Minchen Wei

Minchen Wei
The Hong Kong Polytechnic University | PolyU · Department of Building Environment and Energy Engineering

PhD (Penn State University), MSc (Penn State University), BEng (Fudan University)
Carrying out research related to color science, imaging science, and illuminating engineering.

About

112
Publications
23,218
Reads
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1,429
Citations
Introduction
Minchen Tommy Wei is Director of Color, Imaging, and Metaverse Research Center at PolyU. He is the recipient of China's Excellent Young Scientists Fund. He is also a topical editor (associate editor) of Journal of the Optical Society of America A (JOSA A), and Color Research & Application. His research interest focuses on fundamental color science and color management, and applying color science on various imaging (e.g., camera, display, sensor, VR, AR, and MR) and lighting (e.g., LED) systems.
Additional affiliations
July 2020 - August 2021
The Hong Kong Polytechnic University
Position
  • Professor (Associate)
October 2015 - June 2020
The Hong Kong Polytechnic University
Position
  • Professor (Assistant)
August 2009 - October 2015
Pennsylvania State University
Position
  • Research Assistant, Instructor
Education
August 2009 - August 2015
Pennsylvania State University
Field of study
  • Dept. of Architectural Engineering, Illuminating Engineering
September 2005 - June 2009
Fudan University
Field of study
  • Dept. of Illuminating Enginering & Light Sources

Publications

Publications (112)
Article
Full-text available
In lighting practice, light level is seldom considered when specifying light source color rendition. Many past studies found that sources that can enhance color saturation within a certain range, especially for red colors, were preferred, but the experiments were typically carried out with an illuminance between 200 and 500 lx and the illuminance w...
Article
Past studies reported that the degree of chromatic adaptation was affected by viewing medium and adapting luminance. In this study, human observers adjusted the color appearance of a stimulus produced by a self-luminous display to make it appear as white as possible under different adapting conditions, whose adapting luminance and Correlated Color...
Article
Augmented reality superimposes virtual objects onto a real environment, allowing humans to simultaneously see virtual objects and real environment. Such a viewing condition and the luminance relationship between virtual objects and real environments introduce new challenges in color appearance characterization. In this study, an augmented reality s...
Article
Chromatic adaptation is an important mechanism in the human visual system, which affects the perceived color appearance of scenes and objects under the illumination. Recent studies, however, found that the degree of chromatic adaptation was significantly affected by the chromaticities of the adapting condition, which is not characterized in the exi...
Article
In part I of this study [ Opt. Express 29 , 12292 ( 2021 ) 10.1364/OE.418675 ], 50 human observers matched the color appearance of six color stimuli produced by four smartphone displays, including one conventional liquid crystal display (LCD) and three organic light emitting diode (OLED) displays, to those produced by a reference smartphone OLED di...
Article
For a variable speed (VS) space heating air source heat pump (ASHP) unit, to comprehensive study its frosting suppression and heating performances, a condensing-frosting performance map has been proposed. An experimental study using an experimental VS ASHP unit to obtain condensing-frosting performance maps was previously reported. However, obtaini...
Article
Both observer age and size of stimulus as characterized using the field of view (FOV) are two important parameters to affect the color matching functions (CMFs) of human observers. They are also included in the cone fundamental and CMFs models that were recently proposed by the International Commission on Illumination (CIE) in 2006. In contrast to...
Article
For a space heating ASHP unit, frosting on its outdoor coil would adversely impact its normal operation, requiring frequent defrosting and resulting in low operating efficiency and poor indoor thermal comfort. It has been shown that varying the speeds of both compressor and outdoor air fan in a variable speed (VS) ASHP unit can lead to different ou...
Article
In part I of this work [ Opt. Express , 27 , 9276 , (2019) 10.1364/OE.27.009276 ], we carried out an experiment to investigate the effects of adapting luminance and correlated color temperature (CCT) on degree of chromatic adaptation. Under the highest white luminance L w of 900 cd/m ² , an incomplete chromatic adaptation was still found under the...
Article
Many related studies suggested that a fixed airflow direction usually led to that the most frost would only deposit on the windward side of finned tube heat exchangers (FTHXs) of the traditional single fan outdoor coils in air source heat pumps (ASHPs), result in more frequent defrosting operations and a lower operating efficiency of ASHPs. In this...
Conference Paper
Full-text available
In the study, two psychophysical experiments are carried out to understand the visual comfort and white appearance of a tablet display. Twenty-four observers assess the visual comfort of document layouts, and eleven observers rate the whiteness percentage of the stimulus under normal light levels with a CCT of 6500 K. The result of the experiment f...
