TWI540899B - Image sensor and operating method thereof - Google Patents
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Description
本發明係關於一種影像感測器，特別係關於一種運用類比差分以消除環境光干擾的影像感測器及其運作方法。 The invention relates to an image sensor, in particular to an image sensor using analog differential to eliminate ambient light interference and a method for operating the same.
習知一影像感測器通常具有複數陣列排列的感測像素，其中該影像感測器之一種運作方法可使用滾動快門(Rolling Shutter)，例如以一控制信號依序啟動該影像感測器中每一列之該等感測像素以擷取一影像。由於每一列之該等感測像素為依序啟動而非同時啟動(亦即每一列之該等感測像素開始曝光的時間不同)，擷取快速移動的物件影像時，使用滾動快門所擷取的影像可能會有失真(distortion)的問題。 A conventional image sensor generally has a plurality of arrays of sensing pixels. One method of operating the image sensor can use a rolling shutter, for example, sequentially starting the image sensor with a control signal. Each of the sensing pixels of each column captures an image. Since the sensing pixels of each column are sequentially activated rather than simultaneously activated (that is, the time at which the sensing pixels of each column start to be exposed), when the fast moving object image is captured, the rolling shutter is used to capture The image may have a problem with distortion.
另一種影像感測器之運作方法可使用全域快門(Global Shutter)，例如以一控制信號同時啟動該影像感測器中全部感測像素以致於每一列之該等感測像素可在同一時間開始曝光以擷取一影像，因此，使用全域快門的影像感測器可避免所述影像失真的問題。 Another method of operating the image sensor can use a Global Shutter, for example, simultaneously starting all the sensing pixels in the image sensor with a control signal so that the sensing pixels of each column can start at the same time. Exposure to capture an image, therefore, the use of a global shutter image sensor can avoid the problem of image distortion.
然而，使用全域快門的影像感測器在擷取影像時，為了消除環境光的干擾或降低影像雜訊，習知一種解決方式係透過影像後處理的方式將兩張數位影像圖框直接相減以獲得一差分影像圖框。例如，請參照第1A及1B圖，第1A圖為習知使用全域快門之一影像感測器91之影像擷取之時序圖。假設該影像感測器91具有4個感測像素列R1~R4，在一第一期間P1，一光源開啟一預設時間且該等感測像素列R1~R4同時曝光，接著關閉該光源並依序讀取該感測像素列R1至R4以輸出一第一影像信號；在一第二期間P2，該光源關閉並以該預設時間同時曝光該等感測像素列R1~R4並依序讀取該感測像素列R1至R4以輸出一第二影像信號。 However, when using an image sensor with a global shutter to eliminate ambient light interference or reduce image noise when capturing images, a conventional solution is to directly subtract two digital image frames by image post-processing. Get a differential image frame. For example, please refer to FIGS. 1A and 1B. FIG. 1A is a timing diagram of image capture of a conventional image sensor 91 using a global shutter. It is assumed that the image sensor 91 has four sensing pixel columns R1 R R4. During a first period P1, a light source is turned on for a predetermined time and the sensing pixel columns R1 R R4 are simultaneously exposed, and then the light source is turned off. The sensing pixel columns R1 to R4 are sequentially read to output a first image signal; in a second period P2, the light source is turned off and the sensing pixel columns R1 R R4 are simultaneously exposed at the preset time and sequentially The sensing pixel columns R1 to R4 are read to output a second image signal.
接著，請參照第1B圖，該影像感測器91所輸出之該第一 影像信號先透過一類比數位轉換器93轉換成一第一數位信號9a並儲存在一數位緩衝區95。接著，將該第二影像信號透過該類比數位轉換器93轉換成一第二數位信號9b。最後，再將該第一數位信號9a減去該第二數位信號9b以獲得一消除環境光的第三數位信號9c。然而，此種方法中，包含該影像感測器91之系統需設置該數位緩衝區95且該影像感測器91必須連續輸出兩張影像圖框(例如根據該第一數位信號9a及該第二數位信號9b所形成之影像圖框)才能獲得一張處理後的影像圖框(例如根據該第三數位信號9c所形成之影像圖框)。 Next, please refer to FIG. 1B, the first output by the image sensor 91 The image signal is first converted to a first digit signal 9a by an analog-to-digital converter 93 and stored in a digital buffer 95. Then, the second image signal is converted into a second digit signal 9b through the analog-to-digital converter 93. Finally, the first digital signal 9a is subtracted from the second digital signal 9b to obtain a third digital signal 9c for eliminating ambient light. However, in this method, the system including the image sensor 91 needs to set the digital buffer 95 and the image sensor 91 must continuously output two image frames (for example, according to the first digital signal 9a and the first The image frame formed by the binary signal 9b can obtain a processed image frame (for example, an image frame formed according to the third digital signal 9c).
有鑑於此，本發明提出一種運用類比差分以消除環境光干擾的方法及使用該方法之影像感測器。 In view of this, the present invention proposes a method of using analog difference to eliminate ambient light interference and an image sensor using the same.
本發明之一目的在提供一種影像感測器，其所輸出的每一張類比影像已消除環境光之干擾。 It is an object of the present invention to provide an image sensor in which each analog image output has eliminated interference from ambient light.
本發明另一目的在提供一種影像感測器，其可降低接近一倍的功率消耗且不需使用一數位緩衝器用以儲存一影像圖框供進行兩張數位影像圖框之差分運算。 Another object of the present invention is to provide an image sensor that reduces power consumption by nearly double and does not require the use of a digital buffer for storing an image frame for performing differential operations on two digital image frames.
為達上述目的，本發明提供一種影像感測器。該影像感測器包含一光電轉換電路及一輸出電路。該光電轉換電路用以相對一高準位信號期間儲存一第一電荷量及相對一低準位信號期間儲存一第二電荷量。該輸出電路包含一第一儲存電路及一第二儲存電路分別用以儲存轉移自該光電轉換電路之該第一電荷量及該第二電荷量，並用以比較該第一儲存電路中之該第一電荷量及該第二儲存電路中之該第二電荷量以輸出一類比影像信號，其中，該高準位信號及該低準位信號分別用以驅動一光源之啟閉，該光電轉換電路相對該低準位信號期間依序轉移該第一電荷量至該第一儲存電路、儲存該第二電荷量及轉移該第二電荷量至該第二儲存電路。 To achieve the above object, the present invention provides an image sensor. The image sensor comprises a photoelectric conversion circuit and an output circuit. The photoelectric conversion circuit is configured to store a second charge amount during a period of storing a first charge amount and a low level signal relative to a high level signal. The output circuit includes a first storage circuit and a second storage circuit for storing the first amount of charge and the second amount of charge transferred from the photoelectric conversion circuit, and comparing the first of the first storage circuits An amount of charge and the second amount of charge in the second storage circuit to output an analog image signal, wherein the high level signal and the low level signal are respectively used to drive opening and closing of a light source, the photoelectric conversion circuit The first charge amount is sequentially transferred to the first storage circuit, the second charge amount is stored, and the second charge amount is transferred to the second storage circuit during the low level signal period.
本發明另提供一種影像感測器之運作方法。該影像感測器包含一光電元件、一像素緩衝電路、一第一儲存電路、一第二儲存電路及一差分單元。該第一儲存電路及該第二儲存電路分別耦接於該差分單元之兩輸入端。該光電元件用以相對一高準位信號及一低準位信號產生光電流儲存至該像素緩衝電路，其中該高準位信號及該低準位信號用以驅動一光 源之啟閉。該運作方法包含：於該高準位信號期間從該光電元件儲存一第一電荷量至該像素緩衝電路；於該低準位信號期間將該像素緩衝電路之該第一電荷量轉移至該第一儲存電路；該第一電荷量轉移後，於該低準位信號期間從該光電元件儲存一第二電荷量至該像素緩衝電路；將該像素緩衝電路之該第二電荷量轉移至該第二儲存電路；以及以該差分單元比較該第一儲存電路及該第二儲存電路中之儲存電荷量以輸出一類比影像信號。 The invention further provides a method for operating an image sensor. The image sensor comprises a photoelectric element, a pixel buffer circuit, a first storage circuit, a second storage circuit and a differential unit. The first storage circuit and the second storage circuit are respectively coupled to the two input ends of the differential unit. The photo-electric component is configured to generate a photocurrent to the pixel buffer circuit with respect to a high-level signal and a low-level signal, wherein the high-level signal and the low-level signal are used to drive a light The source is opened and closed. The method includes: storing a first amount of charge from the photosensor to the pixel buffer circuit during the high-level signal; transferring the first amount of charge of the pixel buffer circuit to the first period during the low-level signal a storage circuit; after the first charge amount is transferred, storing a second amount of charge from the photosensor to the pixel buffer circuit during the low level signal; transferring the second amount of charge of the pixel buffer circuit to the first And storing the amount of stored charge in the first storage circuit and the second storage circuit to output an analog image signal.
