CN102096174B

Movatterモバイル変換

Info

Publication number: CN102096174B
Application number: CN200910252444A
Authority: CN
Inventors: 林芃威; 郭力文
Original assignee: Altek Corp
Current assignee: Altek Corp
Priority date: 2009-12-09
Filing date: 2009-12-09
Publication date: 2012-09-26
Anticipated expiration: 2029-12-09
Also published as: CN102096174A

Abstract

A system and method for executing automatic focusing in low-brightness scene, especially for shooting low-brightness scene, can obtain digital image signal through lens module and photosensitive element, then use gain adjustment unit to gain-adjust the digital image signal to reduce noise, then use memory position capture unit to capture data of multiple memory positions in signal, so as to eliminate useless data position, then execute a color tone adjustment step, and generate accurate automatic focusing effect of real-time image by improving contrast of digital image signal.

Description

Translated fromChinese

在低亮度场景执行自动对焦的系统与方法System and method for performing autofocus in low-brightness scenes

技术领域technical field

本发明涉及一种低亮度场景执行自动对焦的系统与方法，特别是于低亮度场景拍摄时，通过记忆位(bit)的选取与色调调整达到准确即时图像自动对焦的技术。 The present invention relates to a system and method for auto-focusing in low-brightness scenes, in particular to a technology for achieving accurate and instant image auto-focusing by selecting memory bits and adjusting color tones when shooting low-brightness scenes. the

背景技术Background technique

自动对焦(Automatic Focusing，简称AF)技术让相机或摄像机于特定区域进行测距，进而调整镜头于一焦距(focal length)内，得到清晰的图像，此对于一般消费性的数字相机或摄像机来说已经是不可缺少的要件。 Autofocus (Automatic Focusing, referred to as AF) technology allows the camera or video camera to measure the distance in a specific area, and then adjust the lens within a focal length (focal length) to obtain a clear image. This is for general consumer digital cameras or video cameras. It is already an indispensable element. the

一般手动对焦(MF)的方式是由使用者于观景窗(viewfinder)利用其中的对焦屏(focusing screen)调整图像的清晰度，主要是调整底片或是感光元件与镜片组间的距离，也就是所谓的焦距，让图像准确地投影于底片或是感光元件上，也让用户在观景窗看到清晰的图像。 The general manual focus (MF) method is that the user uses the focusing screen in the viewfinder to adjust the sharpness of the image, mainly to adjust the distance between the negative film or the photosensitive element and the lens group, and also It is the so-called focal length, which allows the image to be accurately projected on the film or photosensitive element, and also allows the user to see a clear image in the viewing window. the

而自动对焦有几种方式，分为被动式和主动式两种，同样应用于目前消费性的数字相机或是摄像机上。 There are several ways of autofocus, which are divided into passive and active, which are also used in current consumer digital cameras or video cameras. the

被动式自动对焦应用于一些自动相机，其借助于被摄物反光的分析计算镜片组的移动位置，若在光线不足的环境下，则常常使用辅助对焦灯，如一些相机在进行对焦时，会打出一束颜色光，遇到被摄物体后反射回来，能够得到足够的反光，进而分析焦距，据以控制镜片组的位置。 Passive autofocus is used in some automatic cameras, which calculate the moving position of the lens group by means of the analysis of the reflection of the subject. If the light is insufficient, the auxiliary focus light is often used. For example, when some cameras focus, they will display When a beam of colored light meets the subject and is reflected back, enough reflection can be obtained, and then the focal length can be analyzed to control the position of the lens group. the

而另一自动对焦技术则是由相机或是摄像机本身发出超音波或红外线，利用由被摄物反射的信号计算距离，包括应用来往时间或是利用反射角来得出被摄物距离，进而调整自身焦距。 Another auto-focus technology is that the camera or the camera itself emits ultrasonic or infrared rays, and uses the signal reflected by the subject to calculate the distance, including using the time of travel or using the reflection angle to obtain the distance of the subject, and then adjust itself. focal length. the

