WO2006037772A1

WO2006037772A1 - Endoscopic camera head

Info

Publication number: WO2006037772A1
Application number: PCT/EP2005/054974
Authority: WO
Inventors: Alain Verdier
Original assignee: Thales
Priority date: 2004-10-08
Filing date: 2005-10-03
Publication date: 2006-04-13
Also published as: FR2876267B1; FR2876267A1

Abstract

The invention concerns an endoscopic camera head comprising a photodetection part (110) and an objective (120) with non mobile parts and at least one electrically tunable liquid lens (122). Preferably, it is integrated in a monolithic housing.

Description

ENDOSCOPIC CAMERA HEAD

The present invention relates to an endoscopic camera head, applicable in particular to endoscopes used in the medical field, in particular for carrying out surgical or therapeutic operations. An endoscope is an optical device that allows observations to be made in confined areas, typically inside a cavity. In its most general form, it comprises a tube fitted with an optic and a light source which provides the lighting necessary for carrying out the observation. The distal end of the tube is inserted into the cavity to make the observation. An imaging device placed at the proximal end of the tube allows an operator to see the interior of the cavity.

In the invention, we are more particularly interested in endoscopes which use as imaging device a camera making it possible to view the image of the scene observed, on video monitors, or to record it. A camera comprises an endoscopic camera head, mounted on the proximal end of the endoscope and a CT signal processing device which receives the signals delivered by the camera head, and which outputs electronic signals sent to one or more display or image recording devices. According to the state of the art, and as shown diagrammatically in FIG. 1, an endoscopic camera head 1 mainly comprises an imaging part 10 and a coupler 20 comprising a lens 21. The imaging part comprises a photodetection device 1 1 and a proximity signal processing device 12, which outputs the electronic signals to an external display and / or recording device 3. The objective allows image recovery and focusing on the photodetection device 1 1 of the camera head.

The photodetection device 1 1 usually comprises at least one color sensor. It can include three, one for red, one for green and one for blue, associated with a separating prism.

The camera head can be equipped with simplified adjustment keys (not shown), for example for gain adjustment or white balance or any other function. An external device control and automatic configuration of the camera head can be provided, which allows the buttons on the camera head to be automatically configured using pre-programmed menus and options, depending on the context of use. Such devices are known which make it possible to adjust a whole panel of parameters as a function of the changing environment of the endoscope. In particular, such a device is described in the French patent entitled "Digital camera and associated digital control method" and published under the number 2 787 275. In practice, the CT processing device illustrated in FIG. 1 advantageously implements such features.

A usual function of the lens is to allow the focusing of the image in the capture plane of the photodetector of the camera head.

Indeed, in operating mode, for example during a surgical operation, the surgeon or an assistant is brought regularly to move the endoscope, and must therefore each time change the focus of the image. In particular, the working area in which the distal end of the endoscope is located as well as the other surgical instruments is a very small area, with a volume of a few cubic centimeters. The surgeon has to frequently vary the position of the endoscope to have a good perception of the operating field. By bringing the distal end of the endoscope closer to the working area, it will have a very good definition of the details and a high precision of the operative gesture, while by moving it away, it will have a wider field necessary for the repositioning of the instruments or the location of organs. Each time, the focus must be redone.

For these purposes, the objective usually comprises an optical combination, typically 3 to 5 lenses, with moving parts, the displacement of which enables the image captured by the photodetection device to be brought into focus. These moving parts are designed to be moved along the optical axis XX ′ of the endoscope, by an external actuator, typically a moving ring 22, mounted around the objective, and the rotation of which causes the axial movement of the parts lens mobiles. It is also possible to have an actuator of the translation type.

