An arrangement comprising a test device and a microfluidic device, wherein the microfluidic device is a disk type microfluidic device which has a microfluidic structure arranged on a disk-shaped platform to move a fluid using centrifugal force to perform a series of operations, the microfluidic device including a chamber to detect an analyte or test material and a detection object, and wherein the detection object comprises a test paper upon which a predetermined biochemical reaction of a biomaterial is performed, the test device configured to detect the detection object and comprising: a light emitting element to emit light onto the microfluidic device; and a light receiving element to capture an image of the test paper through light emitted from the light emitting element; the test device being an apparatus provided with the light emitting element and the light receiving element to detect the detection object of the microfluidic device and thus detect results of biochemical reactions occurring within the detection object; the test device further comprising: a rotary drive unit to rotate the microfluidic device; and a controller to compute a signal value for at least one predetermined area (26, 27) on the image of the test paper captured by the light receiving element and adjust an exposure level of the light receiving element according to a difference between the computed signal value and a predetermined target value, wherein the signal value comprises at least one of an RGB signal value, a YCbCr signal value and a Gray-scale signal value, and the controller adjusts the exposure level of the light receiving element by controlling iris opening of the light receiving element. a light emitting element to emit light onto the microfluidic device; and a light receiving element to capture an image of the test paper through light emitted from the light emitting element; the test device being an apparatus provided with the light emitting element and the light receiving element to detect the detection object of the microfluidic device and thus detect results of biochemical reactions occurring within the detection object; the test device further comprising: a rotary drive unit to rotate the microfluidic device; and a controller to compute a signal value for at least one predetermined area (26, 27) on the image of the test paper captured by the light receiving element and adjust an exposure level of the light receiving element according to a difference between the computed signal value and a predetermined target value, wherein the signal value comprises at least one of an RGB signal value, a YCbCr signal value and a Gray-scale signal value, and the controller adjusts the exposure level of the light receiving element by controlling iris opening of the light receiving element. a rotary drive unit to rotate the microfluidic device; and a controller to compute a signal value for at least one predetermined area (26, 27) on the image of the test paper captured by the light receiving element and adjust an exposure level of the light receiving element according to a difference between the computed signal value and a predetermined target value, wherein the signal value comprises at least one of an RGB signal value, a YCbCr signal value and a Gray-scale signal value, and the controller adjusts the exposure level of the light receiving element by controlling iris opening of the light receiving element.