随着科技进步，除了公知的自动对焦方式，更有相机或摄像机通过即时撷取的观景画面(如通过图像传感器撷取，而于LCD屏幕预览的画面)执行自动对焦程序，这也就是即时图像自动对焦(Live View自动对焦)，可于即时预览的同时完成构图及自动对焦。其中应用于相机内的自动对焦系统采用图像处理能力强大的处理器，通过图像清晰度运算，能够即时比对由图像传感器撷取的图像并快速搜寻焦点。 With the advancement of science and technology, in addition to the well-known auto-focus methods, there are still cameras or video cameras that perform auto-focus procedures through real-time captured viewing pictures (such as captured by image sensors and previewed on LCD screens), which is real-time Image autofocus (Live View autofocus), which can complete composition and autofocus while previewing in real time. Among them, the autofocus system applied in the camera adopts a processor with powerful image processing capability, and through image definition calculation, it can instantly compare the images captured by the image sensor and quickly search for the focus. the

图1为公知技术的自动对焦程序，自动对焦主要是通过步进马达(stepping motor)移动对焦镜片(步骤S101)，移动至一特定位置时，通过镜头撷取图像画面(步骤S103)，并在预设的几个位置点计算上述对焦屏中物体的清晰度，同时得出相对焦距(步骤S105)，此时判断是否有足够的数据(步骤S107)，若为否，表示还要继续执行通过马达移动对焦镜片、撷取图像、计算清晰度等步骤；若为是，则接着在这几个预设的位置中估计出具有最大清晰度的位置，即得出使图像最清楚的对焦位置(步骤S109)。之后移动镜片组(lens group)至最佳的焦距上(步骤S111)，完成自动对焦的程序。 Fig. 1 is the auto-focus program of the known technology, auto-focus is mainly to move the focus lens through a stepping motor (step S101), when moving to a specific position, capture the image frame through the lens (step S103), and Calculate the sharpness of the object in the above-mentioned focusing screen at several preset positions, and at the same time obtain the relative focal length (step S105), at this time, judge whether there is enough data (step S107), if not, it means to continue to pass The motor moves the focusing lens, captures the image, and calculates the sharpness; if yes, then estimate the position with the maximum sharpness among these preset positions, that is, the focus position that makes the image clearest ( Step S109). Then move the lens group (lens group) to the best focal length (step S111), and complete the auto-focus procedure. the

在上述利用撷取的图像计算清晰度的技术中，提供用以对焦的图像可能是足够亮度的图像，能够得到较为精确的焦距，但也可能为较暗的图像，而让对焦产生不精确的问题。 In the above technique of calculating the sharpness by using the captured image, the image provided for focusing may be an image with sufficient brightness to obtain a more accurate focus distance, but it may also be a darker image, resulting in inaccurate focusing question. the

图2为公知技术中数字相机中的电路方块图。其中显示数字相机内的主要元件，此例的相机中主要包括有自动白平衡、自动曝光与自动对焦的电路，相机利用镜头20拍摄图像，由图像感测器21接收并转换为数字信号，经图像前置处理单元22处理后，经自动白平衡单元23调整色温，之后经图像信号处理器24后执行预览、拍摄，或是储存图像。在撷取图像的过程中，仍需通过自动曝光单元27找到曝光值，通过自动对焦单元28得到正确的成像距离，这些信息通过马达驱动器29控制镜头马达，以得到正确对焦的图像。 FIG. 2 is a circuit block diagram of a digital camera in the prior art. It shows the main components in the digital camera. The camera in this example mainly includes circuits for automatic white balance, automatic exposure and automatic focus. The camera uses thelens 20 to capture images, which are received by theimage sensor 21 and converted into digital signals. After being processed by the image pre-processingunit 22 , the color temperature is adjusted by the automaticwhite balance unit 23 , and then theimage signal processor 24 performs preview, shooting, or image storage. In the process of capturing images, it is still necessary to find the exposure value through theauto exposure unit 27, obtain the correct imaging distance through theauto focus unit 28, and use the information to control the lens motor through themotor driver 29 to obtain a correctly focused image. the

另外，处理图像的过程中，包括从感光元件撷取图像开始，到图像处理、预览到储存，期间的记忆方式也可能因为硬件设计而撷取了较高位的值，使得对焦的精确度下降，尤其是在低亮度场景中，会因为撷取较高位而损失图像细节，除了噪声增加，更影响对焦的精确度。 In addition, in the process of image processing, including the image capture from the photosensitive element, image processing, preview and storage, the memory method during the period may also capture a higher bit value due to hardware design, which reduces the accuracy of focusing. Especially in low-brightness scenes, image details will be lost due to the capture of higher bits. In addition to increased noise, it will also affect the accuracy of focusing. the

