CN101907764A - Projection helmet optical system and its projection objective lens, helmet display device using the system - Google Patents

Abstract

A projection objective lens for a projected helmet optical system, comprising a first refracting lens, a second refracting lens, a third refracting lens and a fourth refracting lens arranged in sequence and having the same optical axis; between the four refracting lenses There is a gap; a diffraction element is also arranged between the second positive lens and the third positive lens. The projection objective lens of the present invention has relatively simple structure and small volume. The invention also provides a projected helmet optical system and a helmet display device using the system.

Description

Projection helmet optical system and its projection objective lens, helmet display device using the system

technical field

The invention relates to the field of optical technology, and specifically designs a projection objective lens of a projection helmet optical system. The invention also relates to a projection helmet optical system and a helmet display device using the system.

Background technique

Projected helmet-mounted displays (Head Mounted Progective Displays, HMPDs) are a new type of helmet-mounted display, which can give the correct "occlusion" of real objects and virtual objects in virtual reality and augmented reality environments, limit information to a specific space, and achieve multiple Effects such as complementary interference in the user environment. Compared with eyepiece-based head-mounted displays, the system can achieve small size and mass, large field of view, and small optical distortion.

FIG. 1 is a schematic diagram of an optical system of a conventional projection head-mounted display.

Please refer to FIG. 1 , the optical system of the projection helmet display includes a microdisplay 2 , a projection objective lens 3 , a beam splitter 5 , and a retroreflective screen 4 . The micro-display 2 and the beam splitter 5 are separately arranged on the optical axis of the projection objective lens 3, and are located on both sides of the projection objective lens 3. The retroreflective screen 4 is arranged on an axis perpendicular to the optical axis of the projection objective lens 3, and the beam splitting surface of the beam splitter 5 is also at an angle of 45° to the axis.

When working, the image on the microdisplay 2 is formed after passing through the projection objective lens 3, and the formed image is projected at the position of the projected image 1 through the transfer function of the beam splitter 5. Due to the reflection of the retroreflective screen 4 , the imaged light is reflected back to the beam splitter 5 and reaches the exit pupil 6 through the beam splitter 5 . The image displayed on the microdisplay can be seen by observing at the exit pupil 6.

FIG. 2 is a schematic diagram of a projection objective lens of the optical system of the above-mentioned projection head-mounted display. As shown in Figure 2, the projection objective lens includes a first positive lens 3-1, a second positive lens 3-2, a first negative lens 3-3, and a second negative lens 3-8 from the object plane to the image plane direction. , the fourth positive lens 3-6 and the fifth positive lens 3-7. Wherein, the optical axes of all the above-mentioned lenses are coaxial. The first positive lens 3-1 and the second positive lens 3-2 are meniscus-shaped, with the convex surface facing the object plane, and the first negative lens 3-3 is also meniscus-shaped, with the convex surface facing the object plane . There is an air gap between the first negative lens 3-3 and the second positive lens 3-2. The second negative lens 3-8 is a doublet lens with a convex surface facing the image side, and includes a negative lens 3-4 and a positive lens 3-5. The fourth positive lens 3-6 is a meniscus lens, and its convex surface also faces the image side. The fifth positive lens 3-7 is a biconvex lens.

The above-mentioned projection objective lens is a simple refraction projection system, and includes multiple lenses, which makes the entire projection objective lens larger in volume and complex in structure, and it is necessary to further improve it.

Contents of the invention

The invention provides a projection objective lens applied to a projection helmet optical system. The projection objective lens of the invention has a relatively simple structure and a small volume. The invention also provides a projected helmet optical system and a helmet display device using the system.

The present invention provides a kind of projection objective lens used for projection helmet optical system, comprising the first refraction lens, the second refraction lens, the third refraction lens and the fourth refraction lens which are arranged in sequence and have the same optical axis; There are gaps between the refractive lenses;

A diffractive element is further arranged between the second positive lens and the third positive lens.

Optionally, the four refracting lenses are positive meniscus lenses;

And the concave surfaces of the first refracting lens and the second refracting lens face the same direction, the concave surfaces of the third refracting lens and the fourth refracting lens face the same direction, and the first refracting lens and the second refracting lens The concave surface is opposite to the concave surfaces of the third refracting lens and the fourth refracting lens.

Optionally, the gap between the refracting lenses is air or its medium.

