201246928 六、發明說明： 【發明所屬之技術領域】 本發明係有關於-種黑階補償電路及其相關方法，尤指一種同 時利用數位及輯影像_峨進行黑階補伽黑階補償 電路、影像感測器及其相關方法。 【先前技術】 半導體影像感測器(例如電荷耗合元件(CCD)或互補金屬氧化半 導體(CMOSM·)普遍使驗照械或攝雜巾，用以將可見光 之影像轉換為電子信號，便於後續的儲存、傳輸或顯示。 由於電子電路的非完美性質，使得影像感測器在未接收任何光 線的情形下仍齡具有漏電流，因此使得影賴·所產生的影像 感測ail號會包含有此漏電流的成分，而無法真實反應所感測到的影 像凴度值。為了克服此問題，通常會讀取多行的光學黑（optical black)像素(或光遮（light-shielded)像素），經平均後作為一黑階補 償值，此黑階補償值即用來表示影像感測器在未接收任何光線下仍 具有之漏電流。 請參考第1圖’第1圖為習知黑階補償電路100的示意圖。如 第1圖所示，黑階補償電路100包含有一加法器102、一類比放大 器104、一類比數位轉換器丨〇6、一數位放大器ι〇8、一黑階校正單 201246928 元110以及-數位類比轉換器112。在黑階補償電路 100的操作上， 黑階補償電路_會讀取影像感測訊號Vin中的黑像素感測訊號， 並藉由類比放大②104、類比數位轉換器1G6以及數位放大器⑽ 的處理後’輸人至黑階校正單元⑽中。而黑階校正單元110將所 接收的黑像诚測值進行平均計算，以得到—黑_償值，之後該 黑階補償值經由數位類比轉換器122回到加法請以補償影像感 測喊Vln，以使得影像處理單元120所接收到的影像感測訊號可 以真實反應出所感測到的影像亮度值。 ^ j而上述黑p白補仏電路100的類比數位轉換器⑽以及黑階 1單11G會具有較大的時間延遲’且數位類比轉換$ 112會產 生量化誤差’目此’傳統之黑_償電路1GG的速度及準確度都無 法提高。 、另外’若是利賴比f路來進行黑階補償，則會有無法有效率 進行熱像素遽除的問題，而無法準確的進行黑階補償。 【發明内容】 因此，本發明的目的之一在於提供一種同時利用數位及類比電 路以對衫像感測訊號進行黑階補償的黑階補償電路及其相關方法， 以解決上述的問題。 依據本發明一實施例，一種黑階補償電路包含有一第一處理單 201246928 元、一第二處理單元以及一補償單元。該第一處理單元依據—第— 臨界值以對所接收之一第一數位黑像素感測訊號進行熱像素據除操 作，以產生一濾除後第一黑像素感測訊號，並依據該濾除後第一黑 像素感測訊號以產生一第二臨界值；該第二處理單元依據該第二臨 界值以對所接收之一第二數位黑像素感測訊號進行熱像素濾除操 作’以產生一濾除後第二黑像素感測訊號，並依據該濾除後第二累 像素感測訊號以產生一黑階補償值；該補償單元依據該黑階補償值 以對所接收之影像感測訊號進行黑階補償以得到一輸出訊號。 依據本發明另一實施例，一種黑階補償方法，包含有：依據— 第一臨界值以對一第一數位黑像素感測訊號進行熱像素濾除操作， 以產生一濾除後第一黑像素感測訊號，並依據該濾除後第一黑像素 感測訊號以產生一第二臨界值；依據該第二臨界值以對一第二數位 黑像素感測訊號進行熱像素濾除操作，以產生一濾除後第二黑像素 感測訊號，並依據該濾除後第二黑像素感測訊號以產生一黑階補償 值；以及依據該黑階補償值以對所接收之影像感測訊號進行黑階補 償以得到一輸出訊號。 依據本發明另一實施例，一種影像感測器包含有一影像感測單 元以及一黑階補償電路，其中該影像感測單元包括複數個感測像素 及複數個黑像素。該黑階補償電路包含有一第一處理單元、—第二 處理單元以及一補償單元。該第一處理單元耦接至該些黑像素，用 以依據一第一臨界值以對所接收之該些黑像素的感測訊號進行熱像 201246928 -素濾除操作，以產生一濾除後第一黑像素感測訊號，並依據該濾除 後第一黑像素感測訊號以產生一第二臨界值；該第二處理單元耦接 至该些黑像素，用以依據該第二臨界值以對所接收之該些黑像素的 感測訊號進行熱像素濾除操作，以產生一濾除後第二黑像素感測訊 唬，並依據該濾除後第二黑像素感測訊號以產生一黑階補償值；該 補償單元耦接於該些感測像素，用來依據該黑階補償值以對該些感 測像素之影像感測訊號進行黑階補償以得到一輸出訊號。 【實施方式】 請參考第2圖，第2圖為依據本發明一實施例之黑階補償電路 200的示意圖。如第2圖所示，黑階補償電路2〇〇包含有一類比黑 階校正單元202、一類比數位轉換器208、一第一處理單元210、一 第一多工器220、一加法器222、一乘法器224、一第二處理單元230、 一第二多工器240以及一補償單元（於本實施例中，該補償單元為 一加法器250)，其中類比黑階校正單元202包含有一加法器203、 一類比放大器204以及一黑階值計算單元206。 在黑階補償電路2〇〇的操作上，首先，類比黑階校正單元2〇2 接收來自影像感測器（未繪示）的類比黑像素感測訊號Vin，並對 類比黑像素感測訊號Vin進行黑階調整操作以產生一調整後類比黑 像素感測訊號。詳細來說，類比黑像素感測訊號Vin經過加法器203 以及類比放大器204之後輸入至黑階值計算單元206，接著，黑階 值計算單元206將所接收的類比黑像素感測訊號Vi η作平均操作（例 201246928 如，低通濾波操作）以產生一校正值vBLC至加法器203，以使得類 比黑像素感測訊號Vin在經過加法器203之後會儘可能的接近一代 表全黑的灰階值。在其他實施例中，類比黑階校正單元2〇2可以使 用減法器或是混合器來代替加法器203。 然而，由於影像感測器在製作過程上的瑕疲，有少部分的累像 素會有所謂的“熱像素”現象，亦即在某些情形下，該些黑像素所輸 出的感測訊號會具有很大的電流/電壓。因此，黑階值計算單元2〇6 所汁算出的校正值VBLC至很可能會因為少部分的黑像素的“熱像 素”現象而有所誤差，進而造成類比黑階校正單元2〇2的輸出並不會 接近一代表全黑的灰階值，亦即，類比數位轉換器2〇8接收黑階校 正單7L 202之輸出以產生的數位黑像素感測訊號Din可能無法達到 一接近於“0”或一很低的數位值。 因此，接著，第一處理單元210接收數位黑像素感測訊號Din 中的第一數位黑像素感測訊號，並依據一第一臨界值TH1以對 該第一數位黑像素感測訊號進行熱像素濾除操作以產生一濾除後第 黑像素感測峨，其+第-触,魏素細城可以是包含有複 數，黑像素（例如-整行黑像素）的感麻號，且祕素遽除操作 P疋將該第一數位黑像素感測訊號中大於第一臨界值TH1的數位 值去除。接著’第-處理單元21〇、_將簡除後第—黑像素感測 孔號中複數個數位值作平均操作，以產生-第二臨界值TH2。 201246928 接著，第一多工器220依據一第一選擇訊號SEL1以選擇性地 輪出第一臨界值TH1或是第二臨界值TH2，之後，第一多工器220 的輸出經由加法器222以及乘法器224的調整之後輸入至第二處理 早元230。 需注意的是，加法器222以及乘法器224係用來對第一臨界值 ΤΗ 1或是第二臨界值TH2作數值上的調整，且均為非必須（〇pti〇nai) 的元件，亦即加法器222以及乘法器224可以自黑階補償電路2〇〇 移除而不影響到黑階補償電路2〇〇的操作。 接著，第二處理單元230接收數位黑像素感測訊號Din中的一 第二數位黑像素感測訊號，並依據第一多工器220所輸出的第一臨 界值TH1或是第二臨界值哪，以_第二數位黑像域測訊號進 行熱像素濾除操作以產生一濾除後第二黑像素感測訊號，其中第二 數位黑像素感測訊號可以是包含有複數個黑像素（例如另一整行黑 像素）的感測訊號，且熱像素濾除操作即是將該第二數位黑像素感 測訊號中大於第-臨界值TH1或是第二臨界值TH2的數位值去 除。接著’第二處理單元23〇繼續將該渡除後第二黑像素感測訊號 中複數個數健作平均操作，並據以產生—黑階補償值Dbk。 舉例說明上述第一處理單元21〇以及第二處理單元23〇的操 作’凊參考第3圖，假設第3圖所示之黑點為該第一數位黑像素感 測訊號的數值分佈圖，縱軸為數值大小。則第一臨界值thi可以設 9 201246928 定為-較高的數位值，例如“蕭，，以使得第一處理單元21G據除很 月顯的熱像素’值。而圖示之第二臨界值τΗ2可以是位於第一臨界 值TH1町之所有黑像錢測訊號的平均，於關巾假設為“55，，。 因此’假設該第二數位黑像素感測戰與該第—數位黑像素感測訊 號具有類似的數值分佈，則第二處理單^可以進—步遽除較不 明顯的“熱像素”值（亦即數值位於“Μ”以上的黑像素感測訊號），並 將圖不之第二臨界值TH2以下之所有黑像素感測訊號的作平岣計 算，並據以得到黑階補償值DBLC。 