Temporal Properties of Liquid Crystal Displays: Implications for Vision Science Experiments

Tobias Elze,Thomas G Tanner,Bart Krekelberg

doi:10.1371/journal.pone.0044048

Abstract

Liquid crystal displays (LCD) are currently replacing the previously dominant cathode ray tubes (CRT) in most vision science applications. While the properties of the CRT technology are widely known among vision scientists, the photometric and temporal properties of LCDs are unfamiliar to many practitioners. We provide the essential theory, present measurements to assess the temporal properties of different LCD panel types, and identify the main determinants of the photometric output. Our measurements demonstrate that the specifications of the manufacturers are insufficient for proper display selection and control for most purposes. Furthermore, we show how several novel display technologies developed to improve fast transitions or the appearance of moving objects may be accompanied by side–effects in some areas of vision research. Finally, we unveil a number of surprising technical deficiencies. The use of LCDs may cause problems in several areas in vision science. Aside from the well–known issue of motion blur, the main problems are the lack of reliable and precise onsets and offsets of displayed stimuli, several undesirable and uncontrolled components of the photometric output, and input lags which make LCDs problematic for real–time applications. As a result, LCDs require extensive individual measurements prior to applications in vision science.

Highlights

Motivation and Scope In many fields of experimental and clinical vision science where display devices are used, the accurate characterisation of the display output including its temporal properties is crucial for reliable measurements or diagnoses
We found that dynamic capacitance compensation (DCC) technology is common in modern Liquid crystal displays (LCD) panels, and Fig. 7 shows average response times of less than 10 ms for all four panel types considered in our measurements
Conclusions the LCDs have largely replaced the previously dominant cathode ray tubes (CRT) displays, the temporal properties of LCD monitors had not been throughly investigated with respect to the requirements of vision science yet, except for motion blur [16]

Summary

Introduction

Motivation and Scope In many fields of experimental and clinical vision science where display devices are used, the accurate characterisation of the display output including its temporal properties is crucial for reliable measurements or diagnoses. A number of experimental paradigms, such as rapid serial visual presentation, visual masking, or priming, require short presentations of visual stimuli with precise onsets, offsets, and precise interstimulus intervals. In certain eye tracking applications, the display needs to be updated rapidly depending on the observers’ current gaze position (gaze–contingency paradigm), which requires an immediate processing of the input signal. The photometric properties of the display output play an essential role if neuronal responses to visual stimuli are recorded and analyzed, and erroneous assumptions about the stimulus signal may lead to data analysis errors and possibly to incorrect experimental conclusions about the visual system. For some computational models violations of assumptions about the input signal shape may completely invalidate the modelling

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Discussion

Conclusion