Time of Flight (ToF) vs Stereo Vision – Which is preferable?

Time of Flight, Stereo Vision

Over the recent ten years, 3D sensors have evolved into one of the most versatile and widespread types of sensors used in robotics. In many robotic applications, 3D sensing has assumed the lead for tasks including near-field object recognition and collision avoidance, surface and object inspection, and map development.

There are numerous 3D sensing methods available. The two most popular topics in this collection, Time of Flight (ToF) and Stereo Vision, as well as their distinctions, will each be covered in a different piece.

What is Time of Flight (ToF) Sensor?

Time of Flight (ToF) sensors emit infrared light from a small laser, which bounces off of any object before returning to the sensor. The sensor can calculate the distance between an object and itself based on the time delay between the light’s emission and its return to the sensor after being reflected by the item.

When using ToF cameras, a light source that can illuminate the entire picture must be present in order for the sensor to detect the depth of each point. Your range map will be the outcome of this, with each pixel encoding the distance to its corresponding point in the scene.

Since ToF projects light onto the scene rather than using ambient light as stereo vision does, it is an active approach. As a result, even in low light, a ToF camera is simple to use. These cameras are capable of processing at greater distances.

Benefits of Time of Flight Camera

  • ToF cameras have a small design and are simple to operate.
  • Higher precision and frame rates are available.
  • Compared to stereo vision, it offers a quick response time.
  • Both in dimly lit and brightly lit environments, it performs well.
  • ToF method is less dependent on mechanical alignment.
  • High Field of View, greater sensor resolution, and superior object classification are all features of 3D ToF cameras.

What is Stereo Vision?

The operation of stereo vision is identical to that of the eye. When both eyes are looking at the same thing, the distance between a human’s two eyes, which ranges from 60 to 70mm, causes one eye to capture a slightly different image than the other. The placement of the image that each eye sees makes a difference in most cases.

Similar to how the human eye sees, stereo cameras feature two lenses that are roughly 60mm apart and they likewise record slightly distinct images. The visual data will then be processed by a processor, much like a human brain, to produce a depth map.

Stereo vision is only appropriate for usage outside in well-lit areas because it can only utilize the ambient light of the surrounding area without utilizing any additional light, making it a passive technique. It would be difficult for a stereo vision camera to capture stereo elements of the scene if it is utilized in low light or if the image contains few textures. The stereo camera should have a powerful sensor to handle all the processing in order to send photos promptly at a better resolution. Additionally, stereo cameras often only function at close ranges (within 2m).

Benefits of Stereoscopic Vision

  • Humans are able to handle small objects thanks to stereoscopic vision.
  • It is beneficial to return threats and respond appropriately.
  • Gives one a keen awareness of reality.
  • Accuracy is made possible in several profiles, including the industrial sector.
  • Stereo Vision performs well in outdoor environments compared to Time of Flight (ToF) which gets affected by the sunlight wavelength.

Difference between Time of flight and Stereo vision

Principle Measures the transit time of reflected light from the target object Compares disparities of stereo images from two 2D sensors
Software Complexity Low High
Material Cost Medium Low
Depth(“z”) Accuracy Medium Low
Depth Range Scalable Limited
Low light Good Weak
Outdoor Weak Good
Response Time Fast Medium
Compactness Low Low
Power Consumption Scalable Low

How do we choose between ToF and Stereo Vision for an application?

Time of Flight (ToF) cameras are in the lead in the race to offer the highest 3D image quality, as evidenced by the comparison table above. Their primary differences are as follows:

  • To prevent issues like employing depth matching techniques on the host platform, depth data from ToF cameras are directly obtained from the module. ToF cameras produce higher-quality images because they rely on accurate laser lighting.
  • The depth range of ToF cameras can be adjusted based on the quantity of VCSELs that are employed for illumination.
  • Because of the ToF camera’s active and dependable light source, they perform better in low-light situations.
  • Due to the fact that the sensor and lighting can be positioned together, ToF cameras have a very compact form factor.

Stereo Vision is also not far behind in the race. There are application areas where the environment inhibits the performance of ToF sensors such as Outdoor environment, Lighting conditions with wavelength similar to the one used on ToF, and so on. In these cases, Stereo Vision is still primary solution model for depth measurement requirements.

Final Words

We sincerely hope that this blog post has aided in your comprehension of Time of Flight (ToF) vs. Stereo Vision, and you have found this guide to 3D sensors useful.

We at vadzo are well aware that creating a depth-sensing camera based on ToF is no easy task. Given that it involves variables like optical calibration, temperature changes, VCSEL pulse timing patterns, etc., the voyage may be challenging. Each of these could have an impact on depth accuracy. Regardless of how time-consuming these processes are, ToF is an efficient system if it is developed with a very long design cycle.

Vadzo Imaging has experience with development of depth measurement solutions that employ the below combinations

  • Stereo Vision
  • Stereo Vision with holographic LEDs
  • High Resolution Color camera with ToF Sensor
  • High Resolution Color camera with mmWave Sensor

If you’re currently working on a vision-enabled product like any industry-based product, please take a look at what we do at Vadzo. We can help you get your product to market faster, and keep it functioning more reliably upon deployment, too.

Should you have any queries, feel free to Contact Us