光电传感器(中英文对照版)

Photoelectric sensor

Key word:

photoelectric effect photoelectric element photoelectric sensor

classification sensor application characteristics

.

Abstract:

in the rapid development of science and technology in the modern

society, mankind has into the rapidly changing information era, people in daily

life, the production process, rely mainly on the detection of information

technology by acquiring, screening and transmission, to achieve the brake

control, automatic adjustment, at present our country has put detection

techniques listed in one of the priority to the development of science and

technology. Because of microelectronics technology, photoelectric

semiconductor technology, optical fiber technology and grating technical

development makes the application of the photoelectric sensor is growing. The

sensor has simple structure, non-contact, high reliability, high precision,

measurable parameters and quick response and more simple structure, form etc,

and flexible in automatic detection technology, it has been widely applied in

photoelectric effect as the theoretical basis, the device by photoelectric material

composition.

Text:

First, theoretical foundation - photoelectric effect

Photoelectric effect generally have the photoelectric effect, optical effect, light

born volts effect.

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The light shines in photoelectric material, according to the electronic absorption

material surface energy, if absorbed energy large enough electronic electronic

will overcome bound from material surface and enter the outside space, which

changes photoelectron materials, this kind of phenomenon become the

conductivity of the photoelectric effect

According to Einstein's photoelectron effect, photon is moving particles, each

photon energy for hv (v for light frequency, h for Planck's constant, h = 6.63 *

10-34 J/HZ), thus different frequency of photons have different energy, light, the

higher the frequency, the photon energy is bigger. Assuming all the energy

photons to photons, electronic energy will increase, increased energy part of the

fetter, positive ions used to overcome another part of converted into electronic

energy. According to the law of conservation of energy:

Type, m for electronic quality, v for electronic escaping the velocity, A

microelectronics the work done.

From the type that will make the optoelectronic cathode surface escape the

necessary conditions are h > A. Due to the different materials have different

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2

escaping, so reactive to each kind of cathode materials, incident light has a

certain frequency is restricted, when the frequency of incident light under this

frequency limit, no matter how the light intensity, won't produce photoelectron

launch, this frequency limit called

2

m

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h

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-

A

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type, c for the speed of light, A reactive for escaping.

When is the sun, its electronic energy, absorb the resistivity reduce conductive

phenomenon called optical effects. It belongs to the photoelectric effect within.

When light is, if in semiconductor electronic energy big with semiconductor of

forbidden band width, the electronic energy from the valence band jump into the

conduction band, form, and at the same time, the valence band electronic left

the corresponding cavities. Electronics, cavitation remained in semiconductor,

and participate in electric conductive outside formed under the current role.

In addition to metal outer, most insulators and semiconductor have photoelectric

effect, particularly remarkable, semiconductor optical effect according to the

optoelectronics manufacturing incident light inherent frequency, when light

resistance in light, its conductivity increases, resistance drops. The light intensity

is strong, its value, if the smaller, its resistance to stop light back to the original

value.

Semiconductor produced by light illuminate the phenomenon is called light emf,

born volts effect on the effect of photoelectric devices have made si-based ones,

photoelectric diode, control thyristor and optical couplers, etc.

Second, optoelectronic components and characteristics

According to the outside optoelectronics manufacturing optoelectronic devices

have photoelectron, inflatable phototubes and photoelectric times once tube.

1. Phototubes phototubes are various and typical products are vacuum

phototubes and inflatable phototubes, light its appearance and structure as

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shown in figure 1 shows, made of cylindrical metal half cathodic K and is located

in the wires cathodic axis of anode in A package of smoke into the vacuum, when

incident light within glass shell in the cathode, illuminate A single photon took all

of its energy transfer to the cathode materials A free electrons, so as to make the

freedom electronic energy increase h. When electrons gain energy more than

escape of cathode materials, it reactive A metal surface constraints can overcome

escape, form electron emission. This kind of electronic called optoelectronics,

optoelectronic escaping the metal surface for after initial kinetic energy

Phototubes normal work, anode potential than the cathode, shown in figure 2. In

one shot more than

optoelectronic cathode surface by positive potential attracted the anode in

photoelectric tube forming space, called the current stream. Then if light intensity

increases, the number of photons bombarded the cathode multiplied, unit of

time to launch photoelectron number are also increasing, photo-current

greatens. In figure 2 shows circuit, current and resistance is the voltage drop

across the only a function of light intensity relations, so as to achieve a

photoelectric conversion. When the LTT optoelectronic cathode K, electronic

escape from the cathode surface, and was the photoelectric anode is an electric

current, power plants absorb deoxidization device in the load resistance - I, the

voltage

Phototubes photoelectric characteristics fig.03 shows, from the graph in flux

knowable, not too big, photoelectric basic characteristics is a straight line.

