Image sensor which can adjust brightness information to fall in a predetermined range

[0001] This application is a divisional application of applicant's earlier application, Ser. No. 14/037,375, filed 2013 Sep. 26, and is included herein by reference.

[0002] 1. Field of the Invention

[0003] The present invention relates to an image sensing method and an image sensor utilizing the method, and particularly relates to an image sensing method and an image sensor utilizing the method that can adjust background light image brightness of the image sensor to be more uniform.

[0004] 2. Description of the Prior Art

[0005] An image sensor is an apparatus that can transfer light to voltage charge, and processes the voltage charge to generate digital signals constituting the image. Such kind of digital signals can be stored to a storage apparatus or be output to a display to display an image corresponding to the digital signals. Such technology is applied to various kinds of electronic apparatuses, for example, a digital camera, a video camera, a mobile phone or a mouse.

[0006] The image sensor can be applied to touch control technology. FIG. 1 is a schematic diagram illustrating a prior art optical touch control apparatus 100. As shown in FIG. 1, the optical touch control apparatus 100 comprises an image sensor 102, bar shape light guiding devices 105, 109 and light emitting diodes 103, 107, 111, 113. The light guiding devices 105, 109 are provided at two sides of the sensing region 101. The light emitting diodes 103, 107, 111, 113 are located at the ends of the light guiding devices 105, 109, such that the light can be projected to the sensing region 101 via the light guiding devices 105, 109. Also, the image sensor 102 is provided opposite to the light guiding devices 105, 109.

[0007] FIG. 2 is a schematic diagram illustrating brightness distribution for the background light image derived by a prior art image sensor. As shown in FIG. 2, the brightness distribution of the background light image is non-uniform. One possible reason for such situation is that the intensities for the light emitted from the light guiding devices 105, 109 are different. Such situation may be caused by other reasons, however. Such informality may cause some problems. For example, if some objects such as a finger is put on the sensing region 101, the light is blocked such that a dark image is formed. For example, the dark image regions Ob₁, Ob₂, Ob₃ and Ob₄ in FIG. 2. Therefore, the optical touch control apparatus 100 utilizes the location of the dark image regions to compute the location and the barycentre of the object.

[0008] However, if the brightness distribution of the background light image is non-uniform, the location and the barycentre of the object may be wrongly determined. For example, the dark image regions Ob₁, Ob₂, Ob₃ and Ob₄ in FIG. 2 indicate the existence of object. The location and the barycentre of the object causing the dark image regions Ob₁, Ob₂ can be correctly computed since the brightness distribution of the background light image for the locations thereof are uniform. However, the location and the barycentre of the object causing the dark image regions Ob₃, Ob₄ may be wrongly computed since the brightness distribution of the background light image for the locations thereof are non-uniform.

[0009] Therefore, one objective of the present invention is to provide an image sensor and an image sensing method to control the brightness of the background light image to be more uniform.

[0010] Another objective of the present invention is to provide an image sensor and an image sensing method, which set different amplifying ratios to the image sensing units in different rows and columns in the image sensing matrix of the image sensor. Such that the brightness of the background light image can be more uniform.

[0011] One embodiment of the present invention discloses an image sensor, which comprises: an image sensing matrix, comprising at least one image sensing unit, for generating at least one image sensing signal according to a sensed image; an analog to digital converter, for converting the image sensing signal to a digital image sensing signal; an adjusting unit, for adjusting the digital image sensing signal to be an adjusted digital image sensing signal according to at least one adjusting parameter and the digital image sensing signal; an operational circuit, for computing at least part of brightness of the sensed image sensed by the image sensing unit according to the adjusted digital image sensing signal to generate at least one operational brightness signal; and a control unit, for adjusting the adjusting parameter, such that brightness information generated based on brightness values, which corresponds to the operational brightness signal, falls in a predetermined range.

[0012] Still another embodiment of the present invention discloses an image sensor, comprising: an image sensing matrix, comprising a plurality of image sensing units, for generating a plurality of image sensing signals according to a sensed image; an analog to digital converter, for converting the image sensing signals to a plurality of digital image sensing signals; an adjusting unit, for adjusting the digital image sensing signals to be a plurality of adjusted digital image sensing signals according to a plurality of adjusting parameters and the digital image sensing signals; an operational circuit, for computing at least part of brightness of the sensed image sensed by the image sensing units according to the adjusted digital image sensing signals to generate a plurality of operational brightness signals; wherein the adjusting unit utilizes at least two of the adjusting parameters with different values to adjust two of the image sensing signals.

[0013] In view of above-mentioned embodiment, the distribution for the background light image brightness of the image sensing apparatus can be adjusted to be normal via adjusting the amplifying parameter or the adjusting parameter, without complicated computing steps. By this way, the problem of wrongly determining the location and the barycentre of the object can be solved. Additionally, utilizing different amplifying parameters or adjusting parameters to process image sensing signals corresponding to different image sensing units can enlarger the application range for the image sensor of the present invention.

