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Technical Explanation for Photomicrosensors
CSM_Photomicro_TG_E_4_2
Introduction
Sensors
What Is a Photomicrosensor?
Switches
A Photomicrosensor is a small photoelectronic 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
Relays
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.
Control Components
Automation Systems
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
Retroreflective and Through-beam Sensors, less than 1 m.
Safety Components
Photomicrosensors have the following advantages over ordinary photoelectric sensors with built-in amplifiers
4. Indicator Lighting Mode
1. Many Different Shapes in One Model Series
The indicator on many Photomicrosensors lights when light
The EE-SX67 Series, for example, has models with eight
is incident. Some Photomicrosensors have specific models
different slot configurations, allowing the customer to
on which the indicator lights when light is interrupted. When
choose the best configuration for the installation position.
lighting the indicator for position adjustment applications of
2. Low Price
Slot-type Sensors, for example, it may be more convenient
Ratings and performances are limited to those required for
to use a model that lights the indicator when light is
building into equipment, and the required IP degree of
interrupted. When using the indicator to check the power
protection is easier to achieve, making prices very
supply status, on the other hand, it may be convenient to
reasonable.
use a model that lights the indicator when light is incident.
Operating Principles
(Glass)
Refractive index: 1.5
(Air)
Refractive index: 1
(Mirror)
Regular Reflection
(Mirror)
Retroreflection
(Paper)
Others
Refractive index: 1
Power Supplies /
In Addition
(Air)
Energy Conservation Support /
Environment Measure Equipment
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, Retroreflection, 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. Retroreflectors (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 "retroreflective".
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.
Motion / Drives
1. Properties of Light
Rectilinear Propagation
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.
Diffuse Reflection
Common
1
Technical Explanation for Photomicrosensors
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.
Light
intensity
Cycle
Safety Components
0
Switches
Light
intensity
0
Time
Time
Light from LED
Relays
Light incident
Control Components
Sunlight/
Incandescent
Light
Light interrupted
Automation Systems
Input to Sensor's
Receiver
DC
Component
Removal of DC Component
Motion / Drives
After DC
Component
Removal at
Receiver
Digitization
Energy Conservation Support /
Environment Measure Equipment
ON
Sensor Output
(Light-ON)
OFF
Power Supplies /
In Addition
Others
Common
2
Technical Explanation for Photomicrosensors
Classification
2. Considerations when Choosing a Sensing Method
(1) Slot Sensors
• Shape, slot width, connection (pre-wired/connector)
• Presence or absence of external light interference (nonmodulated light/modulated light)
• Output configuration (Light-ON/Dark-ON, NPN/PNP)
• Indicator (Light-ON/Dark-ON)
(2) Through-beam Sensors
• Shape, sensing distance
• Output configuration (Light-ON/Dark-ON)
(3) Retroreflective Sensors
• Sensing distance
• Output configuration (Light-ON/Dark-ON)
(4) Diffusive/Limited-reflective Sensors
• Shape, sensing distance
• Presence or absence of background objects (Diffusereflective/Limited-reflective Sensors)
• External light interference (non-modulated light/
modulated light)
• Output configuration (Light-ON/Dark-ON)
Switches
Safety Components
Relays
Control Components
Automation Systems
(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.)
Sensors
1. Classification by Sensing Method
For information on the configuration of each method, refer to
the sensing distance reference diagram in Explanation of
Terms.
Motion / Drives
Energy Conservation Support /
Environment Measure Equipment
Power Supplies /
In Addition
Others
Common
3
Technical Explanation for Photomicrosensors
Explanation of Terms
Term
Reference diagram
Non-modulated light
Modulated light
Explanation
Modulated light
Light
intensity
Light
intensity
Modulated light:
Method used to detect light emitted in pulses
by the emitter element.
0
Time
Slot width
Time
Sensing distance
Emitter
The slot width, i.e., the distance between the
opposing faces of the emitter and receiver, is
the sensing distance.
Receiver
Safety Components
Through-beam
Sensors
(with slot)
Non-modulated light:
Method used to detect light steadily emitted by
the emitter element.
Switches
0
Cycle
Sensors
Non-modulated light
Sensing distance
Through-beam
Sensors
Emitter
Receiver
Sensing
distance
Sensing distance
Retroreflective
Sensors
Reflector
Sensing distance
Sensing object
Emitter/receiver
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.
Automation Systems
Diffusereflective
Sensors
Limitedreflective
Sensors
Control Components
Emitter/receiver
Relays
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.
Releases
Operates
Operates
Sensing
object
Operates
Releases
The difference in distance between the
operating point and releasing point.
Motion / Drives
Differential distance
Releases
Through-beam
Differential distance
Reflective
Energy Conservation Support /
Environment Measure Equipment
(Example for Slot Sensor)
Disk
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 frequency
1 mm
2.1 mm
1 mm
t = 0.2 mm
Power Supplies /
In Addition
(t: thickness)
0
Response time
0
Light input
t
Control
output
t
White paper
Others
Operating time
(TON)
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)
Releasing time
(TOFF)
White paper
White paper
The level of illumination on the sensing surface
that enables stable operation of the Sensor.
Receiver
Receiver
Common
Ambient illumination
Receiver
4
Technical Explanation for Photomicrosensors
Further Information
Sensing Position Characteristics
Sensors
Interpreting Engineering Data
Repeated Sensing Position Characteristics
Sample characteristics for the EE-SX77
Sample characteristics for the EE-SX77
Switches
Dark-ON
Dark-ON
d = ±0.002 mm
Light-ON
0
1.0
2.0
3.0
4.0
5.0
Light-ON
2.16
6.0
2.18
2.20
2.22
Distance d (mm)
Distance d (mm)
Vcc = 24V Number of repetitions: 20, Ta = 25°C
Receiver Output Excess Gain vs. Sensing Distance Characteristics
Parallel Movement Characteristics
Sample characteristics for the EE-SPW311/411
Sample characteristics for the EE-SPW311/411
Distance Y (mm)
1,000
500
300
100
50
30
Control Components
• 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.
Relays
• Indicates whether or not the Sensor responds with respect to
sensing object edge position. (Design the application so that light will
be completely interrupted.)
140
120
100
80
Automation Systems
Receiver output excess gain (multiple)
Safety Components
d
d
10
60
5
3
Distance Y
40
1
20
Distance X
0
0.2
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
Distance X (m)
• 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
Retroreflector 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
Sensing Distance vs. Object Area Characteristics
Sensing object:
2
White paper (15 × 15 mm )
(reflection factor: 90%)
Releases
6
5
Operates
4
3
Relative sensing distance d (%)
7
Sample characteristics for the EE-SPY
500
Sensing object:
2
White paper (15 × 15 mm )
(reflection factor: 90%)
300
Power Supplies /
In Addition
Distance Y (mm)
Sample characteristics for the EE-SPY311/411
Energy Conservation Support /
Environment Measure Equipment
• 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
1 m. The receiver output excess gain can be thought of as being
approximately 10 times the rated sensing distance.
Motion / Drives
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
Distance between Sensors (m)
200
100
80
50
X
2
30
Others
Y
1
0
−5
−4
−3
−2
−1
0
1
2
3
4
5
Distance X (mm)
1
2
3
5
10
20
50
100
Size (mm)
• Indicates the change in the sensing distance when the area of a
white piece of paper with a reflection factor of 90% of the standard
sensing object is increased. (The sensing distance will change with
the reflection factor.)
Common
• Indicates the starting sensing position when the standard sensing
object is moved perpendicular to the optical axis. (These values
apply to the standard sensing object. If the sensing object changes,
the operating range and sensing distances also change.)
10
5