CN112179628A - Image space telecentric lens for optical measurement - Google Patents

Image space telecentric lens for optical measurement Download PDF

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Publication number
CN112179628A
CN112179628A CN202011052460.0A CN202011052460A CN112179628A CN 112179628 A CN112179628 A CN 112179628A CN 202011052460 A CN202011052460 A CN 202011052460A CN 112179628 A CN112179628 A CN 112179628A
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lens
equal
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image
optical measurement
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CN112179628B (en
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宋维涛
张擎天
王涌天
刘越
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Beijing Institute of Technology BIT
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Beijing Institute of Technology BIT
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0207—Details of measuring devices
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
    • G02B13/005—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having spherical lenses only
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/22—Telecentric objectives or lens systems

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Lenses (AREA)

Abstract

The invention provides an image space telecentric lens for optical measurement, which can be combined with some mechanical components to quantitatively detect the display performance of a head-mounted display. The invention relates to an image space telecentric lens for optical measurement, which adopts the design of 5 glass spherical lenses, a diaphragm is arranged in front of the first surface of the lens, the lens is similar to the image space telecentric design, the diameter of an entrance pupil can be adjusted within the range of 2 mm-10 mm, the adjustment range is similar to the adjustment range of a human eye pupil, the effective focal length of a system is 21.092mm, the F number is 2.1, the half field angle of the system is 10 degrees, and the system has better MTF within the full field range. Through a traditional optical design method, a lens with partial human eye characteristics, low cost and simple processing is designed, so that the lens is used for replacing human eyes to perform optical measurement.

