Escáner láser de seguridad versus cortina de luz: cómo elegir

Safety laser scanner vs light curtain is the machine-guarding choice between area sensing and point-of-operation sensing, and it comes down to one practical question an operator faces at the press, robot cell, or floor: do you need fast, high-resolution finger protection right at the point of operation, or multi-meter area monitoring across, say, three machine frames or 50 meters of AGV track? Both are optical presence sensing safety devices that stop machinery before a person reaches a hazard, but the safety space they protect takes two very different forms. This guide compares a light curtain and a laser scanner on detection method, Type and SIL rating, resolution, safe distance, and five-year cost, so you can pick the right one for your press or conclude that both belong in the best safety solution.

Safety Laser Scanner vs Light Curtain: The Quick Answer

A safety light curtain protects a fixed detection plane at the point of operation and reaches Type 4 / SIL 3 for finger-to-body protection; a safety laser scanner protects a configurable two-dimensional area or floor zone at Type 3 / SIL 2, which suits AGVs, robot cells and large perimeter monitoring. In short: the light curtain wins where a worker reaches into a machine, and the laser scanner wins where a worker walks around it. Most plants end up using both, and a single safety relay module can process the stop signal from either device.

The numbers; the standards; an ISO 13855 safe-distance calculation you can run yourself; and a four-question selector to make the call.

Getting this wrong is an expensive mistake: an under-rated device can fail a safety audit, while an over-specified scanner wastes budget on a 14 mm finger hazard a curtain already covers. Because QJKH engineers both the ENT curtain and the SH scanner to IEC 61496, our certified production team sizes the decision to the press or robot cell in front of you, not the brochure.

How Each Device Detects: Detection Plane vs Scanning Field

The fundamental difference is geometry, and it is worth naming. We call it the Plane vs. Field Coverage Model: a light curtain protects a plane, while a laser scanner protects a field. A curtain places a transmitter and receiver on either side of an opening, whereas a scanner sits in one corner and sweeps the floor, and that single structural difference drives almost everything else in this comparison.

A safety light curtain is formed from a transmitter and a receiver that face each other and emit a vertical or horizontal series of infrared light beams. If any opaque object blocks one beam, then the receiver drops the signal and the device outputs an immediate stop signal. Since the spacing of the beams is fixed, the curtain has no concept of shape or position of what’s moving through it; it only knows that there’s an intrusion, which it then responds very quickly in a binary way.

A safety laser scanner operates time-of-flight. A pulsing laser beam is projected by a scanning mirror, it sweeps up to 270°, and times the reflection to measure distance. The scanner has no separate receiver; unlike a curtain it does not need an opposing unit, it ‘reads’ reflection off ambient space. Software defines selectable protection and warning areas so, the same scanner may cover an awkward region, trigger warning on another region then command stoppage when an object encroaches the inner area. US9423499B2 describes a safe object-detection and output-evaluation method, and US11624823B2 cover how a scanner monitors its own operation to guarantee safe use when contamination occurs.

What is the difference between an area sensor and a light curtain?

An area sensor-otherwise a safety scanner, safety laser scanner or area scanner- measures a two dimensional area and responds to presence within an area setting. A light curtain only detects whether an object breaks a plane of beams. In other words, an area scanner measures space around a machine; a curtain draws a trip line. That’s why scanners protect floors of robots while curtains protect press openings.

The reason this matters is structural: because the curtain plane is fixed, it cannot follow a moving robot or AGV, and that trade-off is the root cause of the entire comparison. A scanner reads reflected light over several meters, so it tolerates a layout change a 1,827 mm curtain cannot, per IEC 61496-3.

Safety Classification: Type 4 / SIL 3 Curtain vs Type 3 / SIL 2 Scanner

Here’s the point that’s the source of almost every decision making error, and it can be plainly stated – as the “Type Ceiling Rule,” – no scanner of type 3/SIL2/PLd/category 3, however sophisticated, can serve as a replacement for type 4 / SIL3 / PLe / category 4 light curtains at a points of highest risk. The slogan which “safety laser scanners are displacing light curtains” does hold up regarding areas and peripheries of guarding-but only at those locations. It doesn’t apply where the higher Type 4 security must be used – point-of-operation finger and other areas.

