Symbols and Terminology

Symbols and Terminology
Vishay Semiconductors
Symbols and Terminology
A
A
A
a
B
BER
bit/s
C
C
C
C
°C
CCEO
cd
CD
Cj
d
D*
E
EA
Anode, anode terminal
Ampere, SI unit of electrical current
Radiant sensitive area, that area which is radiant
sensitive for a specified range
Distance, e.g. between the emitter (source) and
the detector
Base, base terminal
Bit Error Rate
Data rate or signaling rate
1000 bit/s = 1 kbit/s, 106 bit/s = 1 Mbit/s
Capacitance, unit: F (farad) = C/V
Coulomb, C = s x A
Cathode, cathode terminal
Collector, collector terminal
Degree Celsius, Celsius temperature, symbol t,
and is defined by the quantity equation t = T - T0.
The unit of Celsius temperature is the degree
Celsius, symbol °C. The numerical value of a
Celsius temperature t expressed in degrees
Celsius is given by t/°C = T/K - 273.15
It follows from the definition of t that the degree
Celsius is equal in magnitude to the Kelvin, which
in turn implies that the numerical value of a given
temperature difference or temperature interval
whose value is expressed in the unit degree
Celsius (°C) is equal to the numerical value of the
same difference or interval when its value is
expressed in the unit Kelvin (K).
Collector emitter capacitance, Capacitance
between the collector and the emitter with open base
Candela, SI unit of luminous intensity. The
candela is the luminous intensity, in a given
direction, of a source that emits monochromatic
radiation of frequency 540 Hz x 1012 Hz and that
has a radiant intensity in that direction of 1/683 W
per steradian. (16th General Conference of
Weights and Measures, 1979), 1 cd = 1 lm ⋅ sr -1
Diode capacitance, total capacitance effective
between the diode terminals due to case, junction
and parasitic capacitances
Junction capacitance, capacitance due to a p-n
junction of a diode, decreases with increasing
reverse voltage
Apparent (of virtual) source size (of an emitter),
the measured diameter of an optical source used
to calculate the eye safety laser class of the
source. See IEC 60825-1 and EN ISO 11146-1
Detectivity A ⁄ NEP
Emitter, Emitter terminal (phototransistor)
Illumination at standard illuminant A, according
to DIN 5033 and IEC 306-1, illumination emitted
from a tungsten filament lamp with a color
temperature Tf = 2855.6 K, which is equivalent to
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542
standard illuminant A, unit: lx (Lux) or klx
EA amb
Ambient illumination at standard illuminant A
echo-off Unprecise term to describe the behavior of the
output of IrDA® transceivers during transmission.
“Echo-off” means that by blocking the receiver the
output RXD is quiet during transmission
echo-on Unprecise term to describe the behavior of the
output of IrDA® transceivers during transmission.
“Echo-on” means that the receiver output RXD is
active but often undefined during transmission. For
correct data reception after transmission the
receiver channel must be cleared during the
latency period
Ee, E
Irradiance (at a point of a surface), quotient of the
radiant flux dΦe incident on an element of the
surface containing the point, by the area dA of that
element. Equivalent definition. Integral, taken over
the hemisphere visible from the given point, of the
expression Le ⋅ cosθ ⋅ dΩ, where Le is the radiance
at the given point in the various directions of the
incident elementary beams of solid angle dΩ, and
θ is the angle between any of these beams and the
normal to the surface at the given point
Ee
dΦe
= ------------------ =
dA
∫
⎛
⎝
Le ⋅ cos θ ⋅ dΩ⎞⎠
2πsr
unit: W ⋅ m-2
Ev, E
Illuminance (at a point of a surface), quotient of
the luminous flux dΦv incident on an element of the
surface containing the point, by the area dA of that
element. Equivalent definition. Integral, taken over
the hemisphere visible from the givenpoint, of the
expression Lv ⋅ cosθ ⋅ dΩ, where Lv is the
luminance at the given point in the various
directions of the incident elementary beams of
solid angle dΩ, and θ is the angle between any of
these beams and the normal to the surface at the
