Image sensing device

Abstract

An image sensing device including filters adjacent to each other is disclosed. The image sensing device includes: a substrate including a first photoelectric conversion element and a second photoelectric conversion element configured to generate photoelectric charges corresponding to the intensity of incident light corresponding to a first color; a first pixel including a first filter disposed above the first photoelectric conversion element to selectively transmit light corresponding to the first color; a second pixel including a second filter disposed above the second photoelectric conversion element to selectively transmit light corresponding to the first color; and a first air layer disposed between the first filter and the first photoelectric conversion element to reflect light from the first filter.

Description

Technical Field

[0001] The techniques and implementations disclosed in this patent document generally relate to an image sensing device including filters adjacent to each other. Background Art

[0002] Image sensing devices are devices that capture optical images by converting light into electrical signals using photosensitive semiconductor materials that react to light. With the development of the automotive, medical, computer and communication industries, the demand for high-performance image sensing devices is increasing in various devices such as smartphones, digital cameras, game consoles, IOT (Internet of Things), robots, security cameras and medical micro cameras.

[0003] Image sensing devices can be roughly divided into CCD (charge coupled device) image sensing devices and CMOS (complementary metal oxide semiconductor) image sensing devices. Compared with CMOS image sensing devices, CCD image sensing devices provide better image quality, but they tend to consume more power and are larger. Compared with CCD image sensing devices, CMOS image sensing devices are smaller in size and consume less power. In addition, CMOS manufacturing technology can be used to incorporate photosensitive elements and other signal processing circuits into a single chip, allowing miniaturized image sensing devices to be produced at a lower cost. For these reasons, CMOS image sensing devices are being developed for many applications including mobile devices. Summary of the invention

[0004] Various embodiments of the disclosed technology are directed to an image sensing device that can capture a high dynamic range (HDR) image from a single exposure.

[0005] According to an embodiment of the disclosed technology, an image sensing device may include: a substrate including a first photoelectric conversion element and a second photoelectric conversion element configured to generate photoelectric charges corresponding to the intensity of incident light corresponding to a first color; a first pixel including a first filter disposed above the first photoelectric conversion element to selectively transmit light corresponding to the first color; a second pixel including a second filter disposed above the second photoelectric conversion element to selectively transmit light corresponding to the first color; and a first air layer disposed between the first filter and the first photoelectric conversion element to reflect light from the first filter.

[0006] According to another embodiment of the disclosed technology, an image sensing device may include: a substrate including a first photoelectric conversion element, a second photoelectric conversion element, and a third photoelectric conversion element configured to generate photo charges corresponding to the intensity of incident light corresponding to a first color; and a filter array, which is arranged above the first photoelectric conversion element, the second photoelectric conversion element, and the third photoelectric conversion element, and is configured to include a first filter corresponding to the first photoelectric conversion element and a second filter corresponding to the second photoelectric conversion element, wherein the filter array includes a first air layer, which is arranged between the first filter and the first photoelectric conversion element to reflect light from the first filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a block diagram illustrating an example of an image sensing device based on some implementations of the disclosed technology.

[0008] Figure 2 Some implementations based on the disclosed technology are shown in Figure 1 A schematic diagram of an example of a pixel array is shown.

[0009] Figure 3 The invention is a method for implementing the disclosed technology according to the incident light including Figure 2 An example graph of the responses of high-sensitivity pixels and low-sensitivity pixels to variations in the intensity of light on an image sensor pixel is shown.

[0010] Figure 4 The following are some examples of implementations of the disclosed technology. Figure 2 Schematic diagram of examples of high-sensitivity pixels and low-sensitivity pixels in a pixel array shown.

[0011] Figure 5 is a diagram showing some implementations based on the disclosed technology. Figure 4 A cross-sectional view of an example of an image sensor pixel taken along the first line is shown.

[0012] Figure 6 Some implementations based on the disclosed technology are shown in Figure 1 A schematic diagram of another example of a pixel array is shown.

[0013] Figure 7 The invention is a method for implementing the disclosed technology according to the incident light including Figure 6 Graphs of examples of responses of high sensitivity pixels, medium sensitivity pixels, and low sensitivity pixels as the intensity of light on an image sensor pixel varies are shown.

[0014] Figure 8 Some implementations based on the disclosed technology are shown in Figure 6 A schematic diagram of an example of arrangement of high-sensitivity pixels, medium-sensitivity pixels, and low-sensitivity pixels in a pixel array shown.

[0015] Fig. 9 is a diagram showing some implementations based on the disclosed technology. Figure 8 A cross-sectional view of an example of an image sensor pixel taken along the second line shown.

[0016] Symbols of components in the figure

[0017] 200: Substrate

[0018] 210: Multiple photoelectric conversion elements

[0019] 310 and 330: First filter

[0020] 311 and 331: Low refractive index layer

[0021] 311 and 331: Air layer

[0022] 320 and 340: Second filter

[0023] 350: Multiple micro lenses

[0024] 360: Multiple optical grid structures DETAILED DESCRIPTION

[0025] This patent document provides implementations and examples of image sensing devices including filters adjacent to each other. In some implementations of the disclosed technology, the image sensing device can obtain a high dynamic range (HDR) image by capturing an image only once or from a single exposure. The disclosed technology provides various implementations of image sensing devices that can obtain a high dynamic range (HDR) image without a complex structure.

[0026] Hereinafter, various embodiments will be described with reference to the accompanying drawings. However, it should be understood that the disclosed technology is not limited to a specific embodiment, but includes various modifications, equivalents and / or substitutions of the embodiments. The embodiments of the disclosed technology can provide various effects that can be directly or indirectly recognized by the disclosed technology.

[0027] Figure 1 is a block diagram illustrating an image sensing device according to an embodiment of the disclosed technology.

[0028] Reference Figure 1 , the image sensing device 100 may include a pixel array 110, a row driver 120, a correlated double sampler (CDS) 130, an analog-to-digital converter (ADC) 140, an output buffer 150, a column driver 160, and a timing controller 170. For example only Figure 1Although the components of image sensing device 100 are shown, this patent document encompasses numerous other alterations, substitutions, variations, modifications, and modifications.

