An image-sensing device includes photoelectric elements for receiving incident light. The photoelectric elements are arranged into unit cells, and each of the unit cells includes a first, a second, a third and a fourth photoelectric element. The first, the second, the third and the fourth photoelectric elements in each of the unit cells are formed of pillar structures, and the first, the second, the third and the fourth photoelectric elements are different sizes. The first photoelectric element captures a first image in a first phase, the second photoelectric element captures a second image in a second phase, the third photoelectric element captures a third image in a third phase, and the fourth photoelectric element captures a fourth image in a fourth phase. The first phase, the second phase, the third phase, and the fourth phase are different.

TECHNICAL FIELD

The disclosure relates to an image-sensing device.

BACKGROUND

With advances being made in technology, electronic devices equipped with a camera have become very popular. However, a modular lens in a conventional camera, a.k.a. a color image sensing (CIS) device, is generally an essential component for capturing incoming light and converting this captured light into digital images. However, due to the limitations of conventional imaging techniques, an image is formed with a lens, and a modular lens takes up a large portion of the available space within the camera. Since the size of portable electronic devices has become smaller and smaller, a large-sized modular lens is not appropriate for these devices.

Accordingly, there is demand for a lens-free image sensor to reduce the size of the camera.

SUMMARY

The disclosure provides an image-sensing device, which includes a plurality of photoelectric elements for receiving incident light. The photoelectric elements are arranged into a plurality of unit cells, and each of the unit cells includes a first photoelectric element, a second photoelectric element, a third photoelectric element, and a fourth photoelectric element. The first photoelectric element, the second photoelectric element, the third photoelectric element, and the fourth photoelectric element in each of the unit cells are formed of pillar structures, and the first photoelectric element, the second photoelectric element, the third photoelectric element, and the fourth photoelectric element are all different sizes. The first photoelectric element in each of the unit cells captures a first image in a first phase, the second photoelectric element in each of the unit cells captures a second image in a second phase, the third photoelectric element in each of the unit cells captures a third image in a third phase, the fourth photoelectric element in each of the unit cells captures a fourth image in a fourth phase. The first phase, the second phase, the third phase, and the fourth phase are different.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

Technical terms of the disclosure are based on general definition in the technical field of the disclosure. If the disclosure describes or explains one or some terms, definition of the terms is based on the description or explanation of the disclosure. Each of the disclosed embodiments has one or more technical features. In possible implementation, a person skilled in the art would selectively implement all or some technical features of any embodiment of the disclosure or selectively combine all or some technical features of the embodiments of the disclosure.

In each of the following embodiments, the same reference number represents the same or similar element or component.

FIG. 1is a schematic diagram of a phase-shifting digital holography device. Please refer toFIG. 1. The phase-shifting digital holography device100includes a laser light source110, a beam emitter120, beam splitters130and140, a piezoelectric transducer (PZT) mirror150, a mirror160, and a sensor array170. The laser light that emitted from the laser light source110is further enhanced at the beam emitter120, and the light emitted from the beam emitter120is split into an object light and a reference light by the beam splitter130. The reference light is reflected by the PZT mirror150that phase modulates the beam. By shifting a constant phase to the reference beam, different hologram images are obtained to derive the complex amplitude of the object wave.

For example, the initial phase of the reference wave is zero and changes by π/2 at each step. Assuming a 4-step phase-shifting digital holography algorithm is used and the intensity of the interference patterns at different phases such as 0, π/2, π, and 3π/2 may be respectively expressed in the formulas (1)-(4):
I0=|ψ0|2+|ψr|2+ψ0ψr*+ψ0*ψr(1)
Iπ/2=|ψ0|2+|ψr|2+jψ0ψr*−jψ0*ψr(2)
Iπ=|ψ0|2+|ψr|2+ψ0ψr*−ψ0*ψr(3)
I3π/2=|ψ0|2+|ψr|2−jψ0ψr*+jψ0*ψr(4)

After obtaining the intensity of the interference patterns at phases 0, π/2, π, and 3π/2, the complex amplitude of the object light is given by the following formula (5):

The complex amplitude of the object light is sometimes referred to as the complex hologram image because we may retrieve the amplitude distribution of the object light in the object plane from ψ0by performing digital back-propagation.

Accordingly, the complex amplitude of the reference light must be known in order to calculate object waves. Usually, the reference light is a plane wave or a spherical wave and therefore its phase is known without any measurement. One having ordinary skill in the art will appreciate the techniques for reconstructing an object image using object waves at different phases, and thus the details will be omitted here.