Description

Image space telecentric lens for optical measurement
Technical Field
The invention belongs to the technical field of optical measurement, and particularly relates to an image space telecentric lens for optical measurement.
Background
The current virtual display device mainly uses a head-mounted display, the head-mounted display is designed according to the characteristics of human eyes, human eyes can see a virtual scene through the head-mounted display, but the display performance of the virtual display device (the head-mounted display) can only be roughly evaluated through own subjective feeling, and the depth and the field angle of the virtual scene cannot be accurately measured. The field angle, the angular resolution and the scene depth are very important indexes for evaluating the display performance of the head-mounted display, but a method for quantitatively detecting the performance indexes is lacked in the field.
Disclosure of Invention
In view of the above, the present invention provides an image-side telecentric lens for optical measurement, which can be combined with some mechanical components to quantitatively detect the display performance of a head-mounted display.
In order to achieve the above purpose, the technical solution provided by the present invention is as follows:
the invention relates to an image space telecentric lens for optical measurement, which comprises a diaphragm, a front lens group, a middle lens group and a rear lens group;
wherein, the front lens group is a positive refractive index lens group and comprises a first lens; the middle lens group is a negative refractive index lens group and comprises a second lens and a third lens; the rear lens group is a positive refractive index lens group and comprises a fourth lens and a fifth lens;
a diaphragm is arranged in front of the first lens; the size of the diaphragm can be adjusted within 2 mm-10 mm;
the focal lengths of the lenses in the lens have the following relations:
| f1/f | < 1 > or more and less than 1.5, | f23/f | < 1 > or more and less than 1.5, and | f45/f | < 0.5 and less than 1; the absolute value of f1/f is more than or equal to 1.5, the absolute value of f2/f is more than or equal to 0.5 and less than or equal to 1, the absolute value of f3/f is more than or equal to 0 and less than or equal to 1, the absolute value of f4/f is more than or equal to 1 and less than or equal to 2, and the absolute value of f5/f is more than or equal to 0 and less than or equal to 1;
wherein f denotes a focal length of the lens, f1 to f5 denote focal lengths of the first lens to the fifth lens, respectively, f23 denotes a focal length of the middle lens group, and f45 denotes a focal length of the rear lens group.
The third lens and the fourth lens are negative lenses, and the second lens and the fifth lens are positive lenses.
The abbe numbers of the third lens and the fourth lens are all smaller than 40, and the abbe numbers of the first lens, the second lens and the fifth lens are all larger than 40.
Wherein the F number of the lens is less than 2.2.
The surface types of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are all spherical surfaces, and the materials are glass.
Wherein, the incidence angle of the chief ray of the maximum field of view of the lens on the image plane is 3.76 degrees.
Wherein, the lens adopts a field design without vignetting.
Has the advantages that:
the invention relates to an image space telecentric lens for optical measurement, which adopts the design of 5 glass spherical lenses, a diaphragm is arranged in front of the first surface of the lens, the lens is similar to the image space telecentric design, the diameter of an entrance pupil can be adjusted within the range of 2 mm-10 mm, the adjustment range is similar to the adjustment range of a human eye pupil, the effective focal length of a system is 21.092mm, the F number is 2.1, the half field angle of the system is 10 degrees, and the system has better MTF within the full field range. Through a traditional optical design method, a lens with partial human eye characteristics, low cost and simple processing is designed, so that the lens is used for replacing human eyes to perform optical measurement. The lens is combined with some mechanical parts, so that the subsequent quantitative detection can be carried out on performance indexes such as the field angle, the angular resolution, the scene depth and the like of the head-mounted display, and the lens in the whole lens is designed by adopting a glass spherical surface, so that the processing cost is low, the difficulty is small, and the large-scale production can be carried out.
Drawings
Fig. 1 is a schematic view of a lens structure according to the present invention.
FIG. 2 is a schematic view of a lens structure with a diaphragm diameter of 2mm according to the present invention.
Fig. 3 is a schematic diagram of MTF curve distribution within a 20 ° field of view (full field angle) of the lens according to the present invention.
Detailed Description
The invention is described in detail below by way of example with reference to the accompanying drawings.
The terms to which the present invention relates:
1. MTF: the modulation transfer function is an important reference standard of the imaging quality of the lens;
2. f number: the f-number, is the ratio (f '/D) of the effective focal length f' of the system to the entrance pupil diameter D (diaphragm diameter).
The lens structure of the invention is shown in fig. 1, wherein numbers 1-6 respectively represent a diaphragm, a first lens, a second lens, a third lens, a fourth lens and a fifth lens, and number 7 is a system image plane.
The lens of the invention comprises a diaphragm 1, a front lens group, a middle lens group and a rear lens group.
Wherein, the front lens group is a positive refractive index lens group, comprising a first lens 2 (positive lens); the middle lens group is a negative refractive index lens group and comprises a second lens 3 (a positive lens) and a third lens 4 (a negative lens); the rear lens group is a positive refracting power lens group including a fourth lens 5 (negative lens) and a fifth lens 6 (positive lens).
The diaphragm 1 is arranged in front of the first lens 2, and has a diameter D of more than or equal to 2mm and less than or equal to 10mm, namely the maximum diameter of the diaphragm is 10mm, and the minimum diameter is 2 mm.
The surface types of the first lens 2, the second lens 3, the third lens 4, the fourth lens 5 and the fifth lens 6 are all spherical surfaces, and the materials are glass.
F denotes a focal length of the lens, f1 to f5 denote focal lengths of the respective lenses, f23 denotes a focal length of the middle lens group (a combined focal length of the second lens and the third lens), f45 denotes a focal length of the rear lens group (a combined focal length of the fourth lens and the fifth lens), wherein f1 denotes a focal length of the front lens group (a focal length of the first lens), and focal lengths of the respective lenses in the lens have the following relationships:
| f1/f | < 1 > or more and less than 1.5, | f23/f | < 1 > or more and less than 1.5, and | f45/f | < 0.5 and less than 1; the absolute value of f1/f is more than or equal to 1.5, the absolute value of f2/f is more than or equal to 0.5 and less than or equal to 1, the absolute value of f3/f is more than or equal to 0 and less than or equal to 1, the absolute value of f4/f is more than or equal to 1 and less than or equal to 2, and the absolute value of f5/f is more than or equal to 0 and less than or equal to 1.
The abbe numbers of the third lens and the fourth lens are less than 40, and the abbe numbers of the first lens, the second lens and the fifth lens are more than 40.
The F-number of the lens is less than 2.2.
The lens structure with a diaphragm diameter of 2mm is shown in fig. 2. The wavelengths adopted in the design are 486.1mm, 546.1mm, 587.6mm and 656.3mm, the full field angle is 20 degrees, the effective focal length of the whole lens is 21.092mm, and the F number is 2.1. By normalizing the parameters of the lens shown in fig. 1, the normalized effective focal length f' of the lens is 1mm, and the angle of view is 2 ω 20 °. The diaphragm 1 is used as the first surface, the number of the surface is 1, the analogy is repeated, the number of the image surface is 12, and the types of the surfaces and the curvature radius of the surface of the lens are shown in table 1.
TABLE 1 lens parameters
Figure BDA0002709972400000051
The lens adopts a field design without vignetting, so that the light rays of each field have uniform illumination on an imaging surface.
The incidence angle of the chief ray of the maximum visual field of the lens on the image plane is 3.76 degrees and less than 4 degrees, so that the whole lens is designed to be approximately image-space telecentric.
FIG. 3 shows the MTF curve distribution in the 20 ° field of view (full field angle) of the lens of the present invention, where the frequency range is 0-225 lp/mm, and it can be seen that the MTF of the lens at 100lp/mm can reach more than 0.3 and the MTF at 225lp/mm can reach more than 0.1 in the 20 ° field of view.
In order to simulate the change of the pupil size of a human eye, the invention puts a diaphragm in front of the first surface of the lens, the size of the system diaphragm can be adjusted within 2 mm-10 mm, the aberration of the whole system is better corrected through the combination of the front lens group, the middle lens group and the rear lens group, and the effect of approximate image space telecentricity is achieved, so that the lens can more accurately measure the photoelectric performance of the display equipment. And the lens has good MTF in the full field of view under the condition of fully adopting a glass spherical surface and the design of the F number of 2.1, and the resolution ratio is higher than the resolution ratio of a central concave area of human eyes, so the lens has partial characteristics of the human eyes and can replace the human eyes to detect the performance index of the head-mounted display.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. An image space telecentric lens for optical measurement is characterized by comprising a diaphragm (1), a front lens group, a middle lens group and a rear lens group;
wherein, the front lens group is a positive refractive index lens group and comprises a first lens (2); the middle lens group is a negative refractive index lens group and comprises a second lens (3) and a third lens (4); the rear lens group is a positive refractive index lens group and comprises a fourth lens (5) and a fifth lens (6);
the diaphragm (1) is arranged in front of the first lens (2); the size of the diaphragm can be adjusted within 2 mm-10 mm;
the focal lengths of the lenses in the lens have the following relations:
| f1/f | < 1 > or more and less than 1.5, | f23/f | < 1 > or more and less than 1.5, and | f45/f | < 0.5 and less than 1; the absolute value of f1/f is more than or equal to 1.5, the absolute value of f2/f is more than or equal to 0.5 and less than or equal to 1, the absolute value of f3/f is more than or equal to 0 and less than or equal to 1, the absolute value of f4/f is more than or equal to 1 and less than or equal to 2, and the absolute value of f5/f is more than or equal to 0 and less than or equal to 1;
wherein f represents the focal length of the lens, f 1-f 5 represent the focal lengths of the first lens (2) to the fifth lens (6), f23 represents the focal length of the middle lens group, and f45 represents the focal length of the rear lens group, respectively.
2. Image-side telecentric lens for optical measurements according to claim 1, characterized in that the third lens (4) and the fourth lens (5) are negative lenses and the second lens (3) and the fifth lens (6) are positive lenses.
3. Image-side telecentric lens for optical measurements according to claim 1, characterized in that the third lens (4) and the fourth lens (5) have abbe numbers that are each less than 40 and the first lens (2), the second lens (3) and the fifth lens (6) have abbe numbers that are each greater than 40.
4. Image-side telecentric lens for optical measurements according to claim 1, characterized in that the F-number of the lens is less than 2.2.
5. The image-side telecentric lens for optical measurement according to claim 1, wherein the first lens (2), the second lens (3), the third lens (4), the fourth lens (5) and the fifth lens (6) are all spherical in surface type and made of glass.
6. Image-side telecentric lens for optical measurement according to claim 1, characterized in that the angle of incidence of the chief ray of the maximum field of view of the lens on the image plane is 3.76 °.
7. Image-side telecentric lens for optical measurements according to claim 1, characterized in that the lens adopts a field-of-view design without vignetting.
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023123443A1 (en) * 2021-12-31 2023-07-06 歌尔光学科技有限公司 Detection lens for head-mounted display device, and detection method
WO2023123440A1 (en) * 2021-12-31 2023-07-06 歌尔光学科技有限公司 Detection lens for head-mounted display device and detection method
CN118068543A (en) * 2024-04-19 2024-05-24 南京信息工程大学 Long working distance high-resolution object space telecentric lens

