thinLens.java
// Modification history
// May 31,1997 fixed bug when object located at focus point
// May 22,1997 add paraxial ray option for mirror
// Feb 21,1997 major modification, almost rewritten the whole code
// try without frame => very slow for netscape
// Nov. 3, 1996 impletemt double buffering
//-----------------------------------------------------
// written by Fu-Kwun Hwang
// I hope that you enjoy this applet
// Suggestions? E-mail to hwang@phy03.phy.ntnu.edu.tw
//-----------------------------------------------------
import java.awt.*;
public class thinLens extends java.applet.Applet{
String buttonText="start";
String windowTitle="Thin Lens demonstration by Fu-Kwun Hwang(1996)";
int windowWidth = 600;
int windowHeight = 350;
LensWindow m;
int windowCount=0;
Color bgColor=new Color(0xC8,0xDF,0xD0);
String rts,STR[]={"Reset","p","q","f","m","lens","mirror","Paraxial"};
public void init() {
setBackground(bgColor);
for(int i=0;i
if((rts=getParameter(STR[i]))!=null)
STR[i]=new String(rts);
}
String str;
// get parameters
if((str=getParameter("buttonText"))!=null)
buttonText=str;
if((str=getParameter("windowTitle"))!=null)
windowTitle=str;
if((str=getParameter("windowWidth"))!=null)
windowWidth=Integer.parseInt(str);
if((str=getParameter("windowHeight"))!=null)
windowHeight=Integer.parseInt(str);
if((str=getParameter("autoStart"))!=null){
m = new LensWindow(windowTitle, true,STR);
go();
}
add(new Button(buttonText));
}
private void go(){
m.resize(windowWidth,windowHeight);
m.show();
m.start();
}
public boolean action(Event e,Object arg) {
if (e.target instanceof Button &&
((String)arg).equals(buttonText)) {
m = new LensWindow(String.valueOf(++windowCount)+":"+
windowTitle, true,STR);
}
go();
return true;
}
//allow the applet to also run as an application.
public static void main(String args[]) {
new thinLens().begin();
}
private void begin() {
m = new LensWindow(windowTitle, false,STR);
go();
}
}
class LensWindow extends Frame {
boolean is_applet;
boolean is_lens=true;
int yOffset=30;
String STR[];
LensWindow(String title, boolean isapp,String[] s){
super(title);
is_applet=isapp;
setBackground(Color.lightGray);
STR=s;
init();
}
public void start(){
reset();
repaint();
// lMirror.hide();
cThin.hide();//disable();
}
public boolean handleEvent(Event e) {
if (e.id == Event.WINDOW_DESTROY) {
hide();
removeAll();
dispose();
if(!is_applet) System.exit(0);
}
return super.handleEvent(e);
}
TextField textP,textQ,textF,textM;//,textR;
// Label lMirror;
Checkbox cThin;
Button type;
Dimension area;
int xc,yc;
double scale=10.;
void init(){
Panel p=new Panel();
// p.add(textR=new TextField(" X , Y",6));
p.add(new Label(STR[1]));
p.add(textP=new TextField("10.",2));
p.add(new Label(STR[2]));
p.add(textQ=new TextField("10.",2));
p.add(new Label(STR[3]));
p.add(type=new Button("+"));
p.add(textF=new TextField("5.",2));
p.add(new Label(STR[4]));
p.add(textM=new TextField("1.",2));
Choice c;
p.add(c=new Choice());
c.addItem(STR[5]);
c.addItem(STR[6]);
p.add(new Button(STR[0]));
// p.add(lMirror=new Label());
p.add(cThin=new Checkbox(STR[7]));
cThin.setState(true);
cThin.show();
thinMirror=cThin.getState();
add("North",p);
show();
}
boolean thinMirror=true;
public boolean action(Event ev, Object arg) {
if (ev.target instanceof Button) {
