Yes, there is a meaningful distinction between the terms "thermal radiation" and "infrared radiation". With that said, there can be significant overlap between these two terms, which is probably why many people use these terms interchangeably in everyday life. "Thermal radiation" is electromagnetic radiation with any frequency that is created by the thermal emission process (not just infrared frequencies), while "infrared radiation" is electromagnetic radiation with a frequency in the specific range of 0.3 THz to 400 THz that is created by any process (not just the thermal radiation process). Infrared radiation can also be called infrared light, infrared rays, or infrared waves. There are many ways to make infrared radiation besides thermal radiation. Also, there are many other types of radiation that the thermal radiation process can create besides infrared radiation. This is summarized in the Venn diagram below. Note that this Venn diagram is in no way complete or comprehensive.

By: Christopher S. Baird, author of The Top 50 Science Questions with Surprising Answers and Associate Professor of Physics at West Texas A&M University

"The pins were held firmly by pushing them into holes made by tapping in an appropriate panel pin or similar into a piece of scrap wood which is long enough for both hands to rest on to keep firm OR of course held in a vice:-

Diaphragmof camera in eyes

Thermal radiation includes all forms of electromagnetic radiation that are emitted by an object through the thermal emission process. This is the process in which the atoms and molecules that make up an object bump around randomly, according to the object's temperature, and emit electromagnetic radiation as a result. Thermal radiation can also be called radiant heat.

All objects that are at a temperature between 1000 K and 100,000 K continuously emit thermal radiation that consists almost entirely of infrared thermal radiation, visible light thermal radiation, and ultraviolet thermal radiation. This includes objects such as candle flames, campfires, incandescent light bulbs turned on, hot electric cooktop elements, hot toaster elements, hot coals, and hot lava. The visible light that you see coming from an object that is so hot that it glows is literally visible light thermal radiation. Such objects are called incandescent.

If by chance you find that a single leaf is damaged beyond repair, the ID can often still function producing a reasonably circular aperture...........but much depends on the total number of leaves, which can vary from as little as 3 in the very cheap forms to 15 or more as shown in the first image above. 12 leaves is commonly used for the average substage or field condenser.........more leaves produce more geometrically perfect circles.

Once an ID's mechanism is over strained its future is very likely to be very short or non-existent. Repairing an iris diaphragm from a long owned and intrinsically valuable instrument depends very much on the specific problem of course, but it can be a very tedious, as well as a difficult and time consuming process. I suspect a few damaged diaphragms are consigned to the scrap heap, which then invites the problem arising from the process of replacement.

Diaphragmmicroscope function

There are other meaningful ways to plot a spectrum. We can replot the four situations shown above, but now plotting as a function of frequency. The results are shown in the four plots below. The curves look a little different when plotted as a function of frequency, because frequency means something different from wavelength, but the overall concepts that I have been explaining are still the same. Room temperature objects and normal human-temperature objects are still found to emit thermal radiation that consists of 100% infrared radiation. Incandescent light bulbs are still found to emit thermal radiation that consists mostly of infrared radiation but also contains a significant amount of visible light. Objects at the temperature of the sun's surface are still found to emit thermal radiation that consists of huge amounts of infrared radiation, visible light, and ultraviolet radiation.

The plot below shows the thermal radiation spectrum emitted by an object that is at the temperature of the sun's surface (5778 K), again assuming that the object is an ideal blackbody emitter. As you can see, the thermal radiation now consists of huge amounts of infrared radiation, visible light, and ultraviolet radiation. This is why sunlight does a great job of warming us up, illuminating the world around us, and giving us sunburns.

What is the iris diaphragmin microscope

Some people show the plot below and claim that because the curve peaks in the visible-light range, that means that the sun emits mostly visible light and that's why human vision evolved to be tuned to these frequencies. This is incorrect. The same data in the plot below plotted as a function of frequency does not peak in the visible-light range, as you will see later. This is because the peak of a broad spectral distribution does not have much meaning. Also, to be clear, the plot below does not exactly show the spectrum of the light emitted by the sun, although it is very close. The plot below shows what the spectrum of the light emitted by the sun's surface would look like if the sun was a perfect blackbody emitter.

