TW201807404A - Method and apparatus of detecting particles on upper surface of glass, and method of irradiating incident light - Google Patents

Abstract

A particle detecting method including: disposing a rotatable mirror on a path of light emitted from a light source so that the mirror reflects the light to irradiate an incident light to the upper surface; calculating an incident angle of the incident light so that a first region where the incident light meets the upper surface of the glass and a second region where light transmits through the glass and meets a lower surface of the glass do not overlap with each other when viewed from above; rotating the mirror based on the calculated incident angle; acquiring an image of the first region with a camera disposed above the first region while conveying the glass in a horizontal direction; and detecting particles by analyzing the acquired image. The detected particles are considered as existing on the upper surface.

Description

Method and apparatus for detecting particles on an upper surface of glass and method of irradiating incident light

The present application claims priority to the Korean Patent Application No. 10/2016/0064, filed on May 25, 2016, the content of which is hereby incorporated by reference.

The present disclosure relates to methods and apparatus for detecting particles on an upper surface of a glass, and methods of illuminating incident light.

In general, a microcircuit pattern is deposited only on one surface (e.g., the upper surface) of a flat glass for a flat panel display without depositing a microcircuit pattern on the other surface (e.g., the lower surface) of the flat glass. If the microcircuit pattern is deposited on particles present on the upper surface of the flat glass, the microcircuit pattern can have some drawbacks. Therefore, it is necessary to check the presence or absence of particles on the upper surface of the flat glass before depositing the microcircuit pattern.

In order to detect only particles on the upper surface of the flat glass, conventional flat glass particle detecting devices include: first and second illumination devices configured to illuminate the flat glass at different angles above the flat glass, respectively The upper surface and the lower surface; and the first and second cameras are configured to each acquire an image of the upper surface illumination area and the lower surface illumination area.

Since the flat glass has a predetermined thickness, particles on the upper surface of the image are indicated as bright portions, and particles on the lower surface are indicated as dark portions. Conventional devices are configured to compare and analyze images acquired by each of the first and second cameras and to detect particles present on the upper surface.

However, since the conventional device has two illumination devices and two cameras, the cost of manufacturing equipment (and the cost of manufacturing flat glass) is increased. Furthermore, as the conveying speed of flat glass has recently become higher and higher, it is necessary to enhance the detection speed of particles on the upper surface of the flat glass. However, conventional devices have difficulty meeting this need because conventional devices must compare and analyze images acquired by two cameras.

The present disclosure addresses a solution to at least one of the foregoing problems. The present disclosure provides methods and apparatus for detecting particles on the upper surface of a glass. Such a method and apparatus can use only one light source and a camera, and the present disclosure provides a method of illuminating incident light.

One aspect of the present disclosure provides a method of detecting particles on an upper surface of a glass. The method includes: placing a rotatable mirror on a path of light emitted by the light source such that the mirror reflects light to illuminate the incident light to the upper surface; calculating an incident angle of the incident light such that the first region and the second region are viewed from above Do not overlap each other, the first area is at the upper surface of the incident light intersection glass, and the second area is where the light is transmitted through the glass and intersects the lower surface of the glass; the mirror is rotated based on the calculated incident angle; to be placed above the first area The camera acquires an image of the first region; and detects the particles by analyzing the acquired image. The detected particles are considered to be present on the upper surface.

In a specific embodiment, the angle of incidence is calculated based on the angle of refraction of the glass and the thickness.

In a specific embodiment, the angle of incidence is calculated based on a maximum of the horizontal distance between the right end of the first region and the left end of the second region.

In a specific embodiment, the maximum value of the horizontal distance is calculated based on the following equation: Where L' is the horizontal distance, d is the thickness of the glass, n is the refractive index of the glass, θ is the incident angle of the incident light, and W is a width of the incident light.

In a specific embodiment, the rotating mirror is performed prior to conveying the glass.

In a specific embodiment, the camera is mounted such that the right end of the first region is positioned at the right end of the field of view of the camera.

In a specific embodiment, the incidence angle of the incident light and the rotating mirror are performed when at least one of the refractive index and the thickness of the glass is changed.