在決定黑階補償值dblc的步驟中，在一實施例中，可以將第二 臨界值TH2以下之所有黑像素感測訊號的平均值設為黑階補償值 Dblc的，亦即，若是第3圖所示之第二臨界值TH2以下的所有累 像素感測訊號的平均值為“40”，則將黑階補償值Dblc設為“4〇”以使 得黑階補償電路200的輸出訊號Dout消除黑像素漏電流的成分；在 另一實施例中，若是第3圖所示之第二臨界值TH2以下的所有黑 像素感測訊號的平均值為“40”，則可以依據此平均值，經由運算或 調整而設定黑階補償值DBLC，例如為“25”。 接著’第二多工器240依據一第二選擇訊號SEL2以選擇性地 輪出黑階補償值DBLC或是一第三臨界值TH3至加法器250，之後， 加法器250依據黑階補償值DBLC或是第三臨界值TH3以對所接收 之影像感測訊號進行黑階補償以得到一輸出訊號Dout至後端的影 像處理電路（未繪示）。 10 201246928 β④/主思的疋’第-多工器22〇的功能僅是供設計者/使用者選擇 疋否略過帛處理單元21Q的輸出，並直接讓第二多工器咖使用 第臨界值TH1來進行熱像素遽除操作。因此，若是不需要此選擇 功能’第一多工器220亦可以自黑階補償電路200中移除，且第一 處理單元210所輸出的第二臨界值TH2直接輸入至加法器從。 類似地$一夕工器24〇的功能是供設計者/使用者選擇是否略 過第二處理早几23G的輸出’並直接讓加法器25()使用第三臨界值 TH3以對所接收之影像感測峨進行黑_償。·，若是不需要 此選擇功能’第二多工器24G亦可以自黑階麵電路中移除， 且第二處理單元230所輸出的黑階補償值DBLC以直接輸入至加法器 250。 ° 如上所述，黑階補償電路2〇〇中的數位電路可以得到一理想的 黑階補償值DBLC，以使得對應至數位黑像素感測訊號咖的輸出訊 號Dout可以接近於“〇，，或為一很低的數位值。如此一來，黑階補償 電路200便可以對後續所接收的影像感測訊號進行準確地黑階補 償。 、、白 此外，由於黑階補償電路200先利用類比電路來進行第一階段 的黑階補償，之後再利用數位電路來消除“熱像素’，影響後來進行第 二階段的黑階補償，因此，可以避免習知技術中數位黑階補償電路 11 201246928 的速度及準確度問題，以及避免習知技術中類比黑階補償電路因為 熱像素因素而造成的準確性問題。 第4圖為依據本發明一實施例之影像感測器400的示意圖，如 第4圖所示，影像感測器4〇〇包含有一影像感測單元420以及黑階 補償電路460。影像感測單元420包括複數個感測像素及複數個黑 像素’且用來輸出該些黑像素的感測訊號以及該些感測像素之影像 感測訊號Vin至黑階補償電路460。在影像感測器400的操作上， 黑階補償電路460接收該些黑像素的感測訊號，並對該些黑像素的 感測訊號進行處理以產生一黑階補償值，接著，黑階補償電路460 再依據該黑階補償值以對該些感測像素之影像感測訊號進行黑階補 償以得到輸出訊號Dout。 黑階補償電路460包括類比數位轉換器408、第一處理單元 410、第二處理單元430以及補償單元（加法器）450。第一處理單 元410依據第一臨界值TH1以對所接收之黑像素的感測訊號進行熱 像素濾除操作，以產生濾除後第一黑像素感測訊號，並依據該濾除 後第一黑像素感測訊號以產生一第二臨界值TH2。第二處理單元 430耦接至該些黑像素，依據第二臨界值TH2以對所接收之黑像素 的感測訊號進行熱像素濾除操作，以產生濾除後第二黑像素感測訊 破，並依據;慮除後第一黑像素感測訊號以產生黑階補償值dblc。補 償單元450用來依據該黑階補償值Dblc以對感測像素之影像感測訊 號進行黑階補償以得到一輸出訊號Dout。其中，第一處理單元 12 201246928 -及第二處理單元430所接收的黑像素感測訊號可以是直接從影像感 測單元420而來的類比訊號或是，如本實施，例透過類比數位轉換 器408而來的數位訊號。 在一實施例中，第二臨界值TH2係小於第一臨界值TH1。其中 第一處理單元410將濾除後第一黑像素感測訊號作平均操作，並據 以產生第二臨界值TH2。本實施例黑階補償電路460亦可包括上述 其他實施例中的類比黑階校正單元202。 簡要歸納本發明，於本發明之黑階補償電路及相關方法中，係 =時利職位及敝電路崎影像感測訊號進行黑階補償的黑階補 償電路及其相關方法’其中黑階補償電路中的數位電路部份可以準 確消除熱像素所造朗影響，麵一步_接㈣影佩測訊號進 饤黑階補償，以得到-理想的輸出訊號。 所做實施例’凡依本發明申請專利範圍 〃 >飾白應屬本發明之涵蓋範圍。 【圖式簡單說明】 第1圖為習知黑階補償電路的示意圖。 :2==明，_電路的示意圖。 第4圖从』Γ 處理單元的操作示意圖。 圖為依據本發明—實施例之影像_器的示意圖。 13 201246928 【主要元件符號說明】 100、200、460 黑階補償電路 102、203、222、250、450 加法器 104 、 204 類比放大器 106、208、408 類比數位轉換器 108 數位放大器 110 黑階校正單元 112 數位類比轉換器 120 影像處理單元 202 類比黑階校正單元 206 黑階值計算單元 210 > 410 第一處理單元 220 第一多工器 224 乘法器 230、430 第二處理單元 240 第二多工器 400 影像感測器 420 影像感測單元 s 14201246928 VI. Description of the Invention: [Technical Field] The present invention relates to a black-order compensation circuit and related methods thereof, and more particularly to a black-order complementary gamma black-order compensation circuit using a digital and a panoramic image _峨 at the same time. Image sensor and related methods. [Prior Art] Semiconductor image sensors (such as charge-dissipating components (CCD) or complementary metal-oxide-semiconducting semiconductors (CMOSM·) generally enable inspection instruments or wipes to convert visible light images into electronic signals for subsequent follow-up Storage, transmission or display. Due to the imperfect nature of the electronic circuit, the image sensor still has leakage current when it does not receive any light, so the image sensing ail number generated by the image will be included. The component of the leakage current does not truly reflect the sensed image intensity. To overcome this problem, multiple rows of optical black pixels (or light-shielded pixels) are usually read. After averaging, it is used as a black level compensation value. This black level compensation value is used to indicate the leakage current that the image sensor still has when it does not receive any light. Please refer to Figure 1 for the first example of the known black level compensation. A schematic diagram of the circuit 100. As shown in FIG. 1, the black level compensation circuit 100 includes an adder 