本發明另提供一種影像感測器。該影像感測器包含一光電轉換電路、一第一儲存電路、一第二儲存電路及一差分單元。該光電轉換電路用以於一第一期間產生相關一光源及環境光之光電流且於一第二期間產生相關該環境光之光電流。該第一儲存電路用以於該第二期間儲存對應該第一期間之該光電流之一第一電荷量。該第二儲存電路用以在該第一電荷量被儲存後，儲存對應該第二期間之該光電流之一第二電荷量。該差分單元包含兩輸入端分別耦接該第一儲存電路及該第二儲存電路，並用以比較該第一儲存電路及該第二儲存電路中之該第一電荷量及該第二電荷量以消除該環境光之干擾。 The invention further provides an image sensor. The image sensor includes a photoelectric conversion circuit, a first storage circuit, a second storage circuit, and a differential unit. The photoelectric conversion circuit is configured to generate a photocurrent of a light source and ambient light during a first period and generate a photocurrent related to the ambient light during a second period. The first storage circuit is configured to store, during the second period, a first amount of the current corresponding to the photocurrent of the first period. The second storage circuit is configured to store a second amount of the photo current corresponding to the second period after the first amount of charge is stored. The differential unit includes two input ends respectively coupled to the first storage circuit and the second storage circuit, and configured to compare the first charge amount and the second charge amount in the first storage circuit and the second storage circuit to Eliminate the interference of the ambient light.
為了讓本發明之上述和其他目的、特徵和優點能更明顯，下文將配合所附圖示，詳細說明如下。此外，於本發明之說明中，相同之構件係以相同之符號表示，於此先述明。 The above and other objects, features, and advantages of the present invention will become more apparent from the accompanying drawings. In the description of the present invention, the same components are denoted by the same reference numerals and will be described.
1、2、3、91‧‧‧影像感測器 1, 2, 3, 91‧‧‧ image sensor
10、10'、31‧‧‧光電轉換電路 10, 10', 31‧‧‧ photoelectric conversion circuit
101‧‧‧光電元件 101‧‧‧Optoelectronic components
102‧‧‧像素電容 102‧‧‧pixel capacitor
103‧‧‧轉移電路 103‧‧‧Transfer circuit
103a‧‧‧第一閘極 103a‧‧‧first gate
103b‧‧‧第二閘極 103b‧‧‧second gate
106‧‧‧第三閘極 106‧‧‧third gate
107‧‧‧第四閘極 107‧‧‧fourth gate
108‧‧‧第五閘極 108‧‧‧ fifth gate
20、32‧‧‧輸出電路 20, 32‧‧‧ output circuit
201、321‧‧‧第一儲存電路 201, 321‧‧‧ first storage circuit
201a、321a‧‧‧比較器 201a, 321a‧‧‧ comparator
201c、202c‧‧‧儲存電容 201c, 202c‧‧‧ storage capacitor
201s、202s‧‧‧開關元件 201s, 202s‧‧‧ switching components
202、322‧‧‧第二儲存電路 202, 322‧‧‧Second storage circuit
205、325‧‧‧差分單元 205, 325‧‧‧Differential unit
30‧‧‧驅動電路 30‧‧‧Drive circuit
35、93‧‧‧類比數位轉換器 35, 93‧‧‧ analog digital converter
37‧‧‧處理器 37‧‧‧ Processor
4‧‧‧成像系統 4‧‧‧ imaging system
5‧‧‧光源 5‧‧‧Light source
70‧‧‧位元線 70‧‧‧ bit line
95‧‧‧數位緩衝區 95‧‧‧ digital buffer
9a‧‧‧第一數位信號 9a‧‧‧first digit signal
9b‧‧‧第二數位信號 9b‧‧‧second digital signal
9c‧‧‧第三數位信號 9c‧‧‧ third digit signal
I5‧‧‧光源強度 I 5 ‧‧‧Light source intensity
IAB‧‧‧環境光強度 I AB ‧‧‧ Ambient light intensity
IL‧‧‧光電流 I L ‧‧‧Photocurrent
Li‧‧‧入射光 Li‧‧‧ incident light
N‧‧‧節點 N‧‧‧ node
P1‧‧‧第一期間 P1‧‧ first period
P2‧‧‧第二期間 P2‧‧‧ second period
Q1‧‧‧第一電荷量 Q 1 ‧‧‧First charge
Q2‧‧‧第二電荷量 Q 2 ‧‧‧second charge
R1~R6‧‧‧感測像素列 R1~R6‧‧‧ Sense Pixel Column
S1~S5‧‧‧步驟 S 1 ~ S 5 ‧ ‧ steps
Sa‧‧‧類比影像信號 Sa‧‧‧ analog image signal
Sc‧‧‧控制信號 Sc‧‧‧ control signal
Sd‧‧‧數位影像信號 Sd‧‧‧ digital image signal
SH‧‧‧高準位信號 S H ‧‧‧ high level signal
SL‧‧‧低準位信號 S L ‧‧‧low level signal
V1‧‧‧第一電壓 V 1 ‧‧‧First voltage
V2‧‧‧第二電壓 V 2 ‧‧‧second voltage
Vout‧‧‧輸出電壓 Vout‧‧‧ output voltage
Vref‧‧‧參考電壓 Vref‧‧‧reference voltage
第1A圖為習知使用全域快門之影像感測器之影像擷取之時序圖。 Figure 1A is a timing diagram of image capture of a conventional image sensor using a global shutter.
第1B圖為習知兩張影像圖框在數位端進行差分運算之方塊圖。 Figure 1B is a block diagram of the differential operation of the two image frames at the digit end.
第2圖為本發明某些實施例之影像感測器之電路圖。 2 is a circuit diagram of an image sensor according to some embodiments of the present invention.
第3圖為本發明某些實施例之影像感測器之運作方法之流程圖。 FIG. 3 is a flow chart of a method for operating an image sensor according to some embodiments of the present invention.
第4圖為對應第2及3圖之複數開關元件之時序圖。 Fig. 4 is a timing chart corresponding to the plurality of switching elements of Figs. 2 and 3.
第5圖為本發明某些實施例之影像感測器之方塊圖。 Figure 5 is a block diagram of an image sensor of some embodiments of the present invention.
第6圖為本發明某些實施例包含複數感測像素之成像系統之示意圖。 Figure 6 is a schematic illustration of an imaging system including a plurality of sensing pixels in accordance with some embodiments of the present invention.
第7圖為對應第6圖之時序圖。 Fig. 7 is a timing chart corresponding to Fig. 6.
