brief introduction

The introduction of powerful compact single board computers has given birth to exciting new product designs. In the application of miniaturization to optimize cost and / or efficiency, its utility is particularly obvious. In addition, the vision system can further reduce the overall size of the product and achieve operational flexibility by using a fully functional board level machine vision camera, while also supporting customized or non-standard optical components. Typical examples are: medical diagnosis, metrology, robotics, embedded vision, packaging and printing inspection, hand-held scanners, desktop laboratories, and other space constrained systems.

This paper covers several important aspects to consider when selecting an embedded visual camera, including functional groups, form factors and physical footprint, interface options, lens mount, software support, thermal management, and electromagnetic compatibility.

Shape factor and function group

When designing camera level imaging board, the camera designer should seriously consider the performance requirements. Many small board level cameras support only low resolution sensors, a small number of GPIO lines, and limited camera internal features. In contrast, many board level models of full-featured machine vision cameras are just standard cameras with their shells removed. While these cameras may achieve the desired imaging performance, they may not be much smaller than standard packaged models. This kind of camera often uses standard GPIO and interface connector, which is not suitable for embedded application because of its large volume. For example, a traditional industrial lock connector is the size of a blackfly s board level camera.

FLIR’s blackfly s board level camera is designed for embedded system as a whole. They are very compact in size, only 29mmx29mmx10mm, providing the same imaging performance and the full range of features of the packaged blackflys model, while the compact GPIO and interface connector save extra space. Another important advantage of FLIR embedded vision camera products is that all cameras with 1 / 3 “to 1.1” size sensors have good usability due to the same shape factor – multiple camera models adopt the same shape factor, which simplifies the development and upgrading of the system and future product variants.

Lens bracket

Board level cameras are an attractive option for customers who want to integrate non-standard optics or place image sensors as close to the target as possible. There is no fixed lens bracket for plate level camera, so designers can freely choose optical elements other than standard C, CS or s interface lenses commonly used in machine vision industry. This design is also suitable for biotechnological and laser beam analysis applications that usually do not require lenses. Another common application of board level cameras is to integrate the lens bracket into another product component, from which comes the name “embedded visual camera”. In addition, the lens bracket is directly integrated into the product shell by molding, which can effectively simplify the manufacturing and assembly, thus further reducing the cost. Installation accessories should also be purchased to evaluate plate level cameras without lens brackets. If the package model has the same sensors and functions as the board level model, they can be used as a development platform.

One of the most important factors in choosing the right lens mount option for a board level camera is the size of the sensor used. Typically, the s-bracket lens is designed for low resolution (usually less than 2MP) sensors 1 / 3 “or smaller. The CS bracket lens is designed for 1 / 3 “to 1 / 2” sensors. If the sensor size is 1 / 2 “or more, a C-bracket lens is preferred.

Thermal management

Packaged machine vision cameras rely on the surface area of the enclosure to dissipate heat from sensors, FPGAs, and other components. If there is no enclosure, there may be other design requirements for high-performance board level cameras to ensure that they operate within the recommended temperature range. In this case, providing enough heat dissipation is the key. The manufacturer usually provides the highest junction temperature for the highest temperature components. For FLIR blackflys cameras, the maximum junction temperature specified for the FPGA is 105 degrees Celsius (221 degrees Fahrenheit).

System designers must ensure that their thermal management solutions meet this metric. The size of the heat sink, the surface area of the rack on which the camera is mounted, or the type of active radiator required depends on the sensor, frame rate, operating environment, and the amount of camera image processing being performed. In order to facilitate the installation of the radiator on the camera, we recommend using heat dissipation paste on the thermal pad to reduce the stress of the plate on the camera as much as possible.

Shell design and rapid prototyping

In most cases, board level cameras are directly integrated into embedded vision systems / products without the need for enclosures. However, for applications where the camera is not integrated with a product and the interior is exposed to components, it may be necessary to prevent damage through the enclosure. In rapid prototyping, embedded system designers can easily design and print a camera shell with a 3D printer, or use a general plastic shell enough to hold the camera, and then install the camera in place through gasket and mounting bracket.

Interfaces and connectors

The first generation usb3.1 is an ideal interface for embedded systems. It can provide all kinds of computer functions from SBC. Direct memory access (DMA) keeps latency to a minimum without using a filter driver. The first generation usb3.1 also uses a single cable power supply and can provide data throughput up to 480MB / s, effectively simplifying the mechanical and electrical design.

An important goal of embedded system designers includes the miniaturization of existing designs. In this case, the maximum length of the cable is much less important than the volume of the cable and connector. Flexible printed circuit (FPC) cables are up to 30 meters long and support the first generation usb3.1. As the name implies, FPC cable refers to the cable that can be bent and twisted to adapt to tight packaging system. In addition, high quality locking connector and FPC shielded cable with locking lug ensure a highly secure and reliable connection.

However, usb3.1 interface has a potential drawback, its high-frequency signal will cause interference up to 5GHz to wireless devices (such as GPS signal). For applications that use such wireless frequencies, we also offer FLIR board level cameras with GigE interfaces.

Mipicsi is another universal interface used by many embedded motherboards. However, compared with USB, the complexity of Mipi protocol and driver may make the development more time-consuming. Low voltage differential signal (LVDS) based interfaces are also available and designed for direct connection to host side FPGA; however, each signal transmission channel requires two wires – a small but significant drawback in some applications.

Software support

Software support is an important factor to consider when choosing camera for embedded system. With the SDK supporting desktop and embedded systems, designers can easily develop visual applications through familiar tools, and easily deploy them to the selected embedded platform. FLIR’s spinnaker SDK supports windows and Linux desktop systems based on X86, x64 and ARM processors.

electromagnetic compatibility

If there is no shielding effect provided by the enclosure, the electromagnetic compatibility (EMC) of the board level camera will be different from that of the package model. All packaged FLIR machine vision cameras are EMC certified; however, board level cameras have not yet been certified. These board level cameras are embedded in other products / systems, so the finished product needs to be certified separately. In both applications, we recommend that they follow electromagnetic interference (EMI) management best practices as other electrical components.

conclusion

The innovation of embedded vision system by board level camera makes the design of compact and multi-functional innovative products more free and flexible. In addition to the factors presented in this article, pay attention to the use of high-quality sensors, optics and reliable components to make your embedded system adapt to the future. FLIR’s full range of board level cameras are designed for these applications with an industry-leading 3-year warranty. Our machine vision experts can help you choose the right imaging performance and shape factor levels for embedded systems.

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