Fig. 1. Schematic for multi-focus non-periodic trajectory scanning for a femtosecond laser based on DMD and galvo scanners. (a) The blue area is the target scanning area. The galvo scanners cause foci to achieve raster scanning, and the DMD controls the “on or off” of each of the four foci by quickly transforming the hologram. (b) Scanning control in the other direction of raster scanning. When foci enter the target area, the foci are turned “on.” (c) Final scanning trajectory.

Fig. 2. Schematic for aberration control and intensity homogenization process of the foci array. Scanning phase φ_scan,k determines the position of the foci; correction phase φ_AO,k determines the aberration (i.e., “on or off”) of the foci; the weight w_k can change the intensity of the foci; θ_k starts with a random phase. g_k is the weight scaling factor calculated by the actual focus intensity captured by the camera. Iteratively correct g_k, w_k, and θ_k to improve the intensity uniformity of the foci.

Fig. 3. Results of intensity uniformity for foci arrays with different numbers. (a) shows the foci arrays with a number of foci from 1 to 36, with each row being a focus array. The focus within the green triangle area is the “off” focus, in which the gray value is multiplied by 8. (b) Normalized intensity of all foci. The blue data points represent the “on” foci, and the red data points represent the “off” foci. The intensity uniformity of the “on” foci reaches 98%, and the intensity of the “off” foci is less than 20% of the intensity of the “on” foci.

Fig. 4. Optical configuration of the scanning system. FS laser, fiber femtosecond laser; M1, reflectivity mirror; L1-L6, lens; DMD, digital micromirror device; KDCM, Keplerian dispersion compensation module; SF, spatial filter; Galvo, galvanometer scanners; DM, dichroic mirror; OBJ, objective lens; BS, beam splitter; CL, condensing lens; TL, tube lens.

Fig. 5. (a) The scanning mode of mosaic splicing is used to scan a circular surface. The light blue area is the target scanning surface. (b) The mosaic 1, which is completely inside the circle, is a square scanning surface that can be fully scanned with multi-focus parallel raster scanning. (c) The target scanning area of the mosaic 2, which is partly outside the circle, is non-periodic, and thus needs to use the scanning method in Fig. 1. (d) The result of making the corneal flap porcine cornea in vitro by the proposed multi-focus scanning method. (e) The result of making the corneal flap by the conventional multi-focus scanning method. (f), (g) The enlarged view of the corresponding part in (d), (e). (h) The result of lifting the corneal flap for (d).