1331331 九、發明說明： 【發明所屬之技術領域】 本發明係有關於光碟儲存裝置，尤其是有關於偵測 光碟片空白未記錄狀態的方法。 【先前技術】 第la圖係為一習知的光學儲存裝置。一般來說，儲 '存在光碟中的資料在傳送至解碼器之前，會先經過放大 籲和數位化的步驟，以將訊號的振幅調整為一目標值。可 變增益放大器102,類比數位轉換器104和自動益增控制 器106形成一個自動增益控制器回路，用來調整光學訊 號#10^的增益。而空白偵測器110提供一額外的資料通 路，用以偵測光學訊號#RF的一空白狀態（blankness)，其 中光學訊號#RF的空白狀態係對應於光碟片上一執道中 之至少一空白未燒錄區段（blank sector)。如果光學訊號 #RF的振幅大小低於一臨界值，則該光學訊號#RF對應 * 該空白狀態，因此解碼器108不啟動，而對應的光碟片 紀錄區段（recording sector)則回報為空白未燒錄區段。相 對的，如果光學訊號#尺卩不是空白狀態，則空白偵測器 110傳送一致能訊號#611至該解碼器108,使解碼器108 啟動，以對類比數位轉換器104輸出的資料訊號#0人丁人 進行解碼處理。 第lb圖係為定義空白狀態的示意圖。當光學訊號 #RF的振幅大小低於臨界值（+th和-th)時，則對應的紀錄 0758-A32233TWF;MTKI-06-252;yeatsluo 6 1331331 區段則視為空白區段。相對的，當光學訊號#RF的振幅 大小超過臨界值訊號時，則對應的紀錄區段則視為非空 白區段，因此啟動解碼器108對資料訊號#DATA進行處 理。 【發明内容】 本發明提出一種光學儲存裝置，以及實作於其中的 空白狀態偵測方法。首先從一光碟片讀取一光學訊號。 一可變增益放大器根據一控制訊號將該光學訊號放大。 一類比數位轉換器取樣該光學訊號以產生一資料訊號。 一自動增益控制器根據該資料訊號的大小更新該控制訊 號。一空白偵測器將該資料訊號與一臨界值訊號比較， ，偵測一空白狀態。一臨界值訊號產生器根據該控制訊 號而產生該臨界值訊號。如果該資料訊號的大小不超過 該臨界值訊號，該空白偵測器傳送—暫停訊號使該控制 訊號暫時停止更新。 «亥光學儲存農置可進—步包含—解碼器_接該類比 數位轉換器和空白㈣器，其中如果該資料訊號的大小 超過該臨界值訊號，則該空白_器產生—致能訊號使 該解碼器啟動，使該解碼器開始處理該資料訊號。 該臨界值訊號產生器可包含_查詢表，用以提供一 線性轉換關係，以㈣該控制訊號產生該臨界值訊號。 。亥&™界值λ號產生器也可以—硬體電路來達成，包 含-控制器，-乘法ϋ和-加法器。該控制器根據該控 0758-A32233TWF;MTKI-06-252;yeatsluo 7 1331331 制訊號產生一斜率值和一偏移值，乘法器將該控制訊號 乘以該斜率值。而該加法器將該乘法器的輸出加上該偏 移值，以產生該臨界值訊號。 虽δ玄控制訊號的大小在一第一範圍内，該控制器產 生一第一斜率值，及一第一偏移值。當該控制訊號的大 小在一第二範圍内’該控制器則產生一第二斜率值，及 一第二偏移值。 該空白偵測器包含一高通濾波器，一遲滯元件 (hysteresis)和一計數器。高通濾波器將該資料訊號中的低 頻成份濾除。遲滯元件根據該臨界值訊號將該資料訊號 量化為一方波訊號。計數器統計該方波訊號的工作週期 以偵測該空白狀態。該光學儲存裝置可更進一步包含一 解，器。如果該計數器偵測到低位準的方波訊號，該計 數益產生一致能訊號以啟動該解碼器，使該解碼器開始 處理該資料訊號。 為讓本發明之上述和其他目的、特徵、和 明顯易懂，下文特舉出較佳實施例，並配合所附圖式， 作洋細說明如下： 【實施方式】 力第2圖係為一光學儲存裝置的實施例。本實施例的 架構不同於以往。空白偵測器22〇使用從類比數位轉換 器輸出的資料訊號#DATA來偵測空白狀態，藉此節省第 1圖所示空白偵測器110資料路徑上的電路成本。空白偵 〇758-A32233TWF;MTKi.06.252；yeatsluo 8 1.331331 測器220係以數位電路的方式實作，成本更低於類比電 路。在第1圖中，類比數位轉換器輸出的資料訊-#DATA 被送至自動益增控制器106,而自動益增控制器106產生 -- 一控制訊號#cH至可變增益放大器102以調整光學訊號 #RF的增益值。藉此資料訊號#0人丁入的大小在遞迴調整 的過程中漸漸逼近一目標值。由於資料訊號#DΑΤΑ的大 小一直在變動中，空白偵測器220可能判斷錯誤。為了 $確保判斷正確，本發明提出一種臨界值訊號產生器210， 用以提供動態的臨界值訊號#th，正比於控制訊號#(^1。 當資料訊號#DΑΤΑ被放大時該臨界值訊號#th也被放 大，使得空白偵測器220偵測空白狀態的功能不受到可 變增益放大器102增益的影響。 如果空白狀態持續了一段時間，該自動增益控制器 回路可能又逐漸的把光學訊號#RF的增益放大到趨近於 該目標值，形成我們不樂見的發散現象。因此在空白偵 φ 測器220中另有一個功能來解決這個問題。如果該資料 訊號#DATA的大小沒超過臨界值訊號#th，表示光學訊號 #RF是處於空白狀態。這時空白偵測器220發出一暫停 訊號#hold給自動益增控制器106，命令它暫停更新控制 訊號#ctrl。如此一來，可以使空白狀態下的光學訊號#RF 之增益就保持不變。在此同時空白偵測仍然持續在進 行。當發現資料訊號#DATA是非空白狀態時，則自動益 增控制器106重新啟動，繼續更新控制訊號#ctrl，以恢 復自動增益控制器回路的功能。 0758-A32233TWF；MTKl-06-252;yeatsluo 9 1331331 第3a圖係為第2圖中臨界值訊號產生器21〇的一實 施例。第3b ®表示增益和控制訊號#ct相關係圖。臨界 值訊號#th基本上和可變增益放大器1〇2中的增益一樣， 都正比於控制訊號#ctrl。為了簡化該臨界值訊產生器1331331 IX. Description of the Invention: [Technical Field of the Invention] The present invention relates to a disc storage device, and more particularly to a method for detecting a blank unrecorded state of an optical disc. [Prior Art] The first drawing is a conventional optical storage device. In general, the data stored in the disc is transmitted to the decoder and then subjected to an amplification and digitization step to adjust the amplitude of the signal to a target value. Variable gain amplifier 102, analog digital converter 104 and automatic benefit controller 106 form an automatic gain controller loop for adjusting the gain of optical signal #10^. The blank detector 110 provides an additional data path for detecting a blankness of the optical signal #RF, wherein the blank state of the optical signal #RF corresponds to at least one blank in an obstruction on the optical disc. Burning sector. If the amplitude of the optical signal #RF is lower than a critical value, the