The Type classes emanate from the IEC 61496 family of electro-sensitive protective equipment (ESPE) standards. Light curtains are active opto-electronic protective devices (AOPDs) under Type 2 or 4. Laser scanners are active opto-electronic protective devices responsive to diffuse reflection (AOPDDR), classified Type 3. In the 2025 edition, the detection-capability and fault-detection minimums for Type 3 devices were raised in IEC 61496-3. Their maximum reach for performance level (PL) and safety integrity level (SIL) are given by ISO 13849-1 and IEC 62061, respectively. As is readily asserted by Datasensing (which builds both), a scanner reaches PLd, but a Type 2 curtain only PLc (though Type 4 achieves PLe).

“Treat the Type rating as a ceiling, not a preference. We size every quote to the risk assessment first: if the hazard is a power press where hands enter the die space, the answer is a Type 4 curtain, full stop. The scanner earns its place around the cell, not at the nip point.”

QJKH Functional Safety Engineering Team

Detection Capability and Resolution Compared

Resolution divides device applicability by body parts. It’s the single best separating feature between the technologies. With 14 mm beams, a Type 4 light curtain will stop a finger, 30 mm a hand, 40 mm a body. Viewing height spans from just 160 mm (on small units) up to a meter or more (e.g., 1800 mm+ for whole body monitoring). Because it’s triggered as soon as even one beam is blocked, close proximity to the hazard is feasible while holding guarded opening sizes to the bare minimum.

In contrast, a laser scanner prioritizes reach over resolution. The smallest object a scanner can typically detect is in the 70 mm range (leg-guarding for floor zone), but extend the detection out to several meters (e.g., a 5.5 meter danger field, and 20 meter warning field). A scanner won’t notice a finger, but it may observe an entire zone around an automaton, alter its protective zone shape as the device shifts tasks, and ignore persistent background intrusions like a forklift truck’s path. For monitoring a vast and irregular hazard zone for entire bodies (or even teams of workers), this area coverage is a benefit that curtains can’t offer.

Mis-specifying 14 mm finger versus 30 mm hand resolution is a common and costly mistake, because the wrong beam spacing either fails to protect fingers at the point of operation or trips on a forearm in production. QJKH holds finger resolution to a 14 mm tolerance for exactly this reason, in line with ISO 13855.

The resolution-to-safety-distance relationship for both devices is defined in ISO 13855.

Head-to-Head Specification Comparison

Here’s the full side-by-side – our 12-Row Scanner-vs-Curtain Spec Table. Use it to shortlist before you read the application section.

Read the table as a set of trade-offs, not a winner: the curtain’s 14 mm resolution is the reason it wins the press, while the scanner’s 270° field is the reason it wins the cell. Because QJKH builds and certifies both, the comparison is honest rather than a single-product pitch, and every number is cross-checked to CE and IEC 61496 datasheets.

The scanner’s time-of-flight detection method is documented in US patent US9423499B2.

Which One Fits Your Application?

The choice is driven by where the hazard is and whether anything moves. The scenario-to-device map below covers the most common cases in machinery, robotics and automation. As a working rule, fixed access points and point-of-operation hazards call for a light curtain, while open floors, robot-cell perimeters and moving platforms make the laser scanner the better choice; on many lines both safety sensors run together.

Press shop. On a stamping line, an operator hand-feeds blanks into a hydraulic press every few seconds. Here a 14 mm Type 4 curtain mounted at the operator station detects finger entry and stops the ram within milliseconds, while muting lets the finished part exit on the outfeed without a false stop. A scanner can’t see the finger and its 60-134 ms response would force the curtain plane far back – the curtain is the only correct choice to protect workers at this point of operation.

