Abstract:
A detecting apparatus includes a light source configured (i.e., structured and arranged) for irradiating the lens module with light, the light being brought into a focus by the lens module; a detecting device configured for measuring and recording a location of the focus; and a driving device configured for driving a barrel of the lens module to rotate relative to a holder of the lens module. The detecting apparatus is particularly configured such that, when the driving device drives the barrel of the lens module to rotate to two different angular locations, the light source irradiates the lens module with light, the lens module making the light be brought into two respective focuses at (i.e., relative to) the two different angular locations, and the detecting device measures a deviation distance between the two respective focuses. A method of detecting concentricity of a lens module is further provided.

Description:
BACKGROUND 
   1. Technical Field 
   The present invention relates to a concentricity-detecting apparatus and method for precisely detecting a level/degree of concentricity of a lens module. 
   2. Description of Related Art 
   Nowadays, with the development of the optical imaging technology, camera modules are now in widespread use. Camera modules are being combined with various portable electronic devices such as mobile phones, PDAs (personal digital assistants) and portable computers, to make such devices increasingly multi-functional. 
   A typical camera module generally has a lens module mounted therein. The lens module is coupled with an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) so as to capture images. Generally, the lens module includes a holder and a barrel pivotably received in the holder. A plurality of lenses and spacers is alternately received in the barrel. Preferably, an infrared-cut filter that blocks light in the infrared spectrum is also fitted in the lens module to prevent interference. Before the qualified lens module is entered in a market, the imaging quality of the lens module after assembly must be ensured. Accordingly, the degree/level of the concentricity of the holder and the barrel therein the hold must be detected, in order to ensure that the camera qualifies to be sold on the market. 
   Conventionally, manual detection for concentricity of the lens module has low efficiency and speed, to a certain degree. Further, the concentricity of the lens module may not be precisely measured, due to operators error and/or skill limitations. Therefore, it is nearly impossible to ensure that every detected lens module is qualified when relying on manual inspection. 
   An improved apparatus and method for precisely detecting concentricity of the lens module is thus desired to thereby overcome the above-mentioned disadvantages. What is needed, therefore, is a detecting apparatus and method for precisely detecting/measuring the level/degree of concentricity of a lens module. 
   SUMMARY 
   In a present embodiment, the detecting apparatus includes a light source configured for irradiating the lens module with light, the light being brought into a focus by the lens module; a detecting device being configured for measuring and recording a location of the focus; and a driving device configured for driving a barrel of the lens module to rotate relative to a holder of the lens module. The detecting apparatus is particularly configured such that, when the driving device drives the barrel of the lens module to rotate to two different angular locations, the light source irradiates the lens module with light, the lens module making the lens module bring the light into two respective focuses at (i.e., relative to) the two different angular locations, and the detecting device measures a deviation distance between the two respective focuses. 
   A method of a detecting concentricity of a lens module, comprising the steps of:
     (a) providing a driving device for driving a barrel of the lens module to rotate relative to a holder of the lens module;   (b) providing a light source for irradiating the lens module, the light source to be brought into focus relative to a given lens module position, the lens module being driven to rotate by the driving device to yield different focuses;   (c) providing a detecting device for measuring a deviation distance between the different focuses, thereby judging the concentricity of the lens module.   

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Many aspects of the present apparatus and method for detecting a concentricity of a lens module can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present apparatus and method. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
       FIG. 1  is a schematic view of a detecting apparatus for detecting concentricity of a lens module according to a first present embodiment; 
       FIG. 2  is similar to  FIG. 1 , but a barrel is rotated to another position; and 
       FIG. 3  is a schematic view of a detecting apparatus for detecting concentricity of a lens module according to a second present embodiment. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Embodiments will now be described in detail below and with reference to the drawings. 
   Referring to  FIG. 1 , a detecting apparatus  100  for detecting concentricity of a lens module  10 , according to a first present embodiment, includes a driving device  16 , a light source  18 , and a detecting device  20  for detecting a potential deviation of an optical (i.e. focal) axis of the lens module  10 . The lens module  10  includes a barrel  12  and a holder  14  for receiving the barrel  12  therein. The lens module  10  inherently has at least one lens (not specifically shown) mounted therein. 