given point
Ev
dΦv
= ----------------- =
dA
∫
⎛
⎝
Lv ⋅ cos θ ⋅ dΩ⎞⎠
2πsr
unit: lx = lm ⋅ m-2
F
Farad, unit: F = C/V
f
fc, fcd
Frequency, unit: s-1, Hz (Hertz)
Cut-off frequency - detector devices, the
frequency at which, for constant signal modulation
depth of the input radiant power, the demodulated
signal power has decreased to ½ of its low frequency
value. Example: The incident radiation generates a
photocurrent or a photo voltage 0.707 times the
value of radiation at f = 1 kHz
(3 dB signal drop, other references may occur as
e.g. 6 dB or 10 dB)
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For technical questions concerning detectors, contact: [email protected]
Document Number: 81252
Rev. 1.3, 18-Aug-08
Symbols and Terminology
Symbols and Terminology
fs
FIR
Switching frequency
Fast infrared, as SIR, data rate 4 Mbit/s
Ia
Light current, general: current which flows
through a device due to irradiation/illumination
IB
IBM
IC
Ica
Base current
Base peak current
Collector current
Collector light current, collector current under
irradiation. Collector current which flows at a
specified illumination/irradiation
Collector dark current, with open base,
collector emitter dark current. For radiant sensitive
devices
with
open
base
and
without
illumination/radiation (E = 0)
Repetitive peak collector current
Mode of operation where the device (e.g. a
transceiver) is fully operational and expecting to
receive a signal for operation e.g in case of a
transceiver waiting to receive an optical input or to
send an optical output as response to an applied
electrical signal.
Radiant intensity (of a source, in a given
direction), quotient of the radiant flux d Φe leaving
the source and propagated in the element of solid
angle dΩ containing the given direction, by the
element of solid angle.
Ie = dΦe/dΩ, unit: W ⋅ sr -1
Note: The radiant intensity Ie of emitters is typically
measured with an angle < 0.01 sr on mechanical
axis or off-axis in the maximum of the irradiation
pattern.
Continuous forward current, the current flowing
through a diode in the forward direction
Average (mean) forward current
Peak forward current
Surge forward current
Short-circuit current, that value of the current
which flows when a photovoltaic cell or a
photodiode is short circuited (RL << Ri ) at its
terminals
DC output current
Photocurrent, that part of the output current of a
photoelectric detector, which is caused by incident
radiation.
Reverse current, leakage current, current which
flows through a reverse biased semiconductor
p-n-junction
Abbreviation for infrared
ICEO
ICM
idle
Ie , I
IF
IFAV
IFM
IFSM
Ik
Io
Iph
IR
IR
Ira
Reverse current under irradiation, reverse light
current which flows due to a specified
irradiation/illumination in a photoelectric device
Ira = Iro + Iph
IrDA®
Infrared Data Association, no profit organization
generating infrared data communication standards
Document Number: 81252
Rev. 1.3, 18-Aug-08
IRED
Iro
Vishay Semiconductors
Infrared emitting diode, solid state device
embodying a p-n junction, emitting infrared
radiation when excited by an electric current. See
also LED: solid state device embodying a p-n
junction, emitting optical radiation when excited by
an electric current.
Reverse dark current, dark current, reverse
current flowing through a photoelectric device in
the absence of irradiation
IRPHY
Version 1.0, SIR IrDA®‚ data communication
specification covering data rates from 2.4 kbit/s
to 115.2 kbit/s and a guaranteed operating range
more than one meter in a cone of ± 15°
IRPHY
Version 1.1, MIR and FIR were implemented in the
IrDA® standard with the version 1.1, replacing
version 1.0
IRPHY
Version 1.2, added the SIR low power standard to
the IrDA® standard, replacing version 1.1. The SIR
low power standard describes a current saving
implementation with reduced range (min. 20 cm to
other low power devices and min. 30 cm to full
range devices).
IRPHY
Version 1.3, extended the low power option to the
higher bit rates of MIR and FIR replacing version 1.2.
