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Thermal vs. Optical Sensors

March 16th, 2023 | 11 min. read

Thermal vs. Optical Sensors

Ignat Goossens

Ignat Goossens is an Enterprise Account Executive at VergeSense. He has a deep passion for people and design and in his role he is able to combine these two passions and help organisations create truly people-centric workplaces.

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As businesses strive to strike a balance between real estate costs and employee experience, the challenge of dealing with the effects of inconsistent occupancy is harder than ever before. Whether it’s fluctuating attendance on different days, or varying patterns of space usage across offices and companies, the need for accurate occupancy tracking has never been more critical.

Fortunately, with the rapid development of occupancy tracking solutions in the market, there are myriad options to choose from. But, how do you determine which solution is best suited for your organization? 

While many solutions may appear similar, it's important to recognize that not all occupancy tracking solutions are created equal. There are varying capabilities, benefits, and costs associated with each.  

To simplify the evaluation process, we will compare the pros and cons of two commonly used technologies for measuring workplace occupancy— thermal sensors and optical sensors. This comparison will help you make an informed decision about which solution is the best fit for your workplace. 

Thermal Sensors

Thermal sensors work by detecting the heat signatures of objects in their field of view. 

So, what does this mean? 

When people enter a room and move around in it, they emit heat, and the thermal sensor can detect these changes in temperature to determine the presence and movement of people. 

How Do Thermal Sensors Work?

All objects emit infrared radiation as a result of their temperature. This radiation falls within the infrared region of the electromagnetic spectrum, which is usually not visible to the naked eye. Thermal sensors are designed to detect this radiation and convert it into a visual representation of temperature, providing insight into occupancy. 

These sensors consist of a lens that focuses the infrared radiation onto a bunch of small, temperature-sensitive elements called microbolometers. Each bolometer measures the temperature of a small area of the image, and the combined output forms an image that represents the temperature of the objects in the field of view. 

The thermal sensor detects this change in energy and sends a signal to the control unit of the sensor, which then triggers the lights or other connected devices to turn on.

Thermal occupancy sensors can detect people even when they are stationary and not moving, making them ideal for detecting occupants in large areas such as warehouses, conference rooms, and auditoriums.

The sensitivity and detection range of thermal occupancy sensors can be adjusted to suit the specific application. For example, in a small room, the sensor may have a narrow detection range, while in a large warehouse or open office space, the sensor may have a broader detection range.

The Benefits of Thermal Sensors

1. They are non-intrusive 

Thermal sensors do not emit any radiation and do not require any physical contact with the person being detected. Since they don’t capture any visual or personal information about individuals, and only detect temperature changes of objects in their field of view, these sensors are usually favored in organizations where privacy is top of mind. This makes them a non-intrusive solution for detecting occupants in a room or area.

2. They are more accurate than PIR sensors, Badge, and WiFi location tracking 


Thermal sensors can detect people sitting or standing still, which may be missed by motion sensors that rely on movement. They can also provide more reliable occupancy data than PIR sensors, which can be triggered by changes in temperature caused by other factors such as sunlight or wind. Finally, they are more accurate than a badging system, which only measures attendance, not occupancy, and lends itself to misinformation due to tailgating. 

3. They don’t rely on visual cues

Unlike optical sensor technology, thermal sensors can detect the heat signatures of people and objects in a room, making them useful for tracking occupancy in low-light or dark environments. 

The Drawbacks of Thermal Sensors

1. Thermal sensors confuse common things for people, which leads to inaccurate occupancy data


Thermal sensors offer limited technology that can only capture people, never objects, making it impossible to gain a true understanding of your workplace. Since these sensors can detect changes in temperature caused by sources other than humans, such as pets, machinery or sunlight, they can provide false positives and inaccurate occupancy data.

Conversely, they sometimes fail to detect individuals who are not generating enough heat, such as people who are sitting still or wearing heavy clothing. This can result in false negatives, and a vast underestimation of occupancy. 