[0029] The pixel array 110 may include a plurality of unit imaging pixels arranged in rows and columns. In one example, the plurality of unit imaging pixels may be arranged in a two-dimensional pixel array including rows and columns. In another example, the plurality of unit imaging pixels may be arranged in a three-dimensional pixel array. The plurality of unit pixels may convert optical signals into electrical signals based on unit pixels or based on pixel groups, wherein the unit pixels in the pixel groups share at least specific internal circuits. The pixel array 110 may receive a drive signal including a row selection signal, a pixel reset signal, and a transfer signal from the row driver 120. Upon receiving the drive signal, the corresponding imaging pixel in the pixel array 110 may be enabled to perform operations corresponding to the row selection signal, the pixel reset signal, and the transfer signal.

[0030] The row driver 120 may enable the pixel array 110 to perform specific operations on the imaging pixels in the corresponding row based on the command and control signals provided by the controller circuit such as the timing controller 170. In some implementations, the row driver 120 may select one or more imaging pixels arranged in one or more rows of the pixel array 110. The row driver 120 may generate a row selection signal to select one or more rows among the multiple rows. The row driver 120 may sequentially enable a pixel reset signal for resetting the imaging pixels corresponding to at least one selected row and a transmission signal for the pixels corresponding to the at least one selected row. Therefore, as analog signals generated by the respective imaging pixels of the selected row, the reference signal and the image signal may be sequentially transmitted to the CDS 130. The reference signal may be an electrical signal provided to the CDS 130 when the sensing node (e.g., the floating diffusion node) of the imaging pixel is reset, and the image signal may be an electrical signal provided to the CDS 130 when the photocharge generated by the imaging pixel is accumulated in the sensing node.

[0031] CMOS image sensors may use correlated double sampling (CDS) to remove undesired offset values ​​(called fixed pattern noise) of pixels by sampling the pixel signal twice to remove the difference between the two samples. In one example, correlated double sampling (CDS) may remove undesired offset values ​​of pixels by comparing the pixel output voltages obtained before and after the photocharges generated by the incident light are accumulated in the sensing node, so that only the pixel output voltage based on the incident light may be measured. In some embodiments of the disclosed technology, CDS 130 may sequentially sample and maintain the voltage levels of the reference signal and the image signal provided to each of the plurality of column lines from the pixel array 110. That is, CDS 130 may sample and maintain the voltage levels of the reference signal and the image signal corresponding to each column of the pixel array 110.

[0032] In some implementations, the CDS 130 may transmit the reference signal and the image signal of each column to the ADC 140 as a correlated double sampling signal based on a control signal from the timing controller 170 .

[0033] ADC 140 is used to convert the analog CDS signal into a digital signal. In some implementations, ADC 140 may be implemented as a ramp comparison ADC. The ramp comparison ADC may include a comparator circuit for comparing the analog pixel signal with a reference signal such as a ramp signal that ramps up or down, and a timer counts until the voltage of the ramp signal matches the analog pixel signal. In some embodiments of the disclosed technology, ADC 140 may convert the correlated double sampling signal generated by CDS 130 for each column into a digital signal and output the digital signal. ADC 140 may perform counting operations and calculation operations based on the correlated double sampling signal of each column and the ramp signal provided from the timing controller 170. In this way, ADC 140 can eliminate or reduce noise (e.g., reset noise) originating from imaging pixels when generating digital image data.

[0034] The ADC 140 may include a plurality of column counters. Each column of the pixel array 110 is connected to the column counter, and image data may be generated by converting a correlated double sampling signal received from each column into a digital signal using the column counter. In another embodiment of the disclosed technology, the ADC 140 may include a global counter to convert a correlated double sampling signal corresponding to a column into a digital signal using a global code provided from the global counter.

[0035] The output buffer 150 may temporarily hold the column-based image data provided from the ADC 140 to output the image data. In one example, the image data provided from the ADC 140 to the output buffer 150 may be temporarily stored in the output buffer 150 based on a control signal of the timing controller 170. The output buffer 150 may provide an interface to compensate for a data rate difference or a transmission rate difference between the image sensing device 100 and other devices.

[0036] The column driver 160 may select a column of the output buffer upon receiving a control signal from the timing controller 170, and sequentially output the image data temporarily stored in the selected column of the output buffer 150. In some implementations, upon receiving an address signal from the timing controller 170, the column driver 160 may generate a column selection signal based on the address signal and select a column of the output buffer 150, thereby outputting the image data from the selected column of the output buffer 150 as an output signal.

[0037] The timing controller 170 may control operations of the row driver 120 , the ADC 140 , the output buffer 150 , and the column driver 160 .

[0038] The timing controller 170 may provide clock signals required for the operation of the various components of the image sensing device 100, control signals for timing control, and address signals for selecting rows or columns to the row driver 120, the column driver 160, and the output buffer 150. In an embodiment of the disclosed technology, the timing controller 170 may include a logic control circuit, a phase-locked loop (PLL) circuit, a timing control circuit, a communication interface circuit, and the like.

[0039] Figure 2 Some implementations based on the disclosed technology are shown in Figure 1 A schematic diagram of an example of a pixel array 110A is shown.

[0040] Reference Figure 2 , the pixel array 110A is Figure 1 An example of a pixel array 110 is shown. Figure 2 Pixel array 110A is shown as including only two types of image sensor pixels, i.e., high sensitivity pixels (HPX) and low sensitivity pixels (LPX), but pixel array 110A may include other types of image sensor pixels. In some implementations, each pixel included in pixel array 110A may be a high sensitivity pixel (HPX) or a low sensitivity pixel (LPX). The number of high sensitivity pixels (HPX) and the number of low sensitivity pixels (LPX) included in pixel array 110A may vary.

[0041] A high sensitivity pixel (HPX) may be configured to generate a greater response to an increase in the intensity of incident light than other types of pixels. Here, the response may include a charge or pixel signal generated by the high sensitivity pixel (HPX) based on the intensity of the incident light. In one example, a high sensitivity pixel (HPX) may include a pixel that exhibits a relatively high sensitivity to incident light.

[0042] A low sensitivity pixel (LPX) may include a pixel configured to generate less response to an increase in the intensity of incident light. In other words, a low sensitivity pixel (LPX) may include a pixel that exhibits relatively low sensitivity to incident light.

[0043] Figure 3 The invention is a method for implementing the disclosed technology according to the incident light including Figure 2 Graphs showing examples of the responses of high sensitivity pixels (HPX) and low sensitivity pixels (LPX) to variations in the illumination or intensity of light on an image sensor pixel.

[0044] Figure 3 Plots showing the response of a high sensitivity pixel (HPX) and the response of a low sensitivity pixel (LPX) versus the illumination or intensity of incident light applied to the corresponding pixel.