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2. Photoelectric times had the sensitivity of vacuum tube due to low, so with

people developed has magnified the photomultiplier tubes photo-current ability.

Figure 4 is photomultiplier tube structure schematic drawing.

图

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光电倍 增结构示意图

From the graph can see photomultiplier tubes also have A cathode K and an

anode A, and phototubes different is in its between anode and cathode set up

several secondary emission electrodes, D1, D2 and D3... They called the first

multiply electrode, the second multiply electrode,... Usually, double electrode for

10 ~ 15 levels. Photomultiplier tubes work between adjacent electrode, keeping

a certain minimum, including the cathode potential potentials, each multiply

electrode potential filtering increases, the anode potential supreme. When the

incident light irradiation, cathodic K escape from the optoelectronic cathode

multiplied by first accelerated, by high speed electrode D1 bombarded caused

secondary electron emission, D1, an incident can generate multiple secondary

electron photonics, D1 emit of secondary electron was D1, D2 asked electric field

acceleration, converged on D2 and again produce secondary electron emission...

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So gradually produce secondary electron emission, make electronic increased

rapidly, these electronic finally arrived at the anode, form a larger anode current.

If a n level, multiply electrodes at all levels for sigma, the multiplication of rate is

the multiplication of photomultiplier tubes can be considered sigma n rate,

therefore, photomultiplier tube has high sensitivity. In the output current is less

than 1mA circumstances, it in a very wide photoelectric properties within the

scope of the linear relationship with good. Photomultiplier tubes this

characteristic, make it more for light measurement.

3 and photoconductive resistance photoconductive resistance within the working

principle is based on the photoelectric effect. In semiconductor photosensitive

material ends of mount electrode lead, it contains transparent window sealed in

the tube and shell element photoconductive resistance. Photoconductive

resistance properties and parameters are:

1) dark resistance photoconductive resistance at room temperature, total dark

conditions stable resistance called dark resistance, at the current flow resistance

is called dark current.

2) light resistance photoconductive resistance at room temperature and certain

lighting conditions stable resistance measured, right now is called light resistance

of current flow resistance is called light current.

4, volt-ampere characteristics of both ends photoconductive resistance added

voltage and current flows through photoconductive resistance of the relationship

between called volt-ampere characteristics shown, as shown in figure 5. From the

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graph, the approximate linear volt- ampere characteristics that use should be

limited, but when the voltage ends photoconductive resistance, lest than shown

dotted lines of power consumption area

5, photoelectric characteristics photoconductive resistance between the poles,

light when voltage fixed the relationship between with bright current

photoelectric characteristics. Called Photoconductive resistance photoelectric

characteristics is nonlinear, this is one of the major drawback of photoconductive

resistance.

6, spectral characteristics is not the same incident wavelength, the sensitivity of

photoconductive resistance is different also. Incidence wavelength and

photodetector the relationship between relative sensitivity called spectral

characteristics. When used according to the wavelength range by metering,

choose different material photoconductive resistance.

7, response time by photoconductive resistance after photo-current need light,

over a period of time (time) rise to reach its steady value. Similarly, in stop light

photo-current also need, over a period of time (down time) to restore the its

dark current, this is photoconductive resistance delay characteristics.

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Photoconductive resistance rise response time and falling response time about

10-1 ~ 10-3s, namely the frequency response is 10Hz ~ 1000Hz, visible

photoconductive resistance cannot be used in demand quick response occasion,

this is one of the main photoconductive resistance shortcomings.

8 and temperature characteristic photoconductive resistance by temperature

affects greatly, temperature rise, dark current increase, reduced sensitivity, which

is another photoconductive resistance shortcomings.

