Patent Description:
A prior art inspection device for parisons is described in publication <CIT>.

That publication describes an inspection system with a detection head equipped with cameras and movable along longitudinal guides in such a way that one row of parisons held in a stationary position is inspected each time the detection head passes.

The parisons are initially carried in a containment device provided with a 12x12 array of seats holding respective parisons which are delivered in rows onto respective carrier slides movable longitudinally in a direction parallel to the detection head.

Once each slide has been brought into the detection area, the slide is stopped and the detection head is triggered and made to move translationally along the respective longitudinal guide.

The Applicant has found that the disadvantage of this type of inspection system is that the detection head has to perform a very high number of passes in order to complete inspection of all the parisons. This brings to the fore relatively stringent production limitations.

Moreover, the long length of time the parisons have to remain inside the inspection device may lead to excessive alteration of the temperature profiles of the parisons, thus adversely affecting the subsequent stages of the production process.

Other parison inspection devices are described in patent documents <CIT> and <CIT>.

The aim of this invention is to provide an inspection device for parisons and an inspection method for parisons, as well as a machine for making parisons comprising the device, which can overcome the above mentioned disadvantages of the prior art.

This aim is achieved by the inspection device for parisons and by the inspection method for parisons as according to one or more of the appended claims.

More specifically, the device comprises at least a first conveying means having, on one side of it (the receiving side), a plurality of seats, arranged in an array configuration, for receiving respective parisons.

It should be noted that in the array of receiving seats, the parisons are arranged according to a plurality of rows and a plurality of columns (the number of parisons in each row being equal to the number of columns). In a possible embodiment, the first conveying means is configured to simultaneously receive the parisons of the plurality of parisons, simultaneously occupying all the seats of the plurality of receiving seats (positioned on that face).

The first conveying means is movable between a first station for receiving the parisons and a second station for releasing the parisons. The first conveying means is movable between the first and second stations along a trajectory having at least one stretch which is transverse, preferably perpendicular, to the longitudinal axis of the parisons on the first conveying means.

Preferably, the plurality of seats is formed on a flat face; thus, the seats in the plurality of seats are coplanar or substantially coplanar. Preferably, the parisons housed in the seats of the plurality of seats are extracted simultaneously directly from the mould.

The device includes at least a first optical detection device. In an example embodiment, the first optical detection unit faces the first conveying means on the parison receiving side of the latter; this is true at least at the transverse, preferably perpendicular, stretch of the trajectory to inspect at least one portion of the parisons which faces the first optical detection unit. In other words, the first optical detection unit is oriented (relative to the first conveying means) in such a way as to see the parison receiving seats on the first conveying means. In an embodiment, the parison receiving seats on the first conveying means include holes and are configured to receive the parisons bottom down in the holes in such a way that the opening of each parison is directed away from the parison receiving seats on the first conveying means to be inspected by the first optical detection unit when the first conveying means passes through the optical path (of the cameras) of the first optical detection unit.

The first optical detection unit and the first conveying means are movable relative to each other. In a possible embodiment, the first optical detection unit is located at a position which is stationary (or movable in the opposite direction) relative to the movement of the first conveying means (the latter movement being along the aforementioned trajectory), to produce a relative movement between the first conveying means and the first optical detection unit.

This allows inspecting all the parisons associated with the array during the passage from the first to the second station.

It should be noted that the expression "optical detection unit" is used to denote a unit that includes all the electronic components necessary for capturing images; for example, the unit includes at least a camera, a lens and an illuminator.

In a possible embodiment, the first optical detection unit comprises at least one camera which is linear and elongate in shape. Preferably, the first optical detection unit is located at a stationary position, at least during detection, and is configured to perform one inspection (take one snapshot) at least in a detection plane lying transversely to the transverse stretch of the trajectory of the first conveying means to inspect one after the other consecutive rows of parisons carried by the first conveying means. This allows the camera to detect consecutive rows of parisons one after the other during the feed movement of the first conveying means. Preferably, the detection plane is parallel to one of the two lines of the parison array when the first conveying means passes the transverse stretch of the trajectory. More preferably, the detection plane is vertical and detection occurs while the first conveying means moves in a horizontal direction, with the parisons arranged in the form of an array lying in a vertical plane.

