WO2022051967A1

WO2022051967A1 - Optical apparatus

Info

Publication number: WO2022051967A1
Application number: PCT/CN2020/114419
Authority: WO
Inventors: Yingqing LIU; Sota Miyatani; Takuya Anzawa; Qing TONG
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2020-09-10
Filing date: 2020-09-10
Publication date: 2022-03-17
Also published as: CN116195266A

Abstract

An optical apparatus, where the optical apparatus (10) comprises a lens system (12); an image sensor (13) configured to receive light passing through the lens system (12), where the image sensor (13) is a binning type image sensor capable of changing a pixel pitch thereof; and an intensity controller (11) configured to reduce intensity of light passing through at least one reduction area thereof to change intensity distribution of light entering the lens system (12) in accordance with the pixel pitch of the image sensor (13).

Description

OPTICAL APPARATUS

TECHNICAL FIELD

The present disclosure relates to a method for reducing a Moire effect, an optical apparatus capable of implementing the method, and a device having the optical apparatus. For example, the device may be a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a surveillance camera, or the like.

BACKGROUND

Recent development of manufacturing technologies provide increasing the number of pixels in the image sensor mounted on a device such as a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, or a surveillance camera.

In some cases, an increase in the number of pixels causes a decrease in a pixel pitch of the image sensor since a size of the image sensor that can be installed in the device is limited. The decrease in the pixel pitch of the image sensor may reduce light receiving sensitivity. In this regard, a binning type sensor capable of changing the pixel pitch thereof is recently attracting attention as solution for improving the light receiving sensitivity.

The binning type sensor has a feature of combining pixel signals from adjacent pixels into one resulting signal to virtually combine the adjacent multiple pixels into one pixel. For example, there exists a horizontal binning type sensor, a vertical binning type sensor, and a full binning type sensor. The horizontal and vertical binning type sensors may virtually combine a pair of adjacent pixels arranged in the row and column direction respectively and double the pixel pitch thereof. In addition, the full binning type sensor may virtually combine adjacent NxN pixels arranged two-dimensionally and increase the pixel pitch N times, where N is set to be equal to or more than 2. For example, a binning operation increasing the pixel pitch 2 times may be called "2x2 binning" .

However, an increase in the pixel pitch may facilitate a Moire effect appearing in a generated image, since the Moire effect becomes noticeable when capturing an object having a spatial frequency larger than a Nyquist frequency corresponding to the pixel pitch of the image sensor. Although some conventional cameras are equipped with an optical low pass filter (OLPF) in order to reduce the Moire effect, the Moire effect is not reduced effectively when the pixel pitch of the image sensor is changed since a cutoff frequency of the conventional OLPF is fixed.

SUMMARY

Embodiments provide an optical apparatus, a method for reducing a Moire effect, and a device having the optical apparatus. The device may be a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera, a surveillance camera, or the like.

A first aspect of the embodiments provides the optical apparatus. In a first possible implementation form of the first aspect, the optical apparatus comprises: a lens system; an image sensor configured to receive light passing through the lens system, where the image sensor is a binning type image sensor capable of changing a pixel pitch thereof; and an intensity controller configured to reduce intensity of light passing through at least one reduction area thereof to change intensity distribution of light entering the lens system in accordance with the pixel pitch of the image sensor.

According to the first possible implementation form of the first aspect, the intensity distribution of light entering the lens system may be changed in accordance with the pixel pitch of the image sensor, thereby lowering a modulation transfer function (MTF) curve of the optical apparatus enough at a target spatial frequency relevant to the pixel pitch of the image sensor.

For example, the target spatial frequency may be a Nyquist frequency corresponding to the pixel pitch of the image sensor. Lowering the MTF curve enough at the corresponding target spatial frequency may result in reduction of the Moire effect appearing on an image generated based on output signals from the image sensor.

In the first possible implementation form of the first aspect, the Moire effect may be effectively reduced by forming the intensity distribution providing the suitable MTF curve relevant to the current pixel pitch of the image sensor, even though the pixel pitch of the image sensor is changed.

