Nearly 40 years ago, the Supreme Court held in Diamond v. Diehr that while patent claims directed solely to abstract ideas, such as mathematical formulas, are not patent eligible, a claim containing a mathematical formula would be patent eligible if it “implements or applies that formula in a structure or process which, when considered as a whole, is performing a function which that patent laws are designed to protect.”[1] While the claims in Diehr included a well-known equation for the temperature dependence of a reaction rate, they were found to be patent eligible because they were directed to an improvement in the process of curing rubber.

The answer to the question of whether a claim recites “a function which the patent laws were designed to protect” is not always a clear one. The Federal Circuit’s recent decision in Thales Visionix, Inc. v. United States [2] provides some insights into what is considered a patent-eligible function.

Thales addresses patent eligibility of claims for determining an orientation of an object relative to a moving reference frame. The patent at issue, U.S. Patent No. 6,474,159(the ’159 patent), recognized that in traditional methods that used inertial sensors to track the motion of an object relative to the earth, small errors in measurements for acceleration and/or angular velocity may build up over time, requiring intermittent correction. To address these problems, the claimed invention tracks the movement of the object relative to the moving platform, instead of tracking both the object and the platform relative to the earth and then fusing the data. By eliminating inertial calculations with respect to the earth, the system may be simplified and sources of potential errors may be reduced.[3]

The technology was alleged to be utilized in the helmet-mounted display system for the F-35 Fighter. However, the patent claims at issue are broad enough to cover a wide variety of other applications. For example, an independent tracking system claim recites only “a first inertial sensor mounted on the tracked object”, “a second inertial sensor mounted on the moving reference frame”, and “an element adapted to receive signals from said first and second inertial sensors and configured to determine an orientation of the object relative to the moving reference frame based on the signals received from the first and second inertial sensors.” An even shorter independent method claim recites: “A method comprising determining an orientation of an object relative to a moving reference frame based on signals from two inertial sensors mounted respectively on the object and on the moving reference frame.”

The Federal Circuit analyzed the claims of the ’159 patent applying the two-part Mayo/Alice framework. In step one, the Federal Circuit determined if the claims are directed to an abstract idea. The Federal Circuit noted that the claims were “nearly indistinguishable from the claims at issue in Diehr,” and not merely directed to the abstract idea of using “mathematical equations for determining the relative position of a moving object to a moving reference frame.”[4] Instead, the mathematical equations utilized by the claims “serve only to tabulate the position and orientation information” of a particular configuration of inertial sensors. As the claims of Diehr “reduced the likelihood that the rubber molding process would result in overcuring or undercuring,” the claims of the ’159 patent are “directed to systems and methods that use inertial sensors in a non-conventional manner to reduce errors in measuring the relative position and orientation of a moving object on a moving reference frame.”[5] The Federal Circuit held that the claims at issue are not directed to an abstract idea because the claims “specify a particular configuration of inertial sensors . . . in order to more accurately calculate the position and orientation of an object on a moving platform.”[6] “[T]he claims seek to protect only the application of physics to the unconventional configuration of sensors as disclosed.”[7]

The Federal Circuit decision appears to be unusual for several reasons. First, despite being characterized as “nearly indistinguishable” from the claims in Diehr, the independent claims of the ’159 patent do not recite any particular mathematical equation. At most, the mathematical equation is implicit in the recited limitations of determining the orientation of the object based on the sensor data.[8] Diverging from the reasoning of Diehr, the decision appears to place heavy emphasis on the “unconventional choice of reference frame” and the “unconventional configuration of sensors.”[9]

Second, the decision does not address the breadth of the claims. In particular, the method claim recites merely “determining an orientation of an object relative to a moving reference frame based on signals from two inertial sensors mounted respectively on the object and on the moving reference frame.” There is no requirement that the recited steps be performed by a machine. Such a claim may fall into the ineligible category of abstract ideas encompassing mental processes. See, e.g., Elec. Power Grp., LLC v. Alstom S.A., 830 F.3d 1350, 1354 (Fed. Cir. 2016) (“[W]e have treated analyzing information by steps people go through in their minds, or by mathematical algorithms, without more, as essentially mental processes within the abstract-idea category.”).

Notwithstanding, because the Federal Circuit decision appears to place a heavy emphasis on the unconventional configuration and placement of the sensors and the resulting improvements,[10] patent applications should identify unconventional aspects of the claimed invention and carefully consider why and how it improves the prior art. By emphasizing these aspects in the specification, an applicant may improve the chances that claims will be found to be patent-eligible even if they involve the use of mathematical formulas.