102, an analog amplifier 104, an analog-to-digital converter 丨〇6, a digital amplifier ι〇8, and a black level. The positive single 201246928 element 110 and the digital analog converter 112. In the operation of the black level compensation circuit 100, the black level compensation circuit _ reads the black pixel sensing signal in the image sensing signal Vin, and by analogy amplification 2104 The analog digital converter 1G6 and the digital amplifier (10) are processed and input into the black level correction unit (10), and the black level correction unit 110 averages the received black image honest values to obtain a black_compensation value. Then, the black level compensation value is returned to the addition by the digital analog converter 122 to compensate the image sensing call Vln, so that the image sensing signal received by the image processing unit 120 can truly reflect the sensed image brightness value. ^ j and the analog digital converter (10) of the black p white complement circuit 100 and the black 11 single 11G will have a large time delay 'and the digital analog conversion of $ 112 will produce a quantization error 'this is the traditional black _ The speed and accuracy of the compensation circuit 1GG cannot be improved. In addition, if the Rayleigh is used to perform black level compensation, there will be a problem that the hot pixel cannot be efficiently removed, and it cannot be accurate. Therefore, one of the objects of the present invention is to provide a black-order compensation circuit and a related method for simultaneously performing black-level compensation on a shirt image sensing signal by using a digital and analog circuit to solve the above problem. According to an embodiment of the invention, a black level compensation circuit includes a first processing unit 201246928, a second processing unit, and a compensation unit. The first processing unit receives the received data according to the -th threshold value. a first digital black pixel sensing signal performs a hot pixel erasing operation to generate a filtered first black pixel sensing signal, and generates a second threshold according to the filtered first black pixel sensing signal The second processing unit performs a hot pixel filtering operation on the received second digital black pixel sensing signal according to the second threshold to generate a filtered second black pixel sensing signal, and according to the Filtering the second accumulated pixel sensing signal to generate a black level compensation value; the compensation unit performs black level compensation on the received image sensing signal according to the black level compensation value To get an output signal. According to another embodiment of the present invention, a black level compensation method includes: performing a hot pixel filtering operation on a first digital black pixel sensing signal according to a first threshold value to generate a filtered first black a pixel sensing signal, and according to the filtered first black pixel sensing signal to generate a second threshold; according to the second threshold, performing a hot pixel filtering operation on a second digit black pixel sensing signal, Generating a filtered second black pixel sensing signal, and generating a black level compensation value according to the filtered second black pixel sensing signal; and sensing the received image according to the black level compensation value The signal performs black level compensation to obtain an output signal. According to another embodiment of the present invention, an image sensor includes an image sensing unit and a black level compensation circuit, wherein the image