   The driving device  16  includes a driving rod  161 , a friction block  162  mounted on the driving rod  161 , a retaining member  163  configured for limiting movement of the driving rod  161 , and a motor (not shown). The driving rod  161 , located/positioned over a top end of the lens module  10 , can be selectably moved back and/or forth by the motor (e.g., a servo-motor). The friction block  162  is mounted on a bottom portion of the driving rod  161  and is configured for contacting the barrel  12 , thereby avoiding damage of the barrel  12 . Advantageously, the friction block  162  is made of a rubber material with a high friction coefficient, in order to enhance friction between the driving rod  161  and the barrel  12 . Therefore, when the driving rod  161  drives the barrel  12  to rotate relative to the holder  14 , the driving rod  161  is prevented from sliding relative to the barrel  12 , thereby avoiding damage to a surface of the barrel  12 . According to the first embodiment, the following relation is satisfied between the driving rod  161  and the barrel  12 : L=θr, wherein L is an effective length of the driving rod  161 , and θ is a rotary angle that the barrel  12  is driven to rotate relative to the holder  14 , and r is a radius of the barrel  12 . In the first present embodiment, θ can, for example, be rotated to an rotary angle of 180 degrees. θ may be, e.g., 60 degrees, 90 degrees, 120 degrees, and so on. Further, the angle θ can be precisely controlled by moving the driving rod  161 . 
   The motor is used to drive the driving rod  161  to selectably move back and/or forth. The motor may, e.g., be a stepping motor, a DC (Direct Current) motor, or a servo motor and so on. 
   The retaining device  163  is used to limit the driving rod  161  to move in a linear direction relative to the barrel  12 , as indicated by an arrow in  FIGS. 1 and 2 . A guiding hole  1631  is defined in the retaining device  163  and is configured for allowing the driving rod  161  to move back and/or forth along a defined horizontal direction (i.e. that shown by the arrow). The retaining device  163  may be another device, so long as the device can restrict/guide the movement of the driving rod  161 . 
   A plurality of lens (not shown) is received in the barrel  12 . An optical/focal axis of the barrel  12  should substantially overlap an optical/focal axis of the lens module  10 , so long as they are appropriately configured/aligned. That is, the focus point of the lens module  10  should not vary significantly with a change of the rotational angle of the barrel  12  (as per a focusing step), if the lens modules  10  and the barrel  12  are properly aligned. The light source  18  is located over the top end of the lens module  10 . A beam of light rays  182  emitted from the light source  18  is set to be parallel to a properly-aligned the optical axis of the lens module  10 . The light source  18  irradiates the lens module  12  to cause the lens module  12  to create a focus. 
   The detecting device  20 , situated under the lens module  10 , is used to detect a deviation of the actual optical axis of the lens module  10  from the expected one. That is, the detecting device  20  is able to determine an actual focus location and is able to compare such to other measured focus locations and/or to an expected or theoretical focus location. Advantageously, the detecting device  20  is situated below the lens module  10 , generally in expected optical alignment therewith, so as to be able to record a position of the actual focus of the lens module  10 . The detecting device  20  may be a light sensor, such as a charge coupled device (CCD). 
   Referring to  FIG. 2 ,  FIG. 2  is similar to  FIG. 1  except that the barrel  12  has been driven by the driving device  16  to rotate to another position. When the light source  18  irradiates the barrel  12  for the first time, the detecting device  20  measures the position of the first focus  201  that the lens module  10  projects. The barrel  12  is then rotated to another position. When the light source  18  irradiates the barrel  12  for the second time, the detecting device  20  measures the position of the second focus  202  created by the barrel  12 . Finally, a deviation distance between the first and second focuses  201 ,  202  is measured, via the detecting device  20 . It is then determined if the deviation distance falls into the allowable range. Advantageously, the first and second focuses  201 ,  202  substantially overlap one another. Further beneficially, the first and second focuses  201 ,  202  each overlap an expected/theoretical focal point of the lens module  10 . Therefore, based on the positions of the first and second focuses  201 ,  202 , it can be determined if the lens module  10  is qualified. If the deviation distance falls outside the allowable range, namely, the first and second focuses  201 ,  202  do not overlap one another and/or an expected/theoretical focal point of the lens module  10 . Therefore, based on such a determination, the lens module  10  can be deemed disqualified. 
