CN103149789B - The method of testing of module motor curve is evaluated based on image MTF - Google Patents
The method of testing of module motor curve is evaluated based on image MTF Download PDFInfo
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- CN103149789B CN103149789B CN201310063935.XA CN201310063935A CN103149789B CN 103149789 B CN103149789 B CN 103149789B CN 201310063935 A CN201310063935 A CN 201310063935A CN 103149789 B CN103149789 B CN 103149789B
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Abstract
The invention provides a kind of method of testing evaluating module motor curve based on image MTF, selection can reflect camera lens out of focus situation of change and test motor characteristics conforming MTF as sharpness computation function, then analyze according to the MTF of motor curve to motor diverse location of MTF matching, judge the kinetic characteristic of motor, when testing motor curve, find out the peak position of the motor curve at display image four angles simultaneously, the focal length difference of corner is obtained by calculating corner location, judge that the inclined height of camera lens and sensor surface is poor, calculate angle of inclination.The motor curve testing scheme of the present invention's application, by using MTF test chart and image detecting apparatus, effectively detected the motor characteristics of module and the bad of motor inclination aspect, ensure that the quality of product.
Description
Technical field
The present invention relates to mobile phone camera module motor curve test method, especially relate to the technical method of the AF mobile phone camera module motor curve test evaluated based on image MTF.
Background technology
At present along with the widespread use of AF (auto-focusing) mobile phone camera, the assembling inclination caused due to reasons such as processing procedure and motor supplied materials and motor abnormal problem often occur.How being detected by this defective products will be the key guaranteeing product quality.Classic method uses the mode of laser ranging to test the dynamic tilt of motor curve and motor.The dynamic tilt of motor can not inclination between complete reaction camera lens and sensor, therefore, study a kind of can inclination accurately between detector lens and sensor the method simultaneously can testing motor curve will be particularly important.
Summary of the invention
The present invention is a kind of novel AF mobile phone camera module motor curve test method evaluated based on image MTF, the method is used to test the performance of module motor, described method the inclination accurately between detector lens and sensor also can reflect the performance of testing motor simultaneously, described a kind of method of testing evaluating module motor curve based on image MTF, comprises the following steps:
1) target and back light is selected, adjustment height support is utilized to adjust the distance of target to Camera Test module, the focal position of described distance corresponding test module, be the focusing clearly object distance position of motor when running to half stroke to positive dirction of test module, Camera Test module be placed on the test position of graphic transmission equipment;
2) back light above target is opened, start graphic transmission equipment, Initialize installation is carried out to test module, the target image of described test module shooting is square, then drive the motor operation of Camera Test module, the target image transmitting that test module is taken by described graphic transmission equipment is to computing machine;
3) fixed step size is set, the motor controlling test module runs at positive and negative two traffic directions of motor according to setting step-length, motor often runs a step-length, control test module and take a target image, and utilize image definition algorithm to calculate the mtf value of target picture centre, with motor operation step-length for x-axis, with each step-length for the mtf value calculated for Y-axis draws the positive and negative step-length of two traffic directions of motor and the relation curve of mtf value, be similar to normal distribution curve according to the motor class of a curve of mtf value matching;
4) normal distribution curve is analyzed, the two ends lifting position of described normal distribution curve is respectively enable position and the stop position in motor operation direction, the linearity of the smoothness reflection motor operation of described curve, the difference of the normal distribution curve peak position of positive and negative two traffic directions of motor is that motor is sluggish.
Wherein, the image of described Computer display is 1/8th sizes of the target image that test module photographs.
When testing, the method for testing step at the angle of inclination of motor is as described below:
(1) in motor positive dirction testing results, draw the mtf value at target image four angles and the curve of motor step-length, four class of a curve of drafting are similar to normal distribution curve simultaneously;
(2) four peak positions of four curves are found out, four mtf values of corresponding Y-axis, the sequencing of described peak refers to the sequencing of X-direction, the vergence direction of motor is the overturning angle at angle first the peak place from last peak place, the horizontal ordinate difference of first peak and last peak position is the difference of motor step number, according to camera lens when same field focuses the object of same distance, the characteristic that the step number of motor operation is identical, can calculate the angle of inclination of motor.
The tangent value at motor angle of inclination is the ratio of the inclined height of motor and the actual physics distance at target image two angles, and the inclined height of described motor can be multiplied with the motor displacement often run corresponding to a step by the difference of motor step number and to draw.