Mechanical means are further provided for securely anchoring the camera head to the endoscope. For medical applications, the different parts of the endoscope are subjected to severe sterilization treatments, including soaking in antiseptic solutions, and / or autoclave treatments, that is to say at high temperature. According to the state of the art, an endoscopic camera head 1 is thus usually presented in two separate parts: the imaging part 10 comprising the devices 1 1 and 12 for photodetection and associated signal processing, and an optocoupler part. Mechanical 20. According to the state of the art, this coupler 20 comprises the objective 21 with movable parts, the axial movement of which is actuated by the movable ring 22 disposed on the coupler 20, and ensures the mechanical attachment and the optical centering between the endoscope and the imaging part 10 by suitable means. Currently, we have:

a C-type connector between the imaging part 10 and the coupler 20;

a conventional mechanical system (not shown) enabling the endoscope 2 to be hooked and mechanically centered on the coupler 20.

To seal the various parts of the camera head, O-rings are generally used. As illustrated in FIG. 1, there are thus 3 O-rings: the dynamic joints J1, J2, to ensure the seal between the ring 22 and the coupler 20 during the movement of the ring; the static seal J3 associated with the mount C, which preserves a sealed closed space between the imaging part 10 and the coupler 20. Furthermore, according to the state of the art, in the case where adjustment keys are provided on the camera head, these keys are waterproof type.

Finally, to ensure the transmission of light, the imaging part 10 is provided with a sealed optical window w1 and the coupler 20 is provided with two sealed optical windows w2 and w3. In operation, when the camera head is mounted on the endoscope, mechanical centering makes it possible to align the three windows, along the optical axis XX ', so that the light transmitted by the distal end of the endoscope arrives on the photodetection device 1 1. In practice, it may be necessary to apply a dichroic anti-reflection treatment on the windows w1 to w3. A state-of-the-art endoscopic camera head has various drawbacks.

A first drawback concerns the focusing, which is a delicate operation. In particular, the camera head is often inserted in a sterile cover, which does not facilitate gripping of the focusing ring. It is difficult to do this with one hand. In addition, the direction of rotation to use to focus is not intuitive and there is always trial and error in the search for the best position. Also, the development requires the operator of time and concentration, which is a disadvantage, because it helps to lengthen the operating time and also diverts attention from the operating procedure.

A second drawback relates to the mechanics of moving the moving parts of the objective, the problems of seizure and sealing require continuous maintenance, and therefore downtime of the device to be expected.

Another drawback is linked to decontamination and sterilization treatments. Usually, the regulations in this area provide very specific soaking times, but in practice, these soaking times can be longer. The solutions used are aggressive for organic materials, which leads to rapid wear of the seals. In addition, it is usually preferred not to separate the photodetection part and the coupler part, to reduce handling on these devices and avoid the problem of drying windows w1 and w2 which is not easy, because poor drying is not will see that by the operator, when using the endoscope (fogging). However, it may happen that the C-mount connector is loose. During soaking, there is then a liquid infiltration, which requires an additional drying time. In addition, it is only at the time of use, after reassembly of the camera head on the endoscope, that an operator will notice this defect (fogging on the windows). This leads to additional manipulations and loss of time.

Finally, to support autoclave sterilization treatments, the two photodetection parts 10 and coupler 20 of the camera head are constructed and assembled according to very specific diagrams, so that during from an autoclave treatment, no water vapor or the like disturbs the optical imaging function. It follows an additional cost of the material.

An object of the invention is to provide an endoscopic camera head which does not have all of its drawbacks.

The idea behind the invention is to remove the moving parts of the objective and to use at least one electrically tunable liquid lens, to achieve focusing. The mechanical-optical focusing means are thus replaced by electro-optical means. In this way the external mechanical actuators (rings) are eliminated, and with them, the seals and the associated sealing problems, as well as the specific mechanical problems associated with the moving parts: seizure or malfunction. A much more robust camera head is obtained, with reduced maintenance, which is a definite advantage for devices intended for intensive use in hospitals (reduction in the number of devices and in maintenance costs). The weight of the camera head is also reduced, which is very appreciable for manually manipulated endoscopes.

