TWI629643B - Exposure time determination method of image sensing - Google Patents
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Abstract
本發明提出一種影像感測之曝光時間決定方法，包含：提供一第一階 段曝光條件，其中該第一階段曝光條件，包括一第一曝光時間；根據該第一階段曝光條件，感測一影像，以產生一第一直方亮度極大值、一第一直方亮度極小值、與一第一直方寬度；增加或減少該第一曝光時間為一第二曝光時間，以作為一第二階段曝光條件，而感測該影像，進而產生一第二直方亮度極大值、一第二直方亮度極小值、與一第二直方寬度；比較該第一直方寬度與該第二直方寬度，並根據比較結果，而決定一第三曝光時間；以及根據該第三階段曝光條件，感測該影像。 The invention provides a method for determining the exposure time of image sensing, which includes: providing a first order Segment exposure conditions, where the first-stage exposure conditions include a first exposure time; according to the first-stage exposure conditions, an image is sensed to produce a first maximum square brightness and a first minimum square brightness Value, and a first square width; increase or decrease the first exposure time to a second exposure time as a second stage exposure condition, and sense the image to generate a second histogram brightness maximum, A second histogram brightness minimum value and a second histogram width; comparing the first histogram width with the second histogram width, and determining a third exposure time according to the comparison result; and according to the third stage exposure conditions To sense the image.
Description
本發明係有關一種影像感測之曝光時間決定方法，特別是指一種根據影像亮度訊號之直方圖以決定曝光時間的影像感測之曝光時間決定方法。 The invention relates to a method for determining the exposure time of image sensing, and more particularly to a method for determining the exposure time of image sensing based on a histogram of image brightness signals to determine the exposure time.
一般而言，在光學式指紋辨識系統中，常會發生所擷取的指紋影像亮度太高或太低的問題，造成指紋影像不清楚，進而影響了指紋辨識的正確性。而擷取的指紋影像亮度太高或太低的問題，通常是影像感測的曝光時間太長或太短所造成。因此，決定影像感測的曝光時間會影響指紋辨識的正確性。 Generally speaking, in an optical fingerprint recognition system, the problem that the brightness of the captured fingerprint image is too high or too low often causes the fingerprint image to be unclear, which affects the accuracy of fingerprint recognition. The problem that the brightness of the captured fingerprint image is too high or too low is usually caused by the exposure time of the image sensor being too long or too short. Therefore, determining the exposure time of image sensing will affect the accuracy of fingerprint recognition.
有鑑於此，本發明即針對上述先前技術之不足，提出一種根據影像亮度訊號之直方圖以決定曝光時間的影像感測之曝光時間決定方法。 In view of this, the present invention proposes a method for determining the exposure time of image sensing based on the histogram of the image brightness signal to determine the exposure time based on the shortcomings of the foregoing prior art.
就其中一個觀點言，本發明提供了一種影像感測之曝光時間決定方法，包含：S1：提供一第一階段曝光條件，其中該第一階段曝光條件，包括一第一曝光時間；S2：根據該第一階段曝光條件，感測一影像， 並根據所感測影像的亮度分布與對應於各亮度之像素數目，產生一直方統計圖(histogram)，且在該直方統計圖中決定一第一直方亮度極大值、一第一直方亮度極小值、與一第一直方寬度，其中該第一直方寬度為該第一直方亮度極大值與該第一直方亮度極小值之間，像素數目超過一數目閾值的亮度之總數；S3：增加或減少該第一曝光時間為一第二曝光時間，以作為一第二階段曝光條件，而感測該影像，進而產生一第二直方亮度極大值、一第二直方亮度極小值、與一第二直方寬度；S4：比較該第一直方寬度與該第二直方寬度，並根據比較結果，而決定一第三曝光時間；以及S5：根據該第三階段曝光條件，感測該影像。 According to one of the viewpoints, the present invention provides a method for determining exposure time of image sensing, including: S1: providing a first-stage exposure condition, wherein the first-stage exposure condition includes a first exposure time; S2: according to The first stage exposure conditions, sensing an image, Based on the brightness distribution of the sensed image and the number of pixels corresponding to each brightness, a histogram is generated, and a first maximum luminance value and a minimum first luminance value are determined in the histogram. Value, and a first square width, wherein the first square width is the total number of brightnesses between the maximum value of the first square brightness and the minimum value of the first square brightness, and the number of pixels exceeds a threshold; S3 : Increasing or decreasing the first exposure time to a second exposure time as a second stage exposure condition, and sensing the image, thereby generating a second maximum histogram brightness, a second minimum histogram brightness, and A second histogram width; S4: comparing the first square width with the second histogram width, and determining a third exposure time according to the comparison result; and S5: sensing the image according to the third stage exposure conditions .
在其中一種較佳的實施例中，當減少該第一曝光時間為該第二曝光時間，以作為該第二階段曝光條件，而感測該影像，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度不小於該第一直方寬度時，產生一第三曝光時間，以作為一第三階段曝光條件，而感測該影像；其中該第三曝光時間正相關於：將一目標直方值減去該第二直方亮度極小值後，將結果除以該目標直方值，再乘以該第二曝光時間。 In one of the preferred embodiments, when the first exposure time is reduced to the second exposure time as the second stage exposure condition, the image is sensed to generate the second histogram brightness maximum, the When the second histogram brightness is minimum and the second histogram width, and the second histogram width is not less than the first histogram width, a third exposure time is generated as a third stage exposure condition, and the An image; wherein the third exposure time is positively related to: subtracting the second histogram brightness minimum value from a target histogram value, dividing the result by the target histogram value, and then multiplying the second exposure time by the target histogram value.
在其中一種較佳的實施例中，當減少該第一曝光時間為該第二曝光時間，以作為該第二階段曝光條件，而感測該影像，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度小於該第一直方寬度，且該第二直方亮度極大值不大於一目標直方值時，產生一第三曝光時間，以作為一第三階段曝光條件，而感測該影像；其中該第三曝光時間正相關於：將該目標直方值除以該第二直方亮度極大值，再乘以該第二曝光時間。 In one of the preferred embodiments, when the first exposure time is reduced to the second exposure time as the second stage exposure condition, the image is sensed to generate the second histogram brightness maximum, the A third exposure time is generated when the minimum value of the second histogram brightness and the second histogram width are smaller than the first histogram width, and the maximum value of the second histogram brightness is not greater than a target histogram value. , As a third stage exposure condition, and sensing the image; wherein the third exposure time is positively related to: dividing the target histogram value by the second histogram brightness maximum value, and then multiplying by the second exposure time.
在其中一種較佳的實施例中，當減少該第一曝光時間為該第二曝光時間，以作為該第二階段曝光條件，而感測該影像，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度小於該第一直方寬度，且該第二直方亮度極大值大於一目標直方值時，產生一第三曝光時間，以作為一第三階段曝光條件，而感測該影像；其中該第三曝光時間正相關於：將該目標直方值除以該第二直方亮度極小值與該第二直方寬度的和，再乘以該第二曝光時間。 In one of the preferred embodiments, when the first exposure time is reduced to the second exposure time as the second stage exposure condition, the image is sensed to generate the second histogram brightness maximum, the When the second histogram luminance minimum value and the second histogram width are smaller than the first histogram width and the second histogram luminance maximum value is greater than a target histogram value, a third exposure time is generated, The image is sensed as a third-stage exposure condition, and the third exposure time is positively related to: dividing the target histogram value by the sum of the second histogram luminance minimum value and the second histogram width, and then multiplying Take the second exposure time.
在其中一種較佳的實施例中，當增加該第一曝光時間為該第二曝光時間，以作為該第二階段曝光條件，而感測該影像，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度小於該第一直方寬度時，產生一第三曝光時間，以作為一第三階段曝光條件，而感測該影像；其中該第三曝光時間正相關於：將一目標直方值減去該第二直方亮度極小值後，將結果除以該目標直方值，再乘以該第二曝光時間。 In one of the preferred embodiments, when the first exposure time is increased to the second exposure time as the second stage exposure conditions, the image is sensed to generate the second histogram brightness maximum, the When the second histogram brightness minimum value and the second histogram width are smaller than the first histogram width, a third exposure time is generated as a third stage exposure condition, and the image is sensed ; Wherein the third exposure time is positively related to: after subtracting the second histogram brightness minimum value from a target histogram value, dividing the result by the target histogram value, and then multiplying the second exposure time by the target histogram value.