2 leaves are shown below resting more or less in their working position on top of the driver plate whose slots allow the constant radial change of position of their respective leaf pins when it is rotated during operation. The upper pins are housed in the holes of the ID body shown above.

Diaphragmcamera function

The success of a repair depends not just on the sensitive skills of the hands BUT as much on the accuracy of the notes and sketches you make before disassembly. Hopefully your particular repair will be easier than those I have described as most substage iris assembles seem to be fairly accessible. Good luck!

The plot below shows the thermal radiation spectrum emitted by an object that is at the temperature of a living human (310 K), again assuming that the object is an ideal blackbody emitter, which is usually close to the truth. As you can see, the thermal radiation still consists of 100% infrared radiation. An object at this temperature is nowhere near to emitting visible light or higher frequencies. This is why humans at normal temperatures do not visibly glow, i.e. they are only glowing at non-visible infrared frequencies. (A human at abnormal temperatures can certainly visibly glow, such as when on fire.) Click image to enlarge. Public Domain Image, source: Christopher S. Baird. All objects that are at a temperature between 1000 K and 100,000 K continuously emit thermal radiation that consists almost entirely of infrared thermal radiation, visible light thermal radiation, and ultraviolet thermal radiation. This includes objects such as candle flames, campfires, incandescent light bulbs turned on, hot electric cooktop elements, hot toaster elements, hot coals, and hot lava. The visible light that you see coming from an object that is so hot that it glows is literally visible light thermal radiation. Such objects are called incandescent. The plot below shows the thermal radiation spectrum emitted by an object that is at the temperature of an incandescent light bulb filament (2820 K) when the light bulb is turned on (assuming an ideal blackbody emitter). As you can see, the thermal radiation still consists mostly of infrared radiation. However, it also consists of a significant amount of visible light and a small amount of ultraviolet radiation. In other words, an incandescent light bulb that is turned on emits far more non-visible infrared radiation than it does visible light. This is why incandescent light bulbs are so inefficient. Click image to enlarge. Public Domain Image, source: Christopher S. Baird. The plot below shows the thermal radiation spectrum emitted by an object that is at the temperature of the sun's surface (5778 K), again assuming that the object is an ideal blackbody emitter. As you can see, the thermal radiation now consists of huge amounts of infrared radiation, visible light, and ultraviolet radiation. This is why sunlight does a great job of warming us up, illuminating the world around us, and giving us sunburns. Some people show the plot below and claim that because the curve peaks in the visible-light range, that means that the sun emits mostly visible light and that's why human vision evolved to be tuned to these frequencies. This is incorrect. The same data in the plot below plotted as a function of frequency does not peak in the visible-light range, as you will see later. This is because the peak of a broad spectral distribution does not have much meaning. Also, to be clear, the plot below does not exactly show the spectrum of the light emitted by the sun, although it is very close. The plot below shows what the spectrum of the light emitted by the sun's surface would look like if the sun was a perfect blackbody emitter. Click image to enlarge. Public Domain Image, source: Christopher S. Baird. Note that most of the plots above have different vertical scales. The vertical scales were adjusted in each case to make the plotted curve fill the graph. All of the plots above show the thermal radiation spectrum as a function of the wavelength. There are other meaningful ways to plot a spectrum. We can replot the four situations shown above, but now plotting as a function of frequency. The results are shown in the four plots below. The curves look a little different when plotted as a function of frequency, because frequency means something different from wavelength, but the overall concepts that I have been explaining are still the same. Room temperature objects and normal human-temperature objects are still found to emit thermal radiation that consists of 100% infrared radiation. Incandescent light bulbs are still found to emit thermal radiation that consists mostly of infrared radiation but also contains a significant amount of visible light. Objects at the temperature of the sun's surface are still found to emit thermal radiation that consists of huge amounts of infrared radiation, visible light, and ultraviolet radiation. Click image to enlarge. Public Domain Image, source: Christopher S. Baird. Click image to enlarge. Public Domain Image, source: Christopher S. Baird. Click image to enlarge. Public Domain Image, source: Christopher S. Baird. Click image to enlarge. Public Domain Image, source: Christopher S. Baird. All objects that are at a