Projection Display Research Articles

Retinal projection display with realistic accommodation cue

Although retinal projection displays have the feature of being always in focus and no loss of image resolution, the lack of accommodation cue makes it difficult to perceive the depth correctly. In this paper, we proposed a retinal projection display system with realistic accommodation cue. The proposed system adds an optometric device to the conventional holographic optical element (HOE)-based retinal projection display. The optometric device detects the accommodation response of the human eyes to observe a real scene at different distances. According to the focused depth of the human eye, refocused images containing realistic focusing and defocusing information are generated through the light field refocusing technology. By establishing a focus depth-lookup table, the refocused images matching with the focused depth of human eye was presented to the human eye, so as to restore the retinal projection display with realistic accommodation cue. A proof-of-concept prototype based on the proposed structure was developed, and the experimental results presented retinal projection displays with realistic accommodation cue at a depth between 250 mm and 400 mm. The proposed system retains the characteristics of high resolution and free focusing while adding the accommodation cue. The developed prototype has great competitiveness in near-eye displays.

P‐65: A Novel Free‐Form, High Contrast Emissive Projection Display and Vehicle Applications

A novel high contrast emissive projection display (EPD) on black screen is developed, using a set of RGB emissive nanomaterials that can be selectively excited by digital projection of 3 violet‐blue wavebands. The new photoluminescent display enables a scalable and freeform emissive display onto any vehicle interior surface, without covering or hiding the original surface. For example, the set of RGB emissive materials can be applied as clear topcoat onto pitch‐black foil or substrate on vehicle dashboard or center console, showing superior image contrast in bright ambient light under lower power projection. Such high contrast free‐form emissive projection will be discussed with demos for many new vehicle interior display applications.

P‐17.1: Micro‐LED with patterned substrate for efficient projection display

P‐17.1: Micro‐LED with patterned substrate for efficient projection display

P‐9.16: 4K LCD projection display drive system

P‐9.16: 4K LCD projection display drive system

P‐4.16: Extending Eyebox with Big FOV for Holographic Retinal Projection Display

P‐4.16: Extending Eyebox with Big FOV for Holographic Retinal Projection Display

Study on Speckle Noise Reduction in Laser Projection Displays

Laser speckle has a negative effect on laser projectors, so reducing laser speckle is crucial for the development of laser projector displays. We primarily focus on studying the laser speckle contrast of laser projector displays and the mechanism for reducing speckle. Based on the theory of decreasing temporal and spatial coherence of laser light, this report derives the complete formula for calculating speckle contrast in a laser projector display and provides detailed calculation procedures. According to the comprehensive formula, the primary factors influencing speckle contrast encompass wavelength, spectrum, angles of incidence or observation of lasers, the roughness of the screen surface, the number of independent speckle patterns generated by a moving diffuser, and the number of resolution elements within one eye resolution element in the projector lens. Various methods have been used in the projection engine to suppress speckle, and the main factors for reducing speckle have been verified through theoretical calculations and experimental verification. At a testing distance of 700 mm and with an F-number of 41.7 for the detector lens, the RGB laser speckle contrasts were measured to be 9.1%, 7.3%, and 10.4%, respectively, which aligns well with the results obtained from theoretical calculations. Meanwhile, the speckle contrast of the white field was also measured, yielding a result of 5.6%. The speckle contrast becomes imperceptible when the viewing distance exceeds 2000 mm in our projection system.

Patterned phosphor-in-glass films with efficient thermal management for high-power laser projection displays

Patterned phosphor-in-glass films with efficient thermal management for high-power laser projection displays

Novel Color Converters for High Brightness Laser‐Driven Projection Display: Transparent Ceramics–Glass Ceramics Film Composite

