KR100953885B1 - Apparatus and Method for Aligning Optic Axis of Lens Module - Google Patents

Abstract

The present invention relates to a lens module optical axis alignment device and method, and more particularly to a light source; A screen disposed at a predetermined distance from the light source and configured to pass light emitted from the light source through a plurality of openings formed in a central region and an outer portion of the light source; A lens module disposed at a predetermined distance from the screen, the lens module including a barrel and a variable lens temporarily connected to a tip of the barrel and passing light passing through the opening of the screen; A detector configured to form light passing through the variable lens; A control unit electrically connected to the detection unit to measure an eccentric position of a variable lens and determine a moving position of the variable lens; And a driving unit electrically connected to the control unit mounted on the variable lens and the control unit, the driving unit including a drive unit for driving linear movement of the control unit mounted on the variable lens. Through the lens module optical axis alignment device and method, the assembly process of the lens module can be performed quickly, suitable for mass production, and the lens module can exhibit high integration and high pixel optical performance.

Lens module, optical axis alignment, variable lens, modulation transfer function, line spread function, careful

Description

Lens module optical axis alignment device and method {Apparatus and Method for Aligning Optic Axis of Lens Module}

The present invention relates to a lens module optical axis alignment device and a lens module optical axis alignment method including the same. More particularly, in aligning the optical axis of the lens module for a phone camera, it is possible to quickly perform the assembly process of the lens module, The present invention relates to a lens module optical axis alignment device and method that is suitable for production and enables the lens module to exhibit high integration, high pixel optical performance.

Recently, the demand for camera phones continues to increase, and accordingly, the demand for high integration and high pixel camera phones is increasing.

The optical system used in camera phones has been composed of plastic lenses of aspherical shape. Such plastic lenses have the disadvantages of easy aspherical shape and easy thermal deformation and birefringence.

In order to compensate for the shortcomings of plastic lenses while aiming for high resolution, camera phone optical systems are improving performance by combining plastic lenses and optical glass lenses.

The camera phone lens, which is a multifunctional advanced optical system, is made by advanced optical design and precision processing, and its demand is soaring and mass production is required.

As these camera phones become more advanced, there is a need for an optical performance evaluation apparatus and method for quantitatively and real-time measuring optical performance of pre-assembly units and post-assembly camera phone modules.

In general, optical component evaluation technology measures various types of evaluation items from the manufacturing stage, and various measurement techniques have been developed to increase measurement accuracy during such measurement. In particular, when manufacturing a lens module, the mechanical center of the lens barrel is developed. It is important to precisely perform the eccentric adjustment for matching the axis and the optical axis of the lens accommodated in the lens barrel, and it is particularly important to precisely perform the optical axis adjustment for matching the optical axis between the lenses accommodated in the lens barrel.

In the case of an optical system composed of a plurality of components, an evaluation method by optical transfer function (OTF) measurement is generally used to see the average performance of the optical system, and the optical transfer function is an amplitude portion of a modulation transfer function (Modulation). Transfer Function (MTF) and Phase Transfer Function (PTF) which is a phase part.

Among them, the modulation transfer function is mainly used to express the performance of the optical system, and various methods of measuring the modulation transfer function have been proposed.

The present invention is to solve the above problems, an object of the present invention is to align the optical axis of the lens module for the phone camera, it is possible to quickly perform the assembly process of the lens module, suitable for mass production, the lens The present invention provides a lens module optical axis alignment device and method for enabling a module to exhibit high integration, high pixel optical performance.

Lens module optical axis alignment device according to an aspect of the present invention is a light source; A screen disposed at a predetermined distance from the light source and configured to pass light emitted from the light source through a plurality of openings formed in a central region and an outer portion of the light source; And a lens module disposed at a predetermined distance from the screen, the lens module including a barrel and a variable lens temporarily connected to the tip of the barrel and configured to pass light passing through the opening of the screen.