sensing unit includes a plurality of sensing pixels and a plurality of black pixels. The black level compensation circuit includes a first processing unit, a second processing unit, and a compensation unit. The first processing unit is coupled to the black pixels for performing a thermal image 201246928-prime filtering operation on the received sensing signals of the black pixels according to a first threshold value to generate a filtered image. The first black pixel sensing signal is generated according to the filtered first black pixel sensing signal to generate a second threshold; the second processing unit is coupled to the black pixels for determining the second threshold Performing a hot pixel filtering operation on the received sensing signals of the black pixels to generate a filtered second black pixel sensing signal, and generating a second black pixel sensing signal according to the filtering a black level compensation value; the compensation unit is coupled to the sensing pixels for performing black level compensation on the image sensing signals of the sensing pixels according to the black level compensation value to obtain an output signal. [Embodiment] Please refer to FIG. 2, which is a schematic diagram of a black level compensation circuit 200 according to an embodiment of the present invention. As shown in FIG. 2, the black level compensation circuit 2 includes an analog black level correction unit 202, an analog digital converter 208, a first processing unit 210, a first multiplexer 220, and an adder 222. a multiplier 224, a second processing unit 230, a second multiplexer 240, and a compensation unit (in the present embodiment, the compensation unit is an adder 250), wherein the analog black level correction unit 202 includes an addition method The 203, an analog amplifier 204, and a black level value calculation unit 206. In the operation of the black-order compensation circuit 2, first, the analog black-order correction unit 2〇2 receives the analog black pixel sensing signal Vin from the image sensor (not shown), and senses the analog black pixel sensing signal. Vin performs a black level adjustment operation to produce an adjusted analog black pixel sensing signal. In detail, the analog black pixel sensing signal Vin is input to the black level value calculating unit 206 after passing through the adder 203 and the analog amplifier 204, and then the black level value calculating unit 206 performs the received analog black pixel sensing signal Vi η. The averaging operation (for example, 201246928, for example, low-pass filtering operation) is to generate a correction value vBLC to the adder 203 so that the analog black pixel sensing signal Vin will be as close as possible to a gray level representing all black after passing through the adder 203. value. In other embodiments, the analog black level correction unit 2〇2 may use a subtractor or a mixer instead of the adder 203. However, due to the fatigue of the image sensor during the production process, a small number of tired pixels have a so-called "hot pixel" phenomenon, that is, in some cases, the sensing signals output by the black pixels will Has a large current / voltage. Therefore, the correction value VBLC calculated by the black-order value calculation unit 2〇6 is likely to be inaccurate due to the “hot pixel” phenomenon of a small number of black pixels, thereby causing the output of the analog black-order correction unit 2〇2. It does not approach a grayscale value representing all black, that is, the analog digital converter 2〇8 receives the output of the black matrix correction sheet 7L 202 to generate a digital black pixel sensing signal Din that may not