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US20160062105A1 (en) * 2014-08-29 2016-03-03 Canon Kabushiki Kaisha Eyepiece lens, observation apparatus, and imaging apparatus including the same
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CN206378632U (en) * 2016-12-21 2017-08-04 歌尔科技有限公司 Doubly telecentric camera lens and its camera, video recorder, telescope and overlength zoom lens
CN108681033A (en) * 2018-05-22 2018-10-19 德伽智能光电（镇江）有限公司 A kind of optical lens
CN109739005A (en) * 2019-01-29 2019-05-10 上海鼎州光电科技有限公司 A kind of nearly eye detector lens
CN111367044A (en) * 2019-12-29 2020-07-03 北京理工大学 Human-simulated glasses head

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07281089A (en) * 1994-04-12 1995-10-27 Olympus Optical Co Ltd Photographing lens
CN1782773A (en) * 2004-12-03 2006-06-07 三星电机株式会社 Optical system for high resolution using plastic lenses
US20160062105A1 (en) * 2014-08-29 2016-03-03 Canon Kabushiki Kaisha Eyepiece lens, observation apparatus, and imaging apparatus including the same
CN106569318A (en) * 2016-09-30 2017-04-19 惠州萨至德光电科技有限公司 Optical imaging lens
CN206378632U (en) * 2016-12-21 2017-08-04 歌尔科技有限公司 Doubly telecentric camera lens and its camera, video recorder, telescope and overlength zoom lens
CN108681033A (en) * 2018-05-22 2018-10-19 德伽智能光电（镇江）有限公司 A kind of optical lens
CN109739005A (en) * 2019-01-29 2019-05-10 上海鼎州光电科技有限公司 A kind of nearly eye detector lens
CN111367044A (en) * 2019-12-29 2020-07-03 北京理工大学 Human-simulated glasses head

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023123443A1 (en) * 2021-12-31 2023-07-06 歌尔光学科技有限公司 Detection lens for head-mounted display device, and detection method
WO2023123440A1 (en) * 2021-12-31 2023-07-06 歌尔光学科技有限公司 Detection lens for head-mounted display device and detection method
CN118068543A (en) * 2024-04-19 2024-05-24 南京信息工程大学 Long working distance high-resolution object space telecentric lens

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