Article
In the study, two psychophysical experiments are carried out to understand the visual comfort and white appearance of a tablet display. Twenty-four observers assess the visual comfort of document layouts, and eleven observers rate the whiteness percentage of the stimulus under normal light levels with a CCT of 6500 K. The result of the experiment f...
Article
With the development of wide color gamut displays, several recent studies investigated the performance of the CIE standard color matching functions (CMFs) in characterizing the color matches and observer metamerism between different primary sets. These studies, however, always employed different spectral shapes to produce color stimuli, which faile...
Article
The appearance of color stimuli with luminance levels beyond the diffuse white is gaining importance due to the popularity of high dynamic range (HDR) displays. Past work on color appearance of stimuli, color appearance models, and uniform color spaces mainly focused on the stimuli with luminance levels below the diffuse white, which were produced...
Article
Full-text available
E-reading devices are becoming more and more common in our daily life, and they are used under a wide range of ambient light levels, from completely dark to extremely bright conditions. In this study, a psychophysical experiment is carried out to investigate how ambient light level affects the visual comfort of an e-reading device. Human observers...
Article
This article explores the best practices for conducting psychophysical experiments that investigate how colour rendition influences the perception of architectural environments. We offer guidance that covers all stages of research from preliminary development to publication, focusing especially on experiments that investigate qualities such as perc...
Article
Organic light emitting diode (OLED) displays use red, green, and blue primaries with a higher saturation level to produce larger color gamuts than conventional liquid crystal displays (LCD). No past study, however, experimentally investigated how such a difference between these two display types causes color mismatch and observer metamerism using t...
Conference Paper
In the study, a prediction model of visual comfort is proposed based on an artificial neural network. Using the ambient illuminance levels and screen parameters as features, the model can well represent the visual perception with high correlation coefficients.
Conference Paper
Full-text available
Head-up displays (HUDs) can be used under various surround conditions ranging from extremely dark to very bright environments such as daylight. Many head-up displays are designed to enhance visual clarity by adjusting the brightness of the display. However, few studies aim to investigate the impacts of the text-background lightness combination of a...
Article
Head-up displays (HUDs) can be used under various surround conditions ranging from extremely dark to very bright environments such as daylight. Many head-up displays are designed to enhance visual clarity by adjusting the brightness of the display. However, few studies aim to investigate the impacts of the text-background lightness combination of a...
Article
Various color difference metrics were developed for characterizing the perceived color difference between individual color patches. Color difference between palettes containing multiple color patches, however, is critically important in product design and computer graphics. This study aimed to investigate how the perceived color difference between...
Article
Displays with different primary sets were found to introduce perceived color mismatch between pairs that are computationally metameric and to affect the degree of observer metamerism. OLED display is becoming more and more popular than LCD display in different imaging systems. In this study, human observers used an LCD and eight OLED displays to ma...
Conference Paper
Various color difference metrics were developed for characterizing the perceived color difference between individual color patches. Color difference between palettes containing multiple color patches, however, is critically important in product design and computer graphics. This study aimed to investigate how the perceived color difference between...
Article
Curtain walls are more and more commonly used as building facades. They allow a better daylight availability and a direct connection to exterior environments. Meanwhile, due to the high specular reflections, they may also introduce negative impacts, such as glare and urban heat island effects, to the surround, especially in dense and urban environm...
Article
Characterizing daylight quality for flats in residential buildings is critically important in Hong Kong, where buildings are close to each other. In this study, we performed Climate Based Daylight Modeling (CBDM) calculations on 400 flats in a public housing property using three different methods. In addition to the Typical Meteorological Year (TMY...
Article
Color appearance models were developed to characterize the color attributes of stimuli under different viewing conditions based on data collected through magnitude estimation or color matching experiments. Although human beings experience very high light levels under daylight and the reproduction of colors under daylight is important in the color a...
Article
Full-text available
Displays with different primary sets were found to introduce perceived color mismatch between stimuli that are computationally metameric and to affect the variations of the perceived color difference of metameric stimuli among observers (i.e., observer metamerism). In this study, computational analyses and psychophysical experiments were carried ou...
Article
Full-text available
CAT02, the most widely used chromatic adaptation transform to characterize the chromatic adaptation mechanism in the human visual system, includes a factor D to characterize the degree of chromatic adaptation. This factor, however, is only determined by the luminance level of the adapting field and surround. This study was designed to investigate h...