reach a value close to “0”. Or a very low digital value. Therefore, the first processing unit 210 receives the first digital black pixel sensing signal in the digital black pixel sensing signal Din, and performs hot pixel on the first digital black pixel sensing signal according to a first threshold TH1. The filtering operation is performed to generate a black pixel sensing 峨 after filtering, and the + first touch, Weisu fine city may be a numb number containing a plurality of black pixels (for example, a whole line of black pixels), and the secret is removed. The operation P removes the digit value of the first digital black pixel sensing signal that is greater than the first threshold TH1. Then, the 'th processing unit 21', _ averages the plurality of digital values in the first-black pixel sensing hole number to generate a second critical value TH2. 201246928, the first multiplexer 220 selectively turns the first threshold TH1 or the second threshold TH2 according to a first selection signal SEL1, after which the output of the first multiplexer 220 is via the adder 222 and The adjustment of the multiplier 224 is then input to the second processing early element 230. It should be noted that the adder 222 and the multiplier 224 are used to adjust the first critical value ΤΗ 1 or the second critical value TH2 numerically, and are all non-essential (〇pti〇nai) components. That is, the adder 222 and the multiplier 224 can be removed from the black-order compensation circuit 2〇〇 without affecting the operation of the black-order compensation circuit 2〇〇. Then, the second processing unit 230 receives a second digital black pixel sensing signal of the digital black pixel sensing signal Din, and according to the first threshold TH1 or the second threshold value output by the first multiplexer 220 Performing a hot pixel filtering operation on the second digital black image field to generate a filtered second black pixel sensing signal, wherein the second digital black pixel sensing signal may include a plurality of black pixels (eg, The sensing signal of the other black pixel is removed, and the hot pixel filtering operation removes the digit value of the second digital black pixel sensing signal that is greater than the first threshold TH1 or the second threshold TH2. Then, the second processing unit 23 continues to perform the averaging operation on the plurality of second black pixel sensing signals after the rounding, and accordingly generates a black level compensation value Dbk. For example, the operation of the first processing unit 21〇 and the second processing unit 23〇 is described. Referring to FIG. 3, it is assumed that the black dot shown in FIG. 3 is a numerical distribution diagram of the first digital black pixel sensing signal. The axis is a numerical value. Then, the first critical value thi can be set to 9 201246928 as a higher-digit value, such as "Xiao, so that the first processing unit 21G divides the hot pixel value of the month, and the second threshold is shown. Η2 can be the average of all black money signals at the first threshold TH1, which is assumed to be "55,". Therefore, 'assuming that the second digital black pixel sensing warfare has a similar numerical distribution to the first-digit black pixel sensing signal, the second processing unit can further eliminate the less obvious "hot pixel" value ( That is, the black pixel sensing signal whose value is above "Μ", and the flatness calculation of all the black pixel sensing signals below the second threshold TH2, and the black level compensation value DBLC are obtained. In the step of determining the black level compensation value dblc, in an embodiment, the average