The objective then comprises an optical combination which performs the image recovery function adapted to the capture plane of the photodetector 11 of the camera head, and at least one electrically tunable liquid lens, placed in front of or behind.

Advantageously, the liquid lens or lenses are integrated into the optical combination, thereby reducing the optical cost of the objective (number of elements), and promoting its miniaturization (bulk).

According to another aspect of the invention, the focusing is done manually, for example, by means of an external button provided for controlling the voltage applied to the lens (or on the lenses), and of an adapted electrical device. provided in the coupler, for example a potentiometer arranged on the camera head, of the waterproof type, associated with a power supply internal to the objective (battery). It is also possible to provide a sealed control key (at least one), associated with a voltage control device provided in the coupler.

An improvement of the invention includes a possibility of automatic focusing, controlled by the signal processing means of the camera head. This automatic focusing can be controlled by a key provided on the camera head, or in a remote mode, on the external device CT, for example an external device allowing the control and the configuration of the camera as described in the French patent. No. 2,787,275 cited above.

According to another aspect of the invention, the camera head is integrated in a monolithic housing. Indeed, the disappearance of the moving parts of the objective and of the associated mechanical means of displacement, makes it possible to envisage the integration of the objective in the same housing as the photodetector. Such integration advantageously makes it possible to remove the mount C and its O-ring J3, and to reduce the number of optical crossings to be provided: a single optical crossing is then necessary, with a single associated dichroic treatment. The optical quality of the transmission, and therefore the sensitivity of the camera at low light levels, are improved. The cost of the camera head is also reduced. In particular, the monolithic integration, and the reduction in the number of interfaces posing sealing problems facilitate and reduce the costs of construction and assembly necessary to make the camera head autoclavable. In fact, according to the state of the art, each of the two parts of the camera head, coupler 20 and imagery 10 had to be designed so as to be each autoclavable.

Thus, as characterized, the invention relates to an endoscopic camera head comprising an imagery and a lens. According to the invention, said objective is with non-moving parts and comprises at least one electrically tunable liquid lens, said lens comprising a conductive liquid capable of controlling the deformation of a surface in contact with this liquid, under the effect of a electric voltage applied to said lens.

According to one aspect of the invention, the camera head comprises means allowing the focusing in manual or automatic mode, in an integrated or remote manner.

According to one aspect of the invention, the camera head is integrated in a monolithic housing.

According to another aspect of the invention, the camera head is produced in miniature form and integrated into the distal end of an endoscope. Other advantages and characteristics of the invention will appear more clearly on reading the description which follows, given by way of indication and without limitation of the invention and with reference to the appended drawings, in which: FIG. 1 already described illustrates an endoscopic system comprising a camera head according to the state of the art;

FIG. 2a illustrates an architecture of a camera head according to a first embodiment of the invention;

FIG. 2b is a variant of FIG. 2a; FIG. 3 illustrates an architecture of a camera head according to a second embodiment of the invention;

FIG. 4 illustrates an endoscope provided with a camera head according to the invention, miniaturized.

A first embodiment of a camera head according to the invention is shown in Figure 2a.

The camera head 100 comprises a photodetection part 110 and a coupler part 130. The photodetection part is similar to that already described in relation to FIG. 1 under the reference 10 and comprises a photodetector 111 and a proximity signal processing device 112 .

The coupler 130 includes a lens 120, which allows the recovery of images and the focusing in a capture plane of the photodetector 111.

The objective 120 has non-moving parts and includes at least one liquid lens 122, allowing images to be focused as a function of a voltage applied to it. In the example illustrated, the objective comprises an optical combination 121, which has non-moving parts, and an electrically tunable lens 122 placed in front, that is to say between the optical combination 121 and the window w3 intended to face the proximal end of the endoscope. This lens then performs a tunable focusing optical function in the objective 121.

