KR20170044392A

KR20170044392A - Image sensing apparatus with position control functuion of optical filter

Info

Publication number: KR20170044392A
Application number: KR1020150144025A
Authority: KR
Inventors: 백명흠; 허은정
Original assignee: 백명흠; 허은정
Priority date: 2015-10-15
Filing date: 2015-10-15
Publication date: 2017-04-25

Abstract

The present invention includes an optical filter position control part whose height is controlled in response to an electrical control signal applied between an optical filter layer and a color filter layer formed in the upper part of an image sensor. An image provided from the image sensor is compared with a reference image. According to the comparison result, the optical filter position control unit is controlled to control the position of the optical filter layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensing apparatus having an optical filter position adjustment function,

The present invention relates to an image sensor, and more particularly, to an image sensing apparatus having an optical filter position adjustment function.

Image sensors are known as image sensing devices that are widely used in digital still cameras and camera phones.

An image sensing apparatus constituting the image sensor may employ an optical filter such as an infrared filter for filtering infrared rays. Since the distance between the optical filter and the image sensor is fixed at the time of manufacture or assembly, The image sensing performance of the image sensing device may be deteriorated if it is not fixed at the correct position.

SUMMARY OF THE INVENTION The present invention provides an image sensing apparatus having an optical filter position adjustment function and an image sensing method therefor.

According to one aspect of the present invention, there is provided an image sensing apparatus including:

An image sensor for sensing an image through a unit pixel;

A color filter layer formed on top of the image sensor for color filtering;

An optical filter position adjuster whose height is adjusted in response to an applied electrical control signal;

An optical filter layer disposed on the optical filter position adjusting unit; And

And a controller for comparing the image provided from the image sensor with a reference image and controlling the position of the optical filter layer by controlling the optical filter position adjusting unit according to the comparison result.

In an embodiment of the present invention, the optical filter regulator may be constituted by a piezoelectric element.

In an embodiment of the present invention, the optical filter regulator may comprise an electroactive polymer actuator.

In an embodiment of the present invention, the optical filter controller may be constituted by a coil actuator.

In an embodiment of the present invention, the optical filter controller may be configured as a gyroscope.

In an embodiment of the present invention, the optical filter layer may be an infrared filter layer.

In an embodiment of the present invention, the optical filter layer may include a low-pass infrared filter layer and a high-pass infrared filter layer.

In an exemplary embodiment of the present invention, a microlens layer may be further provided between the color filter layer and the optical filter alignment layer.

According to still another aspect of the present invention, there is provided an image sensing apparatus comprising:

An image sensor for sensing an image through a unit pixel;

A color filter layer formed on top of the image sensor for color filtering;

An optical filter position adjustment layer whose height is adjusted in response to an applied electrical control signal;

And an optical filter layer disposed on the optical filter position adjusting unit.

In an embodiment of the present invention, the optical filter control layer may comprise any one of a piezoelectric element, an electroactive polymer actuator, a coil actuator, and a gyroscope.

In an embodiment of the present invention, a microlens layer may be further provided between the color filter layer and the optical filter position adjustment layer.

According to another aspect of the present invention, there is provided a method of controlling an operation of an image sensing apparatus,

Providing an optical filter position adjustment unit between the color filter layer and the optical filter layer positioned on top of the image sensor;

Comparing an image provided from the image sensor with a pre-stored reference image; And

And adjusting the position of the optical filter layer in the upper or lower direction by controlling the optical filter position adjusting unit according to the comparison result.

In an embodiment of the present invention, the optical filter regulator may be composed of a piezoelectric element, an electroactive polymer actuator, a coil actuator, and a gyroscope and may be driven by an electrical control signal.

According to the image sensing apparatus of the present invention as described above, since the position of the optical filter can be variably adjusted, there is an advantage that the performance of image sensing is improved.