9, frequency characteristic frequency characteristics refers to an external voltage

and incident light, strong must be photo-current I and incident light modulation

frequency, the relationship between the f, photoelectric diode is the frequency

characteristic of the photoelectric triode frequency characteristics, this is because

of the photoelectric triode shot

base-combed need time's sake. By using the principle of the photoelectric

efficiency of optoelectronics manufacturing frequency characteristics of the worst,

this is due to capture charge carriers and release charge need a certain time's

sake.

Three, photoelectric sensors

Photoelectric sensor is through the light intensity changes into electrical signal

changes to achieve control, its basic structure, it first figure 6 by measuring the

change of change of converting the light signal, and then using photoelectric

element further will light signals into electrical signal by photoelectric sensor

general. Illuminant, optical path and optoelectronics. Three components of

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photoelectric detection method has high precision, fast response, non- contact

wait for an advantage, but measurable parameters of simple structure, sensors,

form flexible, therefore, photoelectric sensor in the test and control is widely

used.

By photoelectric sensor generally is composed of three parts, they are divided

into: transmitter and receiver and detection circuit shown, as shown in figure 7,

transmitter aimed at the target launch beam, the launch of the beam from

semiconductor illuminant, general light emitting diode (LED), laser diode and

infrared emission diode. Beam uninterrupted launch, or change the pulse width.

Receivers have photoelectric diode, photoelectric triode, composed si-based

ones. In front of the receiver, equipped with optical components such as lens and

aperture, etc. In its back is detection circuit, it can filter out effective signal and

the application of the signal. In addition, the structural components in

photoelectric switch and launch plate and optical fiber, triangle reflex plate is

solid structure launch device. It consists of small triangle cone of reflective

materials, can make a beam accurately reflected back from plate, with practical

significance. It can be in with the scope of optical axis 0 to 25, make beams

change launch Angle from a root almost after launch line, passes reflection or

from the rotating basic returns.

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Photoelectric sensor is a kind of depend on is analyte and optoelectronics and

light source, to achieve the relationship between the measured purpose, so the

light source photoelectric sensor plays a very important role, photoelectric

sensor power if a constant source, power is very important for design, the

stability of the stability of power directly affect the accuracy of measurement,

commonly used illuminant have the following kinds:

1, leds is a change electric energy into light energy semiconductor devices. It has

small volume, low power consumption, long life, fast response, the advantages of

high mechanical strength, and can match and integrated circuits. Therefore,

widely used in computer, instruments and automatic control equipment.

2, silk light bulb that is one of the most commonly used illuminant, it has rich

infrared light. If chosen optoelectronics, constitutes of infrared sensor sensitive

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colour filter can be added to the visible tungsten lamps, but only filter with its

infrared does illuminant, such, which can effectively prevent other light

interference.

3, compared with ordinary light laser laser with energy concentration, directional

good, frequency pure, coherence as well as good, is very ideal light sources.

The light source, optical path and photoelectric device composition photoelectric

sensor used in photoelectric detection, still must be equipped with appropriate

measurement circuit. The photoelectric effect to the measurement circuit of

photoelectric element of widerange caused changes needed to convert the

voltage or current. Different photoelectric element, the measurement circuit

required is not identical also. Several semiconductor introduces below

optoelectronic devices commonly used measurement circuit.

Semiconductor photoconductive resistance can through large current, be in so

usually, need not equipped with amplifier. In the output power of demand is

bigger, can use figure 8 shows circuit.

Figure 9 (a) with temperature compensation given the photosensitive diode

bridge type measuring circuit. When the incident light intensity slow change, the

reverse resistance photosensitive diode is the slow change, the change of the

temperature will cause the bridge output voltage, must compensate. Drift Picture

a photosensitive diode as the test components, another into Windows, in

neighboring bridge, the change of the temperature in the arms of the influence

of two photosensitive diode, therefore, can eliminate the same output with

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temperature bridge road drift.

Light activated triode incident light in work under low illumination, or hope to get

bigger output power, also can match with amplifying circuit, as shown in figure 9

shows.

