Abstract

Confocal and nonlinear optical microscopies have been applied for dermatological studies because of their capability to provide sub-surface three-dimensional images with sub-µm spatial resolutions. Optical signal degradation as the imaging plane being moved toward deeper regions in skin specimens is the key factor that limits the observation depth for the laser scanning based linear or nonlinear imaging modalities. In this article, we studied the signal degradation in fixed human skin specimens using reflection confocal microscopy and higher-harmonic optical microscopy based on a Cr:forsterite femtosecond laser centered at 1230-nm. By analyzing the optical properties through these linear and nonlinear imaging modalities, we found that the optical signal degradation in the studied human skin specimen is dominated by the distortion of the point spread function.

© 2006 Optical Society of America

Full Article  |  PDF Article

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (7)

Fig. 1.
Fig. 1.

Set up of the harmonic laser scanning microscope combining the reflection confocal with the higher-harmonic generation modalities. BF: barrier filter; BS: beamspliter; DB: dichroic beamsplitter; PMT: photomultiplier tube; GM: galvanometric mirrors; PD: photodetector; VIC: V-I converter circuit; PH: confocal pinhole.

Fig. 2.
Fig. 2.

Cross-sectional (a) RC, (b) THG, (c) SHG, and (d) combined images of human skin taken at a depth of 90-|j,m from the skin surface around the dermo-epidermal junction. Images size: 120×120μm.

Fig. 3.
Fig. 3.

Cross-sectional (a) RC, (b) THG, (c) SHG, and (d) combined images of human skin taken at a depth of 150-μm from the skin surface in the dermal layer. Images size: 120×120μm.

Fig. 4.
Fig. 4.

Lateral resolutions of RC (black square), SHG (red circle), and THG (green triangle) images versus depth in the studied human skin sample.

Fig. 5.
Fig. 5.

Focal diameter degradation with depth in the studied human skin sample derived from the lateral resolution of the RC (black square), SHG (red circle), and THG (green triangle) images respectively.

Fig. 6.
Fig. 6.

RC signal power (square) versus focal diameter degradation with different depths in the studied human skin sample. The black solid line is the best fit with a slope = -2.24 and the gray solid line is the slope = -2 fitting. Note that both axes are log-scaled.

Fig. 7.
Fig. 7.

THG signal power (square) versus focal diameter degradation with different depths in the studied human skin sample. The solid black line is the best fit with a slope = -4.5. The solid gray line is with a slope = -4. Note that both axes are log-scaled.

Tables (1)

Tables Icon

Table 1. Formula for the focal beam diameter and the resolutions of different imaging modalities.

Metrics