CN114945069A - Novel real-time automatic dimming method and imaging equipment - Google Patents

The invention relates to a novel real-time automatic dimming method and imaging equipment, wherein the method comprises the following steps: acquiring an image of a current scene acquired by an image sensor in real time; calculating the contrast of the image based on an eight-neighbor calculation method; judging whether the contrast of the image meets the evaluation standard of good exposure of the image, if so, re-acquiring the image acquired by the image sensor in real time, otherwise, calculating the average gray value of the image, and judging the dimming direction of the diaphragm according to the average gray value; and driving the diaphragm to adjust according to the dimming direction. The method and the device judge whether the dimming system is located at the optimal exposure position according to the image contrast, judge the adjustment direction of the dimming system according to the average gray value of the image, solve the problems of dimming failure caused by misjudgment of the adjustment direction of the system, incapability of adjusting to the optimal exposure position and the like, have high algorithm real-time performance, and can meet the shooting requirement of the high-speed visible light camera in the shooting range.

一种新型的实时自动调光方法以及成像设备A novel real-time automatic dimming method and imaging device

技术领域technical field

本发明涉及成像技术领域，特别是涉及一种新型的实时自动调光方法以及成像设备。The invention relates to the technical field of imaging, in particular to a novel real-time automatic dimming method and imaging device.

背景技术Background technique

太阳的辐射量会随着纬度、季节、天气的变化而变化，而在海天的特殊的光照环境下，由于太阳的仰角、波长、海水表面的起伏(波浪)和接近海面的空气泡等因素，海水表面对太阳辐射有着大约6％的平均反射率。可见光高速相机成像受环境光照度的影响，装备可见光高速相机的光电经纬仪，在靶场任务中通常采用手动调光或者静态自动调光策略(即针对背景光照不变的情况下进行调光，当调整到合适的曝光位置时自动停止)。在光电经纬仪跟踪目标的过程中，由于海天环境背景光照度的剧烈变化，导致可见光高速相机的成像受到严重的影响。随着对光学测控的精度要求不断提高，要保证在准确捕获目标、实时跟踪目标的同时更高效地获取瞬息变化的细节，必须克服目标与背景光照剧烈变化的问题，因此亟需针对经纬仪的实时自动调光算法的研究。The amount of solar radiation varies with latitude, season, and weather. In the special lighting environment of the sea and sky, due to factors such as the sun's elevation angle, wavelength, fluctuations (waves) on the sea surface, and air bubbles close to the sea surface, etc. The sea surface has an average reflectivity of about 6% for solar radiation. The imaging of the visible light high-speed camera is affected by the ambient light intensity. The photoelectric theodolite equipped with the visible light high-speed camera usually adopts manual dimming or static automatic dimming strategy in the shooting range task (that is, dimming is performed when the background illumination remains unchanged. automatically stops when the exposure position is suitable). In the process of tracking the target with the optoelectronic theodolite, the imaging of the visible light high-speed camera is seriously affected due to the dramatic changes in the background illumination of the sea and sky environment. With the continuous improvement of the accuracy requirements of optical measurement and control, in order to ensure that the target can be accurately captured and tracked in real time, and the details of the instantaneous changes must be obtained more efficiently, the problem of drastic changes in the target and background illumination must be overcome. Research on automatic dimming algorithm.

目前的基于图像处理的调光策略都是：(1)光强测量，(2)测光评价，(3)指导调光，(4)完成补偿，形成了一个从测量到调整的闭环操作。现有的测光方式通常有两种：硬件测光和图像评价。硬件测光方式需要光度计对主镜中的实时进光量进行测量，通过对进光量的评价，去指导图像传感器的曝光时间完成系统调光。由于可见光高速相机在连续拍摄的方式下，帧速可以达到100f/s，因此前后帧图像的差别一般很小。图像评价的方式是对上一帧图像进行平均测光，通过评价值对当前帧图像进行曝光调整。目前基于图像评价的自动调光主要分为4种：基于平均亮度均值的自动调光算法；基于图像信息熵的调光算法；基于图像直方图的自动调光算法；基于图像内容的自动调光算法。The current dimming strategies based on image processing are: (1) light intensity measurement, (2) photometric evaluation, (3) guiding dimming, and (4) completing compensation, forming a closed-loop operation from measurement to adjustment. There are usually two kinds of existing metering methods: hardware metering and image evaluation. The hardware metering method requires a photometer to measure the real-time light input in the main mirror, and through the evaluation of the light input, it guides the exposure time of the image sensor to complete the system dimming. Since the visible light high-speed camera can shoot continuously, the frame rate can reach 100f/s, so the difference between the front and rear frame images is generally small. The method of image evaluation is to perform average light metering on the previous frame image, and adjust the exposure of the current frame image according to the evaluation value. At present, automatic dimming based on image evaluation is mainly divided into four types: automatic dimming algorithm based on average brightness average; dimming algorithm based on image information entropy; automatic dimming algorithm based on image histogram; automatic dimming algorithm based on image content algorithm.

