Handheld apparatus for measuring lens surface power

Abstract

This invention discloses a handheld apparatus for measuring surface power or radius of prescription ophthalmic spectacle lenses, optical lenses or molds blocked with or without chuck during Rx production, and after comparing measurement results with designed data, providing correction data to the processing machines via wireless connection for correction processing if needed. The handheld apparatus integrates an optical measurement head into a monolithic optical system.

Claims

1. A handheld apparatus for measuring lens surface power including spherical power, cylindrical power and cylinder axis of an ophthalmic lens or a mold blocked with or without a chuck during Rx production, the apparatus comprising: an optical measurement head, wherein the optical measurement head comprises optical components including at least one or more first reflective prisms, a second reflective prism, a converging lens, a ring-shaped aperture, a beam splitter and an image sensor, wherein the one or more first reflective prisms are configured to redirect a light beam, incident on the one or more first reflective prisms, to the converging lens thereby obtaining a converged light beam, wherein the beam splitter is configured to reflect the converged light beam and project the converged light beam reflected on a surface of the lens or mold, and wherein the beam splitter is further configured to project a light beam reflected from the lens surface or the mold on the ring shaped aperture, and wherein the second reflective prism is configured to reflect the light beam reflected from the lens surface or the mold and project the reflected light beam from the lens surface or the mold on the image sensor in order to form an image; and a main control body, wherein the main control body comprises a data processing and control unit and a display screen, wherein the data processing and control unit is configured to perform analysis of the image in order to calculate surface power, and wherein the display screen is configured to display results of the analysis performed by the data processing and control unit.

2. The handheld apparatus of claim 1, wherein the optical measurement head is a monolithic optical system, and wherein the optical components are connected to each other by an optical contact bonding or a glue cement.

3. The handheld apparatus of claim 1, wherein the ophthalmic lens or the mold blocked on the chuck is placed against a lens support of the optical measurement head.

4. The handheld apparatus of claim 3, wherein the lens support comprises a ruby or stainless steel or sapphire ring in order to contact the lens surface.

5. The handheld apparatus of claim 1, wherein the main control body further comprises a wireless communication module configured for receiving and sending lens parameters and results between a Rx server and the handheld apparatus.

6. The handheld apparatus of claim 5, wherein the wireless communication module uses a communication protocols chosen from one of the following GSM, GPRS, 3G, LTE, Bluetooth, WiFi, WLAN.

7. The handheld apparatus of claim 1, wherein the main control body is smart mobile phone, and wherein the light beam incident on the one or more first reflective prisms is a LED light of the smart mobile phone.

8. The handheld apparatus of claim 1, wherein the light beam incident on the one or more first reflective prisms is provided by a light source comprised in the optical measurement head.

9. The handheld apparatus of claim 1, wherein the spherical surface power (S) of the lens or mold is calculated by a mathematical equation, $S=\frac{\left(n-1\right)}{R}\times 1000\mathrm{where}n=a\mathrm{refrative}\mathrm{index}\mathrm{of}\mathrm{the}\mathrm{lens}\mathrm{or}\mathrm{mold},R=\mathrm{radius}\mathrm{of}\mathrm{curvature}\mathrm{of}\mathrm{surface}.$
S=(n−1)/R×1000 where n=a refractive index of the lens or mold, R=radius of curvature of surface.

10. The handheld apparatus of claim 9, wherein the radius (R) is calculated by a mathematical equation, $R=\frac{2}{\frac{1}{l}+\frac{1}{l^{\prime }}}\mathrm{where}$ $l=\mathrm{object}\mathrm{distance}$ $l^{\prime }=\mathrm{image}\mathrm{distance}.$
R=2/1/l+1/l′ where l=object distance l′=image distance.

11. The handheld apparatus of claim 10, wherein the object distance (l) is distance from converging point on the optical axis of an incident light beam to the intersecting point of the optical axis on the lens surface.