A second possible implementation form of the first aspect provides: the optical apparatus according to the first possible implementation form of the first aspect, where the at least one reduction area is configured so that the MTF curve of the optical apparatus lowers enough at around the Nyquist frequency corresponding to the pixel pitch of the image sensor.

The Moire effect becomes noticeable when capturing an object having a spatial frequency larger than the Nyquist frequency corresponding to the pixel pitch of the image sensor. In the second possible implementation form of the first aspect, the MTF curve of the optical apparatus may be controlled to lower enough at around the Nyquist frequency corresponding to the pixel pitch of the image sensor by applying the suitable intensity distribution, thereby effectively reducing the Moire effect even though the pixel pitch of the image sensor is changed.

Optionally, the intensity controller may be an intensity controlling mask for reducing intensity of light passing through the at least one reduction area thereof. The intensity controlling mask may be a film, a panel, a sheet or the like, having a feature of the intensity controller.

In some exemplary implementation cases, the intensity controlling mask may be an electrochromic device, a liquid crystal device, or the like. Those are exemplary elements usable as the intensity controlling mask, and it should be noted that no limitation is intended herein by such example enumeration.

The electrochromic device may be a solid-state electrochromic device that solid inorganic material such as Ta ₂O ₅ and ZrO ₂ or organic material is used as electrolytes, or a laminated electrochromic device that a liquid gel is used as the electrolyte. The electrochromic device may be used for controlling optical properties such as refraction, absorption and reflectance by applying voltage.

If the electrochromic device is used as the intensity controlling mask, the electrochromic device controls absorption of a target area thereof to reduce intensity of light passing through the target area. Herein, such target area is called as the reduction area. The absorption of light passing through the at least one reduction area may form the suitable intensity distribution of the light to lower the MTF curve and then reduce the Moire effect in a generated image.

Likewise, even in another case of using the liquid crystal device as the intensity controlling mask, the intensity distribution is changed and the Moire effect may be reduced by lowering the MTF curve at around the target frequency. The present disclosure is not limited to those exemplary cases, and other modified examples are also applicable.

A third possible implementation form of the first aspect provides: the optical apparatus according to the second possible implementation form of the first aspect, where the intensity controlling mask is divided into a plurality of ring-shaped areas centered on an optical axis of the lens system, and each ring-shaped area and an area inside an innermost ring-shaped area are capable of being a reduction area with a low transmittance or a non-reduction area with a high transmittance.

In the third possible implementation form of the first aspect, each reduction area has an axis-symmetric shape centered on the optical axis of the lens system, and various circular striped patterns may be implemented by controlling voltage applied to at least a part of the ring-shaped areas and/or the area inside the innermost ring-shaped area. The target frequency at which the MTF curve of the optical apparatus lowers enough may be finely controlled by switching between the circular striped patterns on the intensity controlling mask in accordance with the pixel pitch of the image sensor.

A second aspect of the embodiments provides the method for reducing a Moire effect. In a first possible implementation form of the second aspect, the method comprises: reducing, by an intensity controller, intensity of light passing through at least one reduction area of the intensity controller to change intensity distribution of light entering the lens system in accordance with a pixel pitch of an image sensor that is a binning type image sensor capable of changing the pixel pitch thereof; and receiving, by the image sensor, light passing through the lens system.

According to the first possible implementation form of the second aspect, the intensity distribution of light entering the lens system may be changed in accordance with the pixel pitch of the image sensor, thereby lowering a MTF curve of the optical apparatus enough at a target spatial frequency relevant to the pixel pitch of the image sensor.

In the first possible implementation form of the second aspect, the Moire effect may be effectively reduced by forming the intensity distribution providing the suitable MTF curve relevant to the current pixel pitch of the image sensor, even though the pixel pitch of the image sensor is changed.

A second possible implementation form of the second aspect provides: the method according to the first possible implementation form of the second aspect, the at least one reduction area is determined so that the MTF curve of an optical apparatus including the intensity controller and the lens system drops at around a Nyquist frequency corresponding to the pixel pitch of the image sensor.

