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YY/T 1603-2018: Medical endoscopes--Endoscope supply units--Video camera system
YY/T 1603-2018
YY
PHARMACEUTICAL INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 11.040.99
C 40
Medical Endoscopes - Endoscope Supply Units -
Video Camera System
ISSUED ON: JANUARY 19, 2018
IMPLEMENTED ON: JANUARY 01, 2019
Issued by: China Food and Drug Administration
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 requirements ... 6
5 Test Methods ... 7
Appendix A (Normative) Test Methods of Brightness Response Characteristic 9
Appendix B (Normative) Test Methods of Signal-to-Noise Ratio ... 14
Appendix C (Normative) Test Methods of Spatial Frequency Response ... 18
Appendix D (Normative) Test Methods of Static Image Latitude ... 24
Medical Endoscopes - Endoscope Supply Units -
Video Camera System
1 Scope
This Standard specifies the terms, definitions, requirements, and test methods for
medical endoscopic camera system.
This Standard is applicable to medical endoscopic camera system (hereinafter referred
to as camera system) that are used as endoscope supply units in endoscopy and
surgery.
This Standard is not applicable to the camera system with special spectral effects and
non-visible spectral imaging.
2 Normative References
The following documents are essential to the application of this document. For the
dated documents, only the versions with the dates indicated are applicable to this
document; for the undated documents, only the latest version (including all the
amendments) are applicable to this document.
GB 9706.19 Medical Electrical Equipment - Part 2: Particular Requirements for the
Safety of Endoscopic Equipment
3 Terms and Definitions
For the purpose of this document, the following terms and definitions apply.
3.1 Conversion function
3.1.1 Opto-electronic conversion function; OECF
The ideal relationship between the object brightness and the corresponding output
signal of the camera system.
3.1.2 Electro-optical conversion function
The inverse function of OECF.
AND the ratio of the modulation degree of the output signal calculated by the OECF
inverse function to the modulation degree of the target object surface brightness.
3.7 Sine-based spatial frequency response; s-SFR
SFR when the target is a sine wave modulation diagram.
3.8 Modulation degree
The ratio BETWEEN the maximum signal value minus the minimum signal value AND
the maximum signal value plus the minimum signal value.
3.9 Spectral neutrality
The reflection or transmission characteristics that is maintained constant against a
certain wavelength of light.
4 requirements
4.1 Requirements for detachable lens
4.1.1 Modulation transfer function (MTF)
The manufacturer shall give the nominal value of the spatial frequency corresponding
to the MTF value of the detachable lens at 50% in the attached information, the
tolerance is -20%, and the upper limit is not counted.
4.1.2 Focal length
The manufacturer shall provide the focal length parameters of the detachable lens in
the attached information. For the lens with a fixed focal length, the tolerance for
nominal value of the focal length is ±20%. For the lens with variable magnification, the
tolerance for nominal value of the minimum focal length is +20%, and the lower limit is
not counted; the tolerance for nominal value of the maximum focal length is -20%, and
the upper limit is not counted.
4.2 Brightness response characteristics
The manufacturer shall provide the output brightness electro-optical conversion
function or data list of the adapted monitor expressed in relative value in the technical
data. The sampling points of the data list are no less than 10, and cover the entire
latitude area.
The output signal of the camera system shall maintain a good linearity between the
brightness calculated according to the electro-optical characteristics and the
brightness of each gray scale of the actual tested target board; and the linear fitting
5.1.1 Modulation transfer function (MTF)
Place a Φ10mm aperture in the measuring optical path, then measure by a general-
purpose device with sufficient accuracy.
5.1.2 Focal length
Place a Φ10mm aperture in the measuring optical path, then measure by a focal length
meter with sufficient accuracy.
5.2 Test methods of brightness response characteristic
Check the content of the technical data provided by the manufacturer.
Measure the brightness response characteristics of the camera system according to
the methods specified in Appendix A.
5.3 Test methods of signal-to-noise ratio
Check the content of the technical data provided by the manufacturer.
Measure the signal-to-noise ratio of the camera system according to the methods
specified in Appendix B.
5.4 Test methods of spatial frequency response
Check the contents of the attached information provided by the manufacturer.
Measure the spatial frequency response of the camera system according to the
methods specified in Appendix C.
5.5 Test methods of static image latitude
Check the contents of the attached information provided by the manufacturer.
Measure the static image latitude of the camera system according to the methods
specified in Appendix D.
5.6 Electrical safety
It shall be carried out in accordance with the test method specified in GB 9706.19.
A.1.4 Image collector
It is required to be able to nondestructively collect and save image data in various
encoding modes.
A.2 Procedures
A.2.1 Test conditions
The temperature of the test environment is (23±2) °C, and the relative humidity is
(50±20) %.
The dark illumination of the test environment is no more than 1lx.
The power supply voltage stability of the control light source shall be controlled within
±2%.
The light source shall be fully preheated and stable.
A.2.2 Test process
A.2.2.1 White balance
For the camera system with white balance function, use A.1.1 test target board to
perform white balance under test conditions.
A.2.2.2 Viewfinder of camera system
Adjust the shooting distance to the desired position and record it as the measurement
working distance d0. For a camera system suitable for visual observation of
endoscopes, d0 is 500mm; other d0 is the design working distance. For zoomable
lenses, measure at the minimum focal length.
A.2.2.3 Focus
If the camera system has an autofocus function, the focus can be slightly blurred when
shooting the test target board to reduce the noise generated by the texture of the block
itself. The emphasis here is "slightly", and the boundaries between blocks shall be
clearly distinguished.
