WO2017142154A1

WO2017142154A1 - Photographing apparatus and photographing method

Info

Publication number: WO2017142154A1
Application number: PCT/KR2016/010138
Authority: WO
Inventors: 허진
Original assignee: (주)이오테크닉스
Priority date: 2016-02-16
Filing date: 2016-09-09
Publication date: 2017-08-24
Also published as: KR101850363B1; TW201730658A; TWI618971B; KR20170096456A

Abstract

A photographing apparatus is disclosed. The disclosed photographing apparatus comprises: a light source for irradiating light; a focusing optical system for changing a path of light reflected from an object; a photographing unit for photographing an image of the object formed by the focusing optical system; and a distance adjusting unit for adjusting a distance between the focusing optical system and the object. The photographing unit photographs the image of the object every time the distance between the focusing optical system and the object changes by a predetermined distance, wherein the predetermined distance is set to be smaller than a depth of field of the focusing optical system.

Description

Recording device and shooting method

The present invention relates to a photographing apparatus and a photographing method, and to an auto focusing technique of a photographing apparatus.

In the laser processing process, it is important to clearly photograph the surface of the object. In order to increase the sharpness of the image, it is necessary to change the focusing position of the focusing optical system according to the object, which is called auto focusing.

Auto focusing is a process of finding the distance point at which a clear image is made while changing the distance between the focusing optics and the object. That is, in the auto focusing process, a plurality of photographing operations are required while varying the distance between the focusing optical system and the object.

By the way, conventionally, image capturing was performed in a stationary state in order to obtain an image without shaking for each of a plurality of photographing operations. However, in this case, since the delay time required to wait for the vibration of the machine is consumed, it becomes difficult to perform auto focusing at high speed. In addition, when performing an auto focusing operation in a moving state, it is difficult to find an accurate focusing position as the sharpness of an image is reduced.

According to the exemplary embodiment, the auto focusing operation of the photographing apparatus can be performed accurately and quickly.

In one aspect,

A light source for irradiating light;

A focusing optical system for changing a path of the light reflected from the object;

A photographing unit which photographs an image of the object formed by the focusing optical system; And

And a distance controller configured to adjust a distance between the focusing optical system and the object.

The photographing unit captures an image of the object whenever the distance between the focusing optical system and the object is changed by a predetermined interval, wherein the predetermined interval is set smaller than a depth of field of the focusing optical system. An imaging device is provided.

According to the embodiment, the photographing apparatus may perform the auto focusing operation while the distance between the object and the focusing optical system is changed. Therefore, the photographing apparatus can shorten the time required for auto focusing.

In addition, the photographing apparatus can obtain a clear image even if the auto focusing is made dynamically. The photographing apparatus may allow at least one image photographed in the dynamic auto focusing process to be photographed in a depth range of the focusing optical system.

In addition, the photographing apparatus may improve the accuracy of the auto focusing operation by correcting the correct focusing distance from the sharpness values of the images.

1 is a diagram illustrating a photographing apparatus according to an exemplary embodiment.

2 is a diagram illustrating an image photographing point of a photographing unit in an auto focusing process.

3 is a diagram illustrating a range in which a distance between an object and a focusing optical system is changed by a distance controller.

4 is a diagram illustrating a change in speed at which a focusing point moves with time.

Fig. 5 is a view showing a photographing apparatus according to another exemplary embodiment.

6 is a diagram exemplarily illustrating an electrical signal generated by an encoder.

Fig. 7 is a view showing a photographing apparatus according to another exemplary embodiment.

8 is a diagram illustrating an example of a synchronization signal generated by a controller.

9 is a diagram illustrating a change in height of a focusing point with time.

10 is a graph showing the relationship between the height of the focusing point and the sharpness of the image.

11 is a diagram illustrating that the processor corrects an auto focusing distance.

12 is a flowchart illustrating a photographing method according to an exemplary embodiment.

Fig. 13 is a flowchart illustrating a photographing method according to another exemplary embodiment.

Fig. 14 is a flowchart showing a photographing method according to another exemplary embodiment.

In one aspect,

A light source for irradiating light;

The photographing unit may photograph an image of the object by a global shutter method.

The distance adjusting unit may change the distance between the object and the focusing optical system at at least one section at constant speed.

The speed at which the distance controller changes the distance between the object and the focusing optical system may satisfy Equation 1.

.... Equation 1

(V1 = size of the distance change speed between the object and the focusing optics, f = number of shots per hour in the constant velocity section, DOF = depth of the focusing optics)

The speed at which the distance controller changes the distance between the object and the focusing optical system may satisfy Equation 2.

V1 <DOF / E ......... Equation 2

(V1 = magnitude of the speed of change of distance between the object and the focusing optical system, DOF = depth of focusing optical system, E = exposure time per frame of the photographing unit)

The exposure time per frame of the photographing unit may satisfy Equation 3.

......... Equation 3

(E = exposure time per frame of the imager, A _pixel = pixel area of the imager, M = magnification, V2 _max = maximum value of the relative vibration speed between the imager and the object)

The photographing apparatus may further include an encoder configured to generate an electrical signal by detecting a change in distance between the object and the photographing unit.

The photographing apparatus may further include a controller configured to generate a synchronization signal for the photographing unit based on the electrical signal generated by the encoder.

The photographing apparatus may further include a processor configured to receive images of the object photographed by the photographing unit and extract clarity of the images.

The processor may determine, as a focusing distance, a distance between the object on which the sharpest image is captured and the focusing optical system.

The processor may determine a focusing distance according to Equation 4 from the sharpness values of the images.

.... Equation 4

(H = distance between the focusing optics and the object in the focusing state, H _i = distance between the focusing optics and the object in the i-th shot with the highest sharpness measured, H _i-1 = focusing optics in the i-1th shot) Distance between the object and H _{i + 1} = distance between the focusing optics and the object in the i + 1th shot, C _i = sharpness value of the i-th image measured with the highest sharpness, C _i _-1 = i- Sharpness value of the first shot image, C _i ₊₁ = Sharpness value of the i + 1th shot image)

An interval in which the distance controller changes the distance between the object and the focusing optical system may be determined by Equations 5 and 6 below.

