Stimuli were projected onto a 200 × 113 cm video-projection screen (Celexon HomeCinema, Tharston, Norwich, UK), using a Propixx DLP Projector (Vpixx Technologies, Saint-Bruno, QC, Canada) running at a temporal resolution of 1440 frames per second and a spatial resolution of 960 × 540 pixels2. Experiments took place in a dimly lit, sound-attenuated room. The gray background used in all experiments had an average luminance of 30 cd/m2. Observers sat 270 cm from the projector with their head supported by a chin rest. Eye movements were measured using an Eyelink 2 head-mounted system (SR Research, Osgoode, ON, Canada) with a sampling rate of 500 Hz. Stimulus display was implemented in MATLAB 2015a (MathWorks, Natick, MA, USA), using Psychtoolbox (Brainard, 1997 (link); Kleiner, Brainard, Pelli, Ingling, Murray, & Broussard, 2007 ) and Eyelink Toolbox (Cornelisen, Peters, & Palmer, 2002 ) extensions, running on a Dell Precision T7810 Workstation with a Debian 8 operating system (Round Rock, TX, USA). Responses were collected via a standard US-English keyboard.
Propixx dlp projector
Manufactured by VPixx Technologies
Sourced in United Kingdom, Canada
The Propixx DLP projector is a high-performance display device designed for laboratory and research applications. It utilizes Digital Light Processing (DLP) technology to provide precise and consistent image quality. The Propixx DLP projector is capable of generating visual stimuli for experiments and demonstrations, supporting a wide range of resolutions and refresh rates.
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Lab products found in correlation
5 protocols using propixx dlp projector
1
High-Speed Visual Perception Experiment
2
Visual Stimuli for Object Categorization Experiments
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Visual stimuli were colour pictures representing thirty different objects from six semantic categories (fruits, vegetables, animals, birds, tools, vehicles). The set of stimuli were used in two previous fMRI studies from our group9 (link),12 (link), and were controlled for psycholinguistic features and familiarity (for details, see12 (link)). Stimuli were presented using MATLAB and the Psychophysics Toolbox48 (link), and were projected on a translucent screen placed at about 130 cm from the participant, using a Propixx DLP projector (VPixx technologies), with a refresh rate of 60 Hz and a resolution of 1280 × 1024 pixels (21.7 × 13.16°).
3
Visual Perception Study in Controlled Environment
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All experiments were conducted in a dark, sound-dampened booth. Stimuli were projected on a 200x113 cm screen (Celexon HomeCinema, Tharston, Norwich, UK) using a PROPixx DLP Projector (Vpixx Technologies, Saint-Bruno, QC, Canada) with a spatial resolution of 1920x1080 pixels and a refresh rate of 120 Hz (frame duration of 8.3ms). Observers faced the screen at a viewing distance of 180 cm while their heads were stabilized on a chin rest. The position of the dominant eye was recorded at a sampling rate of 1 kHz using a desk-mounted infrared eyetracker (EyeLink 1000 Plus; SR Research, Osgoode, Canada). Stimulus presentation was controlled by a DELL Precision T7810 Workstation (Debian GNU Linux 8) and implemented in Matlab 2016b (Mathworks, Natick, MA, USA) with the PsychToolbox (Brainard, 1997 (link); Kleiner et al., 2007 (link)) and Eyelink toolbox (Cornelissen et al., 2002 (link)) extensions. Observers generated their responses on a standard QWERTY keyboard positioned centrally in front of them.
4
High-Speed Gaze-Contingent Stimulus Presentation
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Stimuli were projected onto a 16:9 (250.2 × 141.0 cm) video-projection screen (Stewart Silver 5D Deluxe, Stewart Filmscreen, Torrance, CA), mounted on a wall 340 cm in front of the participant, using a PROPixx DLP projector (Vpixx Technologies, Saint-Bruno, QC, Canada) running at a 1440-Hz refresh rate and a resolution of 960 × 540 pixels. The experimental code was implemented in MATLAB 2016b (Mathworks, Natick, MA, USA) on Ubuntu 18.04, using Psychtoolbox (58 , 59 (link)) and was run on a Dell Precision T7810 Workstation supplied with a Nvidia GTX 1070 graphics card. Eye movements of both eyes were recorded via a TRACKPixx3 tabletop system (Vpixx Technologies, Saint-Bruno, QC, Canada) at a sampling rate of 2000 Hz, running firmware version 11 in experiment 1 and version 16 in experiment 2. Participants rested their head on a chin rest. A custom wrapper function toolbox was used to control the eye tracker, which is made publicly available on Github: https://github.com/richardschweitzer/TrackPixxToolbox .
5
Biologically-Relevant Visual Flicker Frequencies
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Participants viewed experimental stimuli back-projected on a translucent screen by a Propixx DLP projector (VPixx technologies, Saint-Bruno, Canada), employing a refresh rate of 120 frames per second and a resolution of 1920 × 1080 pixel (width × height). The stimulation comprised an ellipse (horizontal/vertical diameter = 6.6°/3.3° of visual angle) positioned in the lower visual field at a center-to-center eccentricity of 3° below fixation (Figures 1A,B ). A diamond shape (maximum eccentricity = 0.9°) served as a central fixation point. Stimuli were presented against a gray background (RGB: 85, 85, 85).
The ellipse underwent periodic luminance changes (= flicker) at rates of either 7 or 11 Hz in the course of each trial: Relative luminance to background oscillated between a minimum of 0% (total black, RGB: 0,0,0) and a maximum of 100% (background gray). Ellipse luminance changed in small increments on each presentation frame to approximate sinusoidal modulations.
We chose our two frequencies within a range that is typically used in frequency-tagging experiments (see Norcia et al., 2015 (link)). Both frequencies were hence known to produce SSRs of high signal-to-noise ratios. Further vital to the design of our study was that 7 and 11 Hz SSRs did not produce harmonics that coincided spectrally within the range of frequencies that we analyzed (<50 Hz).
The ellipse underwent periodic luminance changes (= flicker) at rates of either 7 or 11 Hz in the course of each trial: Relative luminance to background oscillated between a minimum of 0% (total black, RGB: 0,0,0) and a maximum of 100% (background gray). Ellipse luminance changed in small increments on each presentation frame to approximate sinusoidal modulations.
We chose our two frequencies within a range that is typically used in frequency-tagging experiments (see Norcia et al., 2015 (link)). Both frequencies were hence known to produce SSRs of high signal-to-noise ratios. Further vital to the design of our study was that 7 and 11 Hz SSRs did not produce harmonics that coincided spectrally within the range of frequencies that we analyzed (<50 Hz).
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