Another aspect of the present disclosure provides a method of irradiating incident light onto an upper surface of a glass to detect particles on the upper surface. The method includes: placing a rotatable mirror on a path of light emitted by the light source such that the mirror reflects light to illuminate the incident light to the upper surface; and calculating an incident angle of the incident light based on a refractive angle and a thickness of the glass such that when viewed from above The first region and the second region do not overlap each other, the first region is at the upper surface of the incident light intersecting glass, the second region is where the light is transmitted through the glass and intersects the lower surface of the glass; and is rotated based on the calculated incident angle mirror. When the at least one of the refractive index and the thickness of the glass is changed, the calculation of the incident angle and the rotation of the mirror are performed.

In a specific embodiment, the angle of incidence is calculated based on a maximum of the horizontal distance between the right end of the first region and the left end of the second region.

In a specific embodiment, the maximum value of the horizontal distance is calculated based on the following equation: Where L' is the horizontal distance, d is the thickness of the glass, n is the refractive index of the glass, θ is the incident angle of the incident light, and W is the width of the incident light.

Another aspect of the present disclosure provides an apparatus for detecting particles on an upper surface of a glass. The apparatus includes a light source configured to emit light, a rotatable mirror disposed on the path of the light, and configured to adjust an angle of incidence of incident light to be illuminated to the upper surface, and a controller configured to control rotation of the mirror, The first area and the second area do not overlap each other when viewed from above, the first area is at the upper surface of the incident light intersection, the second area is where the light is transmitted through the glass and the lower surface of the intersecting glass; and the camera is configured to Get the image of the first area. The controller is configured to detect the particles by analyzing the acquired images and to treat the detected particles as being present on the upper surface.

In a particular embodiment, the controller is configured to control rotation based on the angle of refraction and thickness of the glass.

In a particular embodiment, the controller is configured to control the rotation based on a maximum of a horizontal distance between a right end of the first region and a left end of the second region.

In a specific embodiment, the maximum value of the horizontal distance is calculated based on the following equation: Where L' is the horizontal distance, d is the thickness of the glass, n is the refractive index of the glass, θ is the incident angle of the incident light, and W is a width of the incident light.

In a specific embodiment, the camera is configured such that the right end of the first region is positioned at the right end of the field of view of the camera.

A specific embodiment of a method and apparatus for detecting particles on the upper surface of a glass, and a method of illuminating incident light will be described below with reference to additional figures.

Accompanying drawings, and first to FIG. 3 of two-dimensional Cartesian coordinate system (X and Y axes). In the following description, the positive X-axis direction and the positive Y-axis direction indicate the rightward direction and the upward direction, respectively. Furthermore, the negative X-axis direction and the negative Y-axis direction indicate the leftward direction and the downward direction, respectively.

In the following description, the words "upper", "lower", "upper", "lower", "right", "left", etc. refer to the relative spatial relationship illustrated in the additional schema (where glass is assumed) Horizontal transport), and is not intended to represent an absolute spatial relationship depending on the direction of glass transport.

As FIG. 1 and FIG. 2 illustrates, according to a specific embodiment to detect particles on the upper surface of the device 100 of the embodiment of the glass (hereinafter simply referred to as "particle detector apparatus"), comprising: a light source 110; mirror 120; controller And the camera 140.

In the particle detecting apparatus 100, the object to be inspected is the glass 10, and the glass 10 is conveyed in the horizontal direction (for example, in the right direction). In the particle detecting apparatus according to another specific embodiment, the object to be inspected may be a glass that is not transported and is fixed. The glass 10 includes an upper surface 11 and a lower surface 12 on which a microcircuit pattern is deposited, and no microcircuit pattern is deposited on the lower surface 12. In another specific embodiment, the glass 10 may comprise a flat glass, a glass substrate, a flat glass substrate, or the like, and has a predetermined thickness and a predetermined width, and extends in a leftward or rightward direction. In order to better explain the particle detector device 100, the first to figures 1 3, the glass 10 is illustrated as having a larger thickness, i.e., thicker than the actual thickness of the illustrated glass 10 (e.g., about several millimeters to a few microns).

Light source 110 is placed over glass 10 to emit light 31 in a direction perpendicular to glass 10. Because the camera 140 is also placed over the glass 10, the light source 110 can be fabricated to integrate with the camera 140 to reduce the size of the particle detecting device 100. Light source 110 can encompass a variety of concepts such as lighting devices, lighting devices, lights, beam formers, and the like. In another embodiment, the light source 110 can be placed over the glass 10 to emit light 31 in a direction that is oblique to the glass 10. In a particular embodiment, light 31 can include radiation as well as laser beams and the like. In one particular embodiment, light source 110 can include a focusing lens 111 to focus light 31 to a predetermined illumination area. The focus lens 111 can be configured to adjust the size of the illuminated area of the light 31 emitted by the light source 110.

