A radially symmetric phase mask composed of several annular zones with equal area (called APM) was designed based on the incoherent imaging theory from Fourier Optics. The phase of any ring equals minus of the phase function caused by certain defocus. Another circularly symmetric phase mask similar to the APM (called MQPM) was proposed, except for the different phase function deriving from the quartic phase mask (QPM). For MQPM, there are two differences from an existing phase mask: the selection of the phase parameters and the method to divide the phase mask. An optimization model was developed to obtain optimized parameters of the phase masks. Numerical evaluations show that both APM and MQPM are less insensitive to defocus than QPM, and the defocused optical transfer functions with two phase masks are symmetric about the in-focus plane in the axial direction.

No abstract

No abstract

PurposeFilm is an important recording medium in industry. How to ensure film quality is a problem, because the film is produced in a dark room. Aims to focus on this.Design/methodology/approachAn inspection system based on machine vision is presented which could assure illumination and imaging at 940 nm which is safe for film.FindingsAn objective evaluation is given using an image processing method and satisfactory results are obtained. Now, the inspection system is used by the biggest film company in China.Originality/valueThis work focuses on an important issue in film production.

Purpose -The brake connector of an automobile is one important part in the brake system. How to measure the matching surface quality is a problem, because the matching surface is a cone surface and has a deep aperture structure. Design/methodology/approach -A new measurement system is presented which could assure illumination and image with a special beam splitter. The worker could observe the matching surface by better image. Findings -More objective evaluation is given with image processing method. Research limitations/implications -Now, this measurement system is used by Toyota (Tianjin) company and satisfied result is obtained. Originality/value -This paper is an original work and focuses on an important issue in automobile production.