基于平均亮度均值的自动调光算法在计算测光评价值来指导调光系统时，受限于目标和背景差异的影响，对环境的适应性较差，不太适用于作为测光评价值的计算。基于图像信息熵的调光算法可以衡量图像的复杂程度，根据信息熵的范围来确定曝光参数，此方法很容易受到图像本身内容的影响，若图像信号非常平坦且值很小，基于图像信息熵的测光方法导致调光系统向导致图像过曝的方向调整。传统基于图像直方图的评价方法对灰度级数陡峭峰值很敏感，可以通过峰值区域来确定像素灰度权重值，但容易受到噪声的干扰而判断失误，对环境适应性较差。很多根据现有的测光评价函数提出的改进方法，往往由于实时性的问题不适用于靶场高速相机的拍摄需求。When calculating the photometric evaluation value to guide the dimming system, the automatic dimming algorithm based on the average brightness is limited by the influence of the difference between the target and the background, and has poor adaptability to the environment, so it is not suitable for use as a photometric evaluation value. calculate. The dimming algorithm based on image information entropy can measure the complexity of the image, and determine the exposure parameters according to the range of information entropy. This method is easily affected by the content of the image itself. If the image signal is very flat and the value is very small, based on the image information entropy The metering method of , causes the dimming system to adjust in the direction that causes the image to be overexposed. The traditional evaluation method based on image histogram is very sensitive to the steep peak value of the gray level, and the pixel gray weight value can be determined by the peak area, but it is easy to be disturbed by noise, and the judgment is wrong, and the adaptability to the environment is poor. Many improved methods based on the existing photometric evaluation functions are often not suitable for shooting requirements of high-speed cameras in shooting ranges due to real-time problems.

专利CN201310384693.4是一种全调光范围快速自动调光方法，包括以下步骤：首先，根据积分时间所处的积分时间区间改变光阑大小，调整积分时间所处的工作区间，扩展调光范围，以保证积分时间在整个调光范围内都可以快速调整由于场景变化所造成的输出图像亮度的变化；然后，通过改变积分时间来调整图像亮度。该方法实现简单，但存在一些问题，如∶(1)复杂的海天背景时，跟踪快速移动目标，图像将会快速的过曝，导致跟踪失败；(2)从光阑最大位置时首先判断积分时间会导致调整时间过长，无法满足经纬仪在运动过程中的实时调光，效率较低。Patent CN201310384693.4 is a fast automatic dimming method with full dimming range, which includes the following steps: first, change the aperture size according to the integration time interval in which the integration time is located, adjust the working area in which the integration time is located, and expand the dimming range , to ensure that the integration time can quickly adjust the brightness of the output image caused by the scene change in the entire dimming range; then, adjust the brightness of the image by changing the integration time. This method is simple to implement, but there are some problems, such as: (1) When tracking a fast-moving target in a complex sea and sky background, the image will be quickly overexposed, resulting in tracking failure; (2) First judge the integral when the diaphragm is at the maximum position Time will cause the adjustment time to be too long, which cannot meet the real-time dimming of the theodolite during the movement process, and the efficiency is low.

专利CN201410198357.5是一种基于B-P神经网络判断照明场景的自动曝光方法，包括以下步骤，S1通过视频采集系统获得原始图像；S2将原始图像划分为多个区域；S3求每个区域的图像亮度平均值，获得亮度矢量；S4设计B-P神经网络，将亮度矢量作为神经网络的输入，对照明场景进行判断；S5根据神经网络的判断结果，计算图像的理想亮度；S6将原始图像的实际亮度与理想亮度的偏差作为PID算法的初始输入，利用PID算法获取理想亮度对应的理想可控量；S7依据理想可控量，获得曝光时间t和模拟增益系数g，将t和g传输到视频采集系统的传感器中即可实现自动曝光。该方法对照明场景的判断准确，算法简单，但同样存在图像会快速的过曝而导致跟踪失败以及无法满足经纬仪在运动过程中的实时调光，效率较低的问题，而且该发明的图像亮度判断方法耗时太多，无法满足实时性需求。Patent CN201410198357.5 is an automatic exposure method for judging lighting scenes based on B-P neural network, including the following steps: S1 obtains the original image through a video acquisition system; S2 divides the original image into multiple areas; S3 finds the image brightness of each area The average value is obtained to obtain the brightness vector; S4 designs a B-P neural network, and uses the brightness vector as the input of the neural network to judge the lighting scene; S5 calculates the ideal brightness of the image according to the judgment result of the neural network; S6 compares the actual brightness of the original image with that of the image. The deviation of the ideal brightness is used as the initial input of the PID algorithm, and the PID algorithm is used to obtain the ideal controllable quantity corresponding to the ideal brightness; S7 obtains the exposure time t and the analog gain coefficient g according to the ideal controllable quantity, and transmits t and g to the video acquisition system automatic exposure can be achieved in the sensor. This method is accurate in judging the lighting scene, and the algorithm is simple, but there are also problems that the image will be quickly overexposed, which will lead to tracking failure, and it cannot meet the real-time dimming of the theodolite during the movement process, and the efficiency is low, and the image brightness of the invention is low. The judgment method takes too much time and cannot meet the real-time requirements.

