How do vision systems work

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If you do not allow these cookies then some or all of these services may not function properly. Vision sensors perform inspections first by locating the part in the image, then by looking for specific features on that part. Once the field of view FOV is set, an operator can run vision tools within the entire range of the target to inspect multiple features for their presence, completeness, or orientation—all in a single image. And even though data output is binary, data in aggregate can be used downstream to improve processes and perform diagnostics on a particular work cell.

The power of an In-Sight vision system with the simplicity and affordability of a vision sensor. Ultra-compact vision systems ideal for applications where machine space is a premium.

Full-featured, powerful vision system with a compact footprint and unique, modular design. Cognex representatives are available worldwide to support your vision and industrial barcode reading needs. Proper lighting makes inspection faster and more accurate. Poor lighting is a major cause of failure in machine vision inspection systems.

In general, the available or ambient light is poor lighting and will not work. For example, the overhead lights in a factory can burn out, dim or be blocked, and these changes might be interpreted as part failures by the machine vision system. Selecting the proper lighting requires some knowledge and experience.

Our distributors and lighting vendors will be able to do an analysis of the parts you want to inspect and recommend proper lighting. Staging usually is mechanical. It also usually includes a Part-in-Place sensor that tells the machine vision system when a part is in front of the camera.

This sensor is usually a simple light source and photoelectric detector, for example. Staging is required for three reasons:. The lens gathers the light reflected or transmitted from the part being inspected, and forms an image in the camera sensor.

The proper lens allows you to see the field-of-view you want and to place the camera at a convenient working distance from the part. To pick the proper lens you will first need to know the field-of-view FOV and the working distance. The FOV is the size of the area you want to capture. Here is a typical example: If the part to be inspected is 4" wide and 2" high, you would need a FOV that is slightly larger than 4", assuming your staging can position the part within this FOV.

In specifying the FOV you have to also consider the camera's "aspect ratio" - the ratio of the width to height view. In the previous example, the 4" x 2" part size would fit in a aspect ratio, but a 4" x 3. The working distance is approximately the distance from the front of the camera to the part being inspected. A more exact definition takes into account the structure of the lens.

From the FOV and working distance and the camera specifications, the focal length of the lens can be estimated. The focal length is a common way to specify lenses and is, in theory, the distance behind the lens where light rays 'from infinity' parallel light rays are brought to a focus.

Common focal lengths for lenses in machine vision are 12 mm, 16 mm, 25 mm, 35 mm and 55 mm. When the calculations are done, the estimated focal length will probably not exactly match any of these common values. We typically pick a focal length that is close and then adjust the working distance to get the desired FOV. There are other important specifications for lenses, such as resolution image detail - depends on the camera and the lens , the amount and type of optical distortion the lens introduces and how closely the lens can focus.

The camera contains a sensor that converts light from the lens into electrical signals. To understand how a machine vision system works, it may be helpful to envision it performing a typical function, such as product inspection. First, the sensor detects if a product is present. If there is indeed a product passing by the sensor, the sensor will trigger a camera to capture the image, and a light source to highlight key features.

In order to process an image, computer software must perform several tasks. First, the image is reduced in gradation to a simple black and white format. Next, the image is analyzed by system software to identify defects and proper components based on predetermined criteria. Machine vision systems, also called automated vision systems or vision inspection systems , consist of several components that are common to most systems.

Although each of these components serves its own individual function and can be found in many other systems, when working together they each have a distinct role in a machine vision system. Our related guide Machine Vision System Hardware Selection provides additional information regarding the selection of the elements of a machine vision system.

Machine vision systems can be comprised of discrete elements or may be integrated together into one unit such as a smart camera that combines the functions of the individual elements into a single package. Regardless of whether a discrete or integrated system is used, the effectiveness of the machine vision system is also dependent on the nature of the parts being evaluated.

The more consistent the part placement and orientation, the better the performance the system can be expected to deliver. The selection of lighting for use in a machine vision system should be made with the goal of maximizing the contrast for whatever features are of interest to be measured or observed while minimizing the contrast of all other features of the part.

Achieving this goal may require varying the amount of light used intensity , the style of lighting dome vs. Lighting options include LED lighting and strobe lights for capturing images with fast shutter speeds. The optical components in a machine vision system are typically a lens or a camera , which integrates the lens with other elements such as the sensor.

The lens selection will establish the field of view, which is the two-dimensional area over which observations can be made. The lens also will determine the depth of focus and the focal point, both of which will relate to the ability to observe features on the parts being processed by the system. Lenses may be interchangeable or may be fixed as part of some designs that use a smart camera for the optical system. Lenses that have a longer focal length will provide higher magnification of the image but will reduce the field of view.

The selection of the lens or optical system for use is dependent on the specific function being performed by the machine vision system and by the dimensions of the feature under observation.

Color recognition capability is another characteristic of the optical system element. Sensors used in machine vision systems serve to capture the light from the optical system and convert that into a digital image. Sensors use CMOS or CCD technology to capture the light and convert that to a set of pixels that show the presence of light in the different areas of the original part being observed.