IRPHY
Version 1.4, VFIR was added, replacing version 1.3
ISB
Quiescent current
ISD
Supply current in dark ambient
ISH
Iv, I
Supply current in bright ambient
Luminous intensity (of a source, in a given
direction), quotient of the luminous flux dΦv leaving
the source and propagated in the element of solid
angle dΩ containing the given direction, by the
element of solid angle. Ie = dΦv/dΩ, unit: cd ⋅ sr -1
Note: The luminous intensity Iv of emitters is
typically measured with an angle < 0.01 sr on
mechanical axis or off-axis in the maximum of the
irradiation pattern.
luminous efficacy of radiation, quotient of the
luminous flux Φv by the corresponding radiant flux
Φe: K = Φv / Φe, unit: lm ⋅ W-1
Note: When applied to monochromatic radiations,
the maximum value of K(λ) is denoted by the
symbol Km.
Km = 683 lm ⋅ W-1 for νm = 540 x 1012 Hz
(λm ≈ 555 nm) for photopic vision.
K'm = 1700 lm ⋅ W-1 for λ'm ≈ 507 nm for scotopic
vision. For other wavelengths :
K(λ) = Km V(λ) and K'(λ) = K'm V'(λ)
Kelvin, SI unit of thermodynamic temperature, is
the fraction 1/273.15 of the thermodynamic
temperature of the triple point of water
(13th CGPM (1967), Resolution 4). The unit Kelvin
and its symbol K should be used to express an
interval or a difference of temperature.
Note: In addition to the thermodynamic
K
K
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543
Symbols and Terminology
Vishay Semiconductors
Symbols and Terminology
temperature (symbol T), expressed in Kelvins, use
is also made of Celsius temperature (symbol t)
defined by the equation t = T - T0, where
T0 = 273.15 K by definition. To express Celsius
temperature, the unit “degree Celsius”, which is
equal to the unit “Kelvin” is used; in this case,
“degree Celsius” is a special name used in place of
“Kelvin”. An interval or difference of Celsius
temperature can, however, be expressed in
Kelvins as well as in degrees Celsius.
Latency Receiver latency allowance (in ms or µs) is the
maximum time after a node ceases transmitting
before the node’s receiving recovers its specified
sensitivity
LED and IRED
Light Emitting Diode, LED: solid state device
embodying a p-n junction, emitting optical
radiation when excited by an electric current. The
term LED is correct only for visible radiation,
because light is defined as visible radiation (see
Radiation and Light). For infrared emitting diodes
the term IRED is the correct term. Nevertheless it
is common but not correct to use "LED" also for
IREDs.
Radiance (in a given direction, at a given point of
Le; L
a real or imaginary surface).
Quantity defined by the formula
Le
lm
lx
m
Me; M
dΦv
,
dA cos θ dΩ
= ---------------------------------------------------------⋅
⋅
where dΦe is the radiant flux transmitted by an
elementary beam passing through the given point
and propagating in the solid angle dΩ containing
the given direction; dA is the area of a section of
that beam containing the given point; θ is the angle
between the normal to that section and the
direction of the beam, unit: W ⋅ m-2 ⋅ sr -1
Lumen, unit for luminous flux
Lux, unit for illuminance
Meter, SI unit of length
Radiant exitance (at a point of a surface) Quotient of the radiant flux dΦe leaving an element
of the surface containing the point, by the area dA
of that element. Equivalent definition. Integral,
taken over the hemisphere visible from the given
point, of the expression Le ⋅ cosθ ⋅ dΩ, where Le is
the radiance at the given point in the various
directions of the emitted elementary beams of
solid angle dΩ, and θ is the angle between any of
these beams and the normal to the surface at the
given point.
dΦ e
M e = ----------- = ∫ L e ⋅ cos θ ⋅ d Ω
dA
2πsr
MIR
Mode
Electrical input or output port of a transceiver
device to set the receiver bandwidth
N.A.