In addition, the lens module optical axis alignment device according to an aspect of the present invention comprises a detection unit for forming the light passing through the variable lens; A controller electrically connected to the detector and configured to determine a movement position of a variable lens; And a driving unit electrically connected to the control unit mounted on the variable lens and the control unit, and a driving unit driving a linear movement of the control unit mounted on the variable lens.

At this time, it is preferable that a plurality of openings are formed in the outer portion of the screen constituting the lens module optical axis alignment device according to an aspect of the present invention so as to be symmetrical with each other in the horizontal and vertical directions about the opening of the central region.

Lens optical axis alignment method according to an aspect of the present invention by irradiating a light source to the screen having a plurality of openings formed in the central region and the outer region, passing the light source passing through the opening through the lens module, and then through the lens module It is preferable to include the step (a) of imaging one light source to the detection unit.

In addition, in the lens module optical axis alignment method according to an aspect of the present invention, after step (a), the modulation transfer function (MTF) of each field of the detector is measured, so that the symmetrical field of the field having the lowest modulation transfer function value is lensed. It is preferred to include the step (b) of determining the eccentric position of the variable lens of the module.

In addition, the lens module optical axis alignment method according to an aspect of the present invention after the step (b), after measuring the difference between the modulation transfer function value at the spatial frequency of the two fields symmetrically located in the horizontal direction and the vertical direction, It is preferable to include the step of changing the position of the variable lens of the lens module in the horizontal direction or vertical direction so that the difference value is the minimum.

As described above, the lens module optical axis alignment device and method according to the present invention can quickly perform the assembly process of the lens module, it is suitable for mass production, the lens module can exhibit high integration, high pixel optical performance You can do that.

Hereinafter, a lens module optical axis alignment device according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a conceptual diagram illustrating a lens module optical axis alignment device according to an embodiment of the present invention, FIG. 2 is a front view of a detector constituting the lens module optical axis alignment device according to an embodiment of the present invention, and FIG. 3 is line spread. Graph showing a function.

Lens optical axis alignment device according to an embodiment of the present invention is disposed at a predetermined distance from the light source 1 and the light source, and passes the light emitted from the light source through a plurality of openings formed in the central region and the outer portion. A screen 10.

In this case, a plurality of openings are formed in the outer portion of the screen 10 so as to be symmetrical with each other in the horizontal and vertical directions about the opening of the central area, and the openings are formed in pinholes, slits, or quadrangular shapes. It can be formed, in this embodiment was formed as a slit.

The opening of the screen 10 is divided into a portion that allows light to pass through and a portion that does not allow light to pass through. The size of the screen 10 varies as much as the size that can be projected to the entire screen according to the viewing angle specification of the optical axis adjusting lens module. Various openings can be selected from the optical axis region to the non-axis region to be slit-shaped, pinhole-shaped, or square-shaped openings.

In addition, the lens module alignment device is disposed at predetermined intervals such that the non-stock fields symmetrically located in the central axis of the screen 10 are positioned in the vicinity of the viewing angle of the optical axis adjustment target lens of 50 degrees or more, and the barrel 21 and The lens module 20 and the light passing through the variable lens 22 and the lens module 20 is temporarily bonded to the front end of the barrel 21, including a variable lens 22 for passing the light passing through the opening of the screen (10). This detection unit 30 is formed.

At this time, the detection unit 30 is composed of a CCD (charge-coupled device) or CMOS sensor, the image corresponding to the position of each opening formed in the screen 10 is formed.

In addition, it may further include a relay lens (not shown) disposed between the lens module 20 and the detector 30, through which the light passing through the lens module passes.

The relay lens may be configured as a magnification lens for matching the size of the imaging surface of the lens module to adjust the optical axis and the size of the detector sensor.

In addition, the lens module alignment device is electrically connected to the detection unit 30, to calculate the resolution to determine the eccentricity of the variable lens 22, and to measure the eccentric position of the variable lens 22, A controller (not shown) for determining a movement position; And a driving unit 24 electrically connected to the control unit 23 mounted on the variable lens 22 and the control unit and driving linear movement of the control unit 23 mounted on the variable lens 22. It includes a drive unit, the drive unit 24 may be configured as a servo motor or PIEZO drive device.