H-D-δ <X <H + D + δ ....... Equation 5

..... Equation 6

(X = distance between the object's support and the focusing point of the focusing optics, H = expected thickness of the object, D = thickness deviation of the object, δ = acceleration interval, V1 = maximum velocity, a = acceleration)

In another aspect,

Irradiating light onto the object;

Focusing light reflected from the object using a focusing optical system;

Adjusting a distance between the focusing optics and the object; And

Photographing an image of the object whenever the distance between the focusing optical system and the object is changed by a predetermined interval;

The predetermined method is provided in which the predetermined interval is set smaller than the depth of the focusing optical system.

The adjusting of the distance may change the distance between the object and the focusing optical system at a constant speed in at least one section.

In the adjusting of the distance, the photographing unit captures an image of the object at a predetermined time interval in a section in which the distance between the object and the focusing optical system is changed at a constant speed.

The speed at which the distance between the object and the focusing optical system changes may satisfy Equation 1.

.... Equation 1

(V1 = magnitude of the speed of change of distance between the object and the focusing optical system, f = number of shots per hour in the constant velocity section, DoF = depth of focusing optical system, and α is any real number satisfying 0.1 <α <0.5)

In the adjusting of the distance, a speed of changing the distance between the object and the focusing optical system may satisfy Equation 2.

V1 <DOF / E ......... Equation 2

The photographing method may further include generating an electrical signal by detecting a change in distance between the object and the photographing unit.

The photographing method may further include generating a synchronization signal for the photographing unit based on the electrical signal.

The photographing method may further include extracting sharpness of the images by receiving images of the object photographed by the photographing unit.

The photographing method may further include determining a focusing distance according to Equation 3 from the sharpness values of the images.

.... Equation 3

In the drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of description. Meanwhile, the embodiments described below are merely exemplary, and various modifications are possible from these embodiments.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are only used to distinguish one component from another.

Singular expressions include plural expressions unless the context clearly indicates otherwise. In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

In addition, terms such as “unit” and “module” described in the specification mean a unit that processes at least one function or operation.

1 is a diagram illustrating a photographing apparatus 100 according to an exemplary embodiment.

Referring to FIG. 1, the photographing apparatus 100 according to an exemplary embodiment includes a light source 110, a focusing optical system 120 for changing a path of light reflected from an object 10, and a focusing optical system 120. It may include a photographing unit 140 for capturing the image of the formed object 10 and the distance adjusting unit 130 for adjusting the distance between the focusing optical system 120 and the object 10.

The light source 110 may radiate light. Light emitted from the light source 110 may be irradiated to the object 10 through a predetermined optical system. 1 illustrates an example in which the light emitted from the light source 110 proceeds as parallel light. For example, a beam expander and a beam splitter may be provided on the front surface of the light source 110. The light emitted from the light source 110 may travel in parallel light by expanding a beam diameter in a beam expander. The traveling parallel light may be directed to the focusing optical system 120 by reflecting an optical path from the beam splitter. However, the embodiment is not limited thereto, and the optical system through which the light emitted from the light source 110 passes may be configured differently. In addition, the light emitted from the light source 110 may be directly irradiated to the object 10 without passing through the optical system.

The focusing optical system 120 may change the path of the light reflected from the object 10. The light whose path is changed by the focusing optical system 120 may be incident on the image sensor of the photographing unit 140. In FIG. 1, the focusing optical system 120 is expressed separately from the photographing unit 140, but the embodiment is not limited thereto. The focusing optical system 120 may be included in the photographing unit 140. In this case, the distance adjusting unit 130 may change the distance between the focusing optical system 120 and the object 10 by moving the photographing unit 140. The focusing optical system 120 may have a predetermined focusing distance. Therefore, when the focusing optical system 120 and the surface of the object 10 maintain an appropriate distance, the photographing unit 140 may acquire a clear image of the object 10. The focusing optical system 120 may include, for example, a lens having positive refractive power.

The object 10 may include a wafer, a semiconductor chip, etc. as an object to be photographed, but is not limited thereto. The object 10 may not have a constant thickness due to the roughness of the surface. In addition, the distance between the surface of the object 10 and the focusing optical system 120 may not be constant depending on the flatness of the support surface S1 supporting the object 10. Therefore, in order for the photographing apparatus 100 to obtain an image of the object 10 clearly, the distance between the object 10 and the focusing optical system 120 should be appropriately adjusted. The process in which the photographing apparatus 100 adjusts the distance between the focusing optical system 120 and the object 10 to obtain an image of the object 10 clearly is called an auto focusing process.

The distance adjuster 130 may change the distance between the object 10 and the focusing optical system 120 in the auto focusing process. The distance adjuster 130 may move the support surface S1 on which the object 10 is seated. As another example, the distance adjusting unit 130 may move the focusing optical system 120. When the focusing optical system 120 is embedded in the photographing unit 140, the distance adjusting unit 130 may move the photographing unit 140. In addition, the distance adjusting unit 130 may change the distance between the focusing optical system 120 and the object 10 by simultaneously moving the focusing optical system 120 and the support surface S1.

In order to change the distance between the object 10 and the focusing optical system 120, the distance adjusting unit 130 includes a moving object having a large mass including the focusing optical system 120, the photographing unit 140, and the support surface S1. I can move it. The moving body may mean a focusing optical system 120, a photographing unit 140, a support surface S1, and the like, in which the distance controller 130 moves for auto focusing. While the distance adjuster 130 accelerates and decelerates the moving body, vibration due to inertial force may occur. For example, in a situation in which the photographing apparatus 100 photographs the semiconductor object 10, the photographing unit 140 may increase in mass due to equipment attached to the photographing unit 140 to increase the mass of the moving object. At this time, when the distance adjuster 130 accelerates and decelerates the photographing unit 140, the photographing unit 140 may generate vibration due to inertial force.