AbstractLaser‐driven projection display puts forward urgent demand for color converter materials to simultaneously achieve balanced‐spectrum properties and strong heat dissipation. Herein, this work develops a novel optofunctional composite by coupling Y3Al5O12:Ce3+ transparent ceramics (TC) with CaAlSiN3:Eu2+ phosphor‐in‐glass film (PiGF) for the first time. Remarkably, this new material architecture design enables a balance between the spectrum properties and heat dissipation ability, and can yield high‐quality white light with brightness of over 2500 lm, luminous efficacy (LE) of over 200 lm W−1, correlated color temperature (CCT) of 3700–4100 K, and improved color rendering index (CRI) of 60–70. Furthermore, the PiGF@TC‐converted laser projection system is also successfully designed, showing natural and real color restoration. Additionally, the combined action of thermal quenching and optical excitation intensity quenching is confirmed for the luminescence saturation upon high‐power blue laser driven. The main mechanism of optical quenching is identified to be energy upconversion dominated by second‐order nonlinear processes. The findings described here suggest a step toward developing the admirable laser‐driven color converters for next‐generation lighting sources.

55‐4: Invited Paper: Monolithic MicroLED Display for AR Applications

In this work, the latest development of monolithic microLED display for Augmented Reality (AR) applications is reported, with the focus on R/G/B monochrome display panels and polychrome projectors from Jade Bird Display Limited (JBD). State‐of‐the‐art Red, Green, and Blue microLED display panel performances are presented. Integration of R/G/B monochrome panels through x‐cube led to the world's smallest full‐color display projector with only 0.4cc in volume, ready to be combined with optical combiner towards smart glasses and AR glasses applications. The implementation of MIPI interface and uniformity correction further enhanced flexibility, functionality, and image quality for faster adoption of this new microLED display technology.

34‐3: Research on Vehicle mounted Projection Display with Local Dimming Effect

With the development trend of large on‐board screen and intelligent driving, PHUD, as a new type of car head up display application scenario, has gradually attracted the attention of various automobile manufacturers. It greatly simplifies the system design by highlighting modules, specific angle of view steering design, and one‐time windshield projection. At the same time, it carries BD cell Local Dimming technology to achieve exquisite HDR projection display and greatly reduce module drive power consumption, and the contrast can reach millions. This paper mainly studies a module display combining BD cell local dimming and PHUD technology.

Simultaneous RGB generation in domain engineered QPM devices using type 0 DFG process

We have theoretically demonstrated the simultaneous generation of red (R), green (G), and blue (B) wavelengths by employing the type-0 quasi-phase-matched (QPM) difference frequency generation (DFG) process in congruent LiNbO3 crystal. Various domain-engineered QPM structures are presented and analysed, aiming to achieve an excellent spectral response. The RGB emissions were observed to vary from 632 nm to 656 nm for red, 504 nm to 532 nm for green, and 449 nm to 484 nm for blue, respectively, for different configurations of input pump, operating temperature, and phase matching periods. A maximum shift of about 10 nm to 20 nm was noticed in the spectral position of the DFG peaks when the operating temperature varies from 25 °C to 60 °C. We have also investigated the effect of pump detuning and random domain fluctuations over the phase matching point on the DFG spectrum. Further, we have addressed the advantages of introducing a phase shifter (PS) domain in the periodically poled lithium niobate (PPLN) to produce excellent equal intensity RGB peaks in a single device for their potential application in a laser-based projection display system.

Driving Towards the Future: Exploring Human-Centered Design and Experiment of Glazing Projection Display Systems for Autonomous Vehicles

The automotive glazing projection display pertains to projecting information onto unique glazing materials in a car through projection equipment, a new direction of Human-Computer Interaction (HCI) in the intelligent cockpit. The core issue in glazing projection is determining what information should be projected onto the car’s glazing and the area to which it should be projected. To address this issue, we conducted a focus group comprising 12 people. We distributed 1082 questionnaires to investigate future autonomous driving contexts, user information demands based on glazing projection, and regional preferences for displaying such information. We selected five contexts and nine high-rated features to design a driver-specific display interface. We conducted eye-movement experiments to investigate the effect of the projection interface on the driver’s gaze behaviors under different display areas and subsequently modified the display areas. This study confirms the feasibility of the glazing projection display and provides theoretical support for HCI development in the intelligent cockpit.

Engineering CsPbX3 (X = Cl, Br, I) Quantum Dot-Embedded Borosilicate Glass through Self-Crystallization Facilitated by NaF as a Phosphor for Full-Color Illumination and Laser-Driven Projection Displays.