发明内容SUMMARY OF THE INVENTION

为了解决复杂的环境对测光评价函数的影响，本发明根据图像对比度来判断调光系统是否位于最佳的曝光位置，并通过图像的平均灰度值判断调光系统的调整方向，解决了系统调整方向的判断失误导致的调光失败和无法调整到最佳的曝光位置等问题，同时本发明算法实时性较高，可以满足靶场高速可见光相机的拍摄需求。In order to solve the influence of complex environment on the photometric evaluation function, the present invention judges whether the dimming system is in the best exposure position according to the image contrast, and judges the adjustment direction of the dimming system according to the average gray value of the image. The failure of dimming and the inability to adjust to the best exposure position caused by the wrong judgment of the adjustment direction, and at the same time, the algorithm of the present invention has high real-time performance and can meet the shooting requirements of high-speed visible light cameras in the shooting range.

为实现上述目的，本发明采取如下的技术方案：For achieving the above object, the present invention adopts the following technical scheme:

一种新型的实时自动调光方法，所述方法包括以下步骤：A novel real-time automatic dimming method comprising the following steps:

步骤一：获取图像传感器实时采集的当前场景的图像；Step 1: acquire the image of the current scene captured by the image sensor in real time;

步骤二：基于八近邻的计算方法计算所述图像的对比度；Step 2: Calculate the contrast of the image based on the calculation method of the eight nearest neighbors;

步骤三：判断所述图像的对比度是否满足图像良好曝光的评价标准，若是，则返回步骤一，重新获取所述图像传感器实时采集的图像，否则执行步骤四；Step 3: judging whether the contrast of the image meets the evaluation criteria for good image exposure, if so, return to step 1, and re-acquire the image captured by the image sensor in real time, otherwise, perform step 4;

步骤四：计算所述图像的平均灰度值，并根据所述平均灰度值判断光阑的调光方向；Step 4: Calculate the average gray value of the image, and determine the dimming direction of the diaphragm according to the average gray value;

步骤五：根据所述调光方向驱动所述光阑进行调整，调整后返回步骤一，重新获取所述图像传感器实时采集的图像。Step 5: Drive the diaphragm to adjust according to the dimming direction, and return to step 1 after adjustment to re-acquire the image captured by the image sensor in real time.

同时，本发明还提出一种成像设备，所述成像设备包括图像传感器、光阑和处理计算机，所述图像传感器与所述光阑封闭于带有通光孔的壳体中，所述光阑包括光阑座、安装在所述光阑座上的光阑片和用于驱动所述光阑片转动的驱动电机，并且所述驱动电机与所述处理计算机连接；At the same time, the present invention also provides an imaging device, the imaging device includes an image sensor, a diaphragm and a processing computer, the image sensor and the diaphragm are enclosed in a casing with a light-passing hole, and the diaphragm comprising a diaphragm seat, a diaphragm plate mounted on the diaphragm seat, and a driving motor for driving the diaphragm plate to rotate, and the driving motor is connected with the processing computer;

所述成像设备拍摄的当前场景的光线经过所述通光孔被所述光阑片线性斩切后入射至所述图像传感器上，所述图像传感器将采集的当前场景的图像传输至所述处理计算机，所述处理计算机执行以下实时自动调光步骤：The light of the current scene captured by the imaging device is linearly chopped by the aperture through the light aperture and then incident on the image sensor, and the image sensor transmits the captured image of the current scene to the processing A computer, the processing computer performs the following real-time automatic dimming steps:

步骤一：获取所述图像传感器实时采集的当前场景的图像；Step 1: acquiring the image of the current scene collected in real time by the image sensor;

步骤二：基于八近邻的计算方法计算所述图像的对比度；Step 2: Calculate the contrast of the image based on the calculation method of the eight nearest neighbors;

步骤三：判断所述图像的对比度是否满足图像良好曝光的评价标准，若是，则返回步骤一，重新获取所述图像传感器实时采集的图像，否则执行步骤四；Step 3: judging whether the contrast of the image meets the evaluation criteria for good image exposure, if so, return to step 1, and re-acquire the image captured by the image sensor in real time, otherwise, perform step 4;

