In the world of vision systems, the ability to accurately read and interpret images is paramount.   


One crucial aspect of image-based reading is determining the appropriate resolution required to capture and process the desired information effectively.   


Pixels per module (PPM) is a common criterion used to gauge whether a camera has sufficient resolution to read a specific code.   


In this article, we will delve into the basics of PPM, its significance, and how it is calculated.  


Understanding pixels per module  


PPM, or pixels per module, refers to the number of pixels required to cover a single cell or module of a code. It acts as a metric to assess the camera’s resolution in relation to the desired application.   


By calculating PPM, one can determine if the camera possesses enough resolution to accurately read the code.  


Calculating PPM  


The calculation of PPM involves several factors: the camera’s resolution in one direction, the Y-field of view in millimetres, and the code size in millimetres.   


Let’s break down the calculation step-by-step:  


Determine the camera’s resolution: Start by identifying the camera’s resolution in the desired direction. For instance, if the camera has a resolution of 752 pixels horizontally, that would be the value used in the calculation.  


Measure the Y-field of view: Next, determine the Y-field of view in millimetres. This measurement represents the vertical area covered by the camera’s lens. For example, if the Y-field of view is 78 mm, this is the value to be used.  


Measure the code size: Measure the size of the code in millimetres, specifically the dimension related to the modules. For instance, if the code size is 12 mm, this would be the value utilised.


Calculate the number of modules: Determine the number of modules within the code. If the code has 22 modules, this would be the appropriate value.  


Perform the PPM calculation: Divide the camera’s resolution by the Y-field of view and then divide the code size by the number of modules.Finally, multiply these values together to obtain the PPM. In the given example, the calculation would be (752 pixels / 78 mm) * (12 mm / 22 modules) = 5.26 PPM.  


Importance of PPM  


PPM serves as a crucial parameter when selecting a vision system for a specific application. Insufficient resolution can lead to inaccurate code reading, which can impact productivity, quality control, and overall operational efficiency.   


By calculating PPM, users can ensure that the camera resolution aligns with the requirements of their application, thus maximising reading accuracy and reliability.  


Simplifying the PPM calculation  


While the manual calculation of PPM may seem complex, there are tools available to simplify the process. Configurator apps or image-processing software running on image-based readers can quickly and accurately calculate PPM.   


These user-friendly tools eliminate the need for manual calculations and provide immediate feedback on whether the camera’s resolution is sufficient for a given application.  


Pixels per module (PPM) is a fundamental concept in the field of vision systems. By understanding PPM and how it is calculated, users can determine the appropriate camera resolution for their application.   


This knowledge is crucial for ensuring accurate and reliable code reading, which in turn impacts productivity and quality control. As technology advances, the availability of user-friendly tools further simplifies the calculation process, making it accessible to a broader range of users. 


By embracing the basics of PPM, businesses can harness the full potential of vision systems and optimise their operations.