A.2.2.4 Set the brightness of background B on the test target board
Adjust the brightness of background B on the test target board to achieve the
brightness value specified by the manufacturer. During the entire brightness
adjustment process of small grays-sale block A, the brightness of background B shall
keep the overall gain of the tested camera system unchanged.
A.2.2.5 Adjust the brightness of small gray scale block A on the test target board,
Appendix B
(Normative)
Test Methods of Signal-to-Noise Ratio
B.1 Device
B.1.1 Test target board
The same as A.1.1.
B.1.2 Light source
The same as A.1.2.
B.1.3 Image collector
The same as A.1.4.
B.2 Procedure
B.2.1 Test conditions
The same as A.2.1.
B.2.2 Test process
B.2.2.1 White balance
The same as A.2.2.1.
B.2.2.2 Viewfinder of camera system
The same as A.2.2.2.
B.2.2.3 Focus
The same as A.2.2.3.
B.2.2.4 Set the brightness of background B on the test target board
The same as A.2.2.4.
B.2.2.5 Change the brightness of small gray scale block A on the test target
board, collect and analyze images
Gradually change the brightness of the small gray scale block A on the test target board;
proximity shall make the shape of the spectral distribution curve of the light source be
similar to that of the simulated standard illuminator; and the color temperature
tolerance is ±10%.
The arrangement of the illuminance source shall make the illumination uniform in the
area of the target board; and the difference between the brightness at any position in
the area and the center brightness shall be within ±10%.
C.1.3 Image collector
The same as A.1.4.
C.2 Procedures
C.2.1 Measurement conditions
C.2.1.1 Illumination conditions of the measurement target board
The brightness of the measurement target board shall enable the camera system to
produce acceptable output signal levels, but not overexposed.
C.2.2 Test process
C.2.2.1 White balance
The same as A.2.2.1.
C.2.2.2 Viewfinder of camera system
Adjust the shooting distance to the desired position, record it as the measurement
working distance d0, and center the test target board. For a camera system suitable
for visual observation endoscopes, d0 is 500mm; and other d0 is the design working
distance. For zoomable lenses, measure at the minimum focal length.
C.2.2.3 Camera system focus
If the camera system has auto-focus function, the auto-focus system of the camera
system shall be used to focus at the measurement working distance d0. If it is manual
focus, select the sharpest focus setting when the spatial frequency is about 1/4 of the
Nyquist frequency of the camera system.
C.2.2.4 Camera system settings
The image compression function of the camera system may significantly affect the
resolution measurement. Some camera systems may select whether to enable the
image compression function by pressing the button. All setting values of the camera
system may affect the measurement results, including the shooting mode, test distance,
etc., which shall be reported together with the measurement results.
NOTE: Due to the high contrast of the target board, the modulation degree of the target board
may be treated as 1.
If other equivalent sine wave test target boards are used, the result processing shall
refer to the above method equivalently.
C.3 Presentation of results
The test report shall include the following information:
a) The model and number of the camera system under test;
b) Camera mode;
NOTE: It is applicable to camera systems that may adopt multiple camera modes.
c) The characteristics of the used light source;
d) All setting values that may affect the measurement results, such as sharpness
settings (if any), lens conditions (including model, focal length, and/or zoom
status of variable magnification lenses), set the number of pixels or compression
mode, etc.
NOTE: The model of the non-detachable lens is often the same as the model of the
camera system itself.
e) Measurement working distance d0;
f) The number of cycles per circle of the star map; if the test board is not in the form
of a star map, declare the characteristics of the test board;
g) The angular frequency values of the corresponding object space when SFR is
30% and 50%, respectively;
h) Response curve of spatial frequency response (SFR).
D.2.2.5 Change the brightness of small gray scale block A on the test target
board, collect and analyze images
The brightness level change range of the small gray scale block A on the test target
board shall exceed the latitude range; and at least 5 brightness levels shall be lower
than the cut-off critical brightness value of the dark area of the camera system under
test. Near the cut-off critical brightness in the dark and light areas, the ratio of adjacent
brightness levels shall be no greater than 1.1 times.
Gradually change the brightness of the small gray scale block A on the test target board.
For each selected brightness level, measure and record the brightness value as Li; use
the camera system to shoot the test target board of the corresponding brightness; use
the image collector to collect n images and save, n is no less than 8.
For the collected images, select (M × N) pixels (32 × 32 is recommended) in the area
of the small gray-scale block A; and respectively read the output signals of the output
signal (M × N × 3) matrix corresponding to red, green, and blue channels in each image.
D.2.2.6 Calculate the brightness signal component according to the output
signal values of each channel of red, green and blue
The same as B.2.2.6.
D.2.2.7 Draw the curve of brightness and its corresponding brightness signal
output value
According to the Li and 𝑌ത i obtained in procedures D.2.2.5 and D.2.2.6, draw the curve
of brightness and its corresponding brightness signal component.
D.2.2.8 Read the brightness saturation critical value of the highlighted area Lsat
Read the critical brightness value Lsat when the brightness signal component 𝑌ത i of the
highlighted area on the curve is close to the saturation value.
NOTE: When any channel reaches saturation, it is saturated.
D.2.2.9 Calculate the cut-off critical value of brightness of the dark area Lmin
Read the critical brightness value Lmin when the brightness signal component 𝑌ത i in the
dark area on the curve starts to cut off.
Judgment of cut-off state: TAKE the 2 times of average value of random noise that is
calculated according to B.2.2.7 plus average value of brightness signal component 𝑌ത i
corresponding to the 5 groups of lower brightness levels obtained in D.2.2.5 AS the
threshold value. Find the data whose brightness output signal value is greater than the
threshold value and closest to the threshold value; the brightness corresponding to the
data is the critical brightness value Lmin.