第2圖為本發明某些實施例之影像感測器1之電路圖。該影像感測器1係用以感測光能量並轉換成電信號。該影像感測器1包含至少一光電轉換電路10及一輸出電路20，其中該光電轉換電路10之輸出端與該輸出電路20之輸入端之間以一位元線70連接。一影像感測器可具有複數陣列排列的光電轉換電路以作為感測像素，且每一行之該等光電轉換電路之輸出端可透過一位元線電性連接至一輸出電路之輸入端。例如，包含M×N個像素的影像感測器通常具有M×N個光電轉換電路以及M個或N個輸出電路及位元線。為簡化圖式，第2圖僅例示性地繪示該影像感測器1中兩個光電轉換電路10、10'、一個輸出電路20及一條位元線70。可以瞭解的是，該光電轉換電路10及該光電轉換電路10'雖然具有不同標號，但兩者具有相同結構，用以表示該影像感測器1其中一行之兩個感測像素(例如第一行第一列之感測像素及第一行第二列之感測像素)。 Figure 2 is a circuit diagram of an image sensor 1 in accordance with some embodiments of the present invention. The image sensor 1 is used to sense light energy and convert it into an electrical signal. The image sensor 1 includes at least one photoelectric conversion circuit 10 and an output circuit 20, wherein an output end of the photoelectric conversion circuit 10 and an input end of the output circuit 20 are connected by a one-dimensional line 70. An image sensor can have a plurality of arrays of photoelectric conversion circuits as sensing pixels, and the output terminals of the photoelectric conversion circuits of each row can be electrically connected to the input end of an output circuit through a single bit line. For example, an image sensor including M x N pixels typically has M x N photoelectric conversion circuits and M or N output circuits and bit lines. To simplify the drawing, FIG. 2 only exemplarily shows two photoelectric conversion circuits 10, 10', one output circuit 20 and one bit line 70 in the image sensor 1. It can be understood that the photoelectric conversion circuit 10 and the photoelectric conversion circuit 10' have different structures, but have the same structure for indicating two sensing pixels of one line of the image sensor 1 (for example, the first The sensing pixels of the first column and the sensing pixels of the first row and the second column are performed.
必須說明的是，在擷取影像圖框時，該影像感測器1可搭配至少一光源(未繪示)用以提供影像擷取時所需的光，故該光源可稱為補光燈(例如一發光二極體)。該影像感測器1包含一信號產生器或一時序控制器(未繪示)用以依序發出一高準位信號及一低準位信號以驅動該光源之啟閉，但不限於此。其他實施例中，該高準位信號及該低準位信號可由包含該影像感測器1之一成像系統提供，例如由該成像系統之一控制電路提供，且被提供至該影像感測器1。某些實施例中，光源與影像感測器可包含於同一影像感測器封裝中而由一時序控制器同時控制光源與影像感測器的運作。某些實施例中，光源位於影像感測器外部，而該影像感測器可產生該高準位信號及該低準位信號以控制該光源。必須說明的是，雖然此處係分別以一高準為信號及一低準位信號進行說明，然上述信號產生器、時序控制器或控制電路可僅產生高準位信號，而該低準位信號表示未產生 信號，例如信號值為零。 It should be noted that, when capturing an image frame, the image sensor 1 can be combined with at least one light source (not shown) for providing light required for image capturing, so the light source can be called a fill light. (eg a light-emitting diode). The image sensor 1 includes a signal generator or a timing controller (not shown) for sequentially emitting a high level signal and a low level signal to drive the light source to be turned on and off, but is not limited thereto. In other embodiments, the high level signal and the low level signal may be provided by an imaging system including the image sensor 1 , for example, provided by a control circuit of the imaging system, and provided to the image sensor. 1. In some embodiments, the light source and the image sensor can be included in the same image sensor package to simultaneously control the operation of the light source and the image sensor by a timing controller. In some embodiments, the light source is external to the image sensor, and the image sensor can generate the high level signal and the low level signal to control the light source. It should be noted that although the description is made here by a high-precision signal and a low-level signal, the signal generator, the timing controller or the control circuit may only generate a high-level signal, and the low-level signal Signal representation not generated The signal, for example the signal value is zero.
該光電轉換電路10係用以相對一高準位信號期間儲存一第一電荷量Q1及相對一低準位信號期間儲存一第二電荷量Q2，其中該高準位信號驅動該光源開啟而該低準位信號控制該光源關閉。也就是說，該光電轉換電路10儲存該第一電荷量Q1的同時該光源為開啟，而該光電轉換電路10儲存該第二電荷量Q2的同時該光源為關閉。 The photoelectric conversion circuit 10 is configured to store a second charge amount Q 2 during a period of storing a first charge amount Q 1 and a low level signal relative to a high level signal, wherein the high level signal drives the light source to be turned on. The low level signal controls the light source to turn off. That is, the photoelectric conversion circuit 10 stores the first charge amount Q 1 while the light source is turned on, and the photoelectric conversion circuit 10 stores the second charge amount Q 2 while the light source is turned off.
該光電轉換電路10包含一光電元件101、一像素電容102及一轉移電路103。該光電元件101例如可為一光電二極體(photodiode)用以轉換入射光Li為一光電流IL；其中，該光電流IL與該入射光Li之強度相關。該像素電容102則用以儲存該光電流IL為該第一電荷量Q1或該第二電荷量Q2。可以瞭解的是，當該光源開啟時，該入射光Li包含該光源所發出之光及環境光，該光電元件101轉換該光源所發出之光及該環境光為該光電流IL並據以在該像素電容102儲存一電荷量(亦即該第一電荷量Q1)。當該光源關閉時，該入射光Li僅包含該環境光，該光電元件101則轉換該環境光為光電流IL並據以在該像素電容102儲存另一電荷量(亦即該第二電荷量Q2)。必須說明的是，該轉移電路103耦接在該像素電容102與該輸出電路20之間，而在該像素電容102儲存該第二電荷量Q2之前，該轉移電路103先從該像素電容102轉移該第一電荷量Q1至該輸出電路20，接著該第二電荷量Q2被儲存至該像素電容102。 The photoelectric conversion circuit 10 includes a photoelectric element 101, a pixel capacitor 102, and a transfer circuit 103. The photo-electric element 101 can be, for example, a photodiode for converting the incident light Li into a photocurrent I L ; wherein the photocurrent I L is related to the intensity of the incident light Li. The pixel capacitor 102 is configured to store the photo current I L as the first charge amount Q 1 or the second charge amount Q 2 . It can be understood that, when the light source is turned on, the incident light Li includes the light emitted by the light source and the ambient light, and the photoelectric element 101 converts the light emitted by the light source and the ambient light into the photo current I L according to A charge amount (that is, the first charge amount Q 1 ) is stored in the pixel capacitor 102. When the light source is turned off, the incident light Li only contains the ambient light, and the photoelectric element 101 converts the ambient light into a photocurrent I L and accordingly stores another charge amount (ie, the second charge) in the pixel capacitor 102. Quantity Q 2 ). It should be noted that the transfer circuit 103 is coupled between the pixel capacitor 102 and the output circuit 20, and the transfer circuit 103 first passes from the pixel capacitor 102 before the pixel capacitor 102 stores the second charge amount Q 2 . The first amount of charge Q 1 is transferred to the output circuit 20, and then the second amount of charge Q 2 is stored to the pixel capacitor 102.
某些實施例中，該轉移電路103包含開關元件用以根據開關元件之啟閉控制電荷轉移，例如第2圖顯示一第一閘極103a及一第二閘極103b。當該第一電荷量Q1或該第二電荷量Q2儲存在該像素電容102時，第2圖之一節點N具有對應該第一電荷量Q1或該第二電荷量Q2之一電位(V=Q/C)。為了將電荷轉移至該輸出電路20，該轉移電路103之該第一閘極103a例如可為一源極隨耦器電晶體(source follower transistor)並耦接該節點N以輸出電荷至該輸出電路20。另一方面，由於該光電轉換電路10及光電轉換電路10'同時耦接至相同的輸出電路(亦即該輸出電路20)，該光電轉換電路10之該第二閘極103b及該光電轉換電路10'之該第二閘極103b可不同時開啟，以致於該輸出電路20可依序接收該光電轉換電路10及該光電轉換電路10'之電荷。 In some embodiments, the transfer circuit 103 includes a switching element for controlling charge transfer according to the opening and closing of the switching element. For example, FIG. 2 shows a first gate 103a and a second gate 103b. When the first charge amount Q 1 or the second charge amount Q 2 is stored in the pixel capacitor 102, the node N of the second figure has one of the first charge amount Q 1 or the second charge amount Q 2 Potential (V=Q/C). In order to transfer the charge to the output circuit 20, the first gate 103a of the transfer circuit 103 can be, for example, a source follower transistor and coupled to the node N to output a charge to the output circuit. 20. On the other hand, since the photoelectric conversion circuit 10 and the photoelectric conversion circuit 10' are simultaneously coupled to the same output circuit (that is, the output circuit 20), the second gate 103b of the photoelectric conversion circuit 10 and the photoelectric conversion circuit The second gate 103b of 10' may be turned on at the same time, so that the output circuit 20 can sequentially receive the charge of the photoelectric conversion circuit 10 and the photoelectric conversion circuit 10'.
