Reports about the state of
the photographic industry all indicate that there has been a definite slow
down. Just about everybody reported
lower sales volumes. This was further underlined
by the fact that especially the market leaders Canon and Nikon had nothing
really new to show at the recent Photokina.
The notable exception is Leica.
Not only did they show a wealth of new items, both cameras and lenses, as well as accessories, but they also were able to point to a very healthy grows in sales.
Over the years Leica has been
thoroughly criticized as being out of touch with market trends, that they are
just trying to hold on to their past glory.
Leica indeed has taken a definitely different approach. They have steadfastly continued with their
production methods which are totally without mass production but offer
extremely high tolerances and general attention to detail and overall quality. That is paying off.
These production methods are
thoroughly rooted in their past, starting with the original Optical Institute
in Wetzlar out of which Leica evolved.
For that reason I decided to republish an article from 1969, when Leica
Camera AG was still called Ernst Leitz GmbH, Wetzlar. It goes into much detail about how Leicas, Leica lenses, and other Leica equipment are being made. Obviously,
virtually all of the machinery and testing instruments have been replaced by
modern counterparts, but it is a great account of what needs to be done to be
on top of the quality curve in this industry.
The main factory of Ernst Leitz, GmbH, at Wetzlar with the Kalsmut ruins in the background.
A VISIT TO THE LEITZ FACTORY
By F. Neumann
For many of the thousands of
visitors who come every year to Wetzlar, the name of this ancient free imperial
city is bound up with the conception of Leitz and the Leica – symbol of
precision optical equipment.
It is therefore not
surprising that the Leitz factory exerts greater attraction than the
slate-covered old town buildings around the venerable cathedral or the Goethe
memorials.
We recently had the
opportunity of taking part in a visit to the factory.
This may comprise a brief
half hour’s visit to two or three representative sections, but it may stretch
over days where in special cases – e.g. for a news report – detailed
information has to be collected. The
wide production program, the extensive factory with its many departments, offer
such an abundance of material that it is difficult for a reporter, as indeed
for the guide in a conducted tour, to stick to essentials.
The visitor and – likewise
the reader – will have each his own particular interests. All, however, must commence their tour at the
same spot, the progress “from glass block to Leitz objective”; for glass is the
essential element of all Leitz products.
Whether as a prism, mirror or lens, high quality glass is worked into a
high grade optical system in the form of an objective, a prism combination for
a rangefinder or an illuminating system.
In combination with delicately fashioned mechanical components it
constitutes a the very heart of the opto-mechanical precision instrument.
From glass block to finished lens
In the glass store
We begin our round at the
glass store. This contains more than 200
different types of glass, all needed in current manufacture. From them are made, as components in
manufacture, about 5000 different types of lenses and prisms. Well over 1000 types of lenses and special instruments
go to make up the manufacturing program.
The glass is stored in form
of large square or rectangular blocks.
Picking up two such blocks of about the same size, one may be struck by
a very great difference in weight. We
are told that the heaviest glasses are also the most expensive, and that the
various types differ widely among themselves both in their characteristics and
in their stability to outside influences.
The glassworks also supply optical glasses in the form of rods from
about 5 to 25mm diameter and also as molded blanks (for large scale series
production) already shaped to the form of the finished lens of prism.
Slitting
From the glass store we
proceed first to where the glass blocks are cut up. Diamond saws slit the blocks into plates of
the required thickness. The plates are
then ground plane parallel with abrasive powder and cut up.
Edging
The individual cut-up plates
are cemented together in a stack and edged circular on special grinding
machines. Bat moldings simplify this
first working process, because they can be slit right away to the blank
thickness.
Surfacing
In the next process the
circular discs are shaped in the milling machine to the rough shape of the
lens. The molded blank is already
supplied in this form, and so eliminates the slitting, cutting-up, and edging
process. Unfortunately for high grade
lenses and for small series, or for very small lenses, molded blanks cannot be
used.
Spherical and plane surfaces
The next stage in the
manufacture of lenses is machining to radius and thickness, and in the case of
prisms, facing and machining to angle and dimensions.
