Fig. 2

Illustrations of the stereoacuity test system. a Example of the fixed distance test system. The shape of the symbol is c; the size of the symbol is 95 × 95 pixels; the type of disparity is crossed, and the grade of the test is first (four lines represented the disparity of 100 pixels, 75 pixels, 50 pixels and 25 pixels from top to bottom). The stereo targets are line 1–3, line 2–6, line 3–4, and line4-2. b Example of the fixed distance test system. The shape of the symbol is E; the size of the symbol is 60 × 60 pixels; the type of disparity is uncrossed, and the grade of the test is second, page 2 (five lines represented the disparity of 75 pixels, 70 pixels, 65 pixels, 60 pixels and 55 pixels from top to bottom). The stereo targets are line 1–5, line 2–5, line 3–2, line4-3, and line 5–4. c Example of the fixed distance test system. The shape of the symbol is □; the size of the symbol is 30 × 30 pixels; the type of disparity is crossed, and the grade of the test is third, page 3 (five lines represented the disparity of 15 pixels, 14 pixels, 13 pixels, 12 pixels and 11 pixels from top to bottom). The stereo targets are line 1–4, line 2–4, line 3–3, line4-2, and line 5–6. d Example of the variable distance test system. The shape of the symbol is C; the size of the symbol is 45 × 45 pixels; the type of disparity is crossed. The reference target in the top line is no.4 with 3 pixels disparity, while in the bottom line is no.3 with 2 pixels disparity. The test stereo target in the middle line is no.5 with 1 pixels disparity