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Patent Law: What is the Written Description Requirement?

By John DiGiacomo

A “written description” is one of the many requirements for obtaining a patent. The written description requirement is contained in the Patent Act which states that the “specification shall contain a written description of the invention in such full, clear, concise, and exact terms as to enable any person skilled in the art . . . to make and use the same.” See 35 U.S.C. 112(a). This requirement is separate and distinct from other requirements of patentability. Essentially, the written description requirement implements the Patent Act’s requirement that a person or entity seeking a patent must describe the technology that is sought to be patented. According to case law, the written description requirement serves several goals including:

  • Satisfies the inventor’s obligation to disclose the technologic knowledge upon which the patent is based
  • Demonstrates that the patentee was in possession of the invention that is claimed
  • Promotes the progress of the useful arts by ensuring that patentees adequately describe their inventions in their patent specifications in exchange for the right to exclude others from practicing the invention for the duration of the patent’s term

Written description patent invalidity is most often found in cases of continuation or continuation-in-part patent applications where the earlier-filed application fails to describe the invention contained in the later-filed application. A case that provides a pretty clear example is Research Corp. Technologies v. Microsoft Corp., 627 F.3d 859 (Fed. Cir. 2010). The relevant earlier-filed patent application had these claims related to a “blue noise mask” use for halftoning printer and computer screen images:

  • A method for the halftoning of gray scale images by utilizing a pixel-by-pixel comparison of the image against a blue noise mask in which the blue noise mask is comprised of a random non-deterministic, non-white noise single valued function which is designed to produce visually pleasing dot profiles when thresholded at any level of said gray scale images.
  • The method of claim 1, wherein said blue noise mask is used to halftone a color image.

The subsequently-filed patent application contained these claims related to a “blue noise dot profile” technique:

  • The machine of claim 1, wherein substantially all of said number of dot profiles have a power spectrum substantially characteristic of a blue noise power spectrum for the level at which such a dot profile is produced.
  • The computer readable memory device of claim 57, wherein said halftoning mask is designed to produce substantially all visually pleasing dot profiles when thresholded at a number of levels.

Based on an examination of the facts presented, the court concluded that a “blue noise mask” is different from a “blue noise dot profile.” The court noted that the relevant inventors had testified that they were in possession of only a blue noise mask at the time of filing the original patent applications. Further, one of the inventors admitted that the earlier-filed applications did not describe any masks other than a blue noise mask. The court held that the earlier-filed application did not describe the blue noise dot profile invention. As such, Claims 4 and 63 of the later-filed application were not entitled to claim the priority date of the earlier-filed patent application.

A challenge based on the written description requirement can also be made in cases NOT involving a continuation patent. There are cases where the patent examiner will reject a patent claim based on a failure of written description. As a practical matter, amending the patent claim or claims might be sufficient to overcome the objection. For more information or if you have questions about applying for a patent, contact the patent lawyers at Revision Legal at 231-714-0100.

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