Guide Description
Safety laser scanners provide flexible, non-contact safeguarding by monitoring defined areas around hazardous machinery. Unlike a physical guard, a scanner can create configurable protective fields that allow access while detecting when a person enters a hazardous area.
This guide explains where safety laser scanners are best applied, how protective and warning fields work, how safety distance is determined, and the practical considerations that affect scanner selection, placement, integration, and validation.
1. What Is a Safety Laser Scanner?
A safety laser scanner is an electro-sensitive protective device that uses laser scanning technology to monitor a defined area for people or objects.
The scanner repeatedly measures its surroundings and compares what it detects against configured safety fields.
A typical application may include:
- Safety laser scanner
- Configured protective field
- Optional warning field
- Safety relay, controller, or safety PLC
- Safety-rated machine outputs
- Manual reset where appropriate
- Machine stopping circuitry
When someone enters the protective field, the scanner signals the safety system to initiate the required safety function.
Practical takeaway: The scanner doesn't physically prevent access. It detects access and relies on the complete safety system to achieve a safe condition before the person reaches the hazard.
2. Where Are Safety Laser Scanners Used?
Safety scanners are particularly useful when a traditional physical barrier or straight-line light curtain isn't practical.
Common applications include:
- Robot and automated cells
- Assembly equipment
- Palletizing systems
- Material handling equipment
- Load and unload stations
- Conveyor systems
- Automated guided vehicles and mobile equipment
- Open machine areas
- Large perimeter safeguarding applications
- Presence detection inside guarded areas
One of their biggest advantages is flexibility.
Instead of requiring a straight sensing plane, the scanner's protective field can often be configured around equipment, columns, conveyors, workstations, and other obstacles.
3. Protective Fields vs. Warning Fields
Safety scanner applications may use multiple field types.
Protective Field
The protective field is the safety-related detection zone.
When a person or object meeting the scanner's detection criteria enters this area, the safety system initiates the intended safety function.
Warning Field
A warning field can extend beyond the protective field and provide an earlier, non-safety-related indication.
For example:
Warning Field Entered → Audible/Visual Warning → Protective Field Entered → Safety Function Initiated
This can be useful where unnecessary machine stops affect productivity.
Important: A warning field should not be confused with the safety-rated protective field.
4. Safety Distance: Why It Matters
A scanner cannot simply be placed at the edge of a hazard.
It must be positioned and configured so that after a person is detected, the machine can achieve the required safe condition before that person can reach the hazard.
Conceptually:
Safety Distance = Approach Considerations + Total System Stopping Performance + Application-Specific Factors
The actual calculation depends on the applicable standard, scanner configuration, machine, detection capability, approach direction, stopping performance, and other factors.
The key principle is simple:
The longer the machine takes to stop, the more distance generally needs to exist between detection and the hazard.
5. Stopping Time Is Critical
A scanner detects someone quickly—but the machine itself does not necessarily stop instantly.
The complete response may look like:
Person Detected → Scanner Responds → Safety Logic Responds → Safety Outputs Change State → Machine Responds → Hazard Stops
Each portion contributes to the total stopping performance.
For this reason, safety-distance determination shouldn't be based solely on a machine's assumed stop time or one component's published response time.
Stopping-time measurement at the machine can provide critical information for determining and validating the scanner application.
6. Scanner Resolution & Detection Capability
Safety scanners can be configured or selected for specific detection capabilities depending on the device and application.
The detection capability influences whether the scanner can reliably detect the intended object or person.
It can also affect:
- Protective-field dimensions
- Safety-distance calculations
- Maximum scanning range
- Mounting configuration
- Application suitability
A larger advertised scanning range doesn't automatically make a scanner better for an application.
The safety function needs to be designed around the required detection capability.
7. Horizontal Area Guarding
One of the most common scanner applications is monitoring an area across the floor.
The scanner creates a two-dimensional protective field around the hazard.
This can work well when operators need to approach equipment from an open side without opening a physical door.
For example:
Operator Approaches → Warning Zone → Protective Field → Machine Safe Condition
Horizontal scanning can also provide an advantage over a light curtain when the application requires area detection rather than simply detecting someone crossing a line.
8. Vertical Access Guarding
Depending on the scanner and application, scanners may also be configured to monitor a vertical plane or opening.
This can function similarly to perimeter access detection.
However, vertical applications require careful consideration of:
- Detection capability
- Scanner position
- Reach-through
- Reach-over
- Reach-under
- Openings around the field
- Reference boundaries or contour monitoring where applicable
If the objective is simply to protect a defined opening, a light curtain may sometimes provide a simpler solution.
9. Presence Detection Inside a Guarded Cell
One of the strongest applications for safety scanners is detecting personnel who have entered an enclosed safeguarded area.
Consider this scenario:
Door Opens → Person Enters → Door Closes → Person Remains Inside
An interlocked door can detect the door position, but by itself it doesn't necessarily determine whether someone remains inside the cell.
A properly designed scanner application can monitor an interior area and help prevent hazardous restart while someone occupies the monitored zone.
This can be particularly useful in:
- Robot cells
- Palletizing systems
- Large automated cells
- Material handling systems
- Areas with limited visibility from the reset station
10. Blind Spots & Unmonitored Areas
A scanner only protects the area it can reliably monitor.
Machine bases, structural columns, guarding posts, conveyors, tooling, fixtures, and other objects can create areas that aren't visible to the scanner.
These shadowed or unmonitored areas need to be evaluated during the safeguarding design.
Solutions may include:
- Relocating the scanner
- Using multiple scanners
- Adding physical guarding
- Adding another presence-sensing technology
- Redesigning the protected area
If the scanner can't see it, don't assume it's protected.