In this case, the barrel 21 may be accommodated in a mounting hole formed in a tray (not shown), and a plurality of mounting holes are formed in the tray, and the plurality of lens modules 20 are disposed in the mounting holes, respectively. The optical axis alignment of the lens module 20 may be continuously performed while transferring the tray.

The control unit constituting the lens module optical axis alignment device according to an embodiment of the present invention includes a measurement unit for measuring the modulation transfer function at the spatial frequency of the image formed in the detector; A comparator for comparing the difference between modulated transfer function values formed in the horizontal and vertical directions on the outer portion of the detector; And an adjusting unit for changing the position of the variable lens by adjusting the driving unit so that the compared difference values are minimum.

On the other hand, the control unit includes a measuring unit for calculating the half-height width by measuring the line spreading function of the image formed in the detector; A comparison unit for comparing the difference between the half-height widths of the images formed in the horizontal and vertical directions on the outer portion of the detection unit; And an adjusting unit for changing the position of the variable lens by adjusting the driving unit so that the compared difference values are minimum.

Lens module optical axis alignment device according to an embodiment of the present invention includes a control unit as described above, it is possible to measure the eccentricity in real time when adjusting the optical axis of the variable lens, it is possible to perform the optical axis alignment quickly.

As shown in FIG. 4, the lens module optical axis aligning apparatus of the embodiment of the present invention includes a light source 101, a screen 110 having a plurality of openings, a lens module 120, and a detector 130. It includes.

In another embodiment, the screen 110 includes an opening 111 formed in the central region and a plurality of openings 112 to 115 formed to be symmetrical in the horizontal and vertical directions, respectively.

In this case, in the screen 10 described above, the openings formed in the outer portion are formed to be symmetrical in the diagonal direction. In the screen 110 of the present embodiment, the openings are arranged in the form of a cross, and the openings are formed to be symmetric in the vertical and horizontal directions. have.

In addition, in the present embodiment, the detection unit 130 extends in the vertical and horizontal directions, respectively, and is composed of two linear sensors 132 and 131 which cross each other in the central region.

In this case, the light passing through the lens module is irradiated to two linear sensors 132 and 131 extending in the vertical and horizontal directions by beam splitters having the same transmittance and reflectance, respectively.

In the case of using one 2D image sensor like the detection unit 30 of the above-described embodiment, the more the image is shifted from the optical axis, the more the modulation transfer function value is generated, so that the measurement is easier. The openings formed in the are arranged in a diagonal direction about the opening of the central area.

However, when two linear sensors are used, the length of the sensor is long, so that even if an opening is formed in the form of a column cross on the outside of the screen 110, the value of the modulation transfer function of each field can be easily measured. .

Therefore, the screen 110 and the detector 130 according to the present exemplary embodiment have a different structure from the above-described screen 10 and the detector 130.

A method of aligning an optical axis of a lens module using the lens module optical axis alignment device configured as described above will be described in detail with reference to the accompanying drawings.

Lens module optical axis alignment method according to an embodiment of the present invention uses a modulation transfer function (MTF) of the light transfer function.

This modulation transfer function is one of the lens performance evaluation methods and is an important indicator of the lens's ability to reproduce the contrast of image detail. This modulation transfer function is measured by contrast reproducibility, the spatial frequency is indicated on the horizontal axis, and the contrast reproducibility is indicated on the vertical axis.

Lens optical axis alignment method according to an embodiment of the present invention is irradiated with light from the light source 1 to the screen 10 having a plurality of openings formed in the central region and the outer region, the light (1) passing through each opening (1) And passing the lens module 20 through the lens module 20 and imaging the light passing through the lens module 20 to the detection unit 30.

An opening is formed in the center portion of the screen 10, and a plurality of openings are formed in the outer portion so as to be symmetrical with each other in the horizontal and vertical directions about the opening.