1 is a circuit diagram showing a unit pixel of a general image sensor.
2 is a structural view of an image sensing apparatus according to an embodiment of the present invention.
FIG. 3 is an exemplary configuration diagram of an optical filter position adjusting unit in FIG. 2. FIG.
FIG. 4 is a diagram illustrating a driving operation of the optical filter position adjusting unit of FIG. 3. FIG.
5 is an overall structural view of an image sensing apparatus according to an embodiment of the present invention.
FIG. 6 is another exemplary configuration diagram of the optical filter position adjusting unit in FIG. 2. FIG.
7 is a diagram illustrating a driving operation of the optical filter position adjusting unit of FIG.
8 is a view showing a driving range according to Fig.
9 is a plan view showing an arrangement of unit pixels of a CMOS image sensor according to the present invention.
10 is a cross-sectional view showing a unit pixel of a CMOS image sensor taken along a direction aa 'of FIG.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features, and advantages of the present invention will become more apparent from the following description of preferred embodiments with reference to the attached drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art, without intention other than to provide an understanding of the present invention.

In this specification, when it is mentioned that some element or lines are connected to a target element block, it also includes a direct connection as well as a meaning indirectly connected to the target element block via some other element.

In addition, the same or similar reference numerals shown in the drawings denote the same or similar components as possible. In some drawings, the connection relationship of elements and lines is shown for an effective explanation of the technical contents, and other elements or functional blocks may be further provided.

Each of the embodiments described and exemplified herein may also include complementary embodiments thereof, and the basic operation and internal mechanism details of heater device control mounted on a semiconductor manufacturing facility or the like are described in detail in order to avoid obscuring the gist of the present invention. Please note that it is not.

An image sensor is an apparatus for converting one-dimensional or two-dimensional or more optical information into an electric signal. The types of image sensors are largely divided into an image pickup tube and a solid-state image pickup element. The imaging tube is widely used in the measurement, control, and recognition using the image processing technology centering on the television, and the application technology is developed. There are two types of commercially available solid-state image sensors: a metal-oxide-semiconductor (MOS) type and a charge coupled device (CCD) type.

A CMOS image sensor is a device that converts an optical image into an electrical signal using CMOS fabrication technology. The CMOS image sensor employs a switching method that sequentially produces outputs by using MOS transistors as many as the number of pixels.

Compared to a CCD image sensor widely used as a conventional image sensor, the CMOS image sensor is simpler in driving method and can realize various scanning methods, and the signal processing circuit can be integrated on a single chip, The use of compatible CMOS technology has the advantage of lowering manufacturing cost and power consumption.

1 is a circuit diagram showing a unit pixel of a CMOS image sensor having four transistors and two capacitance structures and shows a unit pixel of a CMOS image sensor composed of a photodiode PD as a light sensing means and four NMOS transistors .

Among the four NMOS transistors, the transfer transistor Tx serves to transfer the photo-charges generated in the photodiode PD to the floating diffusion region, and the reset transistor Rx is stored in the floating diffusion region for signal detection The drive transistor Dx serves as a source follower and the select transistor Sx serves for switching and addressing. In the figure, "Cf" represents the capacitance of the floating diffusion region, and "Cp" represents the capacitance of the photodiode.

The operation of the thus configured image sensor unit pixel is performed as follows. Initially, the reset transistor Rx, the transfer transistor Tx, and the select transistor Sx are turned on to reset the unit pixel. At this time, the photodiode PD starts to deplete, causing capacitance Cp to undergo carrier changing, and the capacitance Cf of the floating diffusion region is charged up to the supply voltage VDD voltage. Then, the transfer transistor Tx is turned off, the select transistor Sx is turned on, and the reset transistor Rx is turned off. After the output voltage V1 is read out from the unit pixel output terminal Out in such an operation state and stored in the buffer, the transfer transistor Tx is turned on to transfer the carriers of the capacitance Cp, which changes in accordance with the intensity of light, to the capacitance Cf, Then, the output voltage V2 is read out from the output terminal (Out), and analog data for V1 - V2 is converted into digital data, thereby completing one operation cycle for the unit pixel.