此外，某些實施例中，該光電轉換電路10另包含一第三閘極106、一第四閘極107及一第五閘極108。該第三閘極106耦接至該節點N並用以對該像素電容102充電或放電到一預設電量，故該第三閘極106可稱為一重設電晶體(reset transistor)。該第四閘極107耦接在該光電元件101及該像素電容102之間並用以控制該光電元件101所轉換之該光電流輸出至該像素電容102以在該像素電容102暫存該第一電荷量Q1或該第二電荷量Q2。該第五閘極108耦接該光電元件101之輸出端並用以在非曝光期間(亦即快門關閉期間)釋放該光電元件101內累積的電荷。 In addition, in some embodiments, the photoelectric conversion circuit 10 further includes a third gate 106, a fourth gate 107, and a fifth gate 108. The third gate 106 is coupled to the node N and used to charge or discharge the pixel capacitor 102 to a predetermined amount of power. Therefore, the third gate 106 can be referred to as a reset transistor. The fourth gate 107 is coupled between the photo-electric component 101 and the pixel capacitor 102 and is configured to control the output of the photocurrent converted by the photo-electric component 101 to the pixel capacitor 102 to temporarily store the first capacitor at the pixel capacitor 102. The amount of charge Q 1 or the amount of second charge Q 2 . The fifth gate 108 is coupled to the output of the photovoltaic element 101 and is used to release the charge accumulated in the photovoltaic element 101 during non-exposure (ie, during shutter closure).
請繼續參照第2圖，該輸出電路20包含一第一儲存電路201及一第二儲存電路202分別用以儲存轉移自該光電轉換電路10(或該光電轉換電路10')之該第一電荷量Q1及該第二電荷量Q2。某些實施例中，該第一儲存電路201及該第二儲存電路202分別包含一開關元件及一儲存電容，如第2圖該第一儲存電路201包含一開關元件201s及一儲存電容201c，該第二儲存電路202包含一開關元件202s及一儲存電容202c。當該轉移電路103之該第二閘極103b開啟時，該開關元件201s或該開關元件202s亦被開啟以從該像素電容102轉移該第一電荷量Q1至該第一儲存電路201之該儲存電容201c或轉移該第二電荷量Q2至該第二儲存電路202之該儲存電容202c。也就是說，該等開關元件201s、202s可用以控制該光電轉換電路10之該第一電荷量Q1及該第二電荷量Q2轉移至該等儲存電容201c、202c進行儲存。 Referring to FIG. 2, the output circuit 20 includes a first storage circuit 201 and a second storage circuit 202 for storing the first charge transferred from the photoelectric conversion circuit 10 (or the photoelectric conversion circuit 10'). The quantity Q 1 and the second amount of charge Q 2 . In some embodiments, the first storage circuit 201 and the second storage circuit 202 respectively include a switching element and a storage capacitor. As shown in FIG. 2, the first storage circuit 201 includes a switching element 201s and a storage capacitor 201c. The second storage circuit 202 includes a switching element 202s and a storage capacitor 202c. When the circuit 103 of the second transfer gate 103b is turned on, the switching element of the switching element 201s or 202s were also opened to transfer the first amount of charge Q 1 to the first storage circuit from the pixel of the capacitor 102201 The storage capacitor 201c transfers the second amount of charge Q 2 to the storage capacitor 202c of the second storage circuit 202. That is, the switching elements 201s, 202s can be used to control the first charge amount Q 1 and the second charge amount Q 2 of the photoelectric conversion circuit 10 to be transferred to the storage capacitors 201c, 202c for storage.
因此，在該光電轉換電路10之該轉移電路103相對該低準位信號期間從該像素電容102轉換該第一電荷量Q1至該第一儲存電路201之後，該光電轉換電路10儲存該第二電荷量Q2至該像素電容102。接著，該轉移電路103再轉移該第二電荷量Q2至該第二儲存電路202，如第2圖所示。 Therefore, after the transfer circuit 103 of the photoelectric conversion circuit 10 converts the first charge amount Q 1 from the pixel capacitor 102 to the first storage circuit 201 during the low-level signal, the photoelectric conversion circuit 10 stores the first The second charge amount Q 2 is to the pixel capacitor 102. Then, the transfer circuit 103 transfers the second charge amount Q 2 to the second storage circuit 202 as shown in FIG.
該輸出電路20另包含一差分單元205用以比較該第一儲存電路201中之該第一電荷量Q1及該第二儲存電路202中之該第二電荷量Q2以輸出該類比影像信號，其中該第一儲存電路201及該第二儲存電路202分別耦接該差分單元205之兩輸入端。該差分單元205例如可為一差動放大器(differential amplifier)。藉此，該輸出電路20可利用該差分單元205對該 第一儲存電路201中之該第一電荷量Q1及該第二儲存電路202中之該第二電荷量Q2進行類比差分以輸出該類比影像信號。更詳細的說，儲存在該儲存電容201c之該第一電荷量Q1及儲存在該儲存電容202c之該第二電荷量Q2分別在該差分單元205之該兩輸入端形成兩輸入電壓，例如對應該第一電荷量Q1之一第一電壓V1及對應該第二電荷量Q2之一第二電壓V2。接著，該差分單元205之一輸出電壓Vout可由習知差動放大器之公式求得，例如Vout=Ad×(V1-V2)+Ac×(V1+V2)÷2，其中Ad表示為差模增益(differential-mode gain)，Ac表示為共模增益(common-mode gain)。 The output circuit 20 further includes a difference unit 205 for comparing the first charge amount Q 1 in the first storage circuit 201 and the second charge amount Q 2 in the second storage circuit 202 to output the analog image signal. The first storage circuit 201 and the second storage circuit 202 are respectively coupled to the two input ends of the difference unit 205. The difference unit 205 can be, for example, a differential amplifier. Thereby, the output circuit 20 can use the difference unit 205 to analogically divide the first charge amount Q 1 in the first storage circuit 201 and the second charge amount Q 2 in the second storage circuit 202 to output The analog image signal. In more detail, the amount of charge stored in the first storage capacitor Q 1 and 201c of the second amount of charge stored in the storage capacitor 202c Q 2 are formed of the two input voltages at the two input terminals of the differential unit 205, for example, charge amount Q corresponding to the first one of the first voltage V 1 is 1 and 2 corresponding to the second one of the charge amount Q 2 of the second voltage V. Then, the output voltage Vout of one of the difference units 205 can be obtained by a formula of a conventional differential amplifier, for example, Vout=Ad×(V 1 -V 2 )+Ac×(V 1 +V 2 )÷2, where Ad represents For differential-mode gain, Ac is expressed as common-mode gain.
可以瞭解的是，該輸出電路20之一輸出端可耦接至一類比數位轉換器(未繪示)，以轉換該類比影像信號為一數位影像信號以供一數位信號處理器(digital signal processor)進行數位影像處理，但本發明不限於此。其他實施例中，該輸出電路20之該輸出端可耦接至一邏輯電路(例如用以調整影像亮度、旋轉影像、裁剪影像、去除紅眼…等功能)或一記憶單元(例如用以儲存為一影像資料)，端視實際應用而定。 It can be understood that an output end of the output circuit 20 can be coupled to an analog-to-digital converter (not shown) for converting the analog image signal into a digital image signal for a digital signal processor. The digital image processing is performed, but the present invention is not limited thereto. In other embodiments, the output end of the output circuit 20 can be coupled to a logic circuit (eg, to adjust image brightness, rotate an image, crop a silhouette image, remove red eye, etc.) or a memory unit (eg, for storage as An image data) depends on the actual application.