Robot weld cell. A robotic welding cell throws sparks and moves unpredictably, so the hazard is the whole floor area, not a single opening. A laser scanner mounted at a corner watches the approach zone, slows the robot when someone enters the warning zone, and stops it in the protected zone – then resumes automatically once the area clears, avoiding a manual restart. A curtain at the cell entrance can supplement it for access guarding.Robot cell safeguarding usually layers both.

AGV aisle. In an automated warehouse, an AGV travels shared aisles where people walk. A scanner mounted low on the front of the vehicle scans the ground plane ahead, reducing speed in the outer field and stopping before contact in the inner field as objects enter its path. This is the textbook job for a scanner and a fixed curtain simply can’t ride along – see AGV safety for layout guidance.

Where are safety laser scanners typically used?

Safety laser scanners are used wherever the protected zone is an area rather than a line: around robot cells, on AGVs and autonomous mobile robots, at the perimeter of automated warehouses, and on large machines where a person can stand inside the hazardous area. Their configurable zones and several-meter reach make them the default for mobile robotics and area guarding, which is also why EN 1525 leans on them for driverless industrial trucks.

The common mistake here is forcing one device onto every hazard, because a fixed curtain plane cannot ride an AGV and a 70 mm scanner cannot guard a press nip. In practice on a hydraulic press or a robot cell, matching the device to the risk — not to habit — is the difference between a clean audit and an exposed operator, which is why QJKH application engineers start from EN ISO 3691-4 and the risk assessment.

Calculating Minimum Safety Distance (ISO 13855)

Both devices share one formula for safe distance, and running it yourself is the fastest way to feel the difference between them. ISO 13855 gives the minimum distance from the hazard as:

S = K•T+C where S is the minimum safe distance (mm), K is the approach speed (2,000 mm/s for hand/arm movement up to 500 mm), T is the total stop time of the whole safety system, and C is the intrusion distance that depends on detection capability.

Light curtain, worked. For a 14 mm finger-resolution curtain, the intrusion term is C = 8 • (d 14) = 8 • (14 – 14) = 0 mm. If the curtain plus machine total stop time T is 0.2 s, then S = 2,000 • 0.2 + 0 = 400 mm. Swap to a 30 mm hand-resolution curtain and C = 8 • (30 – 14) = 128 mm, so S = 400 + 128 = 528 mm. Finer resolution lets you mount closer and save floor space.

Laser scanner, it worked. For a horizontal floor zone the standard typically uses a walking algorithm and adds a height term: S = (1,600 T) + 1,200 0.4 H, and then allows for a measurement uncertainty Z for the scanner. For T = 0.2s and H = 300 mm mounting height, S = 320 + 1,200*120 = 1,400mm, and adding the 100mm or so measurement uncertainty brings you into 1,500 mm. The slower speed and larger intrusion term are what drive much higher standoff for a scanner compared to a curtain – fine around a cell, terrible at a press.

Skipping this calculation is one of the most expensive mistakes in machine guarding, because mounting inside the safe distance leaves the hazard exposed even when the device reads OK and passes a quick check. The 400 mm curtain result and the roughly 1,500 mm scanner result above are not interchangeable; QJKH runs the ISO 13855 numbers against your measured stop time before quoting a mounting position.

These approach-speed calculations are governed by ISO 13855, with point-of-operation duties set by OSHA 29 CFR 1910.217.

Total Cost of Ownership Over 5 Years

Sticker Price isn’t the big number. We generally break real costs down by this 5-Layer Cost-of-Ownership Stack:

As a generalization, there’s a low device cost and low system setup for the Light Curtain, it tends to be simple tomaintain, and that’s the reason the Curtain is often the lowest cost to procure and implement for Fixed Point-Of-Operation safeguarding and for cost sensitive applications. On the other side, the laser scanner tends to have the highest up-front cost and the longest integration time, but pays off quickly when retooling times and production changeover times are high. these positions aren’t firm figures- inquire for a quote that include machine setup, duty cycle, etc. so we can discuss device price lists that move around.