In this case, the opening may be formed as a pinhole, a slit, or a rectangular shape, and in the present embodiment, the opening is formed as a slit.

The lens module 20 includes a barrel 21 and a variable lens 22 temporarily connected to a tip of the barrel, and is mounted on the variable lens 22 to adjust a position of the variable lens 22. The position of the variable lens 22 of the lens module 20 may be changed by the driver 23 driving the linear movement of the control unit 23 and 23.

In this case, the barrel 21 may be accommodated in a mounting hole formed in a tray (not shown), and a plurality of mounting holes are formed in the tray, and a plurality of lens modules are disposed in the mounting hole, respectively, and the tray is transferred. It is also possible to perform optical axis alignment continuously.

As shown in FIG. 2, each image formed in the detection unit 30 corresponds to the shape of the opening formed in the screen and the arrangement thereof.

A central field 31 corresponding to the slit formed in the central area of the screen 10 and a plurality of fields 32 to 35 are formed so as to be symmetrical in the horizontal and vertical directions about the central field.

For convenience of explanation, the images formed in the detection unit 30 are referred to as the first field 32, the second field 33, the third field 34, and the fourth field 35 in turn.

Thereafter, a line spread function (LSF) of each field is obtained, and a full width at half maximum (FWHM) of the line spread function is measured.

In this case, the line spread function may be obtained by differentiating an edge spread function (ESF) obtained for a transverse or longitudinal edge when the number of screens is rectangular. It can be obtained by Fourier transform the line spread function.

The narrower the half-height width of the line spread function, the higher the resolution. The higher the value of the modulation transfer function over the entire spatial frequency, the better the resolution.

Thus, the resolution and performance of the lens can be measured using the half height width of the line spread function and the modulation transfer function.

On the other hand, when the opening has a pinhole shape, a point spread function (PSF) may be calculated, a point spread function and an intensity distribution function of the image may be calculated, and then the line spread function may be approximated to obtain the line spread function. .

Hereinafter, the modulation transfer function used in the lens module optical axis alignment device according to each embodiment of the present invention will be described in detail.

5 is a block diagram showing an apparatus for measuring the MTF of the lens, Figure 6 is a graph showing the slit light intensity distribution, Figure 7 is a graph showing the light intensity distribution on the slit.

Generally, when measuring the MTF of a lens, the screen 201 with a slit, the lens 202 for a measurement object, and the detection part (image sensor) 203 are arrange | positioned in order.

그리고 공간주파수를 u로 나타내면 위와 같이 렌즈의 MTF M(u)(하기 수학식 1)는 상면에서 배율에 의한 슬릿의 이상적인 광세기 분포 O(x)(도 6참조)와 실제 상의 광세기 분포 함수(도 7 참조)에 대한 푸리에 변환 값의 비로서 나타낼 수 있다. At this time, slit width, measurement magnification lens magnification, image sensor pixel spacing

If the spatial frequency is expressed as u, the MTF M (u) (Equation 1) of the lens as shown above is the ideal light intensity distribution O (x) (see FIG. 6) of the slit by the magnification on the image plane and the light intensity distribution function of the actual image. It may be expressed as the ratio of the Fourier transform value to (see FIG. 7).

In this embodiment, after auto focusing, the symmetric field of the field having the minimum modulation transfer function is determined as the eccentric position of the variable lens 22 of the lens module 20 (step (b)).

For example, when the half height width of the line spread function measured in the second field 33 is the minimum, the fourth field 35 is determined as the eccentric position.

Then, the X axis direction (horizontal direction) alignment and the Y axis direction alignment (vertical direction) are performed in turn (step (c)), and the X axis direction alignment is a modulation transfer function at the spatial frequency of the first field and the second field. The X-axis driver 24 of the variable lens while measuring the difference between the values and the difference between the modulation transfer function values at the spatial frequencies of the third and fourth fields, respectively, and measuring in real time the points where the difference values become minimum values, respectively. Control to change the position of the variable lens 22 to the point where the difference value is the minimum.