由於該第一電荷量Q1係相對該高準位信號期間(該光源開啟故該入射光Li包含該光源所發出之光及該環境光)被儲存且該第二電荷量Q2係相對該低準位信號期間(該光源關閉故該入射光Li僅包含該環境光)被儲存，在該輸出電路20之該差分單元205比較該第一電荷量Q1及該第二電荷量Q2之後，該影像感測器1所輸出之該類比影像信號已去除環境光的干擾(該數位影像信號亦同)。因此，在該類比影像信號轉換成該數位影像信號之後，在數位端(例如包含該數位信號處理器)可直接處理該數位影像信號並據以產生一張數位影像圖框，並不需要對兩張數位影像圖框進行差分處理。 The first charge amount Q 1 is stored relative to the high level signal period (the light source is turned on, the incident light Li includes the light emitted by the light source and the ambient light), and the second charge amount Q 2 is relative to the During the low-level signal period (the light source is turned off, the incident light Li only contains the ambient light) is stored, after the difference unit 205 of the output circuit 20 compares the first charge amount Q 1 and the second charge amount Q 2 The analog image signal output by the image sensor 1 has removed the interference of ambient light (the digital image signal is also the same). Therefore, after the analog image signal is converted into the digital image signal, the digital image signal can be directly processed at the digit end (for example, including the digital signal processor), and a digital image frame is generated accordingly, and the two images are not required. The digital image frame is differentially processed.
此外，一自動曝光(auto exposure)機制係考量入射光的強弱以相應地調整曝光時間，例如當該入射光Li較強時，該影像感測器1可減少曝光時間(或調整光圈大小、白平衡…等)以避免所輸出之影像過曝。某些實施例中，為了實現該自動曝光機制，該影像感測器1之該第一儲存電路201另包含一比較器201a用以比較該儲存電容201c之電壓(亦即該第一電壓V1)與一參考電壓Vref以判斷是否施行該自動曝光機制，如第2圖所示。例如，當該參考電壓Vref大於該第一電壓V1時，該比較器201a輸出 一數值為0而包含該影像感測器1之該成像系統不調整該影像感測器1之曝光時間；當該參考電壓Vref等於或小於該第一電壓V1時，該比較器201a則輸出一數值為1以致於該成像系統可減少該影像感測器1之曝光時間。 In addition, an auto exposure mechanism considers the intensity of the incident light to adjust the exposure time accordingly. For example, when the incident light Li is strong, the image sensor 1 can reduce the exposure time (or adjust the aperture size, white). Balance...etc.) to avoid overexposure of the output image. In some embodiments, in order to implement the automatic exposure mechanism, the first storage circuit 201 of the image sensor 1 further includes a comparator 201a for comparing the voltage of the storage capacitor 201c (that is, the first voltage V 1 And a reference voltage Vref to determine whether to perform the automatic exposure mechanism, as shown in FIG. For example, when the reference voltage Vref is greater than the first voltage V 1, the output of the comparator 201a is 0 and a value comprising the image sensor of the imaging system of the image sensor 1 without adjusting the exposure time 1; when the reference voltage Vref is equal to or smaller than the first voltage V 1 is, the output of the comparator 201a is a value of 1 so that the imaging system may reduce the exposure of the image sensor 1 time.
第3圖為本發明某些實施例之影像感測器之運作方法之流程圖，該影像感測器包含一光電元件、一像素緩衝電路、一第一儲存電路、一第二儲存電路及一差分單元。該第一儲存電路及該第二儲存電路分別耦接於該差分單元之兩輸入端。該光電元件用以相對一高準位信號及一低準位信號產生光電流儲存至該像素緩衝電路，其中該高準位信號及該低準位信號用以驅動一光源之啟閉。該運作方法包含：於該高準位信號期間從該光電元件儲存一第一電荷量至該像素緩衝電路(步驟S1)；於該低準位信號期間將該像素緩衝電路之該第一電荷量轉移至該第一儲存電路(步驟S2)；該第一電荷量轉移後，於該低準位信號期間從該光電元件儲存一第二電荷量至該像素緩衝電路(步驟S3)；將該像素緩衝電路之該第二電荷量轉移至該第二儲存電路(步驟S4)；以及以該差分單元比較該第一儲存電路及該第二儲存電路中之儲存電荷量以輸出一類比影像信號(步驟S5)。 FIG. 3 is a flowchart of a method for operating an image sensor according to some embodiments of the present invention. The image sensor includes a photoelectric element, a pixel buffer circuit, a first storage circuit, a second storage circuit, and a Differential unit. The first storage circuit and the second storage circuit are respectively coupled to the two input ends of the differential unit. The photo-electric component is configured to generate a photocurrent to the pixel buffer circuit with respect to a high-level signal and a low-level signal, wherein the high-level signal and the low-level signal are used to drive a light source to be turned on and off. The operating method includes: storing a first amount of charge from the photo-electric component to the pixel buffer circuit during the high-level signal (step S1); and the first charge amount of the pixel buffer circuit during the low-level signal Transferring to the first storage circuit (step S2); after the first charge amount is transferred, storing a second amount of charge from the photo-electric component to the pixel buffer circuit during the low-level signal (step S3); Transferring the second amount of charge of the buffer circuit to the second storage circuit (step S4); and comparing the stored charge amount in the first storage circuit and the second storage circuit with the difference unit to output an analog image signal (step S5).
一實施例中，第3圖之影像感測器之運作方法可對應至第2圖之該影像感測器1，其中，該光電元件可為該光電轉換電路10(或該光電轉換電路10')之該光電元件101，該像素緩衝電路可包含該像素電容102及該轉移電路103。請同時參照第2~4圖，其中第4圖為對應第2及3圖之複數開關元件之時序圖，接著將說明所述影像感測器之運作方法。 In one embodiment, the method of operating the image sensor of FIG. 3 can correspond to the image sensor 1 of FIG. 2, wherein the photoelectric element can be the photoelectric conversion circuit 10 (or the photoelectric conversion circuit 10' The photo-electric component 101, the pixel buffer circuit can include the pixel capacitor 102 and the transfer circuit 103. Please refer to FIG. 2 to FIG. 4 at the same time, wherein FIG. 4 is a timing chart corresponding to the plurality of switching elements of FIGS. 2 and 3, and then the operation method of the image sensor will be described.
步驟S1：首先，在該高準位信號期間(例如以一驅動電路驅動一光源開啟)，關閉該第五閘極108一預設時間以致於該光電元件101所產生之一光電流不會經過該第五閘極108而被釋放，因此關閉該第五閘極108的期間(亦即該預設時間)可定義為該光電元件101之一有效曝光期間。接著，開啟該第三閘極106以對該像素電容102充電或放電到一預設電量。在該像素電容102具有該預設電量時，關閉該第三閘極106並開啟該第四閘極107，該光電元件101可於該高準位信號期間儲存該第一電荷量Q1至該像素緩衝電路(例如該像素電容102)。 Step S1: First, during the high-level signal (for example, driving a light source to be turned on by a driving circuit), the fifth gate 108 is turned off for a predetermined time so that one photocurrent generated by the photoelectric element 101 does not pass. The fifth gate 108 is released, so that the period in which the fifth gate 108 is turned off (i.e., the predetermined time) can be defined as one of the effective exposure periods of the photovoltaic element 101. Then, the third gate 106 is turned on to charge or discharge the pixel capacitor 102 to a predetermined amount of power. When the pixel capacitor 102 has the predetermined power, the third gate 106 is turned off and the fourth gate 107 is turned on, and the photoelectric element 101 can store the first charge amount Q 1 to the high level signal. A pixel buffer circuit (eg, the pixel capacitor 102).
相同地，該光電轉換電路10'之該光電元件101在該高準位信號期間亦儲存該第一電荷量Q1至該光電轉換電路10'之該像素電容102。 必須說明的是，該光電轉換電路10所儲存之該第一電荷量Q1及該光電轉換電路10'所儲存之該第一電荷量Q1僅用以表示相對該高準位信號期間所儲存的電荷。由於該光電轉換電路10及該光電轉換電路10'設置在該影像感測器1之不同位置，該光電轉換電路10與該光電轉換電路10'所接收的光能量不一定相同，故該光電轉換電路10之該第一電荷量Q1與該光電轉換電路10'之該第一電荷量Q1不一定具有相同的電荷量。 Similarly, the photo-electric component 101 of the photoelectric conversion circuit 10 ′ also stores the first charge amount Q 1 to the pixel capacitance 102 of the photoelectric conversion circuit 10 ′ during the high-level signal. It must be noted that the amount of the first charge Q 1 and stored in the photoelectric conversion circuit of the photoelectric conversion circuit 1010 'of the first stored charge amount Q 1 only to represent the relative duration of this high level signal stored The charge. Since the photoelectric conversion circuit 10 and the photoelectric conversion circuit 10' are disposed at different positions of the image sensor 1, the photoelectric energy of the photoelectric conversion circuit 10 and the photoelectric conversion circuit 10' are not necessarily the same, so the photoelectric conversion the first circuit 10 of the charge amount Q 1 of the charge amount of the first photoelectric converting circuit 10 'of Q 1 does not necessarily have the same amount of charge.