It should be noted that the phase-shifting digital holography device100described in the example ofFIG. 1has to change phase at each step, and it takes time to change phase, calculate the intensities of interference patterns, and reconstruct the object image. Accordingly, it is not practical to employ the device100in any portable electronic devices currently being sold on the market.

However, the concept of phase delay of the phase-shifting digital holography algorithm may be used in an image-sending device of the disclosure.FIG. 2Ais a top view of an image-sensing device according to an embodiment of the disclosure.FIG. 3is a cross-sectional view of the image-sensing device inFIG. 2A. In the embodiment, the image-sensing device200is, for example, a mono-color image sensor. Please refer toFIG. 2AandFIG. 3. The image-sensing200may include a sensor array210. The sensor array210includes a plurality of photoelectric elements for receiving incident light. The photoelectric elements may be implemented on a substrate250(as shown inFIG. 3) via semiconductor manufacturing processes. It should be noted that no lens is used in the image-sensing device200.

In the sensor array210, the photoelectric elements are arranged into a plurality of unit cells220,230,240and250. For example, each of unit cells220,230,240and250includes a photoelectric element221, a photoelectric element222, a photoelectric element223and a photoelectric element224, and the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224are arranged into a 2×2 array.

Furthermore, the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224in each of the unit cells220,230,240and250are formed of pillar structures. In the embodiment, materials of the pillar structures are, for example, single crystal silicon, polycrystalline silicon (poly Si), amorphous silicon, Si3N4, GaP, TiO2, AlSb, AlAs, AlGaAs, AlGaInP, BP, ZnGeP2, any other applicable material, or a combination thereof, but the embodiment of the disclosure is not limited thereto.

In addition, the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224are different sizes. For example, the size of the photoelectric element221is less than the size of the photoelectric element222. The size of the photoelectric element222is less than the size of the photoelectric element223. The size of the photoelectric element223is less than the size of the photoelectric element224.

Furthermore, the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224may be different diameters, and the diameter of each of the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224represents a specific phase of a corresponding phase-shifting hologram image.

Specifically, a 4-step phase-shifting holography method is employed into the architecture of the image-sensing device200. For example, the diameters of the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224are d0, d1, d2, and d3 that correspond to the phase δ0, the phase δ1, the phase δ2, and the phase δ3, respectively. The values of the phase δ0, the phase δ1, the phase δ2, and the phase δ3 are, for example 0, π/2, π, and 3π/2, respectively. In the embodiment, a corresponding relationship of the diameters of the photoelectric elements and the phases is as shown inFIG. 4. In addition, diameters of the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224are, for example, 120-350 nm, and heights of the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224are, for example, 300-750 nm.

It should be noted that the unit cell220is repeatedly arranged in the sensor array210, and each of the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224in each of unit cells220,230,240and250may capture an image in an individual phase of four different phases. For example, the photoelectric element221in each of the unit cells220,230,240and250captures a first image in a first phase (such as the phase δ0), the photoelectric element222in each of the unit cells220,230,240and250captures a second image in a second phase (such as the phase δ1), the photoelectric element223in each of the unit cells220,230,240and250captures a third image in a third phase (such as the phase δ2), the photoelectric element224in each of the unit cells220,230,240and250captures a fourth image in a fourth phase (such as the phase δ3).

Since the first image, the second image, the third image, and the fourth image are captured by the photoelectric element221, the photoelectric element222, the photoelectric element223and the photoelectric element224in each of the unit cells250, and thus the locations of the first image, the second image, the third image, and the fourth image are substantially the same. For example, the phase-shifting hologram image for the phase δ0 may be obtained from the captured image of the photoelectric element221in each of unit cells220,230,240and250. Similarly, the phase-shifting hologram image for the phase δ1, the phase δ2, and the phase δ3 may be obtained from the captured image of the photoelectric element222, the photoelectric element223and the photoelectric element224in each of the unit cells220,230,240and250, respectively.

After obtaining phase-shifting hologram images in four phases, the object wave in the Fourier domain may be obtained using formula (5). Subsequently, an inverse Fourier transform is performed on the object wave to reconstruct the object image in the spatial domain. Alternatively, a transfer function H(x, y) for transforming the object wave in the Fourier domain to the object image in the spatial domain may be estimated in advance, and thus a convolution between the object wave and the transfer function may be performed to obtain the object image.