步骤四：计算所述图像的平均灰度值，并根据所述平均灰度值判断光阑的调光方向；Step 4: Calculate the average gray value of the image, and determine the dimming direction of the diaphragm according to the average gray value;

步骤五：根据所述调光方向输出电机控制命令至所述驱动电机，使所述驱动电机驱动所述光阑片进行转动，调整所述光阑片的通光量，调整后返回步骤一，重新获取所述图像传感器实时采集的图像。Step 5: Output a motor control command to the drive motor according to the dimming direction, so that the drive motor drives the diaphragm to rotate, adjusts the amount of light passing through the diaphragm, returns to step 1 after adjustment, and restarts. Images captured by the image sensor in real time are acquired.

本发明所提出的新型的自动调光方法属于一种基于图像处理的实时自动调光策略，可应用在海天背景等复杂光照条件下的目标测量中。传统的方法有基于价格昂贵的光感元器件实现的自动调光，不仅受限于成本，且感光传感器与图像传感器协同工作导致系统复杂，而本发明基于图像传感器采集的实时图像进行测光评价，系统简单易于实现。The novel automatic dimming method proposed by the invention belongs to a real-time automatic dimming strategy based on image processing, and can be applied to target measurement under complex lighting conditions such as sea and sky backgrounds. The traditional method includes automatic dimming based on expensive photosensitive components, which is not only limited by cost, but also complicated by the cooperative work of photosensitive sensor and image sensor, while the present invention performs photometric evaluation based on real-time images collected by the image sensor , the system is simple and easy to implement.

本发明的实时自动调光方法可以让调光系统一直处于调光状态，当光电经纬仪在快速跟踪目标时，由于背景光照条件的快速变化导致了图像过曝或欠曝时，可以在第一时间做出响应，指导调光系统运行，保证图像处于最佳曝光状态。本发明具有以下有益效果：The real-time automatic dimming method of the present invention can keep the dimming system in a dimming state all the time. When the photoelectric theodolite is rapidly tracking the target, when the image is overexposed or underexposed due to the rapid change of the background lighting conditions, it can be immediately Respond to direct the operation of the dimming system to ensure optimal exposure of the image. The present invention has the following beneficial effects:

(1)本发明的实时自动调光方法的特点是让调光系统一直处于调光状态，通过采用图像的灰度均值与图像对比度相结合的测光策略，实时对图像传感器采集到的图像进行测光评价，具体的评价内容包括：1)利用图像对比度的单峰特性判断当前图像是否处于最佳的曝光状态；2)利用图像的灰度均值的单调特性判断调光系统的调整方向；当背景光照快速变化时，调光系统可以快速相响，保证图像处于最佳曝光状态，达到实时自动调光的目的；(1) The feature of the real-time automatic dimming method of the present invention is to keep the dimming system in a dimming state all the time, and by adopting a photometric strategy combining the gray mean value of the image and the image contrast, the image collected by the image sensor is processed in real time. Metering evaluation, the specific evaluation contents include: 1) Use the single-peak characteristic of image contrast to determine whether the current image is in the best exposure state; 2) Use the monotonic characteristic of the average gray value of the image to determine the adjustment direction of the dimming system; When the background light changes rapidly, the dimming system can respond quickly to ensure that the image is in the best exposure state and achieve the purpose of real-time automatic dimming;

(2)本发明的实时自动调光方法可以对可见光高速传感器和短波红外传感器等相机采集的图像进行评价，适用范围广，并且成像设备中的调光系统所设计的调光元件是光阑，成本低，操作方便。(2) The real-time automatic dimming method of the present invention can evaluate images collected by cameras such as visible light high-speed sensors and short-wave infrared sensors, and has a wide range of applications, and the dimming element designed by the dimming system in the imaging device is a diaphragm, Low cost and easy operation.

附图说明Description of drawings

图1为本发明一种新型的实时自动调光方法的流程图；1 is a flowchart of a novel real-time automatic dimming method of the present invention;

图2为本发明一种新型的实时自动调光方法的另一个流程图；Fig. 2 is another flow chart of a novel real-time automatic dimming method of the present invention;

图3为从欠曝光到过曝光图像对比度示意图；Figure 3 is a schematic diagram of image contrast from underexposure to overexposure;

图4为像素八近邻示意图；4 is a schematic diagram of eight neighbors of pixels;

图5为从欠曝光到过曝光图像的平均灰度值示意图；Fig. 5 is a schematic diagram of the average gray value of an image from underexposure to overexposure;

图6为本发明成像设备的结构示意图；6 is a schematic structural diagram of an imaging device of the present invention;

图7为本发明成像设备中光阑的结构示意图。FIG. 7 is a schematic structural diagram of a diaphragm in the imaging device of the present invention.

