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Popular Lens Mounts Used in Embedded Vision

C mount lenses

When it comes to embedded vision technology, choosing the suitable lens mount is crucial for capturing high-quality images and unlocking the full potential of your devices.

With a wide array of lens mounts on the market, it can be challenging to determine which suits your specific needs.

This blog post aims to simplify the selection process by exploring popular lens mounts used in embedded vision and providing valuable insights to help you make an informed decision.

What is a Lens Mount?

The lens mount is a mechanical interface that securely attaches a camera lens to an imaging device, such as a sensor or camera module. This crucial component ensures proper alignment and positioning of the lens relative to the image sensor. Typically, the lens mount includes threaded screw holes, flanges, or other mechanisms that firmly attach the lens while maintaining precise alignment.

When it comes to lens mounts, there are different styles available. However, the most commonly used mounting styles in embedded camera applications are the screw threaded and bayonet types. The screw-threaded type gets its name from threading your lens onto the camera body. It provides a secure connection between the lens and the camera, ensuring stability during use. On the other hand, the bayonet type uses three to four tabs to lock a lens tightly in place.

Why is Choosing the Right Lens Mount in Embedded Vision Applications Important?

Choosing the right lens mount in embedded vision applications is important for several reasons:

  • Flexibility and lens adaptability: A widely used and standardized lens mount, such as S-mount or C-mount, allows lens adaptability and interchangeability. This lets you switch between lenses for different purposes without requiring substantial tweaks or alterations.

  • Application specifications: Different lens mounts are appropriate for various uses. A smaller lens mount, such as M12, may be more suitable if you require a tiny and lightweight embedded vision device, say an industrial handheld tablet. On the other hand, vision-based equipment with a large form factor, such as robots or tractors, may necessitate larger mounts, such as C-mount, provided it meets the other application requirements.

    Additionally, the quality and functionality the lens provides might determine the lens mount type. Most S-mount (M12) lenses are fixed focus, without additional capabilities such as iris control. C-mount lenses, on the other hand, offer higher quality and can be packaged with features such as motorized zoom and iris control.

  • Future purpose: Choosing an established and popular lens mount ensures future compatibility with various lenses and accessories. It also reduces the likelihood that the lens mount you select will become obsolete or unavailable.

  • Compatibility with image sensors: Various lenses are designed to accommodate specific sensor capacities. Using a lens mount corresponding to the sensor size guarantees that the lens’s image circle completely encompasses the sensor area. This prevents vignetting (the darkening of image boundaries) and keeps image luminance consistent across the frame.

  • Simple integration: Selecting a lens mount that matches the design and specs of the camera module might make the integration process more accessible. It eliminates the need for bespoke adapters or lens adjustments, saving time and effort during installation.

  • Budget-effective: Choosing a standard and widely available lens mount can save costs since compatible lenses and accessories are more widely available and reasonably priced.

Factors to Consider While Picking a Lens Mount for Your Application

Now that you understand what camera lens mount types are, let us learn the factors you need to consider while picking the lens mount for your application. They are as follows:

Mount Size and Flange Fistance

The mount size is the diameter of the lens mount thread, and the flange distance is the distance between the lens mount surface and the image sensor. These parameters determine how compatible the lens is with the sensor. A larger mount size permits a larger lens, allowing more light to reach the sensor. Nonetheless, mount size is not the only factor influencing lens design; flange distance is also crucial.

A shorter flange distance enables lenses to be positioned closer to the sensor, allowing for the development of shorter-focus lenses that are simpler and more cost-effective. In addition, a shorter flange distance enables the construction of more compact cameras than longer flange distances. The proper balance between mount size and flange distance is required for optimal optical image quality in embedded camera applications.

If you’re developing a surveillance camera module with a small form factor, an M12 lens mount with a brief flange distance may be appropriate. In this scenario, its small size and simplicity of integration would be advantageous.

Lens Flange Focal Length

Sensor Size and Resolution

The sensor size and resolution determine the area a lens must cover and the level of captured detail. Modern embedded vision applications frequently employ high-resolution sensors to satisfy stringent image quality requirements. Ensuring that the lens mount chosen can accommodate the desired resolution is essential. While an S-mount lens (also called an M12 lens, with a thread diameter of 12mm) is suitable for most sensors used in embedded vision, large sensors designed to achieve higher resolution or pixel size will need a C-mount lens.

At the same time, even the 1-inch (25.4 mm) diameter of the C-mount might not be enough in certain scenarios, which is when the F-mount becomes the optimal choice. In addition, the T-mount is superior to the C-mount for larger sensors and line scan cameras due to its substantially larger diameter. A larger sensor necessitates a lens that can cover the entire image area without compromising image quality.

Field of View (FOV)

The lens’s field of view is the extent of the scene it can capture. It is affected by both the sensor’s capacity and the lens’s focal length. C-mounts are more prevalent than S-mounts in applications that need a large field of view. 

A lens mount compatible with ultra-wide-angle lenses may be preferred in a robotics application that requires a wide-angle view. This would enable capturing a larger area without requiring extensive camera-to-subject distance.

Focal Length

Lens Focal Length

The focal length determines the lens’s magnification and the distance at which objects come into sharp focus. It affects the field of view and the capacity to photograph subjects up close or far away. The lens’s focal length determines the type of mount with which it is compatible.

For instance, a lens with a focal length of 50 mm requires a larger holder height, rendering it irreconcilable with an M12 holder. M12-mount/CS-mount lenses typically have reduced focal lengths.

A lens mount compatible with variable focal length lenses (zoom or varifocal lenses) could be selected for an embedded vision system that monitors production lines. This would allow the magnification to be adjusted to focus on specific aspects of the production process.

