the invention will be described with reference to a full face helmet and face shield shown in fig1 and 2 which has an integrally formed protective chin portion 1 . there is a cut out face portion 2 over the eyes and nose which may be optionally covered by a face shield 3 which is rotatable upwardly to expose the face portion and allow access to the face . the portion of the face shield covering the cut out face portion will be hereinafter referred to as the lense or outer lense 6 and the surrounding face shield as the frame portion 9 . referring to fig3 , a gapped uniform space gap is formed underneath the outer lense 6 having an equal thickness t and perimeter shape substantially equal to the perimeter shape of the lense area covering the face portion of the helmet . according to one embodiment , the gapped space is formed by uniformly raising the outer lense 6 of the face shield a distance t with reference to the surrounding frame portion 9 of the face shield , as shown in fig3 . an inner lense 7 having a perimeter shape identical to but slightly smaller than the lense portion is fitted into the gapped space and adhesively secured in place along its perimeter with two sided tape 8 in spaced apart relationship to the outer lense . the air space distance d between the lenses is preferably approximately one ( 1 ) mm . it can be appreciated that the thickness of the gapped space t must be at least equal to the thickness of the inner lense and air space thickness d . the inner lense is made of the same material as the outer lense . the field of vision through the face shield is unaffected and the strength of the face shield is unaltered . the compound curvature of the inner lense is made identical to the compound curvature of the outer lense so that the optical characteristics of the face shield are unaffected . another approach to forming the gapped space underneath the outer lense is to start with a thicker face shield and remove lense material to a thickness t from underneath the lense . in any event , the objective is to create a smooth uninterrupted inner surface for the face shield . the inside surface of the inner lens is coterminous with the inside surface of the frame portion . by this means the pivoting action of the face shield from a first closed position covering the face opening to a second open position exposing the face is not impeded or interfered with by the inner lense . it is accordingly important to ensure that the inside surface of the inner lense does not extend outwardly beyond the inner surface of the frame portion of the face shield . according to the present invention , the outside surface of the outer lense may be coated for hardness the inside surface of the outer lense is uncoated as is the outside surface of the inner lense . in other words , the facing surfaces across distance d in the air space are uncoated which facilitates adhesion of the lenses along the common perimeter with double sided tape . the inner surface of the inner lense is preferably coated with an antifogging solution . another advantage of the present invention is the resulting strength and rigidity of the face shield enables the helmet to pass standardized impact tests in the us and uk . according to another aspect of the invention , the inner lense can be replaced with a combination lense that has electrical conductivity features which further improve anti - fog characteristics . as shown in fig4 , the inner lense is comprised of two layers of materials . a first layer of lense material 7 and a thin layer of indium tin oxide ( ito ) material 10 is bonded to the outside of the inner lense . the ito material is very delicate and requires special handling and needs to be applied in a sterilized clean room . the thickness of the combined ito and inner lense is the same as the thickness of the inner lense without the coating . the ito material is electrically conductive . thus the application of ito creates an electrically conductive lense for fog prevention . other advantages which are inherent to the invention are obvious to one skilled in the art . the embodiments are described herein illustratively and are not meant to limit the scope of the invention as claimed . variations of the foregoing embodiments will be evident to a person of ordinary skill and are intended by the inventor to be encompassed by the following claims .
a face shield or visor for a helmet which has a second lense fitted into a gapped space underneath the first lense and has improved anti fogging properties .