Focal Meter Technical Requirements

1) The fit of each moving part of the focal meter should be moderately tight; Reading handwheel should be flexible, accurate positioning; Adjustable baffle movement should be balanced; Printing mechanism to rotate light; The printing mark should be clear, and the diameter of the trace should not be greater than 0.5mm; The press lens mechanism should be stable and reliable.
2) The imaging of the optical system of the focometer should be clear, and the brightness in the field of view or on the projection screen and reading window should be uniform, without oil, water stains, mold spots and other defects that significantly affect the reading.
3) The continuous display type focal meter should be straight, uniform, obvious writing, no broken line, the scale and the indicator line should be parallel and should be marked with different colors of positive and negative top focal. Digital display type focal meter sign and digital display should be complete without broken pen, indicating stable value without obvious drift and flicker.
4) When the lens is not placed, the residual prism degree inherent in the focal meter shall not be greater than 0.1△.
5) The parallax error of visual and projection focometers shall not be greater than 0.1△.
6) Top focal value error requirements. The zero error of the focal meter of various display modes shall not be greater than ±0.03D. Among them, the zero indication error of spherical and cylindrical degree of focal meter with 0.01D division shall not be greater than ±0.02D after the specified preheating time. For focal meters of various display modes, the tolerance between the measured value of the top focal of a spherical standard lens (specified in JJG 866-94) and the standard value of a standard lens is shown in Table 1. In the digital display focal meter, the tolerance between the measured value of the top focal value and the standard value is performed according to the rounding rule of the numbers in Table 1 (omitted).
7) Requirements for the error of the prism degree: for the focal meter of various display modes, the tolerance between the measured value of the prism degree and the standard value of the standard lens of the prism standard lens (specified in JJG 866-94) is shown in Table 2. In the digital display focometer, the tolerance between the prism degree measurement value and the standard value is performed according to the rounding rule of the numbers in Table 2 (omitted).
8) The deviation between the axial position mark of the optical center of the lens and the optical axis of the focal meter shall not be greater than 0.4mm.
9) The deviation between the direction from 00 to 1800 of the axis position dial and the axis position mark shall not be greater than 10.
10) The parallel deviation between the adjustable baffle and the axis position dial from 00 to 1800 shall not be greater than 10.
11) The instrument should meet the requirements of ZBY002 under transportation and packaging conditions, of which +40℃ is selected for high temperature test, -25℃ is used for low temperature test, and 250mm is used for free drop height first.