Abstract: A system for approximating flux density of light on a human retina. A housing has an opening allowing light to pass to inside the housing. A baffle coupled to the housing replicates a facial cutoff function response for the light inside the housing. Two detectors are positioned to detect the light inside the housing. One detector produces a photopic spectral response function of the light inside the housing that approximately replicates a spectral response of the foveal cones in the retina. Another detector produces a scotopic spectral response function of the light inside the housing that approximately replicates a spectral response of rods in the retina. A processor coupled to the detectors calculates a mesopic flux density of the light inside the housing based on the photopic and scotopic spectral response functions.

Abstract: An eye characteristic measuring apparatus can effectively and properly measure and display wavefront aberration of an eye regardless of the eye state. A first illumination optical system (200A) illuminates a small area on a retina of the eye by a first light flux from a first light source unit (100). A first reception light optical system (300A) leads a part of light flux reflected from the retina (61) to a first light reception unit (510) via a first conversion member (400) for converting the reflected light flux into at least 17 beams. A measurement data judgment unit, for example, judges whether the measurement data is appropriate for calculating the wavefront aberration according to a first signal from the first light reception unit (510). For example, when the measurement data judgment unit judges that the measurement data is not appropriate, a first correction unit causes to display a check correction screen which will be detailed later and corrects the data into appropriate measurement data.

Abstract: Measurement of an eye characteristic is performed more accurately and at high speed by setting a measurement condition of a light receiving optical system with a long focal point or high sensitivity on the basis of an optical characteristic measured by a light receiving optical system with a short focal point or low sensitivity or high density. The optical characteristic of the subject eye is obtained on the basis of an output of a first light receiving part and/or a second light receiving part, and a change direction of the beam is estimated on the basis of an output signal from the second light receiving part.

Abstract: An optometric apparatus for a subjective examination of a visual function of an eye of an examinee includes a pair of right and left lens chamber units, each including, a test window and a rotating disk on which a plurality of optical elements are mounted in a circumferential arrangement to be changeably placed in the test window, the optical elements including a green filter and an aperture.

Abstract: An optometric apparatus (1) for subjectively examining a visual function of an examinee's eye, includes: a pair of right and left lens chamber units (5), each including a test window (5a) and optical elements to be changeably disposed in the test window; a support unit (6) which supports the lens chamber units so that the units may be converged; a near vision examination chart (2, 3) to be disposed at a changeable distance from the test window; and an illumination unit (7) which illuminates the near vision chart, the illumination unit being provided in each lens chamber unit.

Abstract: A novel contrast sensitivity test utilizing an adaptive contrast threshold algorithm is proposed. The contrast sensitivity test is embodied as a two-alternative forced choice examination using grating stimuli of randomly interleaved spatial frequencies. The stimulus's orientation is either tilted to the left or right of vertical. During an examination, a succession of grating stimuli is presented to the subject, and the subject asked to indicate the orientation of each stimulus. The contrast level for the next stimulus is varied depending on the subject's response to the previous one using an adaptive weighted up-down algorithm. For each correct response, the contrast level is reduced, whereas for each incorrect response the contrast level is increased. Importantly, the amount by which the contrast level is lowered is different from the amount by which it is raised, and as the examination progresses, the amount changes.

Abstract: Apparatus for measuring accommodation of a lens in an eye includes a target, a Badal lens, and a viewing aperture, where the Badal lens and the viewing aperture are positioned so that when the target moves towards or away from the lens, the apparent size of the target remains constant to a subject looking in the viewing aperture regardless of the distance the target moves. The apparatus may be provided in a compact housing and may include a mirror placed in the housing so that the viewing aperture can be placed away from the optical axis of the lens. The apparatus includes a controller to control the movement of the target. The apparatus measures the accommodation of a lens based on the distance the target moves during an examination. Methods of measuring accommodation of a lens in an eye of a subject are also disclosed.

Abstract: A display device (1) has a photon source (20) that displays an image scene in which the user perceives points at differents distances, resulting in optical stimulation of the eye's accommodative response. This is achieved by an intermediate optical system (21) forming the photons into pencils and a variable power optical system (22) positioned for convergence of the pencils. A control system (8) controls the variable power optical system (22) to modulate photon wavefront curvature according to image pixel co-ordinate and intensity data and data representing required perceived pixel distance.