optical signal #RF corresponds to the blank state, so the decoder 108 does not start, and the corresponding recording sector returns a blank. Burn section. In contrast, if the optical signal # is not blank, the blank detector 110 transmits the coincidence signal #611 to the decoder 108 to cause the decoder 108 to start to output the data signal #0 to the analog digital converter 104. Ding people perform decoding processing. The lb diagram is a schematic diagram for defining a blank state. When the amplitude of the optical signal #RF is lower than the critical value (+th and -th), the corresponding record 0758-A32233TWF; MTKI-06-252; yeatsluo 6 1331331 segment is regarded as a blank segment. In contrast, when the amplitude of the optical signal #RF exceeds the threshold signal, the corresponding record segment is regarded as a non-empty segment, so the decoder 108 is activated to process the data signal #DATA. SUMMARY OF THE INVENTION The present invention provides an optical storage device, and a blank state detecting method implemented therein. First, an optical signal is read from a disc. A variable gain amplifier amplifies the optical signal based on a control signal. A class of digital converters samples the optical signal to produce a data signal. An automatic gain controller updates the control signal based on the size of the data signal. A blank detector compares the data signal with a threshold signal to detect a blank state. A threshold signal generator generates the threshold signal based on the control signal. If the size of the data signal does not exceed the threshold signal, the blank detector transmits a pause signal to temporarily stop the control signal from being updated. «Hai optical storage farm can enter - step includes - decoder _ connected to the analog digital converter and blank (four), wherein if the size of the data signal exceeds the threshold signal, the blank _ device generates - enable signal The decoder is enabled to cause the decoder to begin processing the data signal. The threshold signal generator may include a _ lookup table for providing a linear conversion relationship to generate the threshold signal by the control signal. . The HI &TM threshold λ generator can also be implemented as a hardware circuit, including a -controller, -multiply ϋ and -adder. The controller generates a slope value and an offset value according to the control 0758-A32233TWF; MTKI-06-252; yeatsluo 7 1331331 signal, and the multiplier multiplies the control signal by the slope value. The adder adds the offset value to the output of the multiplier to generate the threshold signal. Although the size of the δ 控制 control signal is within a first range, the controller generates a first slope value and a first offset value. When the size of the control signal is within a second range, the controller generates a second slope value and a second offset value. The blank detector includes a high pass filter, a hysteresis and a counter. The high pass filter filters out the low frequency components of the data signal. The hysteresis component quantizes the data signal into a square wave signal based on the threshold signal. The counter counts the duty cycle of the square wave signal to detect the blank state. The optical storage device can further include a solution. If the counter detects a low level square wave signal, the counting yields a consistent energy signal to activate the decoder, causing the decoder to begin