function pd() 
{
  if(document.forms[0].fsource.value=="viz nize") {    document.forms[0].fsource.value = ""; }
  if(document.forms[0].dsource.value=="viz nize") {    document.forms[0].dsource.value = ""; }

  var err = 0;

  if((document.forms[0].fsource.value=="")&&(document.forms[0].dsource.value==""))//zadáno nic
  {									
    alert("Pro výpočet je nutné vyplnit pole \"obrazová vzdálenost\" nebo \"průměr dírky\"!");
    document.forms[0].fsource.focus();	    
    err = 1;
  }	
  else
  {
    if(document.forms[0].dsource.value=="")
    { 
      if(!kontrola(document.forms[0].fsource, "obrazová vzdálenost (mm)", "d")){ err=1; } 
      else { var fs=desetinnacarka(document.forms[0].fsource); }
    } 
    else
    { 
      if(!kontrola(document.forms[0].dsource, "průměr dírky (mm)", "d")){ err=1; } 
      else { var ds=desetinnacarka(document.forms[0].dsource); }
    } 
  }

  if(err==0)
  { 
    if(!kontrola(document.forms[0].lsource, "vlnová délka světla (mm)", "d")){ err=1; } 
    else { var ls=desetinnacarka(document.forms[0].lsource); }
  } 

  if(err==0)
  { 
    if(!kontrola(document.forms[0].k1, "konstanta pro vzorec 1", "d")){ err=1; } 
    else { var k1=desetinnacarka(document.forms[0].k1); }
  } 

  if(err==0)
  { 
    if(!kontrola(document.forms[0].k2, "konstanta pro vzorec 2", "d")){ err=1; } 
    else { var k2=desetinnacarka(document.forms[0].k2); }
  } 

  if(err==0)
  { 
    if(!kontrola(document.forms[0].k3, "konstanta pro vzorec 3", "d")){ err=1; } 
    else { var k3=desetinnacarka(document.forms[0].k3); }
  } 

/***********/	
  if((document.forms[0].dsource.value == "")&&(err==0))		//VÝPOČET průměru
  {									
    document.forms[0].f1.value = fs;
    document.forms[0].d1.value = document.forms[0].k1.value * Math.sqrt(fs*ls);
    document.forms[0].c1.value = document.forms[0].f1.value/document.forms[0].d1.value;
    document.forms[0].n1.value = Math.pow((document.forms[0].c1.value/22),2);

    document.forms[0].f2.value = fs;
    document.forms[0].d2.value = 2*Math.sqrt(ls*fs*document.forms[0].k2.value);
    document.forms[0].c2.value = document.forms[0].f2.value/document.forms[0].d2.value;
    document.forms[0].n2.value = Math.pow((document.forms[0].c2.value/22),2);

    document.forms[0].f3.value = fs;
    document.forms[0].d3.value = Math.sqrt(fs/document.forms[0].k3.value);
    document.forms[0].c3.value = document.forms[0].f3.value/document.forms[0].d3.value;
    document.forms[0].n3.value = Math.pow((document.forms[0].c3.value/22),2);
		
    document.forms[0].f4.value = fs;
    document.forms[0].d4.value = Math.sqrt(fs)/25;
    document.forms[0].c4.value = document.forms[0].f4.value/document.forms[0].d4.value;
    document.forms[0].n4.value = Math.pow((document.forms[0].c4.value/22),2);

    document.forms[0].dsource.value = "viz nize";
  }	

  if((document.forms[0].fsource.value == "")&&(err==0))			//VÝPOČET vzdálenosti
  {											
    document.forms[0].f1.value = (Math.pow((ds/document.forms[0].k1.value),2))/ls;
    document.forms[0].d1.value = ds;
    document.forms[0].c1.value = document.forms[0].f1.value/document.forms[0].d1.value;
    document.forms[0].n1.value = Math.pow((document.forms[0].c1.value/22),2);

    document.forms[0].f2.value = Math.pow((ds/2),2)/(ls*document.forms[0].k2.value); 
    document.forms[0].d2.value = ds;
    document.forms[0].c2.value = document.forms[0].f2.value/document.forms[0].d2.value;
    document.forms[0].n2.value = Math.pow((document.forms[0].c2.value/22),2);

    document.forms[0].f3.value = Math.pow(ds,2)*document.forms[0].k3.value;   
    document.forms[0].d3.value = ds;
    document.forms[0].c3.value = document.forms[0].f3.value/document.forms[0].d3.value;
    document.forms[0].n3.value = Math.pow((document.forms[0].c3.value/22),2);

    document.forms[0].f4.value = Math.pow((ds*25),2);   
    document.forms[0].d4.value = ds;
    document.forms[0].c4.value = document.forms[0].f4.value/document.forms[0].d4.value;
    document.forms[0].n4.value = Math.pow((document.forms[0].c4.value/22),2);

    document.forms[0].fsource.value = "viz nize";
  }	
}