Numerical Aperture, N.A. = sin α/2
Term used for the characteristic of sensitivity or
intensity angles of fiber optics and objectives
NEP
Ptot
Pv
Noise equivalent power
Total power dissipation
Power dissipation, general
Radiation and Light
Visible radiation, any optical radiation capable of
causing a visual sensation directly.
Note: There are no precise limits for the spectral
range of visible radiation since they depend upon
the amount of radiant power reaching the retina
and the responsivity of the observer. The lower limit
is generally taken between 360 nm and 400 nm
and the upper limit between 760 nm and 830 nm.
Radiation and Light
Optical radiation, electromagnetic radiation at
wavelengths between the region of transition to
X-rays (λ = 1 nm) and the region of transition to
radio waves (λ = 1 mm)
Radiation and Light IR
Infrared radiation, optical radiation for which the
wavelengths are longer than those for visible
radiation.
Note: For infrared radiation, the range between
780 nm and 1 mm is commonly sub-divided into:
IR-A 780 nm to 1400 nm
IR-B 1.4 µm to 3 µm
IR-C 3 µm to 1 mm
Dark resistance
RD
RF
Feedback resistor
Ri
Internal resistance
Ris
Isolation resistance
RL
Load resistance
RS
Serial resistance
Rsh
Shunt resistance, the shunt resistance of a
detector diode is the dynamic resistance of the
diode at zero bias. Typically it is measured at a
voltage of 10 mV forward or reverse, or
peak-to-peak
RthJA
Thermal resistance, junction to ambient
RthJC
Thermal resistance, junction to case
RXD
Electrical data output port of a transceiver device
s
Second, SI-unit of time 1 h = 60 min = 3600 s
S
Absolute sensitivity
Ratio of the output value Y of a radiant-sensitive
device to the input value X of a physical quantity:
S = Y/X, units: e.g. A/lx, A/W, A/(W/m2)
Spectral sensitivity at a wavelength λp
s(λp)
unit: W ⋅ m-2
Medium speed IR, as SIR, with the data rate
576 kbit/s to 1152 kbit/s
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544
For technical questions concerning emitters, contact: [email protected]
For technical questions concerning detectors, contact: [email protected]
Document Number: 81252
Rev. 1.3, 18-Aug-08
Symbols and Terminology
Symbols and Terminology
Absolute spectral sensitivity at a wavelength λ,
the ratio of the output quantity y to the radiant input
quantity x in the range of wavelengths
λ to λ + Δλ
s(λ) = dy(λ)/dx(λ)
E.g., the radiant power Φe(λ) at a specified
wavelength λ falls on the radiationsensitive area of
a detector and generates a photocurrent Iph ⋅ s(λ)
is the ratio between the generated photocurrent
Iph and the radiant power Φe(λ) which falls on the
detector. s(λ) = Iph / Φe(λ), unit: A/W
s(λ)rel
Spectral sensitivity, relative, ratio of the spectral
sensitivity s(λ) at any considered wavelength to
the spectral sensitivity s(λ0) at a certain
wavelength λ0 taken as a reference
s(λ)rel = s(λ)/s(λ0)
s(λ0)
Spectral sensitivity at a reference wavelength λ0
SC
Electrical input port of a transceiver device to set
the receiver sensitivity
SD
Electrical input port of a transceiver device to shut
down the transceiver
Shutdown
Mode of operation where a device is switched to a
sleep mode (shut down) by an external signal or
after a quiescent period keeping some functions
alive to be prepared for a fast transition to
operating mode. Might be in some cases identical
with “standby”
SIR
Serial Infrared, term used by IrDA® to describe
infrared data transmission up to and including
115.2 kbit/s. SIR IrDA® data communication
covers 2.4 kbit/s to 115.2 kbit/s, equivalent to the
basic serial infrared standard introduced with the
physical layer version IrPhy version 1.0
Split power supply
Term for using separated power supplies for
different functions in transceivers. Receiver
circuits need well-controlled supply voltages. IRED
drivers do not need a controlled supply voltage but
need much higher currents. Therefore it safes cost
not to control the IRED current supply and have a
separated supply. For that some modified design
rules have to be taken into account for designing
the ASIC. This is used in nearly all Vishay
transceivers and is described in US-Patent
no. 6,157,476
s(λ)
sr
Steradian (sr), SI unit of solid angle Ω. Solid angle
that, having its vertex at the centre of a sphere,
cuts off an area of the surface of the sphere equal
to that of a square with sides of length equal to the
radius of the sphere. (ISO, 31/1-2.1, 1978)
Example: The unity solid angle, in terms of
geometry, is the angle subtended at the center of
a sphere by an area on its surface numerically
equal to the square of the radius (see figures
below). Other than the figures might suggest, the
Document Number: 81252
Rev. 1.3, 18-Aug-08
Vishay Semiconductors
shape of the area does not matter at all. Any shape
on the surface of the sphere that holds the same
area will define a solid angle of the same size. The
unit of the solid angle is the steradian (sr).