processing the data signal. The above and other objects, features, and advantages of the present invention are set forth in the <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; An embodiment of an optical storage device. The architecture of this embodiment is different from the past. The blank detector 22 uses the data signal #DATA output from the analog digital converter to detect the blank state, thereby saving the circuit cost on the data path of the blank detector 110 shown in FIG. Blank Detector 758-A32233TWF; MTKi.06.252; yeatsluo 8 1.331331 The Detector 220 is implemented in the form of a digital circuit, and the cost is lower than the analog circuit. In Fig. 1, the data signal -#DATA output by the analog-to-digital converter is sent to the automatic gain controller 106, and the automatic boost controller 106 generates a control signal #cH to the variable gain amplifier 102 for adjustment. The gain value of optical signal #RF. The size of the data signal #0 person is gradually approaching a target value in the process of recursive adjustment. Since the size of the data signal #DΑΤΑ is constantly changing, the blank detector 220 may judge the error. In order to ensure that the judgment is correct, the present invention proposes a threshold signal generator 210 for providing a dynamic threshold signal #th, which is proportional to the control signal #(^1. When the data signal #DΑΤΑ is amplified, the threshold signal # Th is also amplified so that the function of the blank detector 220 to detect the blank state is not affected by the gain of the variable gain amplifier 102. If the blank state continues for a while, the automatic gain controller loop may gradually turn the optical signal# The gain of the RF is amplified to approach the target value, forming a divergence phenomenon that we are not happy with. Therefore, there is another function in the blank detector 220 to solve this problem. If the size of the data signal #DATA does not exceed the critical value The value signal #th indicates that the optical signal #RF is in a blank state. At this time, the blank detector 220 sends a pause signal #hold to the automatic gain controller 106, instructing it to suspend the update control signal #ctrl. The gain of the optical signal #RF in the blank state remains unchanged. At the same time, the blank detection continues. When the data signal #DATA is found to be non-empty In the state, the automatic boost controller 106 restarts and continues to update the control signal #ctrl to restore the function of the automatic gain controller loop. 0758-A32233TWF; MTKl-06-252; yeatsluo 9 1331331 3a is the second An embodiment of the threshold signal generator 21A is shown in the figure. The 3b ® represents the relationship between the gain and the control signal #ct. The threshold value #th is basically the same as the gain in the variable gain amplifier 1〇2. For control signal #ctrl. To simplify the threshold generator
