共查询到19条相似文献,搜索用时 203 毫秒
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为了减小光栅投影三维测量系统中数字投影仪的非线性响应引起的相位误差,提出了一种提高物体相位测量精度和速度的多频条纹反向相位误差补偿方法。该方法通过投影与最高频率相同且具有特定相移量的补偿相移条纹图,获取相位误差大小相等,符号相反的两幅主值相位图,二者运算后误差得以抵消,与多频法相结合从而得到精确的绝对相位值。采用标准平面对提出的方法进行实验验证,并与最近提出的希尔伯特变换补偿方法以及典型相位补偿方法进行比较。实验结果表明,所提方法能有效提高相位测量的精度和速度。通过对自由曲面以及表面不连续物体进行相位误差补偿,进一步验证了该方法的可行性和有效性。 相似文献
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由于数字光栅投影仪的光强传递函数对于正弦投影条纹的质量以及相位测量精度起着至关重要的作用,本文提出了一种校正光学三维扫描仪光强传递函数的新方法。首先,分析了由于投影仪非线性响应引起的光栅谐波的相位测量误差;然后,通过投影一组不同灰度级的图像,并利用光功率计测出数字投影仪投出图像的亮度。接着,通过分析得到数字投影仪的非线性响应特性曲线,再经过数据处理,即可获得投影仪的光强传递函数;最后,对光强传递函数进行反函数逆变换,得到一个校正后的非正弦光栅,利用投影仪对该光栅的投影即可在被测物体表面上获得一个正弦光栅。数字投影仪对标准平板的测量结果表明,校正前平均误差为0.71 mm,校正后为0.55 mm;对于标准量块的测量,校正前的平均误差为0.62 mm,校正后为0.15 mm。上述结果表明,本文提出的方法可以减小由于系统非线性响应引起的测量误差并提高测量精度。 相似文献
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采用离焦二值条纹投影技术进行三维面形测量可以克服数字投影仪的非线性响应,同时有利于提高投影速度,实现高速测量.通过理论分析和实验研究了采用数字投影仪时二值条纹的基频、高次谐波能量分布与条纹周期的关系.结合相移算法,以相位测量误差为指标,衡量各种二值条纹的性能.研究结果表明:在周期小时,罗奇光栅和二维误差扩散算法生成的二值条纹离焦后能产生正弦性较好的条纹;在采用满周期等间隔奇数次相移时,罗奇光栅离焦能获得更高的测量准确度;在周期大时,采用优化脉宽调制方法得到的二值光栅离焦测量准确度最高.研究结果为离焦条纹投影三维测量中二值光栅的选择提供了依据. 相似文献
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投影仪散焦技术克服了实时光栅投影三维测量中的投影仪非线性问题,但散焦产生的高次谐波会大大降低散焦光栅的正弦性,带来明显的测量误差。提出了采用"S"形扫描Sierra Lite抖动算法生成二值抖动光栅,较大地改善了散焦后光栅的正弦性,将该抖动技术生成的散焦光栅用于传统的相移算法,基于投影仪散焦投影,得到用于三维测量的绝对相位信息。仿真结果验证了该方法的有效性,改善了散焦光栅的正弦性,提高了相位质量。实际测量实验与仿真结果相一致。与已有的Bayer有序抖动和Floyd-Steinberg抖动生成的光栅相比,所提算法运算速度快,生成光栅正弦性较好,更加适用于散焦投影测量。 相似文献
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Gamma-distorted fringe image modeling and accurate gamma correction for fast phase measuring profilometry 总被引:1,自引:0,他引:1
In fast phase-measuring profilometry, phase error caused by gamma distortion is the dominant error source. Previous phase-error compensation or gamma correction methods require the projector to be focused for best performance. However, in practice, as digital projectors are built with large apertures, they cannot project ideal focused fringe images. In this Letter, a thorough theoretical model of the gamma-distorted fringe image is derived from an optical perspective, and a highly accurate and easy to implement gamma correction method is presented to reduce the obstinate phase error. With the proposed method, high measuring accuracy can be achieved with the conventional three-step phase-shifting algorithm. The validity of the technique is verified by experiments. 相似文献
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针对投影仪标定方法中存在畸变及倾斜投影引起条纹周期、条纹级数变化的问题,提出一种单周期条纹双四步相移投影仪的标定方法.设计生成横向和纵向各两组单周期条纹图像,经投影仪投影到带有圆形标识的标定板上,相机同步采集标定板图像,叠加由双四步相移获得的两幅相位主值图,对叠加相位主值图相位展开,利用展开的绝对相位值计算投影仪像素坐标值,最终将投影仪标定转换为成熟的相机标定.实验结果表明:仿真投影仪标定实验准确度的最大重投影误差约为0.4pixel,均方根误差为0.132 96pixel;实际投影仪标定实验准确度的最大反投影误差约为0.46pixel,均方根误差为0.143 12pixel;实验结果与仿真结果的最大反投影误差相差15%,均方根误差相差7.6%.与现有的采用三频相位展开进行投影仪标定的方法相比,投影光栅图像数可减少8幅.该方法改善了现有投影仪标定方法的不足,标定准确度和标定效率均得到提高. 相似文献
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Fringe projection profilometry (FPP) is a widely used three-dimensional profile measurement technique. One vital step in this technique is calibration, which determines the system accuracy. The least-squares method, because of its flexibility and simplicity, is commonly used in system calibration for FPP. However, calibration results are affected by the nonlinear gamma of the projector and projection fringe cycle broadening. This paper proposes a new look-up table (LUT) generation method by analyzing the differences between the real and ideal unwrapped phases. The aforementioned problems could then be solved after the phase error is compensated by the LUT. Finally, the validity of the proposed method is demonstrated through experiments, and the accuracy reaches 0.02 mm. 相似文献