Environmental factors such as air conditioning, heating systems and drafts can also affect the accuracy of these sensors, as the sensors may detect these as changes in occupancy.

The placement of the sensor can also affect their accuracy. For instance, sensors that are placed too high or low would be unable to capture the full range of activity in the room. Similarly, if the sensors are placed near the window or by a door may be subject to drafts or other environmental factors, skewing the accuracy of the data. 

2. Thermal sensors fail to capture passive occupancy, which means you are missing out on 50% of your occupancy data

In today's world of dynamic and flexible workplaces, people are on the move in the workplace more than ever before, leaving behind their bags, laptops, and coats within spaces for their return. This concept is known as passive occupancyand it comprises 50% of your total workplace occupancy. 

Seeing that thermal sensors can only detect changes in temperature caused by the presence of people in a room or area, they will not be able to report and measure passive occupancy. Missing out on this data means you are missing half your occupancy data

This often means that if you have thermal sensors in your workplace, you likely need to rely on additional technology or an Occupancy Intelligence Platform to parse out the remaining 50% of your data to figure out if your spaces are passively occupied. 

3. Limited detection range leading to increased costs

Thermal sensors have a limited detection range compared to other types of occupancy sensors. They are typically only effective in detecting people within a range of 20 to 30 feet, which may not be sufficient for larger rooms or areas.

As a result of this limited detection range, you likely need more thermal sensors in any given space than optical sensor technology. This can lead to increased costs, which might be challenging for workplace leaders to justify in terms of ROI. 

Optical Sensors 

Optical sensors not only accurately understand people count, but can also provide a context of what is happening within spaces, which is what makes them the backbone of an Occupancy Intelligence Platform

How Do Optical Sensors Work?

Optical sensors are a highly advanced sensor technology that when paired with an Occupancy Intelligence Platform can provide accurate people counting and detailed insights into how spaces are being actively and passively occupied. 

They are powered by anonymous computer vision technology, which means that these occupancy sensors go beyond just counting people in spaces to actually understanding how these spaces are being used. 

They detect when spaces are actively and passively occupied by identifying humans and common objects that are associated with human presence. They do this by converting light into an image, which then uses AI to derive information from that image.

VergeSense optical sensors generate low-resolution imagery on the device and uses ELS technology (edge-processing, low resolution, and secure) to keep employee privacy protected. This means that the low resolution image derived is immediately destroyed once the AI derives information from it in the form of 0’s and 1’s. 

Other optical sensor solutions, such as XY Sense, use edge processing high-resolution cameras. 

The Benefits of Optical Sensors

1. They accurately capture activity in your spaces

Optical sensors utilize advanced AI to process captured data, leading to an enhanced understanding of every workspaceover time. They can seamlessly integrate with various software and hardware in a company's tech stack, such as IWMS, CAFM, keycard readers, and desk and meeting room booking software. This enables the combination of occupancy data collected by the optical sensors with other space data from the rest of the tech stack. 

Optical sensors provide contextualized utilization insights that are unparalleled compared to other sensor technologies. They take into account the holistic understanding of people, objects, characteristics, and interactions within workspaces, enabling them to measure passive occupancy, which accounts for 50% of space utilization, which thermal sensors cannot. 

In addition, optical sensors can accurately detect when a room is still in use, even when someone has left, due to the presence of personal items such as a coat or backpack. This ensures that occupancy data and room and desk booking platforms remain up to date, allowing employees to reserve their desks even if they are not physically present.

2. They generate actionable insights

The most advanced optical sensors use sophisticated AI to process the data that they capture, which constantly improves their understanding of every space over time. The AI generates insights into people count, active occupancy, and passive occupancy, and computer vision automates the collection of insights and adapts it to employee behavior. 

Because these sensors leverage a holistic understanding of the people, objects, characteristics, and interactions happening within workplaces, they can provide contextualized utilization insights unlike any other sensor technology on the market. 