According to a comparative example, the image photographing of the object 10 may be performed in a state in which the distance between the focusing optical system 120 and the object 10 does not change. For example, after moving the focusing optical system 120 to a predetermined position, the image of the object 10 may be captured while the focusing optical system 120 is stopped. In this case, in order to obtain a clear image, the photographing unit 140 must wait for several tens to hundreds of ms until the focusing optical system 120 moves and stops, and the vibration caused by the acceleration / deceleration disappears before taking the image.

For example, if the vibration velocity vector is (vx, vy, vz) when shooting at an optimal focal length with a lens system with a magnification M and a camera with pixel width and height sizes px and py, respectively, vx * E <px / M And vy * E <py * M and vz * E <DOF can be obtained to obtain a clear image. Here, E denotes the exposure time of the photographing unit 140, DOF means the depth of field (DOF) of the focusing optical system 120, which will be described in detail later.

However, the method according to the comparative example described above may be disadvantageous for high speed photography. In order to find the correct focusing position, it is necessary to compare the sharpness of the images obtained by variously changing the distance between the focusing optical system 120 and the object 10. However, each time the image is acquired, the vibration due to the acceleration and deceleration is reduced, so that waiting time may be required until vx * E <px / M and vy * E <py * M and vz * E <DOF are satisfied. In addition, the auto focusing process may be lengthened due to the waiting time. For example, if the mass of the moving object is more than 30 kg, a waiting time of 400 ms or more may be required every time an image is taken. If so, the delay time required to acquire an image after ten movements and stops may take four seconds or more. This delay time becomes a factor that makes high speed photography difficult.

For faster auto focusing, according to an exemplary embodiment, the photographing unit 140 may capture an image of the object 10 while the distance between the focusing optical system 120 and the object 10 is changed. That is, while at least one of the object 10 and the focusing optical system 120 is not stopped, the photographing unit 140 may capture an image of the object 10. Therefore, after stopping the moving body, it is not necessary to wait for the vibration due to acceleration / deceleration to disappear, so that the time required for auto focusing can be shortened.

The photographing unit 140 may photograph the object 10 by using a global shutter method. Here, the global shutter method refers to a method of obtaining an image by exposing all pixels simultaneously. In contrast, a rolling shutter method obtains an image for one line or a group of pixels and obtains an image with parallax for the remaining pixels. When the photographing unit 140 photographs the object 10 by the global shutter method, a clear image may be obtained despite the external vibration.

As the distance between the object 10 and the focusing optical system 120 changes, the sharpness of the image photographed by the photographing unit 140 may vary. When the sharpness of the image photographed by the photographing unit 140 becomes the maximum, the distance between the object 10 and the focusing optical system 120 may be referred to as a focal length. Even if the distance between the object 10 and the focusing optical system 120 does not perfectly match the focal length, a great change may not occur in the sharpness of the image captured by the photographing unit 140. That is, even if the distance between the object 10 and the focusing optical system 120 changes within a predetermined region near the focal length, there may be no significant effect on the sharpness of the image. The area in which the sharpness of the image is maintained is referred to as a depth of field (DOF) of the focusing optical system 120.

In the auto focusing process, the distance between the focusing optical system 120 and the object 10 may be adjusted into a depth of field (DOF) of the focusing optical system 120. However, if the photographing unit 140 captures an image while the distance between the object 10 and the focusing optical system 120 is changed, when the focusing point is within the depth of field, the image may not be photographed. Therefore, a high sharpness image cannot be obtained during auto focusing, and thus it may be difficult to find the correct auto focusing position. In order to solve the above problem, the photographing unit 140 may photograph an image of the object 10 whenever the distance between the light converging optical system 120 and the object 10 changes by a predetermined interval. In addition, the predetermined interval may be set smaller than the depth of field (DOF) of the focusing optical system (120).

2 is a diagram illustrating an image capturing point of the photographing unit 140 in an auto focusing process. In FIG. 2, the focusing optical system 120 is moved by way of example, but the embodiment is not limited thereto. For example, the distance between the focusing optical system 120 and the object 10 may change as the support surface S1 of the object 10 moves.

Referring to FIG. 2, the photographing unit 140 may photograph an image of the object 10 whenever the distance between the focusing optical system 120 and the object 10 changes by a predetermined interval Δh. The predetermined interval Δh may be set smaller than the size of the depth DOF of the focusing optical system 120. The predetermined interval Δh may be kept constant during the autofocusing process or may change little by little. However, even if the predetermined interval Δh is changed, the size may be smaller than the size of the depth DOF of the focusing optical system 120. Therefore, even when photographing is performed while the distance between the object 10 and the focusing optical system 120 is changed, at least one photographing may be performed in the depth of field.

In order to speed up the auto focusing operation, the distance adjusting unit 130 may change the distance between the object 10 and the focusing optical system 120 within a predetermined range. 3 is a diagram illustrating a range in which the distance between the object 10 and the focusing optical system 120 is changed by the distance adjuster 130.

Referring to FIG. 3, the distance controller 130 may cause the focusing point P of the focusing optical system 120 to move within a predetermined area. The distance adjuster 130 moves the focusing point P of the focusing optical system 120 about a point L2 away from the surface L1 of the supporting surface S1 by an expected height H of the object 10. can do. For example, the distance controller 130 may allow the focusing point P of the focusing optical system 120 to move while satisfying Equation 1.

Here, X = distance between the support surface of the object and the focusing point of the focusing optical system, H = the expected thickness of the object, D = thickness deviation of the object, δ = acceleration interval.

4 is a diagram illustrating a change in the speed at which the focusing point P moves with time. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the relative speed between the focusing optical system 120 and the object 10 (the speed at which the focusing point P moves).

