Abstract
Purpose :
Two-photon (2P) vision enables the perception of pulsed near-infrared (NIR) light as visible light with approximately half the wavelength. Here we explore the viability of an infrared display wherein three NIR channels, corresponding to red, green, and blue visual perceptions, are combined to generate mixed colors. Specifically, we focus on characterizing the white color perception.
Methods :
The display was developed from a prior setup (Manzanera et al., Biomedical Optics Express, 2020). Using a pulsed supercontinuum laser with ~1 ns pulses and a repetition rate of 15 kHz, the beam was divided into three spectral bands, each featuring quasi-monochromatic wavelengths (central wavelengths: 850, 950, and 1050 nm; FWHM: 10-50 nm). The 950 and 1050 nm wavelengths elicit blue and green colors, respectively, via the 2P mechanism; whereas the 850 nm one contributes the red component in this case through normal one-photon (1P) vision. The beams were subsequently recombined and directed to project a 5x5 arcmin square onto the fovea of three healthy subjects. Simultaneously, a similar visible stimulus from an OLED display was projected next to the NIR stimulus. Subjects were asked to adjust the color (hue, saturation, and value) of the visible stimulus to match the color of the NIR one. A spectrometer was then used to obtain the chromatic information of the matched visible stimulus. Ocular exposure remained below the limits of the ANSI Z136.1-2014 standard.
Results :
To achieve the white color, power levels at the pupil plane of 1.4, 33.2, and 52.5 μW were adjusted for the 850, 950, and 1050 nm wavelengths, respectively. The combination of the three NIR channels allowed subjects to perceive a white color with average CIE 1931 coordinates (x,y) = (0.29, 0.40) and small standard deviations, Δx,y < 0.04. Separate channel chromatic coordinates were also measured, obtaining (Δx,y ≤ 0.04): (0.49, 0.33) for the red channel, (0.27, 0.50) for the green one, and (0.18, 0.26) for the blue one.
Conclusions :
A near-infrared RGB display can induce white perception and, therefore, reproduce other colors within the color space defined by its channels. This, coupled with the higher penetration of NIR light into the ocular media could help to develop chromatic tests suitable for near-opaque eyes and to better test the impact of chromatic aberrations in vision.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.