value of all the black pixel sensing signals below the second threshold TH2 may be set to the black level compensation value Dblc, that is, if the third is If the average value of all the accumulated pixel sensing signals below the second threshold TH2 shown in the figure is "40", the black-order compensation value Dblc is set to "4" to cause the output signal Dout of the black-order compensation circuit 200 to be eliminated. The component of the black pixel leakage current; in another embodiment, if the average value of all the black pixel sensing signals below the second threshold TH2 shown in FIG. 3 is “40”, the average value may be used according to the average value. The black level compensation value DBLC is set by calculation or adjustment, for example, "25". Then, the second multiplexer 240 selectively rotates the black level compensation value DBLC or a third threshold TH3 to the adder 250 according to a second selection signal SEL2, after which the adder 250 according to the black level compensation value DBLC Or the third threshold TH3 is used to perform black level compensation on the received image sensing signal to obtain an output signal Dout to the image processing circuit (not shown) at the back end. 10 201246928 β4/ thought of the '疋-multiplexer 22〇 function is only for the designer / user to choose whether to skip the output of the processing unit 21Q, and directly let the second multiplexer use the critical The value TH1 is used for the hot pixel erasing operation. Therefore, if the selection function is not required, the first multiplexer 220 can also be removed from the black matrix compensation circuit 200, and the second threshold value TH2 output by the first processing unit 210 is directly input to the adder slave. Similarly, the function of the $28 is for the designer/user to choose whether to skip the output of the second 23G of the second process and directly let the adder 25() use the third threshold TH3 to receive the received Image sensing is performed in black. If the selection function is not required, the second multiplexer 24G can also be removed from the black level surface circuit, and the black level compensation value DBLC output by the second processing unit 230 is directly input to the adder 250. ° As described above, the digital circuit in the black level compensation circuit 2 can obtain an ideal black level compensation value DBLC so that the output signal Dout corresponding to the digital black pixel sensing signal can be close to "〇,, or As a result, the black level compensation circuit 200 can accurately compensate the black image of the subsequent received image sensing signals. Further, since the black level compensation circuit 200 first uses the analog circuit. To perform the first-stage black-order compensation, and then use the digital circuit to eliminate the "hot pixel", which affects the second-stage black-order compensation. Therefore, the speed of the digital black-order compensation circuit 11 201246928 in the prior art can be avoided. And the accuracy problem, as well as avoiding the accuracy problem caused by the thermal pixel factor in analogy black-scale compensation circuits in the prior art. FIG. 4 is a schematic diagram of an image sensor 400 according to an embodiment of the invention. As shown in FIG. 4, the image sensor 4A includes an image sensing unit 420 and a black level compensation circuit 460. The image sensing unit 420 includes a plurality of sensing pixels and a plurality of black pixels ′ and outputs the sensing signals of the black pixels and the image sensing signals Vin of the sensing pixels to the black matrix compensation circuit 460. In the operation