在其中一種較佳的實施例中，當增加該第一曝光時間為該第二曝光時間，以作為該第二階段曝光條件，而感測該影像，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度不小於該第一直方寬度，且該第二直方亮度極大值不大於一目標直方值時，產生一第三曝光時間，以作為一第三階段曝光條件，而感測該影像；其中該第三曝光時間正相關於：將該目標直方值除以該第二直方亮度極大值，再乘以該第二曝光時間。 In one of the preferred embodiments, when the first exposure time is increased to the second exposure time as the second stage exposure conditions, the image is sensed to generate the second histogram brightness maximum, the A third exposure occurs when the second histogram luminance is minimum and the second histogram width, the second histogram width is not less than the first histogram width, and the second histogram luminance maximum is not more than a target histogram value. Time as a third stage exposure condition, and the image is sensed; wherein the third exposure time is positively related to: dividing the target histogram value by the second histogram brightness maximum value, and then multiplying by the second exposure time .
在前述的實施例中，當增加該第一曝光時間為該第二曝光時間，以作為該第二階段曝光條件，而感測該影像，進而產生該第二直方亮 度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度不小於該第一直方寬度，且該第二直方亮度極大值大於一目標直方值時，產生一第三曝光時間，以作為一第三階段曝光條件，而感測該影像；其中該第三曝光時間正相關於：將該目標直方值除以該第二直方亮度極小值與該第二直方寬度的和，再乘以該第二曝光時間。 In the foregoing embodiment, when the first exposure time is increased to the second exposure time as the second stage exposure condition, the image is sensed to generate the second histogram. When the degree maximum value, the second histogram brightness minimum value, and the second histogram width are not less than the first histogram width, and the second histogram brightness maximum value is greater than a target histogram value, A third exposure time is used as a third stage exposure condition to sense the image; wherein the third exposure time is positively related to: dividing the target histogram value by the second histogram brightness minimum value and the second histogram The sum of the widths is then multiplied by the second exposure time.
在其中一種較佳的實施例中，該提供一第一階段曝光條件之步驟，包括：S101：以預設之一前置曝光條件(preceding exposure condition)，感測該影像，以產生一前置直方亮度極大值、一前置直方亮度極小值、與一前置直方寬度；S102：當該前置直方亮度極大值小於一第一預設亮度，且一光源電流尚未增加達到一光源電流上限，增加該前置曝光條件之該光源電流，作為更新之該前置曝光條件，而感測該影像，以產生更新之該前置直方亮度極大值、該前置直方亮度極小值、與該前置直方寬度；S103：重複前述步驟S102，直到該前置直方亮度極大值不小於該第一預設亮度，或該光源電流增加達到該光源電流上限；S104：當增加該光源電流達到該光源電流上限，且該前置直方亮度極大值小於該第一預設亮度，且該曝光時間級距尚未提高達到一曝光時間級距上限，提高該前置曝光條件之一曝光時間級距，作為更新之該前置曝光條件，而感測該影像，以產生更新之該前置直方亮度極大值、該前置直方亮度極小值、與該前置直方寬度；S105：重複前述步驟S104，直到該前置直方亮度極大值不小於該第一預設亮度，或該曝光時間級距提高達到該曝光時間級距上限；S106：當該前置直方亮度極小值大於一第二預設亮度，且該曝光時間級距尚未降低達到一曝光時間級距下限，降低該前置曝光條件之該曝光時間級距，作為更新之該前置曝光條件，而感測該影像，以產生更新之該前置直方亮度極大值、該前置直方亮 度極小值、與該前置直方寬度；S107：重複前述步驟S106，直到該前置直方亮度極小值不大於該第二預設亮度，或該曝光時間級距降低達到該曝光時間級距下限；S108：當降低該曝光時間級距達到該曝光時間級距下限，且該前置直方亮度極小值大於該第二預設亮度，且該光源電流尚未減少達到一光源電流下限，減少該前置曝光條件之該光源電流，作為更新之該前置曝光條件，而感測該影像，以產生更新之該前置直方亮度極大值、該前置直方亮度極小值、與該前置直方寬度；S109：重複前述步驟S108，直到該前置直方亮度極小值不大於該第二預設亮度，或該光源電流減少達到該光源電流下限；以及當前述步驟S103、S105、與S109完成，以更新之該前置曝光條件，作為該第一階段曝光條件。 In one of the preferred embodiments, the step of providing a first-stage exposure condition includes: S101: Sensing the image with a preset exposure condition to generate a preposition The maximum value of the histogram brightness, a minimum value of the front histogram brightness, and a width of the front histogram; S102: When the maximum value of the front histogram brightness is less than a first preset brightness, and a light source current has not increased to reach a light source current upper limit, Increasing the light source current of the front exposure condition as the updated front exposure condition, and sensing the image to generate the updated maximum value of the front histogram brightness, the minimum value of the front histogram brightness, and the front Histogram width; S103: Repeat the previous step S102 until the maximum value of the front histogram brightness is not less than the first preset brightness, or the light source current increases to reach the upper limit of the light source current; S104: When the light source current is increased to reach the upper limit of the light source current , And the maximum value of the front histogram brightness is smaller than the first preset brightness, and the exposure time step has not been increased to reach an upper limit of the exposure time step, increasing the Set an exposure time interval as one of the exposure conditions as the updated front exposure condition, and sense the image to generate the updated maximum value of the front histogram brightness, the minimum value of the front histogram brightness, and the front histogram Width; S105: repeat the foregoing step S104 until the maximum value of the front histogram brightness is not less than the first preset brightness, or the exposure time step is increased to reach the upper limit of the exposure time step; S106: when the front histogram brightness is extremely small The value is greater than a second preset brightness, and the exposure time step has not been lowered to reach a lower limit of the exposure time step. The exposure time step of the pre-exposure condition is reduced as the updated pre-exposure condition. The image to generate the updated maximum value of the front histogram brightness, the front histogram brightness The minimum value of the degree and the front histogram width; S107: repeat the foregoing step S106 until the minimum value of the front histogram brightness is not greater than the second preset brightness, or the exposure time step decreases to reach the lower limit of the exposure time step; S108: When the exposure time step is reduced to reach the lower limit of the exposure time step, and the minimum value of the front histogram brightness is greater than the second preset brightness, and the light source current has not been reduced to reach a lower limit of the light source current, the front exposure is reduced. The light source current of the condition is used as the updated front exposure condition, and the image is sensed to generate the updated maximum value of the front histogram brightness, the minimum value of the front histogram brightness, and the front histogram width; S109: Repeat the foregoing step S108 until the minimum value of the front histogram brightness is not greater than the second preset brightness, or the light source current is reduced to reach the lower limit of the light source current; and when the foregoing steps S103, S105, and S109 are completed, the former is updated The exposure conditions are set as the first-stage exposure conditions.
在其中一種較佳的實施例中，影像感測之曝光時間決定方法較佳地更包含：以該第三階段曝光條件，於一第一時間點，以一感測元件之至少一移動檢查像素感測該影像，以取得該至少一移動檢查像素之至少一第一亮度；以該第三階段曝光條件，於該第一時間點後之一第二時間點，以該至少一移動檢查像素感測該影像，以取得該至少一移動檢查像素之至少一第二亮度；以及根據該至少一第一亮度與該至少一第二亮度，決定一移動穩定度。 In one of the preferred embodiments, the method for determining the exposure time of image sensing preferably further includes: using the third stage exposure condition, at a first time point, at least one moving inspection pixel of a sensing element Sensing the image to obtain at least a first brightness of the at least one moving inspection pixel; using the third stage exposure condition, at a second time point after the first time point, using the at least one moving inspection pixel sense Measuring the image to obtain at least a second brightness of the at least one mobile inspection pixel; and determining a movement stability according to the at least one first brightness and the at least one second brightness.
在前述的實施例中，影像感測之曝光時間決定方法較佳地更包含：根據複數該第一亮度與複數該第二亮度之一絕對差和(sum of absolute difference)，決定該移動穩定度。 In the foregoing embodiment, the method for determining the exposure time for image sensing preferably further includes: determining the movement stability according to a sum of absolute difference between the first brightness and the second brightness. .
在其中一種較佳的實施例中，該第一預設亮度與該第二預設亮度相同，皆為一預設中間亮度。 In a preferred embodiment, the first preset brightness is the same as the second preset brightness, and both are a preset intermediate brightness.