发明内容Contents of the invention

本发明要解决的技术问题主要是在一般数字相机或是摄像机中设置一自动对焦系统，特别针对在低亮度场景下，利用即时图像对焦的方式会导致对焦不准确的问题，能够通过记忆位的选取与色调调整的手段，达到准确对焦的效果。 The technical problem to be solved by the present invention is mainly to install an auto-focus system in a general digital camera or a video camera, especially for the problem of inaccurate focus caused by the way of using real-time image focusing in low-brightness scenes. Select and adjust the color tone to achieve the effect of accurate focus. the

由于图像传感器要具有自动对焦的功能，尤其是针对即时图像对焦的方式，就必须经由搜寻镜头位置(调整成像距离)与图像清晰度的信息，调整焦距，取得最清晰的图像。 Since the image sensor needs to have an auto-focus function, especially for instant image focusing, it is necessary to adjust the focal length by searching the lens position (adjusting the imaging distance) and image definition information to obtain the clearest image. the

其中实施例之一包括利用一镜头模块拍摄图像，接着由感光元件，如CCD或CMOS，感光产生数字图像信号，之后，能通过增益调整单元调整数字图像信号的增益值，以降低噪声。由于由感光元件撷取的图像有较高的记忆位值，接着会因为硬件的限制而无法储存原有的记忆位值，本发明通过一记忆位撷取单元撷取有效的多个记忆位的数据。 One of the embodiments includes using a lens module to capture an image, and then a photosensitive element, such as a CCD or CMOS, generates a digital image signal, and then the gain value of the digital image signal can be adjusted by a gain adjustment unit to reduce noise. Since the image captured by the photosensitive element has a higher memory bit value, and then the original memory bit value cannot be stored due to hardware limitations, the present invention captures effective multiple memory bit values through a memory bit extraction unit data. the

接着，引入一色调调整单元执行色调调整步骤，能够将有效的记忆位值放大至一范围，以提高数字图像信号的对比，由此产生一对焦图像，再通过对焦单元计算对焦图像的清晰度，并根据一焦距自动调整镜头模块，以执行拍摄。Next, a tone adjustment unit is introduced to perform the tone adjustment step, which can amplify the effective memory bit value to a range to improve the contrast of the digital image signal, thereby generating a focused image, and then calculate the sharpness of the focused image through the focusing unit, And automatically adjust the lens module according to a focal length to perform shooting.

另外，由于本发明应用于低亮度场景的拍摄环境，故会引入由自动曝光单元(auto exposure)产生的曝光值与判断亮度高低的门槛值，经判断后，当环境处理低亮度场景时，即重复上述步骤达到准确即时图像自动对焦的目的。 In addition, since the present invention is applied to the shooting environment of low-brightness scenes, the exposure value generated by the auto exposure unit (auto exposure) and the threshold value for judging the brightness level will be introduced. After the judgment, when the environment processes low-brightness scenes, that is Repeat the above steps to achieve accurate instant image autofocus. the

本发明提供一种在低亮度场景执行自动对焦的系统，应用于一低亮度场景的拍摄，所述的系统包括有：一镜头模块，用以拍摄一图像；一感光元件，连结该镜头模块，且将该图像感光后而转换为数字图像信号；一增益调整单元，连结该感光元件，且将经该感光元件产生的该数字图像信号增益调整后以降低噪声；一记忆位撷取单元，连结该增益调整单元，用以撷取经降低噪声后的数字图像信号中多个记忆位的数据；一色调调整单元，连结该记忆位撷取单元，用以对经降低噪声后的该数字图像信号执行一色调调整步骤，由此提高该数字图像信号的对比；一对焦图像产生单元，系连结该色调调整单元以接收该经色调调整的数字图像信号，并将其转换为一对焦图像；以及一对焦单元，连结该对焦图像产生单元及该镜头模块，该对焦单元先计算出该对焦图像的清晰度，再根据一可令该对焦图像清晰的焦距自动调整该镜头模块，接续执行拍摄。 The present invention provides a system for performing autofocus in a low-brightness scene, which is applied to shooting a low-brightness scene. The system includes: a lens module for shooting an image; a photosensitive element connected to the lens module, And the image is converted into a digital image signal after being exposed to light; a gain adjustment unit is connected to the photosensitive element, and the gain of the digital image signal generated by the photosensitive element is adjusted to reduce noise; a memory bit extraction unit is connected to the The gain adjustment unit is used to extract the data of a plurality of memory bits in the digital image signal after noise reduction; a tone adjustment unit is connected to the memory bit extraction unit for performing on the digital image signal after noise reduction a tone adjustment step, thereby improving the contrast of the digital image signal; an in-focus image generation unit connected to the tone adjustment unit to receive the tone-adjusted digital image signal and convert it into an in-focus image; and a focus A unit is connected to the focused image generating unit and the lens module. The focusing unit first calculates the sharpness of the focused image, and then automatically adjusts the lens module according to a focal length that can make the focused image clear, and continues shooting. the