As mentioned above, the Moire effect becomes noticeable when capturing an object having a spatial frequency larger than the Nyquist frequency corresponding to the pixel pitch of the image sensor. In the second possible implementation form of the second aspect, the MTF curve of the optical apparatus may be controlled to lower enough at around the Nyquist frequency corresponding to the pixel pitch of the image sensor by applying the suitable intensity distribution, thereby effectively reducing the Moire effect even though the pixel pitch of the image sensor is changed.

A third possible implementation form of the second aspect provides: the method according to the second possible implementation form of the second aspect, where the intensity controlling mask is divided into a plurality of ring-shaped areas centered on an optical axis of the lens system, and each ring-shaped area and an area inside an innermost ring-shaped area are capable of being a reduction area with a low transmittance or a non-reduction area with a high transmittance.

A third aspect of the embodiments provides the device comprising: the optical apparatus according to any one of the first to third possible implementation forms of the first aspect; and a processor configured to generate an image based on output signals from the image sensor to store the image in a memory.

A fourth aspect of the embodiments provides a program that causes a computer to perform the method according to any one of the first to third possible implementation forms of the second aspect. A fifth aspect of the embodiments provides a non-transitory computer-readable storage medium storing a program that causes a computer to perform the method according to any one of the first to third possible implementation forms of the second aspect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram for describing configuration of a device and an optical apparatus in the device according to the embodiment of the present disclosure,

FIG. 2 is a schematic diagram for describing arrangement of an intensity distribution (ID) controller and lens groups in the optical apparatus according to the embodiment of the present disclosure,

FIG. 3 is a schematic diagram for describing controllable areas of the ID controller according to the embodiment of the present disclosure,

FIG. 4 shows a first example of a reduction area of the ID controller according to the embodiment of the present disclosure,

FIG. 5 shows a second example of the reduction area of the ID controller according to the embodiment of the present disclosure,

FIG. 6 shows a third example of the reduction area of the ID controller according to the embodiment of the present disclosure,

FIG. 7 shows a fourth example of the reduction area of the ID controller according to the embodiment of the present disclosure,

FIG. 8 shows a fifth example of the reduction area of the ID controller according to the embodiment of the present disclosure,

FIG. 9 shows a sixth example of the reduction area of the ID controller according to the embodiment of the present disclosure,

FIG. 10 shows a first example of a modulation transfer function (MTF) curve of the optical apparatus according to the embodiment of the present disclosure,

FIG. 11 shows a second example of the MTF curve of the optical apparatus according to the embodiment of the present disclosure,

FIG. 12 shows a flowchart for describing a method implemented by the device according to the embodiment of the present disclosure,

FIG. 13A shows a first preferable configuration of the reduction areas of the ID controller,

FIG. 13B shows the MTF curve corresponding to the first preferable configuration of the reduction areas,

FIG. 14A shows a second preferable configuration of the reduction areas of the ID controller,

FIG. 14B shows the MTF curve corresponding to the second preferable configuration of the reduction areas,

FIG. 15A shows a third preferable configuration of the reduction areas of the ID controller, and

FIG. 15B shows the MTF curve corresponding to the third preferable configuration of the reduction areas.

DESCRIPTION OF EMBODIMENTS

The following describes technical solutions of the embodiments, referring to the accompanying drawings. It will be understood that the embodiments described below are not all but just some of embodiments relating to the present disclosure. It is to be noted that all other embodiments which may be derived by a person skilled in the art based on the embodiments described below without creative efforts shall fall within the protection scope of the present disclosure.

Following embodiment relates to a method for reducing a Moire effect, an optical apparatus implementing the method, and a device having the optical apparatus. This embodiment may apply to various devices such as a mobile phone, a smart phone, a tablet computer, a personal computer, a digital still camera, a digital video camera and a surveillance camera.

(Exemplary configuration of the optical apparatus and the device) Following describes configuration of the optical apparatus and the device according to the embodiment of the present disclosure with reference to FIG. 1.

FIG. 1 is a schematic block diagram for describing configuration of the device and the optical apparatus in the device according to the embodiment of the present disclosure. A device 10 shown in FIG. 1 is an example of the device according to the embodiment of the present disclosure.

As shown in FIG. 1, the device 10 comprises an intensity distribution (ID) controller 11, a lens system 12, an image sensor 13, a processor 14 and a memory 15. Optionally, the device 10 may further comprise at least one dedicated controller for controlling operation of the ID controller 11 and/or the image sensor 13.