Referring to FIG. 4, the relative speed between the focusing optical system 120 and the object 10 may gradually increase until time t1. At this time, the relative speed may increase with a constant acceleration (a). The acceleration section is a section in which the distance controller 130 accelerates at least one of the focusing optical system 120 and the object 10.

For example, while the time varies from t0 to t1, the focusing point P of the focusing optics 120 may move from the height H-D-δ to the height H-D from the surface L1 of the support surface S1. The moving distance δ during the acceleration period can be represented by Equation 2.

In Equation 2, δ represents the magnitude of the distance traveled during the acceleration time, a is the magnitude of the acceleration, V is the terminal velocity by the acceleration, that is, the magnitude of the maximum velocity.

From time t1 to time t2, the relative speed between the focusing optical system 120 and the object 10 may be maintained at a constant size V1. For example, while the time varies from t1 to t2, the focusing point P of the focusing optics 120 may move from the height H-D to the height H + D from the surface L1 of the support surface S1. In addition, from time t2 to time t3, the relative speed between the focusing optical system 120 and the object 10 may gradually decrease. At this time, for example, the relative speed may be gradually reduced to a constant acceleration -a. Further, while the time varies from t2 to t3, the focusing point P of the focusing optics 120 can move from the height H + D to the height H + D + δ from the surface L1 of the support surface S1. By setting the moving range of the focusing point P in consideration of the expected height H and the thickness deviation D of the object 10, the distance adjusting unit 130 may find the focusing distance faster and more accurate. .

While the focusing point P moves from the height L-D to the height H + D from the surface L1 of the supporting surface S1, the photographing unit 140 may photograph an image of the object 10 a plurality of times. In this case, the focusing point P may move at a constant speed, and the magnitude V1 of the moving speed may depend on the exposure time of the photographing unit 140. Here, the exposure time means a time when the photographing unit 140 is exposed to light in order to obtain an image in one shot. The exposure time may be adjusted by the time for which the light source 110 irradiates light. As another example, the exposure time may be adjusted by a shutter or an aperture inside the photographing unit 140.

The speed at which the focusing point P moves (the magnitude of the speed of change in distance between the object 10 and the focusing optical system 120; V1) may satisfy Equation 3 below.

In Equation 3, V1 = size of the speed of change of distance between the object and the focusing optical system, DOF = depth of field (DOF) of the photographing unit, and E = exposure time per frame of the photographing unit. Also, α is a real number satisfying 0 <α <1 and may vary depending on the optical performance of the photographing unit 140.

If the focusing point P moves too quickly, the focusing point P may move out of the depth DOF while the photographing unit 140 captures one frame. Therefore, as in Equation 3, by limiting the speed at which the focusing point P moves, it is possible to prevent the focusing point P from moving out of the depth DOF during the exposure time required for photographing.

Even when the distance between the focusing optical system 120 and the object 10 is moved at a constant speed in the auto focusing process, minute vibration may occur in a direction perpendicular to the distance direction between the focusing optical system 120 and the object 10. Therefore, when the exposure time per frame of the photographing unit 140 is too long, the sharpness of the image may be reduced by the vibration between the focusing optical system 120 and the object 10. In order to prevent the sharpness of the image from deteriorating, a movement between the focusing optical system 120 and the object 10 should occur within a 1 pixel range of the photographing unit 140 during the exposure time per frame. To satisfy this, the exposure time per frame of the photographing unit 140 may satisfy Equation 4.

In Equation 4, E = exposure time per frame of the photographing unit 140, A _pixel = pixel area of the photographing unit 140, M = magnification, V2 _max = relative between the photographing unit 140 and the object 10. The maximum value of the vibration speed is shown.

As shown in Equation 4, by limiting the exposure time (E) of the photographing unit 140, it is possible to prevent the sharpness of the image is lowered by the horizontal vibration between the photographing unit 140 and the object 10. . For example, in the case of wafer photographing in a conventional wafer grooving process, a field of view (FOV) of the photographing unit 140 is required to be 240um x 180um to 480um x 360um and the optical resolution is 1.2um or less. May be required. Assuming that the maximum vibration velocity (V2 _max ) between the photographing unit 140 and the object 10 is 0.2 mm / s, it is within about 2ms from Equation 4 in an environment of a pixel size of 4.8um x 3.6um and a magnification of 10 times. Exposure time may be required. In addition, the output power of the light source 110 required to obtain an image may vary according to the exposure time E. FIG. For example, the light output power required for the light source 110 may increase as the exposure time E per frame of the photographing unit 140 decreases. For example, if the exposure time is about 2ms for the field of view (FOV) 480um x 360um, the minimum output power required for the light source 110 may be about 0.2W.

While the focusing point P moves at a constant speed V1 from the surface L1 of the supporting surface S1 to the height H to the height H + D, the photographing unit 140 images the image of the object 10 at regular time intervals. You can shoot. By capturing an image of the object 10 at a predetermined time interval by the photographing unit 140, an image may be obtained whenever the focusing point P moves by a predetermined distance. In this case, the speed at which the focusing point P moves (relative speed between the object 10 and the focusing optical system 120; V1) and the number of times f taken by the photographing unit 140 may satisfy Equation 5.

In Equation 4, V1 = size of the speed of change of distance between the object 10 and the focusing optical system 120, f = number of shots per hour of the photographing unit 140 in the constant velocity section, DOF = depth of the focusing optical system 120 (DOF). Also, α is a real number satisfying 0 <α <1 and may vary depending on the optical performance of the photographing unit 140.

Referring to Equation 5, the product of the speed V1 of moving the focusing point P and the inverse of the number of shots f of the photographing unit 140 is larger than the depth DOF of the focusing optical system 120. Can be small. Therefore, even if the photographing is performed while the focusing point P is moving, at least one photographing may be performed when the focusing point P is located in the depth of field (DOF) of the focusing optical system 120. In addition, a focusing distance may be derived from a clear image captured in a depth of field.