另外，本发明还提供一种在低亮度场景执行自动对焦的方法，所述的方法包括：通过一镜头模块撷取一图像，并通过一感光元件将该图像转换为数字图像信号；根据一自动曝光程序产生的曝光值判断该图像的明亮度，若属于一低亮度场景，即进行调整该感光元件的增益值，以降低经该感光元件产生的该数字图像信号的噪声；选择性撷取该数字图像信号的多个记忆位；调整该经选择的数字图像信号的色调，由此提高该数字图像信号的对比；以及利用经前述步骤调整过后的数字图像信号令该镜头模块执行自动对焦。 In addition, the present invention also provides a method for auto-focusing in a low-brightness scene, the method includes: capturing an image through a lens module, and converting the image into a digital image signal through a photosensitive element; according to an automatic The exposure value generated by the exposure program judges the brightness of the image. If it belongs to a low-brightness scene, the gain value of the photosensitive element is adjusted to reduce the noise of the digital image signal generated by the photosensitive element; selectively capture the A plurality of memory bits of the digital image signal; adjusting the color tone of the selected digital image signal, thereby improving the contrast of the digital image signal; the

附图说明Description of drawings

图1为公知技术的自动对焦程序的流程图； Fig. 1 is the flow chart of the autofocus program of known technology;

图2为公知技术中数字相机中的电路方块图； Fig. 2 is the circuit block diagram in the digital camera in the known technology;

图3a-图3c为记忆位在各阶段的状态示意图； Figure 3a-Figure 3c is a schematic diagram of the state of the memory bit at each stage;

图4为本发明在低亮度场景执行自动对焦的系统的电路方块图； Fig. 4 is the circuit block diagram of the system that the present invention performs auto-focus in low-brightness scene;

图5为应用图4所示的本发明在低亮度场景执行自动对焦的系统的整体电路方块图； Fig. 5 is the overall circuit block diagram of the system that applies the present invention shown in Fig. 4 to perform autofocus in low-brightness scenes;

图6为色调调整的对应曲线； Figure 6 is the corresponding curve of tone adjustment;

图7为本发明执行自动对焦的方法流程图； Fig. 7 is the flow chart of the method for performing autofocus in the present invention;

图8为本发明在低亮度场景执行自动对焦的方法流程图。 FIG. 8 is a flowchart of a method for performing autofocus in a low-brightness scene according to the present invention. the

【主要元件附图标记说明】【Description of reference signs of main components】

镜头20 图像传感器21 Lens 20Image sensor 21

图像前置处理单元22 自动白平衡单元23 Image pre-processing unit 22 Automaticwhite balance unit 23

图像信号处理器24 自动曝光单元27 Image signal processor 24Automatic exposure unit 27

自动对焦单元28 马达驱动器29 Auto focus unit 28Motor driver 29

镜头模块40 感光元件41 Lens module 40photosensitive element 41

增益调整单元42 记忆位撷取单元43 Gain adjustment unit 42 Memorybit extraction unit 43

色调调整单元44 数字增益补偿单元45 Tone adjustment unit 44 Digitalgain compensation unit 45

图像显示处理单元46 对焦图像产生单元47 Imagedisplay processing unit 46 Focused image generation unit 47

对焦单元48 显示单元49 Focus unit 48Display unit 49

储存单元57 按键组51 Storage unit 57key group 51

控制单元53 驱动单元55 Control unit 53Drive unit 55

具体实施方式Detailed ways

自动即时图像对焦技术通过由镜头、感光元件所拍摄的图像进行对焦的技术，在数字相机或摄像机对着图像拍摄时，镜头的驱动马达即先移动对焦镜片，在特定的几个位置点计算图像的清晰度，能自动搜寻取得对焦清晰锐利的位置的图像。自动搜寻的过程之一是，连续计算对焦区域内图像边缘清晰度，并寻找最大图像边缘清晰度的位置，而清晰度的常用方法有Sobel空间濾波器及Laplacian空间濾波器等，但本发明并非限制于这些方法中。 Automatic instant image focusing technology focuses on the image captured by the lens and photosensitive element. When the digital camera or video camera shoots the image, the driving motor of the lens first moves the focusing lens, and calculates the image at several specific positions. It can automatically search for images with clear and sharp focus. One of the processes of automatic search is to continuously calculate the sharpness of the image edge in the focus area, and find the position of the maximum sharpness of the image edge, and the commonly used methods for sharpness include Sobel spatial filter and Laplacian spatial filter, etc., but the present invention does not limited to these methods. the