[0045] Here, the response may have a signal-to-noise ratio (SNR) limit (eg, an SNR threshold level) and a saturation level.

[0046] The signal-to-noise ratio (SNR) limit may include a threshold value of a response that may satisfy a predetermined reference SNR. A response less than the SNR limit may be an invalid response that may not satisfy the reference SNR, and a response greater than the SNR limit may be a valid response that may satisfy the reference SNR. The reference SNR may be determined experimentally in consideration of the characteristics of the image sensing device 100.

[0047] The saturation level may include a maximum response value indicating the intensity of the incident light. The saturation level may be determined based on how efficiently a pixel (e.g., a photoelectric conversion element) can convert the intensity of the incident light into photocharges and how efficiently a floating diffusion (FD) region can convert the photocharges into electrical signals. As the intensity of the incident light increases, the response may increase according to the intensity of the incident light until a saturation level is reached. However, even if the intensity of the incident light increases after the response has reached the saturation level, the response does not increase beyond the saturation level and stays at the saturation level.

[0048] If the effective response of each pixel is defined as a response that can indicate the intensity of the incident light while satisfying the reference SNR, the range of the intensity of the incident light corresponding to the effective response of each pixel can be defined as the dynamic range of each pixel. For example, the dynamic range of a pixel may include the range of the intensity of the incident light to which the pixel can have an effective response.

[0049] The response of the high sensitivity pixel (HPX) may increase with a relatively higher slope in response to an increase in the intensity of the incident light. After reaching the saturation level, the response of the high sensitivity pixel (HPX) may have a level corresponding to the saturation level regardless of the intensity of the incident light.

[0050] The response of the low sensitivity pixel (LPX) may increase with a relatively lower slope in response to an increase in the intensity of the incident light. After reaching the saturation level, the response of the low sensitivity pixel (LPX) may have a level corresponding to the saturation level regardless of the intensity of the incident light.

[0051] like Figure 3 As shown, the minimum value of the dynamic range of the high-sensitivity pixel (HPX) may be smaller than the minimum value of the dynamic range of the low-sensitivity pixel (LPX), and the maximum value of the dynamic range of the high-sensitivity pixel (HPX) may be smaller than the maximum value of the dynamic range of the low-sensitivity pixel (LPX). Therefore, in a low illumination range where the intensity of the incident light is relatively small, the high-sensitivity pixel (HPX) may be more appropriately used to sense the intensity of the incident light. In a high illumination range where the intensity of the incident light is relatively large, the low-sensitivity pixel (LPX) may be more appropriately used to sense the intensity of the incident light.

[0052] A high dynamic range (HDR) may be obtained using both the response of a high sensitivity pixel (HPX) suitable for a low illumination range and the response of a low sensitivity pixel (LPX) suitable for a high illumination range. In other words, compared to using only one of the high sensitivity pixel (HPX) and the low sensitivity pixel (LPX), the disclosed technology may be implemented in some embodiments to use both the high sensitivity pixel (HPX) and the low sensitivity pixel (LPX), thereby allowing the pixel array 110A to have a high dynamic range (HDR) corresponding to a specific range from the minimum value of the HPX dynamic range to the maximum value of the LPX dynamic range. To this end, at least a portion of the HPX dynamic range and at least a portion of the LPX dynamic range may overlap with each other.

[0053] When synthesizing a high dynamic range (HDR) image corresponding to a high dynamic range (HDR) using high sensitivity pixels (HPX) and low sensitivity pixels (LPX), the disclosed technology may be implemented in some embodiments to synthesize the HDR image by calculating (e.g., summing) the HPX response and the LPX response, and / or forming an image based on the HPX response at a low illumination level and an image based on the LPX response at a high illumination level.

[0054] In the image sensing device 100 , high-sensitivity pixels (HPX) and low-sensitivity pixels (LPX) are simultaneously arranged in the pixel array 110A, so that the image sensing device 100 can synthesize an HDR image using an image acquired by only one exposure.

[0055] Figure 4 The following are some examples of implementations of the disclosed technology. Figure 2 Schematic diagram of examples of high sensitivity pixels (HPX) and low sensitivity pixels (LPX) in a pixel array shown.

[0056] Reference Figure 4 , the pixel array 110A-1 includes high-sensitivity pixels (HPX) and low-sensitivity pixels (LPX) arranged in a (4×4) matrix array including 4 rows and 4 columns. Although for the convenience of description, Figure 4 The pixel array 110A-1 is shown as including only 16 pixels, but the pixel array 110A-1 may include more than 16 pixels. For example, those 16 pixels may be repeatedly arranged in the row direction and the column direction of the pixel array 110A-1.

[0057] The pixel array 110A-1 may include first to fourth pixel groups. Each pixel group includes a (2×2) matrix array.

[0058] Each of the first pixel group and the fourth pixel group may include a low-sensitivity green pixel (G L) and three high-sensitivity green pixels (G H ). The first pixel group and the fourth pixel group may be arranged diagonally in the row direction or the column direction of the pixel array 110A-1. In this case, the low-sensitivity green pixels (G L ) may include a low-sensitivity pixel (LPX) that generates a pixel signal indicating the light intensity of a wavelength range corresponding to green light. A high-sensitivity green pixel (G H ) may include a high-sensitivity pixel (HPX) that generates a pixel signal indicating the intensity of light in a wavelength range corresponding to green light.

[0059] The second pixel group may be disposed to the right of the first pixel group and may include a low-sensitivity red pixel (R L ) and three high-sensitivity red pixels (R H ). Low sensitivity red pixel (R L ) may include a low-sensitivity pixel (LPX) that generates a pixel signal indicating the light intensity of a wavelength range corresponding to red light. A high-sensitivity green pixel (R H ) may include a high-sensitivity pixel (HPX) that generates a pixel signal indicating the intensity of light in a wavelength range corresponding to red light.

[0060] The third pixel group may be disposed below the first pixel group and may include a low-sensitivity blue pixel (B L ) and three high-sensitivity blue pixels (B H ). Low-sensitivity blue pixel (B L ) may include a low sensitivity pixel (LPX) that generates a pixel signal indicating the light intensity of a wavelength range corresponding to blue light. A high sensitivity blue pixel (B H ) may include a high-sensitivity pixel (HPX) that generates a pixel signal indicating the intensity of light in a wavelength range corresponding to blue light.

[0061] although Figure 4 The low sensitivity pixel (LPX) is shown as being disposed at a position corresponding to the upper left end of the (2×2) matrix in each of the first to fourth pixel groups, but it should be noted that the low sensitivity pixel (LPX) may also be disposed at other positions in other implementations. In addition, the number of low sensitivity pixels (LPX) included in each of the first to fourth pixel groups may be set to 2 or 3.

