Thanks Guy. Yeah It has a mirror on the outer diameter but I don't know what's
the purpose of that. I have another question, I'm using this formula
Proj. Diag Size = (Distance2Screen-FLofProj)*(LCD Size)
_____________________________________
FL
Objective Focal is 8.66 inches
I use excel and I came up with these values:
LCD Sz(in) -- dist to screen(in)--FL of Proj(in)-- Proj. Diagonal-- lcd 2 LENS
8 117 8.66 100.0831409 9.352224478
8 116 8.66 99.15935335 9.358673374
8 115 8.66 98.23556582 9.365243558
8 114 8.66 97.31177829 9.371938485
8 113 8.66 96.38799076 9.37876174
8 112 8.66 95.46420323 9.385717051
8 111 8.66 94.5404157 9.392808286
8 110 8.66 93.61662818 9.400039471
8 109 8.66 92.69284065 9.40741479
8 108 8.66 91.76905312 9.414938595
8 107 8.66 90.84526559 9.422615416
8 106 8.66 89.92147806 9.430449969
8 105 8.66 88.99769053 9.438447166
8 104 8.66 88.073903 9.446612125
8 103 8.66 87.15011547 9.45495018
8 102 8.66 86.22632794 9.463466895
8 101 8.66 85.30254042 9.472168075
Do you know any site that sells small motor like stepper that has accurate
rotational to translational displacement?
I noticed that Changing the distance to screen while others are constant change the
lcd to Objective in a small increments. I'm thinking about using a PVC then attach
the motor so I can control the displacement accurately.
I also remember when I was a little boy, I had this top that has a threaded string.
You use the string to rotate the top. I guess we could also use that but it wont be exact.
Is this possible? What do you think?
Many Thanks Guy!
the purpose of that. I have another question, I'm using this formula
Proj. Diag Size = (Distance2Screen-FLofProj)*(LCD Size)
_____________________________________
FL
Objective Focal is 8.66 inches
I use excel and I came up with these values:
LCD Sz(in) -- dist to screen(in)--FL of Proj(in)-- Proj. Diagonal-- lcd 2 LENS
8 117 8.66 100.0831409 9.352224478
8 116 8.66 99.15935335 9.358673374
8 115 8.66 98.23556582 9.365243558
8 114 8.66 97.31177829 9.371938485
8 113 8.66 96.38799076 9.37876174
8 112 8.66 95.46420323 9.385717051
8 111 8.66 94.5404157 9.392808286
8 110 8.66 93.61662818 9.400039471
8 109 8.66 92.69284065 9.40741479
8 108 8.66 91.76905312 9.414938595
8 107 8.66 90.84526559 9.422615416
8 106 8.66 89.92147806 9.430449969
8 105 8.66 88.99769053 9.438447166
8 104 8.66 88.073903 9.446612125
8 103 8.66 87.15011547 9.45495018
8 102 8.66 86.22632794 9.463466895
8 101 8.66 85.30254042 9.472168075
Do you know any site that sells small motor like stepper that has accurate
rotational to translational displacement?
I noticed that Changing the distance to screen while others are constant change the
lcd to Objective in a small increments. I'm thinking about using a PVC then attach
the motor so I can control the displacement accurately.
I also remember when I was a little boy, I had this top that has a threaded string.
You use the string to rotate the top. I guess we could also use that but it wont be exact.
Is this possible? What do you think?
Many Thanks Guy!
linear actuator
It is actually very easy to focus the projector lens manually after you move the projector to a new screen distance. A lot of people don't even bother to use a knob/threaded rod type mechanism, just going for a simple releasable clamp to hold the lens from sliding in a slightly larger tube. After all, you only need to do it once after you move the projector. With our giant boxes, not many people move them around!
It sounds like you want to build a motorized focus adjustment. The device you need is a "linear actuator" or "linear motor". It is pretty much just a stepper motor driving a pinion gear to move a long toothed rod. You can find them by doing a web search for either of those terms. You can also try including "robot parts" or "surplus". I think the driver interface is pretty simple: You supply pulses to one wire to move the rod one way, pulses to another wire move the rod the other way. One "step" per pulse, where the step size may be 0.1 mm or it may be 5 mm. Depends on the design. Some will have a current position output signal, if you want to automate the whole thing.
It is actually very easy to focus the projector lens manually after you move the projector to a new screen distance. A lot of people don't even bother to use a knob/threaded rod type mechanism, just going for a simple releasable clamp to hold the lens from sliding in a slightly larger tube. After all, you only need to do it once after you move the projector. With our giant boxes, not many people move them around!
It sounds like you want to build a motorized focus adjustment. The device you need is a "linear actuator" or "linear motor". It is pretty much just a stepper motor driving a pinion gear to move a long toothed rod. You can find them by doing a web search for either of those terms. You can also try including "robot parts" or "surplus". I think the driver interface is pretty simple: You supply pulses to one wire to move the rod one way, pulses to another wire move the rod the other way. One "step" per pulse, where the step size may be 0.1 mm or it may be 5 mm. Depends on the design. Some will have a current position output signal, if you want to automate the whole thing.