210的實作，可採用數位電路以近似運算的方式來產生該 線性關係。在第3 b圖中，曲線z代表可變增益放大器工^ 根據控制訊號#ctrl產生的增益值。直線yl和y2代表臨 界值訊號產生器210使用的近似曲線，用來產生臨界值 讯號#th。臨界值訊號產生器21〇包含一加法器3〇6 控制器302和一乘法器304。直線…和y2可以表示為 yn=anx+bn 其中η是整數，an是斜率，而\是偏移值。 在第3a圖中，控制器302根據控制訊號知⑴的大 小產生一斜率值#51〇%和一偏移值#〇ffset。接著乘法器 304將控制訊號#c出乘以斜率值#sl〇pe，而相乘結果送至 •加法器306 ’與該偏移值Offset相加，以產生臨界值訊號 #th。控制訊號#ctrl的大小可以區分為複數個範圍，每一 範圍對應一組不同的斜率值和偏移值。舉例來說，在第 3 b圖中η專於2，所以使用兩條直線來近似曲線z。當該 控制訊號如⑴的大小為第一範圍，則該控制器3〇2產生 斜率值al以及偏移值bl。當該控制訊號#cM的大小為第 二範圍，則該控制器302產生斜率值a2以及偏移值b2。 η的值不限定為2，而數字越大可以得到越精確的近似結 果。此外，臨界值訊號產生器210也可以包含一數位查 〇758-A32233TWF；MTKI-06-252;yeatsluo 10 1331331 詢表’查詢表中包含不同的控制訊號知⑺，以及其對應 之不同的臨界值訊號#th。曲線Z通常是在習知的校準程 序中就能決定’因此臨界值訊號產生器210的設定也可 以在校準的時候一併設定。 第4圖係為第2圖中空白偵測器220的一實施例。 該空白偵測器220包含三個數位元件，高通濾波器4〇2， 遲滞元件（hysteresis)404和計數器406。該高通濾波器402 籲過濾資料訊號#0ΑΤΑ中的低頻成份，留下高頻的部份。 該遲滯元件404耦接高通濾波器402，將該資料訊號 #DATA量化為一種方波訊號的形式，只有〇和1兩種狀 態’各具有不同的工作週期（duration)。該計數器406統 a十該方波訊號的工作週期以產生一計數值，並利用該計 數值來判斷光學訊號#RF的空白狀態是否成立。 界值訊號#th可以輸入至遲滯元件404中，用以調 整產生方波訊號的靈敏度。當高通濾波器4〇2輸出的資 籲料訊號#DATA在振幅大小低於臨界值訊號#th對應之振 幅大小程度時輸出低位準訊號，當高通濾波器4〇2輪出 的資料訊號#DΑΤΑ在振幅大小高於臨界值訊號針^對應 之振幅大小程度時輸出高位準訊號，以形成該方波訊 號。而计數克406在計數方波訊號的工作週期時就，若 偵測到低位準方波訊號時，即判斷為空白狀態。當叶數 器406偵測到高位準方波訊號時，即判斷為非空白狀熊， 並送出致能訊號#en將解碼器108啟動，使解碼器1〇8"開 始對資料訊號#DΑΤΑ進行解碼處理。 0758-A32233TWF;MTKI-06-252;yeatsluo 11 1331331 於另一實施例中，臨界值訊號#th也可以輸入至計數 器406中，用以改變空白狀態是否成立的判斷標準。舉 例來說，若偵測到低位準方波訊號之計數值超過對應於 臨界值訊號#th之一預定計數值時，即判斷為空白狀態。 當計數器406偵測到高位準方波訊號時，即判斷為非空 白狀態，並送出致能訊號#en將解碼器.108啟動，使解碼 器108開始對資料訊號#0八丁人進行解碼處理。 第5圖係為本發明實際應用時的波形變化示意圖。 在tl階段，資料訊號#DATA的大小並未超過臨界值訊號 #th，所以光學訊號#RF被回報為空白狀態，而自動益增 控制器106受暫停訊號#hold的控制而暫停更新，使臨界 值訊號#th維持不變的值。在t2階段，資料訊號#DATA 超過臨界值訊號#th，所以自動增益控制器回路恢復運 作，漸漸的將資料訊號#DATA放大而趨近於目標值 (+-target)。同時，臨界值訊號#th也隨著資料訊號#D AT A 的增益變大而放大。在t3階段中，資料訊號#DATA的大 小回復小於臨界值訊號#化，意即進入另一段空白狀態。 值得注意的是此時的臨界值訊號#th比tl階段時之臨界 值訊號#th還高。如果臨界值訊號#th未能動態調整，則 t3階段的資料訊號#0人丁人可能被固定的臨界值訊號#th 誤判斷為非空白狀態。在t3階段既然已判斷為空白狀 態，則自動增益控制器回路又進入暫停狀態，使臨界值 訊號#th和可變增益放大器102的增益一樣都維持在不變 的值。在t4階段中表示資料訊號#DATA出現了超過目標 0758-A32233TWF;MTKI-06-252;yeatsluo 12 1331331 值的情況，所以自動增益控制器回路遞迴的運作使其趨 近於目標值（+-target)。而在此同時，臨界值訊號齡的值 也隨著增益下降。上述的例子說明了本發明動態地調整 臨界值訊號#th來避免錯誤的判斷結果。 第6圖係為偵測空白狀態的流程圖。在步驟中， 可變增益放大器1〇2根據控制訊號將光學訊號卿 放大。在步驟604 t，該類比數位轉換器將光學訊號卿 #，樣以得到-資料訊號#DATA。在步驟6G6中，該自動 益增控制器106根據資料訊號#DATA的大小更新控制訊 號㈣。在步驟608巾，臨界值訊號產生器21〇根據控 制訊號#ctrl提供-臨界值訊號齢。在步驟61〇中，空白 偵測器220輯臨界值訊號_偵測資料訊號㈣下八的 空白狀態。在步驟612中，如果資料訊號奶八以不是空 白狀態’貝啟動解碼器、⑽對該資料訊號#DATA進行解 碼。在步驟614巾，如果該資料訊號#DATA是空白狀能， 空⑽測器220關閉解瑪器⑽，並暫停自動益增控、制 益106的運作使自動增益控制器回路不動作。 【圖式簡單說明】 第1 a圖係為一習知的光學儲存裝置。 第1b圖係為定義空白狀態的示意圖。 第2圖係為一光學儲存裝置的實施例。 ”a圖係為第2圖中臨界值訊號產生器的實施例。 第3b圖表示增益和控制訊號的關係圖。 〇758-A32233TWF；MTKI-O6.252;yeatslu〇 1331331 第4圖係為第2圖中空白偵測器的實施例。 第5圖係為本發明實際應用時的波形變化示意圖 第6圖係為偵測空白狀態的流程圖。 【主要元件符號說明】 102〜可變增益放大器； 106〜自動增益控制器； 110〜空白偵測器； 210〜臨界值訊號產生器； 3 02〜控制器； 306〜加法器； 404〜遲滯元件； 104〜類比數位轉換器； 108〜解碼器； 220〜空白偵測器； 304〜乘法器； 402〜南通滤波β， 406〜計數器。 0758-A32233TWF;MTKI-06-252;yeatsluo 14The implementation of 210 can be performed by a digital circuit in an approximated manner. In Fig. 3b, the curve z represents the gain value produced by the variable gain amplifier according to the control signal #ctrl. The lines yl and y2 represent the approximate curves used by the threshold value signal generator 210 to generate the threshold value signal #th. The threshold signal generator 21A includes an adder 3〇6 controller 302 and a multiplier 304. Lines... and y2 can be expressed as yn=anx+bn where η is an integer, an is the slope, and \ is the offset value. In Fig. 3a, the controller 302 generates a slope value #51〇% and an offset value #〇ffset based on the size of the control signal (1). Next, the multiplier 304 multiplies the control signal #c by the slope value #sl〇pe, and the multiplication result is sent to the adder 306' to add the offset value Offset to generate the threshold value signal #th. The size of the control signal #ctrl can be divided into a plurality of ranges, each range corresponding to a different set of slope values and offset values. For example, in Figure 3b, η is specific to 2, so two straight lines are used to approximate curve z. When the size of the control