In the embodiment, each of the unit cells220,230,240and250is formed as a 2×2 array, an order of the first photoelectric element221, the second photoelectric element222, the third photoelectric element223and the fourth photoelectric element224in the 2×2 array is fixed, and an order of each of unit cells220,230,240and250is fixed, as shown inFIG. 2A. Therefore, patterns formed by the unit cells220,230,240and250may be the same. However, the embodiment of the disclosure is not limited thereto.

In some embodiments, each of the unit cells220,230,240and250is formed as a 2×2 array, an order of the first photoelectric element221, the second photoelectric element222, the third photoelectric element223and the fourth photoelectric element224in the 2×2 array is flexible, and an order of each of the unit cells220,230,240and250is flexible, as shown inFIG. 2B. Therefore, patterns formed by the unit cells220,230,240and250may be different.

Alternatively, in some embodiments, each of the unit cells220,230,240and250is formed as a 2×2 array, an order of the first photoelectric element221, the second photoelectric element222, the third photoelectric element223and the fourth photoelectric element224in the 2×2 array is fixed, each of the unit cells220,230,240and250is repeated with a predetermined degree rotation to the right, or each of the unit cells220,230,240and250is repeated with a flip to the right, or each of the unit cells220,230,240and250is repeated with the flip and the predetermined degree rotation to the right, as shown inFIG. 5,FIG. 6orFIG. 7. The predetermined degree may be, for example, 90 degrees, 180 degrees or 270 degrees.

It can be seen inFIG. 5, the order of the photoelectric element221, the photoelectric element222, the photoelectric element223, and the photoelectric element224in the 2×2 array of each of the unit cells220,230,240and250may be fixed, the unit cell220is repeated with the predetermined degree (for example, 90 degrees) rotation to the right from the unit cell250, the unit cell250is repeated with the predetermined degree (for example, 180 degrees) rotation to the right from the unit cell240, the unit cell240is repeated with the (vertical) flip and the predetermined degree (for example, 90 degrees) rotation to the right from the unit cell230, and the unit cell230is repeated with the (vertical) flip to the right the unit cell220. Therefore, patterns formed by the unit cells220,230,240and250are different.

It can be seen inFIG. 6, the order of the photoelectric element221, the photoelectric element222, the photoelectric element223, and the photoelectric element224in the 2×2 array of each of the unit cells220,230,240and250may be fixed, the unit cell220is repeated with the predetermined degree (for example, 90 degrees) rotation to the right from the unit cell250, the unit cell250is repeated with the predetermined degree (for example, 180 degrees) rotation to the right from the unit cell240, the unit cell240is repeated with the (horizontal) flip and the predetermined degree (for example, 90 degrees) rotation to the right from the unit cell230, and the unit cell230is repeated with the (horizontal) flip to the right the unit cell220. Therefore, patterns formed by the unit cells220,230,240and250are different.

It can be seen inFIG. 7, the order of the photoelectric element221, the photoelectric element222, the photoelectric element223, and the photoelectric element224in the 2×2 array of each of the unit cells220,230,240and250may be fixed, the unit cell220is repeated with the predetermined degree (for example, 270 degrees) rotation to the right from the unit cell250, the unit cell250is repeated with the predetermined degree (for example, 180 degrees) rotation to the right from the unit cell240, the unit cell240is repeated with the (vertical) flip and the predetermined degree (for example, 90 degrees) rotation to the right from the unit cell230, and the unit cell230is repeated with the (horizontal) flip to the right the unit cell220. Therefore, patterns formed by the unit cells220,230,240and250are different. The other arrangements of the photoelectric element221, the photoelectric element222, the photoelectric element223, and the photoelectric element224in the 2×2 array of each of the unit cells220,230,240and250may be refer to the embodiment ofFIG. 5,FIG. 6orFIG. 7, and the description thereof is not repeated herein.

FIG. 8is a flowchart of a 4-step phase-shifting holography method for use in an image-sensing device according to an embodiment of the disclosure. The flowchart inFIG. 8is for use in the image-sensing device200(such as the mono-color image sensor). In step S810, the method involves obtaining four phase-shifting hologram images in different phases. For example, the image-sensing device200shown inFIG. 2A,FIG. 2B,FIG. 5,FIG. 6orFIG. 7may be used in the following embodiments. Specifically, the four phase-shifting hologram images correspond to the phases 0, π/2, π, and 3π/2.