It is important that the image sensor used as an image recognition element is capable of converting incident light into electrons without loss. Since the unit pixel of the image sensor is composed of a photodiode as well as a circuit for processing signals in the unit pixel, as shown in FIG. 1, a device that serves to convert incident light into electrons is a photodiode. The area of the diode is limited. In order to overcome this problem, a microlens is formed on the unit pixel, and light incident on a region other than the photodiode region among the light entering the unit pixel is collected by the photodiode. The method of forming the microlenses can improve the optical collection speed of the image sensor.

On the other hand, an infrared (IR) filter may be disposed on the upper portion of the microlens.

In an embodiment of the present invention, an optical filter position adjustment layer or an optical filter up-down portion capable of adjusting the position of an infrared filter for optimal infrared filtering is provided.

2 is a structural view of an image sensing apparatus according to an embodiment of the present invention.

Referring to FIG. 2, an image sensor 110 is disposed at the lowermost portion of the housing 150. The image sensor 110 senses an image through a unit pixel as described above.

A color filter layer 112 may be formed on the image sensor 110 for color filtering. Here, it should be understood that the size of the color filter layer 112 is exaggerated relative to the size of the lower image sensor 110 for the sake of understanding.

A microlens layer 116 may be formed on the color filter layer 112 to form microlenses for condensing light.

An optical filter position adjusting unit 200 having a height adjusted in response to an electrical control signal is installed on the microlens layer 116 for the purpose of the present invention.

Here, the layer constituting the optical filter position adjuster 200 may be formed at a predetermined distance from the upper portion of the color filter layer 112 when the microlens layer 116 is omitted.

An optical filter layer 300 is provided on the optical filter position adjusting unit 200.

Here, the optical filter layer 300 may be an infrared filter.

The infrared filter includes a low pass infrared filter composed of a first nitride film and a first oxide film, a high pass infrared ray filter composed of a plurality of second nitride films and a second oxide film alternately stacked on the low pass infrared filter, Filter.

The low pass infrared filter can reflect all the light having a wavelength of 0.7 탆 when the first nitride film having a refractive index of 2.3 and the first nitride film having a refractive index of 1.43 and the first oxide film having a refractive index of 1.43 are alternately laminated five times.

The high-pass infrared filter can reflect all the light having a wavelength of 0.3 탆 when the second nitride film having a thickness of 240 Å and the second oxide film having a thickness of 430 Å are alternately laminated five times.

The thickness of the optical filter layer 300 is adjusted according to an electrical control signal of the optical filter position adjusting unit 200 so that the mounting position of the optical filter layer 300 is adjusted to be high or low. As a result, the distance between the optical filter layer 300 and the image sensor 110 may be adjusted to vary the optical filtering characteristics of the optical filter.

Therefore, the controller of the image sensing apparatus compares the image provided from the image sensor 110 with the reference image and controls the optical filter position adjusting unit 200 according to the comparison result to determine the position of the optical filter layer 300 .

FIG. 3 is an exemplary configuration diagram of an optical filter position adjusting unit in FIG. 2. FIG.

Referring to FIG. 3, the optical filter positioning unit 200 includes a lower electrode layer 212, an electroactive film 214, and an upper electrode layer 216. The electroactive film 214 interposed between the flexible electrode plates or electrode layers 212 and 216 includes a composite material having a thin dielectric layer and forms a capacitive structure.

FIG. 4 is a diagram illustrating a driving operation of the optical filter position adjusting unit of FIG. 3. FIG.

As shown in FIG. 4, when a voltage is applied to the electrodes, the different charges in the two electrodes are attracted to each other, and this electrostatic attraction forces the electroactive film 214 (along the Z-axis).

When a voltage is applied between the lower electrode layer 212 and the upper electrode layer 216, the electroactive film 214 is compressed to the maximum thickness b in the Z-axis direction. In addition, the compression distance generated by the film as a result of the applied voltage also depends on a number of other factors such as the dielectric constant of the elastomeric material and its size and stiffness.

When it returns to the inactive state due to the elimination of the voltage difference and induced charges, it returns to the thickness a as shown in FIG.

The length L and the width W of the electroactive polymer film 214 are much larger than the thickness t. Generally, the dielectric layer of the electroactive polymer film 214 has a thickness in the range of about 1 [mu] m to about 100 [mu] m and may be thicker than each electrode.

