JP3282868B2 - Resolution inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera, a video camera,
Projection television, telescopes, such as binoculars, it relates to a resolution inspection how to automate resolution inspection of the product having a lens barrel which is constituted by a lens.

[0002]

2. Description of the Related Art As one of conventional resolution inspection methods, there is a method as shown in FIG. In FIG. 7, reference numeral 21 denotes a lens barrel constituted by a zoom lens, and reference numeral 22 denotes a slide on which a resolution chart arranged on an image forming surface of the lens barrel 21 is drawn.
Reference numeral 23 denotes a light source for projecting the slide 22, and reference numeral 24 denotes a screen that projects a resolution chart drawn on the slide 22.

[0003] An operator 25 first sets the lens barrel 21 to be inspected in front of the slide 22 and reads the resolution pattern projected on the screen 24 with the zoom lens of the lens barrel 21 at the telephoto end. Identify how many black and white stripes appear to be separated. Next, by changing the zoom lens of the lens barrel 21 to the wide end, the resolution chart 22 is projected on the screen 24 to identify how many black and white stripes appear to be separated in the same manner as described above.

[0004] For example, 1 mm per mm at the telephoto end and the wide end.
When more than 00 black and white stripes appear to be separated,
1 is determined to be good.

As another conventional resolution inspection method,
There is a method as shown in FIG. In FIG. 8, reference numeral 26 denotes an image sensor mounted on the imaging surface of the lens barrel 21, reference numeral 27 denotes an image sensor control unit for controlling the image sensor 26 and outputting a video signal, reference numeral 28 a resolution chart, and reference numeral 29 a monitor for displaying a video signal. TV.

[0006] The resolution chart 28 is imaged by the image sensor 26 through the lens barrel 21 and the image sensor control unit 2
The video signal is converted into a video signal at 7 and displayed on the monitor television 29. The operator 25 observes the resolution pattern reflected on the monitor TV 29, and can determine how many black and white stripes are visible with respect to the vertical angle of view. It is read whether it is a book or not, and if it can be seen, for example, 300 TV books or more both vertically and horizontally, it is determined to be good.

[0007]

However, in the above-mentioned conventional resolution inspection method, there is a problem that the limit of the resolution is largely determined by the sensuality of the operator and the inspection standard is not constant. Further, in the case of a video camera, the resolution when the image is displayed on a monitor television may be reduced depending on the mounting state of the image pickup device, and the conventional example shown in FIG. In addition, in the conventional example of FIG. 8, the inspection can be performed in a state where the image pickup device is assembled. However, since resolution inspection is required at least at the tele end and the wide end of the zoom, two types of resolution charts are required, one for the tele end and the other for the wide end. Becomes
In addition, there is a problem that one of the lens barrel and the resolution chart needs to be moved to adjust the angle of view, and there is a problem that automatic inspection cannot be performed.

[0008] The present invention is the light of the conventional problems, and an object thereof is to provide a resolution test how capable of automatic inspection resolution of the imaging device with the barrel in the absence of variations in the determination.

[0009]

According to the resolution inspection method of the present invention, an image pickup device is mounted on an image forming surface of a lens barrel, and a resolution chart in which black and white stripes lower than the limit resolution are drawn is picked up and obtained from the image pickup device. A resolution inspection method that determines the degree of modulation by determining the modulation factor from the amplitude of the video signal and comparing it with a preset reference value
Video signal obtained by imaging the resolution chart.
Is divided into strip sections with a width larger than the cycle of
Find the maximum and minimum for each section and then at least average
To obtain the modulation degree of the entire strip section through statistical processing of
Features.

[0010]

In the above arrangement of the present invention, the amplitude, which is the difference between the black and white densities of a video signal obtained by imaging a resolution chart in which black and white stripes lower than the limit resolution are drawn, increases as the resolution increases. However, a fixed resolution cannot be evaluated based on the illuminance of the resolution chart or the sensitivity difference of each image sensor with the amplitude alone.Therefore, the value obtained by dividing the density difference between the black and white stripes by the density difference between the white and black areas near the black and white stripes is the modulation factor. The value is compared with the modulation degree of a preliminarily selected limit sample, and when the modulation degree is high, it is determined as a good product. The density difference between black and white stripes is
Finding the maximum and minimum and averaging the noise and noise of the image sensor
Eliminates the effects of shading on lenses and the like.

