1. When starting the focimeter, it usually performs a self check. The machine will check if the optical path is unobstructed and free from foreign objects. If the screen displays an error or the system cannot be accessed normally after booting up, first check whether the lens cover of the measuring lens is open. The above error message may also occur when the lens is first placed on the lens holder and then turned on.

2. When the optical path of the power meter is unobstructed, it is found that the power meter cannot return to zero after entering the system. There are several reasons for the above situation: ① The focal length meter works for a long time, and the working environment has an impact on the optical path system, such as dust accumulation on the support. At this point, simply remove the measuring base cap, wipe the cover glass with a clean silicone cloth or lens paper, and then reinstall it The optical components above the lens dot structure of the focimeter are prone to oil and dust during use. You can use a cotton ball dipped in a small amount of alcohol to gently wipe them clean.
3. Optical center deviation observed in the focimeter

① Place the+15.00 spherical mirror standard lens on the measuring base, align it with the center and let the prism degree return to 0, print the center mark, then rotate the lens and align it again until the prism degree is 0, print the center mark, and half of the distance between the two center marks should not exceed 0.4mm. If it exceeds the limit, the limit screw above the dotting mechanism can be adjusted to align the axis mark of the optical center with the optical axis of the focimeter. After that, tighten the fixing screw and perform calibration until it meets the requirements.
② The dotting mechanism of an automatic focimeter generally uses a ten thousand pen. When the ink of the Wanci pen is used up, there may also be a phenomenon where the focal point meter is unable to dot or the dot is unclear. At this time, the dot mechanism can be removed and the ink can be refilled into the pen, or a new Wanci pen can be directly replaced.
③ The focal length meter measures the deformation of the base, and the edge is not on a horizontal plane. In this case, the lens is placed in an inclined state, causing the optical center to exceed the tolerance. This situation can only be solved by replacing the entire base cap.
④ Incorrect operation or impact of the focimeter can also cause displacement and deformation of the optical components, resulting in optical axis deviation. The entire problem will seriously affect the use of the focimeter and require repair at the factory.

4. There is a difference in the display value of the focimeter
① The wear of the lens measurement base caused deviation from the standard position, resulting in readings exceeding the tolerance. The wear of the measuring base has a serious impact on the data measurement of the instrument, especially when measuring the height of the lens, there is a large error. Moreover, there is no linear relationship between the changes in the affected measurement data. If the wear is minor, it can be improved by attaching an anti wear gasket to the lens base. If the wear is severe, the entire base can only be replaced.
② Partial power meters have the function of measuring ordinary lenses and contact lenses, and they need to use different caps for detection. If the wrong cap is used during detection, it can also cause data to exceed the standard. So when checking the lenses, check if you have used the right cap.
③ The focimeter is sensitive to strong light environments, so when inspecting the lens, try to maintain a soft indoor light. Excessive light can cause unstable readings, making it difficult to align with the optical center, and resulting in out of tolerance at the calibration point. If the above situation occurs, adjusting the position of the focimeter or using low light or no light illumination can solve it.

5. About the parameter settings of the focimeter
① Selection of display interval: The function menu is divided into four levels: 0.01D, 0.06D, 0.12D, and 0.25D. 0.01D should be selected as the display interval for the instrument. If 0.25D or 0.12D is chosen as the indication interval of the instrument, its measurement accuracy may not be as good as that of a manual focusing focimeter. Because the resolution accuracy of some manual focusing focometers has reached 0.05D.
② Selection of column mirror mode: The menus for this function are “-“, “+”, and “+/-” respectively. According to regulations, the column mirror mode should be set to a mixed gear “+/-“. This can measure both positive and negative astigmatism, which matches the settings of the refractometer.
③ Prism selection: The menus for this function are “Do not display”, “Cartesian coordinates”, and “Polar coordinates”. When setting this function, there are two situations. When calibrating the focal length, the prism should choose polar coordinates. When using a focimeter to detect glasses or lenses, a Cartesian coordinate should be selected. This is a method of representing the direction of the prism base, which decomposes the total prism degree into horizontal and vertical directions, forming two components of prism degree. Because the human eye has different tolerance to horizontal and vertical prism angles.
④ The Abbe number is generally set to around 58, which is related to the refractive index of the lens. At present, the refractive index of eyeglass lenses on the market ranges from 1.49 to 1.81, and the Abbe number ranges from 31 to 60. The higher the refractive index, the lower the Abbe number. The standard lens developed by the China Institute of Metrology has a refractive index of 58.9 corresponding to the Abbe number. Therefore, the regulation stipulates that the automatic focal length meter should be calibrated under this condition to ensure accurate, reliable, and consistent transmission of measurement values. The reference wavelengths of the LM-600PD fully automatic focimeter are divided into two types: e-line (green mercury line light source) and d-line (yellow helium line light source). There are significant differences in the top power readings measured at different reference wavelengths. According to the JJG580-2005 “Verification Regulations for Power Meters”, e-spectral lines are uniformly used as the reference wavelength. Therefore, regardless of the type of light source used in the power meter, the reference wavelength of the power meter should be set to e-spectral lines during calibration.
⑤ When conducting calibration, the “auto save reading” function should be set to the “off” state. If the “Auto Save Readings” function is set to “On”, it will result in poor repeatability of the measurement results.