The ID controller 11, the lens system 12 and the image sensor 13 may form the optical apparatus according to the embodiment of the present disclosure. For example, the ID controller 11 may operate as an intensity controlling mask for changing intensity distribution of light entering the lens system 12. The intensity controlling mask may be an electrochromic (EC) device, a liquid crystal (LC) device, or the like. Those are exemplary elements usable as the intensity controlling mask, and it should be noted that no limitation is intended herein by the example enumeration.

The lens system 12 comprises at least one lens group, a stop (an iris) , and an optical filter such as a infrared ray (IR) cut filter. For example, the lens system 12 may have a structure shown in FIG. 2. FIG. 2 is a schematic diagram for describing arrangement of a WF controller and lens groups in the optical apparatus according to the embodiment of the present disclosure.

In an example of FIG. 2, the lens system 12 includes a stop ST and lenses L1 to L7, and the WF controller 11 is located on an object side of the lens system 12. In FIG. 2, a Z-direction corresponds to an optical axis AX of the lens system 12, and a surface of the WF controller 11 is perpendicular to the Z-direction and corresponds to a X-Y plane. OP1 and OP2 in FIG. 2 represent optical paths that are symmetrical with respect to the optical axis AX.

The image sensor 13 may be a charge coupled device (CCD) image sensor, a complementary metal-oxide-semiconductor (CMOS) image sensor, or the like. The image sensor 13 is a binning type image sensor capable of changing a pixel pitch thereof. Also, the image sensor 13 is configured to receive light passing through the lens system 12.

The processor 14 is configured to generate an image based on output signals from the image sensor 13 and store the image in the memory 15. For example, the processor 14 may be a central processing unit (CPU) , a field-programmable gate array (FPGA) , an application specific integrated circuit (ASIC) , a graphics processing unit (GPU) , or the like.

The memory 15 may be a read-only memory (ROM) , a random access memory (RAM) , a flash memory, a hard disk drive (HDD) , a solid state drive (SSD) , a portable storage medium, or the like. Also, the memory 15 may store a program to cause the processor 14 to perform operation for controlling at least one of the ID controller 11, the lens system 12 and the image sensor 13. The program may be provided to the device 10 via data carrying means such as a non-transitory computer readable storage medium, a local and/or wide area network, or the like.

In the embodiment of the present disclosure, the ID controller 11 is configured to reduce intensity of light passing through at least one reduction area thereof to change intensity distribution of light entering the lens system 12 in accordance with the pixel pitch of the image sensor 13.

In some exemplary implementation cases, the ID controller 11 may be an electrochromic (EC) device, a liquid crystal (LC) device, or the like. Those are exemplary elements usable as the intensity controlling mask, and it should be noted that no limitation is intended herein by such example enumeration.

The EC device may be a solid-state electrochromic device that solid inorganic material such as Ta ₂O ₅ and ZrO ₂ or organic material is used as electrolytes, or a laminated electrochromic device that a liquid gel is used as the electrolyte. The EC device may be used for controlling optical properties such as refraction, absorption and reflectance by applying voltage.

If the EC device is used as the ID controller 11, the EC device controls absorption of a target area thereof to reduce intensity of light passing through the target area. Such target area is the reduction area mentioned above. The absorption of light passing through the at least one reduction area may form the suitable intensity distribution of the light to lower the MTF curve and then reduce the Moire effect in a generated image.

Likewise, even in another case of using the LC device as the ID controller 11, the intensity distribution is changed and the Moire effect may be reduced by lowering the MTF curve at around the target frequency. The present disclosure is not limited to those exemplary cases, and other modified examples are also applicable.

In general, a Moire effect becomes noticeable when capturing an object having a spatial frequency larger than a Nyquist frequency corresponding to a pixel pitch of an image sensor used for the capturing.

In the embodiment of the present disclosure, the intensity distribution of light entering the lens system 12 may be changed to a suitable intensity distribution for lowering the MTF curve of the optical apparatus enough at around the Nyquist frequency corresponding to the current pixel pitch of the image sensor 13. This may cause reduction of the Moire effect appearing on a generated image. Further, since at least one suitable reduction area is selected in accordance with the pixel pitch of the image sensor 13, the Moire effect may be reduced even thought the pixel pitch is changed by binning operation.