Further, the brightness stability of described back light, the brightness uniformity of back light panel.The size of described target and back light can be full of the whole target image of test module shooting.
The motor curve testing scheme of the present invention's application, by using MTF (modulation transfer function) test chart and image detecting apparatus, change the mode of use laser testing in the past, effectively detected the motor of module and the bad of motor inclination aspect, ensure that the quality of product.Use this method of testing, the bad Product checking of this respect can be gone out.
Accompanying drawing explanation
Fig. 1 is the testing apparatus schematic diagram of embodiments of the invention;
Fig. 2 is the preparation flow process of motor curve test in embodiment;
Fig. 3 is test flow chart in embodiment;
Fig. 4 is the motor curve synoptic diagram according to picture centre MTF matching in embodiment;
Fig. 5 is the peak position view of the motor curve at four angles of image in embodiment;
Fig. 6 is the schematic diagram at motor angle of inclination.
Embodiment
Problem to be solved by this invention is AF mobile phone module motor abnormal products to detect, and provides a kind of motor curve measuring technology scheme evaluated based on image MTF.Foundation is for fixing object distance, the defocusing amount changing camera lens can change the sharpness of module imaging, by selecting suitable sharpness computation function, can substitute laser ranging, for testing the consistance of motor characteristics, such as starting current, stopping electric current, the linearity, sluggishness etc.In this programme, utilize the MTF of image definition computing function to evaluate and instead of traditional laser testing, the MTF adopting image is because function anti-interference is good for this reason, and can reflect the out of focus situation of camera lens accurately, thus can reasonable evaluation motor curve characteristic.
The operation mainly displacement of motor, the change of displacement is the change of focal length in the performance of camera lens, and the embodiment of the change of focal length on image is the change of image definition, so by the situation of change of MTF, indirectly can test the change in displacement situation of motor, change the change in displacement of camera lens relative to focal position by the relative position changing motor, then by calculating motor operation at the mtf value of diverse location image, just can judge the ruuning situation of motor.
As shown in Figure 1, the parts that described method of testing utilizes have: adjustment height support 1, target 5, back light 4, image capture device 3, test module 2.
As shown in Figure 2, select target 5 and back light 4, adjustment height support 1 is utilized to adjust the distance of target 5 to Camera Test module 2, described distance can according to camera lens depth-of-field guide quick-setting, test module 2 focal position is made just in time to be in the position that motor positive dirction runs to half stroke, the size of described target 5 and back light 4 can be full of the whole image of test module shooting, the brightness stability of described back light 4, evenly, select the image capture device 3 that transmission is stable, need the motor that accurately can control module in testing to drive simultaneously, motor can be run according to preset requirement, then Camera Test module 2 is placed on the test position of graphic transmission equipment 3, and the back light opened above test chart, test.
Described test flow chart as shown in Figure 3, initialization test module, motor is made to be parked in initialized step number, the mark domain that described test module photographs similarly is square, because the figure of the sensor transmissions of test module is square, described image is transferred to computing machine through graphic transmission equipment, and the image of described Computer display is 1/8th sizes of the target image that test module photographs, and this ratio also can adjust.
Time in the initialized step number of motor, the image of display is unsharp, along with the operation of motor positive dirction, image will from unintelligible to clear, motor positive dirction when running to half stroke time the most clearly, the image now on target on the focal length of test module, when motor continues to run, image on target is not on the focal length of test module, and image is from clear to unintelligible.
Motor operation runs according to the fixed step size of setting, obtains the image of place step-length and show image on computers, calculating mtf value and real-time rendering curve, to terminate all mtf values of post analysis at test stroke and to show test results.
According to feature linear between motor displacement and drive current, the MTF of module and optical image are the normal distribution curves centered by focal length apart from the relation presented.According to above 2 points, can derive, use the motor class of a curve of MTF matching to be similar to a normal distribution curve.
As shown in Figure 4, the curve co-insides drawn when the positive and negative both direction of motor is run, motor is when running to positive dirction, enable position is c and stop position is b, motor is when to reverse direction operation, and enable position is b and stop position is c, and process when motor positive dirction is run has been divided into 78 equal portions, and during reverse direction operation, run to setting step-length time and positive dirction have same mtf value.Can be judged the linearity of motor operation by the smoothness of curve, line smoothing, then motor wire performance enough reaches requirement.The motor difference of curve peak position a that both direction is run back and forth be then that motor is sluggish, and curve co-insides illustrates sluggish and standard is completely the same.