在其中一種較佳的實施例中，影像感測之曝光時間決定方法更包含：根據該第一直方亮度極大值與一目標直方值，決定於該步驟S3中，增加或減少該第一曝光時間。 In one of the preferred embodiments, the method for determining the exposure time of image sensing further includes: determining, in step S3, increasing or decreasing the first exposure according to the first square maximum luminance value and a target histogram value. time.
底下藉由具體實施例詳加說明，當更容易瞭解本發明之目的、技術內容、特點及其所達成之功效。 Detailed descriptions will be provided below through specific embodiments to make it easier to understand the purpose, technical content, features and effects of the present invention.
Hist.Target‧‧‧目標直方值 Hist.Target
Prc.Hist.Max.‧‧‧前置直方亮度極大值 Prc.Hist.Max.
Prc.Hist.Min.‧‧‧前置直方亮度極小值 Prc.Hist.Min.‧‧‧Minimum value of front histogram brightness
S1~S5,S101~S108‧‧‧步驟 S1 ~ S5, S101 ~ S108‧‧‧step
Tint1‧‧‧第一曝光時間 Tint1‧‧‧First exposure time
Tint2‧‧‧第二曝光時間 Tint2‧‧‧Second exposure time
Tint3‧‧‧第三曝光時間 Tint3‧‧‧ Third exposure time
1st Hist.Brt.Max.‧‧‧第一直方亮度極大值 1 st Hist.Brt.Max.
1st Hist.Width‧‧‧第一直方寬度 1 st Hist.Width‧‧‧
1st Pred.Brt.‧‧‧第一預設亮度 1 st Pred.Brt.‧‧‧First preset brightness
2nd Hist.Brt.Max.‧‧‧第二直方亮度極大值 2 nd Hist.Brt.Max.‧‧‧Second histogram brightness maximum
2nd Hist.Brt.Min.‧‧‧第二直方亮度極小值 2 nd Hist.Brt.Min.‧‧‧Minimum value of the second histogram brightness
2nd Hist.Width‧‧‧第二直方寬度 2 nd Hist.Width
2nd Pred.Brt.‧‧‧第二預設亮度 2 nd Pred.Brt.‧‧‧Second preset brightness
〔第1圖〕顯示根據本發明之影像感測之曝光時間決定方法之流程圖；〔第2A-2C圖〕顯示根據本發明之第一個實施例；〔第3圖〕顯示根據本發明之第二個實施例；〔第4圖〕顯示根據本發明之第三個實施例；〔第5圖〕顯示根據本發明之第四個實施例；〔第6圖〕顯示根據本發明之第五個實施例；〔第7圖〕顯示根據本發明之第六個實施例；。 [Figure 1] A flowchart showing a method for determining the exposure time of image sensing according to the present invention; [Figures 2A-2C] showing a first embodiment according to the present invention; [Figure 3] showing a method according to the present invention The second embodiment; [FIG. 4] shows a third embodiment according to the present invention; [FIG. 5] shows a fourth embodiment according to the present invention; [FIG. 6] shows a fifth embodiment according to the present invention [FIG. 7] shows a sixth embodiment according to the present invention;
本發明中的圖式均屬示意，主要意在表示各電路間之耦接關係，以及各訊號波形之間之關係，至於電路、訊號波形與頻率則並未依照比例繪製。 The drawings in the present invention are schematic, and are mainly intended to represent the coupling relationship between various circuits and the relationship between signal waveforms. As for the circuits, signal waveforms and frequencies, they are not drawn to scale.
第1圖顯示根據本發明之影像感測之曝光時間決定方法之流程圖。如圖所示，根據本發明之影像感測之曝光時間決定方法，包含：提供一第一階段曝光條件，其中該第一階段曝光條件，包括一第一曝光時間(S1)；根據該第一階段曝光條件，感測一影像，並根據所感測影像的亮度分布與對應於各亮度之像素數目，產生一直方統計圖(histogram)，且在該直方統計圖中決定一第一直方亮度極大值、一第一直方亮度極小值、與一第一直方寬度，其中該第一直方寬度為該第一直方亮度極大值與該第一直方亮度極小值之間，像素數目超過一數目閾值的亮度之總數(S2)；增加或減少該第一曝光時間為一第二曝光時間，以作為一第二階段曝光條件，而感測該影像，進而產生一第二直方亮度極大值、一第二直方亮度極小值、與一第二直方寬度(S3)；比較該第一直方寬度與該第二直方寬度，並根據比較結果，而決定一第三曝光時間，以作為一第三階段曝光條件(S4)；以及根據該第三階段曝光條件，感測該影像(S5)。 FIG. 1 shows a flowchart of a method for determining an exposure time for image sensing according to the present invention. As shown in the figure, the method for determining the exposure time of image sensing according to the present invention includes: providing a first-stage exposure condition, wherein the first-stage exposure condition includes a first exposure time (S1); according to the first In the stage exposure condition, an image is sensed, and a histogram is generated according to the brightness distribution of the sensed image and the number of pixels corresponding to each brightness, and a first histogram is determined to be extremely large in the histogram. Value, a first square brightness minimum, and a first square width, where the first square width is between the first square brightness maximum and the first square brightness minimum, and the number of pixels exceeds A total number of threshold brightness (S2); increasing or decreasing the first exposure time to a second exposure time as a second stage exposure condition, and sensing the image to generate a second histogram brightness maximum , A second histogram brightness minimum value, and a second histogram width (S3); compare the first histogram width with the second histogram width, and determine a third exposure time based on the comparison result as The third stage of exposure conditions (S4); and a test image according to the third phase of the exposure conditions, the sense (S5).
根據本發明之影像感測之曝光時間決定方法，首先提供第一階段曝光條件，其中第一階段曝光條件包括第一曝光時間。第一曝光時間的決定方式，例如可由一前置流程決定，前置流程將於後詳述。接下來，根據第一階段曝光條件，感測影像，並據以產生一影像亮度之一第一直方圖。從第一直方圖中，取得第一直方亮度極大值、第一直方亮度極小值、與第一直方寬度。接下來，增加或減少第一曝光時間為第二曝光時間，以作為第二階段曝光條件，而感測該影像，並據以產生影像亮度之第二直方圖。從第二直方圖中，取得第二直方亮度極大值、第二直方亮度極小值、與第二直方寬度。接下來，比較第一直方寬度與第二直方寬度，並根據比較結果，而決定第三曝光時間，以作為第三階段曝光條件，感測該影像。 According to the method for determining the exposure time of image sensing according to the present invention, a first-stage exposure condition is first provided, wherein the first-stage exposure condition includes a first exposure time. The method for determining the first exposure time may be determined by, for example, a pre-process, which will be described in detail later. Next, the image is sensed according to the first-stage exposure conditions, and a first histogram of one image brightness is generated accordingly. From the first histogram, the first maximum luminance value, the minimum luminance value, and the first width are obtained. Next, the first exposure time is increased or decreased as the second exposure time as the second stage exposure condition, and the image is sensed to generate a second histogram of the image brightness accordingly. From the second histogram, a second maximum value of the histogram brightness, a second minimum value of the histogram brightness, and a second histogram width are obtained. Next, the first square width and the second histogram width are compared, and a third exposure time is determined according to the comparison result, which is used as a third stage exposure condition to sense the image.
第2A-2C圖顯示根據本發明之第一個實施例。本實施例以實際應用的方式，舉例說明本發明的實施方式。如第2A圖所示，提供感測元件，以感測手指影像。在本實施例中，光源鄰置於感測元件之外側。光源例如但不限於為LED元件，發射光線至手指內部，光線在手指中散射、折射、反射後產生之影像為指紋影像，即以「光手指」(light finger)的方式產生指紋影像。感測元件用以感測該指紋影像，而加以應用，例如驗證身分等。需說明的是，在實際的實施方式中，手指例如可直接或隔著透光物質緊貼感測元件，在本圖中，為方便理解，並未將手指繪製於緊貼感測元件。當然，手指亦可以不緊貼感測元件。感測元件感測該指紋影像後，產生影像亮度之第一直方圖，如第2B圖所示意。 Figures 2A-2C show a first embodiment according to the present invention. This embodiment exemplifies an implementation manner of the present invention in an actual application manner. As shown in FIG. 2A, a sensing element is provided to sense a finger image. In this embodiment, the light source is adjacent to the outside of the sensing element. The light source is, for example, but not limited to, an LED element, which emits light to the inside of the finger. The image generated by the light scattered, refracted, and reflected in the finger is a fingerprint image, that is, a fingerprint image is generated in a "light finger" manner. The sensing element is used for sensing the fingerprint image and applied, such as verifying identity. It should be noted that, in an actual implementation, for example, a finger may be directly attached to the sensing element directly or through a light-transmitting substance. In this figure, for ease of understanding, the finger is not drawn on the sensing element. Of course, the finger may not stick to the sensing element. After the sensing element senses the fingerprint image, a first histogram of image brightness is generated, as shown in FIG. 2B.
