Optical trapping is widely used to manipulate a small-sized particle freely suspended in the isotropic fluidic domain. Trapping is done by means of optical forces developed by conversing light beam. The active gradient forces, ${\text{F}}_{\text{g}\text{r}\text{a}\text{d}}$ depends upon parameters like light wavelength, particle size, and refractive index of medium and particle. The viscous drag forces, ${\text{F}}_{\text{v}\text{i}\text{s}\text{c}}$ depends upon parameter like viscosity of fluid, relative velocity of particle with respect to medium. The necessary condition for particle trapping is to maintain ${\text{F}}_{\text{g}\text{r}\text{a}\text{d},\text{m}\text{a}\text{x}}$ > ${\text{F}}_{\text{v}\text{i}\text{s}\text{c}},$ $({\text{F}}_{\text{g}\text{r}\text{a}\text{d},\text{m}\text{a}\text{x}}\text{i}\text{s}\text{a}\text{m}\text{a}\text{x}\text{i}\text{m}\text{u}\text{m}\text{v}\text{a}\text{l}\text{u}\text{e}\text{o}\text{f}{\text{F}}_{\text{g}\text{r}\text{a}\text{d}})$. In this paper, a graphical approach is applied to predetermine the value of specific parameter such as relative velocity of particle and light wavelength under the necessary condition for optical trapping, while keeping other parameters are as fixed. Software simulation is performed with set of relative velocities on polystyrene small-sized particle in water channel to validate the graphical approach.

光学阱被广泛用于操纵自由悬浮在各向同性流体域中的小尺寸颗粒。诱捕是通过转换光束产生的光学力完成的。主动梯度力${\text{F}}_{\text{G}\text{[R}\text{一种}\text{d}}$取决于参数，例如光波长，粒径以及介质和粒子的折射率。粘性阻力${\text{F}}_{\text{v}\text{一世}\text{s}\text{C}}$取决于参数，例如流体的粘度，粒子相对于介质的相对速度。捕获粒子的必要条件是保持${\text{F}}_{\text{G}\text{[R}\text{一种}\text{d}，\text{米}\text{一种}\text{X}}$ > ${\text{F}}_{\text{v}\text{一世}\text{s}\text{C}}，$ $（{\text{F}}_{\text{G}\text{[R}\text{一种}\text{d}，\text{米}\text{一种}\text{X}}\text{一世}\text{s}\text{一种}\text{米}\text{一种}\text{X}\text{一世}\text{米}\text{ü}\text{米}\text{v}\text{一种}\text{升}\text{ü}\text{Ë}\text{Ø}\text{F}{\text{F}}_{\text{G}\text{[R}\text{一种}\text{d}}）$。在本文中，采用一种图形方法来预先确定特定参数的值，例如在光学陷波的必要条件下，粒子的相对速度和光波长，同时保持其他参数不变。使用一组相对速度对水通道中的聚苯乙烯小颗粒进行软件仿真，以验证图形方法。