Zeiss humphrey HFA II-i series, Руководство по обслуживанию на месте

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Humphrey Field Analyzer II - i General Information
Confidential and Proprietary
52235C1105 1 - 15
Field Service Guide
1.7.4 HFA II - i Light Intensity Fundamentals
The HFA II - i uses one detector mounted at the end of the turret to measure both spot and bowl
intensities. The projection lamp voltage is controlled by software to set maximum stimulus
brightness. This means that the lamp can be operated at a lower voltage when the lamp is new;
and as it ages, more voltage is applied in order to maintain the same level of brightness. This
increases lamp life expectancy and reduces power consumption.
During light intensity calibration, the projection calibration value is stored in memory and set as
close as possible to obtain 929 Ft-L or 10,000 asb of light output. The background lights are
fluorescent and the calibration values are set as close as possible to obtain 2.92 Ft-L or 31.5 asb.
During calibration, light attenuation is measured at 175 different points on each of the two ND
wedges, and the results are stored in memory. The two ND wedges are used in combination to
obtain the desired brightness of the projected spot. The duration of the spot is 200 ms and is
controlled by the software operating the shutter, located between the projection lamp and the
ND wedges.
During the power-on sequence, the bowl intensity is set to the calibrated value (2.92 Ft-L or
31.5 asb). The brightness detector is then pointed at a black patch located on the inside of the
front cover, the shutter is closed, and a measurement is made by the detector. This establishes
the zero asb reference. Next, the shutter is opened, and a spot projected on the bowl
approximately 35
E
above center is measured by the detector. The projection voltage is adjusted
to match the calibration value stored in memory. This measurement sets the maximum
brightness level (10,000 asb, or 0 dB). These two measurement points determine the slope of
the light from dark to maximum brightness.
If the measured intensity varies from that stored during calibration, the lamp voltage is adjusted
and measured again. This continues until the stored intensity and measured intensity match. If
the voltage is adjusted above 10 V, the test will fail and a projection lamp error message will
appear on the screen. If the test does not fail, ten different points on each ND wedge are
measured and compared with their stored values. If these values deviate more than ±.5 dB
from the stored values, the test will fail and a wedge failure error message will be displayed.
1.7.5 Comparing HFA II and HFA II - i
Hardware -
The HFA II - i version differs from the prior production version, the HFA II, in that significant
upgrades have been made.
The HFA II - i uses an off-the-shelf CPU PCB featuring an Intel Celeron 433 MHz processor,
while the HFA II uses a 20 MHz Motorola 68020-based processor. The new CPU PCB
dramatically decreases the test processing time resulting in significant overall test time reduction.
The
HFA II - i CPU PCB contains 64 megabytes of DIMM memory while the HFA II has 4
megabytes of memory on the current CPU. The increase is significant in the ability to support
software features planned for the future; in particular, the implementation of
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Ensemble . In