[0062] Each of the first to fourth pixel groups may include four pixels having the same color, and the first to fourth pixel groups may be arranged in a Bayer pattern. Such an arrangement structure may be defined as a quaternary Bayer pattern structure.

[0063] Figure 5 is a diagram showing some implementations based on the disclosed technology. Figure 4A cross-sectional view of an example of an image sensor pixel taken along the first line AA′ is shown.

[0064] In more detail, Figure 5 It is shown along Figure 4 The cross-sectional view 110A-2 of the pixel taken along the first line AA′ is shown.

[0065] The cross-sectional view 110A-2 includes a substrate 200 and a light receiving layer 300 disposed above the substrate 200. In addition, the cross-sectional view 110A-2 may include pixels G continuously disposed along the first line AA′. L , G H , R L and R H .

[0066] The substrate 200 may include a top surface and a bottom surface facing away from each other. For ease of description, the bottom surface of the substrate 200 may be defined as the front side, and the top surface of the substrate 200 may be defined as the back side. In one example, the substrate 200 may be a P-type or N-type bulk substrate. In another example, the substrate 200 may be a substrate formed by growing a P-type or N-type epitaxial layer on a P-type bulk substrate. In another example, the substrate 200 may be a substrate formed by growing a P-type or N-type epitaxial layer on an N-type bulk substrate.

[0067] The substrate 200 may include a plurality of photoelectric conversion elements 210. The photoelectric conversion elements 210 may be disposed in the pixels G, L , G H , R L and R H In some implementations, the photoelectric conversion element 210 may be formed by stacking a plurality of doped regions. In this case, the lower doped region may be formed by implanting N-type ions. + ions, and the upper doped region can be formed by implanting N - ions. The photoelectric conversion element 210 may be a light receiving area that is large enough to increase the fill factor associated with the light receiving (Rx) efficiency. In some implementations, the photoelectric conversion element 210 may be a light receiving area that is large enough to increase the fill factor associated with the light receiving (Rx) efficiency. L , G H , R L , R H ) may be formed to be etched at a first depth in a vertical direction so that the device isolation layer may electrically or optically isolate adjacent pixels from each other.

[0068] The photocharge accumulated in the photoelectric conversion element 210 may be converted into a pixel signal and the pixel signal may be transmitted to a column line by a readout circuit connected to the photoelectric conversion element 210. In some implementations, the readout circuit may include a floating diffusion (FD) node, a transfer transistor, a reset transistor, a source follower transistor, and a select transistor.

[0069] The floating diffusion (FD) node may include a region configured to receive photocharges from the photoelectric conversion element 210 and accumulate the photocharges therein. The transfer transistor may transfer the photocharges accumulated in the photoelectric conversion element 210 to the floating diffusion (FD) node in response to a transmission (Tx) signal received from the row driver 120. The reset transistor may reset the floating diffusion (FD) node to a reset voltage (e.g., a power supply voltage) in response to a pixel reset signal received from the row driver 120. The source follower transistor may convert the voltage of the floating diffusion (FD) node connected to its gate terminal into an electrical signal, and may output the electrical signal to the selection transistor. The selection transistor may send the electrical signal received from the source follower transistor to the column line in response to a row selection signal received from the row driver 120. Here, the electrical signal sent by the selection transistor to the column line may be used as a pixel signal.

[0070] The light receiving layer 300 may receive light incident on the image sensing device 100 and the incident light reaches the substrate 200. The light receiving layer 300 may include first filters 310 and 330, low refractive index layers such as regions 311 and 331 filled with air as air layers 311 and 331, second filters 320 and 340, a plurality of micro lenses 350, and a plurality of optical grating structures 360.

[0071] The first filter 310 may be disposed at a corresponding pixel (G L ), and the first filter 330 may be disposed above the corresponding pixel (R L ) above. The second filters 320 and 340 may be respectively disposed at the corresponding pixels G H and R H In some implementations, each second filter 320 may be disposed above a corresponding pixel (G H ), and each second filter 340 may be disposed above a corresponding pixel (R H) above. The first optical filters 310 and 330 and the second optical filters 320 and 340 may be formed between the optical grating structures 360 adjacent to each other on the upper portion of the substrate 200, and may selectively transmit light of a specific wavelength band (e.g., red light, green light, blue light, magenta light, yellow light, cyan light, infrared (IR) light). In one example, each filter may correspond to light of a specific wavelength band. For example, each of the first optical filters 310 and 330 and the second optical filters 320 and 340 may include a colored photosensitive material corresponding to a specific color. As another example, each of the first optical filters 310 and 330 and the second optical filters 320 and 340 may include thin film layers arranged alternately. The filters are arranged in a filter array corresponding to pixels arranged in rows and columns in a matrix array.

[0072] exist Figure 5 In the embodiment, each of the first filter 310 and the second filter 320 may be a green filter that selectively transmits light of a wavelength band corresponding to green. In addition, the first filter 310 may be disposed in a low-sensitivity green pixel (G L ), and the second filter 320 may be disposed in a high-sensitivity green pixel (G H )middle.

[0073] exist Figure 5 In the embodiment, each of the first filter 330 and the second filter 340 may be a red filter that selectively transmits light of a wavelength band corresponding to red. In addition, the first filter 330 may be disposed at a low-sensitivity red pixel (R L ), and the second filter 340 may be disposed in a high-sensitivity red pixel (R H )middle.

[0074] In some implementations of the disclosed technology, the filter corresponding to the low-sensitivity pixel includes a low refractive index layer such as an air layer. In one example, the selected filter can be positioned to be spaced apart from the corresponding underlying photoelectric conversion element to form an air layer that receives light passing through the filter. For example, Figure 5As shown, the first optical filter 310 may include an air layer 311, and the first optical filter 330 may include an air layer 331. The air layer 311 may be disposed below the first optical filter, and the air layer 331 may be disposed below the first optical filter 330. For example, the air layer 311 may be disposed between the first optical filter 310 and the photoelectric conversion element 210, and the air layer 331 may be disposed between the first optical filter 330 and the photoelectric conversion element 210. The air layers 311 and 331 may be formed above the top surface of the substrate 200. The bottom surface of the first optical filter 310 may be connected to the top surface of the air layer 311, and the bottom surface of the first optical filter 330 may be connected to the top surface of the air layer 331. The bottom surface of the second optical filter 320 may be connected to the top surface of the substrate 200, and the bottom surface of the second optical filter 340 may be connected to the top surface of the substrate 200. Each of the air layers 311 and 331 may be formed between the optical grating structures 360. The height of each of the air layers 311 and 331 may be relatively greater than the optical lattice structure 360, the height of the air layer 311 may be lower than the first optical filter 310, and the height of the air layer 331 may be lower than the first optical filter 330. Each of the air layers 311 and 331 may include a low refractive index layer, for example, a layer including a hollow or void portion (for example, a portion filled with air) formed in the first optical filters 310 and 330. For example, the air layer 311 may be formed by filling the hollow in the first optical filter 310 with air, and the air layer 331 may be formed by filling the hollow in the first optical filter 330 with air.