(Method for controlling a shape of the deformation area) Following describes a method for controlling a shape of the reduction area with reference to FIG. 3. FIG. 3 is a schematic diagram for describing controllable areas of the ID controller according to the embodiment of the present disclosure. FIG. 3 illustrates merely one of exemplary cases of the embodiment, and it should be noted that the present disclosure is not limited to such exemplary cases and other modified examples are also applicable.

As shown in FIG. 3, the ID controller 11 may be divided into ring-shaped areas A2 to A5 centered on the optical axis AX of the lens system 12, and an area A1 inside the innermost ring-shaped area A2. Optionally, the number of divided areas in the ID controller 11 may be equal to or more than 6 or be equal to or less than 4.

Each of the areas A1 to A5 is capable of being the reduction area or a non-reduction area (e.g. a transparent area) . For example, an area of the ID controller 11 to which a predetermined voltage is applied acts as the reduction area, and another area of the ID controller 11 to which no voltage is applied operates as the non-reduction area. Intensity of light passing through the reduction area is reduced and intensity of light passing through the non-reduction area is maintained.

In an example of FIG. 3, each divided area has an axis-symmetric shape centered on the optical axis of the lens system 12. In this case, various circular striped patterns may be implemented by controlling voltage applied to at least a part of the ring-shaped areas and/or the area inside the innermost ring-shaped area, as shown in FIGs. 4 to 9. FIGs. 4 to 9 show exemplary patterns formed by the at least one reduction area of the ID controller according to the embodiment of the present disclosure.

The example of FIG. 4 shows that the areas A2-A5 are set to be reduction area, and the remaining area A1 is set to be the non-reduction area. In this example, intensity of light passing through the areas A2-A5 is reduced. Here, configuration of the areas A1 to A5 is represented by using a vector like (y1, y2, y3, y4, y5) , where y1 to y5 indicate a state of the areas A1 to A5 respectively, and each of y1, y2, y3, y4 and y5 is 0 if it is the reduction area and 1 if it is the non-reduction area.

The example of FIG. 4 shows that the areas A2-A5 are set to be the reduction area, and the remaining area A1 is set to be the non-reduction area. In this example, the states of the areas A1 to A5 are represented by (0, 1, 1, 1, 1) and light passing through the areas A2-A5 is absorbed at a specific rate associated with a predetermined transmittance of the reduction area.

Optionally, a transmittance (or an absorption coefficient) of each reduction area may be determined determined so as to lower the MTF curve enough at a target spatial frequency associated with the binning type (e.g. 2x2 binning, 4x4 binning, or the like) . In this regard, since a frequency at which the MTF curve lowers enough depends on a shape of the reduction area, it is preferable that the transmittance is determined in consideration of the shape of the reduction area so that the MTF curve lowers enough at the target frequency. To simplify the explanation, the following describes the example that the transmittance is set to be a given value.

The example of FIG. 5 shows that the areas A1, A3-A5 are set to be reduction area, and the remaining area A2 is set to be the non-reduction area. In this example, the states of the areas A1 to A5 is represented by (1, 0, 1, 1, 1) , and light passing through the areas A1, A3-A5 is absorbed at the specific rate.

The example of FIG. 6 shows that the areas A1-A2 and A4-A5 are set to be reduction area, and the remaining area A3 is set to be the non-reduction area. In this example, the states of the areas A1 to A5 is represented by (1, 1, 0, 1, 1) , and light passing through the areas A1-A2 and A4-A5 is absorbed at the specific rate.

The example of FIG. 7 shows that the areas A1 and A4-A5 are set to be reduction area, and the remaining areas A2-A3 are set to be the non-reduction area. In this example, the states of the areas A1 to A5 is represented by (1, 0, 0, 1, 1) , and light passing through the areas A1 and A4-A5 is absorbed at the specific rate.