必須說明的是，該光電元件101係全時轉換入射光為光電流，故該第五閘極108的關閉時間(亦即該預設時間)可視為該影像感測器1的曝光時間，但本發明不限於此。其他實施例中，包含該影像感測器1之該成像系統可發出一快門信號控制該光電元件101開始或停止產生光電流，此時該影像感測器1可以不設置有該第五閘極108。 It should be noted that the photoelectric element 101 converts the incident light into a photocurrent at all times, so the off time of the fifth gate 108 (that is, the preset time) can be regarded as the exposure time of the image sensor 1 , but The invention is not limited thereto. In other embodiments, the imaging system including the image sensor 1 can emit a shutter signal to control the photoelectric element 101 to start or stop generating photocurrent. At this time, the image sensor 1 may not be provided with the fifth gate. 108.
步驟S2：接著，在該低準位信號期間(例如以該驅動電路驅動該光源關閉或不驅動該光源點亮)，關閉該光電轉換電路10之該第五閘極108以致於該光電元件101所產生之一光電流不會經過該第五閘極108而被釋放。該低準位信號期間與該高準位信號期間不同之處在於，在該低準位信號期間開啟該第三閘極106以重設該像素電容102之前，須同時開啟該第二閘極103b及該第一儲存電路201之該第一開關201s以將該像素電容102之該第一電荷量Q1轉移至該第一儲存電路201之該儲存電容201c。 Step S2: Next, during the low-level signal (for example, driving the light source to turn off or not driving the light source to be turned on), the fifth gate 108 of the photoelectric conversion circuit 10 is turned off so that the photovoltaic element 101 One of the generated photocurrents is not released through the fifth gate 108. The low-level signal period is different from the high-level signal period in that the second gate 103b is simultaneously turned on before the third gate 106 is turned on to reset the pixel capacitor 102 during the low-level signal. The first switch 201s of the first storage circuit 201 transfers the first charge amount Q 1 of the pixel capacitor 102 to the storage capacitor 201c of the first storage circuit 201.
如前所述，某些實施例中，在該第一電荷量Q1轉移之後(亦即步驟S2之後)，該第一儲存電路201所包含之該比較器201a比較該儲存電容之電壓與該參考電壓Vref以判斷是否施行自動曝光機制。 As described above, in some embodiments, after the first charge amount Q 1 is transferred (that is, after step S2), the comparator 201a included in the first storage circuit 201 compares the voltage of the storage capacitor with the The reference voltage Vref is used to determine whether or not to perform an automatic exposure mechanism.
步驟S3：在該第一電荷量Q1從該像素電容102轉移至該第一儲存電路201之後，關閉該第二閘極103b及該第一開關201s並開啟該第三閘極106以對該像素電容102充電或放電到該預設電量。在該像素電容102具有該預設電量時，關閉該第三閘極106並開啟該第四閘極107，該光電元件101即可儲存該第二電荷量Q2至該像素緩衝電路(例如該像素電容102)。 Step S3: After the first charge amount Q 1 is transferred from the pixel capacitor 102 to the first storage circuit 201, the second gate 103b and the first switch 201s are turned off and the third gate 106 is turned on to The pixel capacitor 102 is charged or discharged to the preset amount of power. When the pixel capacitor 102 has the predetermined power, the third gate 106 is turned off and the fourth gate 107 is turned on, and the photo-electric component 101 can store the second charge amount Q 2 to the pixel buffer circuit (for example, Pixel capacitance 102).
步驟S4：在該第二電荷量Q2儲存至該像素電容102之後，同時開啟該第二閘極103b及該第二開關202s以將該光電轉換電路10中該像素電容102之該第二電荷量Q2轉移至該第二儲存電路202。可以瞭解的 是，該影像感測器1透過該轉移電路103從該像素緩衝電路轉移該第一電荷量Q1至該第一儲存電路201並轉移該第二電荷量Q2至該第二儲存電路202。此時，該第一儲存電路201之該儲存電容201c及該第二儲存電路202之該儲存電容202c分別儲存有該第一電荷量Q1及該第二電荷量Q2，並於該差分單元205之該兩輸入端形成該第一電壓V1及該第二電壓V2。 Step S4: After the second charge amount Q 2 is stored in the pixel capacitor 102, the second gate 103b and the second switch 202s are simultaneously turned on to the second charge of the pixel capacitor 102 in the photoelectric conversion circuit 10. The quantity Q 2 is transferred to the second storage circuit 202. It can be understood that the image sensor 1 transfers the first charge amount Q 1 from the pixel buffer circuit to the first storage circuit 201 through the transfer circuit 103 and transfers the second charge amount Q 2 to the second storage. Circuit 202. At this time, the storage capacitor 201c of the first storage circuit 201 and the storage capacitor 202c of the second storage circuit 202 respectively store the first charge amount Q 1 and the second charge amount Q 2 , and the difference unit The two inputs of 205 form the first voltage V 1 and the second voltage V 2 .
步驟S5：最後，以該差分單元205比較該第一儲存電路201之該第一電壓V1及該第二儲存電路202之該第二電壓V2以輸出一類比影像信號。藉此，可在該類比影像信號透過一類比數位轉換器轉換成一數位影像信號之前消除環境光的干擾。 Step S5: Finally, the circuit 205 compares the first storage unit 201 of the differential voltage V 1 is the first and the second storage circuit 202 of the second voltage V 2 to output an analog image signal. Thereby, ambient light interference can be eliminated before the analog image signal is converted into a digital image signal by an analog converter.
某些實施例中，該第一儲存電路201儲存該第一電荷量Q1與該第二儲存電路202儲存該第二電荷量Q2間之一間隔時間須愈短愈好，以防止儲存在該儲存電容201c之該第一電荷量Q1在該儲存電容202c儲存該第二電荷量Q2之前衰減以致於該差分單元205可準確根據該第一電壓V1及該第二電壓V2輸出該類比影像信號，例如該間隔時間可小於或等於該第五閘極108的關閉時間(亦即該預設時間或該高準位信號期間)。 In some embodiments, the first storage circuit 201 stores the first charge amount Q 1 and the second storage circuit 202 stores the second charge amount Q 2 in a shorter interval, so as to prevent storage. The first charge amount Q 1 of the storage capacitor 201c is attenuated before the storage capacitor 202c stores the second charge amount Q 2 so that the difference unit 205 can accurately output according to the first voltage V 1 and the second voltage V 2 . The analog image signal, for example, the interval time may be less than or equal to the off time of the fifth gate 108 (ie, the preset time or the high level signal period).
必須說明的是，由於該光電轉換電路10及該光電轉換電路10'耦接至相同的輸出電路(亦即該輸出電路20)，當該光電轉換電路10轉移該第一電荷量Q1或該第二電荷量Q2至該輸出電路20時，該光電轉換電路10'並不能同時轉移該第一電荷量Q1或該第二電荷量Q2至該輸出電路20。因此，該影像感測器1係依序開啟該光電轉換電路10之該第二閘極103b及該第一開關201s、該光電轉換電路10之該第二閘極103b及該第二開關202s、該光電轉換電路10'之該第二閘極103b及該第一開關201s以及該光電轉換電路10'之該第二閘極103b及該第二開關202s，以致於該光電轉換電路10之該第一電荷量Q1及該第二電荷量Q2與該光電轉換電路10'之該第一電荷量Q1及該第二電荷量Q2可依序被轉移，如第4圖所示。 It should be noted that, since the photoelectric conversion circuit 10 and the photoelectric conversion circuit 10' are coupled to the same output circuit (that is, the output circuit 20), when the photoelectric conversion circuit 10 transfers the first charge amount Q 1 or the When the second charge amount Q 2 is to the output circuit 20, the photoelectric conversion circuit 10' cannot simultaneously transfer the first charge amount Q 1 or the second charge amount Q 2 to the output circuit 20. Therefore, the image sensor 1 sequentially turns on the second gate 103b of the photoelectric conversion circuit 10, the first switch 201s, the second gate 103b of the photoelectric conversion circuit 10, and the second switch 202s, The second gate 103b of the photoelectric conversion circuit 10' and the first switch 201s and the second gate 103b of the photoelectric conversion circuit 10' and the second switch 202s, so that the photoelectric conversion circuit 10 a charge amount Q 1 and Q 2 of the second charge amount to the charge amount of the first photoelectric converting circuit 10 'of Q 1 and Q 2 of the second amount of charge can sequentially be transferred, as shown in FIG. 4.