In step S820, the method involves calculating the object wave in the Fourier domain according to the four phase-shifting hologram images in different phases. For example, the intensities of the phase-shifting hologram images in different phases (such as 0, π/2, π, and 3π/2) may be calculated using formulas (1)˜(4), and the object wave may be calculated using formula (5). However, to simplify the calculation of the object wave, the object wave φ0may be calculated approximately using the following formula (6):
φ0≈(I0−Iπ)−ƒ(Iπ/2−I3π/2)  (6)

In step S830, the method involves reconstructing the object image according to the object wave. For example, the object wave φ0is in the Fourier domain and the object image is in the spatial domain, and thus an inverse Fourier transform may be applied on the object wave φ0to reconstruct the object image. Alternatively, a transfer function H(x, y) for transforming the object wave in the Fourier domain to the object image in the spatial domain may be estimated in advance, and thus a convolution between the object wave and the transfer function may be performed to obtain the object image.

FIG. 9is a top view of an image-sensing device according to another embodiment of the disclosure.FIG. 10is a cross-sectional view of the image-sensing device inFIG. 9. In the embodiment, the image-sensing device900is, for example, a color image sensor. Please refer toFIG. 9andFIG. 10. The image-sensing device900may include a sensor array910and a filter array970.

The sensor array910includes a plurality of photoelectric elements for receiving incident light. In the sensor array910, the photoelectric elements are arranged into a plurality of unit cells930,940,950and960. For example, the unit cell930(such as a first unit cell) includes a photoelectric element931, a photoelectric element932, a photoelectric element933and a photoelectric element934. The unit cell940(such as a second unit cell) includes a photoelectric element941, a photoelectric element942, a photoelectric element943and a photoelectric element944. The unit cell950(such as a third unit cell) includes a photoelectric element951, a photoelectric element952, a photoelectric element953and a photoelectric element954. The unit cell960(such as a fourth unit cell) includes a photoelectric element961, a photoelectric element962, a photoelectric element963and a photoelectric element964.

In the embodiment, the photoelectric elements931˜934, the photoelectric elements941˜944, the photoelectric elements951˜954and the photoelectric elements961˜964may be arranged into a 2×2 array, respectively. The photoelectric elements931˜934, the photoelectric elements941˜944, the photoelectric elements951˜954and the photoelectric elements961˜964are equal to or similar to the photoelectric elements221˜224inFIG. 2A. Accordingly, the photoelectric elements931˜934, the photoelectric elements941˜944, the photoelectric elements951˜954and the photoelectric elements961˜964may refer to the embodiments inFIGS. 2A-6, and the description thereof is not repeated herein.

In addition, the unit cells930,940,950and960are arranged into a plurality of macro unit cells920. For example, each of the macro unit cells920may include the unit cell930, the unit cell940, the unit cell950and the unit cell960. In the embodiment, the unit cell930, the unit cell940, the unit cell950and the unit cell960may be arranged into a 2×2 array.

The filter array970is disposed on the photoelectric elements, i.e., the filter array970is disposed on the sensor array910. In addition, the filter array970may include a plurality of color filters, such as red filters972, green filters974and976, and blue filters978. For example, two green filters974and976, one red filter972, and one blue filter978are arranged into a 2×2 array. In the embodiment, the green filters974and976may extract green light from the incident light, the red filter972may extract red light from the incident light, and the blue filter978may extract blue light from the incident light.

The sensor array910may receive the incident light via the filter array970. The unit cell930may correspond to the green filter974in the filter array970, the unit cell940may correspond to the green filter976in the filter array970, the unit cell950may correspond to the red filter972in the filter array970, and the unit cell960may correspond to the blue filter978in the filter array970. Thus, the unit cells930,940,950, and960in each of the macro unit cells920may receive the green light, the green light, the red light and the blue light via the green filter974, the green filter976, the red filter972and the blue filter978in the filter array910, respectively. Specifically, the four unit cells930,940,950, and960in each of the macro unit cell920are configured to capture green, blue, red, and green images in four different phases, such as 0, π/2, π, and 3π/2.

Given that Hζr, Hζg, and Hζbrepresent the wavelengths of the red light, green light, and blue light respectively, it can be concluded that the relationship between the wavelengths is Hζr>Hζg>Hζb, since the red light has the longest wavelength and the blue light has the shortest wavelength among red, green, and blue lights. Accordingly, assuming that the photoelectric elements in the sensor array910are made of the same material, the photoelectric elements951˜954in the unit cell950for receiving the red light have relatively greater heights than the photoelectric elements in other unit cells in the macro unit cell920. That is, the heights of the photoelectric elements in each unit cell are proportional to the wavelength of the received light.

