已知实数 a,b,c,da,b,c,da,b,c,d 满足 b=2lna,d=2c+1b = 2\ln a,d = {2c} + 1b=2lna,d=2c+1 ，则 (a−c)2+(b−d)2{\left( a - c\right) }^{2} + {\left( b - d\right) }^{2}(a−c)2+(b−d)2 的最小值___.