Thanks for the info regarding the linear actuator.
I didn't know how it's called.
Oh, I think I don't need that linear actuator if I can change
it manually without a problem.
Guy, In your opinion, what is the best design, Split Fresnel,
Sandwhiched Fresnel, Single Fresnel before the LCD?
Anyway, I'd like to do keystone correction. Can this be done
by split design only? Have no time to do experiments.
I hope I get this right, 20mm so that there is no fresnel rings:
Split design, Field Fresnel = LCD to Obj distance minus 20mm
Sandwhiched or single before LCD= LCD to Obj distance plus 20mm
Thanks!
I didn't know how it's called.
Oh, I think I don't need that linear actuator if I can change
it manually without a problem.
Guy, In your opinion, what is the best design, Split Fresnel,
Sandwhiched Fresnel, Single Fresnel before the LCD?
Anyway, I'd like to do keystone correction. Can this be done
by split design only? Have no time to do experiments.
I hope I get this right, 20mm so that there is no fresnel rings:
Split design, Field Fresnel = LCD to Obj distance minus 20mm
Sandwhiched or single before LCD= LCD to Obj distance plus 20mm
Thanks!
How does my Triplet specs has a 5.54 magnification?
Guy,
Objective FL = 285 or 11.22"
Fresnel Focal = 330mmFL
Moving the objective from focus throw distance of 140" to get
Fresnel Focus at 329.8. Now, pushing in my objective focus box
would still focus the image while changing the throw distance,
but by how much I can move the focus box to my 74mm diameter projection lens?
LCD FLofObj Throw Dist. Screen Sz(Diagonal) Lcd2Obj Fresnel+20
8 11.22 185 123.9 11.94 303.4 323.4
8 11.22 180 120.3 11.97 303.9 323.9
8 11.22 175 116.8 11.99 304.5 324.5
8 11.22 170 113.2 12.01 305.1 325.1
8 11.22 165 109.6 12.04 305.8 325.8
8 11.22 160 106.1 12.07 306.5 326.5
8 11.22 155 102.5 12.10 307.2 327.2
8 11.22 150 99.0 12.13 308.0 328.0
8 11.22 145 95.4 12.16 308.9 328.9
8 11.22 140 91.8 12.20 309.8 329.8
M = (lens-to-screen) / (LCD-to-lens)
M= 4699/303.4
M= 15.49
This is my Objective specs:
EFL: 285
Magnification: 5.54
74 diameter
I dont clearly understand the magnification specs I have here.
Guy, I tried your formula but it gives diff. values.
Do you know what it means by my magnification of 5.54?
Many Thanks!
Guy,
Objective FL = 285 or 11.22"
Fresnel Focal = 330mmFL
Moving the objective from focus throw distance of 140" to get
Fresnel Focus at 329.8. Now, pushing in my objective focus box
would still focus the image while changing the throw distance,
but by how much I can move the focus box to my 74mm diameter projection lens?
LCD FLofObj Throw Dist. Screen Sz(Diagonal) Lcd2Obj Fresnel+20
8 11.22 185 123.9 11.94 303.4 323.4
8 11.22 180 120.3 11.97 303.9 323.9
8 11.22 175 116.8 11.99 304.5 324.5
8 11.22 170 113.2 12.01 305.1 325.1
8 11.22 165 109.6 12.04 305.8 325.8
8 11.22 160 106.1 12.07 306.5 326.5
8 11.22 155 102.5 12.10 307.2 327.2
8 11.22 150 99.0 12.13 308.0 328.0
8 11.22 145 95.4 12.16 308.9 328.9
8 11.22 140 91.8 12.20 309.8 329.8
M = (lens-to-screen) / (LCD-to-lens)
M= 4699/303.4
M= 15.49
This is my Objective specs:
EFL: 285
Magnification: 5.54
74 diameter
I dont clearly understand the magnification specs I have here.
Guy, I tried your formula but it gives diff. values.
Do you know what it means by my magnification of 5.54?
Many Thanks!
magnification
>Do you know what it means by my magnification of 5.54?
No. "Magnification" is used to express all sorts of things. Maybe your lens "magnification" is relative to a particular object size and distance from the lens.
In the equations I posted above, it refers to the ratio of LCD size to screen image size, which is also the same as the ratio of (throw distance)/(LCD to lens distance).
>Do you know what it means by my magnification of 5.54?
No. "Magnification" is used to express all sorts of things. Maybe your lens "magnification" is relative to a particular object size and distance from the lens.
In the equations I posted above, it refers to the ratio of LCD size to screen image size, which is also the same as the ratio of (throw distance)/(LCD to lens distance).
- Status
- Not open for further replies.