在一般图像撷取时，由于硬件上的设计(通常有成本考虑)，在图像处理的过程中，常常会损失掉一些图像的细节，而在低亮度场景的图像亮度已经很低，且图像的噪声很大，故容易影响到对焦的精确度，如图3a-图3c所示的记忆位在各阶段的状态示意图。 In general image capture, due to hardware design (usually cost considerations), some image details are often lost in the process of image processing, and the image brightness in low-brightness scenes is already very low, and the image The noise is very large, so it is easy to affect the accuracy of focusing, as shown in Figure 3a-Figure 3c are the state diagrams of the memory bits at various stages. the

图3a中，图3a显示为由镜头拍摄、感光元件转换为数字图像信号、进入图像处理单元后的记忆位值，此例为12位，也就是数字图像信号有212的数据。而于之后经图像处理，储存(或暂存)于记忆媒体中，此时，所储存的值可能变成图3b显示的10位，也就是数据变成210。 In Figure 3a, Figure 3a shows the memory bit value after being captured by the lens, converted into a digital image signal by the photosensitive element, and entered into the image processing unit. In this example, it is 12 bits, that is, the digital image signal has 212 data. After image processing, it is stored (or temporarily stored) in the storage medium. At this time, the stored value may become 10 bits as shown in FIG. 3b, that is, the data becomes 210. the

接着，更可能因为要产生用于对焦的即时画面，而再降低即时图像的品质，如图3c所示，成为8位的数据。 Then, it is more likely to reduce the quality of the real-time image because of the need to generate a real-time image for focusing, as shown in FIG. 3 c , it becomes 8-bit data. the

此时，本发明提出一种低亮度场景执行自动对焦的系统与方法，特别是应用于低亮度场景的拍摄环境，针对上述可能在整个图像处理过程损失图像细节的问题，通过选取有效的记忆位，与色调调整的程序，产生较佳的对焦图像。 At this point, the present invention proposes a system and method for autofocusing in low-brightness scenes, especially for shooting environments with low-brightness scenes. Aiming at the above-mentioned problem of possible loss of image details in the entire image processing process, by selecting effective memory bits , with tone adjustment procedures, yields better in-focus images. the

请参阅图4所示的在低亮度场景执行自动对焦的系统的电路方块图，其中显示为本发明揭露的对焦系统，其中应用一图像处理模块400执行即时图像的最佳化，增进通过即时图像的对焦能力。 Please refer to the circuit block diagram of the system for performing auto-focus in low-brightness scenes shown in FIG. focusing ability. the

其中，利用一镜头模块40拍摄图像，镜头模块40以一组镜片组形成，可通过其中对焦镜片进行对焦，图像拍摄后，由一连结于镜头模块40的感光元件41撷取，经感光后转换为数字图像信号。感光元件41可为一般的CCD或是CMOS等。 Wherein, alens module 40 is used to capture an image, and thelens module 40 is formed by a set of lens groups, through which the focusing lens can be used for focusing. After the image is captured, it is picked up by aphotosensitive element 41 connected to thelens module 40, and converted after being photosensitive. for digital image signals. Thephotosensitive element 41 can be a general CCD or CMOS. the

为了要降低图像的噪声，故此对焦系统具有一连接于感光元件41的增益调整单元42，能将数字图像信号经增益调整后降低噪声，较佳的方式是降低感光元件41的增益值，同时能降低图像噪声。但是经降低增益值虽然可降低噪声，但会影响图像品质，故于正常拍摄的过程中，会再辅助以数字增益调整，以确保拍摄品质。如图中数字增益补偿单元45，此单元45即接收经增益调整后的数字图像信号，再通过数字增益补偿，以补偿调整感光元件41增益值后的图像。 In order to reduce the noise of the image, the focus system has a gain adjustment unit 42 connected to thephotosensitive element 41, which can reduce the noise after the digital image signal is adjusted by gain. Reduce image noise. However, although the noise can be reduced by reducing the gain value, it will affect the image quality. Therefore, in the process of normal shooting, it will be assisted by digital gain adjustment to ensure the shooting quality. As shown in the digitalgain compensation unit 45, thisunit 45 receives the digital image signal after gain adjustment, and then compensates the image after adjusting the gain value of thephotosensitive element 41 through digital gain compensation. the

