Dear Henrick, thank you for your kind helps.

Is there a way to make the body of revolution with a 2D image(eg. a triangle into a cone by rotation)?

By this, I meant to talk about a solid of revolution(eg. rotating a triangle about its base line)(Sorry for my short Eng). And working on the single-slit problem, I got the solution of the amplitude of the light in integral form and tried to make it in a plot in order to check if it's right and how several variables affect the shape of the spectrum. What I wanted to ask was this, but I think I didn't make it clear. Sorry for that.

The solution I got for single-slit problem is:

Leng[_L,_u,_v,_r]:=Sqrt[(u+r)^2 +v^2 +L^2];

Amp[_L,_d,_k,_x]:=Integrate[Sin[k Leng[L, u, v, r]]/Leng[L,u,v,r],
{u,v} \[Element] Circle[{0, 0}, 0.5 d]]/ 
Integrate[1/Leng[L,u,v,r], {u,v} \[Element] Circle[{0,0},0.5d]];

Manipulate[Plot[Amp[L,d,k,x]^2, {x,-8,8}, PerformanceGoal->"Quality", PlotPoints->40,
ImageSize->Large], {L, 1, 3}, {d, 10^-6, 3 10^-6}, {k, 2Pi/3 10^7, 0.25Pi 10^7}]

However, to calculate the Plot3D, it takes too much running time.

You are probably talking about doing it like so:

intens[L_, d_, \[Lambda]_, x_] := 
  1/(L^2 + (x - 0.5 d)^2) + 
   1/(L^2 + (x + 0.5 d)^2) + (2 Cos[
       2 Pi Abs[
          Sqrt[L^2 + (x - 0.5 d)^2] - 
           Sqrt[L^2 + (x + 0.5 d)^2]]/\[Lambda]])/(Sqrt[
       L^2 + (x - 0.5 d)^2] Sqrt[L^2 + (x + 0.5 d)^2]);
Manipulate[
 Plot3D[intens[L, d, \[Lambda], x], {x, -5, 5}, {L, 1, 3}, 
  PlotRange -> All, PerformanceGoal -> "Quality", PlotPoints -> 40, 
  ImageSize -> Large, MeshFunctions -> {#3 &}, 
  ColorFunction -> "TemperatureMap"],
 {d, 10^-6, 3 10^-6}, {\[Lambda], 3 10^-7, 8 10^-7}]

Yes, generating such a Plot3D within Manipulate is painfully slow. But this is not very surprising, because a lot of calculation needs to be done. I do not know what you mean by:

Is there a way to make the body of revolution with a 2D image(eg. a triangle into a cone by rotation)?

One standard way if calculations need to be done faster is to use Compile:

cIntens = 
  Compile[{{L, _Real}, {d, _Real}, {\[Lambda], _Real}, {x, _Real}}, 
   Module[{pls, min, sqrpls, sqrmin},
    pls = L^2 + (0.5` d + x)^2;
    min = L^2 + (-0.5` d + x)^2;
    sqrpls = Sqrt[pls];
    sqrmin = Sqrt[min];
    1/min + 1/pls + 2 Cos[2 Pi/\[Lambda] Abs[sqrmin - sqrpls]]/(sqrmin sqrpls)], 
   RuntimeOptions -> "Speed", CompilationTarget -> "C"];

Manipulate[
 Plot3D[cIntens[L, d, \[Lambda], x], {x, -5, 5}, {L, 1, 3}, 
  PlotRange -> All, PerformanceGoal -> "Quality", PlotPoints -> 40, 
  ImageSize -> Large, MeshFunctions -> {#3 &}, 
  ColorFunction -> "TemperatureMap"],
 {d, 10^-6, 3 10^-6}, {\[Lambda], 3 10^-7, 8 10^-7}]

This is still somewhat slow, but much better. If you do not have a C-compiler installed on you system, then just leaf the option CompilationTarget -> "C" away.

Dear Wonseok Lee, glad to help!

But what's the difference between ...

With Table[ ... ] the values of just a single line of pixels is calculated, and with ConstantArray[Table[ ... ], 300] this line is simply replicated 300 times. DensityPlot can not know that all lines are identical and so the same sequence of calculations is done for every line.

Actually, the spectrum graph of the function mentioned upon doesn't respond smoothly as I control the slide by Manipulate function ...

This probably can be improved by using the option PerformanceGoal within Plot:

Plot[   ...   , PerformanceGoal -> "Quality"]

Hello Wonseok Lee,

I guess this effect is due to insufficient resolution of your DensityPlot. You can fix this using the option PlotPoints, e.g.:

DensityPlot[    ...      , PlotPoints -> 50]

then the whole image looks a bit different (i.e. more correct), but Manipulate works very slowly. An alternative way (my suggestion) might be to use Image, e.g.:

Manipulate[
 ImageAdjust@Image[ConstantArray[
   Table[1/(L^2 + (x - 0.5 d)^2) + 
     1/(L^2 + (x + 0.5 d)^2) + (2 Cos[
         2 Pi Abs[
            Sqrt[L^2 + (x - 0.5 d)^2] - 
             Sqrt[L^2 + (x + 0.5 d)^2]]/\[Lambda]])/(Sqrt[
         L^2 + (x - 0.5 d)^2] Sqrt[L^2 + (x + 0.5 d)^2]), {x, -8, 
     8, .005}], 300]], {L, 1, 3}, {d, 10^-6, 3 10^-6}, {\[Lambda], 
  3 10^-7, 8 10^-7}]

Regards -- Henrik