Optical system and optical apparatus including optical system

Abstract

At least one exemplary embodiment is directed to an optical system which includes at least one first refractive optical element, which includes a solid material satisfying the following conditional expression (1), and at least one second refractive optical element, which includes a solid material satisfying the following conditional expression (2):−1.33×10−3×νd+6.7×10−1<θgF   (1)−1.63×10−3×νd+6.2×10−1>θgF   (2)where νd and θgF indicate the Abbe number and the partial dispersion ratio, respectively.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to optical systems and optical apparatuses including the optical systems.[0003]2. Description of the Related Art[0004]To date, optical systems having a short lens length (optical length; length from a first lens adjacent to an object to an image plane) have been demanded for optical apparatuses such as digital still cameras, video cameras, and projectors.[0005]In general, compact optical systems having a short lens length tend to suffer from a greater amount of aberration, in particular, a greater amount of longitudinal and lateral chromatic aberration, resulting in lower optical performance.[0006]In particular, the amount of chromatic aberration is increased in optical systems having a shortened lens length.[0007]Well-known optical systems include lens systems of a so-called negative-lead type having a lens unit with a negative refractive power disposed in the anterior position and a lens ...

AI Technical Summary

Benefits of technology

[0019]At least one exemplary embodiment is directed to an optical system capable of appropriately correct chromatic aberration, capable of being easily manufactured, and having high optical performance.

Problems solved by technology

In general, compact optical systems having a short lens length tend to suffer from a greater amount of aberration, in particular, a greater amount of longitudinal and lateral chromatic aberration, resulting in lower optical performance.

In particular, the amount of chromatic aberration is increased in optical systems having a shortened lens length.

Since optical systems of the negative-lead type have a lens unit with a negative refractive power in the anterior position, negative distortion can easily occur.

However, glass having a high refractive index generally has a high dispersion, and easily causes a greater amount of negative lateral chromatic aberration.

Moreover, it is very difficult to machine anomalous partial dispersion glass such as fluorite.

Furthermore, the specific gravity of the material is relatively large compared with that of other low-dispersion glasses without anomalous partial dispersion, and thus the entire lens system tends to be increased in weight.

Surfaces of anomalous partial dispersion glasses are easily damaged, and anomalous partial dispersion glasses having large diameters can be easily cracked with sudden temperature changes.

Thus, application of materials having anomalous partial dispersion to optical systems is limited.

Liquid materials as discussed in U.S. Pat. No. 4,913,535 require structures for hermetically containing the liquid materials, resulting in difficulties in manufacturing optical systems including such materials.

Also, it is difficult to apply the liquid materials to optical systems due to changes in refractive indices and dispersion characteristics according to temperature.

Images