The hidden cost is downtime: a scanner that nuisance-trips on a reflective pallet can lose more in production than the device costs, because false stops compound across a 5-year life and a tuned zone set can cut them sharply. Because QJKH builds both, our engineers tune the zones and the 70 mm detection limit to the line rather than over-selling the more expensive option.

The underlying guarding obligation that drives these lifecycle costs traces back to OSHA machine-guarding standards.

Limitations, Failure Modes and Common Field Mistakes

We tend to observe these 6 errors from the field, whenever an team must decide between these systems:

• – A finger beam on a press a standard type 3 scanner can’t satisfy point-of-operation: that’s The Type Ceiling Rule.
• – Reach over or round bypass. This is a vertical plane that an operator must work through. They’ve achieved correct placement. But a human can just step over or around the safety plane.
• – Placed too Close. Simply not running the ISO 13855 (above) means the operator comes inside the safety zone.
• – Bypassing Muting. Muting requires distinction between product and people. Defeating it’s like open the gate and leaving it unattended.
• – Don’t Include the Whole Stop Stack. We need to look beyond just device response and also the PLC and the final machine stop time in “T.”
• – Shining Floors causing “nuisance” stops for laser scanners. Shiny or Wet floors, and pallets can reflect the beam creating trips that are only the cause of inconvenience, rather than safety on some occasions.

In practice on a foundry press line or a woodworking cell, dust, steam and reflective surfaces are the real limit on a scanner, while a curtain’s 14 mm plane is defeated by reach-over if mounted without a standing-surface check. QJKH validates these failure modes in-house before shipping, because a missed mistake here is a missed injury.

Scanner optical-window self-monitoring against the dust and contamination failure mode is covered in US patent US11624823B2.

How to Choose: The 4-Question Selector

When an urgent situation demands a quick decision, run the 4-Question Scanner-or-Curtain Selector. It resolves most cases in under a minute, routing finger and hand point-of-operation hazards to a light curtain, area and floor hazards to a laser scanner, mobile platforms to a scanner, and combined perimeter-plus-access needs to a layered system.

Layered makes sense. Area scan often provides peripheral zone coverage around a robot cells and then a light curtain provide flat plane coverage across an entry. Both are wired to safety relays. If pressure sensitive safety mats are an option you can then refer our three-way comparison of light curtains, laser scanners and safety mats. Our Type 2 vs Type 4 selection guide helps you choose the curtain Type appropriate to the safety level.

In practice on a press brake or an AGV aisle, the wrong answer here is the costliest mistake because it is locked in at install, and a 70 mm scanner cannot be retrofitted into a 14 mm finger duty. Confirm the call against your risk assessment and EN ISO 3691-4 for mobile platforms; QJKH engineers will sanity-check the layout before you commit.

Industry Outlook: Why the Lines Are Blurring

It’s a stretch to say it’s “scanner vs. curtain” today. it’s more that you layering your light curtains and scanners to cover both fixed point-of-operation and moving area hazards. The AGV, AMR, and Collaborative robots are certainly driving the evolution and with them increased need for agile areas detection, as a static light plane doesn’t accommodate mobility, as you will see illustrated by standards updates ISO 3691-4 published in 2023 covering driverless industrial trucks and an update to the IEC 61496-3 specification which tighten coverage requirements in 2025. Don’t forget, Finger protection in a point of operation isn’t changing, that is still firmly the job of light curtains (Specifically Type 4/SIL 3).So the important question to ask your safety vendor isn’t “either/or?” it’s “how do they best pair in my application?.” The safety system you’re installing to integrate these devices should be able to readily support each. For example analysts predict the safety laser scanner market will grow to $0.5 billion by 2025 and beyond so keep this safety technology in your sight, but it shouldn’t be your deciding factor.

The 2023 revision of ISO 3691-4 codifies safety-scanner use on driverless industrial trucks.

Preguntas frecuentes