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METHOD AND APPARATUS FOR MEASURING

MAGNIFICATION POWER OF A MAGNIFYING AID

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to measuring the magnification power of magnifying aids and more particularly to an apparatus and method for determining unknown magnification powers of magnification, aids.

2. Description of Related Art

Presently in the magnifier industry there does not exist a standard definition of magnifying power nor a standard method for measuring the magnification power of magnifyi ng aids , such as lenses . Generally, magnifiers are marked or labeled with predetermined or designated magnification powers, however, these listed magnification powers are generally incorrect. Certain industries, such as the soldering industry, require that specific magnification powers be used when inspecting connections or components. Generally, magnifiers that are used out in the field cannot easily be field checked to determine, if indeed the magnification power listed on the magnifier is the true magnification power of the magnifier. Thus, in many industries maqnifiers having improper magnification power are used for inspection. This results in improper inspection of the components which ultimately affects the quality and reliability of the components.

Presently, devices for measuring the magnification powers of magnifying aids have been limited to expensive special testing equipment which is generally found only in an optical laboratory. This testing equipment is highly complex, expensive, nonportable and requires an optical technician to test for the magnif ication power of the magnifier. The user of a magnifying aid who desires to determine its magnification power must send the magnifying aid to an optical laboratory to have the magnification power determined. This process is very time consuming, expensive, and expends valuable time when the user is not able to utilize the magnifying aid.

SUMMARY OF THE INVENTION

Accordingly, the present invention overcomes the disadvantages of the heretofore used devices and methods by providing a new and improved apparatus for measuring the magnification power of a magnifying aid out in the field. The present invention is portable, inexpensive, and capable of being used by non-optically trained operators. The present invention also enables magnifying aids to be field checked without any optical laboratory facility requirement. Thus, the present invention enables unknown magnification powers of magnifying aids to be determined quickly and accurately out in the field.

The apparatus includes an optical system having an objective lens which is apertured down to the size of the pupil of a human eye. A reticle is located at the rear focal plane of the objective lens. The apparatus also includes an eyepiece which is focussable on the reticle which is also positioned in the line of sight of the eye-piece. The reticle may be calibrated to determine the magnification power of a magnifying aid when a measuring scale of known size is viewed through the combination of the optical system and the magnifying aid. The optical system is calibrated such that a predetermined angle is associated with each unit mark of the reticle. The reticle unit mark, having a

predetermined angle, is superposed upon the image of the measuring scale, which has unit marks corresonding to predetermined angles, such that the predetermined reticle angles and measuring scale angles may be

ratioed to calibrate the magnification power of the magnifying aid. If the reticle mark spacing and measuring scale spacing are chosen correctly, the magnification power may be read directly off the reticle.

Also disclosed is a method of measuring the

magnification power of a magnifying aid which uses the above described optical system. The method includes:

providing a magnifying aid which is to have its magnifying power measured; positioning the magnifying aid in the viewing line of the optical system; viewing and focusing a presized scale through the optical system and magnifying aid; comparing the calibrated reticle unit marks with the presized scale units marks; and determining the magnification power of the magnifying aid.

From the subsequent description and the appended claims taken in conjunction with the accompanying

drawings, other objects and advantages of the present invention will become apparent to one skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

in the accompanying drawings:

FIG. 1 is a side elevational view of an apparatus in accordance with the present invention.

FIG. la shows a front view of the aperture disc illustrating the preferred placement of the aperture.

FIG. 2 is a schematic view illustrating calibration of the apparatus in accordance with the present invention,

FIG. 3 is a plan view as seen through the apparatus of FIG. 1.

FIG. 4 is a schematic view illustrating calibration of an apparatus in accordance with the present invention.

FIG. 5 shows a portion of a calibrated reticle having precalibrated magnifying powers indicated

thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, an apparatus for measuring the magnification power of a magnifying aid is shown and designated with the reference numeral 10. The

apparatus 10 generally includes an optical system (12) and a measuring (or target) scale (16) of known size.