[0075] Each filter may absorb a relatively small amount of light of a selected wavelength band to be transmitted, and may absorb a relatively large amount of light of a wavelength band other than the selected wavelength band, so that the filter may selectively transmit light corresponding to the selected wavelength band. In some implementations of the disclosed technology, the combined thickness of the first filter 310 and the air layer 311 and the combined thickness of the first filter 330 and the air layer 331 may be the same as the thickness of the second filters 320 and 340. The combination of the first filter 310 and the air layer 311 and the combination of the first filter 330 and the air layer 331 correspond to low-sensitivity pixels (e.g., low-sensitivity green pixels (G L ), low-sensitivity red pixels (R L )).

[0076] In these designs in which low refractive index layers or air layers 311 and 331 are formed in the optical filters 310 and 330, respectively, light incident on the optical filters 310 and 330 that enters the lower air layers 311 and 331 when transmitting through the optical filters 310 and 330 may be partially or completely reflected by the interface of the air layers 311 and 331 and the surrounding layers having a higher refractive index than the air layers 311 and 331, and such reflection in the air layers 311 and 331 may increase the total reflection of the incident light. Therefore, the air layers 311 and 331 formed in the optical filters 310 and 330 may reduce the total transmittance of the incident light of the selected wavelength band of the optical filters 310 and 330. The transmittance may be used to obtain information on the ratio of the light incident on the optical filters 310 and 330 to the light transmitted through the optical filters 310 and 330.

[0077] Therefore, the transmittance of the first optical filter 310 or 330 including the air layer 311 or 331 in the selected wavelength band of the optical filter 310 or 330 may be lower than the transmittance of the second optical filter 320 or 340 not including the low refractive index layer or the air layer 311 or 331, and thus a smaller refractive index difference is exhibited at the interface thereof. That is, when a light beam having the same intensity is incident on the first optical filters 310 and 330 and the second optical filters 320 and 340, the intensity of the light of the selected wavelength band having passed through the first optical filters 310 and 330 may be smaller than the intensity of the light of the selected wavelength band having passed through the second optical filters 320 and 340.

[0078] In addition, the intensity of light corresponding to the selected wavelength band passing through the first optical filters 310 and 330 may increase with a relatively lower slope in response to an increase in the intensity of the incident light. The intensity of light corresponding to the transmission wavelength band passing through the second optical filters 320 and 340 may increase with a relatively higher slope in response to an increase in the intensity of the incident light.

[0079] The intensity of light corresponding to the transmission wavelength band that has passed through each of the first optical filters 310 and 330 and the second optical filters 320 and 340 can be converted into a pixel signal by the photoelectric conversion element 210 and the readout circuit. As a result, the response of the pixel including the first optical filter 310 or 330 can follow Figure 3 The response of the low sensitivity pixel (LPX) shown, and the response of the pixel including the second filter 320 or 340 may follow Figure 3 The response of the high sensitivity pixel (HPX) is shown.

[0080] Therefore, a pixel including the first filter 310 or 330 may correspond to a low sensitivity pixel (LPX), and a pixel including the second filter 320 or 340 may correspond to a high sensitivity pixel (HPX).

[0081] The image sensing device 100 based on some implementations of the disclosed technology may include air layers 311 and 331, which are inserted into the first filters 310 and 330 to allow the incident light applied to the first filter 310 and the incident light applied to the first filter 330 to have different reflectivities, so that low sensitivity pixels (LPX) and high sensitivity pixels (HPX) can be implemented in one pixel array, so that the image sensing device 100 can form a high dynamic range (HDR) image using only one image.

[0082] As an example, in the case of including a low-sensitivity red pixel (R L ) is inserted into the first filter 310, and an air layer 311 is inserted into the low-sensitivity blue pixel (B L ) is inserted into the first filter 330, and an air layer 331 is inserted into the first filter 330 in the high-sensitivity green pixel (G H ), high-sensitivity red pixel (R H ) and high-sensitivity blue pixels (B H ) does not include the air layers 311 and 331 in the second filters 320 and 340.

[0083] The microlens 350 may be formed above the optical filters 310 to 340 to condense incident light, thereby increasing light receiving (Rx) efficiency of the photoelectric conversion element 210 .

[0084] Each optical grid structure 360 ​​may be formed between adjacent optical filters 310, 320, 330, and 340 at an upper portion of the substrate 200. The optical grid structure 360 ​​may prevent light incident on the optical filters 310 to 340 from interfering with adjacent pixels, thereby minimizing optical crosstalk between adjacent pixels.

[0085] Figure 6 Some implementations based on the disclosed technology are shown in Figure 1 A schematic diagram of another example of a pixel array is shown.

[0086] Reference Figure 6 , the pixel array 110B is Figure 1 An example of a pixel array 110 is shown. Figure 6Pixel array 110B is shown as including three types of image sensor pixels, i.e., high sensitivity pixels (HPX), medium sensitivity pixels (MPX), and low sensitivity pixels (LPX), but pixel array 110B may include other types of image sensor pixels. In some implementations, each pixel included in pixel array 110B may be a high sensitivity pixel (HPX), a medium sensitivity pixel (MPX), or a low sensitivity pixel (LPX). The number of high sensitivity pixels (HPX), the number of medium sensitivity pixels (MPX), and the number of low sensitivity pixels (LPX) included in pixel array 110B may vary.

[0087] Figure 6 The high sensitivity pixels (HPX) and low sensitivity pixels (LPX) shown are Figure 2 Those of are substantially the same, so for ease of description, a detailed description thereof will be omitted herein. The medium sensitivity pixel (MPX) may be configured to generate a greater response to an increase in incident light intensity than the low sensitivity pixel (LPX) and to generate a smaller response than the high sensitivity pixel (HPX).