需說明的是，第2B圖所示的直方統計圖(histogram)，是用來說明如何從直方圖中，取得直方亮度極大值、直方亮度極小值、與直方寬度的方法，而不限於為第一直方圖、第二直方圖、或第三直方圖。在直方圖中，橫軸代表亮度，縱軸代表像素數目。而從直方圖中，取得直方亮度極大值、直方亮度極小值、與直方寬度的方法，例如先提供一預設的數目閾值，像素數目超過數目閾值的最高亮度，即為直方亮度極大值；像素數目超過數目閾值的最低亮度，即為直方亮度極小值；而像素數目超過數目閾值，且介於直方亮度極小值與直方亮度極大值的每一亮度，即被計算為直方寬度的累計單元。例如，像素數目超過數目閾值，且介於直方亮度極小值與直方亮度極大值的亮度，無論像素數目超過數目閾值多少數目，都被計以一累計單元；而直方寬度即累計此累計單元的結果；也就是說，所謂的直方寬度，係指直方亮度極大值與直方亮度極小值之間，像素數目超過數目閾值的亮度之總數。而亮度的定義，為像素從最暗到最亮的數位計 量方式，舉例而言，8位元可以將像素的亮度分為0到255之256級亮度。此外，在直方圖中，例如可預設一亮度閾值，低於此亮度閾值的亮度，不予列入計算，即不被用以取得直方亮度極大值、直方亮度極小值、與直方寬度。第2C圖舉例顯示亮度與曝光時間的關係，在實際的應用上，亮度與曝光時間可以視為線性關係，以方便利用例如但不限於外插法、內插法等線性方式計算。 It should be noted that the histogram shown in Figure 2B is used to explain how to obtain the maximum value of the histogram brightness, the minimum value of the histogram brightness, and the histogram width from the histogram, and is not limited to the first Histogram, second histogram, or third histogram. In the histogram, the horizontal axis represents brightness and the vertical axis represents the number of pixels. The method of obtaining the maximum value of the histogram brightness, the minimum value of the histogram brightness, and the width of the histogram from the histogram, for example, first provides a preset number threshold, and the maximum brightness of the number of pixels exceeding the number threshold is the maximum value of the histogram brightness; The lowest brightness whose number exceeds the threshold is the minimum value of the histogram brightness, and each brightness whose number of pixels exceeds the threshold and which is between the minimum value of the histogram brightness and the maximum value of the histogram brightness is calculated as a cumulative unit of the histogram width. For example, the brightness of the number of pixels exceeding the number threshold and between the minimum value of the histogram brightness and the maximum value of the histogram brightness is counted as an accumulation unit regardless of the number of pixels exceeding the number threshold; and the histogram width is the result of accumulating this accumulation unit In other words, the so-called histogram width refers to the total number of brightnesses whose number of pixels exceeds the threshold between the maximum value of the histogram brightness and the minimum value of the histogram brightness. The definition of brightness is a digital meter from the darkest to the brightest pixel. For example, 8-bit can divide the brightness of a pixel into 256 levels of brightness from 0 to 255. In addition, in the histogram, for example, a brightness threshold can be preset, and brightness lower than this brightness threshold is not included in the calculation, that is, it is not used to obtain the maximum value of the histogram brightness, the minimum value of the histogram brightness, and the width of the histogram. FIG. 2C shows the relationship between the brightness and the exposure time by way of example. In practical applications, the brightness and the exposure time can be regarded as a linear relationship, so as to facilitate the calculation using linear methods such as, but not limited to, extrapolation and interpolation.
根據本發明，例如利用第2A圖所示的裝置與方法，根據第一曝光時間與第二曝光時間，取得第一直方圖與第二直方圖，進而得到第一直方寬度與第二直方寬度，再由第一直方寬度與第二直方寬度，得到第三曝光時間。接著根據第三曝光時間，感測指紋影像，以得到較佳的指紋影像。 According to the present invention, for example, using the apparatus and method shown in FIG. 2A, the first histogram and the second histogram are obtained according to the first exposure time and the second exposure time, and then the first histogram width and the second histogram are obtained. Width, and then a third exposure time is obtained from the first rectangular width and the second rectangular width. Then, the fingerprint image is sensed according to the third exposure time to obtain a better fingerprint image.
第3圖顯示根據本發明之第二個實施例。本實施例舉例說明在步驟S3中，如何決定增加或減少第一曝光時間。如圖所示，當該第一直方亮度極大值1st Histogram Brightness Maximum(1st Hist.Brt.Max.)小於一目標直方值Histogram Target(Hist.Target)，決定於該步驟S3中，增加該第一曝光時間，而產生該第二曝光時間。也就是說，當該第一直方亮度極大值1st Hist.Brt.Max.小於該目標直方值Hist.Target，則判斷為第一次影像感測的結果所產生的影像亮度資訊中，亮度數目超過數目閾值的最高亮度太低，需要以增加曝光時間來提高最高亮度。 Figure 3 shows a second embodiment according to the invention. This embodiment illustrates how to decide to increase or decrease the first exposure time in step S3. As shown in the figure, when the first square brightness maximum value 1 st Histogram Brightness Maximum (1 st Hist.Brt.Max.) Is smaller than a target histogram value Histogram Target (Hist.Target), it is determined in step S3 that The first exposure time results in the second exposure time. In other words, when the maximum value of the first square luminance 1 st Hist.Brt.Max. Is smaller than the target histogram Hist.Target, it is determined that among the image brightness information generated by the result of the first image sensing, the brightness The maximum brightness of the number exceeding the number threshold is too low, and the maximum brightness needs to be increased by increasing the exposure time.
另一方面，當該第一直方亮度極大值1st Hist.Brt.Max.不小於該目標直方值Hist.Target，則決定於該步驟S3中，減少該第一曝光時間，而產生該第二曝光時間Tint2。也就是說，當該第一直方亮度極大值1st Hist.Brt.Max.不小於該目標直方值Hist.Target，則判斷為第一次影像感測的結果 所產生的影像亮度資訊中，亮度數目超過數目閾值的最高亮度太高，需要以減少曝光時間來降低最高亮度。至於在第二次影像感測中，第二階段曝光條件的第二曝光時間Tint2係由第一次影像感測中之第一階段曝光條件的第一曝光時間Tint1增加或減少多少時間而得到，有各種不同的決定方式，其中之一例如但不限於為增加或減少一預設單位時間。 On the other hand, when the first square luminance maximum value 1 st Hist.Brt.Max. Is not less than the target histogram value Hist.Target, it is determined in step S3 to reduce the first exposure time to generate the first Second exposure time Tint2. That is to say, when the maximum value of the first square luminance 1 st Hist.Brt.Max. Is not less than the target histogram value Hist.Target, it is determined that the image luminance information generated by the result of the first image sensing, The maximum brightness exceeding the number threshold is too high. It is necessary to reduce the maximum brightness by reducing the exposure time. As for the second image sensing, the second exposure time Tint2 of the second-stage exposure condition is obtained by increasing or decreasing the first exposure time Tint1 of the first-stage exposure condition in the first image sensing, There are various determination methods, one of which is, for example, but not limited to, increasing or decreasing a predetermined unit time.