String label = (String)arg;
if(label.equals(STR[0]))reset();
else{
if(label.equals("+")) type.setLabel("-");
else if(label.equals("-")) type.setLabel("+");
lf*=-1.;
repaint();
}
}else if( ev.target instanceof TextField){
String label = (String)arg;
double value;
value=Double.valueOf(label).doubleValue();
if(ev.target==textP)
textInput(1,value);
else if(ev.target==textQ)
textInput(2,value);
else if(ev.target==textF)
textInput(3,value);
else if(ev.target==textM)
textInput(4,value);
repaint();
}else if(ev.target instanceof Choice){
String label = (String)arg;
if(label.equals(STR[5])){
is_lens=true;
// lMirror.hide();
cThin.hide();//disable();
}else{
is_lens=false;
// lMirror.show();
cThin.show();//enable();
show();
}
lshow();
repaint();
}else if(ev.target instanceof Checkbox){
thinMirror=cThin.getState();
lshow();
repaint();
}
return true;
}
public void reset() {
area=size();
area.height-=yOffset;
xc=area.width/2;
yc=area.height/2;
double ff=10.*scale;
type.setLabel("+");
textF.setText(Double.toString(ff));
linit(xc,yc,(int)(0.7*yc),ff);
xc-=(int)(2.*lf); // initial object position
yc=yc*3/4;
repaint();
}
boolean objectmove=false,rightClick=false,moveLine=false;
int xp,yp;// vertical reference line
public boolean mouseDown(Event e, int x, int y){
y-=yOffset;
if(Math.abs(x-xp)<5)moveLine=true;
else if(!lmouseDown(x,y)){
if(Math.abs(x-xc)<5 ){
xc=x;
yc=y;
repaint();
objectmove=true;
}
}
if(e.modifiers==Event.META_MASK)//"Right Click, ";
rightClick=true;
return true;
}
public boolean mouseDrag(Event e, int x, int y){
y-=yOffset;
if(working)return true;
if(lmouseDrag(x,y)){
if(rightClick)xc=lxc-ox;// also move objects
repaint(); // change lens
}else if(objectmove){ // move object
if(!is_lens && x>lxc II lh
xc=x;
yc=y;
if(rightClick)lxc=xc+side*ox;// also move lens
writeXY(x,y);
repaint();
}else if (moveLine){
xp=x;
yp=y;
writeXY(x,y);
repaint();
}
return true;
}
public boolean mouseUp(Event e, int x, int y){
y-=yOffset;
lmouseUp(x,y);
objectmove=false;
rightClick=false;
moveLine=false;
repaint();
return true;
}
public boolean mouseMove(Event evt, int x, int y){
y-=yOffset;
if(working)return true;
if(!objectmove)writeXY(x,y);
repaint();
return true;
}
String msg=" X , Y";
private void writeXY(int x, int y){
//textR.setText(
msg=
Double.toString((int)(10.*(lxc-x)/scale)/10.)+
","+
Double.toString((int)(10.*(lyc-y)/scale)/10.);
}
public boolean mouseExit(Event evt, int x, int y){
y-=yOffset;
// textR.setText(" X , Y");
msg=" X , Y";
repaint();
return true;
}
public void textInput(int type,double value){
switch (type) {
case 1: // P
xc=lxc-(int)(value*scale);
break;
case 2: // Q
xc=lxc-(int)(1./(1./lf-1./(scale*value)));
break;
case 3: // F
lf=value*scale;
break;
case 4: // M
xc=lxc-(int)(Math.abs((1.-1./value)*lf));
break;
}
}
Dimension offDimension;
Image offImage;
Graphics g;
public void paint(Graphics gs){
update(gs);
}
private static boolean working=false;
public void update(Graphics gs){
working=true;
area=size();
area.height-=yOffset;
if ( (g == null) // if resize window
II (area.width != offDimension.width)
II (area.height != offDimension.height) ) {
offDimension = area;
offImage = createImage(area.width, area.height);
g = offImage.getGraphics();
xp=area.width-50;
reset();
}
//Erase the previous image.