[0088] Figure 7 The invention is a method for implementing the disclosed technology according to the incident light including Figure 6 Graphs of examples of responses of image sensor pixels as light intensity varies for high sensitivity pixels (HPX), medium sensitivity pixels (MPX), and low sensitivity pixels (LPX) are shown.

[0089] Figure 7 Plots showing the response of a high sensitivity pixel (HPX), the response of a medium sensitivity pixel (MPX), and the response of a low sensitivity pixel (LPX) versus the illumination or intensity of incident light applied to the corresponding pixel. Figure 7 The HPX response and LPX response shown are Figure 3 Those of are substantially the same, and thus for the convenience of description, a detailed description thereof will be omitted herein.

[0090] The response of the medium sensitivity pixel (MPX) shows a characteristic that the amount of increase in response caused by an increase in incident light intensity is higher than that of the low sensitivity pixel (LPX) and lower than that of the high sensitivity pixel (HPX). In some implementations, the response of the medium sensitivity pixel (MPX) may increase with a slope higher than that of the low sensitivity pixel (LPX) and lower than that of the high sensitivity pixel (HPX) in response to an increase in incident light intensity. The response of the medium sensitivity pixel (MPX) may reach a saturation level and thus may have a level corresponding to the saturation level regardless of the incident light intensity.

[0091] like Figure 7 As shown, in order to Figure 3To improve the high dynamic range (HDR), the amount of increase in response caused by an increase in the incident light intensity of the low sensitivity pixel (LPX) may be reduced, or the amount of increase in response caused by an increase in the incident light intensity of the high sensitivity pixel (HPX) may be increased. In this case, the minimum value of the dynamic range of the low sensitivity pixel (LPX) may exceed the maximum value of the dynamic range of the high sensitivity pixel (HPX). For example, a gap may occur between the LPX dynamic range and the HPX dynamic range. As a result, the image sensing device 100 may not be able to obtain an effective response at an illumination level corresponding to such a gap.

[0092] However, the dynamic range of the medium sensitivity pixel (MPX), whose increase in response due to an increase in incident light intensity is higher than that of the low sensitivity pixel (LPX) and lower than that of the high sensitivity pixel (HPX), may have a maximum value higher than the minimum value of the dynamic range of the low sensitivity pixel (LPX), and may have a minimum value lower than the maximum value of the HPX dynamic range. As a result, the MPX dynamic range may cover the gap between the LPX dynamic range and the HPX dynamic range.

[0093] The high dynamic range (HDR) can be implemented using the response of a high sensitivity pixel (HPX) suitable for a low illumination range, the response of a medium sensitivity pixel (MPX) suitable for a medium illumination range, and a range of a low sensitivity pixel (LPX) suitable for a low illumination range. In other words, compared to using high sensitivity pixels (HPX) and low sensitivity pixels (LPX), the disclosed technology can be implemented in some embodiments to use high sensitivity pixels (HPX), medium sensitivity pixels (MPX), and low sensitivity pixels (LPX) at the same time, thereby allowing the pixel array 110B to have a high dynamic range (HDR) corresponding to a specific range from the minimum value of the HPX dynamic range to the maximum value of the LPX dynamic range without causing a gap between the HPX dynamic range and the LPX dynamic range. To this end, at least a portion of the HPX dynamic range, at least a portion of the MPX dynamic range, and at least a portion of the LPX dynamic range can overlap with each other.

[0094] When synthesizing an HDR image corresponding to a high dynamic range (HDR) using high-sensitivity pixels (HPX), medium-sensitivity pixels (MPX), and low-sensitivity pixels (LPX), the disclosed technology can be implemented in some embodiments to synthesize the HDR image by calculating (e.g., summing) the HPX response, the MPX response, and the LPX response, and / or forming an image based on the HPX response at a low illumination level, an image based on the MPX response at a medium illumination level, and an image based on the LPX response at a high illumination level.

[0095] In the image sensing device 100 , high sensitivity pixels (HPX), medium sensitivity pixels (MPX), and low sensitivity pixels (LPX) are simultaneously arranged in the pixel array 110B, so that the image sensing device 100 can synthesize an HDR image using an image acquired by only one exposure.

[0096] Figure 8 Some implementations based on the disclosed technology are shown in Figure 6 Schematic diagram of an example of arrangement of high-sensitivity pixels (HPX), medium-sensitivity pixels (MPX), and low-sensitivity pixels (LPX) in a pixel array shown.

[0097] Reference Figure 8 , the pixel array 110B-1 includes high-sensitivity pixels (HPX), medium-sensitivity pixels (MPX), and low-sensitivity pixels (LPX) arranged in a (4×4) matrix array including 4 rows and 4 columns. Although for the convenience of description, Figure 8 The pixel array 110B-1 is shown to include only 16 pixels, but the pixel array 110B-1 may include more than 16 pixels. For example, the 16 pixels may be repeatedly arranged in the row direction and the column direction of the pixel array 110B-1.

[0098] The pixel array 110B-1 may include fifth to eighth pixel groups. Each pixel group includes a (2×2) matrix array.

[0099] Each of the fifth pixel group and the eighth pixel group may include a low-sensitivity green pixel (G L ), a medium-sensitivity green pixel (G M ) and two high-sensitivity green pixels (G H ). The fifth pixel group and the eighth pixel group may be arranged diagonally in the row direction or the column direction of the pixel array 110B-1. In this case, the medium-sensitivity green pixel (G M ) may include a medium-sensitivity pixel (MPX) that generates a pixel signal indicating the intensity of light in a wavelength range corresponding to green light.

[0100] The sixth pixel group may be disposed on the right side of the fifth pixel group and may include a low-sensitivity red pixel (R L ), a medium-sensitivity red pixel (R M ) and two high-sensitivity red pixels (R H ). Medium sensitivity red pixel (R M ) may include a medium-sensitivity pixel (MPX) that generates a pixel signal indicating the intensity of light in a wavelength range corresponding to red light.

[0101] The seventh pixel group may be disposed below the fifth pixel group and may include a low-sensitivity blue pixel (BL ), a medium-sensitivity blue pixel (B M ) and two high-sensitivity blue pixels (B H ). Medium sensitivity blue pixel (B M ) may include a medium-sensitivity pixel (MPX) that generates a pixel signal indicating the intensity of light in a wavelength range corresponding to blue light.