Abstract: One embodiment of the present invention is a visual field tester that includes: (a) a projection screen; (b) a stimulus projection system that projects a light stimulus onto a first side of the projection screen; and (c) a background projection system that projects background light onto the first side of the projection screen; wherein the stimulus projection system includes: (i) a first rotatable disk having an aperture; (ii) a second rotatable disk disposed in the aperture; and (iii) a stimulus radiation projector that includes a stimulus radiation source and a radiation projection lens system that are configured to project the stimulus from the second disk onto the first side of the projection screen.

Abstract: This invention is a programmable vision testing apparatus and method for use in conducting optometric examinations of video display terminal (VDT) users. The apparatus uses a digital display screen accurately to represent a VDT used under actual work conditions. Further, a plurality of images can be displayed via the vision testing apparatus to provide a convenient and efficient way to test the eyes of VDT users with a wide variety of individual needs.

Abstract: An apparatus for measuring visual performance suitable for carrying out various visual functionality tests in controlled and variable opening conditions of the pupils of a subject. The apparatus uses optic systems for the control of ambient brightness, and uses systems of illumination, observation, and measurement of the pupillary dimensions.

Abstract: Apparatus for measuring accommodation of a lens in an eye includes a target, a Badal lens, and a viewing aperture, where the Badal lens and the viewing aperture are positioned so that when the target moves towards or away from the lens, the apparent size of the target remains constant to a subject looking in the viewing aperture regardless of the distance the target moves. The apparatus may be provided in a compact housing and may include a mirror placed in the housing so that the viewing aperture can be placed away from the optical axis of the lens. The apparatus includes a controller to control the movement of the target. The apparatus measures the accommodation of a lens based on the distance the target moves during an examination. Methods of measuring accommodation of a lens in an eye of a subject are also disclosed.

Abstract: A visual function test apparatus for testing a visual function by presenting an optotype to an examinee's eye is disclosed. This apparatus includes a first half mirror disposed on a projection optical axis of light of the optotype; an illumination light source having a projection optical axis which is made substantially coaxial with the projection optical axis of the optotype light by the first half mirror; a concave mirror which reflects an illumination light from the illumination light source and the optotype light; a second half mirror disposed between the first half mirror and the concave mirror, the second half mirror reflecting the optotype light and the illumination light both reflected by the concave mirror toward the examinee's eye; and a control section which changes a ratio between a light quantity of the optotype light and a light quantity of the illumination light in accordance with a predetermined contrast ratio.

Abstract: A novel contrast sensitivity test utilizing an adaptive contrast threshold algorithm is proposed. The contrast sensitivity test is embodied as a two-alternative forced choice examination using grating stimuli of randomly interleaved spatial frequencies. The stimulus's orientation is either tilted to the left or right of vertical. During an examination, a succession of grating stimuli is presented to the subject, and the subject asked to indicate the orientation of each stimulus. The contrast level for the next stimulus is varied depending on the subject's response to the previous one using an adaptive weighted up-down algorithm. For each correct response, the contrast level is reduced, whereas for each incorrect response the contrast level is increased. Importantly, the amount by which the contrast level is lowered is different from the amount by which it is raised, and as the examination progresses, the amount changes.

Abstract: A flicker sensitivity distribution measuring method is provided to maintain a subject in a fixation state and to accurately measure flicker sensitivity distribution. The sensitivity distribution measuring method includes the steps of displaying a target on a screen of a display while changing high and low luminances of a flickering target stepwise so that the average of the high luminance and the low luminance in each cycle of flickering of the target is always equal to the luminance of the screen serving as a background for the target, and determining a flicker sensitivity on the basis of the high luminance and the low luminance in one cycle of flickering of the target at a moment when the target is perceived.

Abstract: Device and method that allows an objective measure to be taken of the size and morphological pattern of the degradation of the image in scotopic vision. It consists of a black front screen (1) which has a central luminous source (2) surrounded by a grid of circular light spots (3) which at the beginning of the test light up sequentially or at random, according to the method selected, from the nearest to the central source of glare in a centrifuge fashion to the outermost, and a trigger which the patient will press every time he can discriminate the presence of each of the spots in 12 meridians. The non-discriminated or hidden spots will border an area which is interpreted as being occupied by the light aberration and is used as a basis for calculating the glare index.