12. The handheld apparatus of claim 10, wherein the image distance (l′) is additive inverse of sum of distance of the intersecting point of the optical axis of the lens surface to the intersecting point of the optical axis on the ring aperture, distance of the intersecting point of the optical axis on the ring aperture to the intersecting point of the optical axis on the image sensor and the distance of the intersecting point of the optical axis on the image sensor to converging point on the optical axis of the reflected light beam.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The present invention will be understood and appreciated more from the following detailed description, along with the supplemental drawings in which:

(2) FIG. 1a and FIG. 1b illustrate an external view of a handheld apparatus according to the preferred embodiment of the present invention;

(3) FIG. 2 shows the principle of the surface power measurement apparatus;

(4) FIG. 3 illustrates a monolithic optical system according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) FIG. 1a and FIG. 1b show a handheld measurement apparatus according to one embodiment of the present invention, and is respectively a front view and a left-side view of the measurement apparatus in working status. As shown in FIG. 1a and FIG. 1b, the handheld measurement apparatus includes a data processing unit (here we call it a smartphone) such as smart mobile phone 1 as the main control body and an optical measurement head 3 which is fixed on the back side of the smart mobile phone 1. During Rx production, an ophthalmic lens blank or mold 5 is blocked on a chuck 7 via alloy or wax 6. The surface generating machine and polishing machine clamp the chuck 7 on their work piece spindle and process the top surface of the lens blank or mold 5. After polishing, the lens or mold 5 blocked on the chuck 7 is placed against the lens support 4 of the measurement head 3 and the local optical surface power, e.g., spherical power, cylinder power and cylinder axis, of the small surface area where the lens or mold 5 contacts the lens support 4 can be measured and displayed on the display screen 2 of the smart mobile phone 1. The small surface area to be measured can be the center of a single vision lens or mold or the far-view and near-view reference points of a progressive lens or mold or any other point on the surface.

(6) FIG. 2 shows the optical principle of the surface power measurement apparatus. As shown in FIG. 2, an incident light beam 9 converges at a point A on the optical axis 13. The surface to be measured is placed against a fixed lens support which intersects with the optical axis 13 at a point O. A ring-shaped aperture 11 with a fixed radius r and an image sensor 12 are fixed on the same side as the incident beam 9 and intersect with the optical axis 13 at points S and C. The incident beam 9 reaches the surface and is reflected. The reflected light beam 10 goes through the ring-shaped aperture 11 and forms an image on the image sensor 12.

(7) First assume that the surface 8 is a spherical surface with a radius of curvature R, then the reflected light beam 10 will also converge at a point A′ on the optical axis 13, and the image formed on the sensor 12 will be a round ring with a radius c. In this illustrated optical system, an object at point A forms an image at point A′ by the reflective surface 8. According to FIG. 2, the object distance l and image distance l′ can be described by the following equations:
l=OA  (1)
l′=−(OS+SC+CA′)  (2)
where OA, OS and SC are already known.

(8) According to homothetic triangle theory, there is:

(9) $\begin{array}{cc}\frac{\stackrel{\_}{{\mathrm{CA}}^{\prime }}}{\stackrel{\_}{\mathrm{SC}}}=\frac{c}{r-c}& \left(3\right)\end{array}$

(10) Thus equation (2) can be rewritten as:

(11) $\begin{array}{cc}{l}^{\prime }=-\left(\stackrel{\_}{\mathrm{OS}}+\stackrel{\_}{\mathrm{SC}}+\frac{c}{r-c}\stackrel{\_}{\mathrm{SC}}\right)=-\left(\stackrel{\_}{\mathrm{OS}}+\frac{r}{r-c}\stackrel{\_}{\mathrm{SC}}\right)& \left(4\right)\end{array}$

(12) According to the imaging formula of a reflective sphere, there is:

(13) $\begin{array}{cc}\frac{1}{l}+\frac{1}{l^{\prime }}=\frac{2}{R}& \left(5\right)\end{array}$

(14) Hence, the radius of curvature R of surface 8 is:

(15) $\begin{array}{cc}R=\frac{2}{\frac{1}{l}+\frac{1}{l^{\prime }}}=\frac{2}{\frac{1}{\stackrel{\_}{\mathrm{AO}}}-\frac{1}{\stackrel{\_}{\mathrm{OS}}+\frac{r}{r-c}\stackrel{\_}{\mathrm{SC}}}}& \left(6\right)\end{array}$

(16) The spherical power S of surface 8 can thus be calculated by:

(17) $\begin{array}{cc}S=\frac{n-1}{R}\times 1000=500\left(n-1\right)\left(\frac{1}{\stackrel{\_}{\mathrm{AO}}}-\frac{1}{\stackrel{\_}{\mathrm{OS}}+\frac{r}{r-c}\stackrel{\_}{\mathrm{SC}}}\right)& \left(7\right)\end{array}$
where n is the refractive index of the lens or mold 5.

(18) When the surface 8 is a cylinder surface with two radii of curvature R.sub.1 and R.sub.2 on its two orthogonal principal meridians, the image formed on the sensor 12 will be an elliptic ring with a major radius c.sub.1 and a minor radius c.sub.2. The two spherical power S.sub.1 and S.sub.2 on the two orthogonal principal meridians of the cylinder surface can be calculated by:

(19) $\begin{array}{cc}{S}_1=\frac{n-1}{R_1}\times 1000=500\left(n-1\right)\left(\frac{1}{\stackrel{\_}{\mathrm{AO}}}-\frac{1}{\stackrel{\_}{\mathrm{OS}}+\frac{r}{r-c_1}\stackrel{\_}{\mathrm{SC}}}\right)& \left(8a\right)\\ S_2=\frac{n-1}{R_2}\times 1000=500\left(n-1\right)\left(\frac{1}{\stackrel{\_}{\mathrm{AO}}}-\frac{1}{\stackrel{\_}{\mathrm{OS}}+\frac{r}{r-c_2}\stackrel{\_}{\mathrm{SC}}}\right)& \left(8b\right)\end{array}$

(20) The cylinder power C can be calculated by:
C=|S.sub.1−S.sub.2|  (9)

(21) And the cylinder axis is the orientation of the major axis of the elliptic ring image on the sensor 12.

(22) FIG. 3 illustrates a monolithic optical system according to the preferred embodiment of the present invention with the aid of which the above-described principle can be carried out. The smart mobile phone includes an LED flash light 14 and a CMOS image sensor 15. The monolithic optical system comprises optical components including reflective prisms 16, 17, 18 and 19, support prisms 20, 21 and 22, a converging lens 23, a ring-shaped aperture 24, and a beam splitter 25 and CMOS image sensor 15. All the optical components and CMOS image sensor are fixed with each other by optical contact bonding or glue cement.

(23) During measurement, the LED flash light 14 or additional separated LED works as the light source of the optical measurement head. The light beam emitted from the LED flash light 14 is redirected by the reflective prisms 16, 17 and 18, and goes along the optical axis 27 inside the monolithic optical system. A converging lens 23 converts the light beam from the light source into the desired beam which is reflected by a beam splitter 25 and is projected onto surface 26 of the lens or mold to be measured. The light beam reflected from surface 26 goes through the beam splitter 25, a ring-shaped aperture 24, and is then reflected by a reflective prism 19 to be projected onto the CMOS sensor 15 to form an image. The image is analyzed by the smart mobile phone and the surface power of the local surface where the lens support contacts is calculated and displayed on the display screen of the smart mobile phone.

(24) In one embodiment of the present invention, the lens support includes a polished ruby, stainless steel or sapphire ring to contact the lens surface in order not to damage the surface to be measured.

(25) In a further preferred embodiment of the present invention, the smart mobile phone includes a wireless communication module, e.g., GSM, GPRS, 3G, LTE, Bluetooth or WiFi or WLAN. When measuring a lens or mold, the smart mobile phone communicates with the Rx server via the wireless communication module and gets the designed surface data. The smart mobile phone calculates the theoretical local surface power and compares it with the measured result and tells if the lens or mold is ok or not.