可以瞭解的是，該光電轉換電路10'相對該高準位信號期間(亦即該第五閘極108第一次關閉的期間)所儲存之該第一電荷量Q1在該第五閘極108第二次關閉的期間才轉移至該輸出電路20，因此，在該光電轉換電路10轉移該第二電荷量Q2至該輸出電路20之前，該光電轉換電路10'之該第二閘極103b皆保持關閉的狀態。某些實施例中，在該高準位信號 期間一控制信號(例如由該影像感測器1或該成像系統所發出)控制該光電轉換電路10及該光電轉換電路10'之該第五閘極108同時關閉，接著在該低準位信號期間，該控制信號依序關閉該光電轉換電路10之該第五閘極108及該光電轉換電路10'之該第五閘極108。如前所述，關閉該第五閘極108的期間可定義為該光電元件101之該有效曝光期間；換句話說，該影像感測器1在該高準位信號期間同時曝光該光電轉換電路10及該光電轉換電路10'，接著在該低準位信號期間依序曝光該光電轉換電路10及該光電轉換電路10'。 It can be understood that the first charge amount Q 1 stored by the photoelectric conversion circuit 10 ′ during the high-level signal period (that is, the period during which the fifth gate 108 is first turned off) is at the fifth gate. 108 is transferred to the output circuit 20 during the second shutdown period. Therefore, before the photoelectric conversion circuit 10 transfers the second charge amount Q 2 to the output circuit 20, the second gate of the photoelectric conversion circuit 10' 103b is kept closed. In some embodiments, a control signal (eg, issued by the image sensor 1 or the imaging system) controls the fifth switch of the photoelectric conversion circuit 10 and the photoelectric conversion circuit 10' during the high-level signal The poles 108 are simultaneously turned off, and then during the low level signal, the control signal sequentially turns off the fifth gate 108 of the photoelectric conversion circuit 10 and the fifth gate 108 of the photoelectric conversion circuit 10'. As described above, the period in which the fifth gate 108 is turned off may be defined as the effective exposure period of the photovoltaic element 101; in other words, the image sensor 1 simultaneously exposes the photoelectric conversion circuit during the high-level signal. 10 and the photoelectric conversion circuit 10', and then sequentially exposing the photoelectric conversion circuit 10 and the photoelectric conversion circuit 10' during the low-level signal.
第5圖為本發明某些實施例之影像感測器3之方塊圖。該影像感測器3包含一驅動電路30、一光電轉換電路31、一第一儲存電路321、一第二儲存電路322及一差分單元325，其中該驅動電路30與該光電轉換電路31電性連接、該第一儲存電路321及該第二儲存電路322之輸入端同時耦接至該光電轉換電路31之輸出端以及該差分單元325包含兩輸入端分別耦接該第一儲存電路321及該第二儲存電路322。 Figure 5 is a block diagram of an image sensor 3 in accordance with some embodiments of the present invention. The image sensor 3 includes a driving circuit 30, a photoelectric conversion circuit 31, a first storage circuit 321, a second storage circuit 322, and a difference unit 325. The driving circuit 30 and the photoelectric conversion circuit 31 are electrically connected. The input end of the first storage circuit 321 and the second storage circuit 322 are coupled to the output end of the photoelectric conversion circuit 31, and the differential unit 325 includes two input ends respectively coupled to the first storage circuit 321 and the The second storage circuit 322.
該驅動電路30例如可為一信號產生器或一時序控制器，用以依序產生一高準位信號SH及一低準位信號SL，其中該高準位信號SH及該低準位信號SL分別用以控制一光源5於一第一期間開啟且於一第二期間關閉。此外，該驅動電路30同時產生至少一控制信號Sc以控制該光電轉換電路31、該第一儲存電路321及該第二儲存電路322中複數開關元件之啟閉，例如可控制第2及4圖中該第二閘極103b、該第三閘極106、該第四閘極107、該第五閘極108、該第一開關201s及該第二開關202s之啟閉。其他實施例中，包含該影像感測器3之一成像系統另提供一控制電路控制該光源5之啟閉，且該光源5之控制信號被傳送至該影像感測器3之該驅動電路30，以使該驅動電路30相應控制該等開關元件。 The driving circuit 30 can be, for example, a signal generator or a timing controller for sequentially generating a high level signal S H and a low level signal S L , wherein the high level signal SH and the low level The bit signals S L are respectively used to control a light source 5 to be turned on during a first period and turned off in a second period. In addition, the driving circuit 30 simultaneously generates at least one control signal Sc to control the opening and closing of the plurality of switching elements in the photoelectric conversion circuit 31, the first storage circuit 321 and the second storage circuit 322, for example, the second and fourth figures can be controlled. The second gate 103b, the third gate 106, the fourth gate 107, the fifth gate 108, the first switch 201s and the second switch 202s are opened and closed. In another embodiment, an imaging system including the image sensor 3 further provides a control circuit for controlling the opening and closing of the light source 5, and the control signal of the light source 5 is transmitted to the driving circuit 30 of the image sensor 3. So that the drive circuit 30 controls the switching elements accordingly.
當該光源5於該第一期間開啟時，該光電轉換電路31同時接收該光源5之一光源強度I5及一環境光強度IAB；當該光源5於該第二期間關閉時，該光電轉換電路31則僅接收該環境光強度IAB。據此，該光電轉換電路31於該第一期間可產生對應該光源5及環境光之光電流且於該第二期間產生對應該環境光之光電流。必須說明的是，所述光源強度I5是來自被偵測物件之反射光，亦即本實施例中該光源5係用以照明被偵測物件。 When the light source 5 is turned on during the first period, the photoelectric conversion circuit 31 simultaneously receives a light source intensity I 5 and an ambient light intensity I AB of the light source 5; when the light source 5 is turned off during the second period, the photoelectric The conversion circuit 31 then receives only the ambient light intensity I AB . Accordingly, the photoelectric conversion circuit 31 generates a photocurrent corresponding to the light source 5 and the ambient light during the first period and generates a photocurrent corresponding to the ambient light during the second period. It should be noted that the light source intensity I 5 is the reflected light from the detected object, that is, the light source 5 is used to illuminate the detected object in this embodiment.
接著，該第一儲存電路321於該第二期間儲存對應該第一期間之該光電流之一第一電荷量；在該第一電荷量被儲存之後，該第二儲存電路322儲存對應該第二期間之該光電流之一第二電荷量。可以瞭解的是，該第一電荷量係關聯該光源強度I5及該環境光強度IAB，該第二電荷量僅關聯該環境光強度IAB。 Then, the first storage circuit 321 stores a first charge amount corresponding to the photo current in the first period during the second period; after the first charge amount is stored, the second storage circuit 322 stores the corresponding The second amount of charge of the photocurrent during the second period. It can be understood that the first charge amount is associated with the light source intensity I 5 and the ambient light intensity I AB , and the second charge amount is only associated with the ambient light intensity I AB .
最後，該差分單元325比較該第一儲存電路321及該第二儲存電路322中之儲存電荷量(例如第2圖之該第一電荷量Q1及該第二電荷量Q2)以消除該環境光之干擾，並輸出一類比影像信號Sa。某些實施例中，該差分單元325對該第一儲存電路321及該第二儲存電路322中之儲存電荷量直接進行類比差分並輸出該類比影像信號Sa。 Finally, the difference unit 325 compares the stored charge amount in the first storage circuit 321 and the second storage circuit 322 (for example, the first charge amount Q 1 and the second charge amount Q 2 in FIG. 2 ) to eliminate the Ambient light interference, and output a kind of analog image signal Sa. In some embodiments, the difference unit 325 directly compares the stored charge amounts in the first storage circuit 321 and the second storage circuit 322 and outputs the analog image signal Sa.
