Polarization cameras in machine vision
Our polarization machine vison cameras are well-known in the industrial polarized camera market thanks to its use of the monochrome Sony-IMX250MZR image sensor. The portfolio has also recently included the IMX264MZR. Information that a typical line or area industrial camera cannot obtain is captured by industrial polarization camera systems. A two-dimensional analysis is carried out by a polarization camera. It gauges the light's polarization in both its direction and degree. Consequently, there are hardly any reflections from outside light sources in the finished image. For tasks like inspecting glossy and transparent products, a polarized camera is perfect.
Basic machine vision camera vs. polarization machine vision camera
The ensuing illustrations display an image obtained using a standard machine vision camera on the left, and an image obtained using our polarized camera on the right.
Glass inspection (scratch and stain)
These illustrations feature dust and dents on a uniform glass surface. Because there are variations in the degree of polarization, we can easily find scratches, stains, dust, and fingerprints.
Tablet filling inspection
Once again, the left image was taken using a standard industrial camera. Our polarization camera takes the correct picture. It is simple to determine whether or not the tablets are filled because of the variation in polarization levels between the tablet and the aluminum package.
Distortion inspection
Standard industrial camera on the left. Camera polarization on the right.
We can determine the direction of the plane's distortion as well as the distortions themselves using the information about the direction of polarization.
Removal reflection
Standard vision camera on the left image. Polarized camera on the right image.
Reflections can be eliminated by using polarization. The four-directional polarizer of the IMX250MZR and IMX264MZR can simultaneously eliminate reflections in multiple planes.
Do you want to know if your application would be a good fit for a polarization camera? Get in contact or continue reading.
How to use a polarization camera?
The operation of a polarization filter is depicted in the image below. Light beams are released by a light (yellow ray) (Black line). Each light beam is made up of orange and gray light waves, which have varying angles. Light waves with a specific angle—the gray waves in the image—are blocked by a polarization filter (the light gray stripes), while the right-angled light waves—the orange waves—pass through. Therefore, only light waves with the proper angle—orange waves—will strike the camera's lens and sensor. The direct reflected wave of a polarized light wave—the remaining orange waves after the polarization filter—remains polarized when it strikes a non-metallic or transparent object's surface, while the remaining polarized light wave becomes unpolarized in all directions.
The glare from reflective surfaces caused by the polarized reflected light can impede or completely prevent your machine vision system from detecting specific components of an object. It is possible to control this effect by using a polarizing filter. The camera's polarized filter will block polarized light while allowing unpolarized light to flow through. Because of the decreased glare and reflections, your vision system will have an easier time identifying flaws.
The principal of a polarization filter.
Example 1: Application for polarization camera
The first use case for polarization cameras is the capture of monochromatic objects, such as tomatoes. In certain applications, it can be challenging to identify surface flaws or separate different products (like tomatoes) using a normal vision camera. Conversely, polarized camera systems simplify this process by adding an extra layer of analysis that allows for the detection of surface variations in single-colored objects. For instance, conveyor belts that scan single-colored items, like tomatoes on a production line, could be equipped with polarized cameras.
Example 2: Application for polarized camera
Taking pictures of transparent objects is the second scenario in which a polarized camera could be useful. It can occasionally be challenging for normal vision camera systems to identify the features of transparent objects from a captured image. Specifically, because light's polarization changes as it passes through a translucent material. For current camera systems to identify the product correctly, the polarization parameters must be changed. Nonetheless, a polarization camera can automatically record the difference in light transmittance. Conveyor belts in a production line that move transparent products work well with polarized camera systems because they can identify stamped marks and detect the presence of foreign materials.
Specifications of the Sony IMX264MZR polarization camera
With a 3,45µm pixel size and a 5.02 Megapixel total resolution, our MER2-502-79U3M polarization camera employs the Sony IMX250MZR image sensor. A four-directional polarizer known as a polarizer filter is mounted on the image sensor's photodiode in the polarization camera. In other words, this polarized camera can take a four-directional picture in a single frame which determines the polarization angle and direction by calculating the intensity of each direction of polarization. The filter uses a 2x2 pattern in which a different angle filter is applied to each pixel. Only the portion of light perpendicular to the angle of the filter will pass when using polarized light.
Angles of the polarization filter
In summary, the properties of a polarization filter are as follows:
- Light passes through the filter at 0 degrees when it is blocked at a 90 degree angle.
- Light flows through the filter at a 45 degrees when it is blocked.
- Light passes through the filter at a 45 degrees when it is blocked at a 135 degree angle.
- Lastly, light passes through a 90 degrees when it blocks light at a degrees angle.
Our polarization camera model number is MER2-502-79U3M-POL. It features a 2/3" global shutter, 79 frames per second, a USB3 interface, a resolution of 2448(H)x2048(V), and a cell size of 3,45µm x 3,45µm.
Specifications of the Sony IMX264MZR polarization camera
With a 3,45µm pixel size and a 5.03 Megapixel total resolution, our MER2-503-36U3M polarization camera employs the Sony IMX264MZR image sensor. A four-directional polarizer known as a polarizer filter is mounted on the image sensor's photodiode in the polarization camera. In other words, this polarized camera can take a four-directional picture in a single frame which determines the polarization angle and direction by calculating the intensity of each direction of polarization. The filter uses a 2x2 pattern in which a different angle filter is applied to each pixel. Only the portion of light perpendicular to the angle of the filter will pass when using polarized light.
Angles of the polarization filter
In summary, the properties of a polarization filter are as follows:
- Light passes through the filter at 0 degrees when it is blocked at a 90 degree angle.
- Light flows through the filter at a 45 degrees when it is blocked.
- Light passes through the filter at a 45 degrees when it is blocked at a 135 degree angle.
- Lastly, light passes through a 90 degrees when it blocks light at a degrees angle.
Our polarization camera model number is MER2-503-36U3M-POL. It features a 2/3" global shutter, 36 frames per second, a USB3 interface, a resolution of 2448(H)x2048(V), and a cell size of 3,45µm x 3,45µm.
Various polarization camera sensors vs. Sony IMX polarization camera sensors
The polarizer is positioned on top of the chip lens layer in standard polarization camera sensors. In contrast, the Sony IMX250MZR / IMX264MZR sensor is positioned beneath the on-chip lens layer. The shorter distance between the photodiode and polarizer improves the incident angle and extinction ratio as a result. Additionally, polarization filters that are mounted on lenses are frequently used by vision integrators. Unlike our polarization camera with the Sony IMX250MZR / IMX264MZR, which can block and detect light in four angles simultaneously, this filter can only block polarized light from one angle.
GeT Cameras and polarization cameras?
Daheng Imaging featuring the Sony IMX264MZR image sensor has just released a polarization camera, in addition to one featuring the Sony IMX250MZR image sensor. Please get in touch with us if you believe your application needs a polarized camera. We would be pleased to assist you in choosing the ideal polarization camera.