Mathematically, the solid angle is dimensionless,
but for practical reasons, the steradian is
assigned.
Standby
T
T
t
t
Tamb
Tamb
TC
TC
Mode of operation where a device is prepared to
be quickly switched into an idle or operating mode
by an external signal.
Period of time (duration)
Temperature, 0 K = - 273.15 °C, unit: K (Kelvin)
Temperature, °C (degree Celsius). Instead of t
sometimes T is used not to mix up temperature T
with time t
Time
Ambient temperature, if self-heating is
significant: temperature of the surrounding air
below the device, under conditions of thermal
equilibrium. If self-heating is insignificant: air
temperature in the surroundings of the device
Ambient temperature range, as an absolute
maximum rating: the maximum permissible
ambient temperature range
Temperature coefficient, the ratio of the relative
change of an electrical quantity to the change in
temperature (ΔT) which causes it under otherwise
constant operating conditions
Colour temperature (BE), the temperature of a
Planckian radiator whose radiation has the same
chromaticity as that of a given stimulus, unit: K
Note: The reciprocal colour temperature is also
used, unit K-1 (BE).
Tcase
Case temperature, the temperature measured at
a specified point on the case of a semiconductor
device. Unless otherwise stated, this temperature
is given as the temperature of the mounting base
for devices with metal can
td
tf
Delay time
Fall time, the time interval between the upper
specified value and the lower specified value on
the trailing edge of the pulse.
Note: It is common to use a 90 % value of the
signal for the upper specified value and a 10 %
value for the lower specified value.
Junction temperature, the spatial mean value of
the temperature during operation. In the case of
phototransistors, it is mainly the temperature of the
collector junction because its inherent temperature
is the maximum.
Turn-off time, the time interval between the upper
specified value on the trailing edge of the applied
input pulse and the lower specified value an the
trailing edge of the output pulse. toff = td(off) + tf
Tj
toff
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Symbols and Terminology
Vishay Semiconductors
ton
Symbols and Terminology
TXD
Turn-on time, the time interval between the lower
specified value on the trailing edge of the applied
input pulse and the upper specified value an the
trailing edge of the output pulse. ton = td(on) + tf
Pulse duration, the time interval between the
specified value on the leading edge of the pulse
and the specified value an the trailing edge of the
output pulse.
Note: In most cases the specified value is 50 % of
the signal
Input pulse duration
Output pulse duration
Rise time, the time interval between the lower
specified value and the upper specified value on
the trailing edge of the pulse.
Note: It is common to use a 90 % value of the
signal for the upper specified value and a 10 %
value for the lower specified value ts storage time
Storage time
Soldering temperature, maximum allowable
temperature for soldering with a specified distance
from the case and its duration
Storage temperature range, the temperature
range at which the device may be stored or
transported without any applied voltage
Electrical data input port of a transceiver device
V
Volt
tp
tpi
tpo
tr
ts
Tsd
Tstg
V(λ)
Standard luminous efficiency function for
photopic vision (relative human eye sensitivity)
V(λ) , V'(λ)
Spectral
luminous
efficiency
(of
a
monochromatic radiation of wavelength λ); V(λ) for
photopic vision; V'(λ) for scotopic vision).