A glimpse into the glass store
showing some of the glass blocks.
A diamond saw has penetrated the glass block and
is cutting it into plates of the requires thickness.
The plates cut from the block are cemented into a
stack end edged on a corundum wheel edging machine.
Grinding glass plates plane parallel.
A block of lenses is removed from the polishing tool.
The blocks of lenses are smoothed and polished on
a multi-spindle polishing machine.
Grinding and polishing
The first stage in surfacing
lenses is to cement them on a blocking tool with adhesive foil or sealing
wax. They then go through a succession
of stages of smoothing, using special moistened abrasives. Depending upon the radius of curvature and
the size of the lens a great variety of tools may be employed. In the case of the very smallest lenses, as
for instance the front lens of an oil immersion objective, the most skilled
hand work is called for. Years of
experience and an innate delicacy of touch are prerequisite for this highly
specialized work. This is equally true
of the final stage in the production of prisms of the highest precision.
The term highest precision
here means that its assessment is beyond the scope of any mechanical method of
measurement, and can be achieved only with the aid of optical phenomena (e.g.
interference).
What is meant by highest precision?
To take an example, the
polygonal prisms required for technical measurement purposes must be accurate
to one second of arc. This means that
the surface must be flat to within limits corresponding to a radius if
curvature of 30,000 meters (98500 feet).
To give this more practical significance, imagine a traffic policeman in
Paris standing with outstretched arms at the Place de la Concorde, and lines
drawn from his fingertips to London, meeting on the face of Big Ben. The angle formed by these two lines, 400 km
(249 miles) long with a base of 2 meters (6.7 feet) will be one second of arc.
Prisms from crystals
Infrared spectrographs
incorporate dispersion prisms with a base of 150 to 170 mm. The requisite crystals are grown in the Leitz
crystal laboratory. Crystals od such
dimensions and the necessary purity are rarely if ever found in nature. Among other artificial crystals are sodium
chloride, potassium bromide, and caesium bromide. The optical working of such crystals makes
the utmost demands on technical and manual skill, because by reason of the
hygroscopic properties of the crystals and careless handling, for instance,
would leave behind blemishes which could be removed only by long and tedious
work.
It is therefore
understandable that entry into the specially air conditioned and dust protected room cannot, regrettably, be
permitted.
Machine working
In the manufacture of large
series, a high degree of automation and rationalization is achieved by the use
of multi-spindle grinding and polishing machines. A high pitched monotonous whistling and
squeaking sound assails our ears, while our eyes are hypnotized by the
unceasing rhythmic motion of the tools.
The ever watchful eyes of operators are fixed on their machines. When the grinding and polishing operation is
nearing its end, the block of lenses is removed. Careful, almost lovingly, the experienced
hand of the expert operator strokes the surface of the lenses as with critical
eye he judges how far the process has progressed.
A test plate (negative master) polished to the prescribed
curvature, is brought into contact with the surface of the
lens under test. The configuration of the Newton's rings
formed indicate any deviation from the correct curvature.
Correction is then applied in further polishing until the
rings disappear completely.
Testing prisms.
Testing thickness of lenses with a dial gauge.
Testing
In between the individual
working stages repeated progress checks are made to establish surface quality
and maintenance of lens thickness and diameter.
The quality of the surface is checked with a test plate (negative master). This is polished with extreme accuracy to the
prescribed curvature, and for the purpose of the test is brought into contact
with the lens tested.
If the curvature of the lens
is not identical with that of the test plate, interference bands, commonly
known as Newton’s rings, make their appearance.
Their number and regularity provide a reliable indication of the quality
of the surface. Next follows testing of
the surface for freedom from blemishes and the presence of bubbles, measurement
of thickness, and of interfacial angle on the autocollimator. When one sees how many individual operations
every lens, every prism, has to be put through, one can readily appreciate that
it is a long, long way from glass block to finished objective or prism
combination. There is an enormous range
from the smallest to the biggest lens.
