higher image quality

Higher Resolving Power

Neutral Density (ND) Filters When shooting outdoors,

the camera is often subjected to

not affect the color temperature (refer to “Color Temperature”

In some cases,

) of the incoming light since attenuation is uniform over the

be handled even with the smallest iris opening of the lens

ND filters may also be used to intentionally

For this reason a few types of selectable ND filters are placed

select a wider iris (refer to “Iris” ) opening

As the depth of

before the prism (refer to “Prism” ) system with the color con-

field (refer to “Depth of Field” ) is in reverse proportion with

version filters (refer to “Color Conversion Filters” )

These ND

the camera operator can inten-

filters attenuate the magnitude of incoming light to allow

tionally defocus objects in front of and behind the object that

The use of ND filters does

is being shot using the appropriate ND filter

Due to the physical size and alignment of the photo sensors

An optical low pass filter is placed in front of the CCD prism

when an object with fine detail,

block and only allows light with relatively lower frequencies to

a rainbow-colored pattern known

Since this type of filtering may also reduce picture detail,

the characteristics of an optical low pass filter

pen when the frequency of the lens's incoming light exceeds

are determined with special care

the CCD's spatial-offset frequency (refer to “Spatial Offset

but without degrading the camera's maximum resolving

Technology” ) determined by the spacing between each

In order to reduce such Moire patterns from appearing,

optical low pass filters are used in CCD cameras

CCD Mechanism

as Moire may appear across the image

This tends to hap-

Optical System

Optical Low Pass Filter

Prism length

For example,

reflected by any of the prisms and thus is directed straight to

video signals by first separating the incoming light into the

Red is not reflected at the surface of the sec-

This is done by

but gets reflected at the third,

which is an arrangement of three

more reflection within the second prism,

The prism system utilizes the different reflection

Camera Functions

As explained in the section titled Additive Mixing (refer to

characteristics that light has depending on its color or wave-

VTRs Others

Incoming light CCD CCD Camera Color separation system of a 3-CCD camera

The Basics of Camera Technology 9

Optical System

White Shading White Shading is a phenomenon in which a green or

spectral characteristics of the prism

This effect is seen as

magenta cast appears on the upper and lower parts of the

the upper and lower parts of the screen having a green or

even when the white balance (refer to “White Bal-

magenta cast even when the white balance is correctly

ance” ) is correctly adjusted in the center of the screen

White shading is seen in cameras that adopt a dichroic layer

White shading is more commonly due to the lens having an

(used to reflect one specific color while passing other colors

uneven transmission characteristic and is seen typically as

through) in their color separation system

In this system,

the center of the image being brighter than the edges

This is

corrected by applying a parabolic correction waveform to the

using color prisms (refer to “Prism” )

The three-color prisms

variable gain amplifiers used for white balancing

use a combination of total reflection layers and color selective reflection layers to confine a certain color

For example,

Another cause of White Shading is uneven sensitivity of the

blue prism will confine only the blue light,

In this case,

ing phenomenon is not confined in the upper and lower parts

However,

the color-filtering characteristics of each prism

slightly change depending on the angle that the light enters

Sony high-end professional BC cameras are equipped with

(angle of incidence) each reflection layer

This angle of inci-

circuitry that automatically performs the proper adjustment to

dence causes different light paths in the multi-layer structure

suppress the White Shading phenomenon

of the dichroic coating layer and results in the change of the

Red-reflecting dichroic coating Green cast

Magenta Cast

Blue-reflecting dichroic coating

Technically,

'zoom' refers to changing a lens's focal length

In the telephoto position,

(refer to “Focal Length” )

A lens that has the ability to contin-

light is reflected from the subject and directed through the

ually alter its focal length is well known as a zoom lens

and thus the iris must be adjusted accordingly

Optical System

Zoom lenses allow the cameraperson to change the angle of Since chromatic aberration (refer to “Chromatic Aberration” )

in turn changes the area of the image that is directed to the

and other light-diffusion characteristics change when the

CCD image

For example,

by zooming-in to an image (the

high-quality zoom lenses use a

less of the image will be directed to

series of compensation lenses (which account for the higher

the lens and thus that area of the image will appear to be

Zooming-out (wide angle position) means that more of the image is directed to the imager and thus,