Further, in conjunction with lens optical characteristic, directly can test out the degree of tilt between AF process camera lens and sensor, the degree of tilt of motor is exactly the degree of tilt of sensor.When test curve, draw the mtf value at square-shaped image four angles and the curve of motor one direction step-length simultaneously, four curves drawn are also normal distribution curve, and find out four peak positions of four curves, the vergence direction of motor is the overturning angle at angle first the peak place from last peak place, in Fig. 5, upper left corner curve is m1, and upper right corner curve is m2, and lower left corner curve is m3, lower right corner curve is m4, and motor is from the lower left corner to upper right overturning angle.
In Figure 5, the initialized step number of motor is 180step, the horizontal ordinate difference of first peak and last peak position is the difference of motor step number, the sequencing of described peak refers to the sequencing of X-direction, according to camera lens in the identical characteristic of the focal length of same field, the angle of inclination of motor can be calculated, upper left corner m1 arrives focal position prior to lower right corner m4, and difference 25step distance, can determine that motor slope is 0.54 μm/step according to experimental test motor specification, therefore can calculate inclined height difference S is 13.5 μm.As shown in Figure 6, according to design, can determine the actual physics distance L at image two angles, finally calculate tilt angle theta=arctan (13.5/L), described angle of inclination is exactly the angle of inclination between camera lens 6 and sensor 7.
The present invention, by using MTF test, changes the mode of use laser testing in the past, effectively detected the motor of module and the bad of inclination aspect, ensure that the quality of product.Use this method of testing, the bad Product checking of this respect can be gone out.
Claims (6)
1. evaluate a method of testing for module motor curve based on image MTF, comprise the following steps:
1) target and back light is selected, adjustment height support is utilized to adjust the distance of target to Camera Test module, the focal position of described distance corresponding test module, be the focusing clearly object distance position of motor when running to half stroke to positive dirction of test module, Camera Test module be placed on the test position of graphic transmission equipment;
2) back light above target is opened, start graphic transmission equipment, Initialize installation is carried out to test module, the target image of described test module shooting is square, then drive the motor operation of Camera Test module, the target image transmitting that test module is taken by described graphic transmission equipment is to computing machine;
3) fixed step size is set, the motor controlling test module runs at positive and negative two traffic directions of motor according to setting step-length, motor often runs a step-length, control test module and take a target image, and utilize image definition algorithm to calculate the mtf value of target picture centre, with motor operation step-length for x-axis, with each step-length for the mtf value calculated for Y-axis draws the positive and negative step-length of two traffic directions of motor and the relation curve of mtf value, be similar to normal distribution curve according to the motor class of a curve of mtf value matching;
4) normal distribution curve is analyzed, the two ends lifting position of described normal distribution curve is respectively enable position and the stop position in motor operation direction, the linearity of the smoothness reflection motor operation of described curve, the difference of the normal distribution curve peak position of positive and negative two traffic directions of motor is that motor is sluggish.
2. the method for testing evaluating module motor curve based on image MTF according to claim 1, is characterized in that: the method for testing step at the angle of inclination of motor is as described below:
1) in motor positive dirction testing results, draw the mtf value at target image four angles and the curve of motor step-length, four class of a curve of drafting are similar to normal distribution curve simultaneously;
2) four peak positions of four curves are found out, four mtf values of corresponding Y-axis, the sequencing of described peak refers to the sequencing of X-direction, the vergence direction of motor is the overturning angle at angle first the peak place from last peak place, the horizontal ordinate difference of first peak and last peak position is the difference of motor step number, according to camera lens when same field focuses the object of same distance, the characteristic that the step number of motor operation is identical, can calculate the angle of inclination of motor.
3. the method for testing evaluating module motor curve based on image MTF according to claim 1, is characterized in that: step 2) in, the target image of described Computer display is 1/8th sizes of the target image that test module photographs.
4. the method for testing evaluating module motor curve based on image MTF according to claim 2, it is characterized in that: the tangent value at motor angle of inclination is the ratio of the inclined height of motor and the actual physics distance at target image two angles, the inclined height of described motor can be multiplied with the motor displacement often run corresponding to a step by the difference of motor step number and to draw.
5. the method for testing evaluating module motor curve based on image MTF according to claim 1, is characterized in that: the brightness stability of described back light, the brightness uniformity of back light panel.
6. the method for testing evaluating module motor curve based on image MTF according to claim 1, is characterized in that: the size of described target and back light can be full of the whole target image of test module shooting.
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