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Fringe projection profilometry is widely used for three-dimensional shape measurement. In an oblique-angle projection, the fringe cycle is broadened on the reference plane. Phase errors are mainly caused by the nonlinear gamma of the projector and fringe cycle broadening. This study describes a phase error compensation method to eliminate these phase errors. A look-up table that stores phase errors is constructed for phase error compensation. Based on it, a new height equation is proposed. The experimental results show that the proposed method can compensate for the phase errors of the fringe projection profilometry, thereby improving the measurement accuracy significantly. 相似文献
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This paper presents an analysis of error compensation using a newly modified two-step triangular-pattern phase-shifting measurement method, developed to reduce periodic measurement errors due to gamma nonlinearity and defocus of the projector and camera. Experimental analysis revealed that a trade-off is necessary in choosing a higher minimum projector input intensity to use the more linear region of input-to-output intensity mapping, and a lower minimum input intensity for greater dynamic range of input intensity. The modified two-step triangular-pattern phase-shifting method performs two-step triangular-pattern phase-shifting twice, the second time with an initial phase offset of one-eighth of the pitch, and generates the three-dimensional object height distribution by averaging the two obtained object-height distributions. The modified two-step triangular-pattern phase-shifting method consistently had higher measurement accuracy than the unmodified method. Errors were reduced by 23.4% at the midrange of depth using an input intensity value of 40, which yielded the highest measurement accuracy and up to 64% and 54% at small and large depths, respectively. 相似文献
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Gamma畸变的相位误差模型与Gamma标定技术 总被引:3,自引:2,他引:1
Gamma畸变是数字相移测量技术的主要误差源。以通用的均匀步长相移技术为对象,分析了Gamma畸变对相位计算的影响,建立了相位误差与谐波系数的关系模型,证明了各阶谐波系数在Gamma值影响下的递推公式,进而提出了基于离散傅里叶变换的Gamma标定技术。基于此Gamma标定值,通过Gamma预矫正降低相位误差。实验结果表明,标定的Gamma值在整个像平面具有较强的稳定性,Gamma矫正后使相位误差减小了77.5%,在曲面测量的结果中,水波纹明显得到抑制,曲面质量得以提高。 相似文献
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系统参数的标定是结构光三维测量系统工作的基础,且参数标定的精度直接影响测量的精度,其中投影仪目前还存在标定过程复杂、精度较低等问题。为解决该问题,通过投影一组圆阵图案到一块本身带有特征圆的平板上,并由摄像机拍摄;基于二维射影变换理论,通过误差补偿法建立投影仪图像坐标和摄像机图像坐标的对应关系,利用该对应关系计算获取标定点的投影仪图像坐标;以标定点的两组图像坐标和世界坐标为初始值,使用非线性算法对系统进行全参数整体优化,完成系统的标定。实验验证了系统标定误差最大值小于0.05 mm,误差均方根小于0.03 mm,结果表明该方法标定过程简单,能够有效地提高标定精度,具有较广的适用性。 相似文献
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The nonlinear response of the experimental system and the saturation of fringe patterns can induce the fluctuating phase error in the projection grating phase-shifting profilometry. Two major factors of the fluctuating phase error are discussed by simulation. The fluctuating phase error caused by the nonlinear response of the system is four times the frequency of the fringe pattern when the conventional four-frame phase extracting algorithm is used. However, such error can be decreased by five-frame algorithm. On the other hand, the fluctuating phase error caused by the fringe saturation is five times the frequency of the fringe pattern by using conventional five-frame phase extracting algorithm. A novel phase recovering algorithm is used to decrease the phase error caused by the saturation. Furthermore, the applicability range of the proposed phase recovering algorithm is analyzed by simulation and experiments with different saturation degree of the fringe pattern and nonlinearity of the measurement system. 相似文献