temperature above 100,000 K continuously emit thermal radiation that consists of infrared thermal radiation, visible light thermal radiation, ultraviolet thermal radiation, and x-ray thermal radiation. This includes objects such as hot stars and supernovas. Note that the sun's surface is not hot enough to thermally emit much x-ray radiation, but the sun's corona is. Interestingly, objects in the universe that are hot enough to thermally emit significant amounts of gamma-ray radiation are exceedingly rare. Processes that can create temperatures this high are so powerful that they generate far more gamma rays through other mechanisms than through thermal radiation. The plot below shows the percent of the emitted thermal radiation that is infrared radiation at each object temperature (assuming an ideal blackbody emitter). More specifically, it shows the percent of the thermally radiated energy that is in the range of 0.3 THz to 400 THz, as a function of the radiating object's temperature. This plot summarizes much of the information that I have presented above. Note that the complications that arise at cryogenic temperatures (less than 120 K) are not visible in this plot because the plot's temperature scale is so large. Click image to enlarge. Public Domain Image, source: Christopher S. Baird. As you can see from this plot, the emitted thermal radiation consists of 100% infrared radiation for (non-cryogenic) temperature less than 1000 K, which includes cold winter outdoor temperatures, hot summer outdoor temperatures, room temperature, the temperature of a living human, and every temperature at which a human can touch an object and not get burned. Furthermore, most of the ambient infrared radiation in everyday life is created by the thermal radiation process. This is why the terms "thermal radiation" and "infrared radiation" are often used interchangeably in everyday life, even though they mean different things. This means that in everyday life (ignoring objects that are so hot that they glow), if you use the terms "thermal radiation" and "infrared radiation" interchangeably to describe objects in the room, then you won't be very wrong. In contrast, if you use these terms interchangeably to describe hot stars, then you will be very wrong. For instance, less than half of the sun's thermally radiated energy is infrared radiation. Only 2% of the thermally radiated energy emitted by the star Sirius B is infrared radiation. The table below presents the values of some of the data points in the plot above, where the percents are in terms of radiated energy. TemperaturePercent of the thermalradiation that is infrared Room temperature (294 K)100% Human body temperature (310 K)100% Temperature at which water boils (373 K)100% Hottest household oven temperature (533 K)100% Temperature at which aluminum melts (933 K)100% Temperature of incandescent light bulb (2820 K)91% Temperature of the sun's surface (5778 K)46% Temperature of the surface of Sirius A (9940 K)17% Temperature of the surface of Sirius B (25,200 K)2% Infrared radiation includes all electromagnetic waves that are between radio waves and visible light on the electromagnetic spectrum, regardless of what created them. More specifically, infrared radiation includes all electromagnetic radiation with a wavelength between 1 millimeter and 650 nanometers, which corresponds to a frequency in the range of 0.3 THz to 400 THz. Infrared radiation is most commonly generated by the thermal radiation process, but it can also be produced by lasers, LEDs, spectral line emitters, cyclotron emitters, and so forth. In summary, the term "infrared radiation" refers to electromagnetic radiation of particular wavelengths regardless of the source, while the term "thermal radiation" refers to electromagnetic radiation created by the thermal emission process regardless of the wavelengths. Therefore, the term "infrared thermal radiation" is not redundant, but literally means "infrared-wavelength radiation created by the thermal emission process". The visible glow that you see from a campfire is not infrared thermal radiation. It is visible light thermal radiation. The infrared signal from a remote control is infrared radiation but is not thermal radiation. The visible light from your LED flashlight is neither infrared radiation nor thermal radiation, but is visible LED light. In contrast, the radiant heat from a hot rock near the campfire that warms you after the campfire has been put out is 100% infrared thermal radiation. These concepts are summarized below. Example of radiationInfrared radiation?Thermal radiation? Visible glow of a campfireNoYes Visible sunlightNoYes Signals from a remote controlYesNo Signals in fiber optic cablesYesNo Visible illumination from an LED flashlightNoNo Ultraviolet radiation from a tanning bedNoNo Radiant heat from a dark hot rockYesYes Radiant heat from any object that is not visibly glowing (and not cryogenic)YesYes Topics: incandescence, infrared, light, temperature, thermal radiation

Note that most of the plots above have different vertical scales. The vertical scales were adjusted in each case to make the plotted curve fill the graph. All of the plots above show the thermal radiation spectrum as a function of the wavelength.