For example, the heights of the photoelectric elements951˜954in the unit cell950(corresponding to the red filter972) are higher than the heights of the photoelectric elements931˜934and941˜944in the unit cell930and the unit cell940(corresponding to the green filters941and976), and the heights of the photoelectric element931˜934and941˜944in the930and the unit cell940(corresponding to the green filters941and976) are higher than the heights of the photoelectric elements961˜964in the unit cell960, as shown inFIG. 10.

Since the macro unit cell920is repeatedly arranged in the sensor array910, four phase-shifting hologram images are obtained by combining images captured by each of the unit cells930,940,950, and960of the macro unit cells920in the sensor array910, and thus total 16 phase-shifting hologram images may be obtained. It should be noted that the green phase-shifting hologram image captured by the unit cell930is the same as that captured by the unit cell940. For example, the total 16 phase-shifting hologram images may be (Rδ0, Rδ1, Rδ2, Rδ3), (G1δ0, G1δ1, G1δ2, G1δ3), (G2δ0, G2δ1, G2δ2, G2δ3), and (Bδ0, Bδ1, Bδ2, Bδ3), wherein the green phase-shifting hologram images (G1δ0, G1δ1, G1δ2, G1δ3) are captured by the unit cell930, and the green phase-shifting hologram images (G2δ0, G2δ1, G2δ2, G2δ3) are captured by the unit cell940.

In one embodiment, the green filter974and the green filter976are respectively formed of a green color filter (for example, “GCF” inFIG. 11), the red filter972is formed of a red color filter (for example, “RCF” inFIG. 11), and the blue filter978is formed of a blue color filter, as shown inFIG. 11.

In one embodiment, the green filter974and the green filter976are respectively formed of a green multi-film (for example, “MFG” inFIG. 12), the red filter972is formed of a red multi-film (for example, “MFR” inFIG. 12), and the blue filter978is formed of a blue multi-film, as shown inFIG. 12.

In one embodiment, the green filter974and the green filter976are respectively formed of a green grating, the red filter972is formed of a red grating, and the blue filter978is formed of a blue grating, as shown inFIG. 13.

FIG. 14is a flowchart of a 4-step phase-shifting holography method for use in an image-sensing device according to an embodiment of the disclosure. The flowchart inFIG. 14is for use in the image-sensing device900(such as the color image sensor). In step S1410, the method involves obtaining 16 phase-shifting hologram images in different color channels and different phases. For example, the image-sensing device900inFIG. 9may be used in the following embodiments. The 16 phase-shifting hologram images are (Rδ0, R⊕1, Rδ2, Rδ3), (G1δ0, G1δ1, G1δ2, G1δ3), (Bδ0, BM, Bδ2, Bδ3), and (G2δ0, G2δ1, G2δ2, G2δ3), as described above. The above color channels may correspond to the unit cells930,940,950and960, respectively.

In step S1420, the method involving calculating the object wave in each color channel in the Fourier domain according to the 16 phase-shifting hologram images in different color channels and different phases.

In step S1430, the method involving reconstructing the object image for each color channel according to the object wave in each color channel. Specifically, there are four color channels such as one red channel, one blue channel, and two green channels for the image-sensing device900(such as the color image sensor), and the operations for calculating the object wave and reconstructing the object image in a single color channel may be referred to in the embodiment ofFIG. 8, and the description thereof is not be repeated herein.

Thus, four object images representing one red channel, one blue channel, and two green channels are obtained after step S1430, and an image signal processor (not shown) coupled to the image-sensing device900may reconstruct the original color image using the four object images.

In summary, according to the image-sensing device disclosed by the embodiment of the disclosure, the photoelectric elements in each of the unit cells are formed of pillar structures, and the photoelectric elements are different sizes. By arranging photoelectric elements with different sizes, that are designed for different phases in the 4-step phase-shifting holography algorithm, into the sensor array of the image-sensing device, the object image may be reconstructed using the phase-shifting hologram images captured by the photoelectric elements, and thus no modular lens is required in the camera module using the lens-free image sensor, and thus the cost of the whole camera module may be reduced and the thickness of the camera module may be thinner.