If you’re using machine vision cameras, you’re most likely looking at as much detailed information as quickly as possible from your captured images. While some cameras can detect wavelengths beyond what our eyes can see (UV and IR), many applications focus on the visible range. So, how do you decide whether to use color or monochrome cameras for your vision application?
Sorting and grading by color
Typical uses of a color sensor include simple color grading and sorting products by color. It’s handy for sorting pills, labels, textiles, and paints according to their colors.
Color cameras use the same types of vision sensors as monochrome cameras, except their pixels are covered by either red, blue, or green filters. These filters help identify the colors present in the image by separating them based on wavelengths. The Bayer color filter, commonly used in color cameras, has twice as many green filters as red or blue ones.
Adding these filters decreases the number of electrons that ultimately reach the silicon and can be measured. Typically, adding these filters leads to a decrease in quantum efficiency of about 5-10% compared to an equivalent monochrome sensor.
Effects of color interpolation on image quality
In addition to dimming with a color filter, color interpolation creates a full-color image after processing by blending adjacent pixels. This typically results in resolution and sensitivity that is generally lower than monochrome image sensors of the same pixel count and size. Therefore, it’s advisable to use color image sensors only when color information is required for the application. [1]
Additionally, the color captured by your sensor can be influenced by the color of the wavelength of light you are applying to the subject. Carefully integrate and maintain lighting conditions to achieve the best image quality.
Unless you are doing a comparison that will be determined/confirmed and evaluated exclusively by color, a monochrome camera typically provides quicker and more accurate information.
Your choice between color and monochrome cameras depends on your project’s specific needs. While color sensors are great for tasks like sorting by color, they may sacrifice some resolution and sensitivity. Considering factors like lighting conditions and the necessity for color information will help you make the best choice for efficient and accurate image analysis.
[1] Sony Semiconductor Solutions Corporation