具体实施方式Detailed ways

下面将结合附图及较佳实施例对本发明的技术方案进行详细描述。The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

在其中一个实施例中，本发明新型的实时自动调光方法的调光流程如图1所示，具体包括以下步骤：In one of the embodiments, the dimming flow of the novel real-time automatic dimming method of the present invention is shown in FIG. 1 , which specifically includes the following steps:

步骤一：首先由图像传感器对当前场景进行实时图像采集，获取图像传感器实时采集的图像；Step 1: firstly, the image sensor performs real-time image acquisition on the current scene, and obtains the image acquired by the image sensor in real time;

步骤二：基于八近邻的计算方法计算图像的对比度；Step 2: Calculate the contrast of the image based on the calculation method of the eight nearest neighbors;

对比度表达了图像最高和最低灰度级之间的灰度差，通俗的讲就是亮暗的拉伸对比程度，表现了画质的清晰程度。在同一场景下，图像从欠曝光到过曝光其对比度呈现一种单峰性的对称分布，如图3所示。当对比度最大时，图像处于最佳的曝光状态。常见的对比度计算均基于四近邻的计算方法，即指计算上下左右四个相近邻像素间的灰度差，而本算法为了实用性更广、鲁棒性更强，采用了基于八近邻的计算方法来计算图像的对比度，如图4所示，具体的图像的对比度计算公式如下：Contrast expresses the grayscale difference between the highest and lowest grayscale levels of the image. In layman's terms, it is the degree of stretched contrast between light and dark, which expresses the clarity of the image quality. In the same scene, the contrast of the image from underexposure to overexposure presents a unimodal symmetrical distribution, as shown in Figure 3. When the contrast is at its maximum, the image is optimally exposed. The common contrast calculation is based on the calculation method of the four nearest neighbors, which means to calculate the grayscale difference between the four adjacent pixels of the upper, lower, left, and right, and this algorithm uses the calculation based on the eight nearest neighbors for wider practicability and stronger robustness. method to calculate the contrast of the image, as shown in Figure 4, the specific formula for calculating the contrast of the image is as follows:

C＝∑_δδ(i,j)²P_δ(i,j) (1)C=∑ _δ δ(i,j) ² P _δ (i,j) (1)

其中：δ(i,j)＝|i-j|表示相邻像素间的灰度差；Where: δ(i,j)=|i-j| represents the grayscale difference between adjacent pixels;

P_δ(i,j)表示相邻像素间的灰度差为δ的像素分布概率。P _δ (i,j) represents the pixel distribution probability that the grayscale difference between adjacent pixels is δ.

步骤三：判断图像的对比度是否满足图像良好曝光的评价标准，若是，则返回步骤一，重新获取图像传感器实时采集的图像，否则执行步骤四；Step 3: determine whether the contrast of the image meets the evaluation criteria for good image exposure, if so, return to step 1 to re-acquire the image captured by the image sensor in real time, otherwise, perform step 4;

在本发明中，基于图像从欠曝光到过曝光其对比度呈现一种单峰性的对称分布这种特性，以图像的对比度作为评价值，并设定图像良好曝光的评价标准，判断图像的对比度是否满足图像良好曝光的评价标准，如果满足，说明当前正处于良好的曝光状态，然后返回步骤一，重新获取图像传感器实时采集的图像并进行测光评价；如果不满足，说明正处于过曝或者欠曝的状态，因此需要对系统进行调光方向的判断，即执行步骤四。In the present invention, based on the characteristic that the contrast of the image exhibits a unimodal symmetrical distribution from underexposure to overexposure, the contrast of the image is used as the evaluation value, and the evaluation standard for good exposure of the image is set to determine the contrast of the image. Whether the evaluation criteria for good image exposure is met. If so, it means that it is currently in a good exposure state. Then go back to step 1 to re-acquire the image captured by the image sensor in real time and perform metering evaluation; if not, it means that it is in overexposure or The state of underexposure, so it is necessary to judge the dimming direction of the system, that is, step 4 is executed.

