Compact and extremely thin imaging devices are being used for compact and thin electronic devices such as mobile phones and PDAs (Persona Digital Assistants). As image sensors used in these imaging devices, solid-state imaging elements such as CCD-type image sensors and CMOS-type image sensors are known. Over recent years, the increase of pixels in imaging elements is in progress, and resolution and performance have been enhanced. Further, in imaging lenses to form an object image on these imaging elements, in response to miniaturization of imaging elements, compactness is being required and this requirement tends to grow year by year.
As such an imaging lens used for an imaging device (hereinafter referred to also as a “camera module”) fitted into a portable terminal, a 3 plastic lens structure type and a 3 lens structure optical system of one glass lens and 2 plastic lenses are known (for example, refer to Patent document 1).
On the other hand, a method is proposed in which on a glass substrate of several inches, a large number of lens elements are simultaneously molded by a replica method and then the glass substrate (lens wafer) on which a large number of these lens elements have been formed is separated to mass-produce lenses. Lenses produced by such a production method are referred to also as wafer scale lenses. Three lens structure imaging lenses employing such wafer scale lenses are known (for example, refer to Patent Document 2 and Patent Document 3).