Preferably, the diffraction element is a single-layer diffraction element or a double-layer diffraction element,

Preferably, the diffraction element is a double-layer diffraction element;

The double-layer diffractive element includes a first transmission element and a second transmission element with periodic convex-concave micro-engraving structures on one side; the convex-concave micro-engraving structures of the two transmission elements have the same convex-concave period;

The sides of the first transmission element and the second transmission element provided with the convex-concave micro-engraving structure are oppositely arranged, and the protrusions of the two micro-engraving structures are opposite to the protrusions, and the depressions are opposite to the depressions.

Optionally, a side surface of the first transmission element and the second transmission element opposite to the convex-concave micro-carving structure is a plane, a spherical surface or an aspheric arc surface.

optional,

Recess depth of the first transmissive element:

Recess depth of the second transmissive element:

Wherein, n ₁ (λ ₀₁ ) and n ₁ (λ ₀₂ ) are the refractive indices of the first transmission element when the design wavelengths are λ ₀₁ and λ ₀₂ respectively; n ₂ (λ ₀₁ ) and n ₂ (λ ₀₂ ) are The refractive indices of the second transmission element when the design wavelengths are λ ₀₁ and λ ₀₂ respectively; k ₀₁ and k ₀₂ are wave numbers.

Optionally, materials of the first transmission element and the second transmission element are FCD ₁ and FD ₆ respectively.

Optionally, when the two wavelengths are designed to be 400nm and 700nm respectively, H ₁ =10.9um and H ₂ =5.9um.

Optionally, the materials of the first transmission element and the second transmission element are respectively SF6 and Sk52, or are respectively Ge and ZnSe.

The present invention also provides a projection helmet optical system, including the projection objective lens described in any one of the above technical solutions.

The present invention also provides a projected helmet display device, including the projected helmet optical system.

Compared with the prior art, compared with the existing projection objective lens, the projection objective lens of the present invention has fewer optical elements and a simpler structure, which is beneficial to reduce the overall volume and weight of the entire projection objective lens.

Preferably, the diffraction element of the projection objective lens of the present invention is a double diffraction element, so that the optical system comprising the double-layer diffraction element can be applied to a head-mounted display in the visible light range, and has a higher diffraction efficiency when observing in the visible light range ; Thereby, the contrast and authenticity of the image plane can be effectively improved; and the requirements for use of the helmet-mounted display device in virtual display and visualization training can be met.

Description of drawings

Fig. 1 is the schematic diagram of the optical system of existing a kind of projection head-mounted display;

Fig. 2 is a schematic diagram of a projection objective lens of the optical system of the projection head-mounted display shown in Fig. 1;

3 is a schematic diagram of an embodiment of a projection objective lens for a projection helmet optical system of the present invention;

FIG. 4 is a schematic diagram of a double-layer diffraction element applied in the embodiment shown in FIG. 3 .

Detailed ways

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described here, and those skilled in the art can make similar extensions without violating the connotation of the present invention, so the present invention is not limited by the specific implementations disclosed below.

The projection objective lens used in the projection helmet optical system of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 3 is a schematic diagram of an embodiment of the projection objective lens used in the projection helmet optical system of the present invention.

Please refer to Fig. 3, the projection objective lens of the embodiment of the present invention comprises 5 optical components, and the direction from object to image is successively the first refraction lens 7-1, the second refraction lens 7-2, the diffraction element 7-5, the first refraction lens A triple refraction lens 7-3 and a fourth refraction lens 7-4. The four refracting lenses are arranged on the same optical axis. The double-layer diffractive element 7-5 is arranged above the optical axis. A certain gap is provided between the above five optical components, and the gap may be an air gap or may be filled with a medium.

The first refracting lens 7-1, the second refracting lens 7-2, the third refracting lens 7-3 and the fourth refracting lens 7-4 are all positive meniscus lenses. Please continue to refer to FIG. 3, the first refracting lens 7-1 has an opposite convex surface 7-1a and a concave surface 7-1b, and the second refracting lens 7-2 has an opposite convex surface 7-2a and a concave surface 7-2b; the third refracting lens 7-3 has an opposite convex surface 7-3a and a concave surface 7-3b; the fourth refracting lens 7-4 has an opposite convex surface 7 -4a and concave surface 7-4b.

The concave surface 7-1b of the first refracting lens 7-1 and the concave surface 7-2b of the second refracting lens 7-2 face the same direction; the concave surface 7-3b of the third refracting lens 7-3 The concave surface 7-4b of the fourth refracting lens 7-4 faces the same direction, and the concave surfaces of the first refracting lens 7-1 and the second refracting lens 7-2 are in the same direction as the third refracting lens 7-3 and the second refracting lens 7-3. The concave surfaces of the quadruple refraction lens 7-4 are oppositely arranged.