本步骤中图像良好曝光的评价标准为图像的对比度大于对比度阈值，即对比度阈值与最大图像对比度C_max之间的区域是图像良好曝光的评价标准，其中对比度阈值可以通过两种方式确定，一种是根据经验人工确定对比度阈值的大小，另一种是由算法自动设置，即以评价标准对比度最大值的90％作为对比度阈值，而评价标准对比度最大值是指预设时间段内图像传感器采集的图像的对比度最大值的平均值。本发明采用第二种方式确定对比度阈值，更加符合调光的实际情况。In this step, the evaluation standard for good image exposure is that the contrast of the image is greater than the contrast threshold, that is, the area between the contrast threshold and the maximum image contrast _Cmax is the evaluation standard for good image exposure, and the contrast threshold can be determined in two ways. One The size of the contrast threshold is manually determined based on experience, and the other is automatically set by the algorithm, that is, 90% of the maximum contrast value of the evaluation standard is used as the contrast threshold, and the maximum contrast value of the evaluation standard refers to the image sensor collected in the preset time period. The average of the contrast maxima of the image. The present invention adopts the second method to determine the contrast threshold, which is more in line with the actual situation of dimming.

步骤四：计算图像的平均灰度值，并根据平均灰度值判断光阑的调光方向；Step 4: Calculate the average gray value of the image, and judge the dimming direction of the diaphragm according to the average gray value;

图像的对比度代表图像的清晰程度，图像亮度可以理解为图像的明暗程度，图像亮度上的变化并不会影响图像的对比度。但是亮度的过度变化，导致了最大灰度值与最小灰度值接近且一致时会影响图像的对比度。在同一场景下，图像从欠曝光到过曝光其平均灰度值呈现一种单调分布，如图5所示。一幅尺寸为m×n的图像，其平均灰度值M的计算公式如下：The contrast of the image represents the clarity of the image, and the brightness of the image can be understood as the brightness of the image. Changes in the brightness of the image will not affect the contrast of the image. However, the excessive change of brightness will affect the contrast of the image when the maximum gray value and the minimum gray value are close and consistent. In the same scene, the average gray value of the image shows a monotonic distribution from underexposure to overexposure, as shown in Figure 5. For an image of size m×n, the calculation formula of the average gray value M is as follows:

其中：L代表图像的大小，其取值是m×n；z_k代表图像中所有可能的灰度级，k的取值范围是0～L-1；p(z_k)表示图像中灰度级z_k出现的概率。Among them: L represents the size of the image, and its value is m×n; z _k represents all possible gray levels in the image, and the value range of k is 0～L-1; p(z _k ) represents the gray level in the image probability of occurrence of class _zk .

仍参见图5，当图像处于欠曝光时，图像的平均灰度值最小值为M_min，当图像处于过曝光时，图像的平均灰度值最大值为M_max。取平均灰度值最小值与平均灰度值最大值的平均值作为灰度阈值，计算公式如下：Still referring to FIG. 5 , when the image is under-exposed, the minimum value of the average gray value of the image is M _min , and when the image is over-exposed, the maximum value of the average gray value of the image is M _max . The average value of the minimum value of the average gray value and the maximum value of the average gray value is taken as the gray threshold value, and the calculation formula is as follows:

M_mean＝(M_max+M_min)/2 (3)M _mean = (M _max +M _min )/2 (3)

以灰度阈值作为标准，以此来判断调光元件的调整方向。The grayscale threshold is used as a standard to determine the adjustment direction of the dimming element.

具体地，根据图像的平均灰度值判断光阑的调光方向的过程包括以下步骤：Specifically, the process of judging the dimming direction of the diaphragm according to the average gray value of the image includes the following steps:

判断平均灰度值是否小于灰度阈值，若是，则判定光阑的调光方向为增加通光量方向，否则判定光阑的调光方向为减少通光量方向。It is judged whether the average gray value is less than the gray threshold, and if so, the dimming direction of the diaphragm is determined to be the direction of increasing the light flux; otherwise, the dimming direction of the diaphragm is determined to be the direction of reducing the flux.

步骤五：根据调光方向驱动光阑进行调整，调整后返回步骤一，重新获取图像传感器实时采集的图像。Step 5: Drive the diaphragm to adjust according to the dimming direction, and return to Step 1 after adjustment to re-acquire the image captured by the image sensor in real time.

在本步骤中，根据步骤四所判断的调光方向驱动光阑进行调整，使驱动光阑的步进电机向所判断的调光方向进行移动，并且在光阑调整后返回步骤一，重新获取图像传感器实时采集的图像，重复执行上述步骤，重新开始图像评价。In this step, the diaphragm is driven for adjustment according to the dimming direction determined in step 4, so that the stepping motor driving the diaphragm is moved to the determined dimming direction, and after the diaphragm is adjusted, it returns to step 1 to re-obtain For the images captured by the image sensor in real time, repeat the above steps to restart the image evaluation.

本发明的实时自动调光方法可以让调光系统一直处于修正状态，当出现由于背景光照变化而导致的图像曝光变化时，可以实时对光阑的进光量进行动态调整，以保证图像处于良好的曝光状态。The real-time automatic dimming method of the present invention can keep the dimming system in a state of correction all the time. When the image exposure changes due to changes in the background illumination, the light input amount of the diaphragm can be dynamically adjusted in real time to ensure that the image is in a good condition. exposure status.