The mirror 120 is placed on the path of the light 31 emitted by the light source 110 such that the incident light 32 is illuminated to the upper surface 11 of the glass 10. The incident angle θ of the incident light 32 is adjusted by the mirror 120 placed on the path of the light 31. Thus, incident light 32 can be illuminated to the upper surface 11 of the glass 10 by a relatively wide range of angles of incidence θ as compared to conventional devices that direct the source directly to the glass. The mirror 120 is electrically coupled to the controller 130 to be rotated based on control signals from the controller 130. The mirror 120 is rotatable along the rotational axis 121 in a clockwise or counterclockwise direction. To this end, the mirror 120 can include a drive mechanism and a power transfer mechanism. In a particular embodiment, the drive mechanism can include a drive motor, an electric motor, and the like. In one particular embodiment, the power transfer mechanism can include pulleys and belts, sprocket and chain, drive and driven gears, and the like. In one particular embodiment, mirror 120 can encompass a variety of concepts such as mirrors, reflective devices, reflectors, and the like. In the following description, the incident light 32 represents light when the light 31 is reflected by the mirror 120 and proceeds to reach the upper surface 11 of the glass 10 from the light 31.

Controller 130 is configured to calculate an angle of incidence θ of incident light 32, control rotation of mirror 120 based on the calculated angle of incidence θ, detect particles by analyzing images acquired by camera 140, and determine detected particles It is considered to be present on the upper surface 11 of the glass 10.

In particular, the controller 130 is configured to calculate the angle of incidence θ of the incident light 32 such that the first region 41 and the second region 42 do not overlap each other when viewed from above. Here, the first region 41 is a region where the incident light 32 intersects the upper surface 11 of the glass 10, and the second region 42 is a region where the transmitted light 33 transmitted through the glass 10 intersects the lower surface 12 of the glass 10. In other words, the controller 130 is configured to calculate the angle of incidence θ of the incident light 32 such that the horizontal distance L' between the right end of the first region 41 and the left end of the second region 42 is greater than zero.

If the first area 41 and the second area 42 do not overlap each other when viewed from above, it is possible to acquire the image of the first area 41 by using the camera 140 above the glass 10 without acquiring the image of the second area 42. In this case, since the image of the illuminated area (i.e., the second area 42) on the lower surface 12 of the glass 10 is not captured by the camera 140, the camera 140 cannot acquire the particle image on the second area 42. Furthermore, since no light reaches the particles on the non-irradiated area (i.e., the remaining areas other than the second area 42) on the lower surface 12 of the glass 10, the camera 140 cannot acquire the particle image. Therefore, the camera 140 can acquire only the image of the upper side particle 21 on the first area 41, and the image of the lower side particle on the lower surface 12 of the glass 10 can be acquired by the camera 140.

In one embodiment, controller 130 can include a computer having program storage components. The program storage component can store any one or more programs associated with calculating the angle of incidence θ, rotating the mirror 120, and analyzing the image. For example, the program storage unit may include a computer readable hard disk, a flexible disk, a compact disk, a magnetic optical disk, a memory card, and the like.

In one particular embodiment, the controller 130 can be configured to control the rotation of the mirror 120 based on the refractive index and thickness of the glass 10 such that the first region 41 and the second region 42 do not overlap each other when viewed from above.

For example, the horizontal distance L' can be calculated from the following equation: Where L' is the horizontal distance, d is the thickness of the glass 10, n is the refractive index of the glass 10, θ is the incident angle of the incident light 32, and W is the width of the incident light 32 in the horizontal direction.

Equation 1 can be derived from Equations 2 through 6 below. First, the horizontal distance L' can be expressed by Equation 2 as follows: Here, referring to Fig . 3 , W _A is the horizontal width of the first region 41, W _B is the horizontal width of the second region 42, and L is the horizontal distance between the center of W _{A and the} center of W _B .