The inspection device also comprises a second conveying means having, on one side of it, a plurality of respective seats for receiving an array of respective parisons and movable between the second station, where it receives a plurality of parisons from the first conveying means while maintaining the array form, and a third station for unloading the parisons, where the second conveying means is configured to hold the parisons at the ends of the parisons opposite the first conveying means. For example, the first conveying means grips each parison by its bottom end and exposes the mouth of the parison to the first optical detection unit, whilst the second conveying means grips each parison by its mouth and/or neck. The second conveying means is movable between the second and third stations along a trajectory having at least one stretch which is transverse, preferably perpendicular, to the longitudinal axis of the parisons carried by the second conveying means, and the device also comprises a second optical detection unit facing the second conveying means on the side of the latter which receives the parisons at least at the transverse, preferably perpendicular, stretch of the trajectory of the second conveying means to inspect at least one portion of the parisons which faces the second optical detection unit. With these features, it is possible to inspect both ends of the parisons, and thus, ideally, to perform a complete inspection, while the parisons are being transferred.

The second conveying means is preferably configured to perform a rotational movement between the second and the third station, such as to vary the orientation of the parisons carried by the second conveying means. In one embodiment, this movement, which comprises a rotation and/or a rototranslation takes the parisons in the array form from a vertical plane (second station) to a horizontal plane (third station), preferably with the parisons extending from the second conveying means downwards to where the second optical detection unit is located.

The second optical detection unit comprises preferably a plurality of fixed cameras located in an area where the trajectory followed by the second conveying means is parallel to a row of seats of the array of seats, preferably horizontal, with the array oriented in a horizontal plane in such a way that each camera operates on a respective main line of the array of seats of the second conveying means.

Preferably, the cameras of the second detection unit are arranged in a mutually offset configuration along the trajectory of the second conveying means.

Preferably, also, each camera of the second detection unit is positioned and shaped to detect the bottom and/or the main body, in succession, of the parisons of one row of parisons of the array of parisons carried by the second conveying means.

In one embodiment, the second detection unit comprises pairs of fixed cameras, each pair being associated with a respective row of parisons carried by the second conveying means to inspect the bottom and/or opposite sides of the main body of the parisons.

In one embodiment, the first conveying means is positioned and configured in such a way as to pick up a plurality of parisons arranged in array form directly from a mould in which the parisons are made. This allows integrating the inspection device into a machine of known type for making parisons using normal procedures for extracting and transferring the parisons from the mould.

At the third station, the device also comprises a sorting means provided with an array of seats for receiving parisons and compatible with the array of seats of the second conveying means in order to receive the parisons from the second conveying means, each seat being equipped with a respective mechanism for releasing or retaining the parison in the seat; the sorting means being movable between a first position, above a container for collecting conforming parisons, and a second position, above a container for defective parisons; the device further comprising a control unit connected to the optical detection units and driving the releasing/retaining mechanism in order to allow each parison to be released into one of the containers, as required.

The method comprises the steps of gripping a plurality of parisons by their first ends in a pickup station using a first conveying means on which the parisons are arranged in the form of an array; transferring the parisons carried by the first conveying means to a second station for releasing the parisons, following a trajectory having at least one stretch which is transverse, preferably perpendicular, to the longitudinal axis of the parisons carried by the first conveying means. The method comprises at least a first step of subjecting the parisons to optical inspection by means of a first fixed optical detection unit during the step of transferring the parisons from the first to the second station while the parisons are in motion, wherein the first optical detection unit faces the first conveying means on the side of the latter which receives the parisons at least at the transverse, preferably perpendicular, stretch of the trajectory to inspect at least one portion of the parisons which faces the first optical detection unit.

The first step of subjecting the parisons to optical inspection is performed by means of at least a first optical detection unit (which, in a possible embodiment, includes a linear camera). The first optical detection unit is preferably elongate in shape. In one embodiment, the first optical detection unit is located at a stationary position, at least during detection, and is configured to perform one inspection at least in a detection plane lying transversely, preferably perpendicularly, to the transverse/perpendicular stretch of the trajectory of the first conveying means to inspect one after the other consecutive rows of parisons carried by the first conveying means. This allows the camera to detect consecutive rows of parisons one after the other during the feed movement of the first conveying means. Preferably, the detection plane is parallel to one of the two lines of the parison array when the first conveying means passes the transverse stretch of the trajectory. More preferably, the detection plane is vertical and detection occurs while the first conveying means moves in a horizontal direction, with the parisons arranged in the form of an array lying in a vertical plane.