3. Optical sensors provide insight into passive occupancy, unlocking 50% of your occupancy story

As mentioned previously, passive occupancy is when people leave their bags, laptops or coats with the intention of returning to the space.

In today’s world of dynamic space use, employees are always moving around the office and are likely to step out of their room for a coffee break only to return a few moments later. Passive occupancy will indicate that their space is occupied, and prevent it from being released to someone else when it is in use but not actively occupied at that moment. 

The VergeSense platform consists of the only optical sensor technology on the market that can measure passive occupancy, which constitutes 50% of space use. This kind of inaccuracy can impact your metrics greatly, as you would be making workplace decisions with incomplete data. 

4. They are private and secure


To ensure privacy and security, optical sensors use ELS technology, which means the image is converted into low resolution and processed on the device itself. This results in the anonymization of the image, and no personal information is derived or stored. The information obtained is destroyed and only the essential data is sent to the user-interface. 

Optical sensors are one part of an occupancy intelligence platform built for large, established companies where security and privacy are a top priority. As a result, most optical sensors and their corresponding Occupancy Intelligence Platforms are compliant with GDPR, CPIA, ISO/IEC 27001, and SOC 2 Type II to maintain their security and privacy measures.

5. Faster installation process than thermal sensors

Although optical sensors are a lot more complex than most occupancy tracking technologies, let alone thermal sensors, they have a shorter installation process. This, however, depends on the square footage of space in your portfolio as well as the number of sensors being deployed. 

At VergeSense, installation and implementation is typically completed between 60 and 90 days.  This is the fastest time to value of any optical sensor technology on the market. 

The Drawbacks of Optical Sensors

1. A misconception of the implications of using a camera

There is a common misunderstanding that optical sensors use cameras in the ceiling to monitor employees, which can discourage the use of this technology in the workplace. 

This fallacy can dissuade the adoption of this technology. These fears often emerge from a lack of knowledge of how these sensors work, and therefore providing transparency when introducing the technology to your company is paramount, whether it is a thermal sensor or a new sensor technology. 

The reality of smart offices today is that nearly every intelligent device, from Google Home to Alexa, has some form of optical technology designed to drive accuracy. It is the fear of who has access to this data that impedes these investments. 

Should I choose Thermal Sensors or Optical Sensors for my office?

Thermal Occupancy Sensors Might be Right for You If... 


If you are a small to medium-sized business in need of a baseline understanding of workplace occupancy, thermal sensors may be a sufficient solution to meet your needs. 

Other characteristics that may suggest thermal occupancy data suiting your organization's needs include: 

  • You are a small to mid-sized business and don’t have to make enterprise-level decisions

  • You are confident with making workplace decisions based solely on active occupancy, and don’t plan to integrate with other desk or room booking solutions. 

  • You are willing to spend significant money on cabling, and are okay with a lack of flexibility in your occupancy tracking. 

  • You don’t have a global workplace portfolio.

  • ESG and sustainability is not a focus in your organization.

Here Are the Characteristics of Enterprises for which Optical Sensors Might be the Right Fit:

If you are a large enterprise with a predominantly in-office or hybrid workforce, you need accurate, contextualized data driving your decisions. In this scenario, you would need an Occupancy Intelligence Platform, which has optical sensors built into the capture layer of the solution. Other characteristics that optical sensors may be best for your organization include:

  1. A global real estate portfolio

  2. More than 5,000 employees

  3. The need to optimize your portfolio by either adding more space or reducing space

  4. The need to make space optimization decisions surrounding space design, planning, cleaning, and/or availability.

  5. A hybrid or in-office workforce

Are You Still Unsure About What Occupancy Tracking Solution is Right for You? 

We’ve got you covered. Here are the top 4 most common occupancy tracking solutions (apart from Thermal sensors) you are likely considering before making a decision. 

  1. WiFi Location Tracking

  2. Badge Data

  3. PIR Sensors 

  4. Optical Sensors

Have any questions? Talk to a Specialist today.