[0014] These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

[0024] FIG. 3 is a schematic diagram illustrating an image sensor 300 according to one embodiment of the present invention. Please note the embodiment in FIG. 3 is only for example and does not mean to limit the scope of the present invention. The image sensor 300 comprises an image sensing matrix 301, a control unit 302, a signal reading circuit 303, an amplifier 305, an analog to digital converter 307 and an operational circuit 309. The image sensing matrix 301 includes at least one image sensing unit PIX₁₁-PIX_nm. In this embodiment, the image sensing units are pixels, and the image sensing matrix is a pixel matrix. The image sensing units can be other pixels, however. The image sensing units PIX₁₁-PIX_nm generate at least one image sensing signals according to a sensed image. The signal reading circuit 303 is arranged to read the image sensing signals IS₁₁-IS_nm. The amplifier 305 amplifies the image sensing signals IS₁₁-IS_nm to be amplified image sensing signals AIS₁₁-AIS_nm according to at least one amplifying parameter. The analog to digital converter 307 transfers the amplified image sensing signals AIS₁₁-AIS_nm to the digital amplified image sensing signals DAIS₁₁-DAIS_nm. The operational circuit 309 computes at least part of brightness of the sensed image sensed by the image sensing units PIX₁₁-PIX_nm according to the digital amplified image sensing signals DAIS₁₁-DAIS_nm to generate at least one operational brightness signal OL₁₁-OL_nm. The operational circuit 309 can be regarded as computing at least part of brightness of the sensed image sensed by the image sensing units PIX₁₁-PIX_nm according to the amplified image sensing signals AIS₁₁-AIS_nm to generate at least one operational brightness signal OL₁₁-OL_nm since the digital amplified image sensing signals DAIS₁₁-DAIS_nm is a digital version of the amplified image sensing signals AIS₁₁-AIS_nm.

[0025] The control unit 302 is arranged to adjust the amplifying parameter of the amplifier 305, such that brightness information generated based on brightness, which corresponds to the operational brightness signals OL₁₁-OL_nm, falls in a predetermined range. For example, the operational brightness signal OL₁₁, OL₁₂, OL₁₃, which have brightness values Lum₁₁, Lum₁₂ and Lum₁₃, are acquired via computing the amplified image sensing signals AIS₁₁, AIS₁₂, AIS₁₃. Therefore, it means the brightness values of the image sensing units PIX₁₁, PIX₁₂, PIX₁₃ are Lum₁₁, Lum₁₂ and Lum₁₃. However, the amplified image sensing signals AIS₁₁, AIS₁₂, AIS₁₃ are adjusted to be amplified image sensing signals AIS₁₁′, AIS₁₂′, AIS₁₃′ after the amplifying parameters are adjusted, thus the brightness values become to Lum₁₁′, Lum₁₂′ and Lum₁₃′, which means the brightness values of the image sensing units PIX₁₁, PIX₁₂, PIX₁₃ are adjusted from Lum₁₁, Lum₁₂ and Lum₁₃ to Lum₁₁′, Lum₁₂′ and Lum₁₃′. The control unit 302 controls the brightness information generated based on the brightness values of the image sensing units PIX₁₁-PIX_nm to fall in a predetermined range. The brightness information will be described in the following for more detail. Please note the amplifying parameters for amplifying image sensing signals IS₁₁-IS_nm can be the same but also can be different. In one embodiment, the amplifier 305 utilizes at least two different amplifying parameters to amplify two image sensing signals. For example, utilizing a first amplifying parameter to amplify the image sensing signal IS₃₂, but utilizing a second amplifying parameter to amplify the image sensing signal IS₄₆. The purpose of such action can be controlling the brightness information generated based on the brightness value of the image sensing units PIX₁₁-PIX_nm to fall in a predetermined range, the same as above-mentioned purpose, but can be other purposes. Additionally, in another embodiment, the amplifier 305 utilizes at least two of the amplifying parameters with different values to amplify two of the image sensing signals only when the images sensing units are in different rows and different columns.

[0026] FIG. 4 is an example for the detail structure of the image sensing matrix 301 in FIG. 3. The cross voltage of the photodiode PD is charged to V_rst if the reset signal RES controls the NMOS M₂ to be conductive. The signal reading units SR₁, SR₂, SR₃ of the signal reading circuit 303 all comprise a voltage charge storing element. The cross voltage of the photodiode PD is transferred to currents via the NMOS M₁ and stored to the voltage charge storing elements in the signal reading units SR₁, SR₂, SR₃, if the sensing unit selecting signals RSEL₁ or RSEL₂ controls the NMOS M₃ to be conductive. Accordingly, the voltage charge stored in the voltage charge storing elements in the signal reading units SR₁, SR₂, SR₃ indicate the light amount sensed by the image sensing units. The voltage charge form the image sensing signals IS₁₁-IS_nm when the voltage charges are output from the signal reading units SR₁, SR₂, SR₃.

