WO2003101089A1 - Miniaturised camera - Google Patents

Abstract

The invention relates to a miniaturised camera with a photosensitive CCD matrix arranged in a rod- or tube-shaped housing and an integrated illumination device, in particular for application or use in a dental diagnostic instrument. In the head end of the rod-shaped housing a recess is provided, in which an optical plate with aperture openings or adjustable diaphragm is arranged. An objective lens is provided to the incident light side, behind the aperture opening and the CCD matrix is arranged, preferably in the head end, at a focal separation which is adjustable. According to the invention, the light necessary for illuminating the object is coaxially injected into the objective beam path. The objective lens and the CCD matrix are arranged in the form of an image sensor on an actuator or are connected thereto such as to achieve a linear displacement along the beam path. A camera electronic circuit carries out a continuous monitoring of the high frequency signal components from the image sensor. Furthermore a control device is provided for the actuator, whereby the control device generates the linear displacement such that a maximum high frequency component is obtained or regenerated.

Description

 Miniaturized camera

description

The invention relates to a miniaturized camera with a photosensitive CCD matrix arranged in a rod or tubular housing and an integrated lighting device, in particular for use in a skin or dental diagnostic instrument, a recess being provided in the head end of the rod-shaped housing. into which an optical plate with an aperture is inserted, according to the preamble of claim 1.

From the international patent application PCT-WO 99/06871, a camera, in particular a modular dental camera, is known, which comprises a housing in which an optical system for imaging an object field, an image sensor that records the image of the lens, and an illumination unit are arranged are. To switch the object field between a small object field and a small recording distance and an overview recording with a large recording distance, a functional element is provided which simultaneously focuses on the respective recording distance and the diaphragm from a small opening with a small recording distance to a large opening with a large recording distance and reversed switches.

With the aid of the switchover, in particular the depth of field should be adapted to the particular application, in order to be able to take a detail of the teeth and then take a picture of the patient's head in a dental camera with one and the same device.

The focusing according to the known solution is carried out by moving the CCD image sensor or by moving the lens, but preferably by moving an optical assembly of the lens itself. The functional elements rely on a translation or rotation movement and can also work electrically. A sensor button should or a similar switching device can be provided so that the user can easily set the various operating states. Furthermore, the functional element should have a control loop that detects, for example, the focusing via a sensor, so that an autofocus system can then be implemented.

With the previously known solution, it is therefore imperative that an external sensor or a button is available, via which the switchover function is triggered. For an autofocus system, in turn, a further sensor is necessary, so that overall the costs for such a dental camera are increased and a large number of functional elements with a naturally higher probability of failure have to be integrated into the camera housing.

In the published patent application DE 100 49 835 AI, a miniaturized camera with a photosensitive CCD matrix arranged in a rod or tubular housing is assumed, the camera comprising an integrated lighting device.

An optical disc present there has a coating which is impermeable at least in the visible spectral range, preferably a rear-side coating, this coating being interrupted for a diaphragm opening of small diameter and larger lighting openings arranged around the diaphragm opening. On the light entry side, a lens is attached behind the aperture, preferably directly on the optical plate. The CCD matrix is located at a predetermined focus distance from the lens. Below the aforementioned lighting openings, light-emitting diodes, preferably white light-emitting diodes, are attached as radiation sources, the coating of the optical plate preventing the direct coupling of radiation from the light-emitting diodes into the optics, consisting of the aperture and lens, so that optical crosstalk is avoided can be avoided.

In a further development of the invention there, it is possible to arrange one or more optically dense media in the space between the lens and the CCD matrix for changing the focus. For example, a sapphire crystal can be brought into the space via a movable slide. To this In this way there is the possibility of gradually changing the focus. The aforementioned movable slide for changing the position of the optically dense medium located in the rod-shaped housing can be connected to an electromagnetic, hydraulic, pneumatic, but also a manual manual drive. The basic principle is to miniaturize the camera head so that it essentially takes up dimensions that correspond to those of conventional dental instruments, for example an angle mirror, so that all potentially critical points in a patient's mouth can be viewed and thus diagnosed in a simple manner ,

Although the older teaching according to DE 100 49 835 AI represents a significant improvement in the state of the art at the time of registration, an actuating device for triggering a change in focus is still required, which, if it is an external slide, leads to sealing problems within the Housing leads or requires an operation in the case of a separate button.

It is therefore an object of the present invention to provide a further developed miniaturized camera with a photosensitive CCD matrix arranged in a rod or tubular housing and an integrated lighting device, in particular for use in a dental or dermatological diagnostic instrument, which enables a considerably simplified operation and which allows very different objects to be detected in a correspondingly resolved manner, in order in this way to improve the acceptance of the use of such a camera by the attending physician.

The object of the invention is achieved by the combination of features according to the teaching of patent claim 1, the subclaims comprising at least expedient refinements and developments.

