KR100280320B1 - Ccd potical system using a holographic optical element lens - Google Patents

Abstract

The present invention relates to a CD camera optical system using a holographic optical element lens, comprising: a first lens having a positive refractive power and a convex object side surface sequentially from the object side; A second lens having an image side concave and having negative refractive power; A third lens having both sides concave, negative refractive power, and a holographic optical element; A fourth lens having both sides convex and positive refractive power; The lens is made of a fifth lens having convex and positive refractive power, and by using a holographic optical element lens, a camera optical system having a high resolution can be realized with a small number of lenses, and an increase in size and weight of the entire optical system is prevented. , Small size and light weight.

Description

CD camera optical system using holographic optical element lens {CCD POTICAL SYSTEM USING A HOLOGRAPHIC OPTICAL ELEMENT LENS}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a Chagre Coupled Device (CCD) camera optical system using a holographic optical element (HOE) lens, and more particularly, to a holographic optical element lens, i.e., diffraction / refraction, in a digital still camera. The present invention relates to a CD camera optical system using a hologram optical element that implements a camera optical system using five lenses using a hybrid lens.

In general, seven lenses are required to implement a CD camera optical system having a focal length f of 8 mm and an F number of 1.4. The seven lenses used in this optical system are spherical lenses.

As described above, the conventional CD optical system composed of seven lenses has an MTF of 0.18 at 20 lps / mm on the axis and 0.43 (Tangential) at 20 lps / mm at a field of 0.7, 0.25 (Sagital). )), An optical system for color CDs with 0.55 (tangential) and 0.47 (sagittal) at 20 lps / mm on the edge of FOV, with a total length of 410,000 pixels of hydrogen at 8mm diagonal.

However, since at least seven lenses are required to implement the conventional CD optical system, the size of the entire optical system is increased, which makes it difficult to miniaturize.

In addition, at least 8 to 9 lenses must be used to realize a high resolution CD optical system of 1 million pixels or more using a conventional CD optical system.

An object of the present invention is to solve the above-mentioned disadvantages, and to realize an optical system having excellent resolution even with a small lens configuration using a holographic optical element lens in a CD camera optical system.

In addition, an object of the present invention is to provide a CD camera optical system using a hologram optical element having a high resolution and good aberration characteristics composed of five lenses including a diffraction / refraction hybrid holographic optical element lens.

1 is a lens configuration of a CD camera optical system using a holographic optical element lens according to an embodiment of the present invention,

2 is a cross-sectional view of a holographic optical element lens according to the embodiment of the present invention,

3 is a spot diagram of a CD camera optical system using a holographic optical element lens according to an exemplary embodiment of the present invention;

4 is an aberration diagram of the CD camera optical system using the holographic optical element lens according to the embodiment of the present invention;

5 is another aberration diagram of the CD camera optical system using the holographic optical element lens according to the embodiment of the present invention;

6 is another aberration diagram of the CD camera optical system using the holographic optical element lens according to the embodiment of the present invention.

A configuration of the present invention for achieving the above object comprises: a first lens having a positive refractive power and a convex object side surface sequentially from the object side; A second lens having an image side concave and having negative refractive power; A third lens having both sides concave, negative refractive power, and a holographic optical element; A fourth lens having both sides convex and positive refractive power; The object side is made of a fifth lens having convex and positive refractive power.

The above-described configuration will be described in detail with reference to the accompanying drawings the most preferred embodiment that can be easily implemented by those skilled in the art to which the present invention pertains.

1 is a lens configuration of a CD camera optical system using a holographic optical element lens according to an embodiment of the present invention,

2 is a cross-sectional view of a holographic optical element lens according to the embodiment of the present invention,

3 is a spot diagram of a CD camera optical system using a holographic optical element lens according to an exemplary embodiment of the present invention;

4 is an aberration diagram of the CD camera optical system using the holographic optical element lens according to the embodiment of the present invention;

5 is another aberration diagram of the CD camera optical system using the holographic optical element lens according to the embodiment of the present invention;

6 is another aberration diagram of the CD camera optical system using the holographic optical element lens according to the embodiment of the present invention.

As shown in FIG. 1, the structure of the CD camera optical system using the holographic optical element according to the exemplary embodiment of the present invention includes a first lens 1 in which the object side surface is convex and has positive refractive power. And a second lens 2 having a concave image and having negative refractive power, a third lens 3 having both concave and negative refractive power, a fourth lens 4 having both convex and positive refractive power, The fifth lens 5 has a convex side of the object and a positive refractive power.

In this embodiment of the invention, the third lens 3 is a holographic optical element lens.

The operation of the CD camera optical system using the holographic optical element lens according to the embodiment of the present invention by the above configuration is as follows.

In the present invention, in order to reduce the number of lenses of the conventional optical system, the optical path of the light is changed using the diffraction phenomenon of the light, instead of changing the optical path of the light by using the refraction of the light as in a general lens. To this end, a diffractive / refractive composite hologram optical element lens is used to diffract light.

By using the above-described holographic optical element lens, the optical system according to the embodiment of the present invention can reduce the number of lenses of the whole optical system, while maintaining the same optical system paraxial value (focal length, F number, angle of view, image size, etc.) and better resolution. And an optical system having a focal length of 8 mm and an F-Never 1.4 used for a color CD having a diagonal length of 8 mm and a number of pixels of 410,000 pixels.