In Equation 2, since the thickness of the glass 10 is very thin (such as from 0.2 mm to 4 mm), it can be assumed that the horizontal width W _{A of the} first region 41 is equivalently equal to the horizontal width W _{B of the} second region 42. Therefore, the horizontal distance L' can be expressed by Equation 3 as follows:

L in Equation 3 can be represented by a trigonometric function from Equation 4 relating to the refraction angle α:

The angle of refraction α in Equation 4 can be expressed by Equation 5, which is related to the angle of incidence θ, using Snell's law:

W _A in Equation 3 can be expressed by Equation 6 relating to the angle of incidence θ:

If Equations 4 through 6 are applied to Equation 3, Equation 1 is solved. Since the refractive index n, the thickness d, and the width W are constant values in Equation 1, the horizontal distance L' is represented by a function related to the incident angle θ.

Therefore, if a specific glass is judged as the target to be inspected, the refractive index and thickness of the specific glass are also determined. In this case, the incident angle θ can be calculated based on Equation 1 such that the horizontal distance L′ is greater than zero (that is, the first region 41 and the second region 42 do not overlap each other when viewed from above).

Furthermore, Equation 1 is theoretical, and in fact the refractive index may not be uniform throughout the glass. Therefore, in order to ensure that the first region 41 and the second region 42 do not overlap, the incident angle θ can be calculated based on Equation 1 such that the horizontal distance L′ has a maximum value. For example, the refractive index n of the glass 10 is 1.5, a width W of 100 microns, and a thickness of 500 microns, the relationship between the horizontal distance L 'and the incident angle θ is illustrated in FIG. 4. Referring to Fig . 4 , when the incident angle θ is 58.5 degrees, the horizontal distance L' has a maximum value. In this case, the maximum value of the horizontal distance L' is 154.1 μm.

The controller 130 is configured to control the rotation (or tilt angle) of the mirror 120 by the drive mechanism of the drive mirror 120 based on the incident angle θ calculated by the foregoing method.

As described above, the incident angle θ at which the first region 41 and the second region 42 do not overlap each other depends on the refractive index and thickness of the glass 10. Therefore, when at least one of the refractive index and the thickness of the glass as the inspection target is changed, the controller 130 is configured to calculate the incident angle θ of the incident light 32 based on the changed refractive index (or the changed thickness), thereby calculating The resulting incident angle θ controls the rotation of the mirror 120.

The camera 140 is placed above the glass 10 in a direction perpendicular to the glass 10. Camera 140 has a field of view FOV (see dashed lines in FIG. 1 and illustrated in FIG. 2), the field of view FOV in the direction of the glass 10, the upper surface 11 extends to the intersection of the glass 10 from the camera 140 vertically downward. Camera 140 is configured to acquire an image of first region 41 without acquiring an image of second region 42. In other words, the camera 140 is mounted such that the camera 140 field of view FOV includes the first area 41 and does not include the second area 42. Since the upper side particles 21 on the first region 41 of the upper surface 11 scatter the incident light 32 to form the scattered light 34, the camera 140 acquires an image of the upper side particles. The camera 140 is electrically connected to the controller 130. The image acquired by the camera 140 is transmitted to the controller 130 in the form of an electrical signal. In this particular embodiment, camera 140 can include a linear charge coupled device (CCD) camera. In one embodiment, camera 140 may encompass a variety of concepts, such as video devices, imaging devices, detection devices, and detectors, to name a few.

In one particular embodiment, as illustrated in FIG. 2, the camera 140 may be installed such that the right end of the first region 41 is positioned at the right end of the field of view FOV, whereby the field of view FOV is positioned furthest from the second region 42. Therefore, it is possible to restrict the light scattered by the lower side particles 22 on the second area 42 from being generated in the image acquired by the camera 140.

The controller 130 is configured to view the highlights on the image as particles by analyzing the image acquired by the camera 140. As described above, the camera 140 does not acquire an image of the underside particles 22 present on the lower surface 12 of the glass 10. Thus, the controller 130 is configured to treat all detected particles as being present on the upper surface 11 of the glass 10.

As shown in FIG . 5 , a method for detecting particles on the upper surface of the glass 200 according to a specific embodiment (hereinafter referred to as "particle detection method") includes: placing a mirror S201; calculating an incident angle S202 of the incident light; Rotating the mirror S203; acquiring the image S204 of the first area; and detecting the particle S205.