The example of FIG. 8 shows that the areas A2 and A4 are set to be reduction area, and the remaining areas A1, A3 and A5 are set to be the non-reduction area. In this example, the states of the areas A1 to A5 is represented by (0, 1, 0, 1, 0) , and light passing through the areas A2 and A4 is absorbed at the specific rate.

The example of FIG. 9 shows that the areas A1, A3 and A5 are set to be reduction area, and the remaining areas A2 and A4 are set to be the non-reduction area. In this example, the states of the areas A1 to A5 is represented by (1, 0, 1, 0, 1) , light passing through the areas A1, A3 and A5 is absorbed at the specific rate.

As mentioned above, various patterns formed by the reduction and non-reduction areas of the ID controller 11 are realized by changing combination of areas set in the reduction or non-reduction area among the areas A1 to A5. The MTF curve of the optical apparatus may be changed in accordance with the pattern formed by the reduction and non-reduction areas. Accordingly, the device 10 may finely control the MTF characteristics of the optical apparatus.

For example, the processor 14 may control the ID controller 11 to form the pattern corresponding to (1, 1, 0, 1, 1) . In this case, the MTF curve of the optical apparatus is as shown in FIG. 10. FIG. 10 shows a first example of the MTF curve of the optical apparatus according to the embodiment of the present disclosure.

In FIG. 10, a horizontal axis indicates a spatial frequency (cycles/mm) of the image sensor 13, and a vertical axis indicates a magnitude of modulation. Also, a solid curve indicates the MTF curve in the case of (1, 1, 0, 1, 1) , and a dash-dotted curve indicates a reference level corresponding to a condition that the ID controller 11 maintains an intensity distribution of light before and after passing therethrough.

Comparing the solid curve with the dash-dotted curves in FIG. 10 shows that the MTF curve in the case of (1, 1, 0, 1, 1) lowers enough at around 200 on the horizontal axis that is the Nyquist frequency when the pixel pitch of the image sensor 13 is that in a case of the 2x2 binning. This results in reduction of the Moire effect when the pixel pitch of the image sensor 13 is that in the case of the 2x2 binning.

Likewise, the processor 14 may control the ID controller 11 to form the pattern corresponding to (1, 0, 1, 0, 1) . In this case, the MTF curve of the optical apparatus is as shown in FIG. 11. FIG. 11 shows a second example of the MTF curve of the optical apparatus according to the embodiment of the present disclosure.

In FIG. 11, a horizontal axis indicates a spatial frequency (cycles/mm) of the image sensor 13, and a vertical axis indicates a magnitude of modulation. Also, a solid curve indicates the MTF curve in the case of (1, 0, 1, 0, 1) , and a dash-dotted curve indicates a reference level corresponding to a condition that the ID controller 11 maintains an intensity distribution of light before and after passing therethrough.

Comparing the solid curve with the dash-dotted curves in FIG. 11 shows that the MTF curve in the case of (1, 0, 1, 0, 1) lowers enough at around 200 on the horizontal axis that is the Nyquist frequency when the pixel pitch of the image sensor 13 is that in the case of the 2x2 binning. Further, the MTF curve lowers enough at around 100 on the horizontal axis that is the Nyquist frequency when the pixel pitch of the image sensor 13 is that in the case of the 4x4 binning. This results in reduction of the Moire effect when the pixel pitch of the image sensor 13 is that in the case of each of the 2x2 binning and the 4x4 binning.

(Operation of the device) Following describes operation of the device 10 with reference to FIG. 12. FIG. 12 shows a flowchart for describing a method implemented by the device according to the embodiment of the present disclosure.

At a step of S101, the ID controller 11 performs changing intensity distribution of light passing through the ID controller 11. Specifically, the ID controller 11 performs reducing intensity of light passing through at least one reduction area thereof to change the intensity distribution of light entering the lens system 12 in accordance with a pixel pitch of the image sensor 13. As mentioned above, the image sensor 13 is a binning type image sensor capable of changing the pixel pitch thereof.

At a step of S102, the image sensor 13 performs receiving light that has passed through the lens system 12.

At a step of S103, the processor 14 performs generating an image based on output signals from the image sensor 13.

At a step of S104, the processor 14 determines whether binning operation on the image sensor 13 is to be performed.