All inorganic perovskite (CsPbX3, X = Cl, Br, I) quantum dot (QD) glass samples are considered the next generation of lighting materials for their excellent luminescence properties and stability, but crystallization conditions are difficult to control, which often leads to the inhomogeneous crystallinity of QDs. Here, we provided evidence that the presence of sodium fluoride induced self-crystallization of CsPbBr3 QDs during routine glass formation without the need for additional heat treatment. We showed that NaF simultaneously affected the network structure of glass and promoted the formation of CsPbBr3 QDs, that is, Na+ ions entered the glass network skeleton, partially interrupting the network structure, while the strong electronegativity of F- ions attracted Cs+ and Pb2+ ions into the gaps formed in the glass networks that had been loosened up by Na+ ions, which reduced the activation energy of crystallization processes. Our results showed that NaF-induced CsPbBr3 QDs glass had excellent thermal stability, high photoluminescence quantum efficiency (49%), and luminescent stability under high-power laser irradiation. Finally, this work also demonstrated the general applicability of this method in the making of a series of CsPbX3 (X = Cl, Br, I) QD glass samples by NaF-induced self-crystallization, which drastically expanded the color gamut to a range of full spectrum for luminescence and laser-driven projection displays. We believe that the work presented here represents a new direction for the research and development of full-color gamut inorganic perovskite quantum dot glass samples, which could have a significant impact on the future applications of laser-driven projection displays as well.

Cross talk-free retinal projection display based on a holographic complementary viewpoint array.

In near-eye displays (NEDs), retinal projection display (RPD) is one kind of promising technology to alleviate the vergence-accommodation conflict (VAC) issue due to its always-in-focus feature. Viewpoint replication is widely used to enlarge the limited eyebox. However, the mismatch between viewpoint interval and eye pupil diameter will cause the inter-viewpoint cross talk when multiple viewpoints enter the pupil simultaneously. In this Letter, a holographic complementary viewpoint method is proposed to solve this cross talk problem. Instead of avoiding observing multiple viewpoint images simultaneously, it is designed that multiple complementary viewpoints jointly project the complete image on the retina without cross talk. To do this, the target image is segmented into multiple sub-images, each multiplied with a corresponding partial spherical phase to converge to a specific complementary viewpoint. A group of complementary viewpoint enter the eye pupil simultaneously, and each viewpoint project a corresponding sub-image on a specific area of the retina and splice to a complete image. All of the complementary viewpoints are duplicated to an interlaced two-dimensional array to extend the eyebox in both horizontal and vertical directions. Optical experiment verifies that the proposed method could present smooth transition between viewpoints to avoid both inter-viewpoint cross talk and blank image issues.

Switchable acoustic projection displays based on coding composite structures

Projection display is of relevance for various applications, for example, information communication, encryption and storage. Although numerous optical projection devices have been reported in past years, the realization of switchable acoustic projection display without built-in circuits is a challenge. In this work, we propose a coding composite structure composed of a perforated plate and a coiling-up cavity with six interdigital rigid walls to achieve switchable acoustic projection displays. The configuration can be served as bits ‘0’ and ‘1’ by using forward and backward placements, respectively. The required projection can be displayed as long as the expected image regions are filled with bit ‘1’ and other regions are filled with bit ‘0’. By switching control wave Pc, the projected image is able to be switched from ‘Off state’ to ‘On state’ accordingly. The underlying physical mechanism is the different scattering responses between two coding bits induced by coherent superposition. Our design provides an effective solution for the construction of acoustic projection displays with switchable feature, which may have potential applications in information encryption and storage.

YAG:Ce PiGF@Alumina‐Substrate in a Reflection Mode for High‐Brightness Laser‐Driven Projection Display

AbstractLaser‐driven projector puts forward urgent demand for light‐conversion materials to achieve high‐quality image display. Herein, a composite structure phosphor‐in‐glass film (PiGF) is fabricated via screen‐printing YAG:Ce and low‐melting glass on the alumina substrate. Benefited from well‐retained optical properties of YAG:Ce in amorphous glass and high thermal conductivity of substrate, PiGF can produce desirable luminous flux of 7169 lm and luminous efficiency of 192 lm W−1 at saturation threshold of 13.25 W mm−2. Furthermore, it is demonstrated that thermal management by using a cool fan with aluminum heat sink is essential to reduce heat aggregation and improve white‐light stability of PiGF‐based laser lighting source operated in a reflective mode. Accordingly, a PiGF‐converted laser projection system is successfully designed for the first time, showing more vivid and brighter display feature benefited from high laser‐driven luminance of LCD screen (2180 cd m−2). This work highlights the practical application of PiGF@alumina‐substrate composite as an efficient laser‐driven color converter in high‐brightness projection display.