进一步地，如图2所示，在开始自动调光后，步骤一至步骤四与图1所示的步骤一致，区别在于：在根据调光方向驱动光阑进行调整之后，紧接着判断是否接收到结束自动调光的指令，若是，则自动调光结束，否则返回步骤一，重新获取图像传感器实时采集的图像，重复执行上述步骤，重新开始图像评价。其中，结束自动调光的指令可以是操作人员输入的指令，也可以是算法满足结束条件时生成的指令，在实际应用中，可根据实际需要选择结束自动调光状态的方式。Further, as shown in FIG. 2 , after the automatic dimming starts, steps 1 to 4 are the same as those shown in FIG. 1 , the difference is that after driving the diaphragm to adjust according to the dimming direction, it is then judged whether the received The instruction to end the automatic dimming, if yes, then the automatic dimming is over, otherwise, go back to step 1, re-acquire the image captured by the image sensor in real time, repeat the above steps, and restart the image evaluation. The instruction to end automatic dimming may be an instruction input by an operator, or an instruction generated when an algorithm satisfies the ending condition. In practical applications, a method for ending the automatic dimming state can be selected according to actual needs.

本发明结合图像的灰度均值与图像对比度这两种评价指标进行测光评价，可以达到实时检测、实时调整的目的，保证了当前图像处于最佳曝光状态。调整时间短，响应效率快，完全适应各种背景光照快速变化的情景。同时，采用本发明实时自动调光方法的成像设备，其将一直处于动态调整的状态，一旦由于背景光照的变化导致图像曝光不佳，成像设备的调光系统将通过实时自动调光方法判断调整方向并进行快速调整，使得成像设备所成的实时图像一直保持着良好的曝光。The invention combines the two evaluation indexes of the grayscale mean value of the image and the image contrast to perform photometric evaluation, which can achieve the purpose of real-time detection and real-time adjustment, and ensure that the current image is in the best exposure state. The adjustment time is short, the response efficiency is fast, and it is fully adaptable to various scenarios where the background light changes rapidly. At the same time, the imaging device using the real-time automatic dimming method of the present invention will always be in a state of dynamic adjustment. Once the image exposure is poor due to changes in the background illumination, the dimming system of the imaging device will judge and adjust through the real-time automatic dimming method. orientation and make quick adjustments so that the live image from the imaging device maintains a good exposure all the time.

本发明所提出的新型的实时自动调光方法具有以下有益效果：The novel real-time automatic dimming method proposed by the present invention has the following beneficial effects:

(1)采用图像的灰度均值与图像对比度相结合的测光策略进行测光评价，可以达到快速调整系统，满足实时调整的条件；(1) The photometric evaluation is carried out by using a photometric strategy that combines the gray mean value of the image and the image contrast, which can achieve a rapid adjustment system and meet the conditions of real-time adjustment;

(2)本发明可以自动的判断调光系统的调整方向，相较于其他的先将系统调整到一端，然后再向另一端搜索最佳位置的调光方法，响应速度更快，效率更高；(2) The present invention can automatically determine the adjustment direction of the dimming system. Compared with other dimming methods that adjust the system to one end first, and then search for the best position to the other end, the response speed is faster and the efficiency is higher. ;

(3)基于八近邻计算的图像对比度的测光评价方法可以应对各种环境，对当前图像的评价更精确，效率更高。(3) The photometric evaluation method of image contrast based on the calculation of eight nearest neighbors can cope with various environments, and the evaluation of the current image is more accurate and efficient.

在另一个实施例中，本发明还提供一种成像设备，该成像设备的结构图如图6所示，在硬件上，该成像设备主要包含前端用于收集图像信息的图像传感器、作为调光元件的光阑和接收图像传感器采集的图像信息以及控制光阑的通光量的处理计算机，其中图像传感器与光阑封闭于带有通光孔的壳体中，封闭的目的是避免环境光的干扰，图像传感器拍摄所需要的光从主光路中折射进入封闭区，经由通光孔入射至图像传感器上，光阑片的作用就是控制这部分光的通光量的。In another embodiment, the present invention also provides an imaging device. The structure diagram of the imaging device is shown in FIG. 6 . In terms of hardware, the imaging device mainly includes an image sensor at the front end for collecting image information, as a dimming device. The diaphragm of the element and the processing computer that receives the image information collected by the image sensor and controls the amount of light passing through the diaphragm. The image sensor and diaphragm are enclosed in a casing with a light-passing hole, and the purpose of sealing is to avoid the interference of ambient light. , the light required by the image sensor for shooting is refracted from the main optical path into the closed area, and incident on the image sensor through the light hole. The function of the diaphragm is to control the amount of light passing through this part of the light.