[0102] although Figure 8 It is shown that the low-sensitivity pixel (LPX) is set at a position corresponding to the upper left end of the (2×2) matrix in each of the fifth to eighth pixel groups and the medium-sensitivity pixel (MPX) is set at a position corresponding to the upper right end of the (2×2) matrix in each of the fifth to eighth pixel groups, but it should be noted that in other implementations, the low-sensitivity pixel (LPX) and the medium-sensitivity pixel (MPX) may also be set at other positions. In addition, the number of low-sensitivity pixels (LPX) included in each of the fifth to eighth pixel groups or the number of medium-sensitivity pixels (MPX) included in each of the fifth to eighth pixel groups may be set to 2.

[0103] Fig. 9 is a diagram showing some implementations based on the disclosed technology. Figure 8 A cross-sectional view of an example of an image sensor pixel taken along the second line BB′ is shown.

[0104] In more detail, Fig. 9 It is shown along Figure 8 A cross-sectional view 110B-2 of pixels taken along the second line BB′ and included in the fifth pixel group and the sixth pixel group is shown.

[0105] The cross-sectional view 110B-2 includes a substrate 400 and a light receiving layer 500 disposed above the substrate 400. In addition, the cross-sectional view 110B-2 may include pixels G continuously disposed along a second line BB′. L , G H , G M , R L and R H . Figure 8 The structure and function of the substrate 400 and the light receiving layer 500 shown in FIG. Figure 5 The structures and functions of the illustrated substrate 200 and the light receiving layer 300 are substantially the same, and thus a detailed description thereof will be omitted herein for the sake of convenience of description.

[0106] The light receiving layer 500 may include a plurality of first filters 510 and 540, a plurality of second filters 520 and 550, a plurality of third filters 530 and 560, a plurality of air layers 511, 531, 541, and 561, a plurality of micro lenses 570, and a plurality of optical grating structures 580. Figure 5 Unlike the illustrated light receiving layer 300 , the light receiving layer 500 may further include third filters 530 and 560 .

[0107] The air layer 511, 531, 541 or 561 may be provided between the photoelectric conversion element 410 and the optical filter 510, 530, 540 or 560. Each of the air layers 511, 531, 541 and 561 may be formed over the top surface of the substrate 400. The bottom surface of each of the optical filters 510, 530, 540 and 560 may be in contact with or connected to the top surface of each of the air layers 511, 531, 541 and 561. The bottom surface of each of the second optical filters 520 and 550 may be in contact with or connected to the top surface of the substrate 400. The air layers 531 and 561 may include the same material and function as the air layers 511 and 541, but each of the air layers 531 and 561 may have a thickness smaller than that of each of the air layers 511 and 541.

[0108] Each of the air layers 531 and 561 may include a low refractive index material such as air, and may include a hollow or void portion formed in the third optical filters 530 and 560. In this case, the air layer 531 may be disposed between the medium sensitivity green pixel (G M ). In addition, the air layer 561 may be disposed in a medium-sensitivity red pixel (R M )middle.

[0109] The thickness T2 of each of the air layers 511 and 541 may be smaller than the thickness of each of the first optical filters 510 and 540, the thickness of each of the second optical filters 520 and 550, or the thickness of each of the third optical filters 530 and 560. The thickness T3 of each of the air layers 531 and 561 may be smaller than the thickness T2 of each of the air layers 511 and 541.

[0110] The transmittance of the third filter 530 or 560 including the air layer 531 or 561 in the selected wavelength band may be higher than the transmittance of the first filter 510 or 540 including the air layer 511 or 541 in the selected wavelength band, and may be lower than the transmittance of the second filter 520 or 550 not including the air layer 511, 531, 541 or 561 in the selected wavelength band.

[0111] When a light beam having the same intensity is incident on the first filters 510 and 540, the second filters 520 and 550, and the third filters 530 and 560, the intensity of the light of the selected wavelength band passing through the third filters 530 and 560 may be greater than the intensity of the light having passed through the first filters 510 and 540, and may be less than the intensity of the light passing through the second filters 520 and 550.

[0112] In addition, the intensity of light corresponding to the transmission wavelength band through the third optical filters 530 and 560 may increase with a slope between the slopes of the first optical filters 510 and 540 and the slopes of the second optical filters 520 and 550 in response to an increase in incident light intensity.

[0113] The intensity of the light of the selected wavelength band passing through each of the first optical filters 510 and 540, the second optical filters 520 and 550, and the third optical filters 530 and 560 can be converted into a pixel signal by the photoelectric conversion element 410 and the readout circuit. As a result, the response of the pixel including the first optical filter 510 or 530 can follow Figure 7 The response of the low sensitivity pixel (LPX) shown, the response of the pixel including the second filter 520 or 550 may follow Figure 7 The response of the high sensitivity pixel (HPX) is shown, and the response of the pixel including the third filter 530 or 560 may follow the response of the medium sensitivity pixel (MPX).

[0114] Thus, a pixel including the first filter 510 or 540 may correspond to a low sensitivity pixel (LPX), a pixel including the second filter 520 or 550 may correspond to a high sensitivity pixel (HPX), and a pixel including the third filter 530 or 560 may correspond to a medium sensitivity pixel (MPX).

[0115] An image sensing device 100 based on other implementations of the disclosed technology may include different air layers 511, 531, 541 and 561 having different thicknesses, and the air layers 511, 531, 541 and 561 are inserted into the filters 510, 530, 540 and 560 among the filters 510, 520, 530, 540, 550 and 560, and low-sensitivity pixels (LPX), medium-sensitivity pixels (MPX) and high-sensitivity pixels (HPX) are incorporated into one pixel array, so that the image sensing device 100 can form a high dynamic range (HDR) image using only one image.

[0116] Although the embodiments disclosed above include pixels with relatively lower sensitivity (i.e., LPX or MPX) disposed at specific positions in the quaternary Bayer pattern, the positions of the pixels with relatively lower sensitivity may be different in other implementations. For example, the pixels each having relatively lower sensitivity may be randomly spaced apart from each other in the same manner as phase detection autofocus (PDAF) pixels. In addition, the number of pixels each having relatively lower sensitivity may be determined to meet the desired HDR performance.

[0117] As apparent from the above description, an image sensing device based on some implementations of the disclosed technology may obtain a high dynamic range (HDR) image by capturing the image only once.

[0118] Although a number of exemplary embodiments have been described, variations and enhancements to the disclosed embodiments and other embodiments may be made based on what is disclosed in this patent document.

