The photo sensor adopts the light cell as the sensor of the detector.
It, at first converted to the change of optical signal by the metric
change, then further convert the optical signal to the electric signal
through the light cell. The photo-sensor is generally made up of light
source, optical thorough fare and part of light cell three.
The photoelectric detecting means has advantages such as precision high,
reacting fast, non-contact,etc., and there is many measurable
parameter, the sensor is simple in construction, the form is flexible,
so, it is very extensive that the optoelectronic type sensor is employed
in measuring and controlling.
The photo-sensor realizes the key component of photo-electricity
translation in various photoelectric detection systems, it is an optical
signal ‘ Infrared, can be seen and ultraviolet ray radiation) Change
into the device of the electric signal.
The optoelectronic type sensor regards photoelectric device as the
sensor of the transition element. It can be used for measuring the non
electrical quantity causing the light quantity to change directly, such
as light intensity, illuminance, radiating temperature measurement, gas
constituent analysis,etc.; Can also use and measure and can convert to
the other non electrical quantities that the light quantity changes,
such as part diameter, surface roughness, meets an emergency, the
displacement, vibration, speed, acceleration, and the shape of object,
recognition of working condition,etc.. The optoelectronic type sensor
has characteristics such as non-contact, reliable performance fast in
response,etc., employed in industry automated assembly and machine
philtrum extensively. In recent years, the new photoelectric device is
emerging constantly, especially the birth of CCD image sensor, the
further application that it is the photo-sensor opened chapter of
innovation.
Germany IFM exchanges the door photo-sensor principle of the good fortune
It is varied for action principle [1 ] of the light cell to observe and
control the system with optics made by the luminous flux, press the
light cell ‘ Optics observes and controls the system) Output quantity
properties can be divided class IIly, namely analog photo-sensors and
pulses (switch) Type photo-sensor. The analog photo-sensor changes
measurand the photo-sensor to become light current of continuous change,
it and measurand one is single value relations. The analog photo-sensor
presses measurand ‘ Measure the goal object) The method can be divided
into transmission ‘ Absorb) The type, it is reflecting type to overflow,
lightproof type (light beam hinders the shelf) Three big classes. The
so-called transmission type means the testee is put in the light path,
the mere energy that the permanent light source gives out crosses the
tested subject, after being absorbed partly, the transmitted light
throws on the light cell;
Overflow reflecting type to refer to light that permanent light source
send out throw at the tested subject while being so-called, and then
throw on the light cell after the body surface examined is reflected;
The luminous flux that the so-called lightproof type refers to sending
out in the light source is only hidden a part among them by the tested
subject, make the luminous flux thrown on Jing’s light cell change,
intensity and testee changed have something to do with the position of
light path.
The light sensitive diode is the most common photosensor. Like general
diode, but there is one that inlays the vitreous window on its case in
the appearance of the light sensitive diode, so that the light kicks
into, accumulated by the grain side in order to increase, the area of
the PN junction is made relatively largely, the light sensitive diode
works under the back-biased working condition, and connect with the load
resistance in series, when there is no illuminationing, it, like
general-purpose diode, the reverse current is very small (< micro;
A),Called the dark current of the light sensitive diode; When there is
illuminationing, current carrier is stimulated, produce the
electron-hole, is called the photoelectricity
Germany IFM exchanges door photo-sensor current carrier of good fortune.
Under the function of the external electric field, photoelectric
current carrier is joined in the electric conduction, form the reverse
current much more largely than the dark current, this reverse current is
called the light current. The magnitude of the light current is
proportional to illumination intensity, then can get the electric signal
varying with illumination intensity on the load resistance.
The phototransistor is except that having light sensitive diodes can
convert the optical signal to the function of the electric signal, and
to the amplifying function of the electric signal. The appearance of the
photosensitive triode is pretty much the same as the general triode,
the general phototransistor only draws two extremely –Emitter and
collecting electrode, the base electrode does not draw, the same
windowing of the case, so that the light kicks into. In order to
increase the illumination, the area of base region is made very largely,
the emitter region is minor, the incident light is mainly absorbed by
the base region. The reversal of biasing of the collector junction while
working, the emitter junction is forward bias. The electric current
that the tube flows through is the dark current Iceo while there is no
illumination =( 1
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