The optical system (12) generaly. includes an

eyepiece (18) having a reticle (20) positioned in the eyepiece (18). The objective lens (34) is focused at infinity on the reticle (20) and any such optical system which can be focused at infinity may be utilized in the apparatus of the present invention; preferably a telescope or monocular focused at infinity is used. A telescope which works satisfactorily in the present invention is a No. 14 Walters 8 x 30 Monocular with

Grid, distributed by S. Walters, Inc., 32208 Oak Shores Drive, West Lake Village, California. The eyepiece

(18) is focused onto the reticle (20) so that the

reticle is in sharp focus to the user when viewed

through the optical system (12). Generally, an aperture disc (32), having a small aperture (33) for simulating the pupil of the eye, is positioned adjacent to the objective lens (34) of the optical system (12). The aperture disc acts as an aperture stop for limiting the amount of light entering the objective lens to that amount which would enter the pupil of the eye of a user. When using the optical system (12) to measure the magnifying power of a magnifying aid (14) the magnifying aid is positioned adjacent the objective lens (34) of the optical system, and the target scale (16) is placed at the focal point of the combination of the optical system (12) and magnifying aid (14) (i.e., at "infinity").

Magnification power may be defined as the ratio of the tangent of two half-angles subtended by an object under two different conditions. The first half-angle (a reference angle) is the half-angle subtended by the object as viewed by the human eye at a distance of 10 inches from the object. The ten inches is used to provide a standard of reference and is an appropriate distance since it is generally accepted that 10 inches is statistically the closest distance at which the human eye can focus. The second half-angle is the apparent half-angle subtended by the object when viewed by the human eye through the optical aid. If the magnifying aid has a power greater than unity, the second half-angle will be greater than the first, and the magnifying power of the aid can be calculated as the ratio of the tangent of the second half-angle divided by the tangent of the first half-angle. However, if this method is to produce repeatable results with acceptable accuracy, a calibrated optical system must be utilized to accurately measure the two half-angles. The optical system (12) is intended to provide that capability.

CALIBRATION OF THE RETICLE UNIT MARKS OF THE OPTICAL SYSTEM Generally, the optical system (12} is calibrated such that each of the unit marks (22) on reticle (20) corresponds with a known predetermined half-angle. Turning to FIG. 2, the optical system (12) is shown positioned at a predetermined distance (42), which is equivalent to infinity for the optical system (12) being used, from a measurement device (24), such as a precision

scale. The center mark (21) of the reticle (20) is

positioned such that one end (preferably the bottom

end) of the measurement device (24) is aligned

with the center mark (21) of the reticle (20). This determines a starting point for calculating the half-angles corresponding to each unit mark (22) of the

reticle (20). The reticle (20) is calibrated by measuring the distance (40) subtended from a chosen unit

mark (25) to the center mark (21) of the reticle (20).

This distance (40) between the chosen unit mark (25) and center mark (21) is used to calibrate the tangent of the half-angle corresponding to the chosen unit

mark (25) on the reticle (20) as viewed through the optical system (12). The tangent of the half-angle for the chosen unit mark (25) on the reticle (20), is determined by taking the distance (40) measured on

measurement device (24) and corresponding to the distance on the reticle from the center mark (21) of the reticle (20), to the chosen unit mark (25) on the

reticle (20), and dividing that distance (40) by the distance (42) from the optical system (12) to the

measuring member (24), which should be equal to at

least 500 times the focal length of the optical system objective (34). Such a distance is equivalent to

"infinity" for the optical system (12) being used.

Each unit mark (22), of the reticle (20), is similarly calibrated to determine its corresponding half-angle.

Now, the tangent of the reticle marks, referred to hereinafter as tan β, may be utilized in the determination of the magnification power of a magnifying aid.

MEASURING MAGNIFYING POWER OF AN OPTICAL AID

The calibrated optical system (12) is generally positioned as shown in FIG. 1 with the aperture (33) placed in the same location as the user's eye would be when using the magnifying aid (14). The target scale (16) of known size is positioned in the line of sight of the optical system (12) and magnifying aid (14).

The target scale (16) has a plurality of equally spaced unit marks (30). The optical system (12) and magnifying aid (14) are moved together in and out along the optical line of sight until the target scale (16) comes into focus. (FIG. 3.) Once the target scale (16) is in

focus the angle subtended by the target scale (16) (or any of its unit marks) on the reticle (20) may be

determined. The center mark (21), of the reticle

(20), is aligned at the starting edge (29) of the

target scale (16). A measurement is taken from the starting edge (29) of the scale (16), to a chosen unit mark ( 31 ) on the target scale ( 16 ) , which corresponds to a chosen unit mark (25), having a previously calibrated angle, on the reticle (20) pattern. Once the length of the distance (44) on the target scale (16) has been determined, the tangent for the angle subtended by

the magnifying aid (14) may be determined. The tangent of the second half-angle for the chosen unit mark (25) on the reticle (20), hereinafter referred to as Tan α, is determined by dividing the distance (44) measured on the target scale (16), in inches, by ten (10) inches.