第4圖顯示根據本發明之第三個實施例。如圖所示，當在步驟S3中，當決定減少該第一曝光時間Tint1為該第二曝光時間Tint2，以作為該第二階段曝光條件，而執行第二次影像感測，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度2nd Histogram Width(2nd Hist.Width)不小於該第一直方寬度1st Hist.Width時，產生一第三曝光時間Tint3，以作為一第三階段曝光條件，而感測該影像；其中該第三曝光時間Tint 3正相關於(例如但不限於等於)：將一目標直方值Hist.Target減去該第二直方亮度極小值2nd Hist.Brt.Min.後，將結果除以該目標直方值Hist.Target，再乘以該第二曝光時間Tint2。也就是說，例如在第一次感測影像的結果中，該第一直方亮度極大值1st Hist.Brt.Max.不小於該目標直方值Hist.Target，則判斷為影像感測的結果所產生的影像亮度資訊中，數量超過數量閾值的最高亮度太高，需要以減少曝光時間來降低亮度；因此，先減少第一曝光時間Tint1，得到第二曝光時間Tint2，並以其作為第二階段曝光條件，而據以執行第二次影像感測，以產生感測影像結果。在第二次影像感測中，該第二直方寬度2nd Hist.Width不小於該第一直方寬度1st Hist.Width時，則再進一步以在步驟S3中，將目標直方值Hist.Target減去該第二直方亮度極小值2nd Hist.Brt.Min.後，將結果除以該 目標直方值Hist.Target，再乘以該第二曝光時間Tint2，而得到第三曝光時間Tint3。 Fig. 4 shows a third embodiment according to the present invention. As shown in the figure, in step S3, when it is decided to reduce the first exposure time Tint1 to the second exposure time Tint2 as the second stage exposure condition, a second image sensing is performed, and then the first Two histogram brightness maximums, the second histogram brightness minimum, and the second histogram width, and the second histogram width 2 nd Histogram Width (2 nd Hist.Width) is not less than the first square width 1 st Hist. When Width, a third exposure time Tint3 is generated as a third stage exposure condition to sense the image; wherein the third exposure time Tint 3 is positively related to (for example, but not limited to): a target histogram value Hist.Target subtracts the second histogram brightness minimum value 2 nd Hist.Brt.Min., Divides the result by the target histogram value Hist.Target, and then multiplies the second exposure time Tint2. That is, for example, in the result of the first sensing image, the first cuboid luminance maximum value 1 st Hist.Brt.Max. Is not less than the target histogram Hist.Target, it is determined as the result of image sensing. In the generated image brightness information, the maximum brightness exceeding the quantity threshold is too high, and the brightness needs to be reduced by reducing the exposure time; therefore, the first exposure time Tint1 is reduced to obtain the second exposure time Tint2, and this is used as the second Stage exposure conditions, and a second image sensing is performed to generate a sensing image result. In the second image sensing, when the second histogram width 2 nd Hist.Width is not less than the first histogram width 1 st Hist.Width, then in step S3, the target histogram value Hist.Target is further After subtracting the second histogram brightness minimum value 2 nd Hist.Brt.Min., The result is divided by the target histogram value Hist.Target, and then multiplied by the second exposure time Tint2 to obtain a third exposure time Tint3.
繼續參閱第4圖，如圖所示，當在步驟S3中，當決定減少該第一曝光時間Tint1為該第二曝光時間Tint2，以作為該第二階段曝光條件，而執行第二次影像感測，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度2nd Histogram Width(2nd Hist.Width)小於該第一直方寬度1st Hist.Width，且該第二直方亮度極大值2nd Hist.Max.不大於該目標直方值Hist.Target時，產生一第三曝光時間Tint3，以作為第三階段曝光條件，而感測該影像；其中該第三曝光時間Tint 3正相關於(例如但不限於等於)：將目標直方值Hist.Target除以該第二直方亮度極大值2nd Hist.Brt.Max.後，將結果再乘以該第二曝光時間Tint2。也就是說，例如在第一次感測影像的結果中，該第一直方亮度極大值1st Hist.Brt.Max.不小於該目標直方值Hist.Target，則判斷為影像感測的結果所產生的影像亮度資訊中，數量超過數量閾值的最高亮度太高，需要以減少曝光時間來降低亮度；因此，先減少第一曝光時間Tint1，得到第二曝光時間Tint2，並以其作為第二階段曝光條件，而據以執行第二次影像感測，以產生感測影像結果。在第二次影像感測中，該第二直方寬度2nd Hist.Width小於該第一直方寬度1st Hist.Width時，且該第二直方亮度極大值2nd Hist.Brt.Max.不大於該目標直方值Hist.Target時，則再進一步以在步驟S3中，將目標直方值Hist.Target除以該第二直方亮度極大值2nd Hist.Brt.Max.後，將結果乘以該第二曝光時間Tint2，而得到第三曝光時間Tint3。 Continuing to refer to FIG. 4, as shown in the figure, when it is determined in step S3 that the first exposure time Tint1 is reduced to the second exposure time Tint2 as the second stage exposure condition, the second image sensing is performed. Measurement, further generating the second histogram luminance maximum value, the second histogram luminance minimum value, and the second histogram width, and the second histogram width 2 nd Histogram Width (2 nd Hist.Width) is smaller than the first histogram When the width is 1 st Hist.Width and the maximum value of the second histogram brightness is 2 nd Hist.Max. Is not greater than the target histogram value Hist.Target, a third exposure time Tint3 is generated as the third stage exposure condition. Measuring the image; wherein the third exposure time Tint 3 is positively related (for example, but not limited to equal to): after dividing the target histogram value Hist.Target by the second histogram brightness maximum value 2 nd Hist.Brt.Max., The result is then multiplied by the second exposure time Tint2. That is, for example, in the result of the first sensing image, the first cuboid luminance maximum value 1 st Hist.Brt.Max. Is not less than the target histogram Hist.Target, it is determined as the result of image sensing. In the generated image brightness information, the maximum brightness exceeding the quantity threshold is too high, and the brightness needs to be reduced by reducing the exposure time; therefore, the first exposure time Tint1 is reduced to obtain the second exposure time Tint2, and this is used as the second Stage exposure conditions, and a second image sensing is performed to generate a sensing image result. In the second image sensing, when the second histogram width 2 nd Hist.Width is smaller than the first histogram width 1 st Hist.Width, and the second histogram luminance maximum value 2 nd Hist.Brt.Max. If it is greater than the target histogram Hist.Target, then in step S3, the target histogram Hist.Target is divided by the second histogram luminance maximum 2nd Hist.Brt.Max., And the result is multiplied by the The second exposure time Tint2, and the third exposure time Tint3 is obtained.
繼續參閱第4圖，如圖所示，當在步驟S3中，當決定減少該第一曝光時間Tint1為該第二曝光時間Tint2，以作為該第二階段曝光條件， 而執行第二次影像感測，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度2nd Hist.Width小於該第一直方寬度1st Hist.Width，且該第二直方亮度極大值2nd Hist.Max.大於該目標直方值Hist.Target時，產生一第三曝光時間Tint3，以作為第三階段曝光條件，而感測該影像；其中該第三曝光時間Tint 3正相關於(例如但不限於等於)：將目標直方值Hist.Target除以該第二直方亮度極小值2nd Hist.Brt.Min.與該第二直方寬度2nd Hist.Width的和，將結果再乘以該第二曝光時間Tint2。也就是說，例如在第一次感測影像的結果中，該第一直方亮度極大值1st Hist.Brt.Max.不小於該目標直方值Hist.Target，則判斷為影像感測的結果所產生的影像亮度資訊中，數量超過數量閾值的最高亮度太高，需要以減少曝光時間來降低亮度；因此，先減少第一曝光時間Tint1，得到第二曝光時間Tint2，並以其作為第二階段曝光條件，而據以執行第二次影像感測，以產生感測影像結果。在第二次影像感測中，該第二直方寬度2nd Hist.Width小於該第一直方寬度1st Hist.Width時，且該第二直方亮度極大值2nd Hist.Max.大於該目標直方值Hist.Target時，則再進一步以在步驟S3中，將目標直方值Hist.Target除以該第二直方亮度極小值2nd Hist.Brt.Min.與該第二直方寬度2nd Hist.Width的和，將結果再乘以該第二曝光時間Tint2，而得到第三曝光時間Tint3。 Continuing to refer to FIG. 4, as shown in the figure, when it is determined in step S3 that the first exposure time Tint1 is reduced to the second exposure time Tint2 as the second-stage exposure conditions, the second image sensing is performed. Measurement, further generating the second histogram luminance maximum value, the second histogram luminance minimum value, and the second histogram width, and the second histogram width 2 nd Hist.Width is smaller than the first histogram width 1 st Hist.Width And when the second histogram luminance maximum value 2 nd Hist.Max. Is greater than the target histogram Hist.Target, a third exposure time Tint3 is generated as a third stage exposure condition to sense the image; wherein the first The three exposure times Tint 3 are positively related (for example, but not limited to being equal to): dividing the target histogram Hist.Target by the second histogram brightness minimum 2 nd Hist.Brt.Min. And the second histogram width 2 nd Hist. The sum of the Width and the result is multiplied by the second exposure time Tint2. That is, for example, in the result of the first sensing image, the first cuboid luminance maximum value 1 st Hist.Brt.Max. Is not less than the target histogram Hist.Target, it is determined as the result of image sensing. In the generated image brightness information, the maximum brightness exceeding the quantity threshold is too high, and the brightness needs to be reduced by reducing the exposure time; therefore, the first exposure time Tint1 is reduced to obtain the second exposure time Tint2, and this is used as the second Stage exposure conditions, and a second image sensing is performed to generate a sensing image result. In the second image sensing, when the second histogram width 2 nd Hist.Width is smaller than the first histogram width 1 st Hist.Width, and the second histogram luminance maximum value 2 nd Hist.Max. Is larger than the target When the histogram value is Hist.Target, then in step S3, the target histogram value Hist.Target is divided by the second histogram luminance minimum value 2 nd Hist.Brt.Min. And the second histogram width 2 nd Hist. The sum of the widths is multiplied by the result by the second exposure time Tint2 to obtain a third exposure time Tint3.
