1. An image acquiring apparatus comprising: micro image acquiring means for acquiring a micro image of a sample by scanning the sample at a predetermined resolution; image pickup condition setting means for setting, for the sample, an image acquiring range corresponding to a range including an object of image acquisition and focus information concerning the image acquisition of the object in the image acquiring range; and micro image acquisition control means for controlling an operation for acquiring the micro image of the micro image acquiring means, wherein the micro image acquiring means has an image pickup device capable of acquiring a one-dimensional image or a two-dimensional image and sets one direction on an image pickup plane in the image pickup device as a scanning direction for acquiring the micro image, the micro image acquisition control means performs control so that a partial image is acquired by scanning the sample in the scanning direction by the image pickup device and a plurality of partial images that become the micro image are acquired by repeating this partial image acquisition a plurality of times while changing an image pickup position along another direction of the image pickup plane, and when at least a first image acquiring range and a second image acquiring range are set as the image acquiring range, the image pickup condition setting means sets three or more first focus measuring positions in the first image acquiring range, and sets first focus information as the focus information for the first image acquiring range by referring to results of focus measurements on the first focus measuring positions performed by using the micro image acquiring means, sets three or more second focus measuring positions in the second image acquiring range, and sets second focus information as the focus information for the second image acquiring range by referring to results of focus measurements on the second focus measuring positions performed by using the micro image acquiring means, and when a partial image among the plurality of partial images includes mixing of a first region belonging to the first image acquiring range and a second region belonging to the second image acquiring range, the focus information is switched between the first focus information and the second focus information in the respective first region and second region to perform scanning of the sample for acquiring the partial image, and wherein when at least a first object and a second object are discriminated as the object, the image pickup condition setting means sets the first image acquiring range and the second image acquiring range for the sample by dividing an image of the sample between an image of the first object and an image of the second object, and in dividing the image of the sample, a boundary between the first object and the second object, obtained by applying dilation processing to the image of the first object and the image of the second object, is set as a dividing line for the first image acquiring range and the second image acquiring range.