Compact automated cell counter

#1. Field of the Invention

#This invention lies in the field of hemocytometry and systems in general for the counting of biological cells suspended in fluids. The focus of this invention is on automated cell counting systems.

#2. Description of the Prior Art

#FIG. 1 is a perspective view of a cell counting instrument representing an example of an implementation of the concepts disclosed herein.

#FIG. 2 is a diagram of the optical components of the instrument of FIG. 1.

#FIG. 3 is a perspective view of optical components in the interior of the instrument of FIG. 1.

#The upper and lower optical windows between which the cell suspension is retained inside the sample vessel are close enough that the retained suspension is a thin film whose lateral dimensions, i.e., its exposed length and width, are at least an order of magnitude greater that its thickness. The entire exposed area (i.e., lateral dimensions) of the sample chamber or a laterally dimensioned portion thereof serves as a field of view that is projected onto a digital imaging sensor that contains at least about 4,000,000 (four million) pixels, or in certain embodiments from about 4,000,000 to about 10,000,000 pixels, with each pixel being no greater than about 2×2 μm (4 μm2) in size, or from about 0.5×0.5 μm (0.25 μm2) to about 2×2 μm (4 μm2) in certain embodiments, and in certain of the latter from about 1×1 μm (1 μm2) to about 2×2 μm (4 μm2) The field of view imaged by the sensor is at least about 3 square millimeters, and often from about 3 mm2 to about 110 mm2. A complementary metal oxide semiconductor (CMOS) is one example of a digital imaging sensor useful for this purpose. Examples of CMOS sensors meeting these parameters are the OV5620 and OV5632 color imagers available from OmniVision, Santa Clara, Calif., USA. Other examples are available from Aptina Imaging, a division of Micron Technology, Inc., of San Jose, Calif., USA. A color digital imaging sensor can also be used. Image processing to count the cells in the image generated by the CMOS sensor can be achieved by known digital counting methods, such as those mentioned above.

#The image of the sample chamber can be magnified along the optical path by a magnification that is often within a range of from about 1.5 to about 6, or a range of from about 1.5 to about 3, with a magnification of about 2 as an example. This can be achieved by a two-lens achromat assembly. An example of such a lens assembly is a lens of 35-mm focal length closest to the sample, a lens of 60-mm focal length closest to the sensor, and an aperture between the two lenses. The distance between the lens nearest the sample and the sample itself in this example is thus 35 mm, and the distance between the lens nearest the sensor and the imager itself is 60 mm. The magnification of the system is the ratio of the focal lengths of the two lenses, which in this case is 60 mm/35 mm=1.7. The two lenses can each for example be 12.5 mm in diameter, and the aperture can be 6 mm in diameter. Lenses of other diameters and focal lengths that will produce the same or approximately the same results will be readily apparent to those skilled in the art. The footprint of the instrument is defined as the area projected by the larger of the instrument and its support base on a plane perpendicular to the optical path. As noted above, the instrument can be constructed with a small footprint, particularly one that is less than 300 cm2 in area.

#When a flat digital imaging sensor is used, a negative lens can be positioned below the sensor to intercept the optical signal immediately and to correct the focus field curvature of the achromat lens pair. This type of field curvature is common in optical systems and is also referred to as Petzval curvature. In an illustrative embodiment, a 6 mm-diameter lens with a minus-18 mm focal length is used. The lens thickness can vary but is optimally selected to correct the curvature without substantially reducing the field of view.