第5圖顯示根據本發明之第四個實施例。如圖所示，當在步驟S3中，當決定增加該第一曝光時間Tint1為該第二曝光時間Tint2，以作為該第二階段曝光條件，而執行第二次影像感測，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度2nd Histogram Width(2nd Hist.Width)小於該第一直方寬度1st Hist.Width 時，產生一第三曝光時間Tint3，以作為一第三階段曝光條件，而感測該影像；其中該第三曝光時間Tint 3正相關於(例如但不限於等於)：將目標直方值Hist.Target減去該第二直方亮度極小值2nd Hist.Min.後，將結果除以該目標直方值Hist.Target，再乘以該第二曝光時間Tint2。也就是說，例如在第一次感測影像的結果中，該第一直方亮度極大值1st Hist.Brt.Max.小於該目標直方值Hist.Target，則判斷為影像感測的結果所產生的影像亮度資訊中，數量超過數量閾值的最高亮度太低，需要以增加曝光時間來提高亮度；因此，先增加第一曝光時間Tint1，得到第二曝光時間Tint2，並以其作為第二階段曝光條件，而據以執行第二次影像感測，以產生感測影像結果。在第二次影像感測中，該第二直方寬度2nd Hist.Width小於該第一直方寬度1st Hist.Width時，則再進一步以在步驟S3中，將目標直方值Hist.Target減去該第二直方亮度極小值2nd Hist.Brt.Min.後，將結果除以該目標直方值Hist.Target，再乘以該第二曝光時間Tint2，而得到第三曝光時間Tint3。 Fig. 5 shows a fourth embodiment according to the present invention. As shown in the figure, in step S3, when it is decided to increase the first exposure time Tint1 to the second exposure time Tint2 as the second-stage exposure conditions, a second image sensing is performed, and then the first Two histogram brightness maxima, the second histogram brightness minima, and the second histogram width, and the second histogram width 2 nd Histogram Width (2 nd Hist.Width) is less than the first histogram width 1 st Hist.Width When a third exposure time Tint3 is generated as a third stage exposure condition, and the image is sensed; wherein the third exposure time Tint 3 is positively related (for example but not limited to equal): the target histogram value Hist. After subtracting the second histogram brightness minimum value 2 nd Hist.Min. From the Target, the result is divided by the target histogram Hist.Target, and then multiplied by the second exposure time Tint2. That is, for example, in the result of the first sensing image, the first cuboid brightness maximum value 1 st Hist.Brt.Max. Is smaller than the target histogram value Hist.Target, it is determined as the result of image sensing. In the generated image brightness information, the maximum brightness exceeding the quantity threshold is too low, and the brightness needs to be increased by increasing the exposure time; therefore, first increase the first exposure time Tint1 to obtain the second exposure time Tint2, and use it as the second stage Exposure conditions, and based on this, a second image sensing is performed to generate a sensing image result. In the second image sensing, when the second histogram width 2 nd Hist.Width is smaller than the first histogram width 1 st Hist.Width, the target histogram value Hist.Target is further reduced in step S3. After removing the second histogram luminance minimum value 2 nd Hist.Brt.Min., The result is divided by the target histogram value Hist.Target, and then multiplied by the second exposure time Tint2 to obtain a third exposure time Tint3.
繼續參閱第5圖，如圖所示，當在步驟S3中，當決定增加該第一曝光時間Tint1為該第二曝光時間Tint2，以作為該第二階段曝光條件，而執行第二次影像感測，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度2nd Histogram Width(2nd Hist.Width)不小於該第一直方寬度1st Hist.Width，且該第二直方亮度極大值2nd Hist.Brt.Max.不大於該目標直方值Hist.Target時，產生第三曝光時間Tint3，以作為第三階段曝光條件，而感測該影像；其中該第三曝光時間Tint 3正相關於(例如但不限於等於)：將目標直方值Hist.Target除以該第二直方亮度極大值2nd Hist.Brt.Max.後，將結果再乘以該第二曝光時間Tint2。也就是說，例如在第一次感測影像的結果中，該第一直方亮度極大值1st Hist.Brt.Max.小於該目標直方值Hist.Target，則判斷為影像感測的結果所產生的影像亮度資訊中，數量超過數量閾值的最高亮度太低，需要以增加曝光時間來提高亮度；因此，先增加第一曝光時間Tint1，得到第二曝光時間Tint2，並以其作為第二階段曝光條件，而據以執行第二次影像感測，以產生感測影像結果。在第二次影像感測中，該第二直方寬度2nd Hist.Width不小於該第一直方寬度1st Hist.Width時，則再進一步以在步驟S3中，將目標直方值Hist.Target除以該第二直方亮度極大值2nd Hist.Brt.Max.後，將結果乘以該第二曝光時間Tint2，而得到第三曝光時間Tint3。 Continuing to refer to FIG. 5, as shown in the figure, when it is determined in step S3 that the first exposure time Tint1 is increased to the second exposure time Tint2 as the second stage exposure condition, the second image sensing is performed. Measurement, further generating the second histogram luminance maximum value, the second histogram luminance minimum value, and the second histogram width, and the second histogram width 2 nd Histogram Width (2 nd Hist.Width) is not less than the first constant When the square width is 1 st Hist.Width and the second histogram brightness maximum value 2 nd Hist.Brt.Max. Is not greater than the target histogram value Hist.Target, a third exposure time Tint3 is generated as the third stage exposure conditions, And sensing the image; wherein the third exposure time Tint 3 is positively related (for example, but not limited to being equal to): after dividing the target histogram Hist.Target by the second histogram luminance maximum 2 nd Hist.Brt.Max. , And then multiply the result by the second exposure time Tint2. That is, for example, in the result of the first sensing image, the first cuboid brightness maximum value 1 st Hist.Brt.Max. Is smaller than the target histogram value Hist.Target, it is determined as the result of image sensing. In the generated image brightness information, the maximum brightness exceeding the quantity threshold is too low, and the brightness needs to be increased by increasing the exposure time; therefore, first increase the first exposure time Tint1 to obtain the second exposure time Tint2, and use it as the second stage Exposure conditions, and based on this, a second image sensing is performed to generate a sensing image result. In the second image sensing, when the second histogram width 2 nd Hist.Width is not less than the first histogram width 1 st Hist.Width, then in step S3, the target histogram value Hist.Target is further After dividing by the second histogram luminance maximum value 2 nd Hist.Brt.Max., The result is multiplied by the second exposure time Tint2 to obtain a third exposure time Tint3.