Throughout its potentially long life the Iris Diaphragm is called upon to play its role, then at some time its delicate mechanism fails. Chances are that the onset of failure is noticed as the resistance of the lever suddenly increases denoting some form of seizure, or by the sound of the 'leaves' complaining of strain. Pear drop shape apertures are common too when the diaphragm fails as one or two of its leaves become unresponsive. A well made example will last a couple of lifetimes or more in sensitive hands, and there are examples of diaphragms still winking from as far back as the 1800's! Though in essence the diaphragm is a simple device its manufacture is not so straightforward, as even its reassembly can test the skills and patience of anyone who has tried. Examples of the best diaphragms manufactured show clearly that there is a great deal of quality engineering and design invested in them, and so their usage should be well regarded, particularly by fingers sensitive enough to pause the moment the slightest change in lever resistance is felt.

All objects made of atoms are always emitting thermal radiation. In order to emit zero thermal radiation, an object would have to be at exactly zero absolute temperature. However, exactly zero absolute temperature is impossible because quantum uncertainty does not allow it. The hotter that an object gets, the more thermal radiation it emits. Also, the hotter that an object gets, the more that the spectrum of the thermal radiation that it emits expands to include higher frequencies. Depending on the temperature of the object, it can emit various combinations of radio wave thermal radiation, infrared thermal radiation, visible light thermal radiation, ultraviolet thermal radiation, x-ray thermal radiation, and gamma ray thermal radiation. (Note that microwave radiation is a type of radio wave radiation and therefore does not need to be mentioned separately.)

If you are tempted to try repairing an ID for the first time, remember to take notes of the physical disposition of all the parts and mark the internal bores if necessary to record positions etc. Best open the iris fully and make marks wherever suitable to make sure when reassembling the driver plate that it goes back precisely in original position relating to the lever and its body stop. Even a few digicam snaps will help.

The plot below shows the thermal radiation spectrum emitted by an object at room temperature (294 K) such as a chair or a table (assuming that the object is an ideal blackbody emitter, which is usually close to the truth). Do not be confused by the word "blackbody" as it is just the name for the idealized explanation and does not refer to colors in the spectrum. As you can see in the plot below, 100% of the thermal radiation emitted by an object at room temperature is infrared radiation. In fact, an object at room temperature is nowhere near to thermally emitting visible light or higher frequencies. This is why objects at room temperature do not visibly glow through thermal effects. In the two plots below, the entire curve is not shown because I wanted all wavelength plots in this article to be on the same horizontal scale so that you can visually compare them.

All objects that are at a temperature below about 1000 K (but above cryogenic temperatures) continuously emit thermal radiation that is 100% infrared radiation. This includes objects at room temperature, such as chairs and tables; objects at cold winter temperatures, such as snow and ice; objects at normal biological temperatures, such as birds and humans; and objects cooked in household ovens, such as pizzas and cookies right out of the oven. That is why none of these objects visibly glow.

As you can see from this plot, the emitted thermal radiation consists of 100% infrared radiation for (non-cryogenic) temperature less than 1000 K, which includes cold winter outdoor temperatures, hot summer outdoor temperatures, room temperature, the temperature of a living human, and every temperature at which a human can touch an object and not get burned. Furthermore, most of the ambient infrared radiation in everyday life is created by the thermal radiation process. This is why the terms "thermal radiation" and "infrared radiation" are often used interchangeably in everyday life, even though they mean different things. This means that in everyday life (ignoring objects that are so hot that they glow), if you use the terms "thermal radiation" and "infrared radiation" interchangeably to describe objects in the room, then you won't be very wrong. In contrast, if you use these terms interchangeably to describe hot stars, then you will be very wrong. For instance, less than half of the sun's thermally radiated energy is infrared radiation. Only 2% of the thermally radiated energy emitted by the star Sirius B is infrared radiation. The table below presents the values of some of the data points in the plot above, where the percents are in terms of radiated energy.

