GB2215077A - Apparatus for testing visual inspection equipment - Google Patents

Abstract

A device 30 for use in testing visual inspection equipment, particularly endoscopes, is assembled from a flat piece of card or plastics into a half-box configuration with a plurality of holes down its upright side 11 through which an endoscope may be inserted which is then suitably positioned relative to a test pattern printed on the device at 12. The optical quality of the endoscope can thus be assessed. The device is collapsible into a flat shape that can be issued with each endoscope. <IMAGE>

Description

APPARATUS FOR TESTING VISUAL INSPECTION EQUIPMENT This invention relates to apparatus for testing visual inspection equipment of the type known in the art as visual aids (VA).

Examples of visual aids in the mechancial field are endoscopes, which are rigid optical equipment and fibrescopes, which are flexible optical equipment. VA equipments are used extensively throughout the aerospace and engineering industries. In particular, they are used for the internal examination for damage in aircraft components and structure and for the routine examination of aircraft engines.

Inspections which utilize the VA equipments are introduced to detect cracks and damages which could, if undetected, affect the integrity of the component and structure under examination and therefore the airworthiness of the aircraft. It is, therefore, very important that all VA equipment be maintained to a very high standard so that the user has the best possible chance of detecting any faults. It will also be realised that similar types of optical equipments are used extensively thro,ughout the medical profession for internal examination of patients.

Apparatus for testing the quality of visual aids have in the past utilized some kind of optical test bench incorporating mechanical fixtures and jigs and an illuminated optical test card. Electronic equipment has been used to obtain the desired results.

These apparatus have disadvantages in that they are large and heavy and require complicated electronics. They are obviously not convenient for use 'on site' by, say, an aircraft engineer, just prior to use of the equipment.

There is, therefore, a need for testing apparatus for visual aids which is portable, easy to use and small enough to be issued with each visual aid when purchased. This would enable 'on site' inspection wherever the equipment was taken.

According to the present invention there is provided a device for testing visual aids wherein the device is of half-box configuration, having a base and an upright substantially at right angles to each othertincluding a test pattern and a plurality of holes selectively situated to allow a standardised visual aid to be inserted into an appropriate hole, and suitably positioned relative to the test pattern for testing.

The device is assembled from a flat piece of material, preferably cardboard, which is pre-printed with the test pattern along with instructions for use and visual symptoms of optical damage.

Thus the device is a complete unit for testing visual aids which is portable, cheap to produce and can be collapsed inwardly as well as outwardly into a flat shape that can be issued with each visual aid, and stored in the specialist container provided for the visual aid.

According to a second aspect of the present invention there is provided a method for testing visual aids comprising the following steps: assembling from a flat piece of material a device having half box configuration, with a base and an upright substantially at right angles to each other, including a test pattern displayed on the inward facing surface of the base and a plurality of holes selectively situated down the upright of the device; inserting a standardised visual aid into an appropriate hole; positioning the visual aid to allow viewing of the test pattern; and viewing the test pattern; whereby the correct positioning of the visual aid may be confirmed and the optical quality of the visual aid may be judged.

The advantage of this method of testing visual vids is that it is just as simple to carry out as a subjective visual test but gives quantified results for the optical quality of the visual aid. Moreover, the simplicity of the method enables the user to carry out a quick check of the apparatus 'on site' prior to use.

Visual aids can therefore be graded by use of this method.

The present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Fig 1 is a plan view of the outward facing surface of the device as printed before assembly, Fig 2 is a plan view of the inward-facing surface of the device as printed before assembly, and Fig 3 is a perspective view of the assembled device For convenience the only type of visual aids herein described will be endoscopes.

An endoscope, in engineering parlance, is an arrangement of fibre optics and lenses contained within a tube of rigid plastics material.

A light source is provided to pass light through the fibre optics to illuminate the area to be viewed. The reflected light is transmitted back through the endoscope via a system of lenses.

A light collector and eyepiece arrangement allows an image of the area illuminated to be viewed. The probing end of the endoscope has mounted thereon either a flat piece of glass for 'forward viewing' or, more commonly, a prism to enable viewing at different angles.

