摘要(英) |
This paper presents a projection lens designed for HMD (Head Mounted Displays) systems, including VR, AR, and MR. The distinctive feature of this lens is that the stop is designed on the exit surface of the lens and it to output collimated light. This design allows for seamless integration with subsequent waveguide systems. To consider cost factors, all lens have been designed and manufactured using spherical glass materials. This paper focuses on the image quality of the projection lens as the main research direction. It not only designs a high-quality projection lens but also explores the relationship between optical distortion and TV Distortion. Furthermore, it conducts practical tests on the image quality of the finished lens. Lastly, this paper also investigates a method for evaluating the image quality of the lens. The aim of this study is to provide a high-quality projection lens that improves the image effects of HMD systems such as VR, AR, and MR.
This lens design is divided into two variants: a FOV 30 degree design and a FOV 50 degree design. The FOV 30-degree projection lens consists of nine glass spherical lens and two flat glass plates. Since this lens design is intended for use with reflective LCOS panels, the two flat glass plates are polarizing beam splitter(PBS) and panel protection glass, respectively.
The entrance pupil diameter of this lens is 14 mm, and the effective diameters of all lens are smaller than 23 mm. The lens has an effective focal length of 16.443 mm, an F-number of 1.1745, an MTF greater than 0.583 at 28 lp/mm. A lateral chromatic aberration smaller than one pixel size of the sensor, optical distortion below 2%, TV distortion below 1.49%, and Relative Illuminance greater than 82.05%. The lens design is manufactured and tested, resulting in a center field image quality of 33 PPD and a horizontal 0.7 field image quality of 23 PPD.Moving on to the FOV 50 degree projection lens design, it consists of nine glass spherical lens and one flat glass plate. This lens design is specifically intended for use with emissive OLED panels, with the flat glass plate serving as panel protection glass.The lens has an entrance pupil diameter of 10 mm, and the effective diameters of all lens elements are smaller than 20 mm. The lens has an effective focal length of 19.337 mm, an F-number of 1.9337, an MTF greater than 0.770 at 29 lp/mm. A Lateral Chromatic Aberration smaller than one pixel size of the sensor, Optical Distortion below 0.8%, TV Distortion below 0.35%, and Relative Illuminance greater than 64.48%.
This paper investigates a method for evaluating the image quality of a lens using the Intel RealSense D455 depth camera. Based on the specifications of the depth camera, the inverse magnification factor is derived using the object-image relationship. Subsequently, a Resolution Chart is designed, consisting of eight spatial frequency groups formed by three fields of view (0.5, 0.7, 0.9). The lens image quality is evaluated by capturing the Resolution Chart and determining the three maximum spatial frequency groups. Finally, the lens image quality is further assessed using the Resolution Chart with four fields of view (0.3, 0.5, 0.7, 0.9) and three spatial frequency groups. |
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