[0027] FIG. 5 is a schematic diagram illustrating how to adjust the brightness distribution of the image sensor via adjusting the amplifying parameter in the image sensor. As shown in FIG. 5, the brightness information diagram for the background light image in the prior art is Sh₁, which has a non-uniform distribution. After adjusting the amplifying parameter, the brightness information diagram becomes to have a uniform distribution, such as Sh₂. Such brightness information can include various kinds of information generated by the brightness of the image sensing units. In one embodiment, the brightness information is a sum of brightness values for one row or one column of the image sensing matrix. For example, the brightness information for the X, Y locations of the brightness distribution diagram Sh₂ indicates the brightness value sum for all the image sensing units in the columns at the X, Y positions in the image sensing matrix M₁. In such case, the whole image sensing matrix M₁ can be regarded as the image sensing window). In another embodiment, the image sensing matrix M₂ utilizes a plurality of image sensing units in an image sensing window WOI₁ to sense the image. In such case, the brightness information for the X, Y locations of the brightness distribution diagram Sh₂ indicates the brightness value sum for all the image sensing units in the columns at the X, Y positions in the image sensing window WOI₁ of the image sensing matrix M₂. Also, the number for the image sensing units utilized to generate the brightness information for each row in the image sensing window varies corresponding to the range of the image sensing window. Take FIG. 5 for example, the image sensing window WOI₂ is a irregular shape, such that the number for the image sensing units in one row at the X position is fewer than the number for the image sensing units in one row at the Y position.

[0028] In one embodiment, the control unit 302 controls the amplifier 305 to utilize one of the amplifying parameters to amplify one of the image sensing signals to form the amplified image sensing signal. That is, the amplified image sensing signals are summed to generate the sum of brightness values after the amplifier 305 amplifies each image sensing signal to generate the amplified image sensing signal. In another embodiment, the control unit 302 controls a plurality of image sensing signals to be summed to form a combinational image sensing signal, such that the amplifier 305 utilizes one of the amplifying parameters to amplify the combinational image sensing signal to generate the amplified image sensing signal. That is, the image sensing signals are amplified to the amplified image sensing signals after summing. The devices for summing the image sensing signals or the amplified image sensing signals are not shown in FIG. 3, but persons skilled in the art will easily understand how to sum the image sensing signals to acquire the sum of brightness values, thus it is omitted for brevity here.

[0029] In one embodiment, the brightness information is an average for the brightness values of one row or one column of the image sensor. Alternatively, the brightness information is the difference of the brightness values corresponding to at least two of the operational brightness signals for one row or one column of the image sensor, for example, the difference between the max brightness value and the min brightness value in one row or one column. The image sensing units utilized for computing can locate in a whole row or a whole column of an image sensing matrix, such as the image sensing matrix M₁ shown in FIG. 5. Alternatively, the image sensing units utilized for computing can locate in a row or a column of a regular shape image sensing window of an image sensing matrix, such as the image sensing matrix M₂ shown in FIG. 5. Additionally, the image sensing units utilized for computing can locate in a row or a column of an irregular shape image sensing window of an image sensing matrix, such as the image sensing matrix M₃ shown in FIG. 5.

[0030] FIG. 6 is a schematic diagram illustrating the structure of the control unit for selecting amplifying parameters for each pixel, according to one embodiment of the present invention. Such structure comprises a plurality of multiplexers Mux₁, Mux₂ and Mux₃, which can be incorporated into the control unit but also can be independent from the control unit. As shown in FIG. 6, the image sensing matrix 301 is a matrix with M columns×N rows. The multiplexers Mux₁, Mux₂ select image sensing unit gains of columns from the multiplexer via the selecting signal Sel_c, and then the multiplexer Mux₃ selects image sensing unit gains of rows via the selecting signal Sel_R. That is, the circuit shown in FIG. 6 selects gain values based on addresses of the image sensing units (in which row and which column). However, the scope of the present invention is not limited to the embodiment shown in FIG. 6, any circuits that can reach the function for the circuit in FIG. 6 should fall in the scope of the present invention.

[0031] The amplifier 305 can utilize the same amplifying parameters to amplify each image sensing signals IS₁₁-IS_nm, but also can utilize different amplifying parameters to amplify at least part of the image sensing signals IS₁₁-IS_nm. In one embodiment, the image sensing units in the same row or the same column utilizes the same amplifying parameters. The amplifying parameter can be set to desired brightness information. In one embodiment, the control unit 302 determines values of the amplifying parameters that each of the image sensing unit corresponds to according to a brightness value of the image sensing signal that the image sensing unit derives in a previous image or a current image.

