Understanding lensometria

Understanding lensometria

Article written by Paulus Maciel. Rights Reserved. This area aims to help eliminate the difficulty in using optical professional focimeter to read the diopter lens glasses. based on a presentation I'm going to put together the right time, called "Testing Lensometria." The language to be used in this regard will be as objective as possible. A language will be objective, but the understanding should be done calmly and lots of practice. I suggest that you read and practice this matter with a reserved time. To facilitate the visualization of all the information, I'll post pictures of large size. Firstly we need to know the parts that make up a focimeter:

• Ocular. Where do we put our eye to see the display's internal focimeter.
• Display drum axis. Thumbwheel that makes the image sharper display internal focimeter. This internal image is a grid that shows the positions of the axis to be read.
• Drum diopters. Thumbwheel to be handled while reading diopters spherical and cylindrical.
• Drum axis. Rotary knob to be handled during reading the axis of cylindrical diopter.

Watch an aerial image of the drums and the axis of diopters.

Now I will describe the other components of lensometros, especially those near the lenses to be measured:

• Fork lift. Support that holds the lens so that it is in the right position reading.
• Adjust the fork. Lever that allows up and down the fork lift.
• Support sighting. This bracket has an opening that will be the target of focimeter. Normally lensometros comes with at least two holders with sights of different apertures choosing the optical. I prefer to aim with the smallest aperture.
• Mira. Opening which will allow the reading of the display diopters in required location. The aim should be positioned in the region of the lens where the optical need to read the diopter. I'll separate a topic to talk about the party position crosshairs.
• Center marker. With three support tips which can be soaked with ink for marking the optical center of the lens.
• Table support. Support that keeps the glasses straight to the fork lift can hold the lens, so the sight of focimeter position yourself correctly for reading.
• Adjust table. Lever up or down which allows the table to support the glasses stay at the correct height measurement.

The sight of focimeter need to be very well positioned for the proper reading of diopters.In single vision lenses, optical center after being found, it is just that the diopter will be read.

In progressive multifocal lenses, the sight of focimeter must have the following positions:

• Diopter far. The opening of the entire target must be positioned above the height marking pupil, also known as cross assembly.
• Prism balance. The point prism for reading the multifocal lens varies with lens design. Essilor lenses in the prism is 4mm below the cross assembly in the prism Zeiss lens is 6mm cross, except the lens compact Sola. In the Hoya lens prism is 4mm below the cross.
• Diopter closely. The reading point is at the bottom of the lens to the marking decentered to the nasal between 2.5 and 5.0 mm depending on the design of the lens.
• To redial the multifocal lens, ask the manufacturer to your feedback and access a matter I wrote about rebooking progressive lenses.

Before you start reading the diopter, it is necessary to adjust the display's viewing focimeter according to our eyesight, so we can see exactly how much the display will show the reticles that reading the diopters:

• Keep focimeter off
• In place of the lens, place a white sheet of paper in front of the crosshairs focimeter
• Rotate the eyepiece to leave the dial shaft very clear (target format picture)
• Do not forget to rotate the drum axis of the display to make it in the correct position (target at the upper right of the image below)

Now we know the internal display focimeter still off. 

When we turn on the focimeter, we find superimposed on an image display bright green, which can be shaped cross or circle. These images are called "reticules". The format of the reticle varies by brand and model focimeter. In this matter I will show you how to read in both formats reticle.

Come to the reading with cross reticle. This cross is formed by two meridians, the first one is what we call a "spherical". Note that all traces of spherical lattice have the same length.

The other meridian is cylindrical. Note that the features of reticle means are longer precisely to serve as a pointer to indicate the axis.

The reading of the diopter consists in leaving the image clearer these reticles possible, even one at a time.

Step by step of reading a spherical lens diopter:

• Place the glasses in the table focimeter in order to position the crosshairs of the field lens being measured diopter. 
• Drop the fork to hold the glasses.
• Turn the diopter drum and try to leave the crosshairs very clear.
• If both reticle spherical cylindrical were as sharp at the same time, this means that the lens has only spherical diopter.
• After leaving the two reticules very clear, note that the diopter dial of the focimeter indicates as being spherical.