The method also comprises a step of transferring the parisons from the first conveying means to a second conveying means at the second station, where the second conveying means has, on one side of it, a plurality of respective seats for receiving an array of respective parisons and movable between the second station, where it faces the first conveying means to receive the plurality of parisons from the first conveying means while maintaining the array form, and a third station for unloading the parisons, where the second conveying means holds the parisons at the ends of the parisons opposite the first conveying means. For example, the first conveying means grips each parison by its bottom end and exposes the mouth of the parison to the first optical detection unit, whilst the second conveying means grips each parison by its mouth and/or neck. The second conveying means is movable between the second and third stations along a trajectory having at least one stretch which is transverse, preferably perpendicular, to the longitudinal axis of the parisons carried by the second conveying means. The method also comprises a second step of optically inspecting the parisons by means of a second optical detection unit facing the second conveying means on the side of the latter which receives the parisons at least at the transverse, preferably perpendicular, stretch of the trajectory of the second conveying means to inspect at least one portion of the parisons which faces the second optical detection unit.

In an embodiment, the second optical detection unit comprises a plurality of fixed cameras located in an area where the trajectory followed by the second conveying means is parallel to a row of seats of the array of seats, and the second inspection step is performed during the movement of the second conveying means to inspect each line of parisons with a respective camera of the plurality of cameras, each line of parisons being aligned with the direction of movement of the second conveying means during detection.

Further, in an embodiment, the step of gripping the parisons in the first pickup station by means of the first conveying means is accomplished by picking up a plurality of parisons arranged in array form directly from a mould in which the parisons are made. In one embodiment, the parisons on the first conveying means are oriented in such a way that the mouth of each parison faces the first detection unit. In a different embodiment, the parisons on the first conveying means are oriented in such a way that the bottom of each parison faces the first detection unit.

The method also comprises the possibility of inspecting the parisons on the first conveying means during a return step in which the conveying means returns from the second station to the first station. In effect, the first conveying means is configured to receive simultaneously a number of parisons which is a multiple (for example a quadruple) of the number of parisons picked up in the first station (for example from the mould) or released to the second conveying means in the second station. In this configuration, the parisons not released in the second station undergo at least one further return and-forward movement cycle on the first conveying means.

These and other features of the invention will become more apparent from the following description of a preferred embodiment of it, illustrated purely by way of non-limiting example in the accompanying drawings which schematically illustrate an inspection device for parisons according to the invention in a sequence of operating steps: More specifically, in the accompanying drawings:.

In the accompanying drawings, the numeral <NUM> denotes in its entirety a machine for making parisons <NUM>, or parison forming machine <NUM>. In one embodiment, the machine <NUM> is an injection moulding machine. This machine is preferably a reciprocating mould machine, that is to say, it simultaneously moulds a plurality of parisons, cyclically, at predetermined intervals (necessary for the machine to be reloaded after each moulding cycle).

In a different embodiment, the machine <NUM> might be a compression moulding machine.

The machine <NUM> has a frame (that is, a supporting structure), not illustrated in the drawings.

The machine <NUM> comprises at least one mould <NUM> for forming the parisons, and downstream of the mould <NUM>, an inspection device <NUM> according to one or more of the aspects of this description, for the parisons <NUM>.

In at least one embodiment, the inspection device <NUM> is (at least partly) integrated in the machine <NUM>.

The mould <NUM> includes a first mould head (or half-mould) 2A and a second mould head (or half-mould) 2B.

The mould <NUM> is configured to make a plurality of parisons <NUM> simultaneously, arranged in array form.

In the context of this description, the term "array" is used to denote an arrangement in rectangular series, that is to say, an arrangement of "m x n" elements, where "m" and "n" are integers greater than or equal to <NUM> (for example, if m=<NUM> and n=<NUM>, there is an array with a single row of <NUM> elements).

In a possible but non-limiting embodiment according to what is illustrated in the drawings, the array distribution is 12x12 or 12x4, according to the component selected, as described below.

As shown in the drawings, the mould <NUM> is configured to simultaneously make an array of 12x4 parisons <NUM>, that is to say, four rows of twelve parisons each.