Preferably, there is a difference in the resolution between the center and the periphery of the imaging field of view. Therefore, for example, the modulation degree is obtained for each of the four corners and the center, and the comparison is made with the reference. Also,
By giving the resolution chart black-and-white stripes that match both the telescopic and wide-angle angles of view of the zoom mechanism in the lens barrel, the degree of modulation on both the telephoto and wide-angle sides is determined, and the quality is compared with the reference. judge.

In the resolution inspection, if the high-frequency component is maximized as in a normal focusing method, the accuracy is poor. Therefore, the focus function of the lens barrel is adjusted to the position where the resolution becomes highest.

Also, the reference chart is used to move the resolution chart or the lens barrel by the position control means so that the reference position of the resolution chart is at a specific position in the field of view of the image so that the same position of the resolution chart is imaged. Let it.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a resolution inspection apparatus according to one embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a lens barrel for a video camera having a focus motor and a zoom motor, and 2 denotes an image sensor. Reference numeral 3 denotes a pallet for holding the lens barrel 1, and reference numeral 4 denotes a conveyor for conveying the pallet 3. Reference numeral 5 denotes a setting device for setting the position of the pallet 3. Reference numeral 6 denotes a contact pin for extracting an image sensor control signal from the pallet 3, and reference numeral 7 denotes an image sensor control unit that supplies a drive signal to the image sensor 2, amplifies an electric signal from the image sensor 2, and outputs the amplified signal as a video signal. Reference numeral 8 denotes an image processing device that performs digital signal processing on a video signal. Reference numeral 9 denotes a sequencer that conveys and regulates the pallet 3 on the conveyor 4, and reference numeral 10 denotes a writer that writes a pass / fail judgment result to an ID card 11 provided on the pallet 3.

Reference numeral 12 denotes a resolution chart, 13 denotes a horizontal drive motor that drives the resolution chart 12 in the horizontal direction, and 14 denotes a vertical drive motor that drives the resolution chart 12 vertically. As shown in FIG. 2, the resolution chart 12 has a configuration in which a wide-end resolution chart 15a and a tele-end resolution chart 15b of the zoom mechanism are drawn on the same sheet.

FIG. 3 shows a position control method of the resolution chart 12, in which a reference position mark 16 is provided on the resolution chart 12, and the horizontal drive motor 13 and the vertical drive The resolution chart 12 is configured to be moved by a motor 14.

Next, the operation of the resolution inspection will be described.

The lens barrel 1 to be inspected is placed on a pallet 3 and conveyed on a conveyor 4. Sequencer 9
Detects the arrival of the pallet 3 and positions the pallet 3 by the setting device 5. The video signal of the resolution chart 12 captured by the image sensor 2 through the lens barrel 1 is collected by the contact pins 6, converted into a video signal by the image sensor control unit 7, and sent to the image processing device 8.

The image processing device 8 rotates the zoom motor to adjust the lens barrel 1 to the telephoto end, and further controls the focus motor of the lens barrel 1 so that the rising of the video signal for black and white displacement becomes steep. Focus.

Next, as shown in FIG. 3, the reference position mark 16 is picked up by the image sensor 2 and its position is recognized by the image processing device 8, and the horizontal drive is performed so that the reference position mark 16 is at a fixed position. A correction amount is given to the motor 13 and the vertical drive motor 14 to move and position the resolution chart 12.

Since the lens barrel 1 is zoomed to the telephoto end, the telephoto end resolution chart 15b in FIG. 2 is imaged in a fixed positional relationship. The image processing device 8 inspects the resolution of each of the center and the four corners from the video signal.

FIG. 4 shows the lower left portion of the resolution chart 15b. The density change of the portion where the black and white stripes lower than the limit resolution are drawn is obtained by the resolution evaluation line 17a. Further, the average density of the white portion and the black portion in the vicinity of the black and white stripe is obtained by the white reference line 17b and the black reference line 17c, respectively.

In FIG. 5, the horizontal axis represents the relative position of the image, and the vertical axis represents the density. 18a is a resolution evaluation line 17
18B is a waveform showing the density distribution of the white reference line 17b, and 18c is a waveform showing the density distribution of the white reference line 17b.
7C is a waveform showing the density distribution of FIG. 7C. Resolution evaluation line 1
The amplitude of the density distribution waveform 18a at 7a is ΔV, the average density at the white reference line 17b and the black
Assuming that the difference from the average density at c is ΔR, the degree of modulation is
It can be expressed by equation (1).

Modulation degree = (ΔV / ΔR) × 100 [%]
(1) Then, the focus motor is controlled so that the modulation degree becomes the highest at the center of the resolution chart 15b of FIG. 2 and finally high-precision focusing is performed, and then the modulation degree at the center and the modulation degree at the four corners are performed. Respectively. If the degree of modulation is equal to or greater than the degree of modulation of the lens barrel 1 at the non-defective limit, the lens barrel 1 at the telephoto end is determined to be non-defective.