It is recalled that an electrically tunable liquid lens is a lens which uses the properties of a conductive liquid to control the deformation of a surface in contact with this liquid, so that the focal distance is thereby modified, and therefore the optical power. More specifically, such a liquid lens has a cone shape containing two transparent liquids which do not mix, a first electrical conductor and a second insulator. In practice, for example, water is used for the first and oil for the second. The lens walls are hydrophobic and contain electrodes through which a control voltage can be applied. The border between the two liquids constitutes a liquid diopter which deforms according to the applied control voltage, under the action of the first conductive liquid. The transition from a convex to a concave surface can be obtained in a fraction of a second. The control voltages are low on the order of a few volts maximum, and the associated control electronics are simple to implement.

The phenomenon is succinctly as follows: in the absence of an electric charge, the first liquid avoids the walls and then forms an arc of a circle, letting the second liquid occupy the space left free by the first liquid. When a control voltage is applied, the electrical charge makes the walls less hydrophobic. The first liquid is then attracted by the electrodes, and sticks to the walls, deforming the diopter, ie the surface between the two liquids. This phenomenon makes it possible to change the refraction of the incident light by the lens, as a function of the applied voltage.

When used in a lens, adjusting this tension allows you to focus until an object in the lens appears sharp.

A proximity electronic device 123 with a battery for example can be provided in the coupler, manually controlled by a waterproof digital button 124, provided on the coupler, to apply a suitable voltage allowing focusing. In a variant shown in Figure 2b, the necessary control voltage is controlled by the signal processing device 1 12 of the photodetector 1 1 1, by a suitable electrical interface 125. In practice we can provide an electrical connection to the interface camera-lens in a sealed area, typically within the area of the J3 seal. In this variant, it is possible to provide for manual focusing, by means of a key. digital which adjusts the control voltage to be applied via the electrical interface 125. It is also possible to provide automatic focusing. The signal processing device 112 then integrates suitable signal processing modules well known to those skilled in the art, for driving the lens.

In such a mode, one can provide an automatic focusing, according to a pulse mode, or continuous. The continuous mode has the effect of perpetually focusing. Such an operation can be inconvenient in operational phases in which instruments move in the field of vision (exchange of instruments ...). It is therefore advantageous to provide a pulse mode of automatic focusing, according to which the focusing is carried out punctually, on pressing a key provided for this purpose on the camera head, or at periodic intervals. The camera head then comprises a set 114 of digital keys, connected to the signal processing device 112. The latter comes to read the state of these keys to actuate one or the other of the modes of focusing provided.

In practice and as shown in FIG. 2a, the tunable lens or lenses 122 can be placed in front of the optical combination as shown in FIG. 2a, or even behind, as shown in FIG. 2b.

Advantageously, the tunable lens or lenses 122 are integrated into the optical combination 121 (not shown), that is to say that they replace other optical elements of this combination. In this way, the optical transmission of the camera head is improved, by reducing the number of optical elements required.

It can also be provided that the signal processing associated with the focusing is carried out by an external device CT for signal processing, advantageously a device allowing the control and the automatic configuration of the camera head. There is then a remote autofocus mode.

According to a preferred embodiment of the invention illustrated in Figure 3, the camera head is made in a monolithic housing, thus eliminating the opto-mechanical coupling usually necessary between the photodetection part and the coupler part. The number of optical elements is reduced since there is only one watertight window w4, intended to face the proximal end of the endoscope 2.

The camera head 200 then comprises, after this window, a lens 220, the photodetector 21 1 and the associated signal processing device 212.