Lenses used in microscope objectives are scarcely larger than a pinhead,
while the condenser lens of a large projector measures twenty inches in
diameter.
Centering
The polished lenses are then
centered on the centering bench and then on the edging machine edged
concentrically to the required diameter.
Coating
One important operation still
remaining is coating. In the coating
department is installed high vacuum equipment with which certain substances are
coated on to the glass surface to form a thin reflection preventing layer. This reduces reflections in the glass-air
interface to a minimum, thereby considerably increasing the transmission, and
therefore the effective speed of the lens.
A still more important function of this layer, however, is its effect in
minimizing scattered light due to surface reflections, which has the effect of
reducing image contrast. Coated surfaces
produce practically no scattered light, and the contrast and brilliance of the
image is in consequence greatly improved.
Examination of the front lens of an oil immersion objective
with a magnifier.
The lens coating department.
The lens coating department.
Preparatory to cementing a pair of lenses the lower component is
coated with slightly warmed canada balsam.
In the cementing shop
One of the last processes the lens has to go
through before mounting in its metal mount is seen in the cementing shop. Both flat-surfaced and spherical surfaced
optical parts in some cases have to have their surfaces cemented together; hot
cementing is done with canada balsam, cold cementing with Araldite.
Mounting
When the sets of individual
lens elements have completed their passage through the optical workshops they
pass through into the mounting shop.
Here they are mounted up at their prescribed separations in accordance
with the working drawings. The ready
prepared mounts are given their finishing cut, the lenses are inserted, and
centered by the reflected image method: they are so adjusted that their centers
and curvature all lie on one straight line, the optical axis of the lens.
Diaphragm ring, distance
scale, and depth-of-field ring complete the outer mount of the finished camera
lens.
Behind closed doors
As we are standing at the
bench where the 50mm Noctilux lens is assembled, a visitor asks about the
machines on which the aspherical lenses are made. In a moment we are plunged into an
interesting conversation. We gather,
however, that for security reasons it is impossible for our guide to show us
these machines. The quantity production
of aspherical lenses for use in the construction of extreme wide aperture
lenses is, we are told, the most important advance that has been made in recent
years.
From raw material to precision instrument
Metal working is a process
with which we are all familiar. Almost
everybody at some time has had an opportunity to look inside a fitting
shop. Lathes, milling machines,
lacquering shops, modern automatic machinery for dozens of different working
processes – all these are to be seen in the reports of all manner of industrial
plants brought to us daily since cinema and television have made audio-visual
communication so easy. Nevertheless an
actual conducted tour of a factory remains a special experience. Nothing can rival its immediacy. The sounds and odors, the atmosphere of the
work bench, these things can only be fully appreciated by an actual visit to
the scene.
Similarly it is impossible to
convey be mere description the quality of precision mechanism such as is
embodied by long tradition in Leitz instruments. For this we must stand side by side with the
precision mechanic, bringing, however, to the occasion a degree of sympathy and open mindedness.
Our guide is well chosen: he is
well versed in his subject, for he was for many years himself employed as
production engineer. He leads us through
labyrinths of countless departments so that in the end we really come to
believe that we have completely got the hang of the factory set-up, and have in
our mind’s eye a complete picture of the whole production scheme.
In the material stores
In the material stores we see
the raw materials of manufacture: steel, brass, bronze, aluminum, and
plastics. In Store 1 are housed the
castings. We examine the numerous housings
and components; we learn how the machine produced casting is better from the
finished point of view than the hand casting, for it is important in precision
mechanical work that the rough casting should have as clean a surface as
possible. In this department we see
quite small castings, as well as castings measured in yards, as used for
building the bulky measuring microscopes and big projectors.
In the semi-products store
are sheet metal, tuning, rods, and other profile material. We soon discover certain parallels between
this tour and our visit to the optical workshops.
Grinding and annealing
Here plate shearing takes the
place of the slitting of the glass blocks.
Glass rod becomes here metal profile, and molded glass blanks have their
equivalent in metal. First we follow the
casting through its successive operations.
