临界照明、柯勒照明的出现

------来源：Steven Ruzin Ph.D., University of California, Berkeley

 

 

 

 

 

 

 

 

 

 

临界（或者尼尔森）照明Critical（or Nelsonian）Illumination、柯勒照明Köhler Illumination；生物显微镜方面的介绍，资料较为好搜寻，可是，金相显微镜的，就感觉是“被嫌弃”的意思。

 

Edward Milles Nelson、August Köhler，到今天，柯勒照明，似乎尽人皆知。

 

维基百科中有柯勒的词条，却没有尼尔森的词条。

 

 

临界照明词条有一个标签：

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http://microscopy.berkeley.edu/courses/tlm/condenser/history.html  The microscope illuminator and condenser are designed to illuminate a transparent sample with transmitted light.

Absorption of light generates the contrast that we see; either by selective wavelength absorption （imparting color）or by intensity attenuation.

 

 

Edmund Culpeper（1670–1738）was the first to place a mirror under the sample so that light would be transmitted through the specimen. This is a late Culpeper compound microscope from about 1730.

 

 

A few years later, opticians added a second reflecting surface to the illuminating mirror. This surface was concave, which provided a higher quality, focused light on the sample.

This is a mirror on a Benjamin Martin microscope from around 1775. One surface is flat, and the other is curved.

       Until late in the 19th Century, samples were illuminated only by light reflected by a flat or concave mirror.

 

Critical Illuminating

 

In the late 1800s, Edward Milles Nelson invented a lensed device that presented a focused beam of illuminating light onto the sample. This device is known as the Substage Condenser. The illumination method is called Critical Illumination. Nelson designed microscopes for the Powell & Lealand microscope company. Left is an example of a Powell & Lealand instrument with a Critical Illuminating substage condenser. The microscope is from c1868.

 

 

Köhler Illumination

 

The latest advance in sample illumination was invented by August Köhler in 1893 for the Zeiss microscope company. The example shown here is a 1905 Leica microscope equipped with a Köhler illuminating condenser. Köhler Illumination

 

http://microscopy.berkeley.edu/courses/tlm/  Techniques in Light Microscopy

 

F2016/ PMB 185

CCN: 26116

 

MWF 9-10AM

138 Morgan Hall

3 Units

Steven Ruzin Ph.D.

CNR Biological Imaging Facility

381 Koshland Hall

 

The course will be a detailed overview of the practice of light microscopy as applied to scientific investigation. The emphasis of the course will be on the use of the light microscope by biological scientists, however students of other disciplines are welcome. We will cover optical microscope theory, microscope components and mechanics, and all modern optical techniques from Brightfield through Deconvolution microscopy, Structured Illumination, and others. Instruction will consist of lectures, demonstrations, and practice using the light microscopes in the CNR Biological Imaging Facility and the GPBB Teaching facility.

 

Laboratory: The laboratory is in 208 GPBB, and will consist of one session per week:

Section 101 （CCN 26117） Friday 1–4PM, 208 GPB

 

Grading: There will be a Midterm written exam and lab practical, plus a written Final Exam. For labs, students will be required to complete at least one worksheet for each of the labs. Worksheet is due at the end of that lab. In addition, a project is required for the class. It consists of a written paper describing your forensic analysis of an unknown white powder.

 

Office hour is Wednesday 4-5PM, or by appointment.

 

http://www.sgaaa.com/news/2014123234716.htm  常见的光学显微镜聚光器有三种类型-仪器常识

时间:2014-12-3 23:47:16  来源:yiyi

常见的光学显微镜聚光器有三种类型-仪器常识

复式显微镜的第三个光学部件称之为“台下聚光器”。标本载玻片置于物镜下的台上。这个台叫做“载物台”，台下区是在载物台下方。有些显微镜，光从一镜面反射通过台下聚光器来照明标本。今天许多显微镜已有内装的台下照明，这样就用不着单独的平面镜了。无论哪种情况，光都是直接通过台下聚光器并且在标本处会聚成很小的一个面积。光线通过标本时再分散并形成一个倒立的圆锥体，其底部的大小正好充满物镜的孔径。

光束进人聚光器的大小由聚光器下的一可变光阑来控制。这个光阑叫做“孔径光阑”。聚光器的焦点与光阑的开放都是为调节柯勒照明用的。

可采用的台下聚光器有三种，阿贝聚光器是最简单、最便宜的一种。大多数的显微镜都装用它，除非标明用另一种类型。这种聚光器未经光差校正，可由二或三个透镜单元组成。在低倍镜（10×或10×以下的物镜）下工作时，顶部的这一单元有时可以通过旋松螺丝或者从支架上拧开而除去。在中倍及高倍镜下工作时则使其保持原位。在用低倍物镜时，如果不除去顶部单元就可能无法将整个视野全照明。

 

https://en.wikipedia.org/wiki/Critical_illumination  Critical illumination

Critical illumination or Nelsonian illumination is a method of specimen illumination used for transmitted and reflected light （trans- and epi-illuminated） optical microscopy. Critical illumination focuses an image of a light source on to the specimen for bright illumination. Critical illumination generally has problems with evenness of illumination as an image of the illumination source （for example a halogen lamp filament） is visible in the resulting image. Köhler illumination has largely replaced critical illumination in modern scientific light microscopy although it requires additional optics which less expensive and simpler light microscopes may not have.

       Optical principles

The optical setup and light path of critical illumination showing the conjugate image planes of the various optical components.

Critical illumination acts to form an image of the light source on the specimen to illuminate it. This image is formed by the condenser or collector lens. This illumination is bright but not always even, as any structure in the light source （for example the filament of a light bulb） will be visible in the resulting image. Homogenous light sources such as a flame or sunlight give more even illumination. Alternatively, a ground or opal glass diffuser can be used to homogenise the light source, but this will cause a significant amount of light to be scattered away from the sample.

See also

Optical microscopy

August Köhler

 

https://en.wikipedia.org/wiki/Köhler_illumination  Köhler illumination

Köhler illumination is a method of specimen illumination used for transmitted and reflected light （trans- and epi-illuminated） optical microscopy. Köhler illumination acts to generate an extremely even illumination of the sample and ensures that an image of the illumination source （for example a halogen lamp filament） is not visible in the resulting image. Köhler illumination is the predominant technique for sample illumination in modern scientific light microscopy. It requires additional optical elements which are more expensive and may not be present in more basic light microscopes.

Prior to Köhler illumination critical illumination was the predominant technique for sample illumination. Critical illumination has the major limitation that the image of the light source （typically a light bulb） falls in the same plane as the image of the specimen, i.e. the bulb filament is visible in the final image. The image of the light source is often referred to as the filament image. Critical illumination therefore gives uneven illumination of the sample; bright regions in the filament image illuminate those regions of the sample more strongly. Uneven illumination is undesirable as it can introduce artefacts such as glare and shadowing in the image.

Various methods can be used to diffuse the filament image, including reducing power to the light source or using an opal glass bulb or an opal glass diffuser between the bulb and the sample. These methods are all, to some extent, functional at reducing the unevenness of illumination however they all reduce intensity of illumination and alter the range of wavelengths of light which reach the sample.

In order to address these limitations August Köhler designed a new method of illumination which uses a perfectly defocused image of the light source to illuminate the sample. This work was published in 1893 in the Zeitschrift für wissenschaftliche Mikroskopie [1] and was soon followed by publication of an English translation in the Journal of the Royal Microscopical Society [2]

Köhler illumination has also been developed in the context of nonimaging optics.[3]

 

The optical setup and light path of Köhler illumination showing the conjugate image planes of various optical components.