Abstract: This invention is a programmable vision testing apparatus and method for use in conducting optometric examinations of video display terminal (VDT) users. The apparatus uses a digital display screen accurately to represent a VDT used under actual work conditions. Further, a plurality of images can be displayed via the vision testing apparatus to provide a convenient and efficient way to test the eyes of VDT users with a wide variety of individual needs.

Abstract: A method of determining an eyeglass prescription for correcting a user's vision is provided. The method includes: prompting the user for selective parameters; configuring an eye chart for display based on the selective parameters; receiving sizing input from the user if the user increases or decreases the size of the eye chart until the eye chart appears clear; reconfiguring the eye chart based on the received sizing input; comparing the reconfigured eye chart to the configured eye chart; and determining the eyeglass prescription for correcting the user's vision based on a comparison between the reconfigured eye chart and the configured eye chart. A system for determining an eyeglass prescription for correcting a user's vision is also provided. The system includes a parameter module, a configure module, a receive module, a reconfigure module, a compare module, and a determine module. The parameter module prompts the user for selective parameters.

Abstract: The invention relates to visual field tests, wherein a plurality of visual stimuli are successively presented to a test subject and the responses from the test subject are recorded in order to determine the test subject's perception of visual stimuli. With the aid of a confidence level function and the recorded responses, at least two visual field test values of different confidence levels are calculated. A result of the visual field test and an indication of the confidence thereof, which are based on the two visual field test values of each test location, are displayed to the user.

Abstract: An electronic eye depth testing method comprises a three dimensional cubic space displayed on a display screen, wherein the cubic space has a first image of a three dimensional object and a second image of a three dimensional object randomly placed within the cubic space. The first image is located at the intersection of two perpendicular horizontal planes and a vertical plane perpendicular to said two horizontal planes and the second image is located at the intersection of two perpendicular horizontal planes and a vertical plane perpendicular to said two horizontal planes. A subject to be tested for depth perception is directed to move the images into convergence in the center of the cubic space.

Abstract: A display device (1) has a photon source (20) that displays an image scene in which the user perceives points at differents distances, resulting in optical stimulation of the eye's accommodative response. This is achieved by an intermediate optical system (21) forming the photons into pencils and a variable power optical system (22) positioned for convergence of the pencils. A control system (8) controls the variable power optical system (22) to modulate photon wavefront curvature according to image pixel co-ordinate and intensity data and data representing required perceived pixel distance.

Abstract: This invention is a programmable vision testing apparatus and method for use in conducting optometric examinations of video display terminal (VDT) users. The apparatus uses a digital display screen accurately to represent a VDT used under actual work conditions. Further, a plurality of images can be displayed via the vision testing apparatus to provide a convenient and efficient way to test the eyes of VDT users with a wide variety of individual needs.

Abstract: A test slide is designed for use in a vision testing apparatus. The test slide comprises several component layers. Those layers include a light diffusing layer, an optotype film layer, a color correcting film layer, a frame separator, and a clear glass layer wherein the components are laminated together in the order identified.

Abstract: One embodiment of the present invention is a visual field tester that includes: (a) a projection screen; (b) a stimulus projection system that projects a light stimulus onto a first side of the projection screen; and (c) a background projection system that projects background light onto the first side of the projection screen; wherein the stimulus projection system includes: (i) a first rotatable disk having an aperture; (ii) a second rotatable disk disposed in the aperture; and (iii) a stimulus radiation projector that includes a stimulus radiation source and a radiation projection lens system that are configured to project the stimulus from the second disk onto the first side of the projection screen.

Abstract: The present invention provides a method for establishing fixation during computerized visual field perimetry, requiring the subject to fixate on a stationary target for a brief instance as he/she moves a secondary target towards the stationary target. In a preferred embodiment, the subject interactively moves the secondary target in the shape of crosshairs toward the stationary fixation target displayed on a monitor using the operations of a computer mouse. The stationary fixation target has preferably the shape of a small red circle in order to make it readily identifiable by the subject. The computer mouse pointer when contacted attaches itself to the secondary target. The subject then moves his head so that the fixation target is directly in front of him/her, and, while staring at the fixation target, moves the secondary target towards the stationary fixation target.

