Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
1999-03-03
2001-03-13
Epps, Georgia (Department: 2873)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C250S548000, C250S201100, C250S201400, C250S201800, C356S399000, C356S400000, C356S401000, C396S104000, C396S120000, C359S389000, C359S390000, C359S800000
Reexamination Certificate
active
06201254
ABSTRACT:
DESCRIPTION
1. Field of the Invention
The present invention relates to a system for determining whether an object whose image is to be recorded, is aligned with a coupling eyepiece and an image capture apparatus and, in the case of non-alignment, for quantifying the position setting that is required on the components of the system in order to achieve said alignment.
The invention may have applications in any sectors concerned with the creation of optimal quality images of an object on an image plane through an eyepiece, particularly in the medical sector.
2. Background Art
In the field of image capture, specialists in the field attempt to achieve images of the highest quality possible, in other words with satisfactory focussing of the capture system and the best possible image definition.
In order to obtain an image of excellent quality, the image plane, i.e. the plane in which the image capture apparatus lies, must be perfectly aligned with the coupling eyepiece on the one hand and with the object on the other. However, the alignment is difficult to effect as the orthogonality of the image plane must be adjusted according to the optical axis and to the focal distance.
Also, in order to create images of an object on an image plane through an eyepiece, it is necessary to obtain optimal positioning between the object, the eyepiece and the image plane. The optimal positioning can be achieved by means of settings that are usually made between the positions of the eyepiece and the capture system (i.e. the image plane). The object is generally positioned so that it is fixed. There are two kinds of settings:
a setting, by means of rotation, of the perpendicularity of the image plane in relation to the optical axis of the eyepiece; and
a setting of the image plane position, i.e. the capture apparatus, in relation to the eyepiece; this is the standard type of focus setting used in an ordinary camera. The setting is made by means of a translation movement along the optical axis, and enables the image plane, i.e. the plane of the image recording apparatus or the capture system, to be focused on the object plane, i.e. the plane in which the object to be recorded lies.
Generally, the object is at a variable distance from the eyepiece. The eyepiece/image plane setting can therefore be made either approximately or visually by the operator using range finding or reflex means.
Some image recording apparatuses are even equipped with a system for measuring the object/eyepiece distance that measures the distance between the object and the eyepiece using an ultrasound or infrared method. In this technique the eyepiece/image plane setting is made automatically.
However, in these standard apparatuses, the depth of field at the eyepiece is significant. The eyepiece/image plane setting is therefore not always accurate.
Moreover, applications exist in which the eyepiece/image plane setting is finer, for example in electron microscopy. In electron microscopy the operator can adjust the eyepiece/image plane setting visually. The operator can also make the setting using a technique known as the “wobber focusing aid”. The technique is described on pages 29 to 31 of “The Principles and Practice of Electron Microscopy” by Ian M. Watt (Cambridge University Press). This technique consists in oscillating a luminous beam between two positions in relation to the lens of the image recording apparatus. This produces a double response of the object observed on the image plane until the system reaches optimal focusing.
However, these “wobbling” methods are difficult to implement as it is not easy to deflect the light source.
In astronomy, it is also useful to have fine setting, particularly when a CCD camera is used in combination with an astronomic eyepiece as described in the article “Une Mission Haute Résolution au T 60” (A High Definition Assignment at T 60) by J. Dijon et al., published in Pulsar magazine No. 707, March-April 1995. The article describes a method that enables a relatively sensitive eyepiece/image plane setting to be achieved. The method consists in selecting a single star, positioning a two-holed mask at the entry of the astronomic eyepiece and verifying the number of patches of light that appear on the CCD image recording apparatus. If the CCD camera is not correctly focused in relation to the eyepiece, two patches appear on the camera. If, however, the focusing is correct only a single patch appears on the CCD camera. By displacing the projection of the star over different areas of the CCD camera, the alignment of the eyepiece/CCD camera can be adjusted, in other words it is possible to adjust the alignment between the eyepiece and the image plane.
However, this method can only be used for an object located at infinity, as is the case in astronomy.
Other optical methods enable the orthogonality of the image plane with the optical axis to be adjusted. One method consists in using an autocollimation eyepiece that is placed on the entry of the eyepiece. In this example, the image plane must provide a reflection for this kind of setting. Moreover, difficulties may arise when other reflective planes are present on the trajectory between the eyepiece and the image plane, as is the case in a CCD camera being used through a glass window.
A method of this kind therefore proves difficult to put into operation. Also, this method only provides the setting required for surface evenness, it does not provide the setting for focusing required to align the system.
DISCLOSURE OF THE INVENTION
The aim of the invention is to overcome the drawbacks of the techniques described above. In order to do this, the invention provides a system for determining whether an object is aligned or non-aligned with the coupling eyepiece and the image capture apparatus and, in the case of non-alignment, for quantifying the settings that are required on the system in order to achieve alignments of said elements.
In order to achieve this, the system of the invention uses an image capture apparatus and a light source to create a group of luminous dots and an opaque mask perforated with at least two holes through which the light passes, the images of said luminous dots on the image plane being split into two if the system is not correctly aligned. Analysis of the said split images is used to quantify the setting of the system that is required to achieve alignment.
More precisely, the invention relates to a system for determining the alignment of an object, whose image is to be recorded, with a coupling eyepiece and an image capture apparatus that defines an image plane. The system is characterized in that it comprises:
an image capture apparatus equipped with setting means for its own positioning;
a light source that is movable in the object plane and that emits at least two non-focused luminous dots; the source produces:
a luminous dot if the evenness of the detector has no significant influence on the quality of the alignment; or
at least three luminous dots under normal conditions; moreover, the three dots can be produced by:
a source that creates three luminous dots simultaneously;
the displacement of a dot-type light source in three places;
eyepiece coupling means focusing on an object plane and ensuring the coupling of an image in the image plane with an image created in the object plane;
a removable opaque mask perforated with at least two holes and placed in front of the light source so as to transmit at least part of the light that is emitted by said light source, the light transmitted through each hole in the mask creating at least one image of a luminous dot on the capture apparatus, said image being split into two if the elements are non-aligned; and
means for determining whether alignment exists and, if there is no alignment, for quantifying said non-alignment.
The means for determining whether alignment exists are, for example:
means for displaying the image (for example a screen); or
computing means in order to evaluate the extent of the split, i.e. the distance separating the two patches produced by a single luminous do
Commissariat A l'Energie Atomique
Epps Georgia
Lester Evelyn A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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