经增益调整单元42调整增益值后，接着由一连接增益调整单元42的记忆位撷取单元43撷取经降低噪声后的数字图像信号，以撷取多个记忆位的数据(如前例中由较高的10位中撷取出8位的数据)，特别是撷取其中有效的记忆位，如撷取较低位置的记忆位，以避免于处理过程损失了图像的细节。值得注意的地方是，在低亮度场景下拍摄的图像，较高位置的记忆位通常是没有数据的状态，故撷取较低位阶的位，可避免损失细节。 After the gain value is adjusted by the gain adjustment unit 42, then a memorybit extraction unit 43 connected to the gain adjustment unit 42 captures the digital image signal after noise reduction to capture the data of a plurality of memory bits (as in the previous example by comparing 8 bits of data are extracted from the high 10 bits), especially the effective memory bits, such as the lower memory bits, to avoid loss of image details during processing. It is worth noting that for images captured in low-brightness scenes, the memory bits at higher positions usually have no data, so capturing lower-level bits can avoid loss of details. the

之后，引入一连接记忆位撷取单元43的色调调整单元44，用以对数字图像信号执行一色调调整(tone mapping)步骤，提高数字图像信号的对比。此色调调整步骤是将上述撷取的记忆位通过线性比例放大至一个范围，以放大其中的细节，经色调调整的图像有利于准确对焦。 Afterwards, atone adjustment unit 44 connected to the memorybit extraction unit 43 is introduced to perform a tone mapping step on the digital image signal to improve the contrast of the digital image signal. The tone adjustment step is to amplify the above-mentioned captured memory bits to a range through a linear ratio, so as to enlarge the details therein, and the tone-adjusted image is conducive to accurate focusing. the

在此实施例中，有一对焦图像产生单元47，连结于色调调整单元44，用以接收经色调调整的数字图像信号，并产生对焦图像，此对焦图像即用以作为即时图像对焦的图像，再由所连结的对焦单元48计算对焦图像的清晰度，最后根据一可令该对焦图像清晰的焦距自动调整该镜头模块40，以执行拍摄。 In this embodiment, there is a focus image generation unit 47, which is connected to thetone adjustment unit 44, to receive the digital image signal adjusted by tone, and generate a focus image. The sharpness of the focused image is calculated by the connected focusingunit 48 , and finally thelens module 40 is automatically adjusted according to a focal length that can make the focused image clear, so as to perform shooting. the

此实施例的附图中，显示相机内更具有图像显示处理单元46，接收自对焦单元48所得出的镜头模块40位置，借以输出自未显示的驱动马达，以拍摄准确对焦的图像。上述经自动对焦后自动调整镜头模块40的成像更应用于显示一即时图像，也就是，附图中图像显示处理单元46同时提供显示单元49显示即时图像，供使用者预览拍摄。 In the drawings of this embodiment, it is shown that the camera further has an imagedisplay processing unit 46 that receives the position of thelens module 40 obtained from theautofocus unit 48 and outputs it from the not-shown driving motor to capture accurately focused images. The above-mentioned imaging of the automatically adjustedlens module 40 after autofocus is more applicable to displaying a real-time image, that is, the imagedisplay processing unit 46 in the accompanying drawings simultaneously provides thedisplay unit 49 to display the real-time image for the user to preview and shoot. the

图5即为应用图4所示的本发明在低亮度场景执行自动对焦的系统的整体电路方块图。 FIG. 5 is an overall circuit block diagram of the system for performing auto-focus in a low-brightness scene using the present invention shown in FIG. 4 . the

由镜头模块40拍摄图像，通过感光元件41撷取后，转换为数字图像信号，经图4显示的图像处理模块400产生用于对焦的即时图像，并产生提供使用者预览的即时图像，如通过显示单元49显示的即时图像，或是产生数字图像文件储存于储存单元57中。 The image is captured by thelens module 40, captured by thephotosensitive element 41, and converted into a digital image signal. Theimage processing module 400 shown in FIG. The real-time images displayed by thedisplay unit 49 or generated digital image files are stored in thestorage unit 57 . the