The plot below shows the percent of the emitted thermal radiation that is infrared radiation at each object temperature (assuming an ideal blackbody emitter). More specifically, it shows the percent of the thermally radiated energy that is in the range of 0.3 THz to 400 THz, as a function of the radiating object's temperature. This plot summarizes much of the information that I have presented above. Note that the complications that arise at cryogenic temperatures (less than 120 K) are not visible in this plot because the plot's temperature scale is so large.

Iris diaphragmlever

Depending entirely on the physical aspects of the ID makes for either difficult or relatively easier implementation of the repair. Of course if you find yourself having to re assemble it all then each leaf must be orientated so the pins are housed in their appropriate hole in the body of the ID. The leaves are layered one at a time around the inside of the body each overlapping the previously laid leaf. The great difficulty occurs when the last few are placed in situ simply because some of the those already in place need to be raised slightly for the final fitment of the remainder.......as you will experience. THIS can be very problematic with small deeply housed iris diaphragms as the process tends to loosen the rest of the leaves. I have 2 solutions which work 1) If you have steel leaves then use a magnet beneath the ID to retain the leaves securely as you go along OR 2) If your leaves are bronze/brass then coat every leaf including the platform with the holes with something sticky such as 'Vaseline which will prevent the leaves from springing about whilst laying them into place. Once the whole job is completed, the sticking agent can be dissolved away with appropriate solvent.

Lens-irisdiaphragmretropulsion syndrome

Pushing home the driver plate is relatively straightforward and just requires sensitive observation so that all the pins ready to receive the slots are equally spaced from each other. Always push the leaves out to maximum opening so their upper pins are all evenly spaced to receive the driver plate. When the plate is eased over the pins, its retaining ring should be gently screwed down on the driver plate which should be slowly oscillated whilst the retaining ring is finally brought to its working position. A registration mark denoting the in-place position of both the ID barrel and this retaining ring gives reassurance that everything is back to original position.............a very important point.

I think those ID's employing steel leaves give most of the trouble as oxidation causes dust which exacerbates friction which in turn tempts the user to oil them. Then the problem compounds because oil attracts dust which in turn helps to make the oil drier and so ad infinitum! All this just increases the forces necessary to adjust the iris, and of course something fails eventually..............usually the pins or the leaves crumple.

All objects that are at a temperature above 100,000 K continuously emit thermal radiation that consists of infrared thermal radiation, visible light thermal radiation, ultraviolet thermal radiation, and x-ray thermal radiation. This includes objects such as hot stars and supernovas. Note that the sun's surface is not hot enough to thermally emit much x-ray radiation, but the sun's corona is. Interestingly, objects in the universe that are hot enough to thermally emit significant amounts of gamma-ray radiation are exceedingly rare. Processes that can create temperatures this high are so powerful that they generate far more gamma rays through other mechanisms than through thermal radiation.

Other problems besetting the ID are crumpled or distorted leaves which have got that way because of inherent friction from dried up lubricant or insensitive use after a pin or two loosened. Sadly once a leaf has been crinkled its life is essentially over and that of the ID as a whole unless you can flatten it very carefully and also replace the pin...........a task only the really dedicated embrace! Slide mounters and clock makers have a decided advantage!!

In summary, the term "infrared radiation" refers to electromagnetic radiation of particular wavelengths regardless of the source, while the term "thermal radiation" refers to electromagnetic radiation created by the thermal emission process regardless of the wavelengths. Therefore, the term "infrared thermal radiation" is not redundant, but literally means "infrared-wavelength radiation created by the thermal emission process". The visible glow that you see from a campfire is not infrared thermal radiation. It is visible light thermal radiation. The infrared signal from a remote control is infrared radiation but is not thermal radiation. The visible light from your LED flashlight is neither infrared radiation nor thermal radiation, but is visible LED light. In contrast, the radiant heat from a hot rock near the campfire that warms you after the campfire has been put out is 100% infrared thermal radiation. These concepts are summarized below.