g.setColor(getBackground());
g.fillRect(0, 0, area.width, area.height);
g.setColor(Color.black);
g.drawString(msg,5,15+yOffset);
g.drawLine(0,lyc,area.width,lyc);
drawGrid(g);
drawRay(g);
lshow();
g.setColor(Color.white);
g.drawLine(xp,30,xp,area.height-30);
if(moveLine)g.drawLine(xp-15,yp,xp+15,yp);
gs.drawImage(offImage, 0, yOffset, this);
working=false;
}
private void drawGrid(Graphics g){
g.setColor(Color.gray);
int i,j;
for(i=lxc,j=0;i>0;j++,i=lxc-(int)(j*scale))
g.drawLine(i,lyc-2,i,lyc+2);
for(i=lxc,j=0;i
g.drawLine(i,lyc-2,i,lyc+2);
//g.setColor(Color.black);
}
private void writeText(TextField obj,double value){
value=(double)((int)(10.*value/scale))/10.;
//formated output, keep same digits outputs after .
obj.setText(Double.toString(value));
}
int ox,oy,side; // object position
double ix,iy; // image position
double magnify;
boolean inrange,normal;
public void drawRay(Graphics g){
if(lxc>xc){
ox=lxc-xc;
side=1;
}else{
ox=xc-lxc;
side=-1;
}
oy=lyc-yc;
if(ox==lf){// located at focus point
normal=false;
textQ.setText("Inf");
}else {
normal=true;
ix=1./(1./lf-1./ox);
writeText(textQ,ix);
}
magnify=-ix/ox;
// write P,Q,F
writeText(textP,Math.abs(lxc-xc));
writeText(textF,Math.abs(lf));
textM.setText(d2String(magnify));
int x1,y1,x2,y2; // ray paths
x1=lxc-side*ox;
y1=lyc-oy;
if(normal)iy=magnify*oy;
else{// May 31,1997
double mag2=-100.*magnify/Math.abs(magnify);
iy=-mag2*oy;
ix=mag2*ox;
}
y2=lyc-(int)iy;
//draw object
g.setColor(Color.blue);
drawit(g,x1,lyc,oy);
if(lh>Math.abs(iy))inrange=true;
else inrange=false;
if(is_lens){// lens
x2=lxc+side*(int)ix;
g.drawLine(x1,y1,lxc,y1); //1-1 ����J�g��
if(magnify<0){
g.drawLine(lxc,y1,x2,y2); //1-2
g.drawLine(x1,y1,x2,y2); //2 ��L�z�褤��
if(inrange){
g.drawLine(x1,y1,lxc,y2); //3-1 ��L�J�I�J�g��
g.drawLine(lxc,y2,x2,y2); //3-2 ����D�b
}
g.setColor(Color.blue);
}else{
if(lf>0){ // converging lens
g.drawLine(lxc,y1,lxc+2*side*(int)lf,lyc+oy); //1-2
g.drawLine(x1,y1,lxc-side*(int)ix,lyc+(int)iy); //2-1
if(inrange) {
g.drawLine(x1,y1,lxc,lyc-(int)iy); //3-1
g.drawLine(lxc,y2,lxc+2*side*(int)lf,y2); //3-2
}
g.setColor(Color.green);
g.drawLine(x1,y1,x2,y2); //2-2
g.drawLine(lxc,y1,x2,y2); //1-3
if(inrange) g.drawLine(lxc,y2,x2,y2); //3-3
}else{ // diverging lens
g.drawLine(lxc,y1,lxc-2*side*(int)lf,lyc-3*oy); //1-2