The correlation between the zooming ratio and angle of view

It also must be noted that the

can be described as shown in the figure below

CCD Mechanism

view (refer to “Angle of View” )

Changing the angle of view

amount of light directed to the imager also changes when Camera Functions

8 mm 8 mm

Correlation between zooming and angle of view

The Basics of Camera Technology 11

Optical System

CCD Mechanism

CCD Mechanism

The Basics of Camera Technology

Camera Functions

VTRs Others

CCD Mechanism

EVS/Super EVS EVS (Enhanced Vertical Definition System) and Super EVS

ing the same high vertical resolution

However,

are features that were developed to improve the vertical reso-

Since Super EVS is an enhanced form of

sacrifices its sensitivity to one-half

let's first look into the basic technology used in EVS

Super EVS has been created to provide a solution to this

EVS has been developed to provide a solution when

The charge readout method used in Super

improved vertical resolution is required

Technically,

EVS sits between the Field Integration and EVS

Instead of

mechanism is based on Frame Integration (refer to “Field

discarding all charges accumulated in the first 1/60 seconds,

Integration and Frame Integration Mode” ),

Super EVS allows this discarded period to be linearly con-

picture blur inherent to this mode by effectively using the

When the period is set to 0,

same as when using Field Integration

Conversely,

As explained in Frame Integration,

the results will be identical to Frame Integration

the longer 1/30-second accumulation period

EVS eliminates

Super EVS will provide a combi-

this by discarding the charges accumulated in the first 1/60

nation of the improved vertical resolution of EVS but with less

Most importantly,

charges accumulated in the second 1/60 seconds

Just like

tion improvement and picture blur will depend on the selected

Frame Integration,

EVS uses the CCD's even lines to create

This can be summarized as follows:

even fields and its odd lines to create odd fields

When set near 0: less improvement in vertical resolution,

When set near 1/60: more improvement in vertical resolution,

Each photo site Field Integration • High in sensitivity but low in resolution

Super EVS • Advantages of both Field Integration and Frame Integration (Technically inbetween the two)

• The electric shutter is operated at a different timing in alternated lines

Even Electrons are NOT discarded completely

Discarded electron Effective electron

EVS (Frame Integration) • High in resolution but low in sensitivity

• Shutter speed is set to 1/60s for NTSC or 1/50s for PAL

• Electrons are to be discarded to the overflow drain of the CCD

CCDs usually have about the same number of vertical pixels

This method is known to provide high vertical resolution but

as the number of scanning lines that the TV system does

has the drawback of picture blur since images are captured

For example,

in the NTSC (refer to “NTSC/PAL” ) system,

across a longer 1/30-second period

there are 480 effective TV scanning lines and therefore

The Field Integration method reduces this blur by shortening

CCDs used in this system have about 490 vertical pixels

the accumulation intervals to match the field rate,

this would mean that the charge

tant to keep in mind that only half of the total scanning lines

accumulation would drop to one-half due to the shorter accu-

are displayed at a time (known as a field)

This also means

Field Integration avoids this by combining

that the CCD should readout only half the number of its verti-

the charges of two vertically adjacent photo sites and reading

cal samples to create a picture field

There are two readout

them to the vertical register in pairs

Each pair represents

one pixel on the interlaced scanning line as the aggregation

Integration method,

which is most commonly used today

of two adjacent vertical pixels

Odd and even fields are crebined

Although this method is most commonly used,

accumulates the charge for one full frame (1/30 second/two

be noted that less vertical resolution is provided compared to

fields) before it is readout to the vertical register

To create

This is simply because the pic-

the charges of the CCD's even lines are readout,

ture information of two adjacent pixels is averaged in the ver-

the charges for the odd lines are readout

tical direction due to the physically enlarged sensing area

Pixels B,

Charge Integration

Frame Integration 1 frame A B C D'E

X X X X

Charge Integration

Time A+B

A+B B+C

B+C C+D

Field Integration CCD Read Out Modes

The Basics of Camera Technology 15

Pixels A,

Field Odd Even

Camera Functions

ated by altering the photo sites of which charges are comIn the Frame Integration method,