图像传感器：对当前场景的实时图像进行采集并传输到处理计算机上；Image sensor: collect the real-time image of the current scene and transmit it to the processing computer;

光阑：主要包括光阑片、光阑座和驱动电机，如图7所示，光阑片安装在光阑座上，光阑片线性斩切由通光孔入射至图像传感器上的光线，从而实现线性改变通光孔的通光量。驱动电机用于驱动光阑片的转动，驱动电机由处理计算机上的驱动电机控制板卡控制运动。优选地，驱动电机采用步进电机，可通过DB9标准接口进行供电和通讯，方便联机。Aperture: It mainly includes an aperture sheet, an aperture base and a drive motor. As shown in Figure 7, the aperture sheet is installed on the aperture base, and the aperture sheet linearly cuts the light incident on the image sensor through the light hole. Thereby, the amount of light passing through the light-transmitting hole can be changed linearly. The drive motor is used to drive the rotation of the diaphragm, and the drive motor is controlled by the drive motor control board on the processing computer. Preferably, the drive motor adopts a stepper motor, which can supply power and communicate through the DB9 standard interface, which is convenient for online connection.

处理计算机不仅获取图像传感器采集的图像信息，而且还利用前述实施例所述的实时自动调光方法来动态调整光阑的通光量，从而保证图像传感器采集的图像处于良好的曝光状态。具体地，处理计算机执行以下实时自动调光步骤：The processing computer not only obtains the image information collected by the image sensor, but also dynamically adjusts the light transmission amount of the diaphragm by using the real-time automatic light adjustment method described in the foregoing embodiments, thereby ensuring that the image collected by the image sensor is in a good exposure state. Specifically, the processing computer performs the following real-time automatic dimming steps:

步骤一：获取图像传感器实时采集的当前场景的图像；Step 1: acquire the image of the current scene collected by the image sensor in real time;

步骤二：基于八近邻的计算方法计算图像的对比度；Step 2: Calculate the contrast of the image based on the calculation method of the eight nearest neighbors;

步骤三：判断图像的对比度是否满足图像良好曝光的评价标准，若是，则返回步骤一，重新获取图像传感器实时采集的图像，否则执行步骤四；Step 3: determine whether the contrast of the image meets the evaluation criteria for good image exposure, if so, return to step 1 to re-acquire the image captured by the image sensor in real time, otherwise, perform step 4;

步骤四：计算图像的平均灰度值，并根据平均灰度值判断光阑的调光方向；Step 4: Calculate the average gray value of the image, and judge the dimming direction of the diaphragm according to the average gray value;

步骤五：根据调光方向输出电机控制命令至驱动电机，使驱动电机驱动光阑片进行转动，调整光阑的通光量，调整后返回步骤一，重新获取图像传感器实时采集的图像。在本步骤中，处理计算机根据步骤四所判断的调光方向输出电机控制命令至驱动电机，使驱动电机驱动光阑片向所判断的调光方向进行转动，调整光阑片的通光量，并且在光阑调整后返回步骤一，重新获取图像传感器实时采集的图像，重复执行上述步骤，重新开始图像评价。Step 5: Output the motor control command to the drive motor according to the dimming direction, so that the drive motor drives the diaphragm to rotate, adjusts the amount of light passing through the diaphragm, and returns to step 1 after adjustment to re-acquire the real-time image collected by the image sensor. In this step, the processing computer outputs a motor control command to the drive motor according to the dimming direction determined in step 4, so that the drive motor drives the diaphragm to rotate in the determined dimming direction, adjusts the light transmission amount of the diaphragm, and After the diaphragm is adjusted, go back to step 1, re-acquire the image captured by the image sensor in real time, repeat the above steps, and restart the image evaluation.

需要说明的是，本实施例中处理计算机所执行的实时自动调光步骤与前述实施例所述的实时自动调光方法的步骤相同，故此处不再赘述。It should be noted that the steps of the real-time automatic dimming performed by the processing computer in this embodiment are the same as the steps of the real-time automatic dimming method described in the foregoing embodiments, and thus are not repeated here.

本发明成像设备的调光系统一直处于修正状态，当出现由于背景光照变化而导致的图像曝光变化时，可以实时对光阑的进光量进行动态调整，以保证图像处于良好的曝光状态。The dimming system of the imaging device of the present invention is always in a correction state. When the image exposure changes due to changes in the background illumination, the light input amount of the diaphragm can be dynamically adjusted in real time to ensure that the image is in a good exposure state.

以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

以上所述实施例仅表达了本发明的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变形和改进，这些都属于本发明的保护范围。因此，本发明专利的保护范围应以所附权利要求为准。The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.