The mould <NUM> comprises two half moulds 2A, 2B which, once moved apart, allow the 12x4 parisons <NUM> to be withdrawn by a pickup means, which is defined by a first conveying means <NUM> of the inspection device <NUM> and which is placed between the two half moulds in such a way as to withdraw the array of parisons <NUM> just made.

The first conveying means <NUM> has a tray- or panel-like configuration and has, on one side of it, a 12x12 array of seats <NUM>, each seat <NUM> being designed to receive a respective parison <NUM> from the mould <NUM>.

The first conveying means <NUM> is movable between a first station S1 for receiving the parisons <NUM> from the mould <NUM>, and a second station S2 for releasing the parisons <NUM>, and is movable between the first and second stations S1, S2 along a trajectory having at least one stretch which is transverse, preferably perpendicular, to the longitudinal axis of the parisons <NUM> on the first conveying means <NUM>. By "longitudinal axis" of the parisons <NUM> is meant the axis around which each parison <NUM> extends and which coincides with the axis of each seat <NUM> and with the direction along which each parison <NUM> is inserted into the respective seat.

Also, in the embodiment illustrated, the trajectory of the first conveying means <NUM> is schematically represented as rectilinear in the entire stretch between the two stations S1, S2.

The first conveying means <NUM> is configured (operated) to receive and store the parisons <NUM> to allow them to cool down in optimum manner. More in detail, the number of seats <NUM> of the first conveying means <NUM> is equal to three times the number of parisons <NUM> released by the mould <NUM>. Thus, the operating logic of the machine <NUM> is such as to progressively store on the first conveying means <NUM>, successive groups of 12x4 parisons received from the mould <NUM> and to release to the second station S2 at every forward cycle only the first of the three groups of 12x4 parisons. In other words, at each forward and return cycle, the first conveying means receives a new group of parisons <NUM> from the mould <NUM> and releases the "older" group. The inspection device comprises a first optical detection unit <NUM>; the unit defines a respective field of vision (that is, an optical path). The first optical detection unit <NUM> is oriented in such a way that its field of vision intercepts the first conveying means <NUM> at least at one of the positions adopted by the first conveying means <NUM> as it moves from the first station S1 to the second station S2 and/or vice versa.

The first optical detection unit <NUM> and the first conveying means <NUM> are movable relative to each other to allow the first optical detection unit <NUM> to see in succession the parisons carried by the first conveying means <NUM> in rows (or, more generally, groups) which are offset, that is, spaced, along the direction of movement of the first conveying means <NUM> between the stations S1 and S2.

In one embodiment, the first optical detection unit <NUM> is stationary, whilst the first conveying means <NUM> is movable.

The position of the first optical detection unit <NUM> is selected in such a way that the first optical detection unit <NUM> faces the first conveying means <NUM> on the side of the latter which receives the parisons <NUM> at least when the first conveying means <NUM> travels the transverse, preferably perpendicular, stretch of the trajectory between the two stations S1, S2, to inspect at least one portion of the parisons <NUM> which faces the first optical detection unit <NUM>.

In an example embodiment, the first optical detection unit <NUM> is connected to the frame of the machine <NUM>; for example, it might be connected to an upright of the frame, positioned vertically (that is, positioned along a direction transverse to a direction of movement of the first conveying means <NUM> between the two stations S1, S2.

In a possible embodiment, the first optical detection unit <NUM> comprises at least one linear camera 6a. Preferably, the first optical detection unit <NUM> is elongate in shape, located at a stationary position, at least during detection of the parisons <NUM>, and configured to perform one inspection at least in a detection plane lying transversely to the transverse stretch of the trajectory of the first conveying means <NUM> to inspect one after the other consecutive rows of parisons <NUM> carried by the first conveying means <NUM>. Preferably, the detection plane is parallel to one of the two lines of the parison array when the first conveying means passes the transverse stretch of the trajectory. More preferably, the detection plane is vertical.

(identified by the detection cone associated with the camera in the accompanying drawings) and detection occurs while the first conveying means <NUM> moves in a horizontal direction with the parisons <NUM> arranged in the form of an array lying in a vertical plane.