For example, in the case of an imaging apparatus used in conventional wafer grooving, the DOF value may be within about 10 μm <DOF <20 μm. And, for more accurate imaging, the DOF * α value may be required within about 5μm. Therefore, V1 / f <5um may be satisfied from Equation 5. For example, V1 <= 0.2 mm / s for f = 40 Hz and V1 <= 0.4 mm / s for f = 80 Hz. The above figures are merely exemplary and may vary depending on the working environment.

When the focusing point P is located in the depth of field DOF of the focusing optical system 120, a clear image may be obtained. The photographing apparatus 100 according to the embodiment may determine that auto focusing is performed when the clear image is obtained. Referring back to FIG. 1, the photographing apparatus 100 may include a processor 160 for evaluating the sharpness of the images photographed by the photographing unit 140. The processor 160 may exchange information with the photographing unit 140 by wireless or wired communication.

The processor 160 of FIG. 1 may receive image information photographed by the photographing unit 140. In addition, the processor 160 may transmit operation setting information of the photographing unit 140 to the photographing unit 140. The photographing unit 140 may receive operation setting information from the processor 160 to change an operation method of the photographing unit 140. For example, the processor 160 may transmit setting information about the exposure time E per frame, the number of shots per hour f, etc. to the photographing unit 140. In addition, the photographing unit 140 may receive the setting information and change the exposure time E per frame and the number of photographing times f per time according to the setting information. In addition, the processor 160 may automatically determine the setting information of the photographing unit 140 from Equation 1 to Equation 5 above. However, the embodiment is not limited thereto. For example, the processor 160 may receive setting information of the photographing unit 140 from a user. To this end, the processor 160 may provide an input interface for receiving setting information. The input interface may be provided by a button method or a touch screen method.

The processor 160 may include an application program for performing the above-described functions, and, in some cases, various databases (DBs) (hereinafter, referred to as "DBs") built in or outside. The DB may be implemented inside or outside the processor 160.

As shown in FIG. 3, while the focusing point P moves from the height L to the height H + D from the surface L1 of the support surface S1, the photographing unit 140 processes the images photographed a plurality of times. And transmit to 160. The processor 160 may evaluate the sharpness of the images received from the photographing unit 140. For example, the processor 160 may evaluate the sharpness of each image and convert it into a score.

Here, the sharpness of the image may be an evaluation amount determined according to the degree of defocusing when the image is captured. For example, an image photographed while the focusing point P deviates from the depth of focus (DOF) of the focusing optical system 120 is photographed while the defocusing degree is severe. In addition, since the image photographed in a state where the degree of defocusing is severe may include a relatively blurry portion, the sharpness may be low. On the other hand, when the focusing point P is located in or near the depth of field, the photographed image is taken at a relatively low defocusing degree. In addition, the image photographed in a state where the defocusing degree is low may be evaluated as having high sharpness as it includes fewer blurry portions.

In exemplary embodiments, the processor 160 may evaluate the sharpness by analyzing the difference in contrast between pixels of the image. For example, as the blurring part of the image increases, the contrast difference between pixels may be reduced. Accordingly, the processor 160 may evaluate that the sharpness of the image is low when the contrast difference between pixels is not large. On the other hand, if the image is clear, a sharp change in contrast between pixels may increase. Therefore, the processor 160 may determine that the sharper the image is, the more the region having a large change amount of contrast between pixels of the image.

The processor 160 may determine an image having the highest sharpness among the images received from the photographing unit 140. When the image having the highest sharpness is captured, it may be determined that the distance between the object 10 and the focusing optical system 120 is close to the focusing distance. For example, the processor 160 may receive N images from the photographing unit 140 and evaluate the sharpness of the i-th image among them. Then, the processor 160 may conclude that the distance between the object 10 and the focusing optical system 120 is closest to the focusing distance when the i-th image is captured.

In order to find the correct focusing position from the sharpness of the images evaluated by the processor 160, the relative distance between the focusing optical system 120 and the object 10 should be known at the time when each image is captured. That is, each time the photographing unit 140 captures an image, a method of knowing the position of the focusing optical system 120 and the object 10 is required.

5 is a diagram illustrating a photographing apparatus 200 according to another exemplary embodiment.

Referring to FIG. 5, the photographing apparatus 200 according to an exemplary embodiment may further include an encoder 250 that detects a change in distance between the object 10 and the photographing unit 140 and generates an electrical signal. . The remaining components are described in the photographing apparatus 100 of FIG. 1, and thus redundant descriptions thereof will be omitted.

The encoder 250 may be linked with the distance adjuster 130. The encoder 250 may detect a state of the distance controller 130 and generate an electrical signal based on the state. For example, the encoder 250 may generate an electrical signal whenever the distance controller 130 changes the distance between the object 10 and the photographing unit 140 by a predetermined interval. As another example, the encoder 250 may generate a pulse signal by detecting an amount of change in distance between the object 10 and the focusing optical system 120 by itself.

6 is a diagram exemplarily illustrating an electrical signal generated by the encoder 250.

Referring to FIG. 6, the encoder 250 may generate a pulse signal whenever the distance between the object 10 and the focusing optical system 120 varies by a predetermined interval. The frequency at which the pulse signal is generated may vary depending on the depth of focus (DOF) of the focusing optical system 120. For example, the distance change amount when an i-th pulse is generated and when the i + 1 th pulse is generated may be set to be equal to or smaller than the size of the depth DOF of the focusing optical system 120. The distance at which the encoder 250 generates the pulse signal is set to be smaller than the depth of the depth of the focusing optical system 120. The positional change of the focusing point P between adjacent shots is set smaller than the depth of the depth. Can be.

6 illustrates a pulse signal as an example of an electrical signal generated by the encoder 250, but the embodiment is not limited thereto. For example, the encoder 250 may generate different kinds of electrical signals according to the distance between the object 10 and the focusing optical system 120. In this case, the processor 160 may include an algorithm therein for interpreting the electrical signal generated by the encoder 250.