Abstract: The present invention relates to an improved display screen for a vision tester apparatus for use in optometric examinations to simulate the actual alphanumeric and graphical images of a modern, high-resolution video display terminal (VDT) and to facilitate prescribing corrective lenses that will perform well for a patient using an actual VDT. The display screen uses graphical images and alphanumeric characters of a continuous-line style to simulate more accurately the display on an modern, high-resolution VDT.

Abstract: A system for color characterization of an self-illuminating imaging display device and synchronization of the appearance of color images displayed on a self-illuminating imaging device is disclosed which is configured to embed a color characterization program in a response to an initial browser based request for a color image to facilitate the color characterization of a self-illuminating imaging device associated with the browser, forward the embedded response to a web browser, and generate a profile characterizing the self-illuminating imaging device using the color characterization program.

Abstract: One embodiment of the present invention is a visual field tester that includes: (a) a high intensity light source; (b) an optical fiber; (c) scanning optics, wherein light output from the light source is directed by the optical fiber to impinge upon the scanning optics, and the scanning optics directs the light to form a stimulus at various field positions; and (d) a video display system to output one or more light patterns. Another embodiment of the present invention is a visual field tester that includes: (a) a video display system to output one or more types of light patterns; (b) a background illumination display system; and (c) viewing optics to magnify the field of view of the video display system and the background illumination display system.

Abstract: The invention is directed to a viewing arrangement (1) having a viewing optic (3) for viewing an object (5) along a viewing beam path. The viewing arrangement (1) also has an illuminating apparatus (9) for illuminating the object (5) along an illuminating beam path running segment-wise transversely to the viewing beam path. A beam-shaping illuminating element (15) is mounted in the segment of the illuminating beam path running transversely to the viewing beam path. The illuminating element (15) is asymmetrical relative to the illuminating beam path.

Abstract: Device and method that allows an objective measure to be taken of the size and morphological pattern of the degradation of the image in scotopic vision. It consists of a black front screen (1) which has a central luminous source (2) surrounded by a grid of circular light spots (3) which at the beginning of the test light up sequentially or at random, according to the method selected, from the nearest to the central source of glare in a centrifuge fashion to the outermost, and a trigger which the patient will press every time he can discriminate the presence of each of the spots in 12 meridians. The non-discriminated or hidden spots will border an area which is interpreted as being occupied by the light aberration and is used as a basis for calculating the glare index.

Abstract: A device for use in laser ophthalmic surgery includes a laser system, a disposable contact lens and an adjustable retainer ring for mounting the contact lens on the laser system. In order to properly align the disposable contact lens to the laser system, reference marks on the contact lens are brought into coincidence with predetermined focal points along the laser beam paths. To this end, the laser system successively directs a laser beam along at least three predetermined paths to respective predetermined focal points, and the contact lens is positioned across these predetermined paths. Along each predetermined path, the laser beam is activated to establish a series of laser marks on the contact lens. If the laser marks, predetermined focal points and reference marks are all coincident, then the contact lens is properly aligned with the laser system.

Abstract: A computer program for an eye depth perception test method comprises a personal data entry form for recording statistical information of a subject to be tested in a personal data step of the program where the statistical information keyed is to a specific personal identification number. The computer program further comprises an algorithm to draw a cubic space upon a display screen in a display step, the algorithm drawing a first image at a first random location within the cubic space and a second image at a second random location within the cubic space in an image selection step, the program then permitting the subject to be tested for depth perception to move the first image and the second image toward convergence in the center of the cubic space.

Abstract: A visual acuity examination apparatus for examining a visual acuity of an examinee by presenting an optotype to the examinee includes an optotype presenting unit which selectively presents at least one of a plurality of comparison optotypes expressed in geometrical series, the optotypes being provided to be plural in number for each visual acuity value, an input unit with which a distinction answer of the examinee with respect to the presented optotype is input, a storage unit in which an examination program which sequentially determines an optotype to be next presented based on whether the distinction answer with respect to the presented optotype is right or wrong is stored, a control unit which controls the optotype presenting unit in accordance with the examination program, and a processing unit which determines a visual acuity value of the examinee from a percentage of right answers in the distinction answers with respect to an optotype for a visual acuity value.

Abstract: An optometric chart presenting apparatus which has a casing provided with a pair of test windows for right eye and for left eye for presenting an optotype optically placed at a predetermined distance to an eye to be examined through at least one of the test windows within the casing, the apparatus comprising a rotating optometric chart disk having a set of optotypes for right eye and a set of optotypes for left eye on one surface thereof, a restricting device disposed on a side of the eye relative to the optotypes for restricting a visual field of the eye, and a driving device for activating rotation of the rotating optometric chart disk in order to move an intended optotype into the visual field.