The ten (10) inch length corresponds to the normal closest focusing distance of the human eye. Now, Tan α may be utilized in the determination of the magnification

power of magnifying aid (14).

The magnification power of the magnifying aid

(14) is determined by dividing the Tan β by Tan α, both of which are calculated as described. Magnification power can be determined as follows:

MP = TAN β

TAN α

Distance (40) as measured on measuring member

(24) corresponding to the distance from

chosen reticle mark (25) to center

Tan β = reticle mark (21)

distance (42) from optical system (12) to

measuring member (24)

Distance (44) measured on the target scale (16) corresponding to the distance from the

chosen unit mark (31) (which corresponds

to the chosen mark (25) on the reticle (20) Tan α = used in Tan β above) to the starting edge (29) of the target scale .

wherein the distance measurements are in inches. Also, since the size of the target scale (16) is known, magnification powers (23) may be directly positioned onto a calibrated reticle (20) as illustrated in FIG 5. This is accomplished by substituting known magnification powers (e.g. 1, 2, 3, 4, 5 etc.) and solving for the unit reticle size and positioning the known magnification powers on the reticle at desired unit marks (22). Therefore, the magnification power can be directly positioned (printed) onto the reticle (20) of the optical system (12) and magnification power may be determined by

viewing a predetermined size target scale through the optical system (12) and magnifying aid (14).

To illustrate the simplicity and ease of use of such a reticle with precalibrated magnification powers indicated on reticle, consider the following. The

magnifying aid of unknown power is positioned with

respect to the aperture of the optical system in the same position as would be the eye of a user of the

magnifying aid. The combination of the optical system and magnifying aid are moved back and forth along the optical axis until the precision measuring target scale is brought into focus. A preselected length of said

precision target scale is measured against the divisions (unit marks) of the reticle. If the selected length of the precision scale extends from the center of the reticle to the unit mark on the reticle marked with a

5, then the magnifying power of the magnifying aid is

5. This procedure is particularly easy to use and

only requires that the selected length on the measuring target scale as viewed through the combination of the optical system and magnifying aid be the same length as would be seen through the optical system alone as extending from the center of the reticle to the unit mark indicating unity power. Thus, a non-optically trained operator can determine unknown magnification power of a magnifying aid by viewing a predetermined sized target scale (16) through the combination of the apparatus

(10) and magnifying aid (14) of unknown magnifying power and reading the power off the precalibrated reticle.

Calibration Example

The following is an example for calibrating an apparatus in accordance with the present invention. The example is included for illustration purposes only and is not intended to be viewed as limiting the scope of the present invention. Corresponding elements are

designated with corresponding reference numerals which have been primed.

An 8 x 30 monocular having a usable target reticle already focused at infinity was chosen as the

optical system (12') (See FIG. 4). An aperture disc (32') having a four to five millimeter diameter aperture was placed in front of the telescope's objective lens (34') for simulating the observer's eye pupil size when

measuring magnifying aids. This aperture also reduces parallax error when calibrating the optical system. A precision scale (24') was positioned 6,000 inches away from the objective lens (34') of the telescope, as

shown in FIG. 4. An object distance (40') is taken.

The object distance (40') corresponds to a length on

the precision scale (24') equal to the distance from

the center mark. (21') of the reticle (20') to the

desired chosen mark (25') on the reticle. Tan β, is

found by taking the object distance (40') and dividing by the distance (42') front the telescope (12') to the precision scale (24'). In this case, the object distance (40') equaled 75 inches. Tan β was found by dividing the object distance (40'), 75 inches, by the distance

(42') between the telescope and precision scale, which is 6,000 inches. Tangent beta is equal to 0.0125;

which is 75 divided by 6,000. The optical system

(12') is now calibrated and ready for use in determining the unknown magnification powers of magnifying aids.

