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This figure shows the total number of receive elements encountering critical angles in 3D phase array imaging in C-scan slices through the pyramidal volume for three focal zones: z = 20 mm, z = 48 mm, and z = 150 mm. Axes denote steering angles in θ and φ. Elements at depth and steering angle combinations such that they encounter rays that exceed critical angles are turned off for that particular image line and focal zone.