When the X-axis alignment is completed, the Y-axis alignment (vertical) alignment is performed, the Y-axis alignment is the difference between the modulation transfer function value at the spatial frequency of the first field and the fourth field and the second field and the third field The difference between the modulation transfer function values at the spatial frequency of the field is measured, and the Y-axis driver 24 of the variable lens is measured in real time while measuring the points where the difference values become minimum values in real time. The position of the variable lens 22 is changed to the point where it becomes.

At this time, the modulation transfer function value of each field 32 to 35 of the outer portion cannot exceed the modulation transfer function value of the center field 31, and the values of the respective fields of the outer portion are not equal to each other. If the difference occurs above the reference value, repeat step (b) to step (c) one or more times.

Alternatively, after auto focusing, the symmetric field of the field having the minimum half-width of the line spread function is determined as the eccentric position of the variable lens 22 of the lens module 20 (step (b)).

For example, when the half height width of the line spread function measured in the second field 33 is the minimum, the fourth field 35 is determined as the eccentric position of the variable lens.

Then, the X-axis direction (horizontal direction) alignment and the Y-axis direction (vertical direction) alignment are performed in sequence (step (c)), and the X-axis alignment is performed by the half height width difference between the first field and the second field and the third alignment. The half height width difference between the field and the fourth field is respectively measured, and the position of the variable lens 22 is changed by controlling the driving unit 24 while measuring the point where the difference becomes the minimum value in real time.

When the X-axis alignment is completed, Y-axis alignment is performed, and Y-axis alignment measures the half height width difference between the first field and the fourth field and the half height width difference between the second field and the third field, respectively. The position of the variable lens 22 is changed by controlling the driving unit 24 while measuring the point where the difference value becomes the minimum value in real time.

Hereinafter, a lens module optical axis alignment method according to another embodiment of the present invention.

Until now, the alignment of the X-axis direction and the Y-axis direction is sequentially performed through one detection unit 30. However, in another embodiment of the present invention, the detection unit extends in the vertical and horizontal directions, respectively, and crosses each other in the center region. Composed of two linear sensors, and in step (c) it is possible to simultaneously change the position of the variable lens 22 of the lens module 20 in the horizontal direction and vertical direction, even in this case Can be changed in the manner described above.

In this case, the light passing through the lens module is irradiated with two linear sensors 132 and 131 respectively extended in the vertical and horizontal directions by light beams having the same transmittance and reflectance.

That is, after performing step (a) described above, the driving unit is controlled to minimize the difference in the half-height width or the difference in the modulation transfer function value measured from the image formed in the linear sensor extending in the horizontal direction. Align the variable lens of the lens module in the horizontal direction.

At the same time as the horizontal alignment, the variable lens of the lens module is vertically controlled by controlling the driving unit to minimize the difference in the half height width or the difference in the modulation transfer function value measured from the image formed in the linear sensor extending in the vertical direction. Can be aligned in the direction.

In this way, by using two linear sensors extending in the horizontal direction (X-axis direction) and vertical direction (Y-axis direction) and connecting separate control units, respectively, the optical axes can be aligned independently in each direction simultaneously. Thus, the optical axis alignment speed is increased.

In addition, by using a high-resolution high-speed linear CCD sensor, resolution can be measured precisely and quickly, and the physical length of the light detection area of the linear sensor is long, so that the stockpile area of the screen can be inspected to be larger. Since the resolution difference between each field is large, the degree of eccentricity can be detected accurately.

Subsequently, when the optical axis alignment process of the variable lens 22 is completed, the variable lens 22 is adhered to the barrel 21, and the plastic lens is sequentially pressed into the barrel 21 to complete the lens module.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art having various ordinary knowledge of the present invention may make various modifications, changes, and additions within the spirit and scope of the present invention. And additions should be considered to be within the scope of the following claims.