Ratio of the radiant flux at wavelength λm to that at
wavelength λ such that both radiations produce
equally intense luminous sensations under
specified photometric conditions and λm is chosen
so that the maximum value of this ratio is equal to 1
VBEO
Base emitter voltage, open collector
V(BR)
Breakdown voltage, reverse voltage at which a
small increase in voltage results in a sharp rise of
reverse current. It is given in technical data sheets
for a specified current
V(BR)
CEO Collector emitter breakdown voltage,
open base
V(BR)EBO Emitter base breakdown voltage, open
collector
V(BR)ECO Emitter collector breakdown voltage, open
base
VCBO
Collector-base voltage, open emitter, generally,
reverse biasing is carried out by applying a voltage
to any of two terminals of a transistor in such a way
that one of the junctions operates in reverse
direction, whereas the third terminal (second
junction) is specified separately.
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546
VCC
VCE
VCEO
VCEsat
Vdd
VEBO
VECO
VF
VFIR
Supply voltage (positive)
Collector emitter voltage
Collector emitter voltage, open base (IB = 0)
Collector emitter saturation voltage, the
saturation voltage is the DC voltage between
collector and emitter for specified (saturation)
conditions, i.e., IC and EV (Ee or IB), whereas the
operating point is within the saturation region.
Supply voltage (positive)
Emitter base voltage, open collector
Emitter collector voltage, open base
Forward voltage, the voltage across the diode
terminals which results from the flow of current in
the forward direction
As SIR, data rate 16 Mbit/s
Vlogic
Reference voltage for digital data communication
ports
Vno
Signal-to-noise ratio
VO
ΔVΟ
VOC
Output voltage
Output voltage change (differential output voltage)
Open circuit voltage, the voltage measured
between the photovoltaic cell or photodiode
terminals at a specified irradiance/illuminance
(high impedance voltmeter!)
VOH
Output voltage high
VOL
Output voltage low
Vph
Photovoltage, the voltage generated between the
photovoltaic cell or photodiode terminals due to
irradiation/ illumination
VR
Reverse voltage (of a junction), applied voltage
such that the current flows in the reverse direction
VR
Reverse (breakdown) voltage, the voltage drop
which results from the flow of a defined reverse
current
Supply voltage
VS
Vss
(Most negative) supply voltage (in most cases:
ground)
± ϕ1/2
Angle of half transmission distance
η
Quantum efficiency
θ1/2; ± ϕ = α/2
Half-intensity angle, in a radiation diagram, the
angle within which the radiant (or luminous)
intensity is greater than or equal to half of the
maximum intensity.
Note: IEC 60747-5-1 is using θ1/2. In Vishay
datasheets mostly ± ϕ = α/2 is used
θ1/2; ± ϕ = α/2
Half-sensitivity angle, in a sensitivity diagram,
the angle within which the sensitivity is greater
than or equal to half of the maximum sensitivity.
Note: IEC 60747-5-1 is using θ1/2. In Vishay
datasheets mostly ± ϕ = α/2 is used
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For technical questions concerning detectors, contact: [email protected]
Document Number: 81252
Rev. 1.3, 18-Aug-08
Symbols and Terminology
Symbols and Terminology
Ω
λm
Δλ
Solid
angle,
see
sr,
steradian
for
IEC 60050(845)-definition. The space enclosed by
rays, which emerge from a single point and lead to
all the points of a closed curve. If it is assumed that
the apex of the cone formed in this way is the
center of a sphere with radius r and that the cone
intersects with the surface of the sphere, then the
size of the surface area (A) of the sphere
subtending the cone is a measure of the solid
angle Ω. Ω = A/r2. The full sphere is equivalent to
4πsr. A cone with an angle of α/2 forms a solid
angle of Ω = 2 π(1 - cos α/2) = 4 π sin2 α/4, unit: sr
observer. For photopic vision
dΦ e λ
Φ v = K m ∫∞ -------------- ⋅ V(λ )dλ ,
0 dλ
dΦ e λ
where -------------- is the spectral distribution of the
dλ
λ
λc
Wavelength of the maximum of the spectral
luminous efficiency function V(λ)
Range of spectral bandwidth (50 %), the range
of wavelengths where the spectral sensitivity or
spectral emission remains within 50 % of the
maximum value
radiant flux and V(λ) is the spectral luminous
efficiency, unit : lm, lm: lumen, Km = 683 lm/W:
Note: For the values of Km (photopic vision) and
K'm (scotopic vision), see IEC 60050 (845-01-56).