The optical system (12) is positioned so that its aperture (33) is placed where the eye of the user would have been when using the magnifying aid (14) to be calibrated as seen in FIG. 1. A target scale (16) is positioned at the focal point of the apparatus (10). The target scale (16) used was a 0.1 inch linear scale reticle with

100 divisions of 0.001 inch increments. Such a target scale may be obtained from a number of commercial suppliers.

The scale (16') is viewed through the optical system (12) and magnifying aid (14) (See FIG. 3). The target scale distance (44) between the center mark (21) of the reticle (20) and the chosen mark (25) of the reticle (20) is determined. This target scale distance (44) measured for the particular magnifying aid (14) was equal to 0.0125 inch. Tangent alpha is determined by dividing the target scale distance (44) by ten (10) inches. Thus, tangent alpha is equal to 0.00125. Now that tangent alpha and tangent beta are known, the

magnification power may be calculated. Magnification power (MP) is equal to tangent beta divided by tangent alpha. Thus, for this case the magnification power is equal to 0.0125, (which is 75 divided by 6,000), divided by 0.00125 (which is 0.0125 divided by 10). Therefore, magnification power can be determined for this particular magnifying aid (14) by dividing 0.0125 by 0.00125

which gives a magnification power of 10 for the magnifying aid (14). By using a target scale of known size the magnifying power can be read directly off the reticle (20) as any value of magnifying power per division

(22) on the reticle that subtends the calibrated distance (44) on the target scale (16).

While the above summarizes the present invention, it will become apparent to those skilled in the art that modifications, variations, and alterations may be made without deviating from the scope and fair meaning of the present invention as described in the subjoined claims.

INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)

(51) International Patent Classification 4 (11) International Publication Number: WO 88/ 03 G01M 11/02 A3 (43) International Publication Date: 19 May 1988 (19.05.

(21) International Application Number : PCT/US87/02451 (81) Designated States: CH (European patent), DE (E

pean patent), GB (European patent), IT (Europ

(22) International Filing Date: 28 September 1987 (28.09.87) patent), JP.

Published

(31) Priority Application Number : 929,022 With international search report.

Before the expiration of the time limit for amending t

(32) Priority Date: 10 November 1986 (10.11.86) claims and to be republished in the event of the receipt

amendments.

(33) Priority Country: US

(88) Date of publication of the international search report:

(71) Applicant: HUGHES AIRCRAFT COMPANY [US/ 16 June 1988 (16.06.

US]; 7200 Hughes Terrace, Los Angeles, CA

90045-0066 (US).

(72) Inventor: STRITTMATTER, Donald, J. ; 4110 E. La

Paloma Drive, Tucson, AZ 85718 (US).

(74) Agents: BROWN, Charles, D. et al.; Hughes Aircraft

Company, Post Office Box 45066, Bldg. Cl, MS A126,

Los Angeles, CA 90045-0066 (US).

(54) Title: METHOD AND APPARATUS FOR MEASURING MAGNIFICATION POWER OF A MAGNIFYI AID

(57) Abstract

An apparatus (10) for measuring the magnification power of a magnifying aid (14). The apparatus (10) includes optical system (12) having an objective lens (34) focused at infinity on a reticle. The reticle (20) is positioned in the line sight of the optical system (12). The reticle (20) is precalibrated such that the magnification power of a magnifying aid (1 may be determined. Also, disclosed is a method of calibrating the optical system (12) and a method of measuring the ma nification power of a magnifying aid (14).

FOR THE PURPOSES OFINFORMAHON ONLY

Codes used to identify States party to the PCT on the front ages of amphletspublishing international applications under the PCT.

AT Austria ER France ML Mali

AU Australia GA Gabon MR Mauritania

BB Barbados GB United Kingdom MW Malawi

BE Belgium HU Hungary NL Netherlands

BG Bulgaria IT Italy NO Norway

BJ Benin JP Japan RO Romania

BR Brazil KP Democratic People's Republic SD Sudan

CF Central African Republic ofKorea SE Sweden

CG Congo KR Republic ofKorea SN Senegal

CH Switzerland LI Liechtenstein SU Soviet Union

CM Cameroon LK Sri Lanka TD Chad

DE Germany, Federal Republic of Lϋ Luxembourg TG Togo

DK Denmark MC Monaco US United States of America

BI Finland MG Madagascar