These Optical Sensors provide a compact,
low-cost method to detect workpieces. Many models are available, including
Slot-type Sensors (through-beam) for non-modulated or modulated light,
Reflective Sensors, and Sensors with separate emitters and receivers.
What are Photomicrosensors?
A Photomicrosensor is a small photoelectric sensor with an amplifier built
into it that is used primarily as a component for building into equipment.
Like any ordinary photoelectric sensor with a built-in amplifier, it is
used, for example, in applications to detect passing objects or in
positioning applications. The sensing object is most often a piece of
metal called a "dog". When the dog enters the sensing area, it is
optically detected by the Photomicrosensor, which outputs a signal.
Features of Photomicrosensors
Photomicrosensors have the following advantages over ordinary
photoelectric sensors with built-in amplifiers:
(1) Many Different Shapes in One Model Series
The EE-SX67 Series, for example, has models with eight different slot
configurations, allowing the customer to choose the best configuration for
the installation position.
(2) Low Price
Ratings and performances are limited to those required for building into
equipment, and the required IP degree of protection is easier to achieve,
making prices very reasonable.
(3) Downsizing Is Possible with the Sensing
Distances Required for Building into Equipment
The standard sensing distances (slot width) are specifically intended to
be used for building into equipment. Slot-type Sensors, for example, have
a 3.6 mm or 5 mm sensing distance. Diffuse-reflective and Limited
Reflective Sensors have a sensing distance of less than 5 mm, and
retro-reflective and Through-beam Sensors, less than 1 m.
(4) Indicator Lighting Mode
The indicator on many Photomicrosensors lights when light is incident.
Some Photomicrosensors have specific models on which the indicator lights
when light is interrupted. When lighting the indicator for position
adjustment applications of Slot-type Sensors, for example, it may be more
convenient to use a model that lights the indicator when light is
interrupted. When using the indicator to check the power supply status, on
the other hand, it may be convenient to use a model that lights the
indicator when light is incident.
(5) Other Specifications: Degree of Protection and
Output Current
A waterproof structure is not required because it is assumed the
Photomicrosensors will be built into other equipment, and the output
current rating can be kept low. Also, most models can operate on a 5-VDC
power supply.
Operating Principles
(1) Many Different Shapes in One Model Series
When light travels through air or water, it always travels in a straight
line. The slit on the outside of a Through-beam Sensor that is used to
detect small objects is an example of how this principle is applied to
practical use.
Refraction
Refraction is the phenomenon of light being deflected as it passes
obliquely through the boundary between two media with different refractive
indices.
Reflection (Regular Reflection, Retro-reflection,
and Diffuse Reflection)
A flat surface, such as glass or a mirror, reflects light at an angle
equal to the incident angle of the light. This kind of reflection is
called regular reflection. Retro-reflectors (also called a corner cube)
take advantage of this principle by arranging three flat surfaces
perpendicular to each other. "Retro" means "to return toward the source."
The light reflected off the reflectors travels back towards the emitter,
thus the term retro-reflective".
Matte surfaces, such as white paper, reflect light in all directions. This
scattering of light is called diffuse reflection. This principle is the
sensing method used by Diffuse-reflective Sensors.
(2) Light Sources
Light Generation
<Non-modulated Light>
Non-modulated light facilitates high-speed response by continuously
radiating a constant amount of light. There is the drawback, however, of
susceptibility to external light interference.
<Modulated Light>
Modulated light is not affected by sunlight, light from incandescent
bulbs, and other external light interference. An LED emitter is
pulse-lighted, and the received signal is processed to remove the DC
component.
Classifications
1. Classification by Sensing
Method
(1) Slot Sensors
Slot Sensors are suitable for applications
using a thin sensing object, or "dog," that require a highly precise
sensing position. Setup is easy because no optical axis adjustment is
needed. There are many product variations. The necessary configuration,
connection method, and other items can be selected from a wide array of
models.
(2) Through-beam Sensors
Through-beam Sensors are suitable for
applications that require relatively long sensing distances.
(3) Retroreflective Sensors
Retroreflective Sensors are suitable for
applications that require relatively long sensing distances. They have the
advantage of requiring less work for wiring and optical axis adjustment
when compared to Through-beam Sensors.
(4) Diffuse-reflective Sensors
Diffuse-reflective Sensors are suitable for
applications where the sensing object is thick and won't fit into the slot
of a Slot Sensor.