g.drawLine(x1,y1,lxc+side*ox,lyc+(int)oy); //2
if(inrange){
g.drawLine(x1,y1,lxc,y2); //3-1
g.drawLine(lxc,y2,lxc-2*side*(int)lf,y2); //3-2
}
g.setColor(Color.green);
g.drawLine(lxc,y1,lxc+side*(int)lf,lyc); //1-3
if(inrange) g.drawLine(lxc,y2,lxc+side*(int)ix,y2); //3-3
}
}
}else{// mirror
double angle=Math.asin(oy/lr);
double dw=0.,dw2;
int xx,xx2,yy;
x2=lxc-(int)ix;
if(!thinMirror)dw=lr*(1.-Math.cos(angle));
xx=lxc-(int)dw;
angle*=2.;
if(lf>0){// concave mirror �W����
boolean within;
g.drawLine(x1,y1,lxc,lyc); //2-1 �� �q�L �譱����
yy=lyc-(int)(lr*oy/(lr-ox));
double mm=iy/(-ix+lr),xt=0.;
if(!thinMirror) xt=lr*(1./Math.sqrt(1.+mm*mm)-1.);
if( (within=(Math.abs(mm*(xt+lr))
g.drawLine(x1,y1,lxc+(int)xt,yy=lyc-(int)(mm*(xt+lr)));//4-1�����J�g�譱
xx2=lxc+(int)(iy*(lf-ox)/oy-lf);
if(oy>0)side=1;else side=-1;
if(oy*iy>0){//�깳
if(!thinMirror)g.drawLine(x1,y1,lxc-(int)lr,lyc);//4-2 �����J�g
else g.drawLine(lxc-(int)(2.*lf),lyc,lxc,yy=lyc-(int)(iy*2.*lf/(2.*lf-ix)));
g.drawLine(lxc,lyc,lxc-2*ox,lyc+2*oy);//2-2 ��ߤϮg
g.setColor(Color.green);
g.drawLine(lxc,lyc,x2,y2);//2-3
g.drawLine(lxc+(int)xt,yy,x2,y2);//2-1
g.setColor(Color.blue);
g.drawLine(x1,y1,xx,y1);//1-1 ����J�g��
if(!thinMirror)g.drawLine(xx,y1,lxc-(int)lr,lyc-oy+(int)(Math.tan(angle)*(lr-dw)));//1-2
g.setColor(Color.green);
if(!thinMirror){
g.drawLine(xx,y1,lxc-(int)ix,lyc-oy-(int)(Math.tan(angle)*(-ix+dw)));//1-3
g.setColor(Color.gray);
g.drawLine(lxc-(int)lf,lyc,x2,y2);
}else{
g.drawLine(lxc,y1,x2,y2);
g.drawLine(lxc,yy,x2,y2);
g.setColor(Color.blue);
g.drawLine(lxc,y1,lxc-(int)lf,lyc);
}
}else{//�깳
g.drawLine(lxc,lyc,x2,y2);//2-2 �譱����--��
if(within&&!thinMirror)g.drawLine(x1,y1,x2,y2);//4-2
g.drawLine(x1,y1,xx,y1);//1-1 ����J�g��
if(!thinMirror){
g.drawLine(xx,y1,lxc-(int)ix,lyc-oy+side*(int)(Math.abs(Math.tan(angle))*(ix-dw)));//1-2
g.setColor(Color.gray);
}
g.drawLine(xx,y1,lxc,yy=lyc+(int)(lf*iy/(ix-lf)));
g.drawLine(x2,y2,lxc,yy);
if(inrange){
g.drawLine(x1,y1,lxc,yy=lyc+(int)(lf*oy/(ox-lf)));//3-1
g.drawLine(x2,y2,lxc,yy);//3-2
}
}
if(!thinMirror){
g.setColor(Color.white);
g.drawLine(lxc-(int)lr,lyc,xx,y1);
}
}else{// convex mirror
dw2=lr*(1.-Math.cos(Math.asin(oy/(lr+ox))));
yy=lyc+(int)((2*lf+dw2/2.)*oy/(ox-2.*lf));
g.drawLine(x1,y1,xx=lxc+(int)dw2,yy);//2�����g�V�譱
g.drawLine(x1,y1,lxc,lyc);//3 �q�L�譱����
g.drawLine(lxc-2*ox,lyc+2*oy,lxc,lyc);//3-1
g.setColor(Color.green);
if(!thinMirror)g.drawLine(lxc+(int)dw2,yy,lxc+(int)lr,lyc);//2-1
else g.drawLine(xx,yy,lxc-(int)(2*lf),lyc);
g.drawLine(lxc,lyc,x2,y2);//3-2
g.setColor(Color.blue);
g.drawLine(x1,y1,xx=lxc+(int)(dw),y1);//1-1 ����J�g��
if(!thinMirror)g.drawLine(lxc+(int)(dw+lf),y1+(int)(lf*Math.tan(angle)),xx,y1);
else g.drawLine(lxc,(int)y1,lxc+(int)(2*lf),y1-2*oy);
if(!thinMirror){
g.setColor(Color.white);
g.drawLine(lxc+(int)(2*dw-lr),2*y1-lyc,lxc-(int)(2*lf),lyc);//�q�L�J�I
}
g.setColor(Color.green);
if(!thinMirror){
g.drawLine(xx,y1,lxc+(int)(dw-lf),y1-(int)(lf*Math.tan(angle)));
g.setColor(Color.gray);
}
g.drawLine(lxc,y1,lxc-(int)lf,lyc);
}
}
if(oy*iy>0)g.setColor(Color.green);
else g.setColor(Color.darkGray);
drawit(g,x2,lyc,(int)iy); // draw image
}
String d2String(double d){
float d2=(float)((int)(100.*d)/100.);
String str=String.valueOf(d2);
if(str.indexOf(".")==-1)str+=".0";
return str;
}
private void drawit(Graphics g,int x,int y,int height){
// for object and image
int x1,y1,width=2,sign=1;
x1=x-width/2;
if(height<0){
sign=-1;
y1=y;
}else y1=y-height;
g.fillRect(x1,y1,width,sign*height);
y1=y-height;
width=2*width;
sign*=2;
// draw hats
g.drawLine(x,y1,x+width,y1+sign*width);
g.drawLine(x,y1,x-width,y1+sign*width);
}
int lxc,lyc,lh; // (xc,yc):center position, h:height of lens
double lr,lf; // focusLength*2;
int lwidth; // half/quater width of lens
public void linit(int x, int y,int hi,double fi){
lxc=x; lyc=y;
lr=Math.abs(2.*fi);
lf=fi;
if(hi<10)lh=10; // minimum height of lens
else if(hi>lr) lh=(int)lr-10;
else lh=hi;
// if(!is_lens && lf<0)type.setLabel("-");
// else type.setLabel("+");
}
boolean moving=false;
boolean sizing=false;
boolean lmouseDown(int x,int y){
if(Math.abs(x-lxc+ww)
if(Math.abs(y-lyc)
if((Math.abs(y-lyc-lh)
sizing=true; // change lens size/shape
else sizing=false;
return true;
}else if(!is_lens && x>lxc && (x-lxc)
return moving=true;
}
return false;
}
boolean lmouseUp(int x,int y){
sizing=false;// back to normal
moving=false;
return true;
}
boolean lmouseDrag(int x,int y){
boolean done = true;
if(sizing){ // change lens size/shape
double dx,dy;
double sign=1.;
if(is_lens){
dx=Math.abs(x-lxc);
// if(lf<0)sign=-1;
}else dx=lxc-x;
if(type.getLabel().compareTo("-")==0)sign=-1.;
dy=Math.abs(y-lyc);