Accordingly, the basic idea of the invention is to start from a miniaturized camera known per se, preferably for use in the dental field, the required for object illumination Light is coaxially coupled into the lens beam path. This coaxial illumination reduces the problem of unwanted reflections on the object to be viewed. This prevents an overexposure due to reflection phenomena that certain pathological changes, for example on a tooth or microcracks present there, are not recognized or only insufficiently, so that a diagnosis is impossible.

Furthermore, according to the invention, the objective or a lens of the objective and / or the CCD matrix is arranged as an image sensor on an actuator or connected to it to obtain a linear displacement along the beam path.

Camera electronics, which are preferably integrated into the camera housing, carry out a continuous evaluation of high-frequency signal components of the image sensor, these high-frequency signal components determined leading to a control device for the actuator. The control device then specifies the linear displacement via the actuator in such a way that a maximum high-frequency signal component in the recorded image is obtained or restored.

The solution described above enables quasi-passive autofocus to be carried out by evaluating the high-frequency image components. The focus position found then generally corresponds to the maximum of the high-frequency image components. With the help of the continuous monitoring of these high-frequency image components, it is ensured that if the deviation from the maximum value is defined, a new focus search and setting can begin and be carried out automatically without the user having to trigger any functions or having to actuate mechanical elements. The focus setting is implemented via an internal change in position of the image sensor or a lens group in the optical system, it being possible preferably to use a piezo actuator.

The auto focus works in conjunction with an electrically adjustable aperture or aperture. The main function of this aperture is the regulation of the illuminance with the aim of producing a noise-free image.

For example, an iris diaphragm or a mechanical interchangeable diaphragm with several openings is used as the adjustable diaphragm. The mechanical interchangeable diaphragm can bring different diaphragm openings into the beam path by moving, twisting or pivoting, in order to set the desired illuminance in this way.

In a further development of the invention, for the purpose of larger linear displacement movements, it is possible to use a stepping or moving coil motor or a similar linear drive as the actuator. In the case of an actuator combination consisting of a stepping or moving coil motor for rough positioning over larger adjustment ranges, it is possible to provide an additional piezo actuator for fine positioning.

In this case, the CCD matrix can preferably be arranged directly on the piezo actuator, with the optically sensitive surface perpendicular to the direction of movement thereof.

According to the invention, the camera electronics have a differential measuring device which determines the respective deviation value from a maximum value of the high-frequency signal components in order to then actuate the control device for the actuator.

The control device for the actuator is activated when a predetermined deviation value is reached or exceeded, the size of the deviation value itself being definable depending on the application.

In order to implement the proposed coaxial lighting, a beam splitter arrangement is located in the camera housing, a group of internal light sources, in particular white light-emitting diodes, being provided adjacent to the beam splitter arrangement, ie, interacting with the latter. Furthermore, there is the possibility that a fiber optic ends on the beam splitter arrangement on the light entry side, which opens into a coupling point at the handpiece end of the camera housing. The coupling point is used for connection to an external light source, in particular a cold light source. Depending on the lighting task and local lighting conditions, the internal and / or external light source can then be switched on or on.

In order to dissipate the heat generated during operation of the internal light sources, it is proposed to mount the internal radiation sources on a heat-conducting carrier of a large area, with part of the carrier extending into the end of the rod-shaped housing that is remote from the head in order to remove the thermal energy from the CCD. Keep the matrix away.

In summary, the present invention assumes a combination of a coaxial illumination known per se with a special autofocus control, in particular to prevent crossfading of reflective examination objects. By continuously evaluating the high-frequency signal components at the output of the image sensor by means of camera electronics, an optimum can be found for the respective image without the user having to carry out or have to trigger manual setting operations.

Due to the additional possibility of influencing or selecting the aperture and controlling the intensity of the internal and / or external radiation sources, high-resolution sensors can be used, which are advantageous in terms of an optimized diagnosis.

It is possible to combine the lighting solution disclosed in the earlier application DE 100 49 835 AI with the coaxial lighting described here. With such a combination solution, if unwanted reflections occur, the immediate lighting according to DE 100 49 835 AI is switched off or its intensity is reduced and at the same time the coaxial lighting is put into operation or its intensity is increased. In this development of the invention, the optical plate therefore not only has an optionally adjustable aperture, but rather larger illumination openings grouped around the aperture. Below the illumination openings, light-emitting diodes are preferably attached as radiation sources, here again preferably white-light diodes. A coating of the optical plate prevents undesirable direct coupling of radiation from the light-emitting diodes into the optics.

In a further embodiment of the invention, the arrangement of an optical plate with an aperture, lens and CCD matrix does not extend along the longitudinal axis of the rod-shaped housing, but is located directly in the head at a distance transversely to the longitudinal direction. In this case, the photosensitive CCD matrix is located on a tongue-like carrier strip, which can be pivoted into a first and second position with the aid of a piezo actuator. The stop positions represent a long-range or near-range image, the respective position being selected on the basis of the size of the high-frequency signal components and the actuating actuator being subjected to a corresponding activation by means of the control device.

