An ultra-wide angle camera lens is provided. The lens includes, from an object side to an image side: a first lens with negative refractive power, an image-side face of the first lens being concave; a second lens with negative refractive power, an image-side face of the second lens being concave; a third lens with positive refractive power, an object-side face of the third lens being convex; a fourth lens with positive refractive power, an image-side face of the fourth lens being convex; and a fifth lens with negative refractive power, an image-side face of the fifth lens being concave. The lens satisfies: 0.05<f/f1<0; and 1.2<ImgH/f<2, in which, f represents an effective focus length of the ultra-wide angle camera lens, f1 represents an effective focus length of the first lens L1, and ImgH is half of a diagonal line of an effective pixel region on an imaging face.

An ultra-wide angle camera lens is provided. The lens includes, from an object side to an image side: a first lens with negative refractive power, an image-side face of the first lens being concave; a second lens with negative refractive power, an image-side face of the second lens being concave; a third lens with positive refractive power, an object-side face of the third lens being convex; a fourth lens with positive refractive power, an image-side face of the fourth lens being convex; and a fifth lens with negative refractive power, an image-side face of the fifth lens being concave. The lens satisfies: 0.05<f/f1<0; and 1.2<ImgH/f<2, in which, f represents an effective focus length of the ultra-wide angle camera lens, f1 represents an effective focus length of the first lens L1, and ImgH is half of a diagonal line of an effective pixel region on an imaging face.

The present invention provides an eyepiece. The eyepiece is composed of one lens, which comprises a first surface and a second surface that are opposite, wherein, the first surface is a curved surface, and the second surface is a Fresnel structure surface; the Fresnel structure surface is formed by a plurality of annular zones that are sequentially arranged, to form a sawtooth surface, and each of the annular zones is formed by a working surface and a non-working surface, the working surface is an aspheric surface, and the non-working surface is a straight bevel; and the eyepiece satisfies the following conditional expression: 85<FOV<130, and 0i5; wherein, FOV is a maximum angle of view of the eyepiece, and i is the angle between the non-working surface of the ith annular zone and the optical axis.

The present invention provides an eyepiece. The eyepiece is composed of one lens, which comprises a first surface and a second surface that are opposite, wherein, the first surface is a curved surface, and the second surface is a Fresnel structure surface; the Fresnel structure surface is formed by a plurality of annular zones that are sequentially arranged, to form a sawtooth surface, and each of the annular zones is formed by a working surface and a non-working surface, the working surface is an aspheric surface, and the non-working surface is a straight bevel; and the eyepiece satisfies the following conditional expression: 85<FOV<130, and 0i5; wherein, FOV is a maximum angle of view of the eyepiece, and i is the angle between the non-working surface of the ith annular zone and the optical axis.

An ocular optical system adapted for an imaging ray of a display image being entered an observer's eye through the ocular optical system to form an image is provided. The ocular optical system includes a first lens and a second lens arranged in order from an eye-side to a display-side along an optical axis. Each of the first lens and the second lens has an eye-side surface and a display-side surface. A maximum distance between the display-side surface of the first lens and the eye-side surface of the second lens parallel to a direction of the optical axis is less than 5 millimeters, and the ocular optical system satisfies: 6DLD/EPD20. DLD is a diagonal length of the displayed image corresponding to a single pupil of the observer, and EPD represents an exit pupil diameter of the ocular optical system.

An ocular optical system adapted for an imaging ray of a display image being entered an observer's eye through the ocular optical system to form an image is provided. The ocular optical system includes a first lens and a second lens arranged in order from an eye-side to a display-side along an optical axis. Each of the first lens and the second lens has an eye-side surface and a display-side surface. A maximum distance between the display-side surface of the first lens and the eye-side surface of the second lens parallel to a direction of the optical axis is less than 5 millimeters, and the ocular optical system satisfies: 6DLD/EPD20. DLD is a diagonal length of the displayed image corresponding to a single pupil of the observer, and EPD represents an exit pupil diameter of the ocular optical system.

In order to obtain an observation optical system which has high optical performance while having a wide field of view, and can easily reduce variation of aberration at the time when an eye relief has changed, the present invention provides an observation optical system which is used for an observer to observe an image displayed on an image display surface, and includes in order from an observation side to an image displaying surface side: a first lens having a positive refractive power; a second lens having a negative refractive power; and a third lens having a positive refractive power, wherein a focal length f1 of the first lens, a focal length f2 of the second lens and a focal length f3 of the third lens are each appropriately set so as to satisfy the conditional expression of: $0.40<\frac{f1}{\sqrt{-f2f3}}<0.80.$

In order to obtain an observation optical system which has high optical performance while having a wide field of view, and can easily reduce variation of aberration at the time when an eye relief has changed, the present invention provides an observation optical system which is used for an observer to observe an image displayed on an image display surface, and includes in order from an observation side to an image displaying surface side: a first lens having a positive refractive power; a second lens having a negative refractive power; and a third lens having a positive refractive power, wherein a focal length f1 of the first lens, a focal length f2 of the second lens and a focal length f3 of the third lens are each appropriately set so as to satisfy the conditional expression of: $0.40<\frac{f1}{\sqrt{-f2f3}}<0.80.$

An installation for improving the binocular visual field includes a structural element located at a distance from the observer equal to or greater than the observer's interpupillary distance. The structural element is provided with at least one through aperture, in which an optical system is applied that has two convergent lenses, between which a divergent lens is centrally interposed, the distance between each of the convergent lenses and the central divergent lens being such as to make the optical system of a neutral afocal type.

A door peep viewer system allows small stature individuals, children, and those confined to a wheelchair or motorized scooter, the ability to use the peep-hole located within a home's front or rear door. This increases home safety by permitting the identification of someone requesting entry to the home. Once the door peep viewer system is mounted to the door, the lower portion adjustably extends to suit the needs of the person using the device. Persons of average height are still capable of using the peep-hole because the top portion is designed with a two-way see through scope. The door peep viewer system can be used in residential homes, or commercially in hotel rooms.