The first refracting lens 7-1 and the fourth refracting lens 7-4 are separately arranged on both sides of the projection objective lens for correcting the spherical aberration of the projection objective lens; the second refracting lens 7-2 and the third refracting lens The concave surfaces of the lens 7-3 are oppositely arranged, and are arranged inside the first refracting lens 7-1 and the fourth refracting lens 7-4, and are used to eliminate field curvature of the projection objective lens. The materials of the four refracting lenses and the radii of curvature of the concave and convex surfaces can be designed according to actual needs, and will not be described here.

The diffractive element 7-5 is arranged between the second refracting lens 7-2 and the third refracting lens 7-3, and is used to correct the positional dispersion of the system. As shown in Figure 3.

The diffractive element 7-5 may be a single-layer diffractive element, that is, only one diffractive optical element. However, since the single-layer diffractive element only responds to light of a single wavelength, that is, the diffraction efficiency is higher at the design wavelength, and when the wavelength deviates from the design wavelength to both sides, the diffraction efficiency of the main diffraction order of the diffractive optical element gradually decreases , and the diffraction energy of the sub-diffraction order will diffuse on the image plane of the main diffraction order, thereby affecting the contrast of the image plane. Therefore, the optical system of a single-layer diffractive element is only suitable for narrow wavelength bands.

In order to overcome the problem that the optical system of a single-layer diffractive element is only applicable to a narrow band, the diffractive element may also be a double-layer diffractive element. That is, two diffractive optical elements are included. FIG. 4 is a schematic diagram of a double-layer diffraction element in this embodiment.

Please refer to FIG. 4, the double-layer diffraction element 7-5 includes a first transmission element 7-5-1 and a second transmission element 7-5-2; and a periodic convex-concave micro-engraving structure is provided on one side of the two transmission elements; For example, a convex-concave micro-engraving structure is provided on one side 7-5-1b of the first transmission element 7-5-1, and a convex-concave micro-engraving structure is provided on one side 7-5-2b of the second transmission element 7-5-2. The convex-concave micro-engraved structures of the two transmission elements have the same period. Specifically, the convex-concave micro-engraving structure may be a grating structure, and the grating structures of the two elements have the same grating period.

The side 7-5-1b of the first transmissive element 7-5-1 and the side 7-5-2b of the second transmissive element 7-5-2 are oppositely arranged and closely attached together. Moreover, when they are close together, the protrusions of the micro-carving structures on both sides are opposite to each other, and the depressions are opposite to each other. The recessed areas of the first transmissive element 7-5-1 and the second transmissive element 7-5-2 may be filled with a dielectric material, or may not be filled with a dielectric, just an air gap.

In addition, the side 7-5-1a of the first transmission element 7-5-1 and the side 7-5-2a of the second transmission element 7-5-2 are the side opposite to the micro-engraved structure, and the side It can be a plane, or a spherical or aspheric arc structure.

The micro-engraved structures of the first transmission element 7-5-1 and the second transmission element 7-5-2 have different depths, and different depths can be set according to the response wavelength of the two transmission elements. For example, after determining the substrate materials with different dispersion coefficients of the two transmission elements, the depths of the micro-engraved structures (that is, the depth of the depression) of the two transmission elements can be obtained as follows:

Recess depth of the first transmissive element:

Recess depth of the second transmissive element:

Wherein, n ₁ (λ ₀₁ ) and n ₁ (λ ₀₂ ) are the refractive indices of the first transmission element 7-5-1 when the design wavelengths are λ ₀₁ and λ ₀₂ respectively; n ₂ (λ ₀₁ ) and n ₂ (λ ₀₂ ) The refractive index of the second transmission element 7-5-2 when the design wavelengths are λ ₀₁ and λ ₀₂ respectively; k ₀₁ and k ₀₂ are wave numbers.

That is to say, after selecting the base material of the two diffractive elements according to the requirement of the corresponding wavelength, the recess depths of the two transmissive elements can be obtained. The depth of the depression and the base material determine the response of the modified double-layer diffraction element to different wavelengths.

