JPH0476434A - Automatic lens meter - Google Patents

Abstract

PURPOSE:To obtain a measured value equal to that of a standard manual lens meter by calculating measured values of measuring light rays having different wavelengths in accordance with compensating coefficients which correspond to dispersive values of a lens to be tested, or to the inverse numbers thereof, and with which the measured values which are different from each other due to differences in wavelength are compensated. CONSTITUTION:Signals from two image sensors 18 are delivered to a comparator 22 and a peak hold circuit 23 through a CCD drive circuit 21. A peak voltage detected by the circuit 23 is converted into a half voltage signal by a D/A converter 26, and is delivered to the comparator 22. This signal and the signal delivered directly to the comparator 22 are compared with each other, and a signal from a counter 27 is delivered to a latch 28 in response to a strobe signal delivered from the comparator, and the positions of bright and dark edges are read from the waveforms of the signal at that time, thereby the coordinate values thereof are detected by a computer 25. In order to compensate the coordinate values for errors in measurement caused value degrees of dispersive values of a lens to be tested, an Abbe values which are reverse of the dispersive values are set and inputted to a computer 25 by way of an Abbe number input switch 29, and the measured value is corrected in accordance with compensating coefficients obtained from the Abbe numbers.

Description

[Detailed description of the invention] “Industrial Application Fields” The present invention relates to automatic lensmeters.

[Prior Art] Various measuring devices have been proposed regarding lens meters that automatically measure various optical characteristics of eyeglass lenses.

These automatic lens meters usually do not use halogen lamps or tungsten lamps, but instead use light emitting diodes (hereinafter referred to as LEDs) due to the complexity of their configurations, such as the need for multiple light sources.

However, commonly used manual lens metamers use a halogen lamp or a tungsten lamp as a light source, and the wavelength of this light source is from 546 nm to 588 nm.

On the other hand, the wavelength of LED is usually about 660 nm, and there is a difference in wavelength between the two.

Lenses have the property that their refractive index varies depending on the wavelength of light, and this property is called dispersion. Due to this property, the refractive power of the test lens depends on the measurement wavelength.
There is a difference in the measured values between an automatic lens meter using an LED and a general manual lens meter. That is, when the wavelength of light becomes long (the refractive power decreases due to dispersion), the measured value of an automatic lens meter is lower than that of a manual lens meter.

[Problems to be Solved by the Invention] If there is an error in the measurement value as described above, there is a drawback that accurate measurement cannot be performed.

The present invention was devised in view of the above-mentioned problems, and a technical problem is to provide an automatic lens meter that can obtain measurement values equal to those of a manual lens meter.

[Means for Solving the Problems] In order to achieve the above object, the configuration of the present invention is to provide an automatic lens that automatically measures optical characteristics such as spherical power and astigmatic power of a test lens inserted into a measurement optical system. In the meter, a measurement light source that emits measurement light of a certain wavelength, a manual means for inputting the dispersion value or the reciprocal of the dispersion value of the test lens, and corresponding to the dispersion value or the reciprocal of the dispersion value of the test lens, It is characterized by having a storage means for storing a correction coefficient for correcting a measurement difference due to a difference in wavelength, and an arithmetic means for calculating a measurement value using measurement light of a different wavelength based on the correction coefficient stored in the storage means. shall be.

Further, the measurement light source is an LED diode.

Further, the measurement value corrected by the correction coefficient is a measurement value using measurement light of 545 nm to 588 nm.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an external view of an automatic lens meter which is an embodiment of the present invention.

1 is a display, which consists of a reticle that shows the optical axis of the measurement optical system as the center, an alignment target 2 (Fig. 1 is a corona target and will be described in detail later), and an LED dot matrix display that displays measurement results, etc. Ru. 3 is a print switch that prints the measurement results, 4
5 is an addition measurement switch for switching to addition measurement mode;
6 is a left/right selection switch, and 6 is a switch for reading measured values.

