Lens module

Abstract

The invention discloses a lens module, which consists of four optical lenses. The lens module comprises a first optical lens group and a second optical lens group. The first optical lens group comprises first optical lenses with negative diopter. Each first optical lens is provided with a first surface and a second surface, wherein the first surface faces an amplification side; the second surface faces a reducing side; at least one of the first surface and the second surface is a non-spherical surface. The second optical lens group is configured between the first optical lenses and the reducing side, and moreover, the second optical lens group comprises second optical lenses, third optical lenses and fourth optical lenses which are arranged in sequence from the amplification side to the reducing side. The diopter of the second optical lenses, the diopter of the third optical lenses and the diopter of the fourth optical lenses are positive, negative and positive in sequence, and moreover, at least two of the second optical lenses, the third optical lenses and the fourth optical lenses respectively comprise non-spherical surfaces. Moreover, the effective focal length of each third optical lens is f3, and the refractive index is Nd3, whereas the effective focal length of each fourth optical lens is f4. Moreover, the lens module meets the formula as follow: the absolute value of f3/(f4*Nd3) is greater than 0.45 but is less than 1.2.

Description

technical field [0001] The invention relates to a lens module, and in particular to a lens module composed of four lenses. Background technique [0002] With the advancement of technology, micro-projection lenses (Projection Lens) have gradually become one of the mainstream in the market. Generally speaking, an important feature of a micro projector is that the light source is changed from a traditional high-pressure mercury lamp (UHP) to an environmentally friendly and power-saving LED lamp. A small numerical aperture (F number) means the use of a large aperture lens. Along with the enlargement of the aperture, the size of the lenses in the lens head will also be relatively larger, thus, the aberration of the imaging image will increase sharply, and thus the difficulty in optical design will be greatly increased. [0003] At present, most of the existing technologies use aspherical lenses to correct the aberration, or increase the number of lenses to overcome the above-me...

AI Technical Summary

Problems solved by technology

Along with the enlargement of the aperture, the size of the lens in the lens head will also be relatively larger, thus, the aberration of the imaging picture will increase sharply, so the difficulty in optical design will be greatly improved

[0003] At present, most of the existing technologies use aspherical lenses to correct aberrations, or increase the number of lenses to overcome the above-mentioned problems, but this will be contrary to the purpose of reducing manufacturing costs

In addition, the use of too many aspherical lenses is likely to increase tolerance sensitivity, and too many lenses will make the entire system unable to meet the compactness (Compact), and it is difficult to truly reduce the size of the overall optics

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