Downstream of the second station S2, the inspection device <NUM> also comprises a second conveying means <NUM>. The second conveying means <NUM> has, on one side of it, a plurality of respective seats (not shown in the accompanying drawings), arranged in an array configuration, for receiving respective parisons <NUM>. The second conveying means <NUM> is movable between the second station S2, where it receives a plurality of parisons <NUM> from the first conveying means <NUM> while maintaining the array form, and a third station S3 for unloading the parisons <NUM>. The second conveying means <NUM> is configured to hold the parisons <NUM> at the ends of the parisons opposite the first conveying means <NUM>. For example, the first conveying means <NUM> grips each parison <NUM> by its bottom end and exposes the mouth of the parison to the first optical detection unit <NUM>, whilst the second conveying means <NUM> grips each parison <NUM> by its mouth and/or neck.

The second conveying means also has a tray- or panel-like configuration and is movable between the second and third stations S2, S3 along a trajectory having at least one stretch which is transverse, preferably perpendicular, to the longitudinal axis of the parisons <NUM> carried by the second conveying means <NUM>.

More specifically, the second conveying means <NUM> is preferably configured to perform a rotational movement between the second and the third station S2, S3, such as to vary the orientation of the parisons <NUM> carried by the second conveying means <NUM>. In one embodiment, this movement, which comprises a rotation and/or a rototranslation takes the parisons in the array form from a vertical plane (second station S2) to a horizontal plane, preferably with the parisons <NUM> extending downwards from the second conveying means <NUM>.

The device <NUM> further comprises a second optical detection unit <NUM>.

The second optical detection <NUM> unit faces the second conveying means <NUM> on the side of the latter which receives the parisons <NUM> at least at the transverse, preferably perpendicular, stretch of the trajectory of the second conveying means <NUM> to inspect at least one portion of the parisons <NUM> which faces the second optical detection unit <NUM>. More specifically, in the embodiment illustrated, the second optical detection unit <NUM> is located underneath the second conveying means <NUM> when the latter is positioned horizontally.

The second optical detection unit <NUM> comprises one or more inspection units. In one embodiment, the second optical detection unit <NUM> comprises a plurality of inspection units. It should be noted that, preferably, the number of inspection units of the second optical detection unit <NUM> is equal to the number of rows along which the parisons are arranged in the second conveying means <NUM>. In the example illustrated, the parisons on the second conveying means <NUM> are arranged in four rows and the second optical detection unit <NUM> has four inspection units; this number may vary from <NUM> to <NUM> or more, depending on the embodiment.

The second optical detection unit <NUM> comprises a plurality of cameras <NUM>; the cameras <NUM> are configured to see (inspect) a lateral portion and a bottom portion of the parisons.

In one embodiment, each inspection unit of the second optical detection unit <NUM> comprises a respective plurality of cameras <NUM>, as follows: one (or more) bottom cameras (oriented towards the second conveying means <NUM> to see the bottom of the parisons carried thereon); and one or more (preferably at least two, one of which on the right and the other on the left) lateral cameras oriented on opposite sides towards a lateral surface of the parisons which are operatively interposed between the lateral cameras).

The second optical detection unit <NUM> and the second conveying means <NUM> are movable relative to each other to allow the parisons (held by the second conveying means <NUM>) to pass through optical detection unit <NUM>.

In one embodiment, the second optical detection unit <NUM> is stationary, whilst the second conveying means <NUM> is movable. Thus, in this embodiment, the cameras <NUM> are fixed (that is, stationary) and located in an area where the trajectory followed by the second conveying means <NUM> is parallel to a row of seats of the array of seats, preferably horizontal, with the array oriented in a horizontal plane in such a way that each camera <NUM> operates on a respective main line of the array of seats of the second conveying means <NUM>.

Preferably, the cameras <NUM> of the second detection unit <NUM> are arranged in a mutually offset configuration along the trajectory of the second conveying means <NUM>.

Preferably, also, each camera <NUM> of the second detection unit is positioned and shaped to detect the bottom and/or the main body, in succession, of the parisons <NUM> of one row of the array of parisons <NUM> carried by the second conveying means <NUM>.

In the embodiment illustrated, the second detection unit <NUM> comprises pairs of fixed cameras, each pair being associated with a respective row of parisons carried by the second conveying means to inspect the bottom and/or opposite sides of the main body of the parisons. Each pair of cameras <NUM> is mounted on opposite sides of a respective U-shaped mounting element in such a way as to detect laterally opposite portions of a single parison <NUM>.