7 is a lens holder, 8 is a nose piece, place the lens to be measured on the nose piece 8, and hold the lens holder 6.
Lower the lens and hold the lens under test.

Next, one embodiment of the measurement optical system of an automatic lens meter will be described.

FIG. 2 is a layout diagram of the optical system of the automatic lens meter.

Reference numeral 11 indicates light emitting diodes such as LEDs, and four light emitting diodes such as LEDs are arranged near the focal point of the objective lens 12 and perpendicular to the optical axis.

When the lens 15 to be tested is set on the nose piece 8, the LED driver is activated according to instructions from the computer, and the four LEDs a, b, c, and d- are turned on in sequence.

13 is a measurement target plate having orthogonal slits, and includes an objective lens 12 and a collimating lens 14.
It is fixedly or movably arranged near the focal point of the image.

The nosepiece 8 is arranged near the focal point of the collimating lens 14 and the imaging lens 16.

17 is a half prism, and 18 is an image sensor provided perpendicular to the optical axis.

The light from the LED is passed through the collimating lens 14 by the objective lens 12. Test lens 15. Images are formed on two orthogonal image sensors I8 via the imaging lens 16, respectively.

As shown in FIG. 3, signals from the two image sensors 18 are input to a comparator 22 and a peak hold circuit 23 via a CCD drive circuit 21. The peak voltage manually detected by the peak hold circuit 23 is
The signal is converted into a digital signal by the converter 24 and then input to the computer 25 . The peak voltage digital signal output from the peak hold circuit 23 is sent to the computer 2.
5, the D/A converter 26 outputs 1/2 of the peak voltage.
is converted into a voltage signal and input to the comparator 22. This signal is compared with the signal directly input to the comparator 22 to generate a strobe signal. The signal from the counter 27 enters the latch 28 in response to the strobe signal, the position of the bright and dark edge is read from the waveform at that time, and the coordinate position is detected by the computer 25.

Next, a method for calculating measured values from the detected coordinate positions will be briefly described.

Target 13 is individually illuminated with four LEDs.
When there is no test lens or when the OD test lens is placed on the nosepiece 8, LEDa, b, c,
The target images formed on the image sensor 18 by each of the two images overlap each other.

When the lens 15 to be tested has only spherical refractive power, the position of the target image formed on the image sensor 18 moves by an amount corresponding to the spherical refractive power.

When the lens 15 to be tested has only cylindrical refractive power, the refractive power acts on the light beam incident on the cylindrical lens in a direction perpendicular to (or in the same direction as) the principal axis. The cylindrical refraction power can be calculated from the amount of movement of this target image.

If the lens 15 to be tested has both spherical refractive power and cylindrical refractive power, the target image is formed by moving on the image sensor 18 by an amount corresponding to each refractive power value.

Now, when LEDs a, b, c, and d are turned on, the center of the target image is A (x,, y,), respectively.
B(xl,, y,), C(y,, yc)
, D (x,, V/), and X,=l
x, -X, /I, X2=lx, -x, IY+ "1y
If we set 2.5'cl Y2=ly,,yd, then the spherical power S - Goto A and Yu.

The computer 25 detects this coordinate position, calculates the spherical refractive power, cylindrical refractive power, axial angle, and prism amount based on the above-mentioned calculation formula, and displays the values digitally.

If the lens to be tested has a dioptric power (refracting power) other than OD, the four target images will be blurred and the image positions will be shifted by an amount proportional to the dioptric power, causing a measurement error.

Therefore, in an actual apparatus, it is desirable to move the measurement target so as to reduce the amount of deviation due to blurring, and calculate the optical characteristics of the lens to be tested from the amount of movement of the measurement meter and the image position.

Next, a method of correcting measurement errors caused by the magnitude of the dispersion value of the lens to be tested and obtaining a measurement value equal to the measurement value of a manual lens meter will be described.