(5) Limited-reflective Sensors
Limited-reflective Sensors are basically the
same as Diffuse-reflective Sensors, but they are suitable when background
objects are present. (With Diffuse-reflective Sensors, the presence of a
background object with a higher reflectivity than the sensing object
(e.g., metals with mirror finishing) may cause sensing instability.)
2. Considerations when Choosing a Sensing Method
(1) Slot Sensors
-
Shape, slot width, connection
(pre-wired/connector)
-
Presence or absence of external light
interference (non-modulated light/modulated light)
-
Output configuration (Light-ON/Dark-ON,
NPN/PNP)
-
Indicator (Light-ON/Dark-ON)
(2) Through-beam Sensors
-
Shape (built-in Amplifier, optical fiber),
sensing distance
-
Output configuration (Light-ON/Dark-ON)
(3) Retroreflective Sensors
(4)
Diffusive/Limited-reflective Sensors
-
Shape (built-in Amplifier, optical fiber),
sensing distance
-
Presence or absence of background objects
(Diffuse-reflective/Limited-reflective Sensors)
-
External light interference (non-modulated
light/modulated light)
-
Output configuration (Light-ON/Dark-ON)
Interpreting Engineering Data
Sensing Position Characteristics
Sample Characteristics for the EE-SX770
Indicates whether or not the Sensor responds with respect to sensing
object edge position.
Repeated Sensing Position Characteristics
Sample Characteristics for the EE-SX770
Indicates the discrepancy in the edge position of the sensing object when
the Sensor responds.
It serves as a guide for the positioning accuracy of the sensing object.
Receiver Output Excess Gain Vs. Sensing Distance
Characteristics
Sample Characteristics for the
EE-SPW311/411
-
Values shown are for the receiver output
excess gain when the sensitivity is set to the maximum value.
-
The above example is for models with a
rated sensing distance of 1m. The receiver output excess gain can be
thought of as being approximately 10 times the rated sensing distance.
Parallel Movement Characteristics
Sample Characteristics for the
EE-SPW311/411
-
Through-beam
Sensors:
Indicates the receiver's sensing limit position when the emitter
position is fixed.
-
Retroreflective
Sensor:
Indicates the sensing limit position of the Retro-reflector when the
Sensor position is fixed.
-
When setting up multiple Through-beam
Sensors, 1.5 times the area shown is necessary to prevent mutual
interference.
Operating Range Characteristics
Sample Characteristics for the EE-SPY301
and EE-SPY401
Note: These values apply to the standard
sensing object. If the sensing object changes, the operating range
and sensing distances also change.
Photomicro Sensor Definition of Terms
Non-modulated light
Method used to detect light steadily emitted
by the emitter element.
Sensing Distance
Through-beam Sensors (with
slot)
The slot width, i.e., the distance between
the opposing faces of the emitter and receiver, is the sensing distance.
Through-beam Sensors / Retroreflective Sensors
The minimum distance that can be set
considering factors such as the variation between products and
fluctuations in temperature.
Note: The actual value under standard
conditions for each method is longer than the rated sensing distance.
Diffuse-reflective Sensors / Limited-reflective
Sensors
The minimum distance that can be set for a
standard sensing object (white paper) considering factors such as the
variation between products and fluctuations in temperature.
Note: The actual value under standard
conditions for each method is longer than the rated sensing distance.
Differential distance
The difference in distance between the
operating point and releasing point.
Response frequency
The frequency at which an object satisfying
specified conditions (size, transparency rate, reflection factor, sensing
distance, and power supply voltage) can be repeatedly detected.
Response time
The delay from the light input turning
ON/OFF until the control output operation or release operation. The
following equation generally applies. Operating time (Ton) ≈ Releasing
time (Toff)
Ambient illumination
The level of illumination on the sensing
surface that enables stable operation of the Sensor.
Recommended Products
|
Slot-type
Photomicrosensor (Non-modulated)
EE-SX47 /
EE-SX67
Photomicrosensor with 50- to 100-mA
direct switching capacity for built-in application. |
|
Compact Pre-wired
Photomicro Sensor with Amplifier (Non-Modulated)
EE-SX91
Meeting customer needs with compact
Sensors that mount with M3 screws. |
|
Retroreflective
Photomicrosensor with Lens
EE-SPZ-A
Photomicrosensor with light modulation
for reduced external light interference. |
| 
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