A family of electroactive polymer materials suitable for use in the present invention include, but are not limited to, dielectric elastomers, electroactive polymers, electroactive polymers, and ionically active polymers, and some copolymers.

Suitable dielectric materials include, but are not limited to, silicon, acrylic, polyurethane, fluorosilicone, and the like. The electroactive polymer has the characteristic of nonlinear reaction. Electronically active polymers typically change their shape and dimensions by the movement of electrons in response to an electric field (primarily dry). Ionically electroactive polymers are polymers whose shape and size change by the movement of ions in response to an electric field (mainly including wetting and electrolytes). Suitable electrode materials may include carbon, gold, platinum, aluminum, and the like.

In the embodiment of the present invention, the optical filter position adjuster 200 is an electroactive film 214, but any other piezoelectric element, coil actuator, and gyroscope may be used.

For example, in the case of a piezoelectric element, a mechanical fluctuation is caused by a piezo effect depending on a voltage level applied. As a result, the height of the actuator can be adjusted by applying a voltage as shown in FIG.

5 is an overall structural view of an image sensing apparatus according to an embodiment of the present invention.

Referring to FIG. 5, an optical filter up-down unit 202 is provided on an image sensor 110 for sensing an image through a unit pixel. The optical filter up / down unit 202 may be implemented as an optical filter position adjuster whose height is adjusted in response to an electrical control signal applied as described above.

A color filter layer may be formed on the image sensor 110 for color filtering.

The optical filter unit 300 may be provided on the optical filter up-down unit 202 and the optical filter unit 300 may be the optical filter unit described above.

The optical filter unit 300 filters the infrared light applied from the objective lens 400 with a predetermined filtering characteristic.

The controller 500 in the image sensing apparatus having the image processing unit 502 compares an image provided from the image sensor 110 with a reference image. The position of the optical filter unit 300 is controlled by controlling the optical filter position adjusting unit according to the comparison result. In this case, when the controller 500 applies the driving control signal DVC through the driving voltage applying unit 600, the driving voltage applying unit 600 generates the output voltage Vin accordingly, And provides it to the up-down unit 202.

Thus, the optical filter up-down portion 202 can vary from thickness a to thickness b to a maximum.

6, the controller 500 may apply the switch control signal SWC as a switching signal of the switch.

As described above, the optical filter position adjusting unit is provided between the color filter layer and the optical filter layer disposed on the upper portion of the image sensor,

Comparing an image provided from the image sensor with a previously stored reference image,

If the optical filter position adjustment unit is controlled according to the comparison result,

The position of the optical filter layer can be adjusted in the upper or lower direction.

According to the image sensing apparatus of the present invention, since the position of the optical filter can be variably adjusted, the filtering characteristic of the optical filter is optimally determined, and the performance of the image sensing is improved.

As a second embodiment, another exemplary form of the optical filter position adjuster will be described.

FIG. 6 is another exemplary structure of the optical filter position adjusting unit in FIG. 2, and FIG. 7 is a diagram illustrating a driving operation for the optical filter position adjusting unit in FIG. Fig. 8 is a view showing a driving range according to Fig. 7. Fig.

As shown in FIG. 6, the optical filter position adjusting unit of the present invention has both side faces supported by the coil-shaped actuator 20 and the elastic spring 30 disposed on both sides of the optical filter unit 12, And a power input circuit 50 for applying or cutting off power to the coil-shaped actuator 20 may be connected.

The power input circuit 50 has positive and negative poles connected to both ends of the coiled actuator 20, that is, the upper and lower ends of the shape memory alloy constituting the coiled type, A predetermined voltage is applied to the coil-shaped actuator 20 by the operation of the switch 51 mounted on the power input circuit 50 so that the variable length drive of the actuator 20 is performed.

The power input circuit 50 includes a switch 51 for applying power, a current adjusting resistor 53 and a capacitor 54 for adjusting the magnitude of the voltage of the power source 52, Type actuator 20 and the power supply wiring is connected to a power supply terminal of the printed circuit board.