The photographing unit 140 may be synchronized with the operation of the pulse signal of the encoder 250. For example, the photographing unit 140 may count the number of pulses of the pulse signal received from the encoder 250. In addition, the photographing unit 140 may photograph an image of the object 10 whenever the number of pulses increases by a predetermined number. In addition, the processor 160 may count the number of pulses of the pulse signal received from the encoder 250. In addition, the processor 160 may focus the optical system 120 and the object 10 at the time when the image with the highest sharpness is photographed from the number of pulses counted at the time when the image with the sharpest image is received from the photographing unit 140. You can see the distance between them.

7 is a view showing a photographing apparatus 300 according to another exemplary embodiment.

Referring to FIG. 7, the photographing apparatus 300 according to the embodiment may further include a controller 355 that generates a synchronization signal for the photographing unit 140 based on an electrical signal generated by the encoder 250. . The controller 355 may receive an electrical signal generated by the encoder 250. The controller 355 may generate a synchronization signal for the photographing unit 140 based on the electrical signal received from the encoder 250. The controller 355 may generate a synchronization signal whenever the distance between the focusing optical system 120 and the object 10 changes by a predetermined interval based on the electrical signal provided by the encoder 250. The photographing unit 140 may capture an image of the object 10 whenever the distance between the focusing optical system 120 and the object 10 changes by a predetermined interval by being synchronized by the synchronization signal. The predetermined interval may be set smaller than the depth of field (DOF) of the focusing optical system 120.

In addition, the processor 160 may receive the synchronization signal from the controller 355 to determine the distance between the object 10 and the focusing optical system 120 when the photographing unit 140 captures an image. In FIG. 7, the processor 160 and the controller 355 are shown as separate blocks. However, in FIG. 7, the two components are separately expressed according to functions, and the processor 160 and the controller 355 are not limited to hardware. For example, the processor 160 and the controller 355 may share the same hardware resource and perform their respective functions. In addition, the processor 160 and the controller 355 may be separated into different devices.

8 is a diagram exemplarily illustrating a synchronization signal generated by the controller 355. In FIG. 8, the upper graph shows a pulse signal generated by the encoder 250 and the lower graph shows a synchronization signal generated by the controller 355.

Referring to FIG. 8, the controller 355 may generate a pulse signal as a synchronization signal whenever the number of pulse signals received from the encoder 250 increases by a predetermined number. 8 illustrates an example in which the controller 355 generates a pulse signal whenever the number of pulse signals received by the encoder 155 changes by three. However, the embodiment is not limited thereto. For example, the number ratio between the pulse signal generated by the controller 355 and the pulse signal generated by the encoder 250 may be smaller or larger than that shown in FIG. 8.

The controller 355 may know the distance between the focusing optical system 120 and the object 10 based on the electrical signal received from the encoder 250. The controller 355 may control an operation method of the distance adjusting unit 130 based on the distance between the focusing optical system 120 and the object 10.

The controller 355 may control the distance controller 130 to move the focusing point P within a range satisfying Equation 1. In this case, values such as H, D, δ, and the like may be input by the input interface unit of the processor 160. The processor 160 may transmit the input setting values to the controller 355. The controller 355 may determine how the distance controller 130 operates by comparing the input values with the distance values obtained by the electrical signal received from the encoder 250.

For example, when the control unit 355 receives the start time HD-δ = 0.64mm, the end point H + D + δ = 0.96mm, and the constant velocity V1 = 0.2mm / s from the processor 160, the control unit ( 355 may transmit a control signal to the distance adjuster 130 such that the height of the focusing point P becomes a point HD-δ = 0.64mm. When the height of the focusing point P becomes H-D-δ = 0.64 mm, the controller 355 may transmit a movement end interrupt to the processor 160. In addition, when the controller 355 receives the autofocus focusing command from the processor 160, the height of the focusing point P is equivalent at the point HD-δ = 0.64mm based on the electrical signal received by the encoder 250. Acceleration speed after accelerating from speed 0 to speed V1 0.2mm / s at speed a (= V1 / Δt) 0.667mm / s2, moving from HD = 0.7mm to H + D = 0.9mm at speed V1 0.2mm / s Decrease to -a (= -0.667mm / s2) to stop at height H + D + δ = 0.96mm. In addition, the controller 355 may transmit a movement end interrupt to the processor 160. In addition, while the height of the focusing point P varies from a point H-D = 0. 7mm to H + D = 0. 9mm, the controller 355 may generate a pulse signal at intervals of 5um. In addition, the photographing unit 140 may capture the object 10 in synchronization with the pulse signal. The above figures are merely exemplary and may vary depending on the embodiment.

9 is a diagram illustrating a change in height of the focusing point P with time.

In FIG. 9, the vertical axis represents the height of the focusing point P, and the horizontal axis represents time. For the sake of convenience, the state in which autofocusing starts is shown as the origin.

The processor 160 may evaluate the sharpness of the N images received from the photographing unit 140. The processor 160 may determine an i-th image having the highest sharpness among the N images. In addition, the processor 160 may know the height H _{i at} which the i th image is taken from the signal received from the controller 355 or the encoder 250. Then, the focusing point (P) to the height (H _i) can be actuated.

Referring to FIG. 9, the focusing point P may accelerate from t ₀ to t ₁ . For example, the height of the focusing point P at time t ₀ may be ₀ on the graph but may actually be HD-δ shown in Equation (1). Also, the height of the focusing point P at time t ₁ may be HD. The time Δt required for the acceleration motion may vary depending on the magnitude V1 of the constant velocity and the acceleration a.

In the period t ₁ to t _N , the focusing point P may move at a constant speed. In the constant velocity section, the height of the focusing point P may vary from HD to H + D. Each time the focusing point P is moved by a predetermined interval Δh in the period in which the focusing point P is in constant motion, the photographing unit 140 may capture an image of the object 10. Since the predetermined interval Δh is set smaller than the depth of field DOF of the focusing optical system 120, at least one imaging may be performed in the depth of field DOF.

