In some embodiments, portions of the LED filament presented in the first quadrant and the second quadrant (the upper quadrants) in the side view may be symmetric (e.g., in line symmetry with the Y-axis) in structure; portions of the LED filament presented in the third quadrant and the fourth quadrant (the lower quadrants) in the side view may be symmetric (e.g., in line symmetry with the Y-axis) in structure. In addition, an emitting direction of a portion of the LED filament in the first quadrant in the side view is symmetric with that of a portion of the LED filament in the second quadrant in the side view, and an emitting direction of a portion of the LED filament in the third quadrant in the side view is symmetric with that of a portion of the LED filament in the fourth quadrant in the side view.
In another embodiment, an arrangement of LED chips in a portion of the LED filament in the first quadrant in the side view is symmetric with an arrangement of LED chips in a portion of the LED filament in the second quadrant in the side view, and an arrangement of LED chips in a portion of the LED filament in the third quadrant in the side view is symmetric with an arrangement of LED chips in a portion of the LED filament in the fourth quadrant in the side view.
In another embodiment, a power configuration of LED chips with different power in a portion of the LED filament in the first quadrant in the side view is symmetric with a power configuration of LED chips with different power in a portion of the LED filament in the second quadrant in the side view, and a power configuration of LED chips with different power in a portion of the LED filament in the third quadrant in the side view is symmetric with a power configuration of LED chips with different power in a portion of the LED filament in the fourth quadrant in the side view.