Window blind

A window blind, comprising:

• a first rail;
• a second rail;
• a lifting module connected to the first rail;
• a first cord and a second cord, each of which passes through and extends out of the first rail, and has an end connected to the lifting module and another end connected to the second rail;
• a plurality of slats located between the first cord and the second cord;
• a ladder tape which comprises at least two warps, wherein the slats are suspended between the first rail and the second rail through the ladder tape, and the slats are located between the warps;
• a modulation mechanism, which is adapted to drive the warps of the ladder tape to make a relative movement in a vertical direction, whereby to drive the slats to turn between a first position and a second position;
• and
• an adjustment unit located between the lifting module and the slats, wherein the first cord passes through the adjustment unit;
• wherein the first cord and the second cord are adapted to be driven to move the second rail toward or away from the first rail, whereby to raise or lower the slats;
• when the slats are fully lowered and are in the first position, a length of a segment of each of the first cord and the second cord between a bottom edge of the first rail and a top edge of the second rail is defined as a first length;
• when the slats are driven by the modulation mechanism to turn from the first position to the second position, the adjustment unit is driven to move the first cord, wherein, at this time, a length of a segment of the first cord between the bottom edge of the first rail and the top edge of the second rail is defined as a second length;
• the second length is different from the first length.