of the image sensor 400, the black level compensation circuit 460 receives the sensing signals of the black pixels, and processes the sensing signals of the black pixels to generate a black level compensation value, and then black level compensation. The circuit 460 further performs black level compensation on the image sensing signals of the sensing pixels according to the black level compensation value to obtain an output signal Dout. The black level compensation circuit 460 includes an analog digital converter 408, a first processing unit 410, a second processing unit 430, and a compensation unit (adder) 450. The first processing unit 410 performs a hot pixel filtering operation on the received sensing signal of the black pixel according to the first threshold TH1 to generate a filtered first black pixel sensing signal, and according to the filtered first The black pixel senses the signal to produce a second threshold TH2. The second processing unit 430 is coupled to the black pixels, and performs a hot pixel filtering operation on the sensing signals of the received black pixels according to the second threshold TH2 to generate a second black pixel sensing signal after filtering. And according to; the first black pixel sensing signal is considered to generate the black level compensation value dblc. The compensation unit 450 is configured to perform black level compensation on the image sensing signal of the sensing pixel according to the black level compensation value Dblc to obtain an output signal Dout. The black pixel sensing signal received by the first processing unit 12 201246928 - and the second processing unit 430 may be an analog signal directly from the image sensing unit 420 or, as in this embodiment, through an analog digital converter. The digital signal from 408. In an embodiment, the second threshold TH2 is less than the first threshold TH1. The first processing unit 410 performs an averaging operation on the filtered first black pixel sensing signals, and accordingly generates a second threshold TH2. The black level compensation circuit 460 of this embodiment may also include the analog black level correction unit 202 in the other embodiments described above. Briefly summarized in the present invention, in the black-order compensation circuit and related method of the present invention, a black-order compensation circuit for black-order compensation and a related method thereof are used in the black-order compensation circuit and the 敝 circuit image sensing signal, and the black-order compensation circuit The digital circuit part can accurately eliminate the influence of the hot pixel, and the next step is to take the black signal compensation to obtain the ideal output signal. The embodiments described herein are intended to be within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of a conventional black-order compensation circuit. : 2 == Ming, _ circuit schematic. Figure 4 is a schematic diagram of the operation of the Γ processing unit. BRIEF DESCRIPTION OF THE DRAWINGS The Figure is a schematic illustration of an image viewer in accordance with the present invention. 13 201246928 [Description of main component symbols] 100, 200, 460 black level compensation circuit 102, 203, 222, 250, 450 adder 104, 204 analog amplifier 106, 208, 408 analog digital converter 108 digital amplifier 110 black level correction unit 112 digital analog converter 120 image processing unit 202 analog black level correction unit 206 black level value calculation unit 210 > 410 first processing unit 220 first multiplexer 224 multiplier 230, 430 second processing unit 240 second multiplex 400 image sensor 420 image sensing unit s 14