High-end cameras typically require an internal light shield to block stray light. When using polyethylene terephthalate (PET) material with an antistatic, high‑opacity coating and directly die‑cutting it, the inner hole’s cross‑section leaves a shiny cut surface, leading to noticeable glare, halos, and ghosting. To thoroughly address this issue, Yamagata Optics, in collaboration with camera manufacturers, successfully developed in 2014 a light shield with a recessed V‑shaped or U‑shaped cross‑section at the inner edge, effectively resolving the problem of lens stray light.

In 2021, Yamagata Optics launched another innovative next-generation process that replaces single-sided chamfering: the double-sided pointed chamfer process.

As the era of large-aperture cameras places ever-higher demands on pixel count, Yamagata Optics has significantly enhanced the precision and stability of thin-film die-cutting, enabling camera manufacturers to flexibly select from a variety of processes—such as etched matte finishing, single-sided chamfering, and double-sided chamfering—to address issues related to light transmission and stray light in imaging sensors.

    In light of the two aforementioned matte‑finishing processes, our company developed a double‑sided chamfering process in 2022. This process delivers the same visual effect as single‑sided chamfering while also providing the corrosion‑induced matte finish, offering the significant advantage of seamless assembly without the need for orientation. It has already been validated on several high‑end models and is now in mass production. Below is a comprehensive stray‑light simulation comparison between Mylar sheets finished with conventional matte processing and those treated with the double‑sided chamfering process.

Laser irradiation test

  The mylar sheet is placed horizontally, exposed to the test environment, with an image sensor positioned directly beneath it at a fixed distance. A high-intensity light source illuminates the internal apertures of the mylar sheet from multiple angles, and the resulting changes in the captured images are observed. The condition corresponding to the strongest scattered-light intensity is taken as the threshold for stray‑light suppression under these circumstances. Because the laser intensity is extremely high, it maximally amplifies the stray‑light contribution introduced by the mylar sheet, thereby enabling a more precise comparison of the stray‑light suppression performance of the two processes.

Lighting test

      Assemble the mylar sheet into a complete test lens, and illuminate it with a point source or collimated light of specified irradiance from various external angles. Observe the changes in the captured images, and define the condition at which scattered light is strongest as the stray‑light suppression limit for that scenario. Compared with laser‑illumination testing, this method provides a more accurate assessment of stray‑light behavior under real‑world operating conditions.

Under laser‑testing conditions, the double‑sided chamfered mylar sheet exhibits superior stray‑light suppression compared to a standard anti‑stray‑light mylar sheet; its surface does not introduce excessive stray light, whereas the standard version produces pronounced arcuate, line‑like stray‑light artifacts. However, under illumination‑testing conditions, the stray light introduced by the double‑sided chamfered mylar is virtually indiscernible, while the standard anti‑stray‑light mylar generates significant stray light on its surface, severely degrading the lens’s optical performance. Consequently, the double‑sided chamfered mylar offers markedly better stray‑light suppression, and the chamfering process reduces the effective area of critical lens surfaces, substantially mitigating stray‑light effects, thereby ensuring superior imaging quality and enhancing the overall performance of camera products.