繼續參閱第5圖，如圖所示，當在步驟S3中，當決定增加該第一曝光時間Tint1為該第二曝光時間Tint2，以作為該第二階段曝光條件，而執行第二次影像感測，進而產生該第二直方亮度極大值、該第二直方亮度極小值、與該第二直方寬度，且該第二直方寬度2nd Hist.Width不小於該第一直方寬度1st Hist.Width，且該第二直方亮度極大值2nd Hist.Brt.Max.大於該目標直方值Hist.Target時，產生一第三曝光時間Tint3，以作為第三階段曝光條件，而感測該影像；其中該第三曝光時間Tint 3正相關於(例如但不限於等於)：將目標直方值Hist.Target除以該第二直方亮度極小值2nd Hist.Brt.Min.與該第二直方寬度2nd Hist.Width的和，將結果再乘以該第二曝光時間Tint2。也就是說，例如在第一次感測影像的結果中，該第一直方亮度極大值1st Hist.Brt.Max.小於該目標直方值Hist.Target，則判斷為影像感測的結果所產生的影像亮度資訊中，數量超過數量閾值的最高亮度太低，需要以增加曝光時間來提高亮度；因此，先增加第一曝光時間Tint1，得到第二曝光時間Tint2，並以其作為第二階段曝光條件，而據以執行第二次影像感測，以產生感測影像結果。在第二次影像感測中，該第二直方寬度2nd Hist.Width 不小於該第一直方寬度1st Hist.Width時，則再進一步以在步驟S3中，將目標直方值Hist.Target除以該第二直方亮度極小值2nd Hist.Brt.Min.與該第二直方寬度2nd Hist.Width的和，將結果再乘以該第二曝光時間Tint2，而得到第三曝光時間Tint3。 Continuing to refer to FIG. 5, as shown in the figure, when it is determined in step S3 that the first exposure time Tint1 is increased to the second exposure time Tint2 as the second stage exposure condition, the second image sensing is performed. Measurement, and then generate the second histogram brightness maximum value, the second histogram brightness minimum value, and the second histogram width, and the second histogram width 2 nd Hist.Width is not less than the first square width 1 st Hist. Width, and when the second histogram luminance maximum value 2 nd Hist.Brt.Max. Is greater than the target histogram Hist.Target, a third exposure time Tint3 is generated as a third stage exposure condition to sense the image; Wherein the third exposure time Tint 3 is positively related to (for example, but not limited to being equal to): dividing the target histogram Hist.Target by the second histogram brightness minimum 2 nd Hist.Brt.Min. And the second histogram width 2 The sum of nd Hist.Width, and then multiply the result by the second exposure time Tint2. That is, for example, in the result of the first sensing image, the first cuboid brightness maximum value 1 st Hist.Brt.Max. Is smaller than the target histogram value Hist.Target, it is determined as the result of image sensing. In the generated image brightness information, the maximum brightness exceeding the quantity threshold is too low, and the brightness needs to be increased by increasing the exposure time; therefore, first increase the first exposure time Tint1 to obtain the second exposure time Tint2, and use it as the second stage Exposure conditions, and based on this, a second image sensing is performed to generate a sensing image result. In the second image sensing, when the second histogram width 2 nd Hist.Width is not less than the first histogram width 1 st Hist.Width, then in step S3, the target histogram value Hist.Target is further Divide the sum of the second histogram brightness minimum 2 nd Hist.Brt.Min. And the second histogram width 2 nd Hist.Width, and then multiply the result by the second exposure time Tint2 to obtain a third exposure time Tint3 .
第6圖顯示根據本發明之第五個實施例。本實施例舉例說明前置流程如何決定第一曝光時間。如圖所示，提供第一階段曝光條件中的第一曝光時間之步驟，包括：S101：以預設之一前置曝光條件(preceding exposure condition)，感測該影像，以產生一前置直方亮度極大值Proceeding Hist.Brt.Max.(Prc.Hist.Brt.Max.)、一前置直方亮度極小值Proceeding Hist.Brt.Min.(Prc.Hist.Brt.Min.)、與一前置直方寬度；S102：當該前置直方亮度極大值Prc.Hist.Brt.Max.小於一第一預設亮度1st Predetermined Brightness(1st Pred.Brt.)，且一光源電流尚未增加達到一光源電流上限，增加該前置曝光條件之該光源電流，作為更新之該前置曝光條件，而感測該影像，以產生更新之該前置直方亮度極大值Prc.Hist.Brt.Max.、該前置直方亮度極小值、與該前置直方寬度；S103：重複前述步驟S102，直到該前置直方亮度極大值Prc.Hist.Brt.Max.不小於該第一預設亮度1st Pred.Brt.，或該光源電流增加達到該光源電流上限；S104：當增加該光源電流達到該光源電流上限，且該前置直方亮度極大值Prc.Hist.Brt.Max.小於該第一預設亮度1st Pred.Brt.，且該曝光時間級距尚未提高達到一曝光時間級距上限，提高該前置曝光條件之一曝光時間級距，作為更新之該前置曝光條件，而感測該影像，以產生更 新之該前置直方亮度極大值Prc.Hist.Brt.Max.、該前置直方亮度極小值、與該前置直方寬度；S105：重複前述步驟S104，直到該前置直方亮度極大值Prc.Hist.Brt.Max.不小於該第一預設亮度1st Pred.Brt.，或該曝光時間級距提高達到該曝光時間級距上限；S106：當該前置直方亮度極小值Prc.Hist.Brt.Min.大於一第二預設亮度2nd Pred.Brt.，且該曝光時間級距尚未降低達到一曝光時間級距下限，降低該前置曝光條件之該曝光時間級距，作為更新之該前置曝光條件，而感測該影像，以產生更新之該前置直方亮度極大值Prc.Hist.Brt.Max.、該前置直方亮度極小值Prc.Hist.Brt.Min.、與該前置直方寬度；S107：重複前述步驟S106，直到該前置直方亮度極小值Prc.Hist.Brt.Min.不大於該第二預設亮度2nd Pred.Brt.，或該曝光時間級距降低達到該曝光時間級距下限；S108：當降低該曝光時間級距達到該曝光時間級距下限，且該前置直方亮度極小值Prc.Hist.Brt.Min.大於該第二預設亮度2nd Pred.Brt.，且該光源電流尚未減少達到一光源電流下限，減少該前置曝光條件之該光源電流，作為更新之該前置曝光條件，而感測該影像，以產生更新之該前置直方亮度極大值Prc.Hist.Brt.Max.、該前置直方亮度極小值Prc.Hist.Brt.Min.、與該前置直方寬度；S109：重複前述步驟S108，直到該前置直方亮度極小值Prc.Hist.Brt.Min.不大於該第二預設亮度2nd Pred.Brt.，或該光源電流減少達到該光源電流下限；以及 當前述步驟S103、S105、與S109完成，以更新之該前置曝光條件，作為該第一階段曝光條件。 Fig. 6 shows a fifth embodiment according to the present invention. This embodiment illustrates how the pre-process determines the first exposure time. As shown in the figure, the step of providing a first exposure time in the first-stage exposure conditions includes: S101: sensing the image with a preset exposure condition to generate a front histogram Proceeding Hist.Brt.Max. (Prc.Hist.Brt.Max.), Proceeding Hist.Brt.Min. (Prc.Hist.Brt.Min.) Histogram width; S102: When the pre-historical brightness maximum value Prc.Hist.Brt.Max. Is less than a first preset brightness 1 st Predetermined Brightness (1 st Pred.Brt.), And a light source current has not increased to reach a light source Current limit, increasing the light source current of the front exposure condition as the updated front exposure condition, and sensing the image to generate an updated maximum value of the front histogram brightness Prc.Hist.Brt.Max., The The minimum value of the front histogram brightness and the width of the front histogram; S103: Repeat the foregoing step S102 until the maximum value of the front histogram brightness Prc.Hist.Brt.Max. Is not less than the first preset brightness 1 st Pred.Brt ., Or the light source current is increased to reach the upper limit of the light source current; S104: when increased Light source current reaches the current limit, and the maximum value of front luminance histogram Prc.Hist.Brt.Max. Less than the first predetermined brightness 1 st Pred.Brt., From the stage and the exposure time has not yet reached an exposure time increase Upper limit of the level, increasing the exposure time level of one of the front exposure conditions as the updated front exposure condition, and sensing the image to generate an updated maximum value of the front histogram brightness Prc.Hist.Brt.Max . The minimum value of the front histogram brightness and the width of the front histogram; S105: Repeat the foregoing step S104 until the maximum value of the front histogram brightness Prc.Hist.Brt.Max. Is not less than the first preset brightness 1 st Pred.Brt., Or the exposure time step is increased to reach the upper limit of the exposure time step; S106: when the pre-historical brightness minimum value Prc.Hist.Brt.Min. Is greater than a second preset brightness 2 nd Pred.Brt And the exposure time step has not been reduced to reach a lower limit of the exposure time step, the exposure time step of the pre-exposure condition is lowered as the updated pre-exposure condition, and the image is sensed to generate an updated The front histogram brightness maxima Prc.Hist.Brt.Ma x. The minimum value of the front histogram brightness Prc.Hist.Brt.Min. and the width of the front histogram brightness; S107: Repeat the foregoing step S106 until the minimum value of the front histogram brightness Prc.Hist.Brt.Min. does not Greater than the second preset brightness 2nd Pred.Brt., Or the exposure time step is reduced to reach the lower limit of the exposure time step; S108: when the exposure time step is reduced to reach the lower limit of the exposure time step, and the front histogram is The minimum brightness value Prc.Hist.Brt.Min. Is greater than the second preset brightness 2nd Pred.Brt., And the light source current has not been reduced to reach a lower limit of the light source current, and the light source current of the front exposure condition is reduced as an update The pre-exposure condition, and the image is sensed to generate the updated pre-historical luminance maximum value Prc.Hist.Brt.Max., The pre-historical luminance minimum value Prc.Hist.Brt.Min., And the Front histogram width; S109: Repeat the foregoing step S108 until the minimum value of the front histogram brightness Prc.Hist.Brt.Min. Is not greater than the second preset brightness 2nd Pred.Brt., Or the light source current is reduced to reach the light source Lower current limit; and when the foregoing steps S103, S105, and S109 are completed, The new front exposure condition is used as the first-stage exposure condition.
