Proposal of the most suitable lens for outer surface inspection of cylindrical containers such as PET bottles
1. External inspection methods for cylindrical containers, plastic caps, preforms, bottlenecks, screws and other threaded parts
When inspecting the outer surface of cylindrical containers and small parts for chips and cracks on the top and sides, to image the entire outer surface (top and sides), rotate the work (PET bottle) by taking an image from the side or diagonal. Alternatively, multiple cameras will be used to divide the circumference and take images. However, this requires space inside the device, and the time and effort required to prepare multiple cameras is also costly. There is also the problem of being out of focus. With the two models of special optical lenses from Opto Engineering, which we deal with this time, it is possible to simultaneously image the top and side surfaces without rotating the workpiece with a single camera. Therefore, it simplifies the space inside the equipment, shortens the inspection process, and reduces inspection costs.
2. Introduction to pericentric lenses
The PC SERIES is a pericentric lens with an angle that constricts the principal ray toward the workpiece, contrary to general optical systems. The central part becomes parallel from the top, and the oblique angle becomes stronger as you go to the peripheral part. The captured photograph looks like the side of the cylinder is opened. Imaging with only one optical system. There is no border between the center and the periphery of the photograph.
2-1. What is a pericentric lens?
By placing the entrance pupil position closer to the object side than the front lens surface, it is possible to focus on the top and sides of the subject (object plane) at the same time.
3. Introducing Catadioptric Lenses
The PCCD SERIES is an application of the Cassegrain optical system that combines two mirrors. The central part is the view from the normal lens from directly above. The side part is a bipartite optical system that combines two different optical systems with the Cassegrain optical system from obliquely above. The field of view indicated by the blue line in the schematic diagram below is taken with a normal (macro) optical system. The field of view of the red line is taken with a special (reverse macro) optical system applied to Cassegrain. Unlike the PC series, the PCCD series has a clear boundary between these two optical systems.
3-1. What is a Cassegrain optical system?
An astronomical telescope that is based on a reflecting telescope and incorporates a corrective lens to correct aberrations is called a catadioptric telescope. Catadioptric is a compound word of catoptric (reflective optics) and dioptric (refractive optics). Various methods have been devised by combining the base optical system and correction lens. The PCCD series is an application of the Cassegrain optical system.