[0032] FIG. 7 is a schematic diagram illustrating an image sensor according to another embodiment of the present invention. One difference between the embodiments shown in FIG. 3 and FIG. 7 is that the embodiment shown in FIG. 3 adjusts the amplifying parameters of the analog image sensing signals, but the embodiment shown in FIG. 7 firstly amplifies and digitalizes the analog image signals IS₁₁-IS_nm to generate the digital amplified image signals DAIS₁₁-DAIS_nm, and then utilizes an adjusting unit to adjust the digital amplified image signals DAIS₁₁-DAIS_nm to generate the adjusted digital image sensing signals ADIS₁₁-ADIS_nm. Therefore, comparing with the embodiment in FIG. 2, the embodiment in FIG. 7 further comprise an adjusting unit 701, which is also controlled by the control unit 302. In one embodiment the amplifier 305 is excluded such that the analog image signals IS₁₁-IS_nm are directly adjusted by the adjusting unit 701 without being amplified. How to adjust a digital signal to become larger or smaller is well known by persons skilled in the art, and the selecting, setting for the adjusting parameter are well known by persons skilled in the art, thus it is omitted for brevity here. Please note the adjusting parameters for adjusting the digital amplified image signals DAIS₁₁-DAIS_nm can be the same or different. In one embodiment, the adjusting unit 701 utilizes at least two adjusting parameters to adjust two of the digital amplified image signals DAIS₁₁-DAIS_nm. For example, utilizing a first amplifying parameter to amplify the digital amplified image signals DAIS₃₂, but utilizing a second amplifying parameter to amplify the digital amplified image signals DAIS₄₆. The purpose of such action can be controlling the brightness information generated based on the brightness value of the image sensing units PIX₁₁-PIX_nm to fall in a predetermined range, the same as above-mentioned purpose, but can be other purposes. Additionally, in another embodiment, the adjusting unit 701 utilizes at least two of the adjusting parameters with different values to adjust two of the image sensing signals only when the images sensing units are indifferent rows and different columns.

[0033] FIG. 8 is a flow chart illustrating an image sensing method according to one embodiment of the present invention. The method corresponding to the embodiment shown in FIG. 3 and includes the following steps:

Step 801

[0034] Utilize at least one image sensing unit (ex. PIX₁₁-PIX_nm) in an image sensing matrix (ex. 301) to generate at least one image sensing signal (ex. IS₁₁-IS_nm) according to a sensed image.

Step 803

[0035] Utilize an amplifier (ex. 305) to amplify the image sensing signal to be an amplified image sensing signal according to at least one amplifying parameter (ex. AIS₁₁-AIS_nm).

Step 805

[0036] Compute at least part of brightness of the sensed image sensed by the image sensing unit according to the amplified image sensing signal to generate at least one operational brightness signal (ex. OL₁₁-OL_nm).

Step 807

[0037] Adjust the amplifying parameter, such that brightness information generated based on the brightness value, which corresponds to the operational brightness signal, falls in a predetermined range.

[0038] FIG. 9 is a flow chart illustrating an image sensing method according to another embodiment of the present invention. The method corresponding to the embodiment shown in FIG. 7 and includes the following steps:

Step 901

[0039] Utilize at least one image sensing unit (ex. PIX₁₁-PIX_nm) in an image sensing matrix (ex. 301) to generate at least one image sensing signal (ex. IS₁₁-IS_nm) according to a sensed image.

Step 903

[0040] Generate a digital image sensing signal according to the image sensing signal.

[0041] As above-mentioned description, the image sensing signal can be amplified and digitalized to generate the digital image sensing signal, or be directly digitalized to generate the digital image sensing signal.

Step 905

[0042] Utilize an adjusting unit (ex. 701) to adjust the image sensing signal to be an adjusted digital image sensing signal according to at least one adjusting parameter (ex. ADIS₁₁-ADIS_nm).

Step 907

[0043] Compute at least part of brightness of the sensed image sensed by the image sensing unit according to the adjusted digital image sensing signal to generate at least one operational brightness signal (ex. OL₁₁-OL_nm).

Step 909

[0044] Adjust the adjusting parameter, such that brightness information generated based on the brightness value, which corresponds to the operational brightness signal, falls in a predetermined range.

[0045] In view of above-mentioned embodiment, the distribution for the background light image brightness of the image sensing apparatus can be adjusted to be normal via adjusting the amplifying parameter or the adjusting parameter, without complicated computing steps. By this way, the problem of wrongly determining the location and the barycentre of the object can be solved. Additionally, utilizing different amplifying parameters or adjusting parameters to process image sensing signals corresponding to different image sensing units can enlarger the application range for the image sensor of the present invention.

[0046] Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.