其中，光源電流指供應一光源的電流，該光源用以發射光線照亮例如但不限於前述第一個實施例中的手指。而光源例如但不限於為前述LED元件。如第6圖所示，前置流程旨在提供第一階段曝光條件，包含光源電流與第一曝光時間。前置流程的目標，在於使感測影像所取得之影像亮度直方圖中，前置直方亮度極大值Prc.Hist.Brt.Max.達到第一預設亮度1st Pred.Brt.，且前置直方亮度極小值Prc.Hist.Brt.Min.不大於第二預設亮度2nd Pred.Brt.。其中，曝光時間級距調整的幅度相較於前述該第一曝光時間增加/減少為該第二曝光時間高，例如但不限於2倍到10倍或以上的幅度。 Wherein, the light source current refers to a current that supplies a light source for emitting light to illuminate, for example, but not limited to, the finger in the first embodiment. The light source is, for example, but not limited to, the aforementioned LED element. As shown in FIG. 6, the pre-process aims to provide the first-stage exposure conditions, including the light source current and the first exposure time. The goal of the pre-process is to make the pre-historical luminance maximum value Prc.Hist.Brt.Max. Reach the first preset brightness 1 st Pred.Brt. The minimum value of histogram brightness Prc.Hist.Brt.Min. Is not greater than the second preset brightness 2nd Pred.Brt. The amplitude of the exposure time step adjustment is higher than the aforementioned first exposure time by increasing / decreasing the second exposure time, such as, but not limited to, a range of 2 times to 10 times or more.
第7圖顯示根據本發明之第六個實施例，本實施例旨在說明，根據本發明，影像感測之曝光時間決定方法，可更包含：以第三階段曝光條件，於第一時間點，以一感測元件之至少一移動檢查像素感測該影像，以取得該至少一移動檢查像素之至少一第一亮度；以該第三階段曝光條件，於該第一時間點後之一第二時間點，以該至少一移動檢查像素感測該影像，以取得該至少一移動檢查像素之至少一第二亮度；以及根據該至少一第一亮度與該至少一第二亮度，決定一移動穩定度。也就是說，在感測元件中，選擇至少一個移動檢查像素；如第7圖所示，在本實施例中，選擇n個複數移動檢查像素，於第一時間點，以該第三階段曝光條件，感測該影像以取得這n個複數移動檢查像素的亮度，也就是n個第一亮度；接著，在之後的第二時間點，同樣的以該第三階段曝光條件，感測該影像以取得這n個複數移動檢查像素的亮度，也就是n個第二亮度；接著，對應比較該些n個第一亮度與n個第二亮度，而得到移動穩定度的相關資訊，而決定該 移動穩定度。可以設定一移動穩定度閾值，當移動穩定度低於此移動穩定度閾值，例如決定以該第三階段曝光條件，感測該影像；當移動穩定度不低於此移動穩定度閾值，例如決定回到步驟S1或步驟101，重新尋求該第三階段曝光條件。 FIG. 7 shows a sixth embodiment of the present invention. This embodiment is intended to illustrate that according to the present invention, the method for determining the exposure time of image sensing may further include: using the third stage exposure conditions at the first time point. , Sensing the image with at least one moving inspection pixel of a sensing element to obtain at least a first brightness of the at least one moving inspection pixel; and using the third stage exposure condition, one after the first time point. At two points in time, sensing the image with the at least one mobile inspection pixel to obtain at least a second brightness of the at least one mobile inspection pixel; and determining a movement according to the at least one first brightness and the at least one second brightness stability. That is, in the sensing element, at least one moving inspection pixel is selected. As shown in FIG. 7, in this embodiment, n complex moving inspection pixels are selected, and the third stage is exposed at the first time point. Condition, the image is sensed to obtain the brightness of the n plurality of mobile inspection pixels, that is, the n first brightnesses; then, at the second time point thereafter, the image is also sensed under the third-stage exposure conditions In order to obtain the brightness of the n complex mobile inspection pixels, that is, the n second brightnesses; then, the n first brightnesses and the n second brightnesses are compared correspondingly to obtain relevant information on the stability of the movement, and determine the Movement stability. A motion stability threshold can be set. When the motion stability is lower than the motion stability threshold, for example, it is decided to sense the image under the third stage exposure condition; when the motion stability is not lower than the motion stability threshold, for example, determine Returning to step S1 or step 101, the third-stage exposure condition is sought again.
移動穩定度的計算方式可以有不同的方式，只要是根據該至少一第一亮度與該至少一第二亮度而得到，都屬於本發明的範圍。舉例而言，可以對應比較該至少一第一亮度與該至少一第二亮度，對所有該至少一第一亮度與該至少一第二亮度差值的絕對值，皆小於一閾值，則代表移動穩定度低於移動穩定度閾值，則決定以該第三階段曝光條件，感測該影像；如果有任何一第一亮度與對應之第二亮度絕對值的差值，不小於該閾值，則代表移動穩定度高於移動穩定度閾值，則決定不以該第三階段曝光條件，感測該影像。又如，將複數該第一亮度與複數該第二亮度之一絕對差和(sum of absolute difference)，作為該移動穩定度；當此移動穩定度低於移動穩定度閾值，則決定以該第三階段曝光條件，感測該影像；而當此移動穩定度高於移動穩定度閾值，則決定不以該第三階段曝光條件，感測該影像。該移動差和的計算方式，如下所示：
其中，d為移動差和，i代表第i個移動檢查像素，P為亮度，t代表第一時間，t+1代表第二時間。 Among them, d is the moving difference sum, i is the i-th moving inspection pixel, P is the brightness, t is the first time, and t + 1 is the second time.
需說明的是，在一種較佳的實施例中，該第一預設亮度與該第二預設亮度相同，皆為一預設中間亮度。舉例而言，像素的亮度分為0到 255之256級亮度，則預設中間亮度例如但不限於為128，且第一預設亮度與該第二預設亮度相同，皆為128。 It should be noted that, in a preferred embodiment, the first preset brightness is the same as the second preset brightness, and both are a preset intermediate brightness. For example, the brightness of a pixel ranges from 0 to 256-level brightness from 255, the preset intermediate brightness is, for example, but not limited to, 128, and the first preset brightness is the same as the second preset brightness, both being 128.
以上已針對較佳實施例來說明本發明，唯以上所述者，僅係為使熟悉本技術者易於了解本發明的內容而已，並非用來限定本發明之權利範圍。在本發明之相同精神下，熟悉本技術者可以思及各種等效變化。例如，各實施例中圖示直接連接的兩電路或元件間，可插置不影響主要功能的其他電路或元件，因此「耦接」應視為包括直接和間接連接。又如，所有實施例中的變化，可以交互採用，例如第3圖實施例中之如何決定在步驟S3中，增加或減少第一曝光時間，也可以應用於其他所有的實施例；第2、4、5、6、7圖實施例也可以應用在其他所有的實施例中，等等。凡此種種，皆可根據本發明的教示類推而得，因此，本發明的範圍應涵蓋上述及其他所有等效變化。 The present invention has been described above with reference to the preferred embodiments, but the above is only for making those skilled in the art easily understand the content of the present invention, and is not intended to limit the scope of rights of the present invention. In the same spirit of the invention, those skilled in the art can think of various equivalent changes. For example, in the embodiments, two circuits or components that are directly connected can be inserted with other circuits or components that do not affect the main function. Therefore, "coupling" should be considered to include direct and indirect connections. As another example, the changes in all embodiments can be adopted interactively, for example, how to determine the increase or decrease of the first exposure time in step S3 in the embodiment of FIG. 3 can also be applied to all other embodiments; The embodiments of 4, 5, 6, and 7 can also be applied to all other embodiments, and so on. All these can be deduced by analogy according to the teachings of the present invention. Therefore, the scope of the present invention should cover the above and all other equivalent changes.
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