For example, when the designed response wavelength is in the visible light spectrum range, that is, the response wavelengths are 400nm and 700nm respectively, the materials of the first transmission element 7-5-1 and the second transmission element 7-5-2 are FCD ₁ and FD ₆ respectively When , the H ₁ =10.9um, H ₂ =5.9um. That is, choose FCD ₁ and FD ₆ as the base material, H ₁ = 10.9um, H ₂ = 5.9um as the depression depth of the micro-engraved structure, then the optical system including the double-layer diffractive element can be applied to the helmet-mounted display in the visible light range. When observed in the visible light range, it has a high diffraction efficiency. Specifically, the diffraction efficiency can be greater than 90%, so that the problem that the single-layer diffraction element is only applicable to a narrow band can be overcome.

In addition, the materials of the first transmissive element 7-5-1 and the second transmissive element 7-5-2 may also be SF6 and Sk52, or Ge and ZnSe respectively.

Compared with the existing projection objective lens, the projection objective lens in the above embodiment has the reduced number of optical elements and simplified structure, which is beneficial to reduce the overall volume and weight of the entire projection objective lens; With good response, the range of wavelengths used is expanded, and the diffraction efficiency is also greatly improved, thus effectively improving the contrast and authenticity of the image plane. The utility model can meet the requirements for using the helmet-mounted display device in virtual display and visual training.

The projection objective lens in the above embodiments can be used as an optical element in a projection helmet optical system, and the optical system can also be applied in a projection helmet display device to form a display device with high contrast and fidelity.

Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be based on the scope defined by the claims of the present invention.

Claims (12)

1. projection objective that is used for projection helmet optical system is characterized in that: comprise set gradually, first refractor with optical axis, second refractor, third reflect lens and fourth reflect lens; Has the gap between described four refractors;

Between described second positive lens and the 3rd positive lens, also be provided with diffraction element.

2. projection helmet optical system according to claim 1 is characterized in that: described four refractors are the falcate positive lens;

And the concave panel of described first refractor and second refractor is towards identical, the concave panel of described third reflect lens and fourth reflect lens is towards identical, and the concave panel of the concave panel of described first refractor, second refractor and third reflect lens, fourth reflect lens is oppositely arranged.

3. projection helmet optical system according to claim 1 is characterized in that: the gap between the described refractor is air or its medium.

4. according to claim 1 or the 2 or 3 described projection objectives that are used for projection helmet optical system, it is characterized in that: described diffraction element is individual layer diffraction element or double-deck diffraction element,

5. according to claim 1 or the 2 or 3 described projection objectives that are used for projection helmet optical system, it is characterized in that: described diffraction element is double-deck diffraction element;

Described double-deck diffraction element comprises that a side is provided with periodically first transmissive element and second transmissive element of convex-concave microscopic carvings structure; The convex-concave microscopic carvings structure of two transmissive elements has the identical convex-concave cycle;

Described first transmissive element and second transmissive element are provided with convex-concave microscopic carvings structure one side and are oppositely arranged, and the projection of two microscopic carvings structures is relative with projection, and depression is relative with depression.

6. the projection objective that is used for projection helmet optical system according to claim 5 is characterized in that: a side relative with convex-concave microscopic carvings structure of described first transmissive element and second transmissive element is plane, sphere or aspheric surface arcwall face.

7. the projection objective that is used for projection helmet optical system according to claim 5 is characterized in that:

The cup depth of first transmissive element:

The cup depth of second transmissive element:

Wherein, n ₁(λ ₀₁) and n ₁(λ ₀₂) described first transmissive element is respectively λ at design wavelength ₀₁And λ ₀₂The time refractive index; n ₂(λ ₀₁) and n ₂(λ ₀₂) described second transmissive element is respectively λ at design wavelength ₀₁And λ ₀₂The time refractive index; k ₀₁And k ₀₂Be wave number.

8. the projection objective that is used for projection helmet optical system according to claim 7 is characterized in that: the material of described first transmissive element and second transmissive element is respectively FCD ₁And FD ₆

9. the projection objective that is used for projection helmet optical system according to claim 8 is characterized in that: when design two wavelength are respectively 400nm and 700nm, and described H ₁=10.9um, H ₂=5.9um.

10. the projection objective that is used for projection helmet optical system according to claim 7 is characterized in that: the material of described first transmissive element and second transmissive element is respectively SF6 and Sk52, perhaps is respectively Ge and ZnSe.

11. a projection helmet optical system is characterized in that: comprise aforesaid right requirement 1 to 10 arbitrary described projection objective.

12. a projection helmet mounted display device is characterized in that: comprise the described projection helmet of described claim 10 optical system.

Images