For example, the processor 14 may determine whether instructions to perform the binning operation is received. If the processor 14 receives the instructions to perform the binning operation, processing proceeds to a step S105. If the processor 14 does not receive the instructions to perform the binning operation, processing proceeds to the step S101.

At a step of S105, the processor 14 controls the image sensor 13 to change the pixel pitch thereof.

For example, when the processor 14 receives the instructions to perform the 2x2 binning, the processor 14 controls the image sensor 13 to combine each set of adjacent 4 pixels into one virtually combined pixel to change the pixel pitch. Also, when the processor 14 receives the instructions to perform the 4x4 binning, the processor 14 controls the image sensor 13 to combine each set of adjacent 16 pixels into one virtually combined pixel to change the pixel pitch.

At a step of S106, the processor 14 performs changing the pattern of the reduction area of the ID controller 11.

For example, when the pixel pitch of the image sensor 13 is that in the case of the 2x2 binning, the processor 14 controls the ID controller 11 to set the reduction pattern suitable for the changed pixel pitch, such as (1, 1, 0, 1, 1) . Also, when the pixel pitch of the image sensor 13 is that in the case of the 4x4 binning, the processor 14 controls the WF controller 11 to set the deformation pattern suitable for the changed pixel pitch, such as (1, 0, 1, 0, 1) .

After completion of processing at the step of S106, processing proceeds to the step of S101.

According to the method shown in FIG. 12, the intensity distribution of light entering the lens system 12 may be optimized in accordance with the pixel pitch of the image sensor 13, thereby lowering the MTF curve of the optical apparatus enough at the Nyquist frequency relevant to the current pixel pitch. Lowering the MTF curve at the Nyquist frequency may cause reduction of the Moire effect appearing on the generated image. Accordingly, the Moire effect may be effectively reduced even though the pixel pitch of the image sensor 13 is changed by the binning operation.

(Preferable configurations of the reduction area) Following describes some of preferable configurations of the reduction areas of the ID controller 11 and performance thereof, with reference to FIGs. 13A to 15B. In this case, the ID controller 11 is divided into ten donut-shaped areas each having a predetermined width, a state of each donut-shaped area is changeable between transparent and reduction states.

FIG. 13A shows a first preferable configuration of the reduction areas of the ID controller 11. In FIG. 13A, the white-colored portions represent transparent areas that incident light into the ID controller 11 may pass therethrough, and the black-colored portions represent the reduction areas. Configuration shown in FIG. 13A is expressed by (0, 1, 1, 0, 1, 1, 0, 1, 1, 1) . In this case, the MTF curve in the case of FIG. 13A becomes a solid-line of FIG. 13B in accordance with our computer simulation. FIG. 13B shows the MTF curve corresponding to the first preferable configuration of the reduction area. In FIG. 13B, a dotted-line represents the MTF curve in a case that all areas of the ID controller 11 is set to be the transparent state.

Comparing the solid-line with the dotted-line in FIG. 13B shows that the MTF curve in the case of (0, 1, 1, 0, 1, 1, 0, 1, 1, 1) effectively lowers enough at around 200 on the horizontal axis that is the Nyquist frequency when the pixel pitch of the image sensor 13 is that in the case of the 2x2 binning. This results in effective reduction of the Moire effect in at least the case of the 2x2 binning.

FIG. 14A shows a second preferable configuration of the reduction areas of the ID controller 11. In FIG. 14A, the white-colored portions represent transparent areas that incident light into the ID controller 11 may pass therethrough, and the black-colored portions represent the reduction areas. Configuration shown in FIG. 14A is expressed by (1, 0, 1, 1, 0, 0, 1, 0, 0, 0) . In this case, the MTF curve in the case of FIG. 14A becomes a solid-line of FIG. 14B in accordance with our computer simulation. FIG. 14B shows the MTF curve corresponding to the second preferable configuration of the reduction area. In FIG. 14B, a dotted-line represents the MTF curve in a case that all areas of the ID controller 11 is set to be the transparent state.

