A New Generation of Cameras for the Outdoor Imaging of Moving Targets

AZoSensors spoke to Corey Fellows, Director of Sales at Lumenera Corporation about their new P-Iris system, ITS applications and how it is an improvement on the functionality of the DC-Iris Series.

Who have Lumenera designed the P-Iris system for?

Lumenera designed the P-Iris lens connector into its cameras for systems that require remote control of the lens’ iris to further the camera’s light management abilities. More specifically, the intended users of P-Iris technology are systems that perform their imaging where the light levels can vary drastically, such as outdoors.

Which industries do you expect the Lumenera LtX45R cameras to benefit most?

Lumenera’s LtX45R series of cameras are particularly suited to outdoor applications where either the subject or the camera is moving. This means the cameras perform in industries like Intelligent Traffic Systems (ITS), Unmanned Aerial Vehicles (UAVs) and Aerial Survey, and Intelligent Security Systems.

In the ITS industry, they are ideally suited for high speed tolling due to their high framerates as well as red light and speed enforcement by triggering the camera through its general purpose input/output (GPIO). As mentioned previously, the camera’s high framerate allows for software triggering through its video feed, removing the need for external hardware to trigger the camera, such as the case for red light infractions. The camera could detect that a car has run a red light and record the infraction without the need of an external signal.

The P-Iris lens is useful in electronic traffic management, where the accurate imaging of high speed objects is a necessity.

For aerial imaging, these cameras are lightweight and energy efficient for systems where size, weight, and power are a concern. They are also quite sensitive in the near infrared (NIR) spectrum, making them ideal candidates for applications like precision agriculture, where Normalized Difference Vegetation Index (NDVI) data can be computed from images capturing the red and NIR spectral bands. Furthermore, the LtX45R family of cameras are well suited for creating orthorectified aerial images to create site surveys and 3D point clouds for inspection and analysis purposes.

Using a monochrome variant for Intelligent Security Systems will take further advantage of the high sensitivity of the Sony Pregius sensor as it will not have a colour filter array over the sensor and will, therefore, allow more light to reach each pixel. It can then also be used in conjunction with infrared lighting for night-time operation as the monochrome variant does not require a color-balancing IR-cut filter.

The camera can then operate 24 hours per day and feed high resolution data to the system where analytics-based decisions can be made to properly secure a site.

What different methods can cameras use to achieve a useful level of brightness?

Typical industrial cameras with fixed-iris lenses manage the scene’s brightness through exposure time or gain. Exposure time is the length of time for which the camera’s sensor is detecting the light from a given scene.

Gain on the other hand, is an analogue circuit that is built into the image sensor that scales up the pixels response to light during the exposure time. Increasing either of these settings will result in a brighter image.

What are the issues associated with each of the above methods?

In low light situations, longer exposure times or increased gain would be used. However, long exposure times lead to blurry images when the subject or the camera is in motion. Furthermore, the camera’s gain can only be increased to a certain level before it becomes too noisy to extract usable data.

Diagram illustrating the effect that changing the aperture has on an image.

How does automated technology like DC-Iris and P-Iris help towards making these problems obsolete?

Using a remotely variable iris introduces a third variable to the camera’s light management algorithm. Once the maximum gain and exposure times are reached, the camera can then open the lens’ aperture to let more light into the sensor.

How does P-Iris improve upon the functionality that DC-Iris delivers?

P-Iris uses a digitally-controlled stepper motor instead of a current-controlled motor that its predecessor (DC-Iris) used. A DC-Iris lens’s aperture was known to drift over time and struggled to maintain a particular f-stop value.

They are effective at fully opening or closing the iris, but struggled with mid-range aperture values. Since P-Iris uses a stepper motor, once the value is set, the aperture will not change until instructed by the camera.

What other benefits does P-Iris bring to the system’s optics?

Lenses are subject to aberrations when the aperture is opened or closed past a certain point. The exact point at which the aberrations start to appear will vary from lens to lens, but all lenses are subject to some degree of aberration.

When the iris is fully opened, spherical aberration is introduced into the image whereas when it is closed to its smallest possible setting, diffraction becomes an issue. Both aberrations reduce the sharpness of the image, making it look softer, which makes edge detection more difficult.

Since P-Iris uses a stepper motor with a large number of positions, the iris can be fine-tuned to avoid the values where diffraction and spherical aberrations are introduced, maintaining a sharply focused image. In other words, P-Iris can continue to vary the lens’ aperture while staying in the sweet-spot for image sharpness.

What Lumenera cameras are equipped with P-Iris?

Lumenera has equipped its complete family of Sony Pregius-based Global Shutter CMOS cameras, with the P-Iris connector.

The Lumenera LtX45R family of cameras includes: the Lumenera Lt345R (3.2 megapixel), the Lumenera Lt545R (5.1 megapixel), the Lumenera Lt945R (8.9 megapixel), and the Lumenera Lt1245R (12.4 megapixel).

The Lumenera Lt545R with P-Iris lenses.

What other features make the Lumenera LtX45R cameras state of the art?

The Lumenera LtX45R series of cameras leverage Sony's Pregius global shutter CMOS sensors. These cameras have exceptionally high framerates which allow the camera to be triggered through software via its own video feed.

They are also highly sensitive and have exceptionally low read noise, allowing them to use shorter exposure times and higher gain values without introducing too much noise into the image. These factors make them great candidates for outdoor applications where light conditions are most challenging.

Where can our readers find out more about Lumenera, P-Iris and the LtX45R camera range?

You can read more about P-Iris in our blog post, or watch our explainer video on P-Iris here. You can also reach out to us at [email protected].

About Corey Fellows

As the Director of Sales at Lumenera, Corey is responsible for strategic account management and OEM business development across the Americas.

Corey has extensive experience in the global digital imaging industry, and has helped to create custom and OEM imaging solutions for a wide variety of industrial markets including: transportation, factory automation, biometrics and unmanned systems.