linit(lxc,lyc,(int)dy,sign*Math.abs(dy*dy/dx+dx)/4.);
}else if(moving)lmove(x,lyc); // move lens
else done=false;
return done;
}
void lmove(int x, int y){
if(!is_lens && x
lxc=x;
lyc=y;
show();
}
int X[],Y[],cnt=0;
int x0,y0,ww,hh;
void lshow(){
if(!sizing &&( is_lens II thinMirror) ) lr=(3.+lh*lh/3.)/4;
//else if (!sizing && thinMirror)lr=(3.+lh*lh/3.)/4;
else lr=Math.abs(2.*lf);
// 3. is the half width of lens
if(lr
double angle=Math.asin((double)lh/lr);
lwidth=(int)(lr*(1.-Math.cos(angle)));
g.setColor(Color.red);
if(is_lens && lf>0)if(sizing)g.drawOval(lxc-lwidth,lyc-lh,2*lwidth,2*lh);
else g.fillOval(lxc-lwidth,lyc-lh,2*lwidth,2*lh);
else{
double x0,y0;
double c=Math.PI-angle,dc;
int ncnt=100;//(int)(lr*c/15.)+1;
int ncnt2=2*ncnt;
x0=lxc+lwidth/2+lr;
y0=lyc;
if(ncnt>cnt){
X=new int[ncnt2];
Y=new int[ncnt2];
cnt=ncnt;
}
//g.drawString(String.valueOf(ncnt),100,100);
ncnt2-=1;
dc=2.*angle/(ncnt-1);
if(is_lens){
for(int i=0;i
X[i]=(int)(x0+lr*Math.cos(c));
Y[ncnt2-i]=Y[i]=(int)(y0+lr*Math.sin(c));
X[ncnt2-i]=(int)(2*lxc)-X[i];
c+=dc;
}
}else{// mirror
if(lf>0){// concave mirror
ww=lwidth;
x0=lxc-lr+1;
for(int i=0;i
X[i]=(int)(x0-lr*Math.cos(c));
Y[ncnt2-i]=Y[i]=(int)(y0+lr*Math.sin(c));
X[ncnt2-i]=X[i]+lwidth;
c+=dc;
}
}else{ //convex mirror
ww=-lwidth;
x0=lxc+lr;
for(int i=0;i
X[i]=(int)(x0+lr*Math.cos(c));
Y[ncnt2-i]=Y[i]=(int)(y0+lr*Math.sin(c));
X[ncnt2-i]=X[i]+lwidth;
c+=dc;
}
}
}
X[ncnt2]=X[0];
ncnt2++;
if(!is_lens){
g.setColor(Color.black);
if(thinMirror){if(sizing)g.drawPolygon(X,Y,ncnt2);
else g.fillPolygon(X,Y,ncnt2);
}else g.drawPolygon(X,Y,ncnt2);
}else if(sizing)g.drawPolygon(X,Y,ncnt2);
else g.fillPolygon(X,Y,ncnt2);
}
g.setColor(Color.red);
g.drawLine(lxc,lyc-5,lxc,lyc+5);
// draw at +/- f, +/- 2f,
int delta=(int)lf,xa,ya=lyc-5,yb=lyc+5;
g.drawLine(xa=lxc-delta,ya,xa,yb);
delta=(int)(2.*lf);
g.drawLine(xa=lxc-delta,ya,xa,yb);
if(is_lens){
g.drawLine(xa=lxc+delta,ya,xa,yb);
delta=(int)(lf);
g.drawLine(xa=lxc+delta,ya,xa,yb);
}
if(is_lens){
if(!sizing&&inrange;){
g.setColor(Color.black);
//if(side>0.)ww=lwidth;// draw ray path in lens approximately
//else ww=-lwidth;
ww=lwidth;
g.drawLine(lxc-side*ww*3/4,lyc-oy,lxc+side*ww,lyc+(int)(oy*(ww-lf)/lf));
g.drawLine(lxc-side*ww,lyc-(int)(iy*(-ww+lf)/lf),lxc+side*ww*3/4,lyc-(int)(iy));
}
ww=0;// for lens
}
}
}