[770]*770PER CURIAM.
International Visual Corporation (IVC) appeals from the March 9, 1992 judgment of the United States District Court for the Northern District of Illinois granting summary judgment of noninfringement in favor of Crown Metal Manufacturing. International Visual Corp. v. Crown Metal Mfg. Co., 22 USPQ2d 1778, 1992 WL 38376 (N.D.Ill.1992). Because we determine that the district court incorrectly interpreted the claims of IVC’s U.S. Patent 4,677,780, we reverse and remand.
BACKGROUND
The ’780 patent is entitled “Magnetically Secured Display Apparatus.” On August 10, 1989, IVC filed a complaint alleging that Crown’s GRIPPER device infringed claims 1-3 and 6-10 of the patent. Crown counterclaimed for a declaratory judgment of noninfringement, invalidity, and unen-forceability. IVC then moved for summary judgment on the issues of infringement, willful infringement, and Crown’s invalidity defense, and Crown moved for summary judgment of invalidity and unenforceability, but did not move for summary judgment of noninfringement. The • district court denied IVC’s motion, granted Crown’s motion on the ground of nonin-fringement, and dismissed the case in its entirety.
DISCUSSION
The issue before us is whether the district court properly granted summary judgment of noninfringement. We review the district court’s grant of summary judgment de novo, see National Cable Television Ass’n v. American Cinema Editors, Inc., 937 F.2d 1572, 1576, 19 USPQ2d 1424, 1427 (Fed.Cir.1991), and specifically determine whether the court’s claim interpretation was legally correct. Palumbo v. Don-Joy Co., 762 F.2d 969, 974, 226 USPQ 5, 8 (Fed.Cir.1985).
At the outset, we reject IVC’s argument that the district court was precluded from granting summary judgment of nonin-fringement on the ground that Crown did not specifically move for summary judgment on that issue. “[Djistrict courts are widely acknowledged to possess the power to enter summary judgments sua sponte, so long as the losing party was on notice that she had to come forward with all of her evidence.” Celotex Corp. v. Catrett, 477 U.S. 317, 326, 106 S.Ct. 2548, 2554, 91 L.Ed.2d 265 (1986). In the instant case, the record clearly shows that IVC had notice that the issue of noninfringement was before the court on the parties’ cross-motions for summary judgment. IVC in fact stated that “the infringement issue is now ripe for summary adjudication,” and argued the issue of infringement, both literal and under the doctrine of equivalents, on several occasions. Thus, summary judgment of nonin-fringement for Crown was not precluded merely because Crown did not move for. summary judgment on that ground.
Literal Infringement
The court held that the GRIPPER did not infringe independent claims 1 and 10,1 either literally or under the doctrine of [771]*771equivalents.2 As to literal infringement, the court held that the GRIPPER did not meet the “housing limitation” and “[accordingly, ... [did] not literally infringe independent claims 1 and 10 of the ’780 patent as a matter of law.” 22 USPQ2d at 1780. Consequently, the court held that there was no literal infringement of dependent claims 2, 3, and 6-9.
The court described the GRIPPER as follows:
The defendant’s GRIPPER clamp consists of a permanent bar magnet secured into a U-shaped ferromagnetic “channel member” which has been bent into an L-shape. There is no separate housing since the U-shaped channel functions as a receptacle for the bar magnets and as a pole piece to significantly increase the magnetic strength of the flat bar magnets.
Id. at 1779 (emphasis added). The court concluded:
The GRIPPER undisputedly does not have a housing separate and apart from the components of the operational magnet (i.e., the permanent bar magnet and the pole pieces). This housing limitation set forth in the ’780 patent is not found exactly in the accused GRIPPER.
Id. at 1780 (emphasis added).
IVC argues that the district court’s interpretation of the “housing” limitation was erroneous. It asserts that the court erroneously interpreted claim 1 to require that it be “separate and apart” from the permanent magnet means. We agree. Claim 1 requires a clamp means that includes an L-shaped tubular housing and a permanent magnet means integrally connected to the first leg portion of the housing. There is no “separate and apart” limitation in the claims; that phrase appears nowhere in the ’780 patent. The term “integrally connected” in claim 1 is inconsistent with a requirement that the housing and permanent magnet be “separate and apart.” Crown in fact conceded at oral argument that the GRIPPER channel member is a “housing” within the meaning of the claim.
The implication of the court’s conclusion that there also is no infringement of claim 10 is that the court considered that claim 10 requires a housing. Claim 10, however, unlike claim 1, does not require a “housing,” but includes a “clamp portion being generally L-shaped and having a tubular horizontal leg ... and a tubular vertical leg.” Moreover, the requirement that the magnet means be in the tubular vertical leg of the clamp is inconsistent with the court’s requirement of separateness between the magnet and a housing.