Because even in the glare photosensitive batteries, maximum output voltage also

only 0.6 V, still cannot make the next level 1 transistor have larger current output,

so must add positive bias, as shown in figure 9 (a) below. In order to reduce the

transistor circuit impedance variations, base si-based ones to reduce as much as

possible without light, when the reverse bias inherit in parallel a resistor si- based

ones at both ends. Or like figure 9 (b) as shown by the positive ge diode

produces pressure drop and test the voltage produced when exposed to light,

make silicon tube e stack, b the voltage between actuators than 0.7 V, and

conduction work. This kind of circumstance also can use silicon light batteries, as

shown in figure 10 (c) below.

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Semiconductor photoelectric element of photoelectric circuit can also use

integrated operational amplifier. Silicon photosensitive diode can be obtained by

integrating op-amp larger output amplitude, as shown in figure 11 (a) below.

When light is produced, the optical output voltage in order to guarantee

photosensitive diode is reverse biased, in its positive to add a load voltage.

Figure 11. (b) give the photocell transform circuit, because the photoelectric

si-based ones short-circuit current and illumination of a linear relationship

between, so will it up in the op-amp is, inverse-phase input, using these two

potential difference between the characteristics of close to zero, can get better

effect. In the picture shows conditions, the output voltage

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The photoelectric element by flux the role of different made from the principle of

optical measurement and control system is varied, press the photoelectric

element (optical measurement and control system) output nature, namely, can

be divided into second analog photoelectric sensor and pulse (switch)

photoelectric sensor. Analog photoelectric sensors will be converted into

continuous variation of the measure, it is measured optical with a single value

relations between analog photoelectric sensor. According to be measured

(objects) method detection of target can be divided into transmission

(absorption) type, diffuse type, shading type (beam resistance gears) three

categories. So-called transmission style means the object to be tested in optical

path in constant light source, the light energy through things, part of being

measured by absorption, transmitted light onto photoelectric element, such as

measured liquid, gas transparency and photoelectric BiSeJi etc; ying

The so- called diffuse style means the constant light by the light onto the analyte

from the object to be tested, and projected onto surfaces reflect on after

optoelectronic devices, such as photoelectric colorimetric thermometer and light

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gauge etc; The so-called shading style means the when illuminant issued by the

flux of light analyte covered by a part Jing optoelectronics, make projection on

the flux change, change the object to be tested and extent of the position with

the light path, such as vibration measurement, the size measurement; And in

pulse photoelectric sensor in the sensors, photoelectric element acceptable

optical signal is intermittent change, therefore photoelectric element in switch

work of the state, the current output it is usually only two steady state of the

signal, the pulse form used for photoelectric counting and photoelectric speed

measurement and so on.

And infrared photoelectric sensor classification and working way generally have

the following kinds:

1, groove photoelectric sensor put a light emitter and a receiver in a slot

face-to-face outfit are on opposite sides of the photoelectric groove. Lighter

emits infrared light or visible light, and in unimpeded cases light receptors can

receive light. But when tested objects from slot zhongtong obsolete, light

occluded, photoelectric switches and action. Output a switch control signal, cut

off or connect load current, thus completing a control movement. Groove switch

is the overall of detection distance because general structure limits only a few

centimeters.

2, DuiShe type optoelectronic sensor if you put lighter and receive light is

separated, can make the detection distance increase. By a lighter and an inbox

light sensor into a photoelectric switch is called DuiShe separate photoelectric

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switches, referred to DuiShe photoelectric switch. Its detection distance can reach

a few meters and even a dozen meters. When using light-emitting device and

receive light device are installed in test object through the path of the sides, test

object by blocking light path, accept light implement action output a switch

control signals.

3, reflex photoelectric switch light- emitting device type and receive light

device into the same device inside, in its front pack a reflex using the

reflection principle of complete photoelectric control function is called reflex

reflex (or reflector reflex) photoelectric switch. Under normal

circumstances, lighter the light reflected by reflex is received by accept

light; Once the light path be test object to block, accept light, the light is not

receive photoelectric switch is action, output a switch control signals.

4, diffusion reflective photoelectric switches its detection head with a lighter and

also an inbox light ware, but no reflex ahead. Normally lighter for the light

collect light is not found. When test object by blocking the light, and the light

reflected light, receive part implement received light signals, output a switch

signals.

Four, I'm the idea of photoelectric sensor

With the development of science and technology people on measuring accuracy

had the higher request, this has prompted the pace with The Times photoelectric

sensor have updated, improve the main means photoelectric sensor

performance is the application of new materials, new technology manufacturing

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