Article
In recent work [J. Opt. Soc. Am. A 36, 1022 (2019)], we found that Δ𝐸∗ab/s in CIELAB is not suitable for describing the perceived speed of temporal color changes in full-room illumination. Two hue transitions with the same physical speed of change, in terms of Δ𝐸∗ab/s, were not perceived to change at the same speed. This is not really surprising, s...
Article
Unique hue plays a critical role in color appearance models and uniform color spaces. Past studies investigating unique hues commonly used 40 Munsell samples with the same chroma and lightness levels to produce color stimuli, with a hue angle step of 9°. These 40 samples were always simultaneously presented to the observers. Both the larger hue ang...
Article
Metamer mismatching occurs in both the human visual system and digital imaging systems. Increasing the number of sensors in digital imaging systems is an efficient method to reduce the degree of metamer mismatching. This study investigates the number of sensors that are needed for the digital imaging systems to have a similar ability to the human s...
Article
Many past studies investigating visual performance focused mainly on the effect of luminance contrast between the target and background. Other studies have suggested the importance of colour contrast on visual performance. This pilot study was designed to investigate whether visual performance in the context of road lighting can be improved by enha...
Article
Adapting chromaticities are not considered in characterizing the degree of chromatic adaptation in various chromatic adaptation transforms (CATs). Though several recent studies have clearly suggested that the effect of adapting chromaticities on degree of chromatic adaptation should not be ignored, these studies were only carried out under a single...
Article
Color appearance models have been extensively studied for characterizing and predicting the perceived color appearance of physical color stimuli under different viewing conditions. These stimuli are either surface colors reflecting illumination or self-luminous emitting radiations. With the rapid development of augmented reality (AR) and mixed real...
Article
Great efforts have been made to develop color appearance models to predict color appearance of stimuli under various viewing conditions. CIECAM02, the most widely used color appearance model, and many other color appearance models were all developed based on corresponding color datasets, including LUTCHI data. Though the effect of adapting light le...
Article
Full-text available
Polymeric g‐C3N4 with controllable photoluminescence emission wavelength in the whole visible light range (450–650 nm) is synthesized through the one‐step molecular doping during the thermal condensation process of g‐C3N4 conjugated framework, which opens up its application beyond the conventional catalysis scopes. By adjusting the doped content of...
Conference Paper
Sunlight is a valuable resource with photometric and radiometric characteristics and the common characteristics of these two aspects is the spectral power distribution (SPD). The particulate matter (PM) has a great influence on SPD and this paper aims to study the relation between PM concentrations and SPD. The SPD and PM concentrations were measur...
Article
An experiment was conducted to examine colour rendition specification criteria. Twenty-five participants each evaluated 90 lighting scenes in a room filled with objects. The lighting scenes included nine chromaticity groups, each with 10 systematically-varied colour rendition conditions designed to meet or not meet previously proposed colour prefer...
Article
Different chromaticities for producing white appearance were found when viewing color stimuli produced by physical color samples and displays, which has been widely attributed to the different degrees of chromatic adaptation caused by the different viewing media. Here we carried out a pilot study to investigate whether such a difference was caused...
Article
Numerous efforts have been made to investigate how light source color rendition affects color preference. Though the effect of light level on color appearance (known as the Hunt effect) was found in 1952, most studies investigating color preference under light sources only employed a single illuminance level and the illuminance levels were typicall...
Article
Substantial efforts have been made to develop new colour fidelity measures that are better correlated to perceived colour fidelity. Such measures minimize the possibility of increasing rated colour fidelity through spectral optimization without improving perceived colour fidelity. This paper reports a psychophysical experiment that was carefully de...
Article
Past studies investigating the unique hues only used samples with a relatively high saturation levels under standard illuminants. In this study, 10 observers selected the four samples with unique hues from 40 V6C8 (Value 6 Chroma 8) and 40 V8C4 (Value 8 Chroma 4) Munsell samples under six light sources, comprising three levels of Duv (i.e., 0, −0.0...
Article
Though Typical Meteorological Year (TMY) data is widely used for predicting daylight quality and daylight-responsive control system performance, few studies investigated whether the predictions were accurate. In this study, daylight simulation was performed for a real space using the TMY data and an actual local weather data with a one-minute inter...
Article
Recent studies revealed the failure of typical blue-pumped white light emitting diodes (LEDs) in rendering the white appearance of surface colors, which was caused by the lack of ultraviolet (UV)/violet radiation to excite the fluorescent whitening agents (FWAs). The effect of such a failure on image color appearance has not been previously investi...
Article
Full-text available
Policymakers and standardization bodies have started to make recommendations about the use of lighting products at night, with the goal of reducing negative impacts on human health. We report a series of field measurements to quantify the responses of different human photoreceptors and the possible suppression of melatonin production caused by the...