We also agree with IVC that the court incorrectly construed the claims to require a plastic housing. The specification of the ’780 patent describes a plastic housing only as a preferred embodiment of the invention; Crown conceded at oral argument that the claims are not so limited. In concluding that the claims are limited to a plastic housing, the court apparently fo[772]*772cused on the HUGGER, IVC’s commercial embodiment of the ’780 patent, which has a plastic housing. This was erroneous since “[infringement is determined on the basis of the claims, not on the basis of a comparison with the patentee’s commercial embodiment of the claimed invention.” ACS Hosp. Sys., Inc. v. Montefiore Hosp., 732 F.2d 1572, 1578, 221 USPQ 929, 933 (Fed.Cir.1984). Thus, because of erroneous claim construction, the court's conclusions on literal infringement must be reconsidered.
Doctrine of Equivalents
The court also examined the question of infringement under the doctrine of equivalents and concluded that the GRIPPER performed substantially the same function in substantially the same way to obtain substantially the same result as the ’780 invention. 22 USPQ2d at 1781. It nevertheless held that there was no infringement under the doctrine of equivalents because the range of equivalents sought by IVC “would have been obvious” in view of a French patent to Delenne. Id. at 1782. In so holding, the court employed the “hypothetical claim” approach of Wilson Sporting Goods Co. v. David Geoffrey & Assoc., 904 F.2d 677, 14 USPQ2d 1942 (Fed.Cir.), cert. denied,
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[770]*770PER CURIAM.
International Visual Corporation (IVC) appeals from the March 9, 1992 judgment of the United States District Court for the Northern District of Illinois granting summary judgment of noninfringement in favor of Crown Metal Manufacturing. International Visual Corp. v. Crown Metal Mfg. Co., 22 USPQ2d 1778, 1992 WL 38376 (N.D.Ill.1992). Because we determine that the district court incorrectly interpreted the claims of IVC’s U.S. Patent 4,677,780, we reverse and remand.
BACKGROUND
The ’780 patent is entitled “Magnetically Secured Display Apparatus.” On August 10, 1989, IVC filed a complaint alleging that Crown’s GRIPPER device infringed claims 1-3 and 6-10 of the patent. Crown counterclaimed for a declaratory judgment of noninfringement, invalidity, and unen-forceability. IVC then moved for summary judgment on the issues of infringement, willful infringement, and Crown’s invalidity defense, and Crown moved for summary judgment of invalidity and unenforceability, but did not move for summary judgment of noninfringement. The • district court denied IVC’s motion, granted Crown’s motion on the ground of nonin-fringement, and dismissed the case in its entirety.
DISCUSSION
The issue before us is whether the district court properly granted summary judgment of noninfringement. We review the district court’s grant of summary judgment de novo, see National Cable Television Ass’n v. American Cinema Editors, Inc., 937 F.2d 1572, 1576, 19 USPQ2d 1424, 1427 (Fed.Cir.1991), and specifically determine whether the court’s claim interpretation was legally correct. Palumbo v. Don-Joy Co., 762 F.2d 969, 974, 226 USPQ 5, 8 (Fed.Cir.1985).
At the outset, we reject IVC’s argument that the district court was precluded from granting summary judgment of nonin-fringement on the ground that Crown did not specifically move for summary judgment on that issue. “[Djistrict courts are widely acknowledged to possess the power to enter summary judgments sua sponte, so long as the losing party was on notice that she had to come forward with all of her evidence.” Celotex Corp. v. Catrett, 477 U.S. 317, 326, 106 S.Ct. 2548, 2554, 91 L.Ed.2d 265 (1986). In the instant case, the record clearly shows that IVC had notice that the issue of noninfringement was before the court on the parties’ cross-motions for summary judgment. IVC in fact stated that “the infringement issue is now ripe for summary adjudication,” and argued the issue of infringement, both literal and under the doctrine of equivalents, on several occasions. Thus, summary judgment of nonin-fringement for Crown was not precluded merely because Crown did not move for. summary judgment on that ground.
Literal Infringement
The court held that the GRIPPER did not infringe independent claims 1 and 10,1 either literally or under the doctrine of [771]*771equivalents.2 As to literal infringement, the court held that the GRIPPER did not meet the “housing limitation” and “[accordingly, ... [did] not literally infringe independent claims 1 and 10 of the ’780 patent as a matter of law.” 22 USPQ2d at 1780. Consequently, the court held that there was no literal infringement of dependent claims 2, 3, and 6-9.
The court described the GRIPPER as follows:
The defendant’s GRIPPER clamp consists of a permanent bar magnet secured into a U-shaped ferromagnetic “channel member” which has been bent into an L-shape. There is no separate housing since the U-shaped channel functions as a receptacle for the bar magnets and as a pole piece to significantly increase the magnetic strength of the flat bar magnets.