同时，由图像处理模块400产生的对焦结果，其数据传递于控制单元53，控制单元53接收使用者通过按键组51的指令，比如半按快门按键，即自动执行对焦程序，由控制单元53接收到对焦信息，控制驱动单元55去驱动镜头模块40，调整对焦镜片的位置。 At the same time, the data of the focusing result generated by theimage processing module 400 is transmitted to thecontrol unit 53, and thecontrol unit 53 receives an instruction from the user through thebutton group 51, such as pressing the shutter button halfway to automatically execute the focusing procedure, and thecontrol unit 53 receives it. After receiving the focusing information, the drivingunit 55 is controlled to drive thelens module 40 to adjust the position of the focusing lens. the

经过反复的对焦程序，最后可得到一个最佳的对焦结果，达到准确即时图像自动对焦的目的。 After repeated focusing procedures, an optimal focusing result can be obtained at last, achieving the purpose of accurate instant image auto-focusing. the

上述对焦时，将移动镜头模块40到多个位置上，以计算清晰度，清晰度的计算的一方式是根据图像的边缘的画素进行比对，并估计清晰度最大的位置，即为自动对焦的结果。 When focusing above, move thelens module 40 to multiple positions to calculate the sharpness. One way to calculate the sharpness is to compare the pixels on the edge of the image and estimate the position with the highest sharpness, which is auto focus the result of. the

本发明在进行自动对焦前，先降低感光元件的增益值，之后，由于硬件或是其他考量(如成本、效率)的关系，仅撷取有效的记忆位，而在低亮度的拍摄场景下，本发明更提供如图6所示的色调调整的对应曲线，能够将数字图像信号通过线性比例放大，保持最多的细节。 The present invention first reduces the gain value of the photosensitive element before autofocusing, and then, due to hardware or other considerations (such as cost and efficiency), only effective memory bits are captured, and in low-brightness shooting scenes, The present invention further provides a corresponding curve for tone adjustment as shown in FIG. 6 , which can amplify the digital image signal through linear scaling and maintain the most details. the

此例中，色调调整的对应曲线的横轴显示色调输入值，原输入的图像可有0-4095(12位)的范围，经过上述选取记忆位后(损失部份细节)，在一实施例中，实际处理的图像值经计算图像亮度的平均值及标准偏差，将落于图中M_low与M_high之间，之后经线性放大，色调输出值(纵轴)即放大到0至255(8位)之间，以此线性比例放大至一个范围，以放大其中的细节，有利于使用即时画面准确对焦。 In this example, the horizontal axis of the corresponding curve of tone adjustment shows the tone input value, and the original input image can have a range of 0-4095 (12 bits). In the process, the actual processed image value will fall between M_low and M_high in the figure after calculating the average value and standard deviation of the image brightness, and then linearly amplified, the tone output value (vertical axis) will be amplified to 0 to 255 ( 8-bit), zoom in to a range with this linear ratio to zoom in on the details, which is conducive to accurate focusing in real-time images.

图7显示为本发明执行自动对焦的方法流程图。 FIG. 7 is a flow chart of the method for performing autofocus in the present invention. the

在此实施例开始时，如步骤S701，由镜头模块撷取图像，经自动曝光(AE)后，由自动曝光程序产生的曝光值得出明亮度(步骤S703)，并通过一门槛值判断亮或暗(步骤S705)。 At the beginning of this embodiment, as in step S701, the image is captured by the lens module, and after automatic exposure (AE), the brightness is obtained from the exposure value generated by the automatic exposure program (step S703), and a threshold value is used to judge whether it is bright or not. dark (step S705). the

若判断为“亮”，即属于一高亮度场景，表示通过所撷取的图像可以产生准确的对焦，故可执行自动对焦(步骤S713)，产生即时图像，并供使用者预览(步骤S715)。 If it is judged as "bright", it belongs to a high-brightness scene, indicating that accurate focus can be generated through the captured image, so auto-focus can be performed (step S713), and an instant image is generated for the user to preview (step S715) . the

但，若判断为“暗”，若属于一低亮度场景，表示位于低亮度场景中，先如步骤S707，降低感光元件增益值，以降低图像中的噪声。之后选择性撷取记忆位(步骤S709)，由于在低亮度场景容易因为在撷取记忆位的过程中损失掉更多细节，故本发明选择撷取有效的记忆位，比如撷取较低位阶的记忆位，以维持其中细节。 However, if it is judged to be "dark", if it belongs to a low-brightness scene, it means that it is in a low-brightness scene. Firstly, as in step S707, the gain value of the photosensitive element is reduced to reduce the noise in the image. Afterwards, the memory bits are selectively retrieved (step S709). Since it is easy to lose more details in the process of retrieving memory bits in low-brightness scenes, the present invention chooses to capture effective memory bits, such as capturing lower bits. The memory bits of the order to maintain the details in it. the