The first process, in the grinding shop, is to clean the casting inside
out. Next it goes into a large furnace,
in which it is annealed to remove any internal stress. We are told that this annealing process is
repeated an number of times during the course of machining, because complete
freedom from internal stress is essential to high precision.
In many cases the precision
mechanic also carries out inspection, and his work bench is accordingly
equipped with the requisite instruments.
As in the optical bench there are many such measuring and checking
instruments, and these are made in the Leitz factory.
The workpiece becomes an individual
Right in the first stages of
finishing we witness what our guide terms “the birth of the individual”, and we
very quickly come to realize an important fact, namely that from now on the
workpiece must be carefully handled as the individual that it is. Storage and transport are just as important as
the work itself. In the next room it is
literally a case of holding one’s breath – we are only permitted because we are
a small group. Any surface
contamination, even the moisture of one’s breath, would lead to malfunctioning
of this delicate measuring equipment, with consequent expensive reworking. One of our group was a very devoted photographer. His remark was: “I quite see what he means;
if anyone were to bend over my unglazed transparencies I would instinctively my
breath for him”.
60 ton hydraulic press in the stamping shop.
In the turning section
Before proceeding to the
heavy component section, we take a look in the turning section. We have already referred to semiproducts, and
here can see for instance how in a semi-automatic lathe a steel rod in a matter
of seconds is first cut off, and the cut-off section is from the other side
provided with a variety of profiles and screw threads.
One other thing we notice in
the turning section: a small chart such as is to be seen hanging in every other
department. At first glance it seems to
contain only a few numerical data.
Nevertheless behind them is a carefully worked out system of production
control.
We are told that years ago
Leitz adopted a policy of leaving virtually nothing to chance. It is not enough to buy good materials,
process them accurately, work exactly to plan.
Turner at lathe.
Plates for the Leica shutter being drilled and countersunk on an
automatic multi-spindle drilling machine.
An automatic computer.
Milling operation on a Profile Projector.
Production control picks up
every error, records it on punched cards, assesses precisely its significance,
and can then quickly and effectively eliminate the cause. And not only does it thus deal with errors,
it also assesses efficiency. At the end
of the month it pays out in hard cash if a team has exceeded its “qualitative”
norm.
Human skill and automation
A few steps further we
encounter a fully automatic machine and take a look at its interior. The programming strip reminds the older among
us of the earlier electric pianos. This
not surprisingly leads us into a philosophic discussion. Fro everyone with imagination must realize
the enormous extent an diversity of the technical progress involved.
A fully automatic machine of
this kind not only performs its various tasks automatically, it does so with
high precision. On the other hand one of
the more striking convictions we came away with from this visit was that man of
the future was not destined to degradation to the status of machine minder.
What a miserable existence
such a robot must lead without its master. He it is that must be responsible
for keeping up to date; he works out the programs without which not a wheel can
turn. Man must remain indispensable, not
only intellectually, but also by virtue of his manual skills. To this, the precision mechanic is an
eloquent witness.
The computer
Just as we had got on the
subject of “electronic brain” in general, our guide tells us that we happen to
be quite close to a computer. So his
suggestion that we should have a look at it is enthusiastically received.
Our guide explains that we
are not going to the date processing department, but to see how computers are
used by those responsible for the design of Leitz lenses and optical
systems. Calculation which formerly not
only used to occupy weeks, but which also had to be restricted to within a much
less comprehensive scope, today are carried out by computer in minutes. Thus quickly and precisely – for the machine
operates just as efficiently after eight hours’ work as at the beginning of the
day – it is possible to verify whether one I on the right track or whether and
where corrections will be necessary.
Without the use of computers the results of the research into high
performance new optical glasses could not have been exploited to maximum
advantage. We are permitted to look
inside the machine. The technician in
charge explained to us what are the important things to bear in mind in
operating and servicing. We leave the
room convinced that a modern lens, and its continual improvement, is the result
of glass research and optical calculations.
Lacquering the framework of the
Optical Master Dividing Head.