CCD Mechanism

However,

if every other line was read out to create In interlace TV systems (such as NTSC or PAL),

Optical System

Field Integration and Frame Integration Mode

CCD Mechanism

HAD SensorTM The HAD (Hole Accumulated Diode) sensor is a diode sensor

The Hole Accumulated Layer also plays an important role in

which incorporates a Hole Accumulated Layer on its surface

The amount of lag in CCDs is determined by

This layer effectively reduced dark current noise,

the efficiency of transferring the electrons accumulated in the

caused by electrons randomly generated at the Si-Si02

photo sensor to the vertical shift register

In CCDs without a

The Hole Accumulated Layer pairs up holes

Hole Accumulated Layer,

the bottom (potential) of the photo-

with the electrons generated at the CCD surface,

sensing well tends to shift and,

the number of electrons (amount of dark current noise) that

electrons will remain in the well even after readout

However,

enter and accumulate in the sensor

The reduction of dark

since the Hole Accumulated Layer

current noise results in a reduction in fixed pattern noise,

clamps the bottom of the photo-sensing well to the same

high signal-to-noise ratio (refer to “S/N (signal-to-noise)

the accumulated electrons will fall completely into

Ratio” ),

electrons will not remain in the photo-sensing well after readout

Surface direction

Depth direction

Surface direction

Potential fixed due to HA layer

Potential N-Substrate Sensor

Depth direction

(a) CCD without HAD sensor structure

Potential N-Substrate Sensor

V-Regi ROG

IT/FIT CCD CCDs are categorized into two types,

Smear appears as a vertical line passing through the

CCD's structure and the method used to transfer the charge

often seen when shooting a bright object in the

accumulated at each photo site to the output

This phenomenon is due to electric charges,

The IT (Interline-Transfer) CCD takes a structure such that

lated in highly exposed photo sites,

the column of photo-sensing sites and vertical registers are

register before the transfer from the photo sites to the vertical

The photo-sensing sites (so-called pix-

els) convert the incoming light into electrical charges over a 1/60-sec period (1/60 secfor NTSC,

The FIT (Frame Interline Transfer) CCD was primarily

After this period,

designed to overcome this drawback

The upper part of this

are transferred to the vertical shift registers during the vertical

device operates exactly like an IT CCD,

The charges within the same line (the

sensing area and charge shifting registers

The bottom part

same row in the CCD array) are then shifted down through

operates as a temporary storage area for the accumulated

the vertical shift register in the same sequence and read into

charges: immediately after the charges are transferred from

Once a given line is read

the photo-sensing area to the horizontal registers (during the

it is immediately read out (during

they are quickly shifted to this fully

the same horizontal interval) so the next scanning line can be

Since the charges travel through the

vertical register over a very short period,

The only significant limitation in the IT imager structure is an

unwanted charges leaking into the vertical register from the

artifact called vertical smear (refer to “Vertical Smear” ),

which appears when the CCD is exposed to an extreme high-

due to the use of a HADTM sensor and On Chip Lens technol-

usually costs more than an IT CCD

ogy (refer to “HAD SensorTM” and “On Chip Lens” )

However,

it most be noted that in recent Sony IT CCDs,

the vertical smear has been reduced to an almost negligible level Vertical shift register

Optical System

The FIT structure thus offers superior smear performance but

Photo sensor

CCD Mechanism

IT CCD Temporary storage area

Camera Functions

Horizontal shift register

FIT CCD

On Chip Lens As compared to the human eye's ability to see in the dark,

CCD cameras have a limitation in sensitivity (refer to “Sensitivity” )

Many technologies have been developed to improve sensitivity

On Chip Lens (OCL) technology drastically enhances the light-collecting capability of a CCD by placing a microlens above each photo sensor so that light is more effectively

On-Chip-Lens

The combination of Sony HAD-sensor technology and OCL has achieved tremendous improvement

even under extremely low-light conditions

Since each micro-lens converges the incoming light to each photo-sensing area,

less light leaks into the CCD's vertical register,

greatly reducing vertical smear (refer to “Vertical

N+ 2nd P-Well

Hole Accumulated Layer

1st P-Well

Smear” )