[0119] CROSS-REFERENCE TO RELATED APPLICATIONS

[0120] This patent document claims priority to and the benefit of Korean Patent Application No. 10-2021-0037014, filed on March 23, 2021, which is hereby incorporated by reference in its entirety as a part of the disclosure of this patent document.

Claims

1. An image sensing device, comprising: a substrate including a first photoelectric conversion element and a second photoelectric conversion element, the first photoelectric conversion element and the second photoelectric conversion element generating photocharges corresponding to the intensity of incident light corresponding to a first color; a first pixel including a first filter disposed above the first photoelectric conversion element to selectively transmit light corresponding to the first color; a second pixel including a second filter disposed above the second photoelectric conversion element to selectively transmit light corresponding to the first color; as well as a first air layer provided between the first optical filter and the first photoelectric conversion element to partially reflect light from the first optical filter, The reflection of incident light at the first filter corresponding to the first color and disposed on the first air layer is different from the reflection of incident light at the second filter corresponding to the first color and disposed on the second photoelectric conversion element.

2. The image sensing device according to claim 1, wherein: The first optical filter includes a bottom surface connected to a top surface of the first air layer; and The second filter includes a bottom surface connected to a top surface of the substrate.

3. The image sensing device according to claim 1, wherein: An amount of increase in response of the first pixel caused by an increase in intensity of light incident on the first pixel is smaller than an amount of increase in response of the second pixel caused by an increase in intensity of light incident on the second pixel.

4. The image sensing device according to claim 1, wherein: The maximum value of the dynamic range of the first pixel is higher than the maximum value of the dynamic range of the second pixel; and A minimum value of the dynamic range of the first pixel is higher than a minimum value of the dynamic range of the second pixel.

5. The image sensing device according to claim 1, wherein: A minimum value of the dynamic range of the first pixel is lower than a maximum value of the dynamic range of the second pixel.

6. The image sensing device according to claim 1, wherein: For light beams having the same intensity, the transmittance of the first optical filter is lower than the transmittance of the second optical filter.

7. The image sensing device according to claim 1, wherein: The first pixel group formed in a (2×2) matrix array includes one first pixel and three second pixels.

8. The image sensing device according to claim 7, further comprising: a second pixel group disposed on a first side of the first pixel group and including a third pixel having a third filter selectively transmitting light corresponding to a second color and a fourth pixel having a fourth filter selectively transmitting light corresponding to the second color; a third photoelectric conversion element, the third photoelectric conversion element being spaced apart from the third optical filter; as well as A second air layer is provided between the third optical filter and the third photoelectric conversion element to reflect light from the third optical filter.

9. The image sensing device according to claim 8, further comprising: an optical grating structure, the optical grating structure being arranged between the third optical filter and the fourth optical filter, The second air layer is disposed below the third optical filter and is shorter than the third optical filter and higher than the optical grid structure.

10. The image sensing device according to claim 7, further comprising: a third pixel group disposed on a second side of the first pixel group and including a fifth pixel and a sixth pixel, the fifth pixel having a fifth filter selectively transmitting light corresponding to a third color, and the sixth pixel having a sixth filter selectively transmitting light corresponding to the third color; as well as A third air layer is included in the fifth optical filter to reflect light from the fifth optical filter.

11. The image sensing device according to claim 10, further comprising: an optical grating structure formed between the fifth optical filter and the sixth optical filter, The third air layer is disposed below the fifth optical filter and is shorter than the fifth optical filter and higher than the optical grid structure.

12. The image sensing device according to claim 1, further comprising: a seventh pixel, the seventh pixel comprising a seventh filter, the seventh filter selectively transmitting light corresponding to the first color; as well as A fourth air layer is included under the seventh optical filter and has a thickness smaller than that of the first air layer.

13. The image sensing device according to claim 12, wherein: The first pixel, the second pixel, and the seventh pixel are constructed so that an increase in the response of the seventh pixel due to an increase in the intensity of light incident on the seventh pixel is greater than an increase in the response of the first pixel due to an increase in the intensity of light incident on the first pixel, and is less than an increase in the response of the second pixel due to an increase in the intensity of light incident on the second pixel.

14. The image sensing device according to claim 12, wherein: The maximum value of the dynamic range of the seventh pixel is lower than the maximum value of the dynamic range of the first pixel, and higher than the maximum value of the dynamic range of the second pixel; and The minimum value of the dynamic range of the seventh pixel is lower than the minimum value of the dynamic range of the first pixel, and higher than the minimum value of the dynamic range of the second pixel.

15. The image sensing device according to claim 12, wherein: The minimum value of the dynamic range of the seventh pixel is lower than the maximum value of the dynamic range of the second pixel; and The maximum value of the dynamic range of the seventh pixel is higher than the minimum value of the dynamic range of the first pixel.

16. An image sensing device, the image sensing device comprising: a substrate including a first photoelectric conversion element, a second photoelectric conversion element, and a third photoelectric conversion element, the first photoelectric conversion element, the second photoelectric conversion element, and the third photoelectric conversion element generating photocharges corresponding to the intensity of incident light corresponding to a first color; as well as a filter array disposed above the first photoelectric conversion element, the second photoelectric conversion element, and the third photoelectric conversion element and including a first filter corresponding to the first photoelectric conversion element and a second filter corresponding to the second photoelectric conversion element, Wherein, the filter array comprises: a first air layer provided between the first optical filter and the first photoelectric conversion element to partially reflect light from the first optical filter, and The reflection of incident light at the first filter corresponding to the first color and disposed on the first air layer is different from the reflection of incident light at the second filter corresponding to the first color and disposed on the second photoelectric conversion element.

17. The image sensing device according to claim 16, wherein: The first optical filter includes a bottom surface connected to a top surface of the first air layer; and The second filter includes a bottom surface connected to a top surface of the substrate.

18. The image sensing device according to claim 16, wherein: The filter array further comprises: a third optical filter disposed above the substrate and corresponding to the third photoelectric conversion element; and A second air layer is provided between the third optical filter and the third photoelectric conversion element to have a thickness smaller than that of the first air layer.

19. The image sensing device according to claim 18, wherein: The filter array further comprises: a plurality of optical grid structures, wherein the plurality of optical grid structures are disposed between the first optical filter, the second optical filter and the third optical filter, The second air layer is disposed between a lower portion of the third optical filter and a top surface of the substrate, and is formed to have a thickness smaller than that of the first air layer and each of the optical grating structures.

20. The image sensing device according to claim 16, wherein: For light beams having the same intensity, the transmittance of the first optical filter is lower than the transmittance of the second optical filter.

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