signal such as (1) is the first range, the controller 3〇2 generates the slope value a1 and the offset value bl. When the size of the control signal #cM is the second range, the controller 302 generates the slope value a2 and the offset value b2. The value of η is not limited to 2, and the larger the number, the more accurate the approximate result is obtained. In addition, the threshold signal generator 210 may also include a digital check 758-A32233TWF; MTKI-06-252; yeatsluo 10 1331331 query table 'the query table contains different control signals (7), and their corresponding different thresholds Signal #th. The curve Z is usually determined in a conventional calibration procedure. Thus, the setting of the threshold signal generator 210 can also be set at the time of calibration. Figure 4 is an embodiment of the blank detector 220 of Figure 2. The blank detector 220 includes three digital components, a high pass filter 4〇2, a hysteresis 404, and a counter 406. The high pass filter 402 appeals to filter the low frequency components in the data signal #0ΑΤΑ, leaving the high frequency portion. The hysteresis component 404 is coupled to the high pass filter 402 to quantize the data signal #DATA into a square wave signal form, and only the 〇 and 1 states have different duty cycles. The counter 406 integrates the duty cycle of the square wave signal to generate a count value, and uses the count value to determine whether the blank state of the optical signal #RF is established. The threshold value #th can be input to the hysteresis element 404 to adjust the sensitivity of the square wave signal. When the amplitude signal size of the high-pass filter 4〇2 is lower than the amplitude level corresponding to the critical value signal #th, the low level signal is output, and when the high-pass filter 4〇2 rotates the data signal #DΑΤΑ When the amplitude is higher than the magnitude of the amplitude corresponding to the threshold signal, the high level signal is output to form the square wave signal. When the counter 406 counts the duty cycle of the square wave signal, if the low quasi-square wave signal is detected, it is judged to be blank. When the leaf counter 406 detects the high level square wave signal, it is judged to be a non-blank bear, and the enable signal #en is sent to activate the decoder 108, so that the decoder 1〇8" starts to perform the data signal #DΑΤΑ Decoding processing. 0758-A32233TWF; MTKI-06-252; yeatsluo 11 1331331 In another embodiment, the threshold signal #th can also be input to the counter 406 for changing the criterion for determining whether the blank state is established. For example, if it is detected that the count value of the low-order square wave signal exceeds a predetermined count value corresponding to one of the threshold value signals #th, it is judged to be a blank state. When the counter 406 detects the high level square wave signal, it judges that it is not blank, and sends the enable signal #en to start the decoder .108, so that the decoder 108 starts decoding the data signal #0 八丁人. Figure 5 is a schematic diagram showing waveform changes in the actual application of the present invention. In the tl phase, the size of the data signal #DATA does not exceed the critical value signal #th, so the optical signal #RF is reported as a blank state, and the automatic gain controller 106 is suspended by the control of the pause signal #hold, making the criticality The value signal #th remains