Method and apparatus for lens auto-focusing in camera module test

1. A method of lens auto-focusing in camera module test, comprising the following steps:

providing testing equipment, wherein the testing equipment comprises a range finder, a signal processor and a driving member all connected electrically;

providing an imaged object;

providing an camera module comprising a lens and an image sensor, wherein a view angle and the biggest value of modulation transfer function of the lens module are both certain values; an image of the imaged object is formed in the image sensor; the imaged object and the image formed thereby in the other side of the lens module are fixed;

inputting an initial image distance tested by the range finder into the signal processor, wherein the signal processor calculates the initial image height based on the initial image distance, and further calculates a displacement for the driving member using a linear equation: x=n(y−S 1 ), wherein x is the displacement of the driving member, y is the image height when the lens at focusing point, S 1 is the initial image height, n is equal to 1/tan θ, and θ is the view angle of the lens; and

generating a controlling signal via the signal processor and sending the signal to the driving member to control it, driving the lens module to a focusing point via the driving member.

2. The lens auto-focusing method in camera module test as claimed in claim 1 , wherein the biggest modulation transfer function value of the lens module is input into the signal processor before testing.

3. The lens auto-focusing method in camera module test as claimed in claim 1 , wherein the driving member is a driving motor or a solenoid valve.

4. The lens auto-focusing method in camera module test as claimed in claim 1 , wherein the displacement of the driving member is equal to the displacement of the lens module during the test.

5. The lens auto-focusing method in camera module test as claimed in claim 1 , wherein the signal processor is electrically connected with the range finder and the driving member.

6. An apparatus for lens auto-focusing in camera module test, wherein the camera module comprises a lens module, a view angle and the biggest value of the modulation transfer function of the lens module are certain values, an imaged object and an image formed thereby in the other side of the lens module are fixed, the apparatus comprising:

a range finder for measuring an image distance;

a signal processor calculating the displacement of the lens module based on an initial image distance tested by the range finder and a linear equation: x=n(y−S 1 ), wherein x is the displacement of the driving member, y is the image height when the lens at focusing point, S 1 is the initial image height, n is equal to 1/tan θ, and θ is the view angle of the lens; and

a driving member for driving the lens module to move, and the range finder, the signal processor and the driving member being connected electrically.

7. The testing equipment as claimed in claim 6 , wherein the image height is a certain value when the lens module is in the best position.

8. The testing equipment as claimed in claim 6 , wherein driving member is a driving motor or a solenoid.

9. The testing equipment as claimed in claim 6 , wherein the displacement of the lens module is equal to the displacement of the driving member during the test.