In the placement mirror S201, the mirror 120 is placed on the path of the light 31 emitted by the light source 110. The mirror 120 reflects the light 31 to illuminate the incident light 32 to the upper surface 11 of the glass 10.

In the incident angle S202 at which the incident light is calculated, the incident angle θ of the incident light 32 is calculated such that the first region 41 and the second region 42 do not overlap each other when viewed from above. The manner in which the angle of incidence θ of the incident light 32 is calculated may be the same as that of the particle detecting apparatus 100 according to one embodiment. In other words, the incident angle θ of the incident light 32 can be calculated based on the refractive index and thickness of the glass 10. Furthermore, the incident angle θ of the incident light 32 can be calculated based on the maximum value of the horizontal distance L'. Furthermore, the maximum value of the horizontal distance L' can be calculated by Equation 1.

In the rotating mirror S203, the mirror 120 is rotated based on the incident angle θ calculated in the incident angle S202 at which the incident light is calculated. In a specific embodiment, the rotating mirror S203 can be performed prior to transporting the glass 10. Therefore, since the rotation of the mirror 120 is controlled before starting to inspect the glass 10, it is possible to reduce the actual time required to inspect the glass 10.

In the image S204 of the first region, the camera 140 acquires the image of the first region 41 while the glass 10 is conveyed in the horizontal direction (for example, to the right). Since the position and function of the camera 140 in the particle detecting apparatus 100 according to one embodiment have been explained, a detailed description about the foregoing is omitted herein.

In the detection particle S205, the particle is detected by analyzing the image acquired in the image S202 of the first region. In particular, the particles are detected by looking for bright portions displayed by the scattered light 34 in the image. The particles detected in the detecting particles S205 are considered to be present on the upper surface 11 of the glass 10.

As illustrated in FIG . 6 , a method of illuminating incident light 300 according to a specific embodiment includes: placing a mirror S301; calculating an incident angle of the incident light S302; and rotating the mirror S303. In this embodiment, the incident angle S302 of the incident light and the rotating mirror S303 are performed when at least one of the refractive index and the thickness of the glass 10 is changed.

Since the placement mirror S301 and the rotation mirror S303 illustrated in Fig . 6 are the same as the placement mirror S201 and the rotation mirror S203 illustrated in Fig . 5 , a detailed description about the foregoing is omitted herein.

In the incident angle S302 at which the incident light is calculated, the incident angle θ of the incident light 32 is calculated based on the refractive index and the thickness of the glass 10 such that the first region 41 and the second region 42 do not overlap each other when viewed from above. The manner in which the angle of incidence θ of the incident light 32 is calculated may be the same as that of the particle detecting apparatus 100 according to one embodiment. In other words, the incident angle θ of the incident light 32 can be calculated based on the maximum value of the horizontal distance L'. Furthermore, the maximum value of the horizontal distance L' can be calculated by Equation 1.

The technical idea of the present disclosure is not limited to the examples illustrated in the foregoing specific embodiments and additional drawings. It will be apparent to those skilled in the art of the present invention that various alternatives, modifications and variations are possible within the scope of the technical idea of the present disclosure.

A method and apparatus for detecting particles on an upper surface of a glass according to a specific embodiment is configured to calculate an optimum angle of incidence of incident light and to control rotation of the mirror based on the calculated optimal angle of incidence. Therefore, it is possible to accurately detect only the particles on the upper surface of the glass by using only one camera. Further, according to the method of irradiating the incident light, it is possible to accurately irradiate the incident light having the optimum incident angle to the upper surface of the glass.

10‧‧‧ glass
11‧‧‧ upper surface
12‧‧‧ Lower surface
21‧‧‧Upper particles
22‧‧‧lower particles
31‧‧‧Light
32‧‧‧ incident light
33‧‧‧ transmitted light
34‧‧‧scattered light
41‧‧‧First area
42‧‧‧Second area
100‧‧‧ particle detection equipment
110‧‧‧Light source
111‧‧‧focus lens
120‧‧ ‧ mirror
121‧‧‧Rotary axis
130‧‧‧ Controller
140‧‧‧ camera
FOV‧‧ Vision
200‧‧‧ particle detection method
300‧‧‧Method of illuminating the angle of incidence

FIG 1 illustrates a schematic side view of a first device on the surface of particles of glass in accordance with the detection of a particular embodiment.

FIG 2 is a first partially enlarged view of FIG.

FIG 3 is a second partially enlarged view of FIG.