To this end, the automatic lens meter of this embodiment may have a built-in function for inputting the dispersion value of the lens to be tested to correct measurement errors due to the dispersion value. - Since the Atsube number, which is the reciprocal of the variance value, is often used for boat fishing, enter this value. There is almost a correlation between the Atsube number and the measurement difference. Therefore, as shown in Figure 4, it is possible to eliminate measurement errors by making a table of the relationship between the Atsube number and the correction coefficient, inputting it into the computer 25, storing it, and correcting the measured value using the correction coefficient determined from the Atsube number. can. The relationship between the Atsube number and the correction coefficient may be an approximate function.

When creating this correction coefficient, it is important to note that if the material of the lens with a predetermined power used when adjusting the automatic lens meter is crown glass, which is used in eyeglass lenses, The measurement error due to the variance value is not an error due to the variance other than the adjustment error. Therefore, a lens to be tested having the same dispersion value as the dispersion value of the lens used at the time of power adjustment will not produce an error due to dispersion. However, recently, in order to make lenses thinner and lighter, spectacle lenses made of glass or plastic with a high refractive index, called high refractive lenses, have become popular. Although this lens had a high refractive index, its dispersion increased, resulting in the measurement error described above.

Therefore, the coefficient for correcting the measured value of the lens under test whose dispersion value is different from the dispersion value of the lens used for adjustment is 66.
The refractive index at 0 nm and the refractive index at 546 nm are determined in advance, and the correction coefficient is calculated using the following formula.

nel...Refractive index nc of the adjustment lens at 546 nm
l...Refractive index ne2 of the adjustment lens at 660 nm
... refractive index of the test lens at 546 nm nc2 ... refractive index of the test lens at 660 nm, correction coefficient: nC1/ne1 nc 2 / ne 2 is obtained. As a result, the graph shown in FIG. 4 is created.

The further corrected measurements are Corrected measured value = measured value x correction coefficient It is determined by

Next, the operating method for performing the above correction will be explained.

Immediately after turning on the power switch, the currently set Atsube number will be displayed on the display.

If the Abe number of the lens to be tested is equal to the set Abe number, it is sufficient to directly measure it.

If you want to measure a lens made of a different material, that is, a lens with a different Atsbe number, input the new Atsbe number using the switch and y switch before making the change, calculate the correction coefficient using the memorized relationship shown in Figure 4, and then measure. All you have to do is correct the value.

[Effects of the Invention] According to the automatic lens meter of the present invention, by correcting the measured values, it is possible to obtain measured values that are equal to the measured values of a manual lens meter that is generally used as a reference.

[Brief explanation of drawings]

FIG. 1 is a front view showing the automatic lens meter of this embodiment. FIG. 2 is a layout diagram of the optical system of this automatic lens meter. FIG. 3 is a block diagram showing the control system of the automatic lens meter according to the embodiment. FIG. 4 is a graph showing the relationship between the Abbe number and the correction coefficient. 1...Display 2...Alignment target 3...Print switch 4...Additional power measurement switch 5...Left/right selection switch 6...Reading switch 7...Lens holder 8... nose piece

Claims (3)

[Claims] (1) Spherical power of the test lens inserted into the measurement optical system,
An automatic lens meter that automatically measures optical properties such as astigmatism power includes a measurement light source that emits measurement light of a certain wavelength, an input means for inputting the dispersion value or the reciprocal of the dispersion value of the lens to be tested, and a lens meter to be measured. a storage means for storing a correction coefficient that corresponds to the dispersion value or the reciprocal of the dispersion value of the detection lens and corrects a measurement difference due to a difference in wavelength; and a storage means for storing a correction coefficient for correcting measurement differences due to differences in wavelength; An automatic lens meter characterized by having a calculation means for calculating a measured value. (2) An automatic lens meter characterized in that the measurement light source in item 1 is an LED diode. (3) The measured value corrected by the correction coefficient in the first term is 54
An automatic lens meter characterized by measuring values using measurement light of 6 nm to 588 nm.