   Referring to  FIG. 3 , a detecting apparatus  200  for detecting a concentricity of a lens module  10 , according to a second present embodiment, includes a driving device  26  configured for driving the barrel to rotate, a light source  18 , and a detecting device  20  configured for detecting a potential deviation of an optical (i.e., focal) axis of the lens module  10 . The lens module  10  includes a barrel  12  and a holder  14 . 
   The driving device  26  includes a pair of juxtaposed driving rods  261 , a pair of friction blocks  262 , a retaining member  263 , and a motor (not labeled). The pair of friction blocks  262  is mounted on a bottom portion of each driving rod  261 , each being respectively configured for contacting the barrel  12 , respectively. The retaining member  263  is configured for selectably adjusting movement of the pair of driving rods  261 . The two driving rods  261 , situated over a top end of lens module  10 , can be selectably moved back and/or forth by the motor. Beneficially, the friction block  262  is made of a rubber material with a high friction coefficient to enhance friction between the driving rod  161  and the barrel  12 . Therefore, when the pair of driving rods  261  drives the barrel  12  to rotate relative to the holder  14 , the two driving rods  261  are prevented from sliding relative to the barrel  12 , and thereby are not capable of damaging a surface of the barrel  12 . When the two driving rods  261  drive the barrel  12  to rotate relative to the holder  14 , one of the two driving rods  261  moves forward, and the other driving rod  261  moves backward at the same time. According to the second embodiment, the following relation is satisfied between the driving rod  261  and the barrel  12 : L′=θr, wherein L′ is a length of the driving rods  261 , and θ is a rotary angle that the barrel  12  is driven to rotate relative to the holder  14 , and r is a radius of the barrel  12 . Thus, the rotary angle θ can be precisely controlled via moving the two driving rods  261 . In the second embodiment, the detecting method for detecting concentricity of a lens module  10  is similar to the detecting method in the first embodiment. 
   The method of detecting concentricity of the lens module  10  includes the following steps. 
   (a) providing the light source  18 . The light source  18  is located over the top end of the barrel  12 . The light source  18  irradiates the lens module  10 , the lens module  10  thereby forming the first focus  201 . 
   (b) providing the detecting device  20 . The detecting device  20  is located under a bottom end of the barrel  12 . The detecting device  20  measures and records the position of the first focus  201 . 
   (c) providing the driving device  16 . The driving device  16  has the driving rod  16  with the friction block  162  mounted thereon. The driving rod  16  can be selectably driven to move back and/or forth. When the friction block  162  of the driving rod  16  drives the barrel  12 , the barrel  12  is rotated to an angle θ. 
   The light source  18  irradiates the lens module  10  again. The lens module  10  projects light on the detecting device  20  again to create the second focus  201 , and, simultaneously, the detecting device  20  measures and records the position of the second focus  201 . The deviation distance between the first and second focuses  201 ,  202 , is measured via the detecting device  20 . If the deviation distance falls into the allowable range, namely, the first and second focuses  201 ,  202  substantially overlap, the lens module  10  is thus considered qualified. If the deviation distance falls outside the allowable range, namely, the optical axis of the barrel  12  does not overlap the optical axis of the lens module  10 . The lens module  10  is thus disqualified. It is to be understood that the qualified/unqualified reading could then be displayed/notified in any various fashion (e.g., green/red notification lights; e-mail and/or mobile-phone message; notice sent/transmitted to a display screen; etc.). 
   While certain embodiment has been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The present invention is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.