Id. at 1779 (emphasis added). The court concluded:
The GRIPPER undisputedly does not have a housing separate and apart from the components of the operational magnet (i.e., the permanent bar magnet and the pole pieces). This housing limitation set forth in the ’780 patent is not found exactly in the accused GRIPPER.
Id. at 1780 (emphasis added).
IVC argues that the district court’s interpretation of the “housing” limitation was erroneous. It asserts that the court erroneously interpreted claim 1 to require that it be “separate and apart” from the permanent magnet means. We agree. Claim 1 requires a clamp means that includes an L-shaped tubular housing and a permanent magnet means integrally connected to the first leg portion of the housing. There is no “separate and apart” limitation in the claims; that phrase appears nowhere in the ’780 patent. The term “integrally connected” in claim 1 is inconsistent with a requirement that the housing and permanent magnet be “separate and apart.” Crown in fact conceded at oral argument that the GRIPPER channel member is a “housing” within the meaning of the claim.
The implication of the court’s conclusion that there also is no infringement of claim 10 is that the court considered that claim 10 requires a housing. Claim 10, however, unlike claim 1, does not require a “housing,” but includes a “clamp portion being generally L-shaped and having a tubular horizontal leg ... and a tubular vertical leg.” Moreover, the requirement that the magnet means be in the tubular vertical leg of the clamp is inconsistent with the court’s requirement of separateness between the magnet and a housing.
We also agree with IVC that the court incorrectly construed the claims to require a plastic housing. The specification of the ’780 patent describes a plastic housing only as a preferred embodiment of the invention; Crown conceded at oral argument that the claims are not so limited. In concluding that the claims are limited to a plastic housing, the court apparently fo[772]*772cused on the HUGGER, IVC’s commercial embodiment of the ’780 patent, which has a plastic housing. This was erroneous since “[infringement is determined on the basis of the claims, not on the basis of a comparison with the patentee’s commercial embodiment of the claimed invention.” ACS Hosp. Sys., Inc. v. Montefiore Hosp., 732 F.2d 1572, 1578, 221 USPQ 929, 933 (Fed.Cir.1984). Thus, because of erroneous claim construction, the court's conclusions on literal infringement must be reconsidered.
Doctrine of Equivalents
The court also examined the question of infringement under the doctrine of equivalents and concluded that the GRIPPER performed substantially the same function in substantially the same way to obtain substantially the same result as the ’780 invention. 22 USPQ2d at 1781. It nevertheless held that there was no infringement under the doctrine of equivalents because the range of equivalents sought by IVC “would have been obvious” in view of a French patent to Delenne. Id. at 1782. In so holding, the court employed the “hypothetical claim” approach of Wilson Sporting Goods Co. v. David Geoffrey & Assoc., 904 F.2d 677, 14 USPQ2d 1942 (Fed.Cir.), cert. denied, 498 U.S. 992, 111 S.Ct. 537, 112 L.Ed.2d 547 (1990).
Hypothetical claim analysis is an optional way of evaluating whether prior art limits the application of the doctrine of equivalents. It is simply a way of expressing the well-established principle “that a patentee should not be able to obtain, under the doctrine of equivalents, coverage which he could not lawfully have obtained from the PTO by literal claims.” Id. at 684, 14 USPQ2d at 1948. If utilized, this approach requires a court to visualize a hypothetical claim that enlarges the scope of an issued claim so that it literally covers an accused device and to determine whether that hypothetical claim would have been patentable over the prior art. Id. at 684-85, 14 USPQ2d at 1948-49; Jurgens v. McKasy, 927 F.2d 1552, 1561, 18 USPQ2d 1031, 1038 (Fed.Cir.), cert. denied, — U.S. -, 112 S.Ct. 281, 116 L.Ed.2d 232 (1991).
The trial court here utilized a hypothetical claim in its analysis, stating:
The ‘angular’ clamping mechanism of the Delenne ’224 is, like the hypothetical claim, a two-legged L-shaped magnetic assembly, without a separate housing, which attaches to a ‘square section’ of a rod.
22 USPQ2d at 1782 (emphasis added). However, because the court based its conclusion that the GRIPPER literally escaped the ’780 claims only by lacking a housing “separate and apart” from the permanent magnet means, a distinction that we now hold to be based upon an erroneous claim interpretation, it is not clear that a suitable hypothetical claim that covers the GRIPPER would necessarily have been obvious over Delenne. Thus, remand is appropriate based on our claim interpretation. On the other hand, on remand the court may decide that, in light of its new analysis of literal infringement, if it concludes there is infringement, application of the doctrine of equivalents is not necessary.
CONCLUSION
We reverse the court’s grant of summary judgment of noninfringement, and remand for proceedings consistent with this opinion.
COSTS
Each party shall bear its own costs.
REVERSED AND REMANDED.
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APPENDIX