之后，如步骤S711，执行一线性对应运算，经色调调整至一范围，借此提高该数字图像信号的对比产生能够精确对焦的即时图像，接着利用经前述步骤调整过后的数字图像信号令镜头模块执行自动对焦(步骤S713)与即时图像预览(步骤S715)。 Afterwards, as in step S711, a linear correspondence operation is performed, and the color tone is adjusted to a range, thereby improving the contrast of the digital image signal to generate an instant image capable of precise focus, and then using the digital image signal adjusted through the preceding steps to make the lens module Perform auto-focus (step S713) and instant image preview (step S715). the

接着请参阅图8所示的本发明在低亮度场景执行自动对焦的方法流程图。此例为已判断在低亮度场景中拍摄的流程，在低亮度场景中，先降低感光元件增益值(步骤S801)，以降低噪声。接着，所撷取的图像同时会用于“对焦用”与“拍摄用”。 Next, please refer to FIG. 8 for the flow chart of the method for performing autofocus in a low-brightness scene of the present invention. This example is the process of determining that the shooting is in a low-brightness scene. In the low-brightness scene, first reduce the gain value of the photosensitive element (step S801 ) to reduce noise. Then, the captured image will be used for "focusing" and "shooting" at the same time. the

若用于对焦用，本发明所提供的对焦系统将选择地调整撷取记忆位(步骤S803)，再用于调整色调(步骤S805)，色调调整可参考图6。经调整色调的图像提供用于即时图像预览(步骤S807)，接收经色调调整的数字图像信号后，产生对焦图像，也就是一即时图像，借以执行自动对焦，通过镜头模块移动的多个位置上计算出多个清晰度，并估计清晰度最大的位置即为自动对焦的结果(步骤S809)。 If it is used for focusing, the focusing system provided by the present invention will selectively adjust the capture memory bit (step S803 ), and then use it to adjust the hue (step S805 ). Refer to FIG. 6 for hue adjustment. The tone-adjusted image is provided for instant image preview (step S807). After receiving the tone-adjusted digital image signal, an in-focus image, that is, an instant image is generated, so as to perform autofocus, and move through multiple positions of the lens module A plurality of sharpnesses are calculated, and the position with the highest sharpness is estimated to be the auto-focus result (step S809 ). the

若用于拍摄用，由于先于步骤S801中降低感光元件的增益值，此时，即再执行数字增益补偿(步骤S811)，使得使用者于屏幕看到的图像亮度与未降低增益值时相同，之后经图像处理，接收由上述对焦程序的结果(步骤S813)，执行拍摄(步骤S815)。 If it is used for shooting, since the gain value of the photosensitive element is lowered in step S801, digital gain compensation is then performed (step S811), so that the brightness of the image seen by the user on the screen is the same as when the gain value is not reduced , after image processing, the result of the above-mentioned focusing procedure is received (step S813), and shooting is performed (step S815). the

综上所述，根据本发明揭露一种在低亮度场景执行自动对焦的系统与方法，通过判断亮、暗度的程序，于低亮度场景中应用调整撷取的记忆位、线性色调调整，在使用较多的有效位的情况下，能得到更精确的对焦。另一方面，于拍摄过程中，能通过数字增益补偿，得到维持亮度的图像。 In summary, according to the present invention, a system and method for autofocusing in low-brightness scenes are disclosed. Through the procedure of judging the brightness and darkness, the memory bit and linear tone adjustment are applied in low-brightness scenes. In the case of using more effective bits, more precise focusing can be obtained. On the other hand, during the shooting process, an image that maintains brightness can be obtained through digital gain compensation. the

但是以上所述仅为本发明的较佳可行实施例，非因此即局限本发明的权利要求保护范围，故凡运用本发明说明书及附图内容所为的等效结构变化，均同理包含于本发明的权利要求保护范围内，特此声明。 However, the above description is only a preferred feasible embodiment of the present invention, and does not limit the protection scope of the claims of the present invention. Therefore, all equivalent structural changes made by using the description of the present invention and the contents of the accompanying drawings are all included in the same way. Within the protection scope of the claims of the present invention, it is hereby declared. the