What is the iris diaphragmused for

Once the pin was in a fixed position with the rebate uppermost the leaf could be positioned back over it to allow the spigot through the hole of the leaf. Careful peaning over the soft bronze with a sharp instrument reattached the pin once more, and the repair was made as smooth as possible to prevent seizure. The finished job was not tidy under the eyeglass but that didn't matter as it worked well and still does."

Iris diaphragmvs condenser

However, I have effected some repairs and adjustments to some diaphragm assembles and in particular I had to repair a very good CTS ID with steel leaves which had been neglected, as I'd found a couple of its leaf pins had loosened. Using the low power stereo 'scope was necessary to re-rivet these back onto the leaves which was very fiddly indeed. Unfortunately as I did this a long time ago I have no photographic record of the way I repaired them......but from memory:-

The plot below shows the thermal radiation spectrum emitted by an object that is at the temperature of an incandescent light bulb filament (2820 K) when the light bulb is turned on (assuming an ideal blackbody emitter). As you can see, the thermal radiation still consists mostly of infrared radiation. However, it also consists of a significant amount of visible light and a small amount of ultraviolet radiation. In other words, an incandescent light bulb that is turned on emits far more non-visible infrared radiation than it does visible light. This is why incandescent light bulbs are so inefficient.

Infrared radiation includes all electromagnetic waves that are between radio waves and visible light on the electromagnetic spectrum, regardless of what created them. More specifically, infrared radiation includes all electromagnetic radiation with a wavelength between 1 millimeter and 650 nanometers, which corresponds to a frequency in the range of 0.3 THz to 400 THz. Infrared radiation is most commonly generated by the thermal radiation process, but it can also be produced by lasers, LEDs, spectral line emitters, cyclotron emitters, and so forth.

There is always a minute amount of radio wave radiation emitted as part of the thermal radiation. However, for all temperatures except cryogenic temperatures, the part of the thermal radiation that is radio waves is miniscule, so that we can ignore it and still get the same answers to four significant figures. More specifically, for all temperatures except cryogenic temperatures, radio waves make up less than a ten-thousandth of the total thermally radiated energy.

If you used Vaseline or similar to aid the reassembly of the leaves this needs removing using petroleum based solvents, though iso-butyl alcohol will shift the bulk of it.

Steel leaves are used particularly in camera lenses where they are relatively free of moisture and abundant oxygen. Many are coated with various substances to suppress oxidation and perhaps aid slippage, but this process can produce plenty of unwanted fine particles dancing around inside promising future trouble.

Though an oiled ID might feel smooth in operation to the touch, the chances are that the pins are straining with forces they were not designed to take, as the leaves are not sliding over each other in their oil free original state, but are wrestling with relatively high oily contact forces.

Iris Diaphragms ( ID for brevity's sake) come in various forms, differing in materials, design and size. Essentially most employ a number of semi-circular 'leaves' each sporting 2 pins riveted one at either end on opposing sides. Half of these pins engage in holes around the periphery of the body of the ID whilst their opposite numbers are located in short slots milled around the periphery of the 'driver' plate which is under the control of the finger lever. The slots allow for the change in the radial variations the leaf experiences as the ID is closed and opened. It is an ingenious device which has been manufactured by optical/engineering companies in varying guises, but they are all essentially of similar spiral format where rotation of the outer leaves closes the aperture in a smoothly controlled manner.

One particular feature of substage IDs is their ability to close down almost completely: a facility rarely required in ordinary camera lenses. This needs carefully designing and manufacture because the lever stop needs to coincide precisely with the pinhole setting of the iris, otherwise damage might ensue from the crumpling of the leaves. The image below is of a typical ID where the lever stops positively just before iris closure. Of course an iris in the substage condenser in this state is of little use for brightfield observation, but is provided so that we can align the optical train more easily knowing where the substage central axis is. This expectant feature places some responsibility on microscope manufacturers to produce IDs of high geometric accuracy as well as sound mechanical integrity.

Below, the body of the condenser or lens barrel has a number of static holes into which one pin from each leaf registers can be seen.

Diaphragms in microscopy are usually more accessible to the atmosphere, insects, mould and probing fingers etc., so are more vulnerable to long term chronic damage.