unchanged. In the t2 phase, the data signal #DATA exceeds the threshold signal #th, so the automatic gain controller loop resumes operation, gradually amplifying the data signal #DATA to approach the target value (+-target). At the same time, the threshold value signal #th is also amplified as the gain of the data signal #D AT A becomes larger. In the t3 phase, the size of the data signal #DATA is less than the threshold value signal, meaning that it enters another blank state. It is worth noting that the critical value signal #th at this time is higher than the critical value signal #th at the time of the tl phase. If the critical value signal #th fails to be dynamically adjusted, the data signal #0 of the t3 stage may be misjudged as a non-blank state by the fixed threshold signal #th. Since it has been judged to be blank in the stage t3, the automatic gain controller circuit enters the pause state again, so that the threshold value signal #th and the gain of the variable gain amplifier 102 are maintained at the same value. In the t4 phase, the data signal #DATA appears to exceed the target 0758-A32233TWF; MTKI-06-252; yeatsluo 12 1331331 value, so the automatic gain controller loop recursive operation makes it approach the target value (+- Target). At the same time, the value of the critical value signal age also decreases with the gain. The above example illustrates that the present invention dynamically adjusts the threshold value signal #th to avoid erroneous judgment results. Figure 6 is a flow chart for detecting blank states. In the step, the variable gain amplifier 1〇2 amplifies the optical signal according to the control signal. At step 604 t, the analog digital converter will optically signal #, to obtain - data signal #DATA. In step 6G6, the automatic boost controller 106 updates the control signal (4) according to the size of the data signal #DATA. At step 608, the threshold signal generator 21 provides a -threshold signal 〇 based on the control signal #ctrl. In step 61, the blank detector 220 records the blank state of the lower eight signals of the critical value signal_detecting data signal (4). In step 612, if the data signal is not empty, the decoder is activated, and (10) the data signal #DATA is decoded. In step 614, if the data signal #DATA is blank, the empty (10) detector 220 turns off the numerator (10), and suspends the operation of the automatic gain control and the benefit 106 so that the automatic gain controller loop does not operate. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1a is a conventional optical storage device. Figure 1b is a schematic diagram of defining a blank state. Figure 2 is an embodiment of an optical storage device. Figure a is an example of the threshold signal generator in Figure 2. Figure 3b shows the relationship between gain and control signals. 〇758-A32233TWF; MTKI-O6.252; yeatslu〇1331331 2 Embodiment of the blank detector in Fig. 5. Fig. 5 is a schematic diagram showing the waveform change in the actual application of the present invention. Fig. 6 is a flow chart for detecting the blank state. [Description of main component symbols] 102~ Variable gain amplifier 106~automatic gain controller; 110~blank detector; 210~threshold signal generator; 3 02~controller; 306~adder; 404~hysteresis component; 104~ analog to digital converter; 108~decoder 220 ~ blank detector; 304 ~ multiplier; 402 ~ Nantong filter β, 406 ~ counter. 0758-A32233TWF; MTKI-06-252; yeatsluo 14