Endoscopes are, therefore, classified into standards according to their angle of view.

A device for testing an endoscope (Fig 1) is formed from a cardboard pattern 10 having an upright 11, a base 12 and substantially triangular side members 13 to which are attached tabs 14 which are preferably self-adhesive. A plurality of holes 15 in the upright 11 are labelled according to the angle of view of the endoscope to be tested.

Information 16 printed on theunderside of the device assists the user to assess the type of optical damage, if any, to the endoscope.

As shown in Fig 2 a test pattern 17 is printed on the inward facing surface of the base 12 of the device and is preferably a United States Air Force 1951 resolving power target. This is surrounded by concentric circles 18.

Instructions 19 for use of the device are also provided.

Fold lines 20 are preferably scored to enable easy assembly of the device.

As shown in Fig 3 the device 30 takes on a half-box configuration when assembled with the upright 11 and base 12 substantially at right angles to each other.

In use, an endoscope is inserted into the appropriate one of the plurality of holes 15, according to its angle of view. The user then looks down the endoscope to view the test pattern.

The initial part of the test is to adjust the position of the endoscope until the concentric circles 18 are both clear and undistorted and are concentric in the image presented by the endoscope to the user. This position will always be approximately two inches above the test pattern 17 for all types of endoscopes. This is illustrated in Fig 1 by a diagram 21 also printed on the cardboard pattern 10, which shows the viewing positions for different types of endoscopes. Once this point has been achieved the user then views the test pattern 17 and selects the group of figures in the test pattern 17 having the closest spacing which he can discern through the endoscope. That is, he selects the group which is next to the group in which the rectangles are blurred together and no spacing is visible between them.

A new, unused endoscope should be capable of discerning all the groups of lines in both column A and column B. However, any endoscope will be fit for use if it satisfies the minimum requirement of being able to discern all groups in column A and at least group 1 in column B. If this minimum requirement is not met the endoscope is probably suffering from some kind of optical damage and will not produce reliable results when in use.

The method, therefore, provides an objective way of testing endoscopes.

Whennotin use, the device is inwardly collapsed into a flat shape along fold lines 22 and stored in the specialised container provided for the endoscope.

The invention has been described with reference only to endoscopes. However, it will be realised that the invention is not limited to endoscopes, but could be used for similar optical equipment such as fibrescopes and borescopes.

Claims (13)

1. A device for testing visual aids wherein the device is of half-box configuration having a base and an upright substantially at right angles to each other including a test pattern and a plurality of holes selectively situated to allow a standardised visual aid to be inserted into the appropriate hole and suitably positioned relative to the test pattern for testing.

2. A device according to Claim 1 wherein the test pattern is displayed on the inward facing surface of the base and the plurality of holes are situated down the upright of the box.

3. A device according to Claim 1 or Claim 2 wherein the device is assembled from a flat piece of material.

4. A device according to Claim 3 wherein the flat piece of material has displayed thereon instructions for use.

5. A device according to Claims 3 or Claim 4 wherein the flat piece of material has displayed thereon visual symptons of optical damage.

6. A device according to Claims 3 to 5 wherein the flat piece of material has displayed thereon fold lines to enable assembly of the device.

7. A device according to any previous claim wherein the device is inwardly collapsable to form a flat structure.

8. A device according to any previous claim in conjunction with a standardised visual aid.

9. A device according to any one of Claims 3 to 8 wherein the material is cardboard.

10. A device according to anyone of Claims 3 to 8 wherein the material is a plastics material.

11. A method of testing visual aids comprising the following steps: assembling from a flat piece of material a device having half-box configuration with a base and an upright substantially at right angles to each other including a test pattern displayed on the inward facing surface of the base and a plurality of holes selectively situated down the upright of the device; inserting a standardised visual aid into the appropriate hole; positioning the visual aid to allow viewing of the test pattern; and viewing the test pattern; whereby the correct positioning of the visual aid may be confirmed and the optical quality of the visual aid may be judged.

12. A visual aid graded by the method of Claim 11.

13. A device substantially as herein described with reference to the accompanying diagrams.