When a lens is combined, the reticles are sharp only separately. The combined reading of a lens is to read the diopter of each separate reticles and calculates the difference in diopter with one another, thereby causing the diopter spherical and cylindrical.

Step by step of reading a sphero cylindrical diopter lens:

• Place the glasses in the table focimeter in order to position the crosshairs of the field lens being measured diopter. 
• Drop the fork to hold the glasses.
• By default, we start reading the spherical diopter
• Turn the diopter drum and axle while to let the ball well clear reticle.
• When turning the drum shaft to the right, you will notice that the ball will stay sharp reticle. Write down the value of a draft diopter found.

• Now rotate the drum axis and diopter clockwise. Note that the spherical lattice will also be clear, but with a different value diopter. Note the diopter value in this draft.

Read your draft and compare the diopter noted. The diopter MORE positive will be considered spherical. In the example below were found to +0.50 diopters and +3.00. The more positive diopter them is +3.00, +3.00 is therefore the diopter spherical lens. Now we can find the following diopter cylindrical.

• Turn the diopter drum and axle while leaving until the reticle clear cylindrical well.
• When turning the drum shaft to the right, you will notice that the reticle is clear cylindrical vai. Write down the value of a draft diopter found. In the example below +1.00

• Now rotate the drum axis and diopter clockwise. Note that the cylindrical lattice will also be clear, but with a different value diopter. Note the diopter value in this draft. In the example below +2.50.

Read your draft and compare the diopter noted. The difference between the diopter LESS MORE positive and positive will be considered cylindrical. In the example below were found to +1.00 diopters and +2.50. The numerical difference between the diopter is 1.50 (this account does not take into account the sign, only the numerical differences). The numerical difference found is the diopter negative cylindrical lens, so time -1.50 cyl.

  

• Turn the diopter drum in the opposite direction that you think the diopter less positive in the case +1.00. Let the reticle clear cylindrical and observe the display of focimeter which is the axis of the cylindrical diopter. In example 45 °.

The final reading is: +2.50 - 1.50 at 45 °

Now I'll show you how to read in a circle with crosshairs.

When the drum is rotated and diopters of any circle is marked, means reading a spherical diopter. To read a spherical lens, simply rotate the drum Dioptre leave the circle until completely crisp. See the display which is the spherical diopter.

We know when the lens is combined only when the reticle is clear when its shape is like a cone. See the format in the example below.

Step by step of reading a sphero cylindrical diopter lens:

• Place the glasses in the table focimeter in order to position the crosshairs of the field lens being measured diopter. 
• Drop the fork to hold the glasses.
• By default, we start reading the spherical diopter
• Rotate the drum until Dioptre leave cone-shaped reticle very clear.
• Note the diopter found a stub. In the example below +2.50

• Simply turn the diopter drum counterclockwise until the cone-shaped reticle is sharp again, now with a different result diopter. Note the diopter found a stub.In the example below +1.00

The spherical diopter will always be more positive among them. In the example below the more positive is +2.50, then the ball is +2.50 diopter.

The numerical difference between the diopter more positive and less positive is a negative diopter cylindrical lens. In the example below, the numerical difference between 2.50 and 1.00 is 1.50, so the diopter negative cylindrical lens is -1.50.

To find the axis of the cylindrical diopter:

• Turn the diopter drum in the opposite direction that you found the strength less positive in the case +1.00. 
• Rotate the drum axis and allow display of the meridian line of the display parallel to the direction of sharpness of the reticle cone-shaped. The display itself will indicate the axis in the case below 165 °.

The final reading is: +2.50 -1.50 to 165 °

For that you get maximum result of learning with information that matter, I recommend that you practice enough to lensometria with the widest possible lens. Only constant practice in the skills necessary for reading will be obtained in focimeter. Want to download a free book to study lensometria? Go to the download area Paulus Blog, click HERE and you will be directed there. the letter "A" search for "Handout Lensometria"