In addition, the optical system according to the embodiment of the present invention is a high resolution optical system that can be applied even when the number of pixels of the CD is about 1 million pixels.

As such, it is possible to reduce the number of lenses and to easily implement high resolution as compared with the conventional optical system due to the optical principle peculiar to the following holographic optical element lenses.

In general, a holographic optical element lens is a diffractive optical element having a shape as shown in FIG. 4, where F is a focal length of the holographic optical element lens, D is a diameter of the holographic optical element lens, and d Is the thickness of the diffractive surface of the holographic optical element lens, and r _n is the radius from the lens center of the nth surface profile.

As shown in FIG. 2, when light waves are incident on a holographic optical element lens having a spherical symmetry, the light waves interfere with a fine surface profile engraved on the holographic optical element lens, thereby causing an image plane located at a focal length F. It is formed.

The wavefront equation of the optical wave that is newly formed due to interference between the surface profile of the holographic optical element lens and the incident plane wave is as follows.

Φ (r) = (2π / λ ₀ ) × (A ₁ r ² + A ₂ r ⁴ + A ₃ r ⁶ + ...)

In the above, λ ₀ represents the design center wavelength of the holographic optical element lens, and A _1, A ₂ , and A ₃ represent the coefficients of the wavefront equation.

Coefficient of the wave front in the equation is given at the time of forming the optical wave front by the diffractive optical element in hologram surface for the design center wavelength, in A ₁ is -1 / 2F for the holographic optical element lens having a focal length F, A ₂ , A ₃ , etc. are given as Zernike Polynomial coefficients related to the formation of light waves by the holographic optical element surface. In the case of A ₁ is the paraxial value associated with the focal length of the lens surface of the holographic optical element.

When the optical wave of the diffracted light formed by Equation 1 is focused on the image plane by interpolation interference, the wavelength of the optical wave, as shown in FIG. It is controlled by the holographic optical element lens so as to have an optical path difference by an integer multiple of lambda.

In this case, the axial radius Rn of the fine zone of the holographic optical element lens surface is determined as follows.

Example values of the CD camera optical system using the holographic optical device according to the embodiment of the present invention having the above characteristics are shown in Table 1 below.

Face number Radius of curvature Thickness and distance C.A radius of curvature Lens material One 13.45 3.00 7.5 2 29.11 0.67 7.3 SF11 First lens 3 29.99 1.00 6.4 4 5.35 12.00 4.9 SSK4 Second lens 5 iris 2.00 3.75 iris 6 -25.604 1.00 5.3 7 12.307 3.20 5.3 SF57 Third lens 8 -9.485 0.10 5.3 LaKn13 Fourth lens 9 12.103 3.00 5.7 10 -84.592 13.24 5.6 SK52 Fifth lens 11 Top 3.98

In the camera optical system configured as described above, the optical wavefront associated with the micro surface profile of the holographic optical element lens is expressed according to Equation 1 as follows.

Φ (r) = (2π / λ ₀₎ × ⁽² + 0.0001956r 0.0000634r ⁴ - ⁶ 0.0000011r)

In this case, the focal length F ₀ by the diffractive surface of the holographic optical element lens is -2556.233 mm, and the design center wavelength λ ₀ is set to 587 nm.

Meanwhile, the depth of each zone profile of K.E. is given as follows.

N (λ ₀ ) represents the refractive index with respect to λ ₀ .

When the light waves are diffracted by the deflective plane of K.E., the difference in the optical paths in each zone causes the difference by an integral multiple of the design center wavelength.

Spot diagrams using a CD optical system according to an embodiment of the present invention having a focal length of 8 mm and an F number of 1.4 applied to KE are shown in FIG. The distribution of the geometrical aberration is as shown in the attached Figures 4-6.

In the embodiment of the present invention, the third lens 3 is K.E., and its shape data is shown in Table 2 below.

One Number of zones 55 2 John's first 1.3731 mm 3 John's Last 5.30mm 4 Minimum zone width 0.0346mm 5 Zone depth 0.691 μm 6 Number of levels 8

The optical system according to the present invention can be applied not only to a cd camera, but also to an optical system of a device requiring small size and light weight, such as a goggle night vision mirror or a helmet mounted display (HMD).

As described above, according to the exemplary embodiment of the present invention, a camera optical system having a high resolution may be implemented with a small number of lenses by using a holographic optical element lens.

In addition, due to the excellent chromatic aberration correction effect of the holographic optical element lens, the basic paraxial calculation values such as the focal length, the F number, and the angle of view of the optical system have the same resolution as before, but the camera optical system having better resolution and aberration characteristics can be realized. have.

In addition, by implementing a high-resolution optical system with five lenses, by reducing the number of lenses to prevent the increase in the size and weight of the entire optical system, it provides a compact and lightweight effect.

Claims (3)

From the object side sequentially, A first lens having an object side surface convex and having positive refractive power; A second lens having an image side concave and having negative refractive power; A third lens having both sides concave, negative refractive power, and a holographic optical element; A fourth lens having both sides convex and positive refractive power; A fifth lens having a convex side of the object and positive refractive power A cd camera optical system. The method of claim 1, A focal length F of 8 mm and a C-number camera optical system with an F number of 1.4. The method of claim 1, Said third lens is a diffraction / refraction composite lens of the CD camera optical system.

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