Finishing large components
A few minutes later we are on
our way again “from raw material to precision instrument”. In the large component finishing department
we see once again various housing which we have already met with on numerous
occasions at various stages: the support for the large projector, the modern
“angular” housing for the microscope, the classical curved stand.
Leica and Leicaflex production
We ask about projectors,
about the Leica and Leicaflex, and are told that this work is carries out in
other shops and other factories.
At the railway station
factory is the assembly line for the Pradovit Color and Pradolux miniature
slide projectors.
In the new Weilburg factory
we are shown the finishing of the aluminum pressure cast body of the Leicaflex:
modern production lines, multiple spindle drills with which some 65 holes can
be drilled at a single operation.
Surface finishing
The next basic process after
the large component finishing process is surface treatment. The moment we enter we are struck by a
typical odor; this is where electroplating, anodizing, lacquering are done. The components or housings to be treated are
suspended on frames which are then immersed in the chemical solutions’
contained in large tanks. Immersion,
removal, and further transport are all preformed automatically.
As in the production,
everything here has become a matter of rationalization. The flow pattern must be as smooth as
possible. That is why visitors to the
factory present something of a problem.
The floor is always moistened again immediately, for dust is the
greatest enemy. Not everything is automatic;
there is also hand work, individual work, according to the nature of the
operation. This is, after all, not a car
factory, but a section and individual working.
Here hundreds, thousands of different components are manufactured. Consequently, notwithstanding all the
rationalization and simplification of manufacturing processes it is almost
impossible to carry out all the operations of manufacture from raw material to
final assembly on a conveyor belt.
“unfortunately” says one –
“fortunately” another.
In the electroplating department.
Assembly of the camera shutter.
Mounting the self-timer in the Leica.
Optical set-up of the Leicaflex lenses is being checked.
The pressure-cast aluminum body of the Leica on the production
line. Altogether 274 operations are carried out on it by milling,
drilling and screw cutting machines.
Testing and adjusting the reflected image of the Leica
bright line view and rangefinder.
Dust-free packing of the Leica.
The Leicaflex body consists of a light metal casting completely
resistant to distortion. This guarantees, among other things,
perfect parallelism of the lens and film plane.
Testing and adjustment and functioning of
the flash synchronization of the Leicaflex.
Using the Optical Master Dividing Head
on a surface grinder.
Precision grinding
Only after the completion of
the surface treatment is precision grinding carried out, on grinding or lapping
machines, or by hand scraping. This is
the last stage before the metal components meet their optical
counterparts. “You see now” says our
guide, as in the materials store of the assembly department we continue our
conversation about the essentials of opto-mechanical precision instruments,
“why the mechanical components must be made with the same precision as the
optical parts?”
Assembly
A chain is only as strong as
its weakest link. In assembly,
therefore, quality and precision are of the utmost importance. For this is where optical and mechanical
parts are assembled so as to become one unit.
The optical axis must not be distorted.
The assembly process is not just a matter of adding component to
component on the unit construction principle; frequently it is possible by
setting on manufacturing tolerance against another, and by making final
adjustments in assembly, so to improve performance that plus and minus errors
are mutually balanced to zero.
The Optical Master Dividing
Head – to take once more an instrument which is manufactured to the highest
standards of accuracy with corresponding precision of performance – is finally
reground ready mounted in the position in which it will later be operated. Incidentally this Optical Master Dividing
Head has played an important part in the development of space travel. It is used to orient the control platform.
Assembly might be basically
divided into three stages: subgroups – groups – final assembly.
How many parts are assembled
at any one time is of course very different with different instruments.
Routine production controls
particularly attracted our attention. As
photographers we are often more intrigued by portraits of these specialists
than with what they are doing.
Every now and again we see a
team working in a “glass case”. Here
there must be neither dust not too much or too little humidity, the temperature
must be rigidly controlled and the room can only be entered or left through an
air lock.
Portrait of an adjuster
Portrait of a microscope objective lens examiner.
In photographic assembly we
once again gather around a large glass enclosure. Here is to be seen a complete Leica
dismantled into its components: a graphic recapitulation of our tour and a
convincing documentary display.