Abstract: A method of determining an eyeglass prescription for correcting a user's vision is provided. The method includes: prompting the user for selective parameters; configuring an eye chart for display based on the selective parameters; receiving sizing input from the user if the user increases or decreases the size of the eye chart until the eye chart appears clear; reconfiguring the eye chart based on the received sizing input; comparing the reconfigured eye chart to the configured eye chart; and determining the eyeglass prescription for correcting the user's vision based on a comparison between the reconfigured eye chart and the configured eye chart. A system for determining an eyeglass prescription for correcting a user's vision is also provided. The system includes a parameter module, a configure module, a receive module, a reconfigure module, a compare module, and a determine module. The parameter module prompts the user for selective parameters.

Abstract: A method and device for producing multicolored patterns can test the color vision or the reaction of a viewer. The patterns are produced by at least one switchable light source and at least two differently colored transparent color segments, which are alternately moved into the beam path of the light source. The device is a technically simple and inexpensive method to create multicolored patterns. In this manner, the light source or the light sources shine through each color segment of the color screen at a time interval predetermined by a control so that individual colors are produced. The time intervals of the individual colors follow one another so quickly that a color-merging frequency is reached or exceeded, and the individual colors of each individual light source merge into a mixed color.

Abstract: An electronic eye depth testing method comprises a three dimensional cubic space displayed on a display screen, wherein the cubic space has a first image of a three dimensional object and a second image of a three dimensional object randomly placed within the cubic space. The first image is located at the intersection of two perpendicular horizontal planes and a vertical plane perpendicular to said two horizontal planes and the second image is located at the intersection of two perpendicular horizontal planes and a vertical plane perpendicular to said two horizontal planes. A subject to be tested for depth perception is directed to move the images into convergence in the center of the cubic space.

Abstract: A vision tester comprises a slide projector for projecting a visual indication chart onto a curved display screen via a mirror rotated by a motor. The center of curvature of the curved display screen substantially coincides with the subject's eye. The rotation of the mirror causes an image of the visual indicator to be moved across the screen in a specific direction. When the subject provides a response to the moving image, the speed of image movement at the time of the response is detected and stored in a memory. The average of a plurality of such measurements is used to determine the subject's dynamic visual acuity.

Abstract: The invention relates to a method of spectral or colorimetric characterisation of a self-illuminatng imaging system, in which the imaging system produces a color field which is matched visually with a reference color field, wherein a transparent color filter film with known spectral or colorimetric reference values which covers a reference color area of the imaging system is used as a reference color field. The invention also provides for the use of the method of spectral or colorimetric characterisation of a self-illuminating imaging system for calibration of the imaging system.

Abstract: A process for testing vision sensitivity from a target is set forth. Specifically, I illuminate the vision sensitivity chart with only indirect light and in the total absence of direct light. In the preferred embodiment, the contrast sensitivity chart is placed in an enclosure and provided with only indirect illumination of a desired intensity. The indirect illumination is such that all light illuminating the vision sensitivity target first indirectly rebounds from a surface and only then is incident upon the vision sensitivity target. At the same time, light rays on the target from this illumination cannot directly rebound into the direct viewer of the subject being tested. With an enclosure having this characteristic, paired viewing apertures are provided and spaced from the eye to provide the eye with a clear the contrast sensitivity chart. Offset from the eye and at a solid angle emulating a real life night driving light source, such as a headlight, light having a direct glare is introduced to the eye.

Abstract: Ophthalmic device, such as a slit lamp or a visual acuity testing device or a combination of these devices, for variable illumination of the patient's eye with illumination fields of different geometries, wherein the illumination of the patient's eye is generated by means of chip components which are controllable electronically with respect to their light transparency, light reflection or light emission and which are illuminated by reflected light or transmitted light or are self-illuminating.