Method for Three-Dimensional Shape Measurements of Composite Surface Based on Fringe Projection and Dual-Transparent Display Screens

Method for Three-Dimensional Shape Measurements of Composite Surface Based on Fringe Projection and Dual-Transparent Display Screens

Lensless phase-only holographic retinal projection display based on the error diffusion algorithm.

Holographic retinal projection display (RPD) can project images directly onto the retina without any lens by encoding a convergent spherical wave phase with the target images. Conventional amplitude-type holographic RPD suffers from strong zero-order light and conjugate. In this paper, a lensless phase-only holographic RPD based on error diffusion algorithm is demonstrated. It is found that direct error diffusion of the complex Fresnel hologram leads to low image quality. Thus, a post-addition phase method is proposed based on angular spectrum diffraction. The spherical wave phase is multiplied after error diffusion process, and acts as an imaging lens. In this way, the error diffusion functions better due to reduced phase difference between adjacent pixels, and a virtual image with improved quality is produced. The viewpoint is easily deflected just by changing the post-added spherical phase. A full-color holographic RPD with adjustable eyebox is demonstrated experimentally with time-multiplexing technique.

Dark-Channel Enhanced-Compensation Net: An end-to-end inner-reflection compensation method for immersive projection system.

Immersive projection display system is widely adopted in virtual reality and various exhibition halls. How to maintain high display quality in an immersive projection environment with uneven illumination and the color deviation caused by the inter-reflection of light is still a challenging task. In this paper, we innovatively propose a deep learning-based radiation compensation for an L-shaped projector-camera system. This method employs complex reflection phenomena to simulate the light transport processing in an L-shaped environment, we also designed a Dark-Channel Enhanced-Compensation Net (DECNet) which composed of a convolutional neural network called Compensation Net, a DarkChannelNet and another subnet (such as sensing network) aiming at achieving high-quality reproduction of projected display images. The final output of DECNet is the compensation image to be projected. It is always a critical problem to establish appropriate evaluation and analysis indexes throughout the research of light pollution compensation algorithms. In this paper, PSNR, SSIM, and RMSE are proposed to quantitatively analyze the image quality. The experimental results show that this method has certain advantages in reducing the inter-reflection of the projection plane. And our method could also well replace the traditional process using the backlight transmission matrix. It can be concluded to a certain that this method can be extended to other more complex projection environments with strong scalability and inclusiveness.

A Hierarchical Structure Perovskite Quantum Dots Film for Laser‐Driven Projection Display

AbstractLaser‐driven projection display puts forward urgent demand for color converter materials to achieve wide‐color‐gamut and high‐quality image presentation. In this study, a hierarchical structure quantum dots‐in‐glass film (QiGF) is fabricated via co‐sintering stable green/red‐emitting CsPbX3@glass (X3 = Br3, Br1.5I1.5) and commercial low‐melting glass on the sapphire substrate. Benefiting from the well‐retained optical properties of CsPbX3 quantum dots in amorphous glass and high thermal conductivity, QiGF succeeded in inhibiting luminescence saturation after 20 W mm−2 blue laser irradiation. A brand‐new white‐lighting source designed by coupling a blue laser with a pattern “QiGF wheel” produced ultra‐narrow blue/green/red tri‐color emissions and total luminous flux of 146 lm. Accordingly, a QiGF‐converted laser projection system is successfully designed for the first time, showing more natural and real color restoration for its wide color gamut display feature (157% of conventional light‐emitting diode projection and 107% of NTSC standard). The present study highlights the practical application of CsPbX3 quantum dots composite as an efficient laser‐driven color converter in projection display.