1 is a conceptual diagram illustrating a lens module optical axis alignment device according to an embodiment of the present invention.

2 is a front view of a detection unit constituting the lens module optical axis alignment device according to an embodiment of the present invention.

3 is a graph showing a line spread function.

4 is a conceptual diagram illustrating a lens module optical axis alignment device according to another embodiment of the present invention.

5 is a block diagram showing an apparatus for measuring the MTF of the lens.

6 is a graph showing a slit light intensity distribution.

7 is a graph showing the light intensity distribution on a slit.

Claims (9)

delete Light source; A screen disposed at a predetermined distance from the light source and configured to pass light emitted from the light source through a plurality of openings formed in a central region and an outer portion of the light source; A lens module disposed at a predetermined distance from the screen, the lens module including a barrel and a variable lens temporarily connected to a tip of the barrel and passing light passing through the opening of the screen; A detector configured to form light passing through the variable lens; A control unit electrically connected to the detection unit to measure an eccentric position of a variable lens and determine a moving position of the variable lens; And And a driving unit electrically connected to the control unit mounted on the variable lens and the control unit, and including a driving unit driving a linear movement of the control unit mounted on the variable lens. A plurality of openings are formed in the outer portion of the screen so as to be symmetrical with each other in the horizontal and vertical directions about the opening of the central region, The opening of the lens module optical axis alignment device, characterized in that formed in a pinhole, square or slit shape. The method of claim 2, wherein the control unit, A measuring unit for measuring a modulation transfer function at the spatial frequency of an image formed in the detector; A comparator for comparing the difference between modulated transfer function values formed in the horizontal and vertical directions on the outer portion of the detector; And And an adjusting unit which adjusts the position of the variable lens by adjusting the driving unit such that the compared difference values are minimized, respectively. The method of claim 2, wherein the control unit, A measuring unit for calculating a half-height width by measuring a line spreading function of an image formed in the detector; A comparison unit for comparing the difference between the half-height widths of the images formed in the horizontal and vertical directions on the outer portion of the detection unit; And And an adjusting unit which adjusts the position of the variable lens by adjusting the driving unit such that the compared difference values are minimized, respectively. The method of claim 2, And the detection unit is two linear sensors extending in a horizontal direction and a vertical direction, respectively, wherein the linear sensors cross each other in a central region. (a) irradiating light to a screen having a plurality of openings formed in a central region and an outer region, passing a light source passing through the opening through the lens module, and then imaging the light source passing through the lens module in the detection unit; (b) measuring a modulation transfer function (MTF) at the spatial frequency of each field of the detector to determine a symmetric field of a field having the lowest modulation transfer function as an eccentric position of the variable lens of the lens module; And (c) measuring the difference between the modulation transfer function values of the two fields symmetrically positioned in the horizontal and vertical directions, and then moving the horizontal direction toward the central axis at the eccentric position of the variable lens of the lens module such that the difference is minimum Or changing in the vertical direction. The method of claim 6, Step (b) obtains the line spread function (LSF) of each field formed in the detection unit, and shifts the symmetric field of the field having the minimum half-width width (FWHM) of the line spread function to the eccentric position of the variable lens of the lens module. Decide, Step (c) measures the difference between the modulation transfer function values of the two fields symmetrically positioned in the horizontal and vertical directions, and then adjusts the central axis at the eccentric position of the variable lens of the lens module so that the difference values are minimum. Lens module optical axis alignment method characterized in that for changing in the horizontal direction or vertical direction. The method of claim 6, The detection unit of step (a) is two linear sensors extending in the vertical and horizontal directions, respectively, and intersecting with each other in the center area, and step (c) sets the position of the variable lens of the lens module in the horizontal and vertical directions. Lens module optical axis alignment method characterized in that for changing at the same time in the direction. The method of claim 6, And a plurality of openings are formed in the outer portion of the screen in the step (a) so as to be symmetrical with each other in the horizontal and vertical directions about the opening of the central region.

Images