Since the photographing is performed at a constant distance interval in the constant velocity movement section, the photographing of the object 10 may be performed at a constant time interval (1 / f). The time taken by the photographing unit 140 to transmit the image data to the processor 160 may be smaller than the time interval 1 / f. In FIG. 9, t _i means the time at which the i-th image was taken in the constant velocity section. In addition, H _i means the height of the focusing point (P) when the i-th shooting is taken in the constant velocity section. After N shots are taken during the constant velocity section, the focusing point P may be decelerated. The focusing point P may stop at height H + D + δ.

10 is a graph showing the relationship between the height of the focusing point P and the sharpness of the image.

Referring to FIG. 10, the sharpness C _i at the i-th photographing height H _i may have the highest value. The processor 160 may determine the height H _i , at which the image having the maximum sharpness C _i value among the various sharpness values, is taken as the auto focusing distance. The determination of the auto focusing distance by the processor 160 is not limited thereto. For example, the processor 160 may further consider the contrast values C _i _-1, C _i ₊₁ in each adjacent _{_{H i-1, H i +}} 1 to the height H _i to correct the auto-focusing distance.

11 is a diagram illustrating that the processor 160 corrects an auto focusing distance.

Referring to FIG. 11, the processor 160 may calculate a height H _max at which an image of maximum sharpness C _max is obtained. As shown in FIG. 11, since the image of the object 10 is taken discontinuously with respect to the distance change, the image may not be taken at the height H _max having the highest sharpness of the image. However, since the interval between H _i-1 , H _i, H _{i + 1} is very narrow, the height of the focusing point P and the height of the focusing point P are changed while the height of the focusing point P is changed from H _i _-1 to H _{i +} ₁ . The relationship between the sharpness of an image can be approximated by a quadratic function. And, H _i-1 by the _{approximation,} H _{_i,} H _i ₊ ₁ and _{_{_{_{C i -1, C i, C}}}} i +1 can be expressed by equation (6) to Equation (9).

The height H _max for obtaining the image of the maximum sharpness C _max may be obtained as −b / 2a, which is the inflection point of the quadratic function shown in Equations 6 to 8. If the height H _max = -b / 2a is obtained from the equations (6) to (8), it can be expressed by the equation (9).

Processor 160 calculates the optimal focusing distance H _max from the sharpness _{_{_{C i -1, C i, C}}} i +1 and the equation (10) of the image obtained in each of the height _{_{H i-1, H i,}} H i + 1 The height H _max can be determined as the auto focusing distance. When the processor 160 determines the auto focusing distance H _max , the distance controller 130 may focus on the object 10 and the focusing optical system such that the distance between the focusing point P and the support surface of the object 10 becomes H _max. The distance between 120 can be changed.

In the above, the

imaging apparatuses

100, 200, and 300 according to the exemplary embodiments have been described with reference to FIGS. 1 to 11. Hereinafter, a photographing method using the photographing

apparatus

100, 200, 300 will be described. In the photographing method described below, all the technical features of the above-described photographing

apparatuses

100, 200, and 300 may be applied, and a redundant description thereof will be omitted.

Referring to FIG. 12, the photographing method includes: irradiating light (S1110), condensing light reflected from the object 10 using the focusing optical system 120 (S1120), and the focusing optical system 120. Adjusting the distance between the object 10 (S1130) and photographing an image of the object 10 whenever the distance between the focusing optical system 120 and the object 10 changes by a predetermined interval (S1140). It may include.

In operation S1110, the light 10 may be irradiated onto the object 10 using the light source 110. The light source 110 may adjust the irradiation time of the light in accordance with the predetermined exposure time E. As another example, the light source 110 may continuously radiate light, and the aperture of the photographing unit 140 may operate in accordance with the exposure time E. In addition, the exposure time E may be determined in consideration of the pixel size and magnification of the photographing unit 140 and the maximum vibration speed between the focusing optical system 120 and the object 10 according to Equation 4.

In operation S1120, the light reflected from the object 10 may be collected using the focusing optical system 120. The focusing optical system 120 may have a predetermined depth. The sharpness of the image formed by the light passing through the focusing optical system 120 may vary depending on whether the focusing point P is located at the depth.

In operation S1130, the relative distance between the focusing optical system 120 and the object 10 may be changed. In operation S1130, the distance adjusting unit 130 may allow the moving range of the focusing point P to satisfy Equations 1 and 2 above.

In operation S1140, while the focusing point P moves, the photographing unit 140 may photograph an image of the object 10 a plurality of times. The photographing unit 140 may photograph an image of the object 10 whenever the distance between the focusing optical system 120 and the object 10 changes by a predetermined interval Δh. In addition, the predetermined interval Δh may be set smaller than the depth of field DOF of the focusing optical system 120. As a result, even when the photographing unit 140 is photographed in a moving environment, at least one sharp image may be captured.

Referring to FIG. 13, the photographing method may further include generating a pulse signal according to a change in distance between the focusing optical system 120 and the object 10 (S1135). The pulse signal may be generated by the encoder 250 shown in FIG. As another example, the controller 355 of FIG. 7 receiving the electrical signal of the encoder 250 may generate a pulse signal. Based on the pulse signal, operation control of the distance controller 130 may be performed. In addition, the photographing unit 140 may be synchronized based on the pulse signal.

Referring to FIG. 14, the photographing method may further include extracting sharpness of the images photographed by the photographing unit 140 (S1150) and extracting a focusing distance from the sharpness values of the images (S1160). .

In operation S1150, the processor 160 may receive images from the photographing unit 140 and evaluate the sharpness of each of the images. Then, each of the sharpness of the evaluated images can be converted into a numerical value.

In operation S1160, the processor 160 may determine a focusing distance from the sharpness values of the images. As an example, the height H _i at which the i-th shot with the highest sharpness is taken may be determined as the focusing distance. As another example, processor 160 may sharpness _{_{_{_{C i -1, C i, C}}}} i +1 and the equation of the image obtained in each of the height _{_{H i-1, H i,}} H i + 1 , as shown in Figure 11 The optimal focusing distance H _max may be calculated from 10 and the height H _max may be determined as the auto focusing distance.