Fig . 4 is a graph showing the relationship between the incident angle and the horizontal distance when the apparatus shown in Fig . 1 is used.

FIG 5 illustrates a flowchart of a method according to the particles on the surface of the glass on the detection of a particular embodiment.

Flowchart of a method illustrating a sixth embodiment of the incident light is irradiated to the specific embodiment.

Domestic deposit information (please note according to the order of the depository, date, number)

Foreign deposit information (please note in the order of country, organization, date, number)

Claims (15)

A method of detecting particles on an upper surface of a glass, comprising the steps of: placing a step of placing a rotatable mirror on a path of light emitted by a light source such that the mirror reflects the light to reflect an incident light Irradiating to the upper surface; calculating a period of incidence of the incident light such that a first region and a second region do not overlap each other when viewed from above, the first region being the incident light that intersects the glass At the upper surface, the second region is where light is transmitted through the glass and intersects the lower surface of the glass; a rotating step of rotating the mirror based on the calculated angle of incidence; a step of acquiring to place a portion above the first region The camera acquires an image of the first region; and a detecting step of detecting the particle by analyzing the acquired image, wherein the detected particle is regarded as being present on the upper surface. The method of claim 1, wherein the incident angle is calculated based on a refractive angle of the glass and a thickness. The method of claim 2, wherein the incident angle is calculated based on a maximum value of a horizontal distance between the right end of the first region and the left end of the second region. The method of claim 3, wherein the maximum value of the horizontal distance is calculated based on the following equation: Where L' is the horizontal distance, d is the thickness of the glass, n is the refractive index of the glass, θ is the incident angle of the incident light, and W is a width of the incident light. The method of claim 1, wherein the rotating step of rotating the mirror is performed prior to transporting the glass. The method of claim 1, wherein the camera is mounted such that the right end of the first area is positioned at the right end of a field of view of the camera. The method of claim 1, wherein the calculating step of calculating the incident angle and the rotating step of rotating the mirror are performed when at least one of a refractive index and a thickness of the glass is changed. A method of irradiating an incident light onto an upper surface of a glass to detect particles on the upper surface, comprising the steps of: placing a step of placing a rotatable mirror on a path of light emitted by a light source such that The mirror reflects the light to illuminate the incident light onto the upper surface; and the calculating step calculates an incident angle of the incident light based on a refractive index and a thickness of the glass such that a first region and a The second regions do not overlap each other, the first region is where the incident light meets the upper surface, the second region is where the light is transmitted through the glass and intersects the lower surface of the glass; and the rotating step is based on the calculated incident The mirror is rotated angularly, wherein the calculating step of calculating the incident angle and the rotating step of rotating the mirror are performed when at least one of a refractive index and a thickness of the glass is changed. The method of claim 8, wherein the incident angle is calculated based on a maximum value of a horizontal distance between the right end of the first region and the left end of the second region. The method of claim 9, wherein the maximum value of the horizontal distance is calculated based on the following equation: Where L' is the horizontal distance d is the thickness of the glass, n is the refractive index of the glass, θ is the incident angle of the incident light, and W is the width of the incident light. An apparatus for detecting particles on an upper surface of a glass, comprising: a light source configured to emit light; a rotatable mirror placed on a path of the light, the mirror configured Adjusting an incident angle of incident light to illuminate the upper surface; a controller configured to control rotation of the mirror such that a first region and a second region do not interact with each other when viewed from above Overlap, the first area is where the incident light meets the upper surface, the second area is where the light is transmitted through the glass and intersects the lower surface of the glass; a camera, the camera is configured to acquire one of the first areas An image, wherein the controller is configured to detect particles by analyzing the acquired image and to treat the detected particles as being present on the upper surface. The apparatus of claim 11, wherein the controller is configured to control the rotation based on a refractive angle and a thickness of the glass. The device of claim 12, wherein the controller is configured to control the rotation based on a maximum of a horizontal distance between a right end of the first region and a left end of the second region. The apparatus of claim 13, wherein the maximum value of the horizontal distance is calculated based on the following equation: Where L' is the horizontal distance, d is the thickness of the glass, n is the refractive index of the glass, θ is the incident angle of the incident light, and W is a width of the incident light. The method of claim 11, wherein the camera is configured such that the right end of the first region is positioned at the right end of a field of view of the camera.