Article
Many tablets are designed to change display brightness or color with surround for enhancing visual comfort. Although both color and brightness of a surround may vary a lot, few studies investigated how text‐background lightness combination of a tablet display and surround jointly affect visual comfort, and how display white point affects visual com...
Article
Full-text available
The whiteness specification is critically important in surface color industry, especially when fluorescent whitening agents (FWAs) are added to objects. The CIE whiteness formula, the most widely used whiteness formula, only characterizes the whiteness under CIE standard D65, which ignores the change of whiteness under different light sources due t...
Article
Full-text available
Recently, corneal illuminance attracts much attention because it is closely related to important functions of indoor lighting. Especially, applying circadian light in the built environment places a challenging requirement on indirect corneal illuminance. In this work, rule-of-thumb equations are proposed to guide circadian lighting design: (i) for...
Conference Paper
A recent report issued by the American Medical Association (AMA) recommended use of lighting products with lower correlated color temperature (CCT) to reduce the potential negative impact of external lighting on human health. In this article, we report a series of field measurements that were conducted to quantify the effect of external lighting on...
Article
The weakness of the CIE whiteness formula, the most widely used formula to characterize the whiteness of surface colors, has been well documented. It cannot characterize the whiteness under the illuminants other than CIE standard D65 and has a small whiteness boundary. A psychophysical experiment was carried out to investigate the whiteness boundar...
Article
Various white balance algorithms, based either on the Gray World assumption or on the Retinex theory, have been developed to remove the color cast of illumination in images. Though most man‐made white objects contain different amount of fluorescent whitening agents (FWAs) to enhance and create different degrees of whiteness appearance, the FWA exci...
Article
Full-text available
In comparison to the great efforts made on the enhancement of image quality for tablet displays, little attention has been paid on the concept of white point. Given the increasing popularity of the light sources with chromaticities off the Planckian locus and color-tunable LED lighting, it is important to investigate human's white perception of tab...
Article
Full-text available
Whiteness is an important colorimetric characteristic for surface colors. The CIE whiteness formula, the most widely used formula, only characterizes the whiteness of a surface color under CIE standard D65 and requires a sample to be within a small chromaticity region. In this study, 20 observers evaluated the whiteness appearance of 88 samples und...
Article
Full-text available
An experiment was conducted to evaluate how perceptions of a light source’s colour quality depend upon colour rendition and chromaticity. Thirty-four participants each evaluated 50 lighting scenes in a 3.7 m by 5.5 m room filled with objects. The lighting scenes included five chromaticity groups, with 10 systematically-varied colour rendition condi...
Article
Recent studies have suggested that light sources with chromaticities slightly below the blackbody locus are preferred by human observers. The preferred light settings identified in these studies, however, had high values of colour fidelity and colour gamut. It has been speculated that the preference was caused by good colour rendition, rather than...
Article
The impact of spectral power distribution of daylight simulators (ie, D65 simulators) on surface whiteness specification was investigated by focusing on how CIE whiteness and tint values of 8 whiteness samples with fluorescent whitening agents (FWAs) vary under different D65 simulators. Large variations in both whiteness (∼16 points) and tint (∼1.6...
Article
Light causes not only vision, but also non-visual effects such as regulating the circadian system. Although the effort to fully understand the mechanism of non-visual response is still ongoing, quantitative models have been proposed to evaluate light's circadian stimulus based on the characteristics of light incident on human eyes. With the light-e...
Technical Report
The CIE Colour Rendering Index (CRI), defined in CIE 13.3-1995, in particular the general colour rendering index, Ra, is widely adopted and used by the lighting industry, in regulatory documents and in international and regional standards and specifications. However, limitations of the CRI have been recently addressed, especially for solid-state li...
Article
Whiteness is an important colorimetric characteristic for surface colors. Currently, the CIE whiteness formula is widely used to characterize the whiteness of a surface in industry, whose limitations have been well documented. In this study, the whiteness appearance of 55 textile samples [43 non-fluorescent whitening agents (FWAs) and 12 FWA sample...
Conference Paper
Whiteness is an important quality parameter for surface colour industries. The CIE whiteness metric has been widely used but is known for shortcomings. For example, it cannot cover sufficient ‘white’ region in colour space and it should only be used for illuminant D65. In a psychophysical experiment, fifty samples were assessed using 2 scales. We i...
Article
Although it is a critical component of any measure of color rendition, a standardized set of color samples can seldom perfectly match a real space or a real set of observed objects. This means that there will always be some level of mismatch between predicted and observed color shifts. This article explores how the color distortions of three object...