N-Substrate Sensor C

S (Channel R

G stop) V-register (Read out gate)

Sensed light

The Basics of Camera Technology 17

CCD Mechanism

Picture Element CCD specifications are indicated with the number of horizontal and vertical picture elements they have within their photosensitive areas

A picture element contains one photo sensor to sample the intensity of the incoming light directed to it

The number of picture elements within the CCD's sensing area is the main factor,

which determines the resultant resolution of the camera

It must be noted that certain areas along the edges of the CCDs are masked

These areas correspond to the horizontal and vertical blanking periods and are used as a reference for absolute black

there are two definitions in describing the picture elements contained within the CCD chip

CCD picture element

'Total picture elements' refers to the entire number of picture elements within the CCD chip,

including those which are masked

'Effective picture elements' describes the number of

Masked picture element

picture elements that are actually used for sensing the incoming light

Effective picture element

Readout Mechanism CCDs are the most popular imaging devices used in today's

Figure C describes the structure of an Interline Transfer (refer

In brief,

CCDs convert incoming light directed

with the photo sensors used for the light-to-

through the camera lens into electrical signals that build a

charge conversion and the charge readout mechanism (to

Since the mechanism of a CCD is very similar

The photo sensors,

it is worthwhile to take a look at the how

convert the incoming light into electrical charges

the human eye works and compare this to a CCD

As figure

light conversion and charge accumulation continues over a

A shows below,

After the 1/60-second period,

directed to and formed on the retina,

electrical charges at each photo sensor are transferred to the

eral million photosensitive cells

The retina then converts the

vertical shift registers during the vertical blanking interval

light that forms this image into a very small amount of electri-

The charges within the same lines (the same row in the CCD

These are then sent to the brain through the

array) are then shifted down through the vertical shift register,

This is the basic mechanism of how

during the next 1/60-second accumulation period,

line by line at a frequency of

Coming back to the mechanism of a CCD,

photo sensors that work exactly like the retina's photosensi-

given line is read into the horizontal register,

However,

the electrical charge readout method is

readout (during the same horizontal interval) so the next

scanning line can be read into the horizontal register

Optical System

Figure A: Mechanism of human eyeball Retina Brain cells Pupil

CCD Mechanism

Light to electricity conversion

Figure B: Mechanism of CCD camera

Picture monitor Vertical shift register

Photo sensor

Camera Functions

VTRs Others

Horizontal shift register Figure C: CCD Readout mechanism

RPN (Residual Point Noise) RPN stands for Residual Point Noise

This term refers to a

On the other hand,

white or black spot seen on a picture monitor due to a defect

electrically offsets the unwanted level shift,

Generally,

these spots consist of up to several

numbers of destroyed pixels in the horizontal and/or vertical

Distinct causes of dead pixels and blemishes are still under

which cannot reproduce colors properly

Until now,

These spots can be categorized into two types

believed that cosmic rays cause damage to the CCD pixels

While dead pixels can no longer reproduce

during high-altitude transportation in an aircraft

This is

they just cannot reproduce colors

based on the statistics of greater numbers of cameras trans-

properly due to an unwanted level shift of the charges accu-

Sony has developed concealment and compensation technologies to counter dead pixels and blemishes,

Concealment technology intelligently interpolates dead pixels using adjacent picture data in the horizontal and vertical

The Basics of Camera Technology 19

CCD Mechanism

Spatial Offset Technology Spatial Offsetting is a method used to improve the luminance

amount of signal charges accumulated in each photo sensor

horizontal resolution of CCD cameras

Use of this technique

is shown in 1 through 7 as signal level

If displayed on a

allows a higher resolution to be achieved than theoretically

the green CCD signal levels would appear as

expected with the number of picture elements that each CCD

shown in A' and the red and blue signal levels would appear

As shown in (a),

the red and blue CCD chips are

fixed to the prism block with a one-half pitch offset in horizon-

These represent the resolution without spatial offsetting

tal direction in respect to the green CCD chip

number of samples (picture elements) within a line to create

The luminance signal,

which is defined in TV standards as an

the luminance signal is double,

addition of R/G/B signals with certain weights on each signal,

than when spatial offset is not used

is equivalently provided by adding A' and B' in spatial offset-

This can also be explained by examining the outputs of the

This is shown in C'