Comparing the solid-line with the dotted-line in FIG. 14B shows that the MTF curve in the case of (1, 0, 1, 1, 0, 0, 1, 0, 0, 0) effectively lowers enough at around 200 on the horizontal axis that is the Nyquist frequency when the pixel pitch of the image sensor 13 is that in the case of the 2x2 binning. This results in effective reduction of the Moire effect in at least the case of the 2x2 binning.

FIG. 15A shows a third preferable configuration of the reduction areas of the ID controller 11. In FIG. 15A, the white-colored portions represent transparent areas that incident light into the ID controller 11 may pass therethrough, and the black-colored portions represent the reduction areas. Configuration shown in FIG. 15A is expressed by (1, 0, 0, 1, 0, 0, 1, 0, 0, 0) . In this case, the MTF curve in the case of FIG. 15A becomes a solid-line of FIG. 15B in accordance with our computer simulation. FIG. 15B shows the MTF curve corresponding to the third preferable configuration of the reduction area. In FIG. 15B, a dotted-line represents the MTF curve in a case that all areas of the ID controller 11 is set to be the transparent state.

Comparing the solid-line with the dotted-line in FIG. 15B shows that the MTF curve in the case of (1, 0, 0, 1, 0, 0, 1, 0, 0, 0) effectively lowers enough at around 200 on the horizontal axis that is the Nyquist frequency when the pixel pitch of the image sensor 13 is that in the case of the 2x2 binning. This results in effective reduction of the Moire effect in at least the case of the 2x2 binning.

The foregoing disclosure merely discloses exemplary embodiments, and is not intended to limit the protection scope of the present invention. It will be appreciated by those skilled in the art that the foregoing embodiments and all or some of other embodiments and modifications which may be derived based on the scope of claims of the present invention will of course fall within the scope of the present invention.

Claims

An optical apparatus comprising:

a lens system;

an image sensor configured to receive light passing through the lens system, wherein the image sensor is a binning type image sensor capable of changing a pixel pitch thereof; and

an intensity controller configured to reduce intensity of light passing through at least one reduction area thereof to change intensity distribution of light entering the lens system in accordance with the pixel pitch of the image sensor.
The optical apparatus according to claim 1, wherein

the at least one reduction area is configured so that a modulation transfer function (MTF) curve of the optical apparatus lowers enough at around a Nyquist frequency corresponding to the pixel pitch of the image sensor.
The optical apparatus according to claim 1 or 2, wherein

the intensity controller is an intensity controlling mask for reducing intensity of light passing through at least one reduction area thereof.
The optical apparatus according to claim 3, wherein

the intensity controlling mask is an electrochromic device, or a liquid crystal retarder.
The optical apparatus according to claim 3 or 4, wherein

the intensity controlling mask is divided into a plurality of ring-shaped areas centered on an optical axis of the lens system, and each ring-shaped area is capable of being a reduction area with a low transmittance or a non-reduction area with a high transmittance.
A method for reducing a Moire effect, comprising:

reducing, by an intensity controller, intensity of light passing through at least one reduction area of the intensity controller to change intensity distribution of light entering the lens system in accordance with a pixel pitch of an image sensor that is a binning type image sensor capable of changing the pixel pitch thereof; and

receiving, by the image sensor, light passing through the lens system.
The method according to claim 6, wherein

the at least one reduction area is determined so that a modulation transfer function (MTF) curve of an optical apparatus including the intensity controller and the lens system lowers enough at around a Nyquist frequency corresponding to the pixel pitch of the image sensor.
The method according to claim 6 or 7, wherein

the intensity controller is an intensity controlling mask for reducing intensity of light passing through at least one reduction area thereof.
The method according to claim 8, wherein

the intensity controlling mask is an electrochromic device, or a liquid crystal retarder.
The method according to claim 8 or 9, wherein

the intensity controlling mask is divided into a plurality of ring-shaped areas centered on an optical axis of the lens system, and each ring-shaped area is capable of being a reduction area with a low transmittance or a non-reduction area with a high transmittance.
A device comprising:

the optical apparatus according to any one of claims 1 to 5;

a processor configured to generate an image based on output signals from the image sensor to store the image in a memory.
A non-transitory computer-readable storage medium storing a program that causes a computer to perform the method according to any one of claims 6 to 10.