In the above, with reference to FIGS. 1 to 14, a photographing method using the photographing

apparatus

100, 200, 300 and the photographing

apparatus

100, 200, 300 according to the exemplary embodiments has been described. According to embodiments, while the auto focusing operation is performed while the distance between the object 10 and the focusing optical system 120 is changed, the time required for auto focusing may be shortened. In addition, although auto focusing is performed dynamically, a clear image may be obtained by allowing at least one image to be captured in a depth range of the focusing optical system 120. In addition, the accuracy of the auto focusing operation can be increased by correcting the correct focusing distance from the sharpness values of the images.

While many details are set forth in the foregoing description, they should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the technical spirit described in the claims.

Claims

A light source for irradiating light onto the object;

A focusing optical system for changing a path of light reflected from the object;

A photographing unit which photographs an image of the object formed by the focusing optical system; And

And a distance controller configured to adjust a distance between the focusing optical system and the object.

The photographing unit captures an image of the object whenever the distance between the focusing optical system and the object is changed by a predetermined interval, wherein the predetermined interval is set smaller than a depth of field of the focusing optical system. Shooting device.
The method of claim 1,

The photographing unit is a photographing apparatus for photographing the image of the object by a global shutter (global shutter) method.
The method of claim 1,

And the distance adjusting unit changes the distance between the object and the focusing optical system at a constant speed in at least one time interval.
The method of claim 3, wherein

And a speed at which the distance controller changes the distance between the object and the focusing optical system satisfies Equation 1.

.... Equation 1

(V1 = size of the distance change speed between the object and the focusing optics, f = number of shots per hour in the constant velocity section, DOF = depth of the focusing optics)
The method of claim 1,

And a speed at which the distance controller changes the distance between the object and the focusing optical system satisfies Equation 2.

V1 <DOF / E ......... Equation 2

(V1 = magnitude of the speed of change of distance between the object and the focusing optical system, DOF = depth of focusing optical system, E = exposure time per frame of the photographing unit)
The method of claim 1,

The exposure time per frame of the photographing unit satisfies Equation 3.

......... Equation 3

(E = exposure time per frame of the imager, A pixel = pixel area of the imager, M = magnification, V2 max = maximum value of the relative vibration speed between the imager and the object)
The method of claim 1,

And an encoder configured to generate an electrical signal by detecting a change in distance between the object and the photographing unit.
The method of claim 7, wherein

And a controller configured to generate a synchronization signal for the photographing unit based on the electrical signal generated by the encoder.
The method of claim 1,

And a processor configured to receive images of the object photographed by the photographing unit, and extract sharpness of the images.
The method of claim 9,

And the processor determines a distance between the object and the focusing optical system on which the sharpest image is captured as a focusing distance.
The method of claim 9,

And the processor determines a focusing distance according to Equation 4 from the sharpness values of the images.

.... Equation 4

(H = distance between the focusing optics and the object in the focusing state, H i = distance between the focusing optics and the object in the i-th shot with the highest sharpness measured, H i-1 = focusing optics in the i-1th shot) Distance between the object and H i + 1 = distance between the focusing optics and the object in the i + 1th shot, C i = sharpness value of the i-th image measured with the highest sharpness, C i -1 = i- Sharpness value of the first shot image, C i +1 = Sharpness value of the i + 1th shot image)
The method of claim 1,

And a section in which the distance controller changes the distance between the object and the focusing optical system is determined by Equation 5 and Equation 6.

H-D-δ <X <H + D + δ ....... Equation 5

..... Equation 6

(X = distance between the object's support and the focusing point of the focusing optics, H = expected thickness of the object, D = thickness deviation of the object, δ = acceleration interval, V1 = maximum velocity, a = acceleration)
Irradiating light onto the object;

Focusing light reflected from the object using a focusing optical system;

Adjusting a distance between the focusing optics and the object; And

And a photographing unit photographing an image of the object whenever the distance between the focusing optical system and the object changes by a predetermined interval.

And the predetermined interval is set smaller than the depth of the focusing optical system.
The method of claim 13,

The adjusting of the distance may include changing the distance between the object and the focusing optical system at a constant speed in at least one time interval.
The method of claim 14,

In the adjusting of the distance, the photographing unit captures an image of the object at a predetermined time interval in a time interval in which the distance between the object and the focusing optical system is changed at a constant speed.

And a speed at which the distance between the object and the focusing optical system is changed satisfies Equation (1).

.... Equation 1

(V1 = magnitude of the speed of change of distance between the object and the focusing optical system, f = number of shots per hour in the constant velocity section, DoF = depth of focusing optical system, and α is any real number satisfying 0.1 <α <0.5)
The method of claim 14,

In the adjusting of the distance, the speed of changing the distance between the object and the focusing optical system satisfies Equation 2.

V1 <DOF / E ......... Equation 2

(V1 = magnitude of the speed of change of distance between the object and the focusing optical system, DOF = depth of focusing optical system, E = exposure time per frame of the photographing unit)
The method of claim 14,

And detecting the change in distance between the object and the photographing unit to generate an electrical signal.
The method of claim 17,

And generating a synchronization signal for the photographing unit based on the electrical signal.
The method of claim 14,

And extracting sharpness of the images by receiving images of the object photographed by the photographing unit.
The method of claim 19,

And determining a focusing distance according to Equation 3 from the sharpness values of the images.

.... Equation 3

(H = distance between the focusing optics and the object in the focusing state, H i = distance between the focusing optics and the object in the i-th shot with the highest sharpness measured, H i-1 = focusing optics in the i-1th shot) Distance between the object and H i + 1 = distance between the focusing optics and the object in the i + 1th shot, C i = sharpness value of the i-th image measured with the highest sharpness, C i -1 = i- Sharpness value of the first shot image, C i +1 = Sharpness value of the i + 1th shot image)