As a result,

When shooting a subject (for better under-

imagine a black triangle written on a white sheet of

Furthermore,

when Spatial Offsetting is done,

paper) with a CCD camera using spatial offset,

facts caused by the CCD clock signal will be decreased and

thus contribute to reproducing sharper picture images

A and B in (c) are enlargements of areas A and B in (b)

"Picture insertion"

CCD (R and B)

P CCD(G)

P: pitch

V Resister Photo sensor

CCD(R/B) A'

HALF PICTURE ELEMENT C'

tion period to be shortened using the electronic shutter func-

This function is similar to mechanical shutters

The electronic shutter operates in such a manner that

used in film cameras and can be used in the very same way

when a certain shutter speed is selected,

When activated,

it allows the camera to capture objects mov-

electrons accumulated only during this period are

ing at high speeds with less picture blur

output to the vertical register

All electrons accumulated

To understand how this function works,

before this period are discarded

The result is that movement

ing the mechanism of an IT CCD (refer to “IT/FIT CCD” )

capture only within the short shutter period will be captured

Incoming light is converted to electrons (electrical charges) at

effectively reducing the picture blur of fast-moving

where they are accumulated over a certain

period and then transferred to the vertical shift register

It is also important to note that shortening the accumulation

the electronic shutter is set to OFF (1/60 second,

1 field),

period results in a drop in sensitivity,

trons are accumulated over the entire field period (1/60 sec-

sated for by using a wider iris opening

Higher shutter speed

ond) and then readout to the vertical register

However,

is sometimes used for the purpose of getting shallow depth of

there is fast movement in the picture during this accumulation

field (refer to “Depth of Field” ) with a wider iris (refer to “Iris” )

opening instead of using neutral density filters (refer to “Neutral Density (ND) Filters” )

Generated electrons

Vertical shift register

Camera Functions

To avoid this blur,

CCD cameras allow the electron accumula-

ment of an electronic shutter,

which was not available in any

CCD Mechanism

The use of CCDs in video cameras has enabled the develop-

Optical System

Variable Speed Electronic Shutter

Horizontal shift register

Shutter period Discarded electrons

Shutter period

Shutter period

Output electrons

(b) Principle of electronic shutter

The Basics of Camera Technology 21

CCD Mechanism

Vertical Smear Vertical Smear is a phenomenon peculiar to CCD cameras,

constantly leak into the vertical register while it shifts down to

which occurs when a bright object or light source is shot with

This phenomenon is observed on the video

The amount of smear is generally in proportion to the inten-

monitor as a vertical streak above and below the object or

sity of the light from the subject or light source and the area

A most notable example is

when the headlights of a vehicle are shot with a CCD camera

Smear in recent Sony CCD cameras has been drastically

Smear is caused by the direct leakage of incoming light into

reduced to a level that is almost negligible due to the use of

the vertical shift register or the overflow of the electrical

the HAD sensor (refer to “HAD SensorTM” )

charges accumulated in the photo sites

The reason that smear is observed as a vertical streak is because electrons

Vertical smear

Vertical smear is reduced by the use of HAD sensor

Optical System

Camera Functions

CCD Mechanism

The Basics of Camera Technology

Camera Functions

VTRs Others

Camera Functions

Adaptive Highlight Control Conventional cameras only have a single knee point/slope

Input signal level

(refer to “Knee Aperture” and “Knee Correction” ) characteristic

In contrast,

the Sony ADSP (Advance Digital Signal

Processing) system has multiple knee point/slope characteristics

The camera intelligently monitors the brightness of all areas of the picture and adapts the knee point/slope for opti-

Multiple knee point/slope

A typical example is shooting an interior scene,

which includes a sunlit exterior seen through a window

This function applies only to video levels in excess of the knee point,

the middle and low luminance parts remaining unchanged

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