When power is applied to the coil type actuator 20 through the power input circuit 50, the actuator 20 is self-heated due to electrical resistance, and when the temperature is higher than the transformation temperature, the length of the actuator 20 increases within a predetermined range. Therefore, the optical filter unit 12, which is supported on the one side of the coil-shaped actuator 20, is displaced by the variable length of the actuator 20 in the transverse direction.

At this time, the feed displacement of the coil-shaped actuator 20 is determined within a range of 0.001 to 0.7 mm, and preferably, a feed displacement of 0.3 mm is maintained.

When the supply of power to the coil type actuator 20 is interrupted by the switching of the switch 51 of the power input circuit 50, the coil type actuator 20 is cooled below the transformation temperature and shrunk to the original state At this time, the optical filter unit 12 is restored by the repulsive force of the elastic spring 30.

8 is a graph showing a modification of the coil type actuator. When the coil type actuator 20 of the present invention is heated by the power supply via the power input circuit 50 as shown in FIG. 8, And when the maximum variable displacement of the actuator 20 is reached at the point II, the power input through the power input circuit 50 connected to the actuator 20 is interrupted The stress (?) Applied to the coil-like actuator 20 is removed to reach the point III. In Fig. 8, the abscissa indicates the displacement of displacement, and the ordinate indicates stress.

As described above, the coil-shaped actuator 20 at the position III recovers the elastic force of the shrinkage deformation due to the repulsive force of the elastic spring 30 supported on the other side of the optical filter part 12, 20 to the point I, which is the variable front point.

Therefore, the coil type actuator 20 has a certain amount of stress (?) Due to self-heating from the point I to the point II by the power supply through the power input circuit 50, and the elongated elastic displacement (II ') point (Ε) from point Ⅰ to the point of recovery to the original position due to length contraction.

9 is a plan view showing an arrangement of unit pixels of a CMOS image sensor according to the present invention.

Referring to FIG. 9, each unit pixel for capturing colors of R, G, and B which are three primary colors of light is arranged in a lattice structure.

10 is a cross-sectional view showing a unit pixel of a CMOS image sensor taken along a direction a-a 'in FIG. In FIG. 10, all the RGB colors of FIG. 9 are displayed.

10, a field oxide film 101 is locally formed on a substrate 100 having a structure in which a high concentration P type (P ++) region and an epi layer P-epi are stacked. On the substrate 100, A plurality of gate electrodes including transfer gates are formed. For example, in the region below the surface of the substrate 100 aligned at one side of the transfer gate, an N-type region formed by deep ion implantation and a region in contact with the surface of the substrate 100 And a photodiode 102 (hereinafter referred to as a PD) formed of a P-type region is formed.

In this case, a high concentration N type (N +) floating diffusion region by ion implantation may be formed on the lower surface of the substrate 100 aligned on the other side of the transfer gate.

A multilayer 103 in which a plurality of metal lines and a plurality of insulating films are mixed may be formed on the upper portion where the PD 102 and the transfer gate are formed.

The plurality of metal lines connect the power line or the signal line to the unit pixel and the logic circuit and serve as a shield for preventing light from entering the area other than the PD 102. [

In addition, a plurality of inter-metal-dielectric (IMD) insulating films between metal line pre-metal dielectrics (hereinafter referred to as PMD) and metal lines under a plurality of metal lines, . As PMD and IMD, oxide film such as silicon oxide film is mainly used.

On the multilayer 103, a protective film 104 for protecting the metal line is formed. The protective film 104 includes a structure in which a thin oxide film and a thick nitride film thereon are stacked.

A first overcoating layer 105 (hereinafter referred to as OCL1) for reducing the occurrence of a step due to the formation of a metal line is formed on the protective film 104. On the OCL1 105, A color filter array 106 (hereinafter, referred to as CFA) is formed.

Yellow (Y), magenta (Mg), and cyan (Cy), which are complementary colors, may be used in addition to R (Red) G .