Focus

Some lens mounts provide manual or motorized focus adjustments, which can benefit applications requiring precise focusing. Choosing a lens-to-mount combination that assures the highest focus quality is essential. For instance, a lens mount compatible with motorized focus control may be chosen in a medical imaging system. This allows healthcare providers to remotely adjust the camera’s focus without physically interacting with it.

Compact Size

Compactness is critical in applications with limited space, such as a handheld retina scanner for example. When compactness is a priority, placing the sensor near the camera housing is critical.

Because of their reduced size and ubiquitous availability, developers prefer S-mount lens types over C/CS-mount lenses in most embedded vision applications. Consider the use of a body-worn camera by law enforcement officials. The lens mount should be small and lightweight to provide comfort and unobtrusiveness while capturing high-quality images.

Most Common Lens Mounts Used in Embedded Vision

S-mount

The S-mount, also called the M12 Mount, holds significant popularity within compact embedded vision devices such as handheld scanners and medical diagnostic devices.

Its compact dimensions render it a preferred choice for scenarios where spatial constraints are considered.

The S-mount lens system employs a screw-threaded mounting approach and finds frequent utilization in board-level cameras.

This mount type encompasses a 12mm metric thread diameter with a pitch of 0.5 mm (M12x0.5), with the “M” denoting metric dimensions measured in millimeters of the outer diameter.

C-mount

The C-mount is a well-established and widely adopted standard, particularly prominent in machine vision and industrial applications. C-mount lenses are widely utilized in robotics, automation, quality control, and surveillance systems due to their adaptability and seamless compatibility with a wide range of camera sensors.

The C-mount connection comprises an imperial thread with a one-inch diameter and 32 threads per inch. This resembles a metric thread, with dimensions comparable to M25.5 x 0.75 mm.

The rear focal distances of the C-mount and CS-mount connectors are an important differentiating characteristic. C-mount connectors have a fixed rear focal distance of 17.526 mm, exactly 5 mm more than CS-mount connectors. While a CS-mount lens cannot be used directly with a C-mount camera, a C-mount lens can be used with a CS-mount camera via a CS-mount adapter, typically a 5 mm spacer ring.

CS-mount

The CS-mount is similar to the C-Mount, except it has a shorter flange focal distance, making it appropriate for smaller sensors. CS-mount lenses are commonly used in security cameras and machine vision installations because they allow for compact designs without sacrificing optical quality. This lens mount has a flange focal distance of 12.5 mm and is the ideal standard for low-cost embedded vision applications.

The CS-mount’s specifications are nearly identical to the C-mount’s, except for a 5mm reduction in flange focal length. This makes CS-mount a viable solution for limited space, and the reduced focal distance allows for more streamlined designs without sacrificing optical quality.

Other Lens Mounts

The above three are the most popular in embedded vision today. But other lens mounts are less frequently used, such as:

F-mount

Nikon developed the F-mount, primarily used for photography and videography. Although it is less common in embedded vision, the F-mount is the optimal choice when Nikon lens compatibility is essential. It is especially important in high-end imaging systems and configurations where alignment with professional camera lenses is essential.

The F-mount is a bayonet-style mount system for Nikon SLR and DSLR cameras. This mount type has a 44mm diameter and a 46.5mm flange distance. The bayonet mechanism of the F-mount adds a layer of convenience, which manufacturers of large format cameras and line scan cameras appreciate greatly. F-mount is synonymous with Nikon’s SLR camera lens mount system, indicating its widespread adoption.

Scientific imaging and machine vision applications emphasizing high-resolution and line scan cameras benefit from the F-mount’s versatility. It excels in situations requiring compatibility with large matrix sensors, where its expansive format shines. The F-mount has been in active production for over half a century, making it the only SLR lens mount to reach this remarkable benchmark.

TFL & TFL-II Mount

TFL (Through-Focal-Length) and TFL-II mounts are less common in embedded vision systems but have significant applications in scientific and research imaging. Due to the larger diameter of these mounts compared to the common C-mount, they are ideally suited for high-precision and resolution situations. Their primary applications include microscopy, scientific instruments, and particular industrial inspection arrangements.

In contrast, the T-mount, known as the M42-mount, distinguishes itself from other mount-varieties. Sophisticated cameras predominantly employ it with large, high-resolution sensors. This mount type has a metric thread with a 42 mm diameter and 0.75 mm pitch (M42x0.75). This mount’s standard flange focal distance is 55 mm.

The TFL-mount was designed for APS-C (27.9mm) sensors, which are too large for a C-mount but too small for an F-mount. The TFL-mount possesses thread dimensions of M35x0.75mm and shares the same flange distance of 17.526mm as the C-mount. The TFL-mount provides the same durability as the C-mount but accommodates larger sensors, bridging the limitations of the F-mount.

C-mount and S-mount Cameras from TechNexion

Introducing TechNexion, the leading provider of cameras with C-mount and S-mount configurations. With our wide range of camera options, we cater to all your imaging needs.

Our C-mount cameras stand out with their standard C-mount lens interface. This widely used lens mount in the industry offers unmatched flexibility and compatibility with various lenses. On the other hand, our S-mount cameras are ideal for applications where space is limited or where a more streamlined and compact design is essential.

Whether in industrial automation, robotics, machine vision, surveillance, medical imaging, or any other industry, TechNexion’s C-mount and S-mount cameras offer options to meet your specific imaging requirements.

With our wide range of camera models and features, you can select the appropriate lens type that suits your needs perfectly. Check out our embedded vision solutions here

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