Next, the zoom motor is turned to adjust the lens barrel 1 to the wide end. Since the optical axis of the lens barrel 1 and the center of the image sensor 2 do not always coincide with each other, the resolution chart 12 is moved and aligned even at the wide end, and then the focus is set so that the degree of modulation is maximized similarly to the tele end. Control the motor. Then, the degree of modulation is calculated for the center and the four corners,
The pass / fail judgment is made by comparing with the modulation degree of the non-defective product limit.

When both the telephoto end and the wide end are non-defective, it is determined as an overall non-defective product, and the result is sent from the image processing device 8 to the sequencer 9.

The sequencer 9 transmits the judgment result to the ID card 11
After the pallet 3 is written through the writer 10, the position of the pallet 3 is released. The pallet 3 on which the non-defective signal is not written on the ID card 11 passes the next process and is recovered as a defect.

The above is the overall operation of the resolution inspection. The density distribution on the resolution evaluation line 17a is shown in FIG.
As shown in FIG. 5, the concentration distribution may have a direct current component. Therefore, in order to remove the influence of the shading when obtaining the degree of modulation, as shown in FIG. 6, the density distribution of the resolution evaluation line 17a is divided into strip-shaped sections 19 having a width ΔT larger than the period of the black and white stripes. Find the maximum and minimum respectively. Then, the average of the difference between the maximum value and the minimum value in each section 19 is taken as ΔV in the equation (1).

In the above embodiment, only the horizontal resolution evaluation lines are shown. However, horizontal black and white stripes can be provided so that the vertical resolution evaluation can be performed.

Further, it is possible to simultaneously perform the zoom tracking inspection for tracking the reference position mark 16 during the zooming and checking whether the image is shaken.

[0032]

According to the present invention, since the resolution inspection is determined by the modulation factor, which is a quantitative evaluation scale, as described above, the accuracy of the determination boundary is higher than in the conventional method that relies on the sensuality of the operator. In addition, since the resolution inspection is performed in a state where the image pickup device is assembled, it is possible to inspect the shipping state of the product. In addition, in the resolution inspection of the lens barrel alone,
Although it was necessary to inspect with an excessive quality standard in consideration of the image sensor assembly accuracy, the resolution inspection after the image sensor assembly can be regarded as a non-defective product if the standard is passed as a whole, and the yield is high. There is an advantage that is improved.

When the modulation degree is obtained, the waveform indicating the density distribution of the resolution evaluation line is divided into strip-shaped sections, and the maximum and minimum are obtained for each section and statistical processing is performed. By eliminating the influence of shading or the like, a high-accuracy modulation degree can be obtained, and the accuracy of the determination boundary in the resolution inspection is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a resolution inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a front view of a resolution chart according to the embodiment.

FIG. 3 is a front view of a position control unit of the resolution chart in the embodiment.

FIG. 4 is a diagram showing black-and-white stripes and white and black reference areas in the embodiment.

FIG. 5 is a density distribution diagram of each evaluation line in FIG. 4;

FIG. 6 is an explanatory diagram showing a state in which a waveform of a resolution evaluation line is divided into strip sections.

FIG. 7 is an explanatory diagram of a conventional resolution inspection method.

FIG. 8 is a perspective view of another conventional resolution inspection apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lens barrel 2 imaging element 8 image processing device 12 resolution chart 13 horizontal drive motor 14 vertical drive motor 16 reference position mark 17a resolution evaluation line 17b white reference line 17c black reference line 19 strip-shaped section

Continuation of the front page (56) References JP-A-58-156828 (JP, A) JP-A-4-329097 (JP, A) JP-A-5-18862 (JP, A) JP-A-61-253440 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01M 11/00-11/08 H04N 17/00-17/06

Claims (1)

(57) [Claims] An imaging device is mounted on an image forming surface of a lens barrel, a resolution chart in which black and white stripes lower than a limit resolution are drawn is taken, a modulation degree is obtained from an amplitude of a video signal obtained from the imaging device, and preset. compared to the reference value a solution <br/> Zodo inspecting how to determine acceptability, resulting et al by imaging a resolution chart
Video signal into a strip section wider than the period of the black and white stripes.
Divide and find the maximum and minimum for each section, then at least
Through the statistical processing such as averaging, etc.
A resolution inspection method characterized by being obtained.