Wavelength, general
Centroid wavelength, centroid wavelength λc of a
spectral distribution, which is calculated as "centre
of gravity wavelength" according to
λ2
λ2
λ c = ∫ λ ⋅ S x (λ )dλ ⁄ ∫ S x ⋅ (λ )dλ
λ1
λ1
Φe; Φ; P
Φv; Φ;
Vishay Semiconductors
Radiant flux; radiant power, power emitted,
transmitted or received in the form of radiation.
unit: W, W = Watt
Luminous flux, quantity derived from radiant flux
Φe by evaluating the radiation according to its
action upon the CIE standard photometric
λD
λp
Dominant wavelength
Wavelength of peak sensitivity or peak emission
Ω = 4 π sr
α = 65.5°
Ω = 1.0 sr
α = 2 arc cos (1 -/2π)
α = 20.5°
Ω = 0.01 sr
Ω = 0.1 sr
94 8584
α = 6.5°
Fig. 1
Document Number: 81252
Rev. 1.3, 18-Aug-08
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For technical questions concerning detectors, contact: [email protected]
www.vishay.com
547
Symbols and Terminology
Vishay Semiconductors
Symbols and Terminology
DEFINITIONS
Databook Nomenclature
(Ideal observer having a relative spectral responsivity curve
that conforms to the V(λ) function for photopic vision or to the
V'(λ) function for scotopic vision, and that complies with the
summation law implied in the definition of luminous flux).
Note: With a given spectral distribution of a radiometric
quantity the equivalent photometric quantity can be
evaluated. However, from photometric units without knowing
the radiometric spectral distribution in general one cannot
recover the radiometric quantities.
The nomenclature, symbols, abbreviations and terms inside
the Vishay Semiconductors data book is based on ISO and
IEC standards.
The special optoelectronic terms and definitions are referring
to the IEC Multilingual Dictionary (Electricity, Electronics and
Telecommunications), Fourth edition (2001-01), IEC 50
(Now: IEC 60050). The references are taken from the current
editions of IEC 60050 (845), IEC 60747-5-1 and
IEC 60747-5-2. Measurement conditions are based on IEC
and other international standards and especially guided by
IEC 60747-5-3.
Editorial notes: Due to typographical limitations variables
cannot be printed in an italics format, which is usually
mandatory. Our booklet in general is using American
spelling. International standards are written in UK English.
Definitions are copied without changes from the original text.
Therefore these may contain British spelling.
Radiometric Terms, Quantities and Units
The radiometric terms are used to describe the quantities of
optical radiation.
The relevant radiometric units are:
TABLE 1 - RADIOMETRIC QUANTITIES
AND UNITS
Radiant and Luminous Quantities and Their Units
These two kinds of quantities have the same basic symbols,
identified respectively, where necessary, by the subscript
e (energy) or v (visual), e.g. Φe, Φv. See note.
Note: Photopic and scotopic quantities. Luminous
(photometric) quantities are of two kinds, those used for
photopic vision and those used for scotopic vision. The
wording of the definitions in the two cases being almost
identical, a single definition is generally sufficient with the
appropriate adjective, photopic or scotopic added where
necessary.
The symbols for scotopic quantities are prime (Φ'v, I'v, etc),
but the units are the same in both cases.
In general, optical radiation is measured in radiometric units.