相同地，某些實施例中，為了實現自動曝光機制，該第一儲存電路321可另包含一比較器321a用以比較該第一儲存電路321中一儲存電容之電壓與一參考電壓以判斷是否施行一自動曝光機制。必須說明的是，雖然第5圖繪示該比較器321a耦接在該第一儲存電路321與該差分單元325之間，只要能夠耦接至該第一儲存電路321中該儲存電容之電壓即可，其連接位置並無特定限制。 Similarly, in some embodiments, in order to implement the automatic exposure mechanism, the first storage circuit 321 may further include a comparator 321a for comparing the voltage of a storage capacitor in the first storage circuit 321 with a reference voltage to determine whether An automatic exposure mechanism is implemented. It should be noted that although the comparator 321a is coupled between the first storage circuit 321 and the difference unit 325, the voltage of the storage capacitor can be coupled to the first storage circuit 321 Yes, there is no specific limit to the connection position.
如前所述，本發明某些實施例之影像感測器具有複數陣列排列的光電轉換電路以作為感測像素。請參照第6及7圖，其中第6圖為本發明某些實施例包含複數光電轉換電路之一成像系統4之示意圖，第7圖為對應第6圖之時序圖。該成像系統4包含一光源5、一驅動電路30(或一控制電路)、以6×8陣列排列的複數光電轉換電路31、一輸出電路32、一類比數位轉換器35、一處理器37，其中第一列之該等光電轉換電路31可定義為感測像素列R1、第二列之該等光電轉換電路31可定義為感測像素列R2…依此類推。 As previously mentioned, the image sensor of some embodiments of the present invention has a plurality of arrays of photoelectric conversion circuits as sensing pixels. Please refer to FIGS. 6 and 7, wherein FIG. 6 is a schematic diagram of an imaging system 4 including a plurality of photoelectric conversion circuits according to some embodiments of the present invention, and FIG. 7 is a timing chart corresponding to FIG. The imaging system 4 includes a light source 5, a driving circuit 30 (or a control circuit), a plurality of photoelectric conversion circuits 31 arranged in a 6×8 array, an output circuit 32, an analog-to-digital converter 35, and a processor 37. The photoelectric conversion circuits 31 of the first column may be defined as the sensing pixel columns R1, the second columns, and the like, and the photoelectric conversion circuits 31 may be defined as the sensing pixel columns R2, and so on.
當該驅動電路30在一第一期間P1控制該光源5開啟時，該驅動電路30同時控制全部之該光電轉換電路31同時曝光以儲存複數第一電荷量。 When the driving circuit 30 controls the light source 5 to be turned on during a first period P1, the driving circuit 30 simultaneously controls all of the photoelectric conversion circuits 31 to simultaneously expose to store a plurality of first charges.
當該驅動電路30在一第二期間P2控制該光源5關閉時，該驅動電路30先控制第一列之該等光電轉換電路31(亦即該感測像素列R1)轉移該等第一電荷量至該輸出電路32、再次曝光以儲存複數第二電荷 量以及轉移該等第二電荷量至該輸出電路32以致於該輸出電路32可比較每一該第一電荷量及每一該第二電荷量以輸出對應第一列之一類比影像信號Sa。接著，該驅動電路30依序控制第二列至第六列之該等光電轉移電路31以輸出對應第二列至第六列之該類比影像信號Sa，如第7圖所示。 When the driving circuit 30 controls the light source 5 to be turned off during a second period P2, the driving circuit 30 first controls the photoelectric conversion circuits 31 of the first column (that is, the sensing pixel column R1) to transfer the first charges. Measured to the output circuit 32, again exposed to store a plurality of second charges And outputting the second amount of charge to the output circuit 32 such that the output circuit 32 can compare each of the first amount of charge and each of the second amounts of charge to output an analog image signal Sa corresponding to the first column. Next, the driving circuit 30 sequentially controls the photoelectric conversion circuits 31 of the second to sixth columns to output the analog image signals Sa corresponding to the second to sixth columns, as shown in FIG.
某些實施例中，該成像系統4可在該類比數位轉換器之一輸入端設置一放大器用以放大該等類比影像信號Sa。最後，透過該類比數位轉換器35，該處理器37可根據對應該等感測像素(亦即該等光電轉換電路31)之數位影像信號Sd輸出一影像。可以瞭解的是，該成像系統4所輸出之影像已消除環境光之干擾，可直接進行影像處理。 In some embodiments, the imaging system 4 can provide an amplifier at one of the inputs of the analog to digital converter to amplify the analog image signals Sa. Finally, through the analog-to-digital converter 35, the processor 37 can output an image according to the digital image signal Sd corresponding to the sensing pixels (that is, the photoelectric conversion circuits 31). It can be understood that the image output by the imaging system 4 has eliminated the interference of ambient light and can directly perform image processing.
某些實施例中，該第一儲存電路及該第二儲存電路分別包含一開關元件及一儲存電容，該開關元件用以控制該光電轉換電路之該第一電荷量及該第二電荷量轉移至該儲存電容。 In some embodiments, the first storage circuit and the second storage circuit respectively comprise a switching component and a storage capacitor, wherein the switching component is configured to control the first charge amount and the second charge amount transfer of the photoelectric conversion circuit To the storage capacitor.
某些實施例中，該第一儲存電路另包含一比較器用以比較該儲存電容之電壓與一參考電壓以判斷是否施行一自動曝光機制。 In some embodiments, the first storage circuit further includes a comparator for comparing the voltage of the storage capacitor with a reference voltage to determine whether to perform an automatic exposure mechanism.
某些實施例中該影像感測器另包含一驅動電路用以依序產生該高準位信號及該低準位信號。 In some embodiments, the image sensor further includes a driving circuit for sequentially generating the high level signal and the low level signal.
本發明實施例之影像感測器可在藉由時序控制以直接比較關聯一光源及環境光之一第一電荷量及僅關聯該環境光之一第二電荷量，而非對該第一電荷量及該第二電荷量分別形成之數位影像圖框進行差分運算，藉以在不降低功率消耗的同時消除該環境光的干擾。 The image sensor of the embodiment of the present invention can directly compare the first charge amount associated with a light source and ambient light and only the second charge amount of the ambient light by timing control instead of the first charge. The digital image frame formed by the quantity and the second charge amount is separately subjected to a difference operation, thereby eliminating interference of the ambient light without reducing power consumption.
如上所述，習知影像感測器使用兩張數位影像圖框(一張對應一光源及環境光、另一張僅對應該環境光)以進行差分運算以消除環境光的干擾，因而具有較高的功率消耗。因此，本發明提出一種影像感測器(第2、3圖)及其運作方法(第3、7圖)，其可藉由時序控制以直接比較關聯該光源及該環境光之一第一電荷量及僅關聯該環境光之一第二電荷量，以在不降低功率消耗的同時消除環境光的干擾。 As described above, the conventional image sensor uses two digital image frames (one corresponding to one light source and ambient light, and the other corresponds to ambient light) to perform differential operations to eliminate ambient light interference, thereby High power consumption. Therefore, the present invention provides an image sensor (Figs. 2 and 3) and a method of operating the same (Figs. 3 and 7), which can be directly compared to associate the light source with a first charge of the ambient light by timing control. A quantity and a second amount of charge associated with only one of the ambient lights to eliminate ambient light interference without reducing power consumption.
雖然本發明已以前述實施例揭示，然其並非用以限定本發明，任何本發明所屬技術領域中具有通常知識者，在不脫離本發明之精神和範圍內，當可作各種之更動與修改。因此本發明之保護範圍當視後附之申請專利範圍所界定者為準。 The present invention has been disclosed in the foregoing embodiments, and is not intended to limit the present invention. Any of the ordinary skill in the art to which the invention pertains can be modified and modified without departing from the spirit and scope of the invention. . Therefore, the scope of the invention is defined by the scope of the appended claims.
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