Reference is made to the following exemplary embodiment and the figure.

In the embodiment of the invention shown in the figure, a focus adjustment is effected by changing the distance between the input aperture 6 or the lens 4 located on a cover glass 5 and the CCD sensor 3. A piezoelectric bender 1 is located on a pedestal 2 to generate the desired relative movement.

When an electrical voltage is applied, the piezo bender 1 executes a movement which leads to the desired change in distance. The movement is represented as pivoting around the fixed connection point between the bearing block 2 and the piezo bender 1. In the embodiment shown, the bearing block 2 extends over almost the entire longitudinal extent of the arrangement, a light passage opening 7 being provided at the end on the right-hand side according to the figure.

Lens 4, cover glass 5 and aperture 6 are connected, for example, to a housing part (not shown) or embedded in a housing recess.

REFERENCE NUMBERS

1 piezo bender

2 bearing block

3 CCD matrix or CCD sensor 4 lens

5 coverslip

6 aperture

7 Opening in the area of the pedestal 2

Claims

claims 1. Miniaturized camera with a photosensitive CCD matrix arranged in a rod-shaped or tubular housing and an integrated lighting device, in particular for use in a dental or dermatological diagnostic instrument, a recess being provided in the head end of the rod-shaped housing, into which an optical plate with an aperture is inserted, a lens is provided on the light entry side behind the aperture and the CCD matrix is arranged at a variable focal distance from the lens, with camera electronics continuously evaluating high-frequency signal components of the image sensor, characterized in that the light required for object illumination is coaxially coupled into the lens beam path via a beam splitter arrangement located in the camera housing, the lens and / or the CCD matrix is arranged as an image sensor on an actuator or with it to obtain a linear displacement g is connected essentially along the beam path, and that a control device is provided for the actuator, the control device specifying the linear displacement in such a way that a maximum high-frequency signal component is obtained or restored. 2. Miniaturized camera according to claim 1, characterized in that the size of the aperture opening can be changed, the aperture size being determined and predetermined by means of the camera electronics in order to obtain a noise-free image. 3. Miniaturized camera according to claim 2, characterized by an iris or a mechanical interchangeable aperture with a plurality of openings of different diameters. 4. Miniaturized camera according to one of the preceding claims, characterized by a piezoelectric actuator. 5. Miniaturized camera according to one of the preceding claims, characterized in that a stepping or moving coil motor is used as an actuator for larger linear displacement movements. 6. Miniaturized camera according to one of the preceding claims, characterized by an actuator combination of a stepping or moving coil motor for rough positioning over larger adjustment paths and a piezo actuator for fine positioning. 7. Miniaturized camera according to claim 6, characterized in that the CCD matrix is arranged directly on the piezo actuator with the optically sensitive surface perpendicular to the direction of movement thereof. 8. Miniaturized camera according to one of the preceding claims, characterized in that the camera electronics comprise a differential measuring device which determines a deviation value from a maximum value of the high-frequency signal components of the image sensor in order to subsequently activate the control device for the actuator. 9. Miniaturized camera according to claim 8, characterized in that the control device is activated when a predetermined deviation value is reached or exceeded. 10. Miniaturized camera according to one of the preceding claims, characterized in that an optically denser medium can be introduced, in particular pivoted, to change the focus in the distance between the lens and the CCD matrix. 11. Miniaturized camera according to one of the preceding claims, characterized in that a naked chip or a sensor in TAPE design is used as the CCD matrix to reduce the installation space. 12. Miniaturized camera according to one of the preceding claims, characterized in that a beam splitter arrangement for coaxial illumination is located in the camera housing. 13. Miniaturized camera according to claim 12, characterized in that the beam splitter arrangement is adjacent to a group of internal light sources, in particular white light-emitting diodes. 14. Miniaturized camera according to claim 12 or 13, characterized in that a fiber optic ends at the beam splitter arrangement, which ends at the handpiece-side end of the camera housing in a coupling point in order to emit radiation from one, including external ones. Light source, especially cold light source to supply. 15. Miniaturized camera according to claim 12 to 14, characterized in that, depending on the observation task and local lighting conditions, the internal and / or external light sources can be switched over or switched on. 16. Miniaturized camera according to one of claims 13 to 15, characterized in that the light-emitting diodes are connected to a controllable constant current source, the luminosity being adjustable as a function of the ambient light conditions or the type of object. 17. Miniaturized camera according to one of claims 13 to 16, characterized in that the internal radiation sources are fastened on a heat-conducting carrier of large area, a part of the carrier extending into the end of the rod-shaped housing of the camera remote from the head.