11. Mounting Height & Location
Scanner placement affects the effectiveness of the entire system.
Designers should consider:
- Mounting height
- Approach direction
- Scanner orientation
- Detection capability
- Field geometry
- Floor conditions
- Structural obstructions
- Reach or step-over possibilities
- Environmental exposure
- Risk of physical damage
Mounting a scanner where it is convenient for installation isn't necessarily the same as mounting it where it provides effective safeguarding.
12. Preventing Step-Over or Reach-Through
Depending on how the scanner field is configured, personnel may potentially:
- Step over the protective field
- Reach over it
- Reach through an opening
- Approach from an unmonitored direction
- Stand in an undetected area
The scanner's location and protective field must therefore be evaluated together with surrounding physical guarding and machine geometry.
Safety distance alone does not address every possible path to the hazard.
13. Multiple Fields & Zone Switching
Modern safety scanners can often support multiple protective-field configurations.
This can be useful when the hazardous area changes based on machine operation.
For example:
Machine State A → Protective Field A
Machine State B → Protective Field B
This can allow the safeguarding system to adapt to different machine conditions while maintaining the required risk reduction.
Potential applications include:
- Robot position changes
- Material transfer
- Automated carts
- Different operating modes
- Loading and unloading sequences
Field switching should be incorporated into the safety-related control strategy, not simply treated as a convenience feature.
14. Environmental Considerations
Safety scanners operate optically, so the surrounding environment matters.
Application considerations can include:
- Dust
- Dirt
- Welding processes
- Reflective surfaces
- Moisture
- Temperature
- Vibration
- Direct sunlight
- Physical impact
- Floor conditions
- Nearby optical devices
The manufacturer's application requirements should always be considered when determining whether a scanner is appropriate for the environment.
A safety-rated device used outside its intended conditions may not provide a reliable safeguarding solution.
15. Scanner vs. Light Curtain vs. Guard Door
Each technology solves a different safeguarding problem.
| Safeguarding | Strong Application |
|---|---|
| Safety Laser Scanner | Flexible area and presence detection |
| Light Curtain | Frequent access through a defined opening |
| Interlocked Guard Door | Controlled physical access through perimeter guarding |
| Guard Locking | Access where hazardous conditions remain after a stop request |
| Fixed Guarding | Areas where routine access isn't required |
For example, a robot cell might use:
Physical Guarding + Interlocked Door + Interior Safety Scanner
Another machine might use:
Physical Guarding + Open Access Point + Safety Light Curtain
The best solution is based on the application—not the technology someone prefers to use.
16. Common Safety Scanner Application Mistakes
Common problems include:
- Protective field too close to the hazard
- Using assumed instead of verified stopping performance
- Incorrect detection capability
- Poor mounting location
- Unprotected blind spots
- Step-over or reach-around access
- Objects obstructing the scanner's view
- Incorrect field configuration
- Automatic restart when the protective field clears
- Poor reset location
- Improper field switching
- Environmental conditions not considered
- Assuming the scanner protects areas outside its monitored field
A safety scanner may be safety-rated, but:
A safety-rated component does not automatically create a safe application.
17. Reset & Restart Strategy
When a scanner detects a person and initiates a safety function, clearing the protective field should not automatically be assumed to mean that hazardous operation can safely restart.
Depending on the application, a deliberate reset may be required.
A typical strategy may look like:
Area Clear → Protective Field Clear → Manual Reset → Machine Ready → Separate Start Command
The reset location should be evaluated so the person resetting the safety system can appropriately verify the safeguarded area.
For large cells or areas with poor visibility, additional measures may be necessary.
18. Integration Into the Safety System
The scanner is only the input side of the safety function.
A complete system may look like:
Person Detected → Safety Scanner → Safety Controller → Safety Outputs → Machine Actuators → Hazard Stops
The required architecture depends on the risk assessment and applicable functional-safety requirements.
Simply connecting a scanner to a standard PLC input does not automatically create an appropriately safety-rated system.
The complete safety function needs to provide the required level of risk reduction.
19. Installation & Validation
Installation isn't complete simply because walking into the scanner field stops the machine.
The completed safety function should be validated to verify that it performs as intended.
Validation may include:
- Protective-field dimensions
- Detection capability
- Scanner position
- Safety distance
- Stopping performance
- Warning-field operation
- Blind spots
- Step-over and reach-around access
- Reset behavior
- Restart prevention
- Field switching
- Fault response
- Safety controller logic
- Machine response
This connects engineering assumptions to actual machine performance.
Safety Laser Scanner Best-Practice Checklist
Before finalizing an application, ask:
☐ Does the risk assessment support using a safety scanner?
☐ Is the scanner appropriate for the environment?
☐ Is the detection capability appropriate?
☐ Has total stopping performance been established?
☐ Has the required safety distance been determined?
☐ Is the protective field configured correctly?
☐ Are warning and protective fields being used appropriately?
☐ Can someone step over or reach around the field?
☐ Are there blind spots or shadowed areas?
☐ Can someone remain undetected inside the safeguarded area?
☐ Is the reset location appropriate?
☐ Does clearing the field avoid automatically initiating hazardous motion?
☐ Is field switching safety-related where required?
☐ Is the scanner properly integrated into the safety-related control system?
☐ Has the completed safety function been validated?
The Takeaway
Safety laser scanners provide one of the most flexible methods of machine safeguarding because the protective area can be designed around the application instead of relying solely on a physical barrier.
But that flexibility makes proper application engineering especially important.
Detection capability + protective-field design + stopping performance + safety distance + blind-spot prevention + safety controls + validation all need to work together.
The goal isn't simply to detect someone entering a red zone.
The goal is to detect the person early enough—and reliably enough—for the machine to achieve the required safe condition before the hazard can be reached.