A second overcoat layer 107 (hereinafter referred to as OCL2) is formed on the CFA 106 in order to secure a process margin in the formation of the microlenses by reducing the step generated by the formation of the CFA 106. On the OCL2 107, And a lens 108 (Micro-Lens, hereinafter referred to as ML) is formed.

On the ML, a protective film is formed to prevent the ML from being scratched or broken. Here, the protective film is omitted.

Thus, the incident light is focused by the ML 108 and enters the PD 102. The image sensor consists of a photodiode area for sensing light, that is, a light receiving area and a logic circuit part for processing light into an electrical signal, and a 0.18 μm CMOS image sensor has a logic circuit having three or more metal lines You may need it.

In Fig. 10, the depth D from the ML 107 to the PD 102 is 5 占 퐉 to 8 占 퐉. When light passes through an arbitrary material, the refractive index changes according to the wavelength, and this is called a wavelength dependent refractive index. When the two wavelengths of light (λ1> λ2) having different wavelengths are incident on the same material, the refraction angle becomes smaller when the wavelength is shorter. A small refraction angle means that more refraction occurs. Therefore, the degree of refraction in the visible light region is in the order of blue (B)> green (G)> red (R).

10, an optical filter up-down unit 202 is disposed between the optical filter unit 300 and the formation layer of the microlens. When the thickness of the optical filter up-down unit 202 is adjusted, a distance between the optical filter unit 300 and the microlens is changed. Therefore, when the optical filter unit 300 is an infrared filter, The refractive index of the light in the infrared region longer in wavelength than the light region is changed. As a result, the filtering characteristic can be optimally determined by adjusting the thickness of the optical filter up-down portion 202.

As described above, an optimal embodiment has been disclosed in the drawings and specification. Although specific terms have been employed herein, they are used for purposes of illustration only and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. For example, without departing from the technical idea of the present invention, the internal structure or the detailed structure and the shape of the image sensing device may be variously changed and modified in different cases.

110: Image sensor
200: regulating layer
300: Optical filter
400: objective lens

Claims

An image sensor for sensing an image through a unit pixel;
A color filter layer formed on top of the image sensor for color filtering;
An optical filter position adjuster whose height is adjusted in response to an applied electrical control signal;
An optical filter layer disposed on the optical filter position adjusting unit; And
And a controller for comparing the image provided from the image sensor with a reference image and controlling the position of the optical filter layer by controlling the optical filter position adjusting unit according to the comparison result.

2. The image sensing apparatus of claim 1, wherein the optical filter controller comprises a piezoelectric element.

2. The image sensing device of claim 1, wherein the optical filter controller comprises an electroactive polymer actuator.

The apparatus of claim 1, wherein the optical filter controller comprises a coil actuator.

The apparatus of claim 1, wherein the optical filter controller comprises a gyroscope.

2. The image sensing apparatus of claim 1, wherein the optical filter layer is an infrared filter layer.

The image sensing apparatus of claim 1, wherein the optical filter layer comprises a low-pass infrared filter layer and a high-pass infrared filter layer.

2. The image sensing device of claim 1, further comprising a microlens layer between the color filter layer and the optical filter position adjustment layer.

An image sensor for sensing an image through a unit pixel;
A color filter layer formed on top of the image sensor for color filtering;
An optical filter position adjustment layer whose height is adjusted in response to an applied electrical control signal;
And an optical filter layer disposed on the optical filter position adjusting unit.

10. The image sensing device of claim 9, wherein the optical filter control layer comprises any one of a piezoelectric element, an electroactive polymer actuator, a coil actuator, and a gyroscope.

The image sensing device of claim 10, further comprising a microlens layer between the color filter layer and the optical filter position adjustment layer.

Providing an optical filter position adjustment unit between the color filter layer and the optical filter layer positioned on top of the image sensor;
Comparing an image provided from the image sensor with a pre-stored reference image; And
And controlling the position of the optical filter layer in the upper or lower direction by controlling the position of the optical filter according to the comparison result.

13. The method according to claim 12, wherein the optical filter controller is configured by a piezoelectric element, an electroactive polymer actuator, a coil actuator, and a gyroscope, and is driven by an electrical control signal.