The objective 220 comprises, as described in relation to FIGS. 2a and 2b, an optical combination 221 without moving parts and at least one electrically tunable liquid lens 222. This lens then receives on its contact electrodes 223, a voltage controlled by electronic proximity means, typically integrated in the signal processing device 212. As described in relation to FIGS. 2a and 2b, the liquid lens (s) can be placed in front of or behind the optical combination, or integrated into the optical combination. The modes of manual, automatic and remote focusing, in pulse or continuous are advantageously implemented. For this purpose digital control keys 214 associated with the various operating modes are provided on the camera head. These keys are provided waterproof. All these keys can be provided on the external CT device, in a remote mode. The surgeon who manipulates the endoscope, or an assistant outside the operating field can thus indifferently control each of these different functions, the first using the keys provided on the camera head, and the second, using the remote keys on the external device. CT. Preferably, several tunable liquid lenses are provided, with an associated command remotely controlled, by the CT device, allowing operations of the automatic zoom type, that is to say operations of automatic reduction or enlargement of the images. Preferably, the camera head according to the invention is designed to be autoclavable. In this case, the liquid lens (s) are such that they withstand the high temperature applied in the autoclave treatment (typically 134 ^° C.), both in terms of the liquids used, chosen so as not to degrade irreversibly with the high temperature, that at the level of the optical structure which will be designed to withstand the high pressures due to the expansion of liquids with temperature.

Another aspect of the invention is illustrated in FIG. 4. Current technological development indeed makes it possible to envisage the production of a camera head according to the invention, in miniaturized form, of dimensions such that it can be integrated into endoscope 2, at the distal end d. In such an application, the photodetector will generally comprise a single sensor, and the endoscope will no longer include an eyepiece. A low cost endoscope with integrated camera head is thus advantageously obtained.

The invention which has just been described is particularly suitable for medical applications. It takes into account the normative aspects of the field. In particular, all the electrical devices are in electrically insulated boxes and operate at very low safety voltage. The monolithic aspect and the simplification of the focusing obtained with a camera head according to the invention is also advantageous for industrial type applications.

Claims

1. Endoscopic camera head comprising a photodetection part (110) and a lens (120), characterized in that said objective is with non-moving parts and comprises at least one liquid lens (122) electrically tunable, said lens comprising a conductive liquid able to control the deformation of a surface in contact with this liquid, under the effect of an electric voltage applied to said lens.

2. Endoscopic camera head according to claim 1, characterized in that it comprises a manual adjustment device (123, 124) of the tension applied to said liquid lens, allowing manual focusing of endoscopic images.

3. Endoscopic camera head according to claim 1, comprising a photodetector (111) and an electronic device (112) for processing the signal supplied by said photodetector, characterized in that said electronic device integrates a module for controlling the voltage to be applied to the liquid lens.

4. Endoscopic camera head according to claim 3, associated with an external signal processing device (CT), characterized in that said external device controls the automatic focusing of the images via the associated signal processing device (112) to the photodetector (1 1 1).

5. Endoscopic camera head according to claim 4, characterized in that it comprises a plurality of electrically tunable liquid lenses, and in that said lenses are controlled by said external signal processing device (CT), through the signal processing device (112) of the head, for performing operations of reduction or enlargement of the images.

6. Endoscopic camera head according to claim 4 or 5, characterized in that said processing device (CT) is a device for automatically controlling and configuring the camera head.

7. Endoscopic camera head according to one of claims 3 to 6, characterized in that said focusing is controlled automatically according to a pulse mode.

8. Endoscopic camera head according to claim 3 to 6, characterized in that said focusing is controlled automatically in a continuous mode.

9. Endoscopic camera head according to any one of claims 2 to 8, characterized in that digital keys (1 14, 224) for controlling the focus are provided on the camera head.

10. Endoscopic camera head according to claim 9 in combination with one of claims 4 to 6, characterized in that the digital keys (1 14, 224) for controlling the focus are provided on the external control device .

11. Camera head according to any one of the preceding claims, characterized in that it is integrated in a monolithic housing.

12. Camera head according to any one of the preceding claims, characterized in that it is autoclavable.

13. Miniature camera head according to any one of the preceding claims, intended to be integrated into the distal end (d) of an endoscope.