It should be noted that the second conveying means <NUM> has a plurality of gripping elements for holding the parisons <NUM>. These gripping elements are preferably arranged in two or more parallel rows. In a possible embodiment, the second conveying means <NUM> comprises a plurality of tracks, where all the gripping elements in one row are mounted on one corresponding track. In a possible embodiment, the tracks of the second conveying means <NUM> are movable transversely to a direction defined by the tracks themselves. This allows the rows of parisons held by the second conveying means <NUM> to be spaced as required.

Operatively, when the second conveying means <NUM> interacts with the first conveying means <NUM>, the row spacing is determined by the row spacing of the parisons on the first conveying means <NUM>; when the second conveying means <NUM> interacts with the second optical detection unit <NUM>, on the other hand, the parison row spacing, on the second conveying means <NUM>, is (or may be) determined by (or set as a function of) an overall dimension of the inspection units of the second optical detection unit <NUM>.

In a possible embodiment, the device includes a third station S3 located (immediately) downstream of the second detection unit <NUM>.

In a possible embodiment, the device <NUM> comprises a sorting means <NUM>. Preferably, the sorting means <NUM> can be positioned at the station S3.

In one embodiment, the sorting means <NUM> is provided with an array of respective seats <NUM> for receiving parisons <NUM>. Preferably, the array defined by the sorting means <NUM> is compatible with the array of seats of the second conveying means <NUM> in order to receive the parisons <NUM> from the second conveying means <NUM>. The sorting means <NUM> has a selective mechanism for releasing/retaining the parisons <NUM> in the respective seats <NUM>. In one embodiment, each seat <NUM> of the sorting means <NUM> is equipped with a respective element for releasing/retaining the parison <NUM> in the seat <NUM>.

The sorting means <NUM> is movable between a first position, above a container <NUM> for collecting conforming parisons, and a second position, above a container <NUM> for defective parisons. In one embodiment, the sorting means <NUM> is operatively positionable at a third position where it faces the second conveying means <NUM> to receive the parisons therefrom; the third position may coincide with the first position or with the second position, or it may be intermediate between the two (preferably the three positions are aligned along a direction transverse to the direction of movement of the second conveying means <NUM> from the first to the second station). In a possible embodiment, the seats <NUM> of the sorting means <NUM> include through holes (to be able to receive the parisons from above and release them from below without having to turn the sorting means upside down).

Claim 1:
An inspection device for parisons comprising at least a first conveying means (<NUM>) having, on one side of it, a plurality of seats (<NUM>) for receiving an array of respective parisons (<NUM>), wherein the first conveying means (<NUM>) is movable between a first station (S1) for receiving the parisons (<NUM>) and a second station (S2) for releasing the parisons (<NUM>) and wherein the first conveying means (<NUM>) is movable between the first and second stations (S1, S2) along a trajectory having at least one stretch which is transverse to the longitudinal axis of the parisons (<NUM>) on the first conveying means (<NUM>), wherein the device (<NUM>) comprises a first optical detection unit (<NUM>) located at a fixed position and facing the first conveying means (<NUM>) on the side of the latter which receives the parisons (<NUM>) at least at the transverse stretch of the trajectory to inspect at least one portion of the parisons (<NUM>) which faces the first optical detection unit (<NUM>), characterized in that it further comprises a second conveying means (<NUM>) having, on one side of it, a plurality of respective seats for receiving an array of respective parisons (<NUM>) and movable between the second station (S2), where it receives a plurality of parisons (<NUM>) from the first conveying means (<NUM>) and a third station (S3) for unloading the parisons (<NUM>), where the second conveying means (<NUM>) is configured to hold the parisons (<NUM>) at the ends of the parisons (<NUM>) opposite the portions of the parisons (<NUM>) gripped by the first conveying means (<NUM>), the second conveying means (<NUM>) being movable between the second and third stations (S2, S3) along a trajectory having at least one stretch which is transverse to the longitudinal axis of the parisons (<NUM>) on the second conveying means (<NUM>), the device (<NUM>) further comprising a second optical detection unit (<NUM>) facing the second conveying means (<NUM>) on the side of the latter which receives the parisons (<NUM>) at least at the transverse stretch of the trajectory of the second conveying means (<NUM>) to inspect at least one portion of the parisons (<NUM>) which faces the second optical detection unit (<NUM>).