ISO 10938 pdf download.Ophthalmic instruments — Chart projectors
1 Scope
This International Standard, together with ISO 15004, specifies minimum requirements and test methods for chart projector systems, including an optical projector and a screen, for the projection of targets used for the determination of visual acuity, the refractive status and the binocular functions of the human eye. This International Standard takes precedence over ISO 15004, if differences exist.
2 Normative references
The following standards contain provision which, through reference in this text, constitute provision of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encourage to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 8596:1994 Ophthalmic optics – Visual acuity testing – Standard optotype and its presentation ISO 8597:1994 Optics and optical instruments – Visual acuity testing – Method of correlating optotypes ISO 15004:1997 Ophthalmic instruments – Fundamental requirements and test methods IEC 60601-1:1988 Medical electrical equipment – Part 1: General requirements for safety
3 Requirements
3.1 General The chart projector shall conform to the requirements specified in ISO 15004. 3.2 Functional requirements The chart projector shall conform to the requirements specified in 3.2.1 to 3.2.5. NOTE – Verification of these requirements is described in clause 4. 3.2.1 Optotypes If designed to be used for certification purposes, the chart projector shall be equipped either with the standard optotype according to ISO 8596 in the grades specified therein, or with optotypes which are correlated to the standard optotype by the method described in ISO 8597.3.2.2 Test area and positioning of optotypes If designed to be used for certification purposes, the target of the chart projector system shall comply with the requirements of clause 5 and 6.1 of ISO 8596:1994. NOTE – It is recommended that there be at least 5 presentations (see 6.2 of ISO 8596:1994) of each optotype size. 3.2.3 Resolving power When tested as described in 4.2, the chart projector shall conform to the following requirements: The minimum resolution on the screen (expressed in lines per millimetre) shall be 4/ V times the line separation corresponding to the limb width on the smallest optotype which the system is designed to project, where V is the decimal acuity grade of the smallest optotype (see ISO 8596). 3.2.4 Luminance and contrast When tested as described in 4.2, the chart projector shall conform to the following requirements: The luminance and contrast of the projected chart shall comply with ISO 8596. The luminance of the background surrounding the optotype shall be between 80 cd/m 2 and 320 cd/m 2 . NOTE – The recommended luminance is 200 cd/m 2 . The luminance of the background within 2 character diameters of the optotype shall not vary by more than 30 %. Across the entire area of the projected field it shall not vary by more than 50 %. Screens which are suitable for use with the projector shall be specified by the manufacturer. 3.2.5 Projection range The projection range shall be 2,9 m to 6,1 m.
4 Test methods
4.1 General All tests described in this International Standard are type tests. Measuring devices shall have an accuracy better than 10 % of the smallest value to be determined. 4.2 Resolving power The smallest projected optotype shall be observed at 1 / 3 of the designed viewing distance and shall not differ noticeably in contrast and contour from larger optotypes. The observer shall have a decimal visual acuity at least equal to 1,0.
5 Accompanying documents
The chart projector shall be accompanied by documents containing instructions for use. In particular, this information shall contain: a) name and address of the manufacturer; b) specification of projection screen;c) if appropriate, a statement that the chart projector contains standard optotypes in accordance with ISO 8596 and/or correlated optotypes in accordance with ISO 8597; d) where appropriate, a statement that the chart projector in its original packaging conforms to the transport conditions as specified in 5.3 of ISO 15004:1997; e) any additional documents as specified in 6.8 of IEC 60601-1:1988.