Luminous (photometric) units are used when optical
radiation is weighted by the sensitivity of the human eye,
correctly spoken, by the CIE standard photometric observer
RADIOMETRIC
TERM
SYMBOL
UNIT
REFERENCE
Radiant power,
radiant flux
Φe
W
IEC 50
(845-01-24)
Radiant intensity
Ie
W/sr
IEC 50
(845-01-30)
Irradiance
Ee
W/m2
IEC 50
(845-01-37)
Radiant exitance
Me
W/m2
IEC 50
(845-01-47)
Radiance
Le
W/(sr ⋅ m2)
IEC 50
(845-01-34)
Photometric Terms, Quantities and Units
The photometric terms are used to describe the quantities of
optical radiation in the wavelength range of visible radiation
(generally assumed as the range from 380 nm to 780 nm).
The relevant photometric terms are:
TABLE 2 - PHOTOMETRIC QUANTITIES AND UNITS
PHOTOMETRIC TERM
EQUIVALENT
RADIOMETRIC TERM
SYMBOL
UNIT
Luminous power
or
luminous flux
Radiant power
or
radiant flux Φe
Φv
lm
Luminous intensity
Radiant intensity Ie
Iv
lm/sr = cd
Iv: IEC 50 (845-01-31)
cd: IEC 50 (845-01-50)
Illuminance
Irradiance Ee
Ev
lm/m2 = lx (lux)
Ev: IEC 50 (845-01-38)
lx: IEC 50 (845-01-52)
Luminous exitance
Radiant exitance Me
Mv
lm/m2
IEC 50 (845-01-48)
Luminance
Radiance Le
Lv
cd/m2
IEC 50 (845-01-35)
Photometric units are derived from the radiometric units by
weighting them with a wavelength dependent standardized
human eye sensitivity V(λ) - function, the so-called
CIE-standard photometric observer. There are different
functions for photopic vision (V(λ)) and scotopic vision (V'(λ) ).
www.vishay.com
548
REFERENCE
Φv: IEC 50 (845-01-25)
lm: IEC 50 (845-01-51)
In the following is shown, how the luminous flux is derived
from the radiant power and its spectral distribution. The
equivalent other photometric terms can be derived from the
radiometric terms in the same way.
For technical questions concerning emitters, contact: [email protected]
For technical questions concerning detectors, contact: [email protected]
Document Number: 81252
Rev. 1.3, 18-Aug-08
Symbols and Terminology
Symbols and Terminology
Vishay Semiconductors
Relation between distance r, irradiance (illuminance) Ee
(EV) and intensity Ie (IV)
The relation between intensity of a source and the resulting
irradiance in the distance r is given by the basic square root
rule law.
An emitted intensity Ie generates in a distance r the
irradiance Ee = Ie/r2.
This relationship is not valid under near field conditions and
should be used not below a distance d smaller than 5 times
the emitter source diameter.
9 m2
4
m2
1 m2
1m
2m
18145
3m
Fig. 2
Using a single radiation point source, one gets the following
relation between the parameter Ee, Φe, r:
dΦ e W
E e = ----------- ------dA m 2
use
dΦ
A
I e = -------- , Ω = ---- and get
2
dΩ
r
dΦ e
I W
dΩ
E e = ----------- = I e -------- = ----e ------2
2
dA
dA
r m
Examples
1.Calculate the irradiance with given intensity and distance r:
Transceivers with specified intensity of Ie = 100 mW/sr will
generate in a distance of 1m an irradiance of
Ee = 100/12 = 100 mW/m2. In a distance of 10 m the
irradiance would be Ee = 100/102 = 1 mW/m2.
2.Calculate the range of a system with given intensity and
irradiance threshold. When the receiver is specified with a
sensitivity threshold irradiance Ee = 20 mW/m2, the
transmitter with an intensity Ie = 120 mW/sr the resulting
range can be calculated as
r =
Ie
-----=
Ee
120
---------- =
20
Document Number: 81252
Rev. 1.3, 18-Aug-08
6 = 2 . 45 m
For technical questions concerning emitters, contact: [email protected]
For technical questions concerning detectors, contact: [email protected]
www.vishay.com
549