Abstract: A method for presenting two simultaneous images having respective cross-sectional areas A.sub.1 and A.sub.2, on respective first and second 2-dimensional image arrays so as to be seen by an observer as a dichoptic stimulus of substantially equal intensity, involves the steps of generating a first one of the images at a predetermined first intensity on the first image array so as be perceived by a first eye of the observer only, and generating a second one of the images at a predetermined second intensity equal the first intensity multiplied by ##EQU1## on the first image array so as to be perceived by a second eye of the observer only. An apparatus for carrying out the method includes a pair of LCD image arrays and a pair of spectacles having prismatic elements for allowing objects to be viewed in a desired direction only.

Abstract: An apparatus and method for communicating to a deaf or severely hearing impaired individual while vision testing utilizing indicator lights (52A), (52B), (52C), and (52D) positioned in the same plane as a visual acuity test chart (54) having optotypes (50B). The examiner activates the indicator lights by means such as an infra-red remote control receiver (56). This is done in a manner previously disclosed to the examinee permitting the examinee to understand messages from the examiner, while the examiner simultaneously operates a refractor to determine the refractive state of the examinee.

Abstract: A remote-controlled LCD sight-testing instrument which includes a mainframe and a remote controller, the mainframe having a display module, the display module being controlled by a control switch of the remote controller to show different test patterns for testing the user's visual acuity, the remote controller having a plurality of direction buttons through which the user gives an answer to every test pattern shown on the display module, the mainframe further having a visual acuity display unit controlled to indicate the user's visual acuity by digital and alphabet, and a buzzer controlled to give a particular sound after test of every test pattern subject to the test result.

Abstract: In an apparatus for displaying a visual acuity chart table, in response to the change of the distance between an eye to be examined and an apparatus body, a concave mirror of a visual chart optical system is moved along a desired optical axis direction and a concave lens is inserted in the optical path of the visual chart optical system, so that the forming magnification of the visual chart images of various kinds of visual charts is kept constant. Thus, irrespective of the distance between the eye to be examined of a person to be examined and the apparatus body, the visual chart images of the visual charts having a constant size can be displayed to the eye E to be examined at a constant distance, and an accurate eye examination to the eye to be examined is carried out irrespective of the dimensions of an eye examination space.

Abstract: An optical apparatus includes a pupil illuminator for illuminating the pupil of an eye of an individual, an imager for obtaining an image of the pupil and an image of the cornea of the eye, a presentor for preliminarily presenting an image positioned at a particular point to the eye, and a direction-of-line-of-sight calculator for calculating the direction of the line of sight of the eye using the positional relationship between the image of the pupil and the image of the cornea on an imaging surface of the imager, and calculating the direction of the line of sight using parameters relating to the image of the pupil and the image of the cornea. The values of the parameters are obtained from the positional relationship between the image of the pupil and the image of the cornea on the imaging surface of the imager when the eye views the image at the particular point.

Abstract: A quantitative visual test measures the rate at which an individual is able to complete a defined visual task, either on paper or on a self illuminated screen. The task involves comparing a plurality of similar appearing numbers to determine if they are an exact match within predetermined levels of time. Inability to complete the test within the predetermined level of time indicates the likelihood that the individual will exhibit visual stress and dyslexia. Individuals under such stress are then remediated by the use of adjusted lighting environments sometimes including other visual aids.

Abstract: An ophthalmic refractor is constructed to judge whether a visual acuity value of a symbol with a mask is minimum or maximum among values in a selected charts, select a chart containing a symbol indicating a visual acuity value smaller than the minimum visual acuity value when the visual acuity value is judged to be minimum, and select a chart containing a symbol indicating a visual acuity value larger than the maximum visual acuity value when the visual acuity value is judged to be maximum.

Abstract: A vision tester comprising a front wall and a back wall. Printed matter comprising words appears on the back wall, which is approximately 14 inches (35.6 cm.) from the front wall. The printed matter is exposed to ambient light from the top and front. The front wall has an opening through which the user of the vision tester looks. A plurality of magnifying lenses, of different diopter ratings, are selectively positionable behind the opening. Indicia appear to indicate the diopter rating of each lens. The user of the vision tester can determine the diopter rating of the appropriate lens needed for reading by determining which lens renders the printed matter clear and readable.

Abstract: An improved ophthalmological self test unit for assisting in the self evaluation of the degenerative effects of certain eye disorders. The self diagnostic ophthalmological device includes a first layer having a top rewriteable surface and a grid pattern disposed thereon and a magnetic second layer fixedly attached to the first layer for attaching the self test device to a magnetically permeable surface.