4.在正方体ABCD−A1B1C1D1ABCD-A_{1}B_{1}C_{1}D_{1}ABCD−A1B1C1D1中,棱长为2,平面α\alphaα经过点AAA,且满足直线AA1AA_{1}AA1与平面α\alphaα所成角为45∘45\circ45∘,过点A1A_{1}A1作平面α\alphaα的垂线,垂足为HHH,则CHCHCH长度的取值范围为((( )))