We discuss the problems of
distribution of production and manufacturing preparations; how extensive is the
necessary organization to ensure that all the components required reach the
assembly point in the right numbers and at the right times so that, for
example, in accordance with the production schedule Batch 284 can be assembled
in the 27th week and is for dispatch according to contract in the 34th
week.
A hundred years ago – a retrospect
It is appropriate here to
take a look back at what things were like a hundred years ago, and what slender
resources Ernst Leitz had at his disposal when he took over the small factory
in 1869.
The first inventory:
“Four lathes, two of them
iron, the other two wood. Four bench
vices. Four racks for files and
chucks. Seven oil lamps, five hammers,
two screw calipers, two dies, two hand drills with drill bows, pliers, files,
saws, one small and one large bottle of varnish.
Today
Today the factory turns out
more than 5000 salable articles. Today
it is not sufficient to look through the microscope: quantitative measurements
are demanded. To every “scope”, or
observation instrument, there is a corresponding “meter”. But even measurement often does not suffice;
permanent records are wanted, so the “graph” has to be added. Deviations have to be corrected, and
inevitably we reach the point where the measuring instrument itself makes the
correction. This is born the “star”
which maintains conditions constant.
Finally the “mat” brings in automation to raise the instrument to its
highest development plane. Such is the
long but systematic path from the first great advance in design, the
orthoscopic eyepiece, to the fully automatic photomicrographic camera, the
Orthomat.
Many factors played their
part in this:
For the manufacture of high
performance microscopes, instruments of high precision were needed for
measurement and materials testing. They
likewise had to be designed and manufactured.
The materials used had to be tested for quality before they could be
used, and from the outset the opinion was held that quality control was a
practical proposition. So Leitz became
at the same time manufacturer, buyer, and customer. Their customers throughout the world are
beyond count.
This too is Leitz
Leitz not only manufacture
their products: they also test them with special equipment largely developed by
themselves. This constitutes a double, a
triple guarantee of highest precision and quality.
The testing system
The testing system of modern
precision manufacture is a quite specialized domain. It is independent of the development and
manufacturing departments, and has two tasks to fulfill:
1. Evaluating and testing out new developments
2. Final testing of all products
This applies to every
department of manufacture: microscopy, metallography, photography, projection,
measuring equipment, etc. Special
laboratories with equipment for research and testing are at the disposal of all
branches of the factory. A great
responsibility falls on the optical laboratory for the testing of lenses. This is where the optical data of lenses are
determined and their entire performance investigated. Electric and electronic constructional
elements and equipment are tested in the electrical testing room and
photographic equipment in the testing laboratory. Among the facilities available to the testing
department are large refrigerated testing rooms down to -60 áµ’C, accessible to inspection, refrigerators down to -80 áµ’C, air conditioned containers for the maintenance of
any desired climate conditions, fog, spraying, and sprinkling devices, jolting
machines, and vibration, shock, and pressure testing machines.
And so this widely extended,
skillfully coordinated testing organization provides the sound basis for the Leitz guarantee of consistent quality
and reliability of all its products.
It is characteristic of Leitz
production that besides a great deal of very successful commercial apparatus,
other products have been developed the idealistic value of which counts more
than material success.
This adequate motive for the
development of trichinoscopes, tyndalloscopes (dust counters for mining, etc.),
and other scientific instruments existed in this spirit of awareness to have
resulted in valuable contributions to the welfare and health of millions and
fundamental advances in scientific research.
Refrigerated room for testing Leica and Leicaflex
functioning under arctic conditions.
Part of the microscope laboratory.
Students taking part in a course of microscopy at the Leitz Works.
Part of the construction design section at the Leitz works.
In the design section.
The administrative buildings of the firm of
Ernst Leitz GmbH in Wetzlar.
Please note: This report was written prior to Ernst Leitz
GmbH splitting up into the four independent companies that bear the Leica name
today, Leica Camera AG, Leica Microsystems, Leica Biosystems, and Leica
Geosystems. The philosophy of utmost
quality and performance continues to be a very important aspect of all four
companies.
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