| 摘要: | 本文提出了一種用於VR、AR、MR等HMD系統的投影鏡頭。該鏡頭的特點是光圈設計在鏡頭的出光面，並能輸出平行光，使其能夠輕鬆與後續的導光系統對接。為了考慮成本因素，所有鏡片都採用了球面玻璃材料進行設計和製造。本文以鏡頭的影像品質為主要研究方向，不僅設計了投影鏡頭，探討了光學畸變和電視畸變之間的關係，還實際檢測了成品鏡頭的影像品質。最後本文還研究了一種鏡頭影像品質的檢測方法。本文目的在於提供一種高品質的投影鏡頭，以改善VR、AR、MR等HMD系統的影像效果。
此鏡頭設計分作全視角30度與全視角50度兩種設計，全視角30度投影鏡頭設計由九片玻璃球面鏡片與兩片平板玻璃所組成，由於此鏡頭設計用於反射式LCOS面板，因此兩片平板玻璃分別為偏振分光鏡(PBS)與面板保護玻璃。此鏡頭入瞳口徑為14 mm，所有鏡片的有效口徑皆小於23 mm，鏡頭有效焦距為16.443 mm，F-number為1.1745，MTF在28 lp/mm時大於0.583，橫向色差小於感測器一個畫素大小，光學畸變小於2%，電視畸變小於1.49%，相對照度大於82.05%，本鏡頭設計實際製造並檢測實體鏡頭其中心視場影像品質可達33PPD與水平方向左右0.7視場影像品質可達23PPD。接著是全視角50度投影鏡頭設計，則是由九片玻璃球面鏡片與1片平板玻璃所組成，此鏡頭設計用於自發光OLED面板，因此1片平板玻璃為面板保護玻璃。鏡頭入瞳口徑為10 mm，所有鏡片的有效口徑皆小於20 mm，鏡頭有效焦距為19.337 mm，F-number為1.9337，MTF在29 lp/mm時大於0.770，橫向色差小於感測器一個畫素大小，光學畸變小於0.8%，電視畸變小於0.35%，相對照度大於64.48%。
本文研究一種鏡頭影像品質的檢測方法，以Intel RealSense D455深度攝影機作拍攝實驗，根據深度攝影機規格利用物像關係式推算出逆向放大率，然後設計一Resolution Chart，其為3個視場(0.5、0.7、0.9)所組成之八個空間頻率組，透過實際拍攝此Resolution Chart，找出此鏡頭之三